* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Guyot Science 2005
Survey
Document related concepts
Marine debris wikipedia , lookup
Blue carbon wikipedia , lookup
Anoxic event wikipedia , lookup
Future sea level wikipedia , lookup
Arctic Ocean wikipedia , lookup
Indian Ocean wikipedia , lookup
Indian Ocean Research Group wikipedia , lookup
Marine habitats wikipedia , lookup
Marine biology wikipedia , lookup
Marine pollution wikipedia , lookup
Ocean acidification wikipedia , lookup
Physical oceanography wikipedia , lookup
Effects of global warming on oceans wikipedia , lookup
History of research ships wikipedia , lookup
Global Energy and Water Cycle Experiment wikipedia , lookup
Ecosystem of the North Pacific Subtropical Gyre wikipedia , lookup
Transcript
Guyot Science 2005 Department of Geosciences, Princeton University 1 2 Guyot Science 2005 A Summary of the Research Progress and Accomplishments Made by the Faculty Members of the Department of Geosciences During the Year 2005 Last year, January–December 2005, was a transitional year for a number of faculty members of the Princeton Department of Geosciences. In June Bob Phinney transferred to emeritus status, following a distinguished career as a professor and former department chair. We are pleased that Bob has agreed to remain at Princeton, and plans to continue to teach his popular freshman seminar, Active Geological Processes, which has long been an attraction for prospective departmental majors. In July Satish Myneni was promoted to the rank of associate professor with continuing tenure. Two professors were named to endowed chairs: George Philander is now the Knox Taylor Professor of Geosciences and Bess Ward is now the William J. Sinclair Professor of Geosciences. In April, George was inducted into the National Academy of Sciences, raising the departmental membership to four. Nadine McQuarrie, a structural geologist who studies mountain building and other active tectonic processes, completed her first highly successful year as our newest assistant professor. Next year, we will be joined by two new assistant professors, Adam Maloof, a geologist who applies paleomagnetism and other tools to the study of the ancient earth, and Frederik Simons, a geophysicist who is developing a variety of innovative new tools to study the structure and evolution of planetary lithospheres as well as pioneering in the development of a freely drifting submersible vehicle to increase teleseismic coverage in the world’s oceans. In December, François Morel was awarded the Maurice Ewing Medal of the American Geophysical Union and the U.S. Navy, “for his leadership in the revolution in low-temperature aqueous geochemistry that has resulted in a new field of studies at the interface between marine chemistry and biology.” Finally, Allan Rubin was inducted as a Fellow of the American Geophysical Union; this is a prestigious honor restricted to no more than 0.1 percent of the membership each year. More than half of the faculty members in the Department of Geosciences are now Fellows of the AGU. The recent research accomplishments of each member of the geosciences faculty are described in the individual reports that follow. A list of faculty publications during the past two years, 2004-2005, is appended to each narrative report. Back Row: Rob Hargraves (deceased), Satish Myneni, Greg van der Vink, Guust Nolet, Tony Dahlen, Jorge Sarmiento, John Suppe. Middle Row: Bob Phinney (emeritus), Lincoln Hollister, Peter Bunge, Ken Deffeyes (emeritus), François Morel, Michael Bender, Nadine McQuarrie, Bess Ward, Tullis Onstott. Front Row: Jason Morgan (emeritus), Tom Duffy, Franklyn van Houten (emeritus), Gerta Keller, George Philander, Bill Bonini (emeritus), Allan Rubin. Photo by Pryde Brown, with additions by Laurie Wanat. 3 gases in ice cores, and of dissolved gases in seawater. We also made a modest beginning on 2 new programs of ice core research. Here are some specfic accomplishments. Michael Bender Professor Ph.D., 1970, Columbia University email: [email protected] 1. We prepared for publication papers on the meridional gradient of O2 in air and its implications for the ocean carbon cycle, on the concentration and isotopic composition of O2 in Southern Ocean surface waters and their implications for the fertility of these waters, and on technical aspects of deriving a timescale climate records in slowly accumulating ice in East Antarctica. These papers are now either accepted or in revision. We also worked on several other manuscripts that are now in review. 2. Jan Kaiser participated in 2 cruises of the “Atlantic Meridional Transect” program and made measurements that strongly contradict the hypothesis that shallow, nutrient-poor ocean waters are chronically net heterotrophic (i. e., that respiration exceeds photosynthesis). The activities of my laboratory focus on studies of the geochemistry of O2, with applications to understanding the global carbon cycle and glacial-interglacial climate change. The geochemical properties we study are the concentration of O2 in air (which we measure to very high precision), and the relative abundance of the three stable O isotopes (16O, 17 O, and 18O) in O2. There are two subjects for the isotopic studies: O2 in fossil air extracted from ice cores, and dissolved O2 in seawater. The results inform us about a range of topics. Studies of the O2 concentration (or ratio of O2/N2) in air constrain the fate of fossil fuel CO2 that does not remain in the atmosphere. These measurements allow us to partition the “missing” CO2 between the oceans and the land biosphere. They also constrain rates of seasonal biological production by the oceans. Finally, they provide a test of models describing the global interaction of ocean circulation and biogeochemistry. The isotopic measurements of O2 in ice core trapped gases reflect the relative fertility of Earth’s biosphere, averaged over about 1,000 years. The triple isotope composition of O2 in seawater reflects the fraction of dissolved O2 from photosynthesis. O2 supersaturation reflects net production (photosynthesis in excess of respiration); by combining measurements of O2 concentrations and isotopes, we can determine rates of photosynthesis, respiration, and net production in aquatic ecosystems. Of course rate determinations of these processes in seawater have been made for many years; what makes our work new is that our approach does not require labor-intensive bottle incubations at sea, and our measurements can be made on large numbers of samples collected by colleagues on cruises of opportunity, and returned to the lab. Supplementing the O2 studies are studies of Ar. In seawater samples, Ar gives a measure of physical supersaturation due to warming of waters and bubble entrainment. In air samples, the Ar/N2 ratio reflects seasonal outgassing and ingassing due to temperature-driven solubility changes, and also to atmospheric mixing. 3. We began measurements in a collaboration with David Marchant, Boston University, to study ice of apparently great antiquity in the Dry Valleys, Antarctica. This ice underlies volcanic ash deposits dated as old as 10,000,000 years. The evidence suggests that the ice is older than the overlying ash, but this conclusion is highly controversial. If proved, it would allow us to measure the concentrations of greenhouse gases in bubbles of air trapped in the ice, and determine the carbon dioxide concentration of the atmosphere at times when Earth was much warmer than at present. We showed that the gases in the bubbles are original samples of trapped air, and we are currently developing isotopic methods for dating the ice. 4. We began a collaboration with Lonnie Thompson, Ohio State University, to date climate records of ice cores he has collected from tropical and temperate regions. To date our results confirmed the relatively recent age of the deep part of one core (ruling out the possibility that the bottom of this core might date back to the last ice age). Two-Year Bibliography Refereed articles: Hendricks, Melissa B., Michael L. Bender and Bruce A. Barnett Net and gross O2 production in the southern ocean from measurements of biological O2 saturation and its triple isotope composition, Deep-Sea Research Part I, 51, 15411561, 2004. Brook, E. J., J. W. C. White, Annie S. M. Schilla, Michael L. Bender, Bruce Barnett, Jeffery P. Severinghaus, Kedrick C. Taylor, Richard B. Alley, Eric J. Steig Timing of millennialscale change at Siple Dome, West Antarctica, during the last glacial period, Quaternary Science Reviews, 24, 1333-1343, 2005. Bender, M. L., D. T. Ho, M. B. Hendricks, R Mika, M. O. Battle, P. P. Tans, T. J. Conway, B. Sturtevant, and N. Cassar Atmospheric O2/N2 changes, 1993–2002: Implications for the partitioning of fossil fuel CO2 sequestration, Global Biogeochemical Cycles, 19, GB4017, doi:10.1029/2004GB002410, 2005. Hendricks, Melissa B., Michael L. Bender, Bruce A. Barnett, Peter Strutton, and Francisco Chavez The triple oxygen isotope composition of dissolved O2 in the equatorial Pacific: a tracer of mixing and biological production, Journal of Highlights of our research during the past year: Our primary focus was on preparing papers for publication and writing proposals for research funding. We continued our measurements of the O2/N2/Ar ratio of air, of trapped 4 Geophysical Research - Oceans, 110, C12021, doi:10.1029/ 2004JC002735, 2005. Kaiser, Jan, Matthew K. Reuer, Bruce Barnett, and Michael L. Bender, Marine productivity estimates from continuous oxygen/argon ratio measurements by shipboard membrane inlet mass spectrometry, Geophysical Research Letters,32, L19605, doi:10.1029/2005GL023459, 2005. Suwa, Makoto, Josepth C. von Fischer, Michael L. Bender, Amaelle Landais, and Edward J. Brook Chronology reconstruction for the disturbed bottom section of the GISP2 and the GRIP ice cores: implications for Termination II in Greenland, Journal of Geophysical Research - Atmospheres, in press. 2005. Bender, M. L., G. Floch, J. Chappellaz, M. Suwa, J._M. Barnola, T. Blunier, G. Dreyfus, J. Jouzel, and F. Parrenin Gas age-ice age differences and the chronology of the Vostok ice core, 0-100 ka, Journal of Geophysical Research – Atmospheres (in review), 2005. Reuer, Matthew K., Bruce A. Barnett, Michael L. Bender, Paul G. Falkowski, and Melissa B. Hendricks New estimates of Southern Ocean biological production rates from O2/Ar ratios and the triple isotope composition of O2, Deep Sea Research, in review, 2005. Articles in press or submitted: Battle, Mark, Sara Mikaloff Fletcher, Michael L. Bender, Ralph F. Keeling, Andrew C. Manning, Nicolas Gruber, Pieter P. Tans, Melissa B. Hendricks, David T. Ho, Caroline Simons, Robert Mika, and Bill Paplawsky Atmospheric potential oxygen: New Observations and their implications for some atmospheric and oceanic models of the global oxygen and carbon dioxide cycles, Global Biogeochemical Cycles, in press, 2005. boundary beneath Cape Verde, Cook Island and Cape Verde. This strong confirmation of the deep-mantle plumes seen in Raffa’s earlier P P-wave results is significant not only because the raypath coverage differs, but also because the off-path sensitivity of finite-frequency S waves differs from that of P waves. Raffa left Princeton in September to begin a new career as a research geophysicist for ExxonMobil in Houston. Fourth-year graduate student Tarje Nissen-Meyer made substantial progress during 2005 on his dissertation project, to compute exact waveform and traveltime sensitivity kernels in a background spherical earth model, using an axially symmetric spectral element method. Once the method is fully developed, it will be capable of computing the response of a spherical earth to a moment tensor or point force source up to 1-Hz frequency, substantially better than can be achieved with normal-mode summation codes. Individual 2-D codes are required for the monopole, dipole and quadrupole components of the source. At the present time, these three source types have been successfully implemented in the simple case of an earth model lacking a fluid outer core. Preliminary results have been submitted for publication as two back-toback papers Geophysical Journal International International. The next steps are to account for the core using a displacement potential representation, to optimize the mesh for a realistic spherical earth model such as PREM, and to parallelize the code for implementation on a small cluster. This work is being conducted in collaboration with Alex Fournier, who defended his Princeton Ph.D. dissertation in December 2003, and who is now a member of the faculty at the University of Toulouse. During the summer of 2005, I collaborated with Ying Zhou, who is now a postdoctoral fellow working with Jeroen Tromp at the Caltech Seismological Laboratory, to develop finite-frequency Fréchet sensitivity kernels for surface-wave group-delay and attenuation measurements. Quite unexpectedly, we found that a finite-frequency group delay exhibits strong sensitivity to the local phase velocity perturbation δc/c as well as to the local group-velocity perturbation δC/C. This dual dependence makes the inversion of measured surface-wave group delays for 2-D maps of δC/C a dubious F. Anthony Dahlen Department Chair Professor Ph.D., 1969, University of California, San Diego email: [email protected] In 2005 I continued my longstanding collaboration with Guust Nolet and postdoctoral fellow Raffaella Montelli, to account for finite-frequency wavefront healing effects in global seismic traveltime tomography. Raffa and I spent much of the summer repairing a minor error in our ray-theoretical crustal traveltime corrections. As expected, the repairs led to only minor changes in her P P-wave velocity images (Science Science 2004), and do not alter the important conclusion Scienc that there least six well-resolved plumes—Ascension, Azores, Canary, Easter, Samoa and Tahiti—that originate in the vicinity of the core-mantle boundary, as originally proposed by Jason Morgan more than thirty years ago. All of the observed plumes have a diameter of several hundred kilometers, indicating that plumes convey a substantial fraction of the internal heat escaping from the earth. In a recent paper submitted to the AGU electronic journal G3, Raffa has gone on to invert SS-wave traveltimes using finite-frequency sensitivity kernels, in order to provide an independent check on her very exciting P P-wave results. In fact, her recently obtained SS-wave images confirm the presence of the six well-resolved deep-mantle plumes listed above, as well as the existence of starting plumes that have not yet risen all the way to the earth’s surface beneath the Coral Sea, east of Solomon and south of Java, and plume conduits that are poorly resolved in the P P-wave tomography extending down to the core-mantle 5 Ampuero, J.-P. & Dahlen, F. A., Ambiguity of the moment tensor, Bull. Seismol. Soc. Amer., 95, 390-400, 2005. Dahlen, F. A., Finite-frequency sensitivity kernels for boundary topography perturbations, Geophys. J. Int., 162, 525-540, 2005. Nolet, G., Dahlen, F. A. & Montelli, R., Travel times of seismic waves: a reassessment, in Seismic Earth: Array Analysis of Broadband Seismograms, edited by Levander, A. & Nolet, G., Geophysical Monograph 157, American Geophysical Union, Washington, D.C., pages 37-47, 2005. Dahlen, F. A. & Nolet, G., Comment on ‘Onsensitivity kernels for ‘wave-equation’ transmission tomography’ by de Hoop and van der Hilst, Geophys. J. Int., 163, 949-951, 2005. Zhou, Y., Dahlen, F. A., Nolet, G. & Laske, G., Finite-frequency effects in global surface-wave tomography, Geophys. J. Int., 163, 1087-1111, 2005. procedure, unless the lateral variations in group velocity are extremely smooth. Guust Nolet and I are both very excited about a recently launched collaboration with Ingrid Daubechies in the Princeton mathematic department, to use wavelets and possibly curvelets as a basis for finite-frequency tomographic inversions. We will be joined in this project by Huub Douma, a new postdoctoral fellow, who recently received his Ph.D. from the Colorado School of Mines. Finally, in 2005, I was pleased to be able to continue my collaboration with Frederik Simons, who is now a member of the faculty at University College London, but who will join the geosciences department as our newest assistant professor in September 2006. We extended our spherical generalization of the one-dimensional time-frequency multitapers of Slepian and Thomson to the case of a double polar cap, for application to the so-called “polar gap” problem in satellite geodesy. Articles in press or submitted: Simons, F. J., Dahlen, F. A. & Weiczorek, M., Spatiospectral concentration on a sphere, SIAM Review, in press, 2005. Zhou, Y., Nolet, G., Dahlen, F. A. & Laske, G., Global upper-mantle structure from finite-frequency surface-wave tomography, J. Geophys. Res., in press, 2005. Dahlen, F. A. & Zhou, Y., Surface-wave group-delay and attenuation kernels, Geophys. J. Int., in press, 2005. Nissen-Meyer, T., Dahlen, F. A. & Fournier, A., Spherical-earth Fréchet sensitivity kernels, Geophys. J. Int., submitted, 2005. Nissen-Meyer, T., Fournier, A. & Dahlen, F. A., A 2-D spectralelement method for computing 3-D spherical-earth seismograms, Geophys. J. Int., submitted, 2005. Montelli, R., Nolet, G., Dahlen, F. A. & Masters, G., A catalogue of deep-mantle plumes: new results from finite-frequency tomography, Geoshem., Geophys, Geosystems, submitted, 2005. Montelli, R., Nolet, G. & Dahlen, F. A., 2005. Comment on ‘Banana-doughnut kernels and mantle tomography’ by van der Hilst and de Hoop, Geophys. J. Int., submitted, 2005. Simons, F. J. & Dahlen, F. A., Spherical Slepian functions and the polar gap in geodesy, Geophys. J. Int., submitted, 2005. Two-Year Bibliography Refereed Articles: Montelli, R., Nolet, G., Dahlen, F. A., Masters, G., Engdahl, E. R. & Hung, S.-H., Finite-frequency tomography reveals a variety of plumes in the mantle, Science, 303, 338-343, 2004. Dahlen, F. A., Resolution limit of traveltime tomography, Geophys. J. Int., 157, 315-331, 2004. Zhou, Y., Dahlen, F. A. & Nolet, G., 3-D sensitivity kernels for surface-wave observables, Geophys. J. Int., 158, 142-168, 2004. Baig, A. M. & Dahlen, F. A., Statistics of traveltimes and amplitudes of waves in random 3-D media, Geophys. J. Int., 158, 187-210, 2004. Montelli, R., Nolet, G., Master, G., Dahlen, F. A. & Hung, S-H., Global P and PP traveltime tomography: rays versus waves, Geophys. J. Int., 158, 637-654, 2004. Baig, A. M. & Dahlen, F. A., Traveltime biases in random media and the S-wave discrepancy, Geophys. J. Int., 158, 922-938, 2004. temperature of the deep mantle. We are exploring crystal structures, phase relations, elasticity, and other fundamental properties at these ultra-high pressure conditions. Experimental capabilities for studying materials at planetary interior conditions are progressing rapidly. For example, advances in synchrotron diffraction methods have expanded the P-T range accessible to direct measurements all the way up to 200 GPa and 3000 K, while at the same time leading to improved resolution that has resulted in dramatically better ability to recover crystallographic details. In combination with new geophysical observations of the Earth, we can now better address such fundamental questions as the origin of seismic discontinuities, chemical heterogeneity in the mantle, and the nature of the core-mantle boundary region. Thomas S. Duffy Associate Professor Ph.D., 1992, California Institute of Technology email: [email protected] My research program focuses on understanding the largescale physical and chemical behavior of Earth and other planets through experimental study of geological materials directly under extreme pressure and temperature conditions. We are using the diamond anvil cell together with laser heating and optical spectroscopy techniques at pressures and Phase transitions and crystal structures of deep Earth minerals Phase transformation in CaSiO3 perovskite Experimental studies have shown that the main rock types of the Earth’s mantle (e.g. peridotite, basalt) transform under 6 lower mantle conditions to assemblages dominated by minerals in the perovskite crystal structure. CaSiO3 perovskite is an important phase because it is thought to be the repository for many high-charge trace elements (including radioactive elements). This phase was long thought to possess cubic symmetry on the basis of many low-resolution x-ray diffraction experiments reported over ~20 years. We conducted the first high-resolution diffraction study of this material at 20-50 GPa [Shim et al., 2002] and showed that the symmetry of CaSiO3 perovskite at room temperature after laser heating is not cubic, but of lower symmetry, most likely tetragonal. Our result is consistent with theoretical calculations using density functional theory (DFT) and more recent experiments which suggest that the transformation from the low-symmetry to cubic form may occur under certain mantle conditions. Such a transition could be accompanied by significant anomalies in elastic properties and may therefore have relevance for interpretation of seismic profiles of the mantle. sistent with theoretical predictions. Upon decompression without further heating, it was found that the post-perovskite phase could still be observed at pressures as low at 12 GPa and evidence for at least partial persistence to ambient conditions was also obtained. We have recently carried out experiments using glass starting materials with compositions along the MgSiO3Al2O3 join to investigate the effects of Al content on the equation of state, transformation pressure, and stability limits of the new phase (Kubo et al., in preparation). The post-perovskite phase was synthesized for compositions with 0, 5, 15, and 20 mol. % corundum at maximum pressures between 145-164 GPa. For the En85Co15 composition, the perovskite to post-perovskite phase transformation was found to occur at 130 GPa and 1800 K, which is higher by ~10 GPa than the transition pressure in Al-free samples. In contract to earlier studies on pyrope compositions, our work suggests the two-phase (perovskite + post-perovskite) stability field is narrow, although analysis is complicated by the sluggish reaction kinetics. We also find that incorporation of Al has only a negligibly small effect on the unit cell volume of the post-perovskite phase in the 80-160 GPa pressure range. Due to the extreme high pressures of the transition and sluggish transformation rates, studies of the post-perovskite phase of MgSiO3 are challenging. Germanates are known to be excellent analogs for silicates as similar phase transitions occur but at significantly lower pressures in germanates. We have carried out a detailed set of synchrotron x-ray diffraction experiments on the post-perovskite phase of MgGeO3 in which we have synthesized the phase, measured its equation of state and refined the crystal structure (Rietveld method) over broad pressure intervals. Our equation of state measurements span a range from 7-201 GPa and place new constraints on the compressibility and structural anisotropy of the new phase (Kubo Kubo et al., 2005 2005). We could successfully conduct Rietveld refinements at very high pressures using data obtained between 80 and 110 GPa with both Ar and NaCl pressure media, including high temperature (14001700 K) data at ~90 GPa. Our structure refinements provide the first experimental constraints on the evolution of bond distances and angles with compression, thereby providing insight into the mechanisms by which the structure responds to compression (Kubo et al., in preparation). The structural response appears to be generally smooth over the pressure range investigated. Average Mg-O and Ge-O bond lengths at room temperature are consistent with those determined for other germanates and silicates. It is also notable that trends in structure parameters obtained by Rietveld refinement are qualitatively consistent with results of our theoretical (DFT) calculations. The temperature effect on average Mg-O bond length is strong while average Ge-O bond length is less sensitive to temperature. One of the most interesting properties of the D” region is that it possesses strong (and variable) seismic anisotropy. Interpretation of this anisotropy has been limited due to poor constraints on the lattice preferred orientation of D” constituents such as the post-perovskite phase. In collaboration Post-perovskite phase transition in silicates and germanates The Earth’s core-mantle boundary region, 2900 km below the surface, is highly complex and potentially holds the key to a host of questions about the planet’s interior and evolution. Thus, the recent discovery of a post-perovskite phase in MgSiO3 at 125 GPa, close to conditions expected for the D” region has major potential implications for understanding geophysics of the deep mantle. We have been pursuing a number of lines of research related to the post-perovskite phase. We had previously demonstrated the stability of MgSiO3 perovskite to 108 GPa [Shim et al., 2001] and reported evidence for a potential modification within the perovskite structure. The existence of the post-perovskite phase was later confirmed in MgSiO3 on the basis of angle-dispersive diffraction at 144 GPa [Shim et al., 2004]. Besides the crystal structure, the equation of state (EOS) is the most fundamental parameter obtained from high-pressure experiments. Using the laser-heated diamond anvil cell, we have recently investigated the equation of state of coexisting perovskite and post-perovskite (CaIrO3-type) phases synthesized from a natural pyroxene composition with Fe content close to that expected for the lower mantle (Shieh et al., 2005 2005). Our measured pressure-volume data for the postperovskite phase from 12-106 GPa yield a bulk modulus of 219(5) GPa and a zero-pressure volume of 164.9(6) Å3 when K0’=4. The bulk modulus of post-perovskite is 575(15) GPa at a pressure of 100 GPa. These results are broadly consistent with theoretical calculations and put limits on the effect of Fe content on the bulk modulus. Our x-ray diffraction data indicate the post-perovskite phase can be formed in this composition at P-T conditions corresponding to ~400-550 km above the core-mantle boundary. Direct comparison of volumes of coexisting perovskite and CaIrO3-type phases at 80-106 GPa demonstrates that the post-perovskite phase has a smaller volume than perovskite by 1.1(2)%. Using measured volumes together with the bulk modulus calculated from EOS fits, we find that the bulk sound velocity decreases by 2.3(2.1)% across this transition at 120 GPa, again con7 with R. Wenk’s group at Berkeley, we have carried out the first experimental deformation study of the post-perovskite phase (of MgGeO3 composition) in the diamond anvil cell at 104-130 GPa and ambient temperature (Merkel Merkel et al., 2005 2005). Previous phenomenological considerations had suggested that (010) or (001) may be the dominant slip planes, based on either the nature of layering in the structure or comparison of theoretical elastic constants with seismic constraints. However, our results showed that slip on (100) or (110) planes dominated plastic deformation, in good agreement with a recent independent theoretical study which found that (110) slip could produce a series of polytype structures intermediate between perovskite and post-perovskite. With the assumption that silicate post-perovskite behaves similarly at lower mantle conditions, a quantitative model of this phase’s contribution to seismic anisotropy in D” was constructed. Studies of the post-perovskite phase remain challenging and there are many unanswered questions that will be a focus for future research. Our equation of state studies will be extended to more complex compositions and new analytical techniques for examining the quenched samples are being adopted. Plastic deformation studies will soon be extended to silicate compositions. diamond anvil cell using finite element calculations (Kiefer and Duffy, 2005 2005). We carried out simulations using a realistic experimental geometry (including insulation layers between the diamonds and sample) to investigate the factors controlling development of axial and radial thermal gradients for optically thin samples. The two key parameters for controlling the axial thermal gradient are the ratio of sample to insulator thermal conductivity and the ratio of the sample thickness to total gap between the diamonds. We also systematically quantified the magnitude of the axial temperature gradients as these parameters are varied. On-going work is focused on simulating more closely the actual complex sample geometries that are used in practice for both CO2 and Nd:YLF laser heating. For example, we have simulated single- and double-sided hot plate geometries, single- and double-sided heating of metallic samples and the micro-furnance geometry. We have also systematically investigated the effects of different laser modes. The results in some cases confirm preconceptions, but in several cases rather surprising results are obtained. These calculations promise to yield insights that will lead to improved experimental designs to yield more homogeneous pressure-temperature conditions in the sample. Phase transitions in SnO2 to megabar pressures There are many other systems with potentially interesting phase relations in the Mbar regime to be explored. As one example, the metal dioxides exhibit extensive polymorphism at high pressures, and a variety of transformation pathways leading to highly coordinated structures have been uncovered. Some high-pressure polymorphs in these systems have very high bulk moduli and may qualify as strong or even superhard solids. Many of these phases have been investigated as analogs for SiO2 as they exhibit similar sequences of transitions but at lower pressures compared with silica. Our high-pressure and high-temperature x-ray diffraction study of SnO2 demonstrates the existence of four phase transitions during compression to 117 GPa. The observed sequence of high-pressure phases for SnO2 is rutile-type ((P4 P42/mnm) → CaCl2-type (Pnnm) → pyrite-type ( ) → ZrO2 orthorhombic phase I (Pbca) → cotunnite-type (Pnam). The latter two phases were observed here for the first time in this system. The bulk moduli for the Pbca (259 GPa) and Pnam (417 GPa) phases of SnO2 determined by fitting pressurevolume data to the second-order Birch-Murnaghan equation of state indicate these high-pressure phases are highly incompressible – although the potential role of deviatoric stress still needs better characterization. Rietveld refinements of powder diffraction patterns for both phases have been successfully carried out. Our static high-pressure results also enable us to provide an interpretation for previous shock compression data that show evidence for two discontinuities along the Hugoniot curve. Our results indicate that the first transformation may be associated with the formation of the Pbca phase whereas the second transformation is consistent with the cotunnite-type phase. Elastic properties of minerals and structure of the mantle The elastic tenor is fundamental to a range of solid-state phenomena including elastic wave propagation, mechanical stability, interatomic interactions, material strength, equation of state, and phase transition mechanisms. The single-crystal elastic properties of minerals are essential for interpretation of the seismic velocity structure of the Earth’s mantle. Despite this importance, the elastic properties of many mantle minerals are poorly constrained, particularly for low-symmetry species at elevated pressures. Brillouin scattering is a method whereby one can measure the complete elastic tensor by recording the frequency shift induced in scattered laser light by thermally generated sound waves. We are using this technique in the diamond anvil cell to investigate the singlecrystal elastic properties of a variety of minerals at pressures corresponding to depths as great 1000 km. Elasticity of olivines and garnets The single-crystal elasticity of fayalite (Fe2SiO4) was measured to 12 GPa by Brillouin scattering at ambient temperature (Speziale et al., 2004), more than an order of magnitude higher pressure than previous investigations. Fayalite is challenging because it is Fe-rich, of low symmetry (orthorhombic), and good crystals are rare. Nevertheless, we could recover the 9 elastic stiffness moduli as well as crystal orientation information by an extensive measurement program using several natural crystals. Our results demonstrate unequivocally that the bulk modulus of olivine increases with iron content, and this effect is enhanced by the application of pressure. The shear constants C44 and C55 show non-linear pressure dependence at P>5 GPa, and this leads to non-linear behavior in the aggregate shear modulus as well. The softening of C44 is comparable to the behavior observed in Mg-rich olivines, but softening of C55 is much stronger in the Fe-rich composition. This shear softening of high-pressure meta- Finite element simulations of the laser-heated diamond cell We have examined the thermal structure of the laser-heated 8 stable fayalite is likely connected to the previously observed pressure-induced amorphization above 35 GPa. We have also carried out single-crystal elasticity studies of three natural garnets (grossular, almandine-pyrope, and andradite) to above 11 GPa ((Jiang et al., 2004a; Jiang et al., 2004b). Garnets are major constituents of the Earth’s upper mantle. They have high symmetry and exhibit a great deal of compositional variability, making them an ideal testing ground for our understanding of elasticity variations in mineral systems. In combination with other Brillouin scattering data for pyrope, our results allow us to constrain the effect of Fe-Mg substitution on the dodecahedral site in pyropealmandine and Fe-Al substitution on the octahedral site in andradite-grossular at high pressures. This was not possible previously due to systematic differences between results at high pressures from different experimental techniques. Brillouin scattering measurements (at ambient or high pressures) and pressure-volume equation of state data were shown to be a powerful combination for evaluating the reliability and potential pitfalls of static compression measurements (e.g. deviatoric stress effects, parameter tradeoffs). Global seismological and geodynamic models require an assessment of not only thermal effects on seismic velocities but also compositional effects. Our new elasticity measurements together with selected values from the literature have allowed us to comprehensively evaluate the sensitivity of seismic velocity to composition, pressure, and temperature for major upper mantle minerals (Speziale Speziale et al., 2005 2005). Logarithmic compressional and shear velocity variations with respect to iron content are most strongly sensitive to crystal structure but pressure and temperature effects may also be important at upper mantle conditions. As one example of the findings from this study, the very different responses of olivines and garnets to iron substitution gives rise to significant variations in the sensitivity of different rock types to iron concentration in accordance with their garnet content. Velocities in mid-ocean ridge basalts are thus much less affected by variations in iron content than other rock types such as harzburgite. These differences need to be accounted for in evaluating the effects of Fe variability on seismic velocity heterogeneity. longitudinal moduli, C11/C33, decreases from 3.3 at ambient pressure to 1.2 at 15 GPa. The epidote family is a group of hydrous Ca-Al silicates that may be important water carriers in cold subducting slabs. In general, little is known about the elastic properties of Ca-Al silicates. Our measurements of the elastic tensor of the epidote-member zoisite at ambient pressure (Mao et al., in preparation) place the first experimental constraint on zoisite’s shear modulus and resolve discrepancies in the bulk modulus from static compression experiments. In addition to continued characterization of single-crystal elastic properties of important mantle phases and their variation with chemistry and structure, we are also focusing future efforts on examining elastic anomalies associated with high-pressure phase transitions. Over the longer term, we plan to develop equipment for carrying out Brillouin scattering at simultaneous high pressures and temperatures, and to extend measurements to higher pressures, particularly for polycrystalline samples. Yield strength at high pressures The yield strength of materials at high pressure is a fundamental property that has not yet been well characterized. Static strength determination is a preliminary step toward eventual characterization of the complete flow laws that govern rheological properties at high pressure or deep Earth conditions. Among the basic questions are how pressure affects yield strength, how relative strengths of different classes of materials compare at ~1 Mbar, and whether theoretically predicted strength inversions (e.g. strengths of rare gas solids exceeding those of metals) can occur at ultrahigh pressures. Knowledge of strength properties is also important for optimizing the design and performance of high-pressure apparatus. Quantitative evaluation of differential stresses developed under various pressure-transmitting media is one example in this regard. Elasticity and strength are interconnected properties that play a mutual role in several basic areas of highpressure science such as development of accurate pressure calibration. Interest in strength properties is also driven by several themes in current materials research including theoretical determinations of ideal shear strength, the connection between strength and particle size in the nano-crystalline realm, and the search for new super hard solids. In the radial x-ray diffraction technique, a sample is compressed in a diamond cell under intentionally non-hydrostatic conditions and the lattice strain is measured as a function of angle from the loading axis using synchrotron x-rays. Such studies can constrain yield strength and provide insights into other properties including elastic moduli, equation of state, and texture development to very high pressures. In ongoing research over the last seven years, we have used this method to characterize the strength of a suite of metals, oxides, silicates, and nitrides. Our recent studies have included: tungsten (He He and Duffy, 2005 2005), platinum (Kavner and Duffy, 2003); MgGeO3 post-perovskite (Merkel et al., 2005), SiO2 (Shieh 2005 Shieh et al., 2002 2002), CaSiO3 (perovskite) (Shieh et al., 2004 2004), CaO (Speziale et al., 2005), B6O (He and Duffy, 2004), and cubic-Si3N4 (Kiefer et al., 2005). In general, Elasticity of hydrous minerals The elastic properties of subduction zone minerals are necessary for understanding basic features of the subduction factory including the existence and distribution of hydrous phases and the effect on seismic wavespeeds of thermal and metamorphic processes. Modeling of seismic velocities in subduction zones is greatly limited by lack of constraints on the elastic properties of the metamorphic phases expected to exist there. We have begun to address this problem by measuring the elastic tensors (at ambient and high pressures) of a suite of hydrous minerals including brucite, diaspore, alunite, and zoisite. The elasticity of brucite has been measured to 14 GPa ((Jiang Jiang et al., 2005 2005). ). Brucite shows highly anomalous elastic properties including the largest shear modulus pressure derivative (Gʹ=3.6) yet measured. The elastic anisotropy of brucite changes strongly with pressure. The ratio of the 9 He, D. W. and T. S. Duffy, Equation of state and strength of boron suboxide from radial x-ray diffraction in a diamond cell under nonhydrostatic compression, Physical Review B, 70, 184121, 2004. Jiang, F., S. Speziale, and T. S. Duffy, Single-crystal elasticity of grossular- and almandine-rich garnets to 11 GPa, Journal of Geophysical Research, 109, B10201, 2004. Shieh, S. R., T. S. Duffy, and G. Shen, Elasticity and strength of calcium silicate perovskite at lower mantle pressures, Physics of the Earth and Planetary Interiors, 143 144, 93-106, 2004. Shim, S.-H., T. S. Duffy, R. Jeanloz and G. Shen, Stability and crystal structure of MgSiO3 perovskite to the core-mantle boundary, Geophysical Research Letters, L10603, 2004. Yin, H. Z., K. D. Hobart, F. J. Kub, S. R. Shieh, T. S. Duffy, J. C. Sturm, High-Ge content SiGe islands formed on compliant oxide by SiGe oxidation, Applied Physics Letters, 84, 36243626, 2004. Shim, S.-H., T. S. Duffy, R. Jeanloz, C.-S. Yoo, and V. Iota, Raman spectroscopy and x-ray diffraction of phase transitions in Cr2O3 to 61 GPa, Physical Review B, 69,144107, 2004. Jiang, F., S. Speziale, S. R. Shieh, and T. S. Duffy, Single-crystal elasticity of andradite garnet to 11 GPa, Journal of Physics: Condensed Matter Matter, 16, S1041-S1052, 2004. Speziale, S., F. Jiang, and T. S. Duffy, Compositional dependence of the elastic wave velocities of mantle minerals: Implications for seismic properties of mantle rocks, Structure, Composition, and Evolution of Earth’s Mantle, edited by R. van der Hilst, J. D. Bass, J. Matas, and J. Trampert, AGU, Washington, DC, 303-323, 2005. Duffy, T. S., Synchrotron facilities and the study of deep planetary interiors, Reports of Progress in Physics, 68, 1811-1859, 2005. Yin, H., K. D. Hoburt, R. L. Peterson, S. R. Shieh, T. S. Duffy, J. C. Sturm, Tunable uniaxial vs biaxial in-plain strain in integrated silicon and silicon-germanium thin films using compliant substrates, Applied Physics Letters, 87, 061922, 2005. Kiefer, B., S. R. Shieh, T. S. Duffy, and T. Sekine, Strength, elasticity, and equation of state of nanocrystalline cubic silicon nitride (c-Si3N4) to 68 GPa, Physical Review B, 014102, 2005. Shieh, S. R., T. S. Duffy, and G. Shen, X-ray diffraction study of phase stability in SiO2 at deep lower mantle conditions, Earth and Planetary Science Letters, 235, 273-282, 2005. Kiefer, B. and T. S. Duffy, Finite element simulations of the laserheated diamond anvil cell, Journal of Applied Physics, 97, 114902, 2005. strength increases with compression at a rate greater than the shear modulus, implying significant strain hardening under diamond cell loading conditions. At pressures of 20-80 GPa, metals typically exhibit strengths of 1-3% of the shear modulus, G. For silicates, six-coordinated silicates exhibit lower strengths relative to their shear modulus (2-4% G) G compared with four-coordinated silicates (4-7% G G). Strong covalent oxides, silicates, and nitrides such as ringwoodite, boron suboxide, and spinel-structured silicon nitride possess yield strengths that can approach 10% of the shear modulus. The maximum strength value we have measured is 28 GPa for B6O at 65 GPa confining pressure. The general increase in strength with pressure for all material classes implies that most materials are “strong” at megabar pressures if one recognizes that the strength of high-grade steel at ambient pressure is ~2 GPa. Furthermore, the consistency of general strength trends across material classes suggests that reasonable empirical predictions of strength in the multimegabar pressure regime can now be made, and this is borne out by our recent data on tungsten metal. Combination of radial x-ray diffraction and Brillouin scattering at high pressures is a potentially powerful technique for constraining mechanical properties at high pressures. We carried out a study of calcium oxide, CaO, by both Brillouin scattering (to 23 GPa) and by radial nonhydrostatic x-ray diffraction (to 65 GPa) (Speziale Speziale et al., 2005 2005). Calcium oxide supports a low differential stress of ~1% of the shear modulus (<2 GPa at high pressures). The Brillouin results show a softening of C44 and consequent increase in the elastic anisotropy in qualitative agreement with theoretical predictions. Over the common pressure range, Brillouin and radial diffraction data yield results in very good agreement for the elastic tensor. However, the radial diffraction data diverge from the extrapolation of Brillouin results at higher pressures, perhaps related to the onset of plasticity or modification to stress/strain continuity relationships. There are a number of directions for future developments in this area. Additional measurements are needed for both the softest and hardest materials; the former to better quantify stress states actually achieved in experiments, and the latter to better characterize the properties of ultrahard solids. On the technical side, advances in diamond cell technology will be pursued to improve the capabilities of the diamond cell as a deformation device with the goal toward eventual direct examination of rheological properties at very high P-T conditions. Other miscellaneous publication: Duffy, T. S., Deeper understanding, Nature, 430, 409-410, 2004. Rubie, D. C., T. S. Duffy, and E. Ohtani, New developments in high-pressure mineral physics and applications to the Earth’s interior, introduction to special issue, Physics of the Earth and Planetary Interiors, 143-144, 1-3, 2004. Yin, H., K. D. Hobart, S. R. Shieh, R. L. Peterson, T. S. Duffy, and J. C. Sturm, Interference-enhanced Raman Scattering in Strain Characterization of Ultra-thin Strained SiGe and Si Films on Insulator, in High-Mobility Group-IV Materials and Devices, edited by M. Caymax, E. Kasper, S. Zaima, K. Rim, and P. F. P. Fichtner, Materials Research Society, Warrendale, Pa, vol. 809, pp. B3.6.1-B.3.6.3, 2004. Two-Year Bibliography Books: Rubie, D. C., T. S. Duffy, and E. Ohtani, editors, New Developments in High-Pressure Mineral Physics and Applications to the Earth’s Interior, Elsevier, Amsterdam, pp. 625, 2004. Chen, J., Y. Wang, T. S. Duffy, G. Shen, and L. Dobrzhinetskaya, Advances in High Pressure Technology for Geophysical Applications, Elsevier, Amsterdam, pp. 512, 2005. Articles in press or submitted: Jiang, F., S. Speziale, and T. S. Duffy, Single-crystal elasticity of brucite, Mg(OH)2, to 14 GPa by Brillouin scattering, Physical Review B, submitted, 2005. 7He, D. W., and T. S. Duffy, Static strength of tungsten to 69 GPa, Physical Review B, submitted, 2005. Refereed articles: Speziale, S., T. S. Duffy, and R. J. Angel, Single-crystal elasticity of fayalite to 12 GPa, Journal of Geophysical Research, 109, B10201, 2004. 10 Merkel, S., A. Kubo, L. Miyagi, S. Speziale, H.-k. Mao, T. S. Duffy, and H.-R. Wenk, Plastic deformation of MgGeO¬3 post-perovskite at lower mantle pressures, Science, in press, 2005. Shieh, S. R., A. Kubo, T. S. Duffy, V. B. Prakapenka, and G. Shen, High-pressure phases in SnO2 to 117 GPa, Physical Review B, in press, 2005. Shieh, S. R., T. S. Duffy, A. Kubo, G. Shen, V. B. Prakapenka, N. Sata, K. Hirose, and Y. Ohishi, Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO3 orthopyroxene, Proceedings of the National Academy of Sciences, in press, 2005. Speziale, S., S. R. Shieh, and T. S. Duffy, High-pressure elasticity of calcium oxide: A comparison between Brillouin scattering and radial x-ray diffraction, Journal of Geophysical Research, in press, 2005. Kubo, A., B. Kiefer, G. Shen, V. Prakapenka, R. J. Cava, and T. S. Duffy, Stability and equation of state of MgGeO¬3 postperovskite phase to 2 Mbar, Geophysical Research Letters, submitted, 2006. Bhutan. With my colleague Djordje Grujic at Dalhausie University, we have defined a process in mountain building, based on our studies in Bhutan. This process involves the rapid extrusion of a low viscosity, partially melted orogenic channel from lower crustal depths. It was published in 2002. In 2005 we completed an article on pulsed channel flow in Bhutan. This rationalizes seemingly contradictory field data to the theoretically based channel flow model of Beaumont and others. I have helped recruit Bhutanese students to study geology in USA. Two recently received MS degrees at UTEP, and one of these, Tobgay Tobgay, is expected to come to Princeton for a Ph.D. Lincoln S. Hollister Professor Ph.D., 1966, California Institute of Technology email: [email protected] Lamellar magnetism. Following up on our hypothesis (Hollister, et al, 2004) that reheating of ilmenohematite may explain anomalous remanent magnetization in rocks along the west coast of North America, I am collaborating on a NSF proposal funded through UC Berkeley to test the hypothesis. The graduate student working on the project is one of our former undergraduate students. We may be headed for a solution to the Baja British Columbia controversy, which holds that parts of western Canada traveled from latitudes corresponding to Baja California during the latest Cretaceous. How are mountains and continental crust made? These are the major questions driving my research and teaching. I interpret the pressure-temperature-time-strain history of rocks in the context of the tectonic processes operating on the continental crust. My contributions are based on direct observation of the products of mountain building. I have forged collaborations with people in other disciplines and work in an interdisciplinary mode where the objective is to achieve results unattainable by individual investigators. I also help students learn how to use field observations in the construction of hypotheses, and for eliminating alternatives. My research is on three fronts: the origin of the Coast Mountains of British Columbia, the origin of the Himalayas in Bhutan, and the application of lamellar magnetism for resolving the Baja British Columbia controversy. Two-Year Bibliography Refereed articles: Hollister, L. S., R. B. Hargraves, T. S. James, and P. R. Renne, The paleomagnetic effects of reheating the Ecstall pluton, British Columbia. Earth and Planetary Science Letters v. 221, 397 407, 2004. Batholiths. My biggest research commitment for the next few years is the new multidisciplinary collaboration, called BATHOLITHS, which proposes to resolve the continental crust composition paradox: although continental crust begins as accreted island arcs the average composition of continental crusts is more silicic than that of island arcs. Before becoming stable continental crust, the original island arc composition is modified by processes that are not understood. This is a fundamental problem in the earth sciences. The disciplines of BATHOLITHS include active and passive source seismology, geochemistry, structural geology, and petrology. Most of these endeavors are underway, but the active source seismology experiment has been delayed due to ship scheduling problems and to complexities in obtaining Canadian environmental permits. For information on the permitting process, see http://www.eos.ubc.ca/research/batholiths/ Other miscellaneous publications: Clowes, R.M., L.S. Hollister, G.Woodsworth, BATHOLITHS: How the Coast Mountains of British Columbia Formed. Informational Brochure for EA and Outreach. 16pp. http://www. eos.ubc.ca/research/batholiths/, 2005. Clowes, R.M., L.S. Hollister, G. Woodsworth, Batholiths: learning how the Coast mountains of British Columbia formed. Informational sheet; 2 pp. http://www.eos.ubc.ca/research/ batholiths/, 2005. Articles in press or submitted: Hollister, L.S. & D. Grujic,, in press, Pulsed Channel Flow in Bhutan. Geological Society of London Special Publication on Channel Flow, Ductile Extrusion and Exhumation of Lower-mid Crust in Continental Collision Zones. Hollister, L.S., J. Diebold, T. Das, in revision, Whole crustal response to Late Tertiary extension near Prince Rupert, British Columbia. Canadian J. Earth Sciences. 11 Two-Year Bibliography Gerta Keller Refereed articles: Keller, G., Paleoecology of Late Maastrichtian-early Danian planktic foraminifera in the eastern Tethys (Israel and Egypt). J. Foram. Res., 34(1): 49-73, 2004. Keller, G. and Pardo, A., Paleoecology of the CenomanianTuronian Stratotype Section (GSSP) at Pueblo, Colorado. Marine Micropleontology, 51: 95-128, 2004. Keller, G., Stueben, D., Berner, Z. and Adatte, T., CenomanianTuronian δ13C, δ18O, sea-level and salinity variations at Pueblo, Colorado. Paleoclimatol. Paleoecol. Paleogeogr., 211, 19-43, 2004. Keller, G., Adatte, T., Stinnesbeck, W., Rebolledo-Vieyra, M., Urrutia Fucugauchi, J., Kramar, U. and Stueben, D., Chicxulub crater predates K-T boundary mass extinction.PNAS, 101(11): 3721-3992, 2004. Keller, G., Adatte, T., Stinnesbeck, W., More Evidence that Chicxulub predates KTboundary. Meteoritics and Planetary Science (MAPS), 39,(6/7), 1127-1144, 2004. Wolfgang Stinnesbeck, Gerta Keller, Thierry Adatte, Markus Harting, Doris Stüben, Georg Istrate and Utz Kramar: Yaxcopoil-1 and the Chicxulub impact. International Journal of Earth Sciences, Volume 93, Number 6, pp. 1042 - 1065, 2004. Keller, G. and Pardo, A., Disaster Opportunists Guembelitrinidae – Index for Environmental Catastrophes. Marine Micropaleontology, 53, 83-116, 2004. Adatte, T. Keller, G., Stueben, D., Harting, M., Kramar, U., Stinnesbeck, W., Abramovich, S. and Benjamini, C., Late Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace element and platinum group elements, biostratigraphy and faunal turnovers. Bulletin Société Géologique de France, 176, 1, 35-53, 2005. Keller, G., Biotic effects of late Maastrichtian mantle plume volcanism: implications for impacts and mass extinctions. Lithos, 79, 317-341, 2005. Keller, G. Impacts, volcanism and mass extinctions: random coincidence or cause & effect? Australian Journal of Earth Sciences, 52, 725-757, 2005. Stueben, D., Harting, M., Kramar, U., Stinnesbeck, W., Keller, G., and Adatte, T., High resolution geochemical record in Mexico during the Cretaceous-Tertiary transition. Geochmica et Cosmochimica Acta, 69, (10), 2559-2579, 2005. Stinnesbeck, W., Ifrim, C., Schmidt, H., Rindfleisch, A., Buchy, M-C., Frey, E., González-González, A.H., Vega, H.J., Cavin, L., Keller, G. and Smith, K.T., 2005. A new lithographic limestone deposit in the Upper Cretaceous Austin Group at El Rosario, County of Muzquiz, Coahuila, Northeastern Mexico. Revista Mexicana Ciencias Geologicas, v. 22 (3), 401-418. Professor Ph.D., 1978, Stanford University email: [email protected] During the past two years the 15 year long research project on the Cretaceous-Tertiary boundary impact and mass extinction has culminated in spectacular success with the coming together of empirical evidence from sedimentology, stratigraphy, paleontology, mineralogy, geochemistry and paleomagnetic stratigraphy. The environmental history revealed by all of these disciplines indicates that the current impact mass extinction scenario can no longer be supported. The Chicxulub impact, commonly believed to be the cause for the KT mass extinction, predates this mass extinction by 300,000 years. A second impact together with major Deccan volcanism is the likely cause for the mass extinction. Our new theory and its supporting evidence has been carried by news outlets all over the world and more than 100 news articles have appeared in international magazines, including top journals like Nature, The Economist, La Recherche, Der Spiegel, Focus, Facts etc. and the Geological Society of London has sponsored a debate on my team’s work (Geoscientist, November, 2003). Six documentary films have been made over the past year, including BBC Horizon (released in October 2004 in the UK), ABC, the History Channel, Swiss TV (released Nov. 24), The New York Museum of Natural History, (released May 2005) and TV interview with Alexander Kluge for German Film, TV and Media released October 2005. Accomplishments during 2005 include the successful drilling of the K-T boundary sequences along the Brazos River in Texas funded by NSF. These cores form a critical part in testing the new impact theory and preliminary results confirm previous studies. New drilling of K-T sequences near Recife in Brazil, also funded by NSF, commenced in September and finished at the end of December 2005 with nearly 100% core recovery. The three core localities recovered K-T sequences with the purpose of assessing the environmental effects of the Chicxulub impact at 8000km from its crater. The cores will be shipped to Princeton in early 2006. Other miscellaneous publications: Keller, Suche nach der Ursache des Massensterbens vor 65 Millionen Jahren. Werdenberger Jahrbuch, p. 189-200, 2004. Keller, La Météorite innocentée. La Recherche, 379, 30-36, 2004. Articles in press or submitted: Keller, G. and Pardo, A., Guembelitria and Heterohelix Blooms – Planktonic proxies for Environmental Catastrophes. Cretaceous Research, in press. Harting, M., Keller, G., Stinnesbeck, W., Volker, Z. and Fotouh, M., Geochemical characterisation of Chicxulub-Impact ejecta: New constraints from the Gulf of Mexico and the Caribbean. EPSL, in prep. A 2000 word summary of our results is published in the Geoscientist and can be downloaded at http://www.geolsoc.org.uk/template.cfm?name=NSG23498 57238495 12 in the December issue of Geospheres, 2005. The power of these sequential reconstructions come from 1) highlighting areas that are not strain compatible and require additional research on the timing, magnitude and style of deformation. Richard Lease for his Sr. Thesis conducted field research to constrain the amount and timing of fault offset in the Mojave portion of the Eastern California Shear Zone (ECSZ). The palinspastic reconstructions modeled through the Arc GIS script required large fault displacements through the eastern Mojave, but the geologic data to support model offsets were unavailable. Richard found a unique marker offset along the fault, which suggests 22± 5 km of offset (15-25 km more than previous estimates), and provided a positive field test for kinematic compatibility models. 2) The palinspastic reconstructions allow us to restore other data sets of interest, such as the volcanic eruptive centers through the Basin and Range. For her Sr. Thesis, Margee Prat started integrating the ARC GIS database of extension in the central Basin and Range with the NAVDAT (North American Volcanic) Database. Together these data sets have the potential to show how mantle lithospheric thickness has evolved with time in conjunction with crustal thinning, as well as provide insight into geodynamical links between extension and volcanism in this region. Nadine McQuarrie Assistant Professor Ph.D., 2001, Arizona University email: [email protected] My research focuses on the kinematic evolution of mountain belts. My interests range from evaluating the sequential accumulation of strain in folds and faults that form a wide (350-350 km), high elevation plateau to the kinematics and dynamics of diffuse continental extension. Research projects start with structurally based field studies, typically through the creation of new geologic maps at previously unpublished scales or resolutions. Projects also typically involve the creation and sequential restoration of cross sections to evaluate viable kinematic deformation histories. Current projects I am working on in conjunction with colleagues and students are: 1) tectonic reconstructions of the North America-Pacific plate boundary over the last 36 Myr, 2) the interaction between erosion and deformation in fold-thrust belts in Bolivia 3) the fundamental controls on the width of mountain belts, specifically looking at the northern edge of the Andean Plateau in Peru and 4) how has deformation evolved in time and space during arc-continent collision in Timor. Interaction between erosion and deformation in foldthrust belts: Quantifying the interactions of lithology, tectonics and climate on multi-scale morphologies of mountain ranges is at the forefront of current geological research. One of the central facets to this research is the magnitude of control climate and the associated erosion has on the formation and development of orogens. Active research in Bolivia (collaborative research with Dr. Todd Ehlers and graduate student Jason Barnes at University of Michigan) use lowtemperature thermochronometry, field-constrained structural analysis, and numerical models to delineate the kinematic evolution of the fold-thrust belts, and the impact of erosional variations on their formation. In Bolivia we have obtained cooling ages and structural data that has been combined in a preliminary kinematic model of how the fold thrust belt has developed through time. We have used new mapping to construct a balanced cross section across the Andean plateau from the volcanic arc to the undeformed foreland. The restored cross section was imported into 2-D MOVE (a cross section restoration program) and the displacement along folds and faults was forward modeled providing a quantitative description of the kinematics (displacement, velocity, velocity change) of fold-thrust belt deformation. The simulated velocity field will be the input into 2D and 3D thermo-mechanical models that link uplift and erosion to an evolving thermal field. This thermal history is used to calculate and predict apatite fission track and apatite and zircon (U-Th)/He sample ages. Tectonic reconstructions of the North America-Pacific plate boundary: Precise displacement fields of continental deformation are becoming increasingly more common and exact through the advent and expansion of global positioning systems (GPS). However, displacement histories over much longer scales (105-107) are required for addressing questions of how the lithosphere responds to major changes in plate geometry and kinematics. For many regions on earth the detailed geologic history necessary for long-term displacement fields is just not available. However, in western North America more is known about timing, amount, and spatial variations of deformation than any other comparable region. By using an Arc GIS (global information systems) database of timing, magnitude and direction of deformation, we can sequentially restore deformation through western North America with time creating a series of palinspastic maps from 36 million years ago to present. The data from these maps can be displayed in a variety of ways that highlight not only the areas where the reconstructions are accurate, but more importantly where the reconstructions are inaccurate (implying where more field-based data are needed). The maps can also be displayed as a movie that illustrates how extension varies with time and as velocity fields over 2-5-10 m.y. increments that can be compared to the modern GPS strain field. The first version of these reconstructions was published Controls on orogen width: The Andes mountains extend over 8000 km along the western side of the South American continent. Significant along strike changes in morphology, structure and zonal climate regimes make the South American Andes an ideal location to look at the factors that control 13 orogen width. Interesting, the widest portion of the Andes, between 12° and 27° S, is also the driest suggesting the lack of erosion is an important factor in broad (350-550 km) high (4-5 km) plateaus. One of the most abrupt along strike changes in morphology of the Andes is along the northern edge of the Andean plateau in Peru. Here a wide zone (~350 km) of high topography with minimal vertical relief transitions abruptly into a significantly narrower (150 km) mountain range with a narrow drainage divide. This west stepping, right angle bend in topography is mimicked in the structural elevation (i.e. stratigraphic erosion level) of lower Paleozoic rocks. This significant change in topographic and structural width provides a unique opportunity to evaluate the factors that govern the width of orogens. This last summer, Nicole Gotberg (graduate student) and I mapped 2 transects through the Peruvian Andes. The northern transect was through the narrow portion of the mountain range and the southern transect was across wide, northern border of the Andean plateau. One of the surprising things that we found was although the stratigraphy varies significantly across the Northern Plateau boundary, the cumulative stratigraphic thickness if each region (north and south) is essentially the same. This fall Nicole has been digitally combining her mapping with Peruvian geologic maps to create new geologic maps that can be used as the bases for balanced cross sections across each region. A map of the northern edge of the Andean Plateau and an accompanying geologic cross section will be products of Nicole’s first year project. deformation history and 4) Rocks which can provide cooling ages of apatite grains which indicate the window of time these rocks were cooled through uplift and erosion. These ffactors allow is to quantify both rates of crustal shortening as well as rates of surface uplift in East Timor. The collision history of the Banda arc is also significant because the obliquity of the collision provides a unique insight into the temporal evolution of the orogen through trading space for time along strike. The westward propagation of the orogen (110 km/m.y.) provides a way to simultaneously observe this active arc-continent collision at various stages of development. This last summer Sarah Johnston (graduate student) and I undertook a six-week field season in East Timor to collect structural data along a roughly N-S transect across the island of Timor in the country of East Timor. Sarah is in the process of compiling her preliminary mapping with pre-existing published and unpublished data of collaborators into a comprehensive GIS database. This database alone will be an important contribution to the current understanding of East Timor geology. As the map is being compiled, Sarah will construct an orogen-scale balanced cross section along the transect line. When finished, She will be able to use the section to estimate the amount of shortening and thickening for this location, thus producing an estimate of thickening-induced uplift. The construction of the section will also pinpoint geographic areas in need of more research and data collection for future work. Two-Year Bibliography Refereed articles: McQuarrie, N., Crustal-scale geometry of Zagros fold-thrust belt, Iran. Journal of Structural Geology, v.26, p. 519-535, 2004. McQuarrie, N., Horton, B.K., Zandt, G., Beck, S., and DeCelles, P.G., The lithospheric evolution of the central Andean Plateau: Tectonophysics, v. 399, p. 15-37, 2005. McQuarrie, N. and Wernicke, B.P., An Animated Tectonic Reconstruction of Southwestern North America since 36 MA: Geosphere, v. 1, p 147-172. doi: 10.1130/GES00016.1, 2005. 4-D Evolution of arc-continent collision in East Timor: The island of Timor in southeast Asia formed and is actively growing by the processes of island arc collision with a continental margin. Collision of the Indonesian volcanic islands (the Banda arc) with the Australian continental margin caused the growth and emergence of Timor, Rote, Savu and Sumba islands in the Banda forearc. In the mountainous region of East Timor, maximum elevations reach ~ 3000 m. Preserved in these mountains are: 1) Flights of coral terraces that record the emergence of the islands by marking an elevation that once was at sea level, 2, Young, marine sedimentary rocks record the progressive shoaling of ocean water depths. 3) Deformed rocks sufficiently exposed to reveal their Articles in press or submitted: Lease, R.O., McQuarrie, N., Oskin, M., (in review), Dextral Shear on the Bristol-Granite Mountains Fault Zone: Successful Geologic Prediction from Kinematic Compatibility of the Eastern California shear zone: Journal of Geology. Barnes, J., Ehlers, T.A., McQuarrie, N., O’ Sullivan, P.B., (in review), Erosion, Climate and plateau growth in the central Andes, northern Bolivia: Earth and Planetary Science Letters. 14 François M. M. Morel Albert G. Blanke, Jr., Professor of Geosciences Director, Princeton Environmental Institute Director, Center in Environmental BioInorganic Chemistry Ph.D., 1971, California Institute of Technology email: [email protected] Marine phytoplankton are responsible for about half of the global primary production and for a major fraction of reverse weathering on the Earth. Some of the carbon dioxide they fix is exported to the deep sea; some of the SiO2 precipitated by diatoms and of the CaCO3 precipitated by coccolithophores is accumulated in sediments and eventually subjected to diagenesis. What physical and chemical factors control the growth and activity of phytoplankton is the overarching question addressed in my research group. Our focus is on trace metals, some of which are essential for phytoplankton growth (e.g., Fe), some are toxic (e.g., Hg), some are both (e.g., Cd). An outstanding question of oceanography is why phytoplankton precipitate hard parts: what physiological and ecological benefits diatoms obtain from their silica frustule? and coccolithophores from their calcite liths? We’ve been working on the hypothesis that the hard parts of phytoplankton are important in key extracellular enzymatic processes. We have shown that the silica frustule of diatoms is an excellent buffer for hydrogen ion that enables the rapid conversion of HCO3- to CO2 through the activity of an extracellular carbonic anhydrase enzyme, a key step in the acquisition of inorganic carbon by diatoms. We have now obtained evidence that the calcium carbonate liths of coccolithophores likewise enhance the activity of extracellular alkaline phosphatase –an enzyme that liberates orthophosphate from organic compounds. The biogeochemistry of cadmium continues to be a research focus in our group. Because of its excellent correlation with phosphate, cadmium is used as a paleotracer of nutrients in the sea. We have obtained mounting evidence from laboratory and field work that cadmium is an important micronutrient for marine phytoplankton. From our previous work, we know that Cd promotes the growth of diatoms under low zinc conditions as the result of the synthesis of a Cd-carbonic anhydrase. Cadmium thus catalyses the acquisition of inorganic carbon for photosynthesis. Having now obtained the full DNA sequence for this enzyme (the first Cd enzyme discovered) and over-expressed it in a bacterial host, we are in the process of characterizing it in collaboration with protein chemists at Pen. Our next goal is to elucidate the biochemical/physiological role of Cd in coccolithophores which we have found to accumulate unusually high 15 concentrations of this metal. The biochemical utilization of cadmium by diatoms and coccolithophores is, we believe, the key to the ocean biogeochemistry of Cd and also, perhaps, to the ecology of these dominant phytoplankton taxa. In collaboration with John Reinfelder (at Rutgers University) we have continued our work on the mechanism of inorganic carbon uptake and fixation in diatoms. By following the rates of CO2 uptake and O2 evolution in the presence of various inhibitors, we have obtained convincing data supporting our earlier (and controversial) report of unicellular C4 photosynthesis --a pathway that involves accumulation of carbon as a C4 compound prior to fixation-- in these organisms. This project, in concert with our work on Cd-carbonic anhydrase and on the physiological role of the silica frustule indicate that a particularly effective carbon acquisition system may be in part responsible for the ecological success of diatoms in the oceans. After a hiatus of several years (during which iron became the fashionable element in oceanography), we have reactivated our research on the iron physiology of marine phytoplankton. Our present foci are the mechanism of uptake of iron complexed in organic chelates or precipitated as colloidal oxides (the major form of iron in the oceans), and intracellular Fe storage. 1) Fe uptake. A considerable amount of laboratory data show that the uptake of Fe by phytoplankton is modulated by the free Fe(III) concentration in seawater. But some laboratory and field data also show that Fe uptake depends on the reduction of Fe(III)complexes by surface enzymes. We have posited a new model of Fe uptake that reconciles these results by making the uptake dependent on the Fe(II) concentration at the surface and obtained new data supporting the validity of this “Fe(II)s” model. 2) Fe storage. We have identified in the recently published genome of the marine cyanobacterium Trichodesmium two sequences with high homology to genes known to code for ferritin, the major iron storage protein in living organisms. This is the first evidence of ferritin in marine microorganisms and we are in the process of isolating and characterizing this protein to study its role in the ecology of Trichodesmium, the organism thought to be responsible for the bulk of N2 fixation in the ocean. Our continuing work on the biogeochemistry of mercury is presently focused on mercury methylation. Since methyl mercury is the species accumulated in fish via the food chain, this is a key transformation, but it has received surprisingly little attention over the past 20 years. The two questions we are trying to answer are: 1) where is methylation occurring in the ocean and by what mechanism? and 2) what controls the rate of methylation by sulfate reducing bacteria in freshwater systems? New data on the concentration of mercury in tuna caught off Hawaii show that this concentration has not changed in thirty years. Mercury in tuna thus does not respond to the increase in mercury in the atmosphere and in the surface of the oceans caused by anthropogenic inputs. We thus propose that methyl mercury in the open ocean may originate from the deep sea, perhaps from hydrothermal vents. Our biochemical work with sulfate Amyot, M., F.M.M. Morel and P. A. Ariya, Dark oxidation of dissolved and liquid elemental mercury in aquatic environments, Environ. Sci. Technol., 39(1) p. 110, 2005. Sternberg, E., D. Tang, T.-Y. Ho, C. Jeandel and F.M.M. Morel, Barium Uptake and Adsorption in Diatoms, Geochemica Acta, Vol. 69(11) 2745-2752, 2005. Kustka, A. B., Y. Shaked, A.J. Milligan, D. W. King, F.M.M. Morel, Extracellular production of superoxide by marine diatoms: Contrasting effects on iron redox chemistry and bioavailabilty. Limnol. and Oceanogr., 50(4) 1172-1180, 2005. Shaked, Y., A.B. Kustka and F.M.M. Morel, A general kinetic model for iron acquisition by eukaryotic phytoplankton. Limnol. And Oceanogr., 50(3) 872-882, 2005. reducing bacteria has shown that, contrary to what is commonly believed, the acetylCoA pathway is not necessary for Hg methylation in these organisms. We are now trying to elucidate what enzymes are actually involved in methylation and what control their activity in these organisms. Two-Year Bibliography Refereed articles: Shaked, Y., A.B. Kustka, F.M.M. Morel and Y. Erel, Simultaneous determination of iron reduction and uptake by phytoplankton, Limnol. and Oceanography: Methods, http://www.aslo. org/lomethods/free/2004/0137.pdf, Vol 2, 137-145, 2004. Reinfelder, J.R., A.J. Milligan, F.M.M. Morel, The role of the C4 pathway in carbon accumulation and fixation in a marine diatom. Plant Physiolog, Vol. 135, 2106-2111, 2004. Lalonde, J.D., M. Amyot, J. Orvoine, F.M.M. Morel, J-C. Auclair, P.A. Ariya, Photoinduced Oxidation of Hg0(aq) in the Waters from the St. Lawrence Estuary Environ. Sci. Technol., 38 (2) 508-514, 2004. Kraepiel, A.M.L., K. Keller, H.B. Chin, E.G. Malcolm, F.M.M. Morel, Response to Comment on “Sources and Variations of Mercury in Tuna” Environ. Sci. Technol., 38(14) 4048, 2004. Milligan, A. J. and F.M.M. Morel. Dynamics of silicon metabolism and silicon isotopic discrimination in a marine diatom as a function of pCO2 Limnol. Oceanogr., 49 (2), 322-329, 2004. Morel, F.M.M. and E.G. Malcolm, “The biogeochemistry of Cadmium” in Biogeochemical Cycles of Elements, Vol. 43 of Metal Ions Biological Systems; ( A. Sigel, H. sigel, and R.K.O. Sigel, eds), M. Dekker, New York, pp. 301, 2005. Sunda, W., N.M. Price, F.M.M. Morel “Trace Metal ion buffers and their use in culture studies” in Algal Culturing Techniques, R. Anderson Editor, Academic Press p. 35-63, 2005. Lane, T.W, M.A. Saito, G.N. George, I.J. Pickering, R.C. Prince, F.M.M. Morel, A cadmium enzyme from a marine diatom, Nature, Vol. 435 p. 42, 2005. Articles in press or submitted: Castruita, M., M. Saito, P.C. Schottel, L.A.Elmegreen, S. Myneni, E.I. Stiefel, and F.M.M. Morel, Overexpression and characterization of an iron storage and DNA-binding Dpsprotein from Trichodesmium erythraeum. , Applied Env. Microbiology, in press. Shaked, Y., Y. Xu, K. Leblanc and F. M. M. Morel, Zinc availability and alkaline phosphatase activity in Emiliania huxleyi: Implications for Zn-P co-limitation in the ocean Limnology and Oceanography, in press. Tang, D. and F.M.M. Morel, Distinguishing between cellular and Fe-oxide associated trace elements in phytoplankton Marine Chemistry, in press, 2005 Xu, Y., T.M. Wahlund, L. Feng, Y.Shaked, and F. M.M. Morel, A novel alkaline phosphatase in the coccolithophore Emiliania huxleyi ((Prymnesiophyceae) and its regulation by phosphorus, J. of Phycology, submitted, 2005. Park, H., B.Song, and F.M.M. Morel, Diversity of the Cadmium Containing Carbonic Anhydrase (CDCA) in Marine Diatoms and Seawater, Env. Microbiology, submitted, 2005. fate and transport of contaminants in the environment. This area of research is gaining importance, and researchers from different disciplines began conducting studies to explore these interactions in greater detail. I am interested in exploring one of these fundamental interactions, which include the evaluation of the chemical state of water in different geologic media and how this modifies the biogeochemical behavior of different inorganic and organic moieties in the natural systems. I am also interested in evaluating the chemical state(s) of important geochemical species to develop predictive patterns for explaining their macroscale behavior. A summary of my current research projects, and accomplishments in the last one year are provided below. Satish Myneni Associate Professor Ph.D., 1995, Ohio State University email: [email protected] Speciation of Aluminum and Iron in Aqueous Solutions and in Solid phases Aluminum and iron are one of the most abundant elements in the Earth’s crust and form common minerals of all soils and sediments. The oxides (Fe only) and oxyhydroxides of these elements are highly reactive towards aqueous contaminants and nutrients and play an important role in the geochemical cycling of several elements. However, several oxides and oxyhydroxides of Al3+ and Fe3+ exist in the form of amorphous and poorly crystalline precipitates and aqueous polymers, whose genesis, structure, composition and reactiv- Water is essential for the origin and survival of life on our planet and perhaps plays an important role on the existence of life on other planetary bodies as well. In several different forms, water mediates the physical and chemical interactions between various components of the Earth’s surface environment, which includes mineral oxides, biota and their byproducts, and the atmosphere. One of the challenges in environmental sciences is to gain a better understanding of interactions between these different components in nature, and to use it to predict a variety of biogeochemical processes such as elemental cycling, biological chemistry of elements, and the 16 ity are poorly understood. These metastable phases occur as nanosize particulates, and convert to crystalline phases if given enough time. The rates of transformation depend on several physico-chemical variables in the environment, and vary from a few hours to several months. My research focuses on the structural chemistry of these metastable phases, and on the influence of different environmental variables that modify their transformation. My group members, Laura Harrington and Michael Hay are participating in this investigation. We use different X-ray scattering and spectroscopy techniques to evaluate the coordination environment of Al3+ and Fe3+ in the stable and metastable phases, and vibrational spectroscopy to understand the coordination environment of bridging and terminal hydroxyls. We also use X-ray spectromicroscopy to evaluate the heterogeneity in size and composition of these phases. In collaboration with Dr. Ann Chaka at the National Institute of Standards and Technology, we are conducting quantum chemical calculations to complement the experimental investigations. The formation of different oxyhydroxides of Al3+ and 3+ Fe in the environment is influenced by the speciation of these ions in aqueous solutions. It is well understood that these ions exist as hexaqua complexes (e.g. Al(H2O)63+) in highly acidic solutions and hydroxylated species (e.g. l Al(OH)m(H2O)nl+/) at all other pH values, and exhibit least solubility at near neutral pH. The chemical behavior of these two ions in aqueous solutions and their species is primarily determined by the hydroxylation of these ions, which in turn is dictated by different aqueous chemical conditions. We built a new synchrotron experimental chamber to evaluate the electronic states of the hydroxylated species of these ions in aqueous solutions. Although Al-speciation in aqueous solutions and precipitates is well studied using NMR spectroscopy, variations in the structural environment of Al in these systems are not well understood. Our preliminary X-ray studies on aluminum indicate that Al3+ forms octahedral complex with H2O in highly acidic solutions, and converts to a tetrahedral complex with 4OH- in alkaline solutions, which are in agreement with previous NMR spectroscopy studies. However, Al3+ converts to a pentacoordinate species when it reacts with an OH- in moderately acidic solutions. Although recent theoretical studies lend support to this observation, experimental evidence is missing. Changes in the coordination of Al3+ modify its electronic state and thus its reactivity. The behavior of Fe3+ follows the chemistry of Al3+ closely. Since Fe3+ exhibits stronger interactions with sulfate among all inorganic ligands, and both of them occur together in several natural systems, our initial studies focused on Fe3+-sulfate interactions. Our infrared and X-ray spectroscopy studies of these systems provided unequivocal evidence for the occurrence of H-bonding complexes of sulfate with Fe-oxyhydroxide polymers (Myneni et al. submitted). These studies unravel the mystery of solution and solid phase speciation of Fe3+ in acidic environments (Majlan and Myneni, Environ. Sci. Technol., 2005). The current emphasis is also on the understanding of the structural environments of soluble Fe3+- polymers in aquatic and biological systems (e.g. ferritins), and their precipitates. Chemistry of Natural Organic Molecules Organic molecules are found everywhere on the surface of the Earth, and their composition, molecular structure and concentration modifies the biogeochemical processes in the environment. One of the bottlenecks in our understanding of the elemental cycles is related to the speciation of C, N, and S associated with the organic molecules, and their variation in the environment. For the past several years, my research group has been using and developing X-ray spectroscopy and spectromicroscopy methods for studying the chemistry of natural organic molecules in their pristine state (Rev. Mineral., 2002). Using these methods I am investigating the: • Functional group composition and macromolecular structure of natural organic molecules in soils and sediments, • Role of minerals in the retention and fractionation of organic molecules in the environment, • Chemistry of natural organohalogens in the environment: coordination chemistry, rates of formation in the environment and their role in various biogeo chemical reactions, and • Reactions at the microorganism-water interfaces. To investigate the biogeochemical processes involved in organic molecule halogenation in terrestrial systems and their rates in detail, we built a field station in Princeton University campus. In addition, we are monitoring the speciation of C, N, and S in organic molecules to evaluate the association of these elemental cycles with the halogen-cycle. We found several interesting results on these systems, and some of the highlights are as follows. Chemistry of natural organohalogens. While manmade organohalogens are widely distributed throughout the biosphere and are characterized by varying degrees of persistence and toxicity, natural production of organohalogen compounds is gaining recognition as a significant contributor to the organohalogen burden in the environment. With the help of my research group members, I made significant progress in understanding the chemistry of natural organohalogens in the past 3-4 years. Using X-ray spectroscopy, I directly showed that the formation of organochlorines and their speciation variations in soils are directly related to the weathering of plant material. Dr. Deshmukh (post-doctoral scholar) conducted a detailed speciation of organochlorines in the O-horizons of soils, and his studies indicated that a majority of chlorinated organic molecules in weathering plant material are associated with the soluble polyphenol fraction, but not with stable lignins, as thought by several previous investigators. Specific molecules identified in our investigation are chlorinated xanthones (probably associated with lichens), and several other aliphatic and aromatic chlorinated molecules (sources uncertain at this stage). The X-ray microscopy studies conducted by Ms. Leri (graduate student) indicated a heterogeneous distribution of organochlorines in weathering leaves, which we are attributing to the differences in organic 17 Maria S., Russell L. M., Gilles M. K., Myneni S. C. B. Organic aerosol growth mechanisms and their climate forcing implications. Science, 306: 1921-1924 2004. Wei J. Saxena A., Song B., Ward B. B., Beveridge T.J ., Myneni SCB. Elucidation of functional groups on Gram-positive and Gram-negative bacterial surfaces using infrared spectroscopy. Langmui,r 20: 11433-11442 2004. Edwards, D. C., Nielsen S. B., Jarzecki A. A., Spiro T. G., Myneni S. C. B. Experimental and theoretical vibrational spectroscopy studies of acetohydroxamic acid and desferrioxamine B in aqueous solutions: Effects of pH and iron complexation. Geochim. Cosmochim. Acta, 69: 3237-3248 2005. Edwards D. C., Myneni S. C. B. Hard and soft X-ray absorption spectroscopic investigation of aqueous Fe(III)-hydroxamate siderophore complexes J. Phys. Chem., A 109: 1024910256. 2005 Strathmann T. J., Myneni S. C. B. Effect if soil fulvic acid on nickel (II) sorption and bonding at the aqueous-boehmite (γ-AlOOH) interface. Environ. Sci. Technol., 39: 4027-4034 2005. Majzlan J., Myneni S. C. B. Speciation of iron and sulfate in acid waters: Aqueous clusters to mineral precipitates. Environ. Sci. Technol., 39: 188-194 2005. Naslund L., Edwards D. C., Wernet P., Bergmann U., Ogasawara H., Pettersson L. G. M., Myneni S. C. B., Nilsson A. X-ray absorption spectroscopy study of the hydrogen bond network in the bulk water of aqueous solutions. J. Phys. Chem., A 109: 5995-6002 2005. Li W., Seal S., Rivero C., Lopez C., Richardson K., Pope A., Schulte A., Myneni S. C. B., Jain H., Antoine K., Miller A. C. Role of S/Se ratio in chemical bnding of As-S-Se glasses investigated by Raman, X-ray photoelectron, and extended X-ray absorption fine structure spectroscopies. J. App. Physics ,98: 053503 2005. Bluhm H., Andersson K., Araki T., Benzerara K., Brown G. E., Dynes J. J., Ghosal S., Gilles M. K., Hansed H. –Ch, Heminger J. C., Hitchcock A. P., Ketteler G., Kilcoyne A. L. D., Kneedler E., Lawrence J. R., Leppard G. G., Majzlan J., Mun B. S., Myneni S. C. B., Nilsson A., Ogasawara H., Ogletree D. F., Pecher K., Salmeron M., Shuh D. K., Tonner B., Tyliszczak T., Warwick T., Yoon T. H. (2005) Soft X-ray microscopy and spectroscopy at the molecular environmental science beamline at the Advanced Light Source. J. Electron Spectosc. Relat. Phenom., 150: 86-104 2005. molecule halogenation processes. Researches conducted by Ms. Hakala (senior) and Leri have shown that organobromines, like organochlorines, are common in terrestrial and marine environments. Since they are present at high concentrations in marine systems, we are planning detailed studies on their formation in the photic zone of ocean water, and their accumulation and dehalogenation in sediments. Although iodine is present at trace concentrations, we are finding that iodide and iodate present in soils react with naturally occurring organic molecules and form organoiodines in short time. The presence of Ca is significantly affecting the sensitivity of X-ray spectroscopy methods in detecting organoiodines in all natural samples. However, we found that the reactions of inorganic iodine with organic molecules are slow, and take about a week to reach equilibrium in laboratory microcosms. Rachel Zwillinger, a senior in my research group, conducted these investigations. Reactive Carboxylic Acids in Natural Organic Molecules. Carboxylic acid groups are one of the most important reactive groups in naturally occurring organic molecules. It has been widely assumed that a majority of these carboxylic acids are present as aromatic carboxylic acids (such as in salicylic acid). However, a combination of multidimensional NMR and infrared spectroscopy studies indicated that a majority of carboxylic groups in natural organics are associated with the aliphatic fraction, and have an electron withdrawing group on the adjacent C-atom (in the α- and β-positions). The presence of such groups makes the carboxyl group much more reactive and promotes the formation of strong complexes (chelation) with aqueous metals and mineral surfaces. This information is important in understanding the reactivity of common stable biomacromolecules and their origin in aquatic systems. In summary, my research group is developing into a diverse and interdisciplinary research group to address the fundamental biogeochemical processes in the environment. Two-Year Bibliography Articles in press or submitted: Myneni S. C. B. Applications of X-ray and infrared spectroscopy methods in studying microbe-mineral interfaces, in press. Myneni S. C. B., Waychunas G. A., Traina S. J., Brown Jr. G. E. Understanding the speciation of oxoanions in aquatic systems, Proc. Natl. Acad. Sci., in review. Bellenger J., Arnaud-Neu F., Asfari Z., Myneni S. C. B., Stiefel E. I., Kraepiel A. Complexation of oxoanions and cationic metals by the bis(catecholate) siderophore azotochelin, Inorganic Chemistry, in review. Refereed articles: Strathmann T., Myneni S. C. B., Speciation of aqueous Ni(II)Carboxylate and Ni(II)-Fulvic Acid Solutions: Combined ATR-FTIR and XAFS Analysis. Geochim. Cosmochim. Acta, 68: 3441-1458, 2004. Xue S., Leri A., Myneni S. C. B., Jaffe P. Uptake of bromide by two wetland plants (Typha latifolia and Phragmites australis (Cav.) Trin. Ex Steud). Environ. Sci. Technol.,38: 5642-5648 2004. Reina R., Leri A., Myneni S. C. B. Cl K-edge X-ray spectroscopic investigation of enzymatic formation of organochlorines in weathering plant material. Env. Sci. Technol., 38: 783-789 2004. 18 With Stephanie Gautier and Jean Virieux, both at Geosciences Azur in France, I have developed a new method to compute the finite-frequency sensitivity of arrival times and amplitudes of local seismic waves in complicated, threedimensional media. A first application, to image the seismogenic zone in the area of the Gulf of Corinth (Greece) is under way. Guust Nolet George J. Magee Professor of Geophysics and Geological Engineering Ph.D., 1976, University of Utrecht (The Netherlands) email: [email protected] Two-Year Bibliography Books Levander, A. and G. Nolet (eds.), Seismic Earth: Analysis of broadband seismograms, AGU Monograph Series, 2005. Refereed articles: Montelli, R., G. Nolet, F.A. Dahlen, G. Masters, E.R. Engdahl, S.-H. Hung, Finite-frequency tomography reveals variety of plumes in the mantle, Science, 303, 338-343, 2004. Montelli, R., G. Nolet, F.A. Dahlen, G. Masters, E.R. Engdahl, S.H. Hung, Global P and PP travel time tomography: rays vs. waves, Geophys. J. Int., 158, 637-654, 2004. Zhou, Y., F.A. Dahlen and G. Nolet, Three-dimensional sensitivity kernels for surface wave observables, Geophys. J. Int., 158, 142-168, 2004. Nolet, G. and R. Montelli, Optimum parameterization of tomographic models, Geophys. J. Int., 161, 365-372, 2005. Nolet, G., F.A. Dahlen and R. Montelli, Traveltimes and amplitudes of seismic waves: a re-assessment, in A. Levander and G. Nolet (eds.), Seismic Earth: Analysis of broadband seismograms, AGU Monograph Series, 37-48, 2005. Levander, A. and G. Nolet, Perspectives on array seismology and US Array, in A. Levander and G. Nolet (eds.), Seismic Earth: Analysis of broadband seismograms, AGU Monograph Series, 1-6, 2005. Dahlen, F.A. and G. Nolet, Comment on the paper “On sensitivity kernels for wave-equation transmission tomography” by de Hoop and van der Hilst, Geophys. J. Int., 163, 949-951, 2005. Zhou, Y., F.A. Dahlen, G. Nolet and G. Laske, Finite-frequency effects in global surface-wave tomography, Geophys. J. Int., 163, 1087-1111, 2005. With Raffaella Montelli and Tony Dahlen, we continued the exploration of the effects of finite frequency – introduced by us five years ago – into the imaging of the Earth’s interior. An investigation of long period S, ScS and SS waves led to a spectacular confirmation of the earlier results that showed a number of mantle plumes reach deep down into the lower mantle. This finding has important implications for the geodynamics of the Earth. This is probably the last time we invert data sets that exist in the pubic domain or that we obtain by collaboration with others. Since 2002, Karin Sigloch has been developing a new method based on matched filters that will allow us for the first time to measure arrival times and amplitudes of body waves from shallow earthquakes – the complicating interacting of the ghost reflections from the Earth’s surface are fully taken into account in the filter. The measurements can be done in different frequency windows, thus fully exploiting the power of finite frequency tomography, the new method of interpretation pioneered at Princeton in the past decade. Using the matched filtering method, Karin has recently been able to show that finite frequency effects are clearly visible in the arrival times and amplitudes of teleseismic P waves recorded by the RISTRA array in the western United States. She, and new graduate student Yue Tiang, have embarked upon an ambitious project to develop our own data base of amplitudes and arrival times, which will include complete dispersion information. Raffaella Montelli has left for Exxon, and we are at present cleaning up the finite-frequency tomography software that she developed, making it more general and user friendly. I have started writing a book that summarizes not only the theory of classical as well as finite-frequency tomography, but also the various methods of data analysis, model parameterization and inversion. No such book exists at present. Articles in press or submitted: Sigloch, K. and G. Nolet, Measuring finite-frequency body wave amplitudes and travel times, subm. to Geophys. J. Int., 2005. Montelli, R., G. Nolet, F.A. Dahlen and G. Masters, A catalogue of deep mantle plumes: new results from finite-frequency tomography, subm. to Geochemistry, geophysics, geosystems (G3), 2006. Montelli, R., G. Nolet and F.A. Dahlen, Comment on `Bananadoughnut kernels and mantle tomography’ by van der Hilst and de Hoop, subm. to Geophys. J. Int., 2006. Zhou, Y., G. Nolet, F.A. Dahlen and G. Laske, Global UpperMantle Structure from Finite-Frequency Surface-Wave Tomography, J. Geophys. Res., in press, 2006. 19 abiogenic or biotic origin. No instruments are currently flight ready that are capable of performing C and H isotopic analyses of methane. In a paper that has been accepted for publication by Astrobiology Journal, I outlined the possible origins of the Martian methane and what type of analyses would be required to distinguish between the different origins. The bad news is that the shuttle back to flight program is bleeding NASA’s science programs dry and the funding prospects for Mar’s related initiatives over the next several years is bleak. It’s time to seek a well endowed benefactor! Tullis C. Onstott Professor Ph.D., 1980, Princeton University email: [email protected] The South African Deep Microbiology Project The environments sampled over the past 5 years in the deep mines of South Africa have revealed new microbial phyla that have never been reported elsewhere, unusual biogeochemical phenomena that are difficult to understand and microscopic features that a frankly so bizarre that their origin is a mystery. For these reasons we’ve had great difficulty in publishing the findings of this project, but this past year has seen a confluence of efforts by the co-investigators participating in this project, which at long last had led to the acceptance for publication of numerous manuscripts describing the microbial diversity and geochemistry of the deep subsurface of South Africa. A great deal more research remains to be performed including the following: Deep Permafrost Environments and the Mars Deep Drilling Mission The past year’s IPTAI astrobiology effort has experienced some significant setbacks. Lupin Mine, a Au mine in the Canadian Arctic that was our sole access to brine situated beneath 500 meters of permafrost and rock, was closed. We were able to obtain some high quality planktonic samples prior to the closure in March and Daniel McGown has been successful in amplifying 16SrDNA from these samples. This was not a trivial undertaking given that the biodensity in these brines appears to be 100 to 1000 times less than we’ve experienced in South Africa. Despite his success, the low biodensity doesn’t bode well for obtaining complete genomic analyses of these environments using large fragment DNA cloning and sequencing. The investigators involved in research at Lupin will be gathering in January ’06 to share their results and plan publications based on the data in hand. The lead IPTAI investigator, Prof. Pratt of Indiana University, and I prepared a proposal to the NAI to support drilling into the permafrost at another Au mine further north called Ulu. This proposal went through two reviews and now it appears to be funded pending quotation from the drilling contractor and developments at Ulu for this coming summer. This campaign will be the first of several designed to develop the technology required for 1) locating subsurface brines beneath deep permafrost on Mars, 2) retrieving samples of permafrost and brine with little organic or microbial contamination, 3) performing life detection experiments on these same samples in the field or in the borehole and 4) determining how sensitive the organic and inorganic constituents are to the thermal histories that Martian samples will be subjected to upon their return from Mars be robotic craft. It is anticipated that such a mission would take place in the 2018-2020 time frame and none of the technology required has reached flight capability as of yet. In this context we have resubmitted a proposal to NASA’s ASTID, Astrobiology Science and Technology Instrument Development, program for perfecting the means of contaminant removal on the surface of Mars by Mars rovers with Honeybee Robotics Ltd. and development of a laser spectrometer of methane isotope analyses. Our group has focused upon methane as a biomarker of Martian life since the discovery of methane in the Martian in 2004 by several investigators led to a plethora of papers speculating on its 1. The Joint Genomics Institute completed sequencing of the complete genome of the DNA of the microorganism which appears to dominate the microbial ecosystem at depths greater than 1.5 km. in South Africa. This organism represents a new genus of Firmicutes with genetic capabilities that are surprising when compared to what we thought were the characteristics of deep subsurface organisms. Now we have to agree upon a name for this organism, utilize the genomic information to try to isolate the microbe from more environmental samples, discover the function of specific genes by performing cloning experiments and complete annotation of the sequence. A manuscript to be submitted to Science is being prepared for the release of the genome. 2. Over the past year we have been installing and instrumenting boreholes at 3.7 km depth at Tau Tona mine as part of an NSF funded project to monitor earthquake seismicity and relate that activity to geochemical and microbial properties. Progress, however, has been much slower than anticipated primarily because of safety issues regarding the site. Nevertheless, the borehole for in situ monitoring of microbial and geochemical transients will be completed in January ’06 and if all goes well this will represent the deepest site in the world for long term observation of subsurface phenomena. This is truly an international effort as the ICDP has paid for the acquisition of pristine cores from the site, the German government is supporting a group from Univ. of Potsdam to investigate changes in gas chemistry and the South African NRF is supporting out colleagues from the Univ. of Free State to run the site. Having the capability for long term in situ studies will hopefully lead to an understanding of some of the mysterious relationships we’ve been observing with spot samples. 20 Articles in press or submitted: Sherwood Lollar, B., Lacrampe-Couloume, G., Slater, G.F., Ward, J., Moser, D.P., Lin, L.-H. and Onstott, T.C. Abiogenic gases support H2-based autotrophy and methanogenesis in the deep subsurface. Chem. Geol., in press, 2006. Onstott, T. C., Lin, L.-H., Davidson, M., Mislowack, B., Borcsik, M., Hall, J., Slater, G., Ward, J., Sherwood Lollar, B., Lippmann-Pipke, J., Boice, E., Pratt, L. M., Pfiffner, S. M., Moser, D. P., Gihring, T. M., Kieft, T., Phelps, T. J., van Heerden, E., Litthaur, D., DeFlaun, M., Rothmel, R., Wanger, G. and Southam, G. The origin and age of biogeochemical trends in deep fracture water of the Witwatersrand Basin, South Africa. Geomicrobiol. Jour Jour, in press Pfiffner, S. M., Cantu, J.M., Smithgall, A., Peacock, A., White, D.C., Moser, D. P., Onstott, T. C. and van Heerden, E. Phospholipid Fatty Acid Profiles and Biodensity Estimates for Water, Rock and Air Samples Recovered from Witwatersrand Basin Mines. Geomicrobiol. Jour., in press, 2006. Slater, G. F., Lippmann-Pipke, J., Reddy, C. M., Lacrampe-Couloume, G., Onstott, T.C., Sherwood Lollar, B. 14C distribution in methane and DIC in South African gold mines: Implications to timing of methanogenesis. Geomicrobiol. Jour., in press, 2006. Wanger, G., Onstott, T. C. and Southam, G. Structural and Chemical Characterization of a Natural Fracture Surface from 2.8 Kilometers Below Land Surface: Biofilms in the Deep Subsurface. Geomicrobiol. Jour., 2006. Gihring, T. M., Moser, D. P., Lin, L.-H., Davidson, M., Onstott, T. C., Morgan, L., Milleson, M., Kieft, T., Trimarco, E., Balkwill, D.L. and Dollhopf, M. The distribution of microbial taxa in the subsurface water of the Kalahari Shield, South Africa. Geomicrobiol. Jour., in press, 2006. Lihung, L.-H., Gihring, T. M., Sherwood Lollar, B., Boice, E., Pratt, L. M., Lippmann-Pipke, J., Bellamy, R.E.S., Hall, J. and Onstott, T. C. Heterogeneous microbial communities associated with a 0.7 to 1.4 kmbls section of the continental crust. Geomicrobiol. Jour., in press, 2006. Moser, D. P., Gihring, T. M., Brockman, F. J., Fredrickson, J. K., Balkwill, D. L., Dollhopf, M. E., Sherwood-Lollar, B., Pratt, L. M., Boice, E., Southam, G., Wanger, G., Baker, B. J., Pfiffner, S. M., Lin, L.-H. and Onstott, T. C. (2005) Desulfotomaculum spp. and Methanobacterium spp. Dominate 4-5 km Deep Fault. Appl. Environ. Microbiol., in press, 2006. Onstott, T. C., McGown, D., Kessler, J., Sherwood Lollar, B., Lehmann, K. K. and Clifford, S. Martian CH4: sources, flux and detection. Astrobiology Journal, in press, 2006. DeFlaun, M. F., Fredrickson, J. K,., Dong, H., Pfiffner, S. M., Onstott, T. C., Balkwill, D .L., Streger, S. H., Stackebrandt, E., Knoessen, S. and van Heerden, E. Isolation and characterization of a novel Geobacillus thermoleovorans species from an ultra-deep South African gold mine. Systematic and Applied Microbiology, in press, 2006. Lihung, L.-H., Wang, P-L, Rumble, D., Lippmann-Pipke, J., Boice, E., Pratt, L. M., Sherwood Lollar, B., Brodie, Eoin, Hazen, T., Andersen, G., DeSantis, T., Moser, D. P., Kershaw, D. and Onstott, T. C. Long term biosustainability in a high energy, low diversity crustal biotome. Science, submitted, 2006. Mac Lean, L.C.W., Pray, T.J., Onstott, T.C. and Southam, G. High-resolution structural and chemical studies of framboidal pyrite formed within a bacterial biofilm. Geology, submitted, 2006. Mailloux, B. J., Devlin, S., Fuller, M. E., Onstott, T. C., DeFlaun, M. F., Choi, K-H, Green, M., Swift, D. J.P. and McCarthy, J. The Role of Aquifer Heterogeneity on Metal Reduction in an Atlantic Coastal Plain Aquifer. App. Geochem., submitted, 2006. Mailloux B. J., Devlin S., Fuller M. E., Onstott T. C., Sigman D. M., Williams K. H., and Hubbard S. S. The fate of nitrate during stimulation of coastal plain sediments. Environmental 3. A new weirdophile? In a Pt mine in South Africa we’ve discovered a star-shaped microbe that probably represents a new phylum of Archaea. Although we returned to this mine to collect additional samples and attempted to isolate the organism in culture, we failed to find it in the new collection. This is probably because the original seep had been sealed with cement. In January ’06 we’ll try to return to see if we can obtain a sample of this organism for further study. Deep Underground Science and Engineering Laboratory (DUSEL) The NSF has selected two candidates to compete in the final stages of the DUSEL. These two sites will submit proposals to NSF in July ’06. The final winner will be selected in early ’07 for funding to be used to develop an MRI proposal that would go to Congress in ’09. As an S1 Investigator I will be coauthor of the “glossy” report on DUSEL that will be used by NSF for justification of the facility. We will be completing this document early in ’06. Given the funding trends at NSF, DOE and NASA, the DUSEL may actually represent the best candidate for supporting long term investment in the field of terrestrial subsurface microbiology. Two-Year Bibliography Refereed articles: Hall, J.A., Mailloux, B.J., Onstott, T.C., Scheibe, T.D., Fuller, M.E., Dong, H. and DeFlaun, M.F., Physical versus chemical effects on bacterial transport as determined during in situ sediment core pulse experiments, Jour. Cont. Hydrology, 76: 295-314, 2004. Lin, L-H, Slater, G. F., Sherwood Lollar, B., Lacrampe-Couloume, G. and Onsott, T. C., Yields and hydrogen isotopic compositions of radiolytic H2 and the implications for deep biosphere in continental crust. Geochim. Cosmochim. Acta, 69, 893903, 2004. Fuller M. E., Mailloux B. J., Streger S., Hall J. A., Zhang P., Vainberg S., Johnson W. P., Onstott T. C., and DeFlaun M. F. Application of a vital fluorescent staining method for simultaneous, near-real-time concentration monitoring of two bacterial strains in an Atlantic Coastal Plain aquifer in Oyster, Virginia. Applied and Environmental Microbiology, 70: 16801687, 2004. Ward, J.A., Slater, G.F., Lacrampe-Couloume, G., Lin, L.-H., Hall, J.A., Moser, D.P., Bonin , A., Bellamy, R.E.S., Onstott, T.C. and Sherwood Lollar, B., Microbial Hydrocarbon Gases in the Witwatersrand Basin, South Africa: Implications for Deep Biosphere, Geochim. Cosmochim. Acta, 68; 3239-3250, 2004. Onstott, T.C. Impact of CO2 Injections on Deep Subsurface Microbial Ecosystems and Potential Ramifications for the Surface Biosphere. In The CO2 Capture and Storage Project, Vol. II, D.C. Thomas and S.M. Benson, eds., 1207-1239, 2004. Lin, L-H, Hall, J.A., Lippmann, J., Ward, J.A., Sherwood-Lollar, B. and Onstott, T.C., Radiolytic H2 in the continental crust: Nuclear power for deep subsurface microbial communities, Geochem. Geophys. Geosys., 6: 10.1029/2004GC000907, 2005. Kieft, T.L., McCuddy, S.M, Onstott, T. C., Davidson, M., Lin, L-H, Mislowack, B., Pratt, L.M., Boice, E., Sherwood Lollar, B., Lippmann-Pipke, J., Pfiffner, S. M., Phelps, T. J., Gihring, T., Moser, D., and van Heerden, A. Geochemically Generated, Energy-Rich Substrates and Indigenous Microorganisms in Deep, Ancient Groundwater, Geomicrobiology Journal, 22:325-355, 2005. 21 of risk assessment. The “dangerous warming” project and the “negative learning” project will be the focus of my main efforts in the near future. I will also continue to supervise postdoctoral students and graduate students in efforts to include the nitrogen cycle and ice-ocean interactions in the aforementioned Earth System Model. Michael Oppenheimer (Woodrow Wilson School and Department of Geosciences) Albert G. Millbank Professor of Geosciences and International Affairs Ph.D., 1970, University of Chicago Two-Year Bibliography email: [email protected] Refereed Articles: The West Antarctic Ice Sheet and Long Term Climate Policy (with R.B. Alley). Climatic Change, 64, 1-10, 2004. Climate Change Impacts Sensitive to Path to Stabilization (with B.C. O’Neill).Proc. Nat. Acad. Sci. 101, 16411–16416, doi_10.1073_pnas.0405522101, 2004. Book Review: The Discovery of Global Warming. J. Environmental Hist., 9, 327-8, 2004. The influence of climate on in-stream removal of nitrogen (with S.D. Donner and C.J. Kucharik). Geophys. Res. Letters, 31, L20509, doi:10.1029/2004GL020477, 2004. Ice Sheets, Global Warming, and Article 2 of the UNFCCC (with R.B. Alley). Climatic Change, 68, 257-267, 2005. Global Assessment of Coral Bleaching and Required Rates of Adaptation under Climate Change (with S.D. Donner, W.J.Skirving, C.M. Little, and O. Hoegh-Guldberg). Global Change Biology, 11, 1–15, doi: 10.1111/j.13652486.2005.01073.x, 2005. Article 2 of the UNFCCC: Historical Origins, Recent Interpretations (with A. Petsonk). Climatic Change, 73, 195-226, 2005. Attribution of Regional Radiative Forcing due to Tropospheric Ozone: A Step Toward Climate Credit for Reductions in Emissions of Ozone Precursors (with V. Naik, D. Mauzerall, L. Horowitz, D. Schwarzkopf, V. Ramaswamy). J. Geophys. Res.,in press, 2005. Avoiding Dangerous Anthropogenic Interference with the Climate System (with K. Keller, M. Hall, S.-R. Kim, and D. F. Bradford). Climatic Change, 73, 227-238, 2005. Defining Dangerous Anthropogenic Interference: The Role of Science,The Limits of Science. Risk Analysis, 25, 1-9, 2005. The Potential Impacts of Sea Level Rise on the Coastal Region of New Jersey, USA (with M.P. Cooper and M.D. Beevers). Submitted to Climatic Change, 2005. The broadest frame for my research is the question of what constitutes a dangerous level of climate change. Within that framework, I have explored particular outcomes or impacts of climate change that might have important consequences for people and societies, and therefore could produce useful benchmarks for policy makers on an appropriate approach for limiting the greenhouse gas emissions that are causing warming. Specific studies have focused on the effect of warming on 1)the Antarctic and Greenland ice sheets 2) coral reef ecosystems and 3)the nitrogen biogeochemical cycle. In each case, attempts are being made to use modeling, observations, and paleo-climatic data to provides bounds on the probability of various outcomes for given levels of warming. The most important outcome has been recognition that a warming in excess of two degrees Celsius is likely to lead to outcomes that would be widely recognized as dangerous. Most recent research and future research plans My recent research has focused on the stability of the West Antarctic and Greenland ice sheets, a global assessment of coral reef ecosystems, construction of a nitrogen sub model within the Geophysical Fluid Dynamics Laboratory’s Earth System Model and the construction of new decision making models appropriate to the global warming problem,including the recognition of a new phenomenon, “negative learning”. As a lead author of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, I am spending considerable time this year on developing a comprehensive framework for evaluating the question of what constitutes dangerous levels of warming, within a context that recognizes uncertainty, learning, and the group and individual aspects Published (or submitted or in press) chapters in books: What is the Economic Value of Information about Climate Thresholds? (with K. Keller, S-R Kim, J. Baehr, and D. F. Bradford), Integrated Assessment of Human-Induced Climate Change, M. Schlesinger, ed., submitted October 14, 2004. Emissions Pathways to Avoid Dangerous Climate Change: A Transatlantic View (with C. Jaeger) in Options for Future Climate Policy: Transatlantic Perspectives, German Institute for International and Security Affairs, Berlin, 2005. 22 nents (which affects the frequency of volcanic eruptions and hence the composition of the atmosphere), is mainly responsible for the long-term global cooling. The other associated with the Milankovitch cycles, the periodic variations in sunlight. The global cooling affected the response to relatively constant Milankovitch forcing by introducing feedbacks at certain times. For example, the global cooling led to the appearance of northern glaciers around 3 Ma, bringing into play the ice-albedo feedback. (White glaciers reflect sunlight, thus promoting the growth of glaciers by depriving the Earth of heat.) This mechanism has been studied extensively in connection with the ice-ages, but many puzzles remain. One is the amplification of obliquity but not precession cycles in global ice volume. Another concerns fluctuations in equatorial sea surface temperatures, very similar to those in the bottom panel, which lead fluctuations in ice volume by several thousand years. This, and other evidence, clearly indicate that the ice-ages involve more than ice, that the tropics played a role. Equatorial sea surface temperature patterns depend on the winds and in turn influence the winds. This implies that interactions between the ocean and atmosphere amount to positive feedbacks. Their impact on the global climate is evident during El Niño episodes when the atmospheric concentration of the powerful greenhouse gas water vapor increases significantly. Sea surface temperature patterns depend critically on the subsurface thermal structure of the ocean, especially the depth of the thermocline, the interface between the shallow layer of warm surface waters and the much colder water at depth. El Niño corresponds to changes in the slope S. George H. Philander Knox Taylor Professor of Geosciences Ph.D., 1970, Harvard University email: [email protected] These geological records show that the present is an unusual moment in the recent history of our planet. Super-imposed on the global cooling that started some 50 million years (Ma) ago when polar temperatures were close to100C, are periodic oscillations that were modest in amplitude up to ~3 million years but then started to amplify, culminating in dramatic fluctuations between prolonged ice-ages that persisted for some 100,000 years, and brief, temperate interglacials. (Variations in O18 in seafloor cores, the top panel, are a measure of polar temperatures.) Our species took advantage of the current interglacial -- it started 10,000 years ago -- to advance rapidly, from the invention of farming to industrial activities that are causing a rapid rise in the atmospheric concentration of greenhouse gases. This rise, the vertical red bar in the lower panel which shows measurements from Antarctic glaciers, is occurring at a time when those concentrations are at a natural maximum. That it is also occurring in an era, the past 1 Ma, of great climate sensitivity, follows from the cause of the recurrent ice-ages: very modest, periodic variations in the distribution of sunlight because of periodic variations in orbital parameters such as the tilt of the Earth’s axis. To anticipate what will happen next it will be helpful to understand what had happened in the past. Two sets of processes determine the climate variations described above. One, associated with the drifting of conti- of the equatorial thermocline as in the sketch on the left. Changes in the spatially averaged depth of the thermocline, as in the sketch on the right, also alter sea surface temperatures, by means of entirely different (diabatic) processes that involve changes in the heat budget of the ocean. Whereas the oceanic heat gain, in low latitudes where cold 23 Two-Year Bibliography water rises to the surface, depends on oceanic factors, specifically the depth of the thermocline, the oceanic heat loss in high latitudes depends on atmospheric factors, the air temperature for example. In a state of equilibrium, heat gain balances heat loss so that a warm world, with a small loss of heat from the oceans, must have a small gain and hence a deep tropical thermocline. Atmospheric conditions in high latitudes can therefore determine the depth of the tropical thermocline, and the intensity of air-sea interactions. These connections between low and high latitudes depend on the oceanic circulation which has two main components: the deep, slow thermohaline circulation, and the shallow, rapid wind-driven circulation. Both effect a poleward transport of heat by means of meridional overturning; surface waters sink in the extra-tropics and rise back to the surface in lower latitudes. The sinking depends on the buoyancy of the water and hence on its temperature and salinity. The heat transport, and consequently the depth of the tropical thermocline, can therefore be affected by several high latitude factors that include temperature, rainfall, and the melting of snow. The global cooling that started 50 Ma ago was accompanied by a gradual elevation of the oceanic thermocline which, around 3 Ma, was so shallow that tropical air-sea interactions started influencing the global climate. Such insights, from studies of oceanic connections between low and high latitudes, are shedding light on phenomena that range from the decadal modulation of El Niño, to the perennial (rather than intermittent) El Niño conditions of the early Pliocene, to the recurrent ice-ages of the past million years. The theories help explain the geological record of past climates, which in turn provide valuable checks for computer models of future global warming. Refereed articles: Boccaletti G., R. Pacanowski, S.G. Philander and A. Fedorov The Thermal Structure of the Ocean, J. Phys. Oceanogr., 34, 888-902, 2004. Fedorov A.V., R.C. Pacanowski, S. G. Philander and G. Boccaletti: The effect of salinity on the wind-driven circulation and the thermal structure of the upper ocean, J. Phys. Oceanogr., 31, 1949-1966, 2004. Boccaletti G., R. Pacanowski, and S.G. Philander: A diabatic mechanism for decadal variability in the tropics, Dynamics of Atmospheres and Oceans, 39, 3-19, 2005. Barreiro M., S.G. Philander, R. Pacanowski, A. Fedorov: Simulations of warm tropical conditions with application to middle Pliocene atmospheres. Climate Dynamics, doi:10.1007/ s00382-005-0086-4, 2005. Other miscellaneous publications: Philander S.G. El Niño and the Uncertain Science of Global Warming. Daedalus, Journal of the American Academy of Arts and Sciences pp 105-108, Spring 2004. Philander S.G. Science in an Uncertain World, News from ICTP, Trieste, Italy, Autumn, 2004. Philander S.G. State of Fear The Day After Tomorrow, P-ROK, Vol. 1 No. 2, 2005. (P-ROK = Princeton Report on Knowledge) Articles in press or submitted: Philander S.G. Sextant to Satellite; the Education of a Landbased Oceanographer Chapter in History of Physical Oceanography - Developments since 1960. Editors M. Jochum and R. Martugudde. Publisher Springer/New York, 2006. Fedorov A., C. Ravelo, P. Dekens, M. Barreiro, R. Pacanowski, S.G. Philander: The Pliocene Paradox, Science, submitted. Fedorov A, G. Boccaletti, R. Pacanowski and S. G. Philander: The Freshening of Surface Waters in High Latitudes; Effects on the Thermohaline and Wind-driven Circulations, J. Physical Oceanography, submitted. datasets has been that location errors are typically ~1 km, a value that exceeds both the earthquake dimensions (tens of meters for magnitude 1 events) and the length scales of significant structures within fault zones. By cross-correlating the seismograms of “similar” earthquakes (those with similar locations and focal mechanisms), it is possible to determine relative arrival times with errors that are less than one-tenth the sampling rate. From such measurements I and students and post-docs working with me have relocated many thousands of microearthquakes recorded by seismic networks in California and Hawaii. In most of our study regions we have reduced errors in relative location to meters to tens of meters for events separated by tens to hundreds of meters. This increased resolution allows us to image fault-zone structures that previously were invisible, and to obtain catalogs of many thousands of events in which relative location errors are much smaller than the earthquakes themselves. For studies of earthquake interaction, which can be conducted sensibly only in a statistical sense, such large numbers are essential and cannot be obtained using standard catalogs. For the past year most of my research has been devoted to developing a theoretical understanding of earthquake nucleation, a spin-off of one of our ongoing projects designed Allan Rubin Professor Ph.D., 1988, Stanford University email: [email protected] For the past few years I have been studying earthquake physics both observationally and theoretically. The primary impetus for this work has been the advent of waveform crosscorrelation as a tool for obtaining precise relative locations of microearthquakes. Because the number of earthquakes increases exponentially with decreasing magnitude, earthquakes near the detection threshold of a given seismic network represent a potential wealth of data for both structural geologists and seismologists. A major impediment to exploiting these 24 to study the very asymmetric distribution of earthquake aftershocks in our central San Andreas fault catalog. The modern view of fault friction is that it depends upon both the fault sliding velocity and the evolving physical or chemical state of the fault surface, which together comprise the “rate” and “state” aspects of “rate-and-state” friction. Despite the fact that the standard rate-and-state equations have been around for over 20 years, their implications for earthquake nucleation on elastically-deformable faults (meaning any fault in the Earth, as opposed to small laboratory versions) have remained elusive. The interest in this topic stems from the fact that if nucleation occurred on large enough temporal and spatial scales, precursory signals could be detected and interpreted prior to damaging earthquakes. While the observational record in this regard has not been promising, there have been numerous suggestions of “nucleation events”, occurring on timescales of fractions of a second to hours, that scale with the ultimate size of the earthquake. For the first time, we have succeeded in obtaining analytic approximations for the size and timescale of earthquake nucleation that are consistent with full numerical simulations. These approximations are based on well-established principles of fracture mechanics, allowing much greater insight into the complex behaviors that result when the nonlinear friction equations operate in an elastic system. We found, for example, that under the most popular of the laws for the evolution of the fault “state”, nucleation near the base of the seismogenic zone takes the form of an expanding crack that might often be detectable using surface seismometers. Per- haps more significantly, we showed that the aspect of this law that leads to such large nucleation zones (possibly hundreds of meters across) is clearly contradicted by existing laboratory experiments. A second popular state evolution law leads to much smaller “pulses” of slip that travel in one direction only. Because all variants of these laws are strictly empirical and are certainly inadequate at some level, it seems much more important to obtain a generic understanding of, for example, the conditions under which the nucleation zone expands or contracts, rather than to just run computer simulations using the currently favored friction law. Only then can one be in a position to predict the outcome when other physics (inelastic dilation and pore pressure reduction within the fault zone; frictional heating of pore fluids, etc.) comes into play. This is where my efforts are now focused. In addition, our theoretical work has pointed to non-traditional rock friction experiments that might better distinguish between competing state evolution laws; I am currently working with Chris Marone at Penn State and Nick Beeler at the USGS to design and implement these. Two-Year Bibliography Refereed articles: Rubin, A. M., and J.-P. Ampuero, Earthquake nucleation on (aging) rate and state faults, J. Geophys. Res., 110, B11312, doi:10.1029/2005JB003686, 2005. Peng, Z., J.E. Vidale, C. Marone, and A. Rubin, Systematic variations in recurrence interval and moment of repeating aftershocks, Geophys. Res. Lett., 32 (15): Art. No. L15301 AUG 2 2005. reasons it took so long to complete (10 years) is because there was a great deal of new research we needed to do in areas that were just not adequately understood. I estimate that I published more than two-dozen papers over the past decade that grew primarily out my attempts to fill in the gaps in our understanding. The gathering of several major new data sets as part of the WOCE and JGOFS programs in the decade of the 1990’s provided a basis for a new look at the field, but much of the analysis of these data had not been done when I started writing during an earlier sabbatical. In addition, while some areas had a great deal of exciting new research that we could base our book on, no one had successfully attempted to pull all of this together into a new synthesis since Broecker and Peng’s magnum opus of 1982, Tracers in the Sea. Our ambition was to provide a modern analogue to that wonderful textbook that has served as an introduction for a whole generation of ocean biogeochemists. We will be delighted if we succeed even partially in accomplishing that goal. As a result of the exceptional efforts required to finish up the book over the last year, my journal publications dropped from a high of nine achieved in 2004 to one in 2005. However, I have eight journal articles in press or submitted that reflect the culmination of several ongoing projects that carried over from previous years, as well as reflecting my everdeepening interest in understanding the critical role of the Southern Ocean in controlling ocean biogeochemistry and its Jorge L. Sarmiento Professor Ph.D., 1978, Columbia University email: [email protected] The primary focus of my research over the past year was the completion of my textbook cum research monograph on ocean biogeochemistry (Ocean Biogeochemical Dynamics, now in press with Princeton University Press) together with my old post doc and now UCLA faculty member (soon to be ETH faculty member), Nicolas Gruber. We have reviewed the galley proofs, and the book is scheduled to come out in May. It is of course difficult to anticipate how it will be received, but there are already quite a few colleagues who have been happily using earlier versions of the book in their courses for some years. The book represents much more than just a synthesis of our present knowledge and understanding. One of the 25 carbon cycle. These new journal articles can be categorized into three broad areas: (1) ocean biogeochemical processes and modeling, (2) modeling and observational constraints on ocean and land carbon sinks for anthropogenic carbon, and (3) Southern Ocean biogeochemistry and circulation. Each of these areas is discussed briefly below, with reference to the in press and submitted papers. ferences have major consequences for the rate of CO2 uptake estimated by these models. We are developing a new ocean model in collaboration with colleagues at GFDL that we hope will provide us with an improved simulation of processes in this region. Two-Year Bibliography Books: Sarmiento, J. L., and N. Gruber, Ocean Biogeochemical Dynamics, Princeton University Press, in press. Ocean Biogeochemical Processes and Modeling: The Orr et al. (2005) Science paper, my only 2005 journal publication, discusses the impact of ocean acidification by anthropogenic carbon on the depth of the saturation horizon of aragonite, and its likely outcropping at the surface of the Southern Ocean during the middle of this century. The possible consequences of this are very disturbing. The in press and submitted articles (1) and (2) by Dunne et al. and Jin et al. present results from our latest efforts to develop new ocean biogeochemistry models. This is ongoing research aimed at model development with the goal of providing new analyses of the impact of global warming on ocean biology and the ocean carbon cycle. Article (3) (Behrenfeld et al., submitted) is a byproduct of a parallel effort to develop empirically based ocean ecosystem models based on a new analysis of satellite color observations. Refereed articles: Doney, S. C., K. Lindsay, K. Caldeira, J.-M. Campin, H. Drange, J.-C. Dutay, M. Follows, Y. Gao, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, G. Madec, E. Maier-Reimer, J.C. Marshall, R.J. Matear, P. Monfray, A. Mouchet, R. Najjar, J.C. Orr, G.-K. Plattner, J. Sarmiento, R. Schlitzer, R. Slater, I.J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool, 2004. Evaluating global ocean carbon models: The importance of realistic physics, Global Biogeochem. Cycles, 18, GB3017, doi:10.1029/2003GB002150. Edmonds, J., F. Joos, N. Nakicenovic, R. G. Richels, and J. L. Sarmiento, Scenarios, targets, gaps, and costs. In: The Global Carbon Cycle, ed. C. B. Field and M. R. Raupach, Island Press, Washington, D.C., pp. 77-102. 2004. Gnanadesikan, A., J. P. Dunne, R. M. Key, K. Matsumoto, J. L. Sarmiento, R. D. Slater, and P, S. Swathi, Oceanic ventilation and biogeochemical cycling: Understanding the physical mechanisms that produce realistic distributions of tracers and productivity. Global Biogeochem. Cycles, 18, GB4010, doi:10.1029/2003GB002097, 2004. Greenblatt, J. B., and J. L. Sarmiento, Variability and climate feedback mechanisms in ocean uptake of CO2. In: The Global Carbon Cycle, ed. C. B. Field and M. R. Raupach, Island Press, Washington, D.C., pp. 257-275, 2004. Marinov, I., and J. L. Sarmiento, The role of the oceans in the global carbon cycle: An overview. In: The Ocean Carbon Cycle and Climate, ed. M. Follows and T. Oguz, NATO ASI, Ankara, Turkey, Kluwer Academic Publishers, pp. 251-295, 2004. Matsumoto, K., J.L. Sarmiento, R.M. Key, O. Aumont, J.L. Bullister, K. Caldeira, J.-M. Campin, S.C. Doney, H. Drange, J.-C. Dutay, M. Follows, Y. Gao, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, K. Lindsay, E. Maier-Reimer, J.C. Marshall, R.J. Matear, P. Monfray, A. Mouchet, R. Najjar, G.-K. Plattner, R. Schlitzer, R. Slater, P.S. Swathi, I.J. Totterdell, M.-F. Weirig, Y. Yamanaka, A. Yool, J.C. Orr, Evaluation of ocean carbon cycle models with data-based metrics. Geophys. Res. Lett., 31, L07303, doi:10.1029/2003GL018970, 2004. Mignone, B. K., J. L. Sarmiento, R. D. Slater, and A. Gnanadesikan, Sensitivity of sequestration efficiency to mixing processes in the global ocean. Energy, 29: 1467-1478, 2004. Sarmiento, J. L., N. Gruber, M. A. Brzezinski, and J. P. Dunne, High latitude controls of the global nutricline and low latitude biological productivity. Nature, 427: 56-60, 2004a. Sarmiento, J. L., R. Slater, R. Barber, L. Bopp, S. C. Doney, A. C. Hirst, J. Kleypas, R. Matear, U. Mikolajewicz, P. Monfray, V. Soldatov, S. A. Spall, and R. Stouffer, Response of ocean ecosystems to climate warming. Global Biogeochem . Cycles, 18, GB3003, doi:1029/2003GB002134, 2004b. Orr, J. C., V. J. Fabry, O. Aumont, L. Bopp, S. C. Doney, R. M. Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R. M. Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. Mouchet, R. G. Najjar, G.-K.Plattner, K. B. Rodgers, C. L. Sabine, J. L. Sarmiento, R. Schlitzer, R. D. Slater, I. J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool, Anthropogenic ocean acidification over the 21st century and Modeling and Observational Constraints on Carbon Sinks: A major research directions that my group has taken in the past years is estimation of the magnitude, spatial distribution, and temporal variability of carbon sources and sinks by inverse modeling of atmospheric and oceanic CO2 observations and by evaluation of models with the major new data sets that were gathered by the global surveys of the past decade. This work culminated during previous years in several papers that converged on an estimate for the oceanic carbon sink of 2.0 ± 0.3 Pg C yr—1 for the 1990’s. In a series of new papers (references (4) to (6) by Fletcher et al., and Jacobson et al, a and b) my group has explored the implications of this oceanic constraint for our estimates of land carbon sources and sinks. The submitted papers by Jacobson et al., a and b suggest that the large anthropogenic carbon sink postulated to exist in tropical rain forests is probably a chimera. The absence of this CO2 fertilization sink has major negative implications for the future growth rate of atmospheric CO2 – mitigation will be much more difficult than had been previously been thought. Southern Ocean Circulation and Biogeochemistry: Reference (7) (Marinov et al., submitted) demonstrates that there is a clear separation in the Southern Ocean between regions that control the air-sea balance of CO2 (confined primarily to high latitude regions of deep-water formation), and regions that control the return of nutrients from the deep ocean to the surface (lower latitude areas where Subantarctic Mode Water forms; see Sarmiento et al.,, 2004a). In Mignone et al., in press (reference (9)), we show that major differences in the representation of Southern Ocean circulation previously identified and analyzed by Matsumoto et al. (2004) can be explained as resulting from differences in the representation of wind forcing and mixing in the ocean models. These dif26 its impact on marine calcifying organisms. Nature, 437: 681686, 2005. Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide: I. Methods and global-scale fluxes, Global Biogeochem Cycles, submitted. Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide: II. Regional results, Global Biogeochem Cycles, submitted. Marinov, I. A. Gnanadesikan, J. R. Toggweiler, and J. L. Sarmiento, The Southern Ocean biogeochemical divide, Nature, submitted. Mignone, B. K., A. Gnanadesikan, J. L. Sarmiento, R. D. Slater, Central role of southern hemisphere winds and eddies in modulating the oceanic uptake of anthropogenic carbon, Geophys. Res. Lett., in press. Articles in press or submitted: Dunne, J. P., R. A. Armstrong, A. Gnanadesikan, and J. L. Sarmiento, Empirical and mechanistic models for the particle export, Global Biogeochem. Cycles, in press. Jin, X., N. Gruber, J. P. Dunne, J. L. Sarmiento, and R. A. Armstrong, Diagnosing CaCO3 and opal export and phytoplankton functional groups from global nutrient and alkalinity distributions, Global Biogeochem. Cycles, in press. Behrenfeld, M., R. O’Malley, D. A. Siegel, C. McClain, J. Sarmiento, G. Feldman, P. Falkowski, E. Boss, and A. Milligan, Climate-driven trends in contemporary ocean productivity, Science, submitted. Fletcher, S. E., N. Gruber, A. R. Jacobson, S. C. Doney, S. Dutkiewicz, M. Follows, K. Lindsay, D. Menemenlis, A. Mouchet, and J. Sarmiento, Inverse estimates of anthropogenic carbon uptake, transport, and storage by the ocean, Global Biogeochem. Cycles, in press. • What terms and rates compose the budgets of “fixed” (biologically available) N in the modern ocean, on land, and in the atmosphere? What are the sensitivities of the different inputs and outputs? How have the N budgets in these systems changed over climate cycles, and how have these changes affected the fertility of ocean and land? What has been the role of such changes in the global carbon cycle? Daniel Sigman Assistant Professor Ph.D., 1997, MIT and Woods Hole Oceanographic Institution email: [email protected] My research activities over the past year are summarized below under the following headings: (1) isotope method development, (2) laboratory studies of isotope discrimination, (3) studies in the modern ocean, (4) studies in the terrestrial biosphere, the atmosphere, and ice cores, (5) paleoceanographic studies, and (6) model studies of past ocean changes. My group’s entire body of work in these areas represents our effort to progress from the introduction of new measurements, to the development of the background information needed to make those measurements useful, to their application to important questions, and finally to a quantitative consideration of the findings in a broader environmental context. The citations below refer to manuscripts listed in the publications section of the annual review form. My group members and I are focused on two distinct but complementary research goals. First, we use of the isotopic composition of dissolved nitrogen species (such as nitrate (NO3-) and dissolved organic nitrogen) to provide integrative constraints on nitrogen cycle processes in modern environments, mostly in the ocean but also in terrestrial systems and the atmosphere. Second, we treat the past, as recorded in marine sediments and glacial ice, as an archive of natural experiments from which the underlying controls on the physical and biogeochemical fluxes of the environment can be determined; we study the past N cycle both in its own right and as an indicator of broader environmental change. A unifying goal of all of this work is to understand the role of plant nutrients in the interaction between life and the environment. Two sets of questions, focused on the ocean, have most centrally motivated our studies: Isotope method development In 2005, building on my group’s previously developed methods for isotopic analysis of nitrate, graduate student Angela Knapp published the first method for the 15N/14N analysis of bulk dissolved organic matter in seawater, a major N pool in the ocean that had not previously been characterized isotopically [Knapp et al., 2005]. In turn, on the basis of this work, a collaboration among Moritz Lehmann, Ben Houlton, and Masha Prokopenko has resulted in the development of a highsensitivity method for measuring the 15N/14N of dissolved ammonium (NH4+), as described in Houlton’s 2005 Ph.D. dissertation. Also building upon Knapp’s dissolved organic N method, Becky Robinson and Brigitte Brunelle have established, improved, and tested a new technique for the 15N/14N of diatom microfossil-bound N, for paleoclimate studies [Robinson et al., 2005, Brunelle et al., in review]. Finally, Julie Granger has developed a versatile method for the removal of • The polar oceans are special domains in the ocean where the “major nutrients” nitrogen (N) and phosphorus (P) are not completely consumed by algal growth. What factors control the physical conditions and nutrient status of the polar surface ocean? Over the ice age/interglacial cycles of the last 3 million years, how have the characteristics of the polar ocean affected other regions of the ocean, atmospheric carbon dioxide, and climate? 27 nitrite (NO2-) from aqueous samples to prevent this species from contaminating the isotopic analysis of nitrate [Granger et al., in review]. This method is particularly relevant to Granger’s culture studies of denitrifying bacteria (see below), in which there were large accumulations of nitrite. budget for the surface ocean at the Bermuda Atlantic Timeseries Station (BATS), indicating that N2 fixation accounts for <10% of the N supply at this site and reopening the question of the N source for the large summertime drawdown in CO2 at BATS. Nitrate N and O isotope data are also contributing to our understanding of fixed N loss from the ocean. In 2005, Moritz Lehmann published a study of the Bering Sea in which we find that the down-slope transport of organic matter from the productive Bering shelf drives denitrification in the deep sea sediments, leading to the development of a previously observed nitrate deficit in the deep basin of the Bering Sea [Lehmann et al., 2005]. These findings suggest that sedimentary denitrification is likely at the heart of unexplained variations in the nitrate-to-phosphate ratio of deep waters, with implications for globally integrated rates of nitrate loss from the ocean. Finally, the isotopes of nitrate also represent a potentially powerful constraint on the internal cycling of fixed N in the ocean, with implications for ocean circulation and the carbon cycle. My strongest interest in this regard is in the supply, transport, and consumption of nitrate in regions of the polar ocean, the Southern Ocean in particular. Combined concentration and isotope data, interpreted with a numerical model, allowed Peter DiFiore to quantify the different physical mechanisms of nitrate supply, the rate of biological export production, and the isotope effect of nitrate assimilation in the Subantarctic Zone of the Southern Ocean [DiFiore et al., in review]. These studies of the modern polar ocean complement our lab studies of algal physiology and our paleoceanographic studies. Laboratory studies of isotope discrimination The utility of isotopic distributions in the environment is premised on knowledge of the magnitudes of isotope discrimination by individual biogeochemical reactions, which is most often gained through lab studies of cultured organisms. Julie Granger’s focus is on the isotope effects of nitrateconsuming processes, in particular, nitrate assimilation by photosynthetic organisms (central to studies of nutrient supply and uptake in the surface ocean) and denitrification by heterotrophic bacteria (central to studies of the global ocean’s input/output budget of fixed N). In previous years, we have studied the relationship between N and O isotope fractionation during nitrate assimilation. In 2005, our investigations were extended to denitrifiers. Because we believe that nitrate reductase is the driver of isotope fractionation during both nitrate assimilation and denitrification, we had predicted that the N-to-O isotope coupling would be the same for both processes. This prediction has been borne out by Julie’s culture experiments, but one exotic denitrifier demonstrated different and unexpected behavior, which we believe relates to the several forms of nitrate reductase found in certain denitrifiers (manuscript in preparation). Studies in the modern ocean In projects carried out in various regions of the open ocean and in previously well-studied isolated basins, we are developing and applying the N and O isotope ratios of nitrate and dissolved organic N as integrative signals of spatially and temporally variable processes. Important results have begun to arise. In regions where the input of newly fixed N has been proposed to augment the subsurface nitrate pool, the 15N/14N of this nitrate converges toward the 15N/14N of newly fixed N and thus appears consistent with this process [Knapp et al., 2005]. Ongoing work described in Knapp’s Ph.D. dissertation seeks to combine the isotope data with constraints on circulation to quantify the rate of N2 fixation in the overlying surface ocean. Perhaps more surprising is the tentative evidence from our coupled nitrate 15N/14N and 18O/16O measurements for a previously unrecognized input of (low15 N/14N) newly fixed N in a region of intense nitrate loss by denitrification [Sigman et al., 2005]. With our new ability to measure the 15N/14N of dissolved organic N (DON), we have begun to study this enigmatic N pool, which has been hypothesized to be an important N source and sink for algae growing in the surface ocean as well as a form in which N can be exported from the surface ocean [Knapp et al., 2005]. In general, we have found the bulk DON pool of the tropical and subtropical surface ocean to be remarkably stable in isotopic composition, implying that this pool is not a direct participant in the rapid N cycling that is known to take place in the surface ocean. Angie Knapp’s measurements of DON completes the N isotope Studies in the terrestrial biosphere, the atmosphere, and ice cores Recent Ecology and Evolutionary Biology graduate student Ben Houlton has measured the isotopic composition of nitrate, dissolved organic N, and ammonium in cloud water, rainfall, soil extracts, soil water, and streams across a well-constrained rainfall gradient on the island of Maui, as described in his 2005 Ph.D. dissertation. The resulting N isotope budgets for these forests indicate an important and rainfall-dependent role for denitrification in tropical systems [Houlton et al., in review]. Associated with changes in the forest N budget across the rainfall gradient, we found a remarkably abrupt transition in the form of N fueling plant growth, from nitrate to ammonium with increasing rainfall. In contrast to a widely held view that plants control forest N fluxes, the Maui gradient suggests that the plants in these forests are not so much driving the N fluxes as finding a solution for their N demand that is consistent with the conditions of microbial growth. With recent Princeton Ph.D. Meredith Hastings, I have worked on the nitrate N and O isotopes in rain, snow, and ice as tracers of reactive nitrogen sources and processing in the modern and ancient atmosphere. Hastings’s downcore study in the GISP2 ice core from Greenland indicates a dramatically (~20‰) higher nitrate 15N/14N in ice from the last ice age than in the Holocene [Hastings et al., 2005]. 28 Although post-depositional artifacts cannot be ruled out for glacial-age ice, the 15N/14N data suggest a major climate-driven change in the relative contributions of different sources of atmospheric reactive N, such as may result from a reorganization of the terrestrial biosphere. While the isotopic signatures of reactive N sources and processing require better description to realize the true potential of the isotope tracers of atmospheric reactive N, our new methods are expediting progress in this field. cycles in CO2 and climate. Two-Year Bibliography Refereed articles: Hastings, M. G., E. J. Steig, and D. M. Sigman, Seasonal variations in N and O isotopes of nitrate in snow at Summit, Greenland: Implications for the study of nitrate in snow and ice cores, Journal of Geophysical Research – Atmospheres, 109, D20306, 10.1029/2004JD004991, 2004. Deutsch, C., D. M. Sigman, R. C. Thunell, N. Meckler, and G. H. Haug, Isotopic constraints on glacial/interglacial changes in the oceanic nitrogen budget, Global Biogeochemical Cycles, 18, GB4012, 10.1029/2003GB002189, 2004. Granger, J., D. M. Sigman, J. A. Needoba, and P. J. Harrison, Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton, Limnology and Oceanography, 49, 5 , 1763-1773, 2004. Robinson, R. S., B. G. Brunelle and D. M. Sigman, Revisiting nutrient utilization in the glacial Antarctic: Evidence from a new method for diatom-bound N isotopic analysis, Paleoceanography, 19, 3, PA3001, 10.1029/2003PA000996, 2004. Thunell, R. C., D. M. Sigman, F. Muller-Karger, Y. Astor and R. Varela, The nitrogen isotope dynamics of the Cariaco Basin, Venezuela, Global Biogeochemical Cycles, 18, 3, GB3001, 10.1029/2003GB002185, 2004. Lehmann, M. F., D. M. Sigman, and W. M. Berelson, Coupling the 15N/14N and 18O/16O of nitrate as a constraint on benthic nitrogen cycling, Marine Chemistry, 88, 1-20, 2004. Needoba, J. A., D. M. Sigman, P. J. Harrison, The mechanism of isotope fractionation by algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate, Journal of Phycology, 40, 517–522, 2004. Sigman, D. M., S. L. Jaccard, and G. H. Haug, Polar ocean stratification in a cold climate, Nature, 428, 59-63, 2004. Hastings, M. G., D. M. Sigman, and E. J. Steig, Glacial/interglacial changes in the isotopes of nitrate from the Greenland Ice Sheet Project 2 (GISP2) ice core, Global Biogeochemical Cycles, 19, GB4024, doi:10.1029/2005GB002502, 2005. Sigman, D. M., J. Granger, P. DiFiore, M. F. Lehmann, A. v. Geen, R. Ho, and G. Cane, Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin, Global Biogeochemical Cycles, 19, GB4022, doi:10.1029/2005GB002458, 2005. Lehmann, M. F., D. M. Sigman, D. C. McCorkle, B. G. Brunelle, S. Hoffmann, M. Kienast, G. Cane, and J. Clement, The origin of the deep Bering Sea nitrate deficit -- Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes, Global Biogeochemical Cycles, 19, GB4005, 10.1029/2005GB002508, 2005. Jaccard, S. L., Haug, G. H., Sigman, D. M., Pedersen, T. F., Thierstein, H. R., Röhl. U., Glacial/interglacial changes in Subarctic North Pacific stratification, Science, 308,10031006, 2005. Robinson, R. S., D. M. Sigman, P. J. DiFiore, M. M. Rohde, T. A. Mashiotta, and D. W. Lea, Diatom-bound 15N/14N: New support for enhanced nutrient consumption in the ice age Subantarctic, Paleoceanography, 20, PA3003, 10.1029/2004PA001114, 2005. Haug, G. H., A. Ganopolski, D. M. Sigman, A. Rosell-Mele, G. E. A. Swann, R. Tiedemann, S. L. Jaccard, J. Bollmann, M. A. Maslin, M. J. Leng, and G. Eglinton, North Pacific seasonality and the glaciation of North America 2.7 million years ago, Nature, 433, 821-825, 2005. Knapp, A. N., D. M. Sigman, and F. Lipschultz, N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic time-series study site, Global Biogeochemical Cycles, 19, GB1018, 10.1029/2004GB002320, 2005. Paleoceanographic studies Former postdoctoral researcher Rebecca Robinson and current graduate student Brigitte Brunelle have used their recently developed method for diatom microfossil-bound N isotope analysis to generate down-core records from polar ocean regions, where the nutrient status and physics of the surface layer can strongly affect atmospheric CO2. New down-core records from the Subantarctic Zone of the Southern Ocean provide evidence for more complete nutrient drawdown in the region during the last ice age [Robinson et al., 2005]. This represents some of the first evidence for naturally driven, long term iron fertilization of the ocean, in this case due to greater dust inputs to the region during the last ice age, much as had been predicted by the late John Martin. Ice age enhancement of nitrate consumption in the Subantarctic Zone may also explain observations of lower nutrient content, higher dissolved O2 content, and less denitrification in the tropical thermocline during the last ice age, with implications for climate-related changes in global ocean fertility and the N budget. In 2005, my collaborators (in particular, Gerald Haug) and I have published several papers demonstrating that the Subarctic North Pacific and the most polar Southern Ocean respond similarly to climate change, including glacial/interglacial cycles [Haug et al., 2005; Jaccard et al., 2005]. These studies and a manuscript in review by graduate student Brigitte Brunelle on the ice age Bering Sea greatly strengthen the case for a pervasive and general tendency for these polar ocean regions to undergo vertical stratification during cold climates. The reconstructed polar ocean changes have the capacity to affect atmospheric CO2 in the observed sense of its glacial/interglacial change. Model studies of past ocean changes I have recently begun to consider a physical mechanism for the apparent climate/polar stratification link mentioned above that involves the reduced sensitivity of seawater density to temperature at low temperatures: in the case of a globally colder ocean, temperature gradients become less important in polar ocean density structure, reducing their opposition to the stratifying effect of the net atmospheric deposition of fresh water on polar ocean regions. Postdoctoral researcher Agatha de Boer has used a general ocean circulation model to investigate this effect [de Boer et al., in review]. The results provide proof of concept for a significant role for whole ocean temperature change in polar ocean overturning. They also point to interactions among the polar regions of the different ocean basins that, along with the inclusion of other feedbacks, are leading us toward a more complete hypothesis for the role of polar ocean stratification in the Pleistocene 29 Articles in press or submitted: de Boer, A. M., D. M. Sigman, and J. R. Toggweiler, The effect of global ocean temperature change on deep ocean ventilation, Paleoceanography, in review. DiFiore, P. J., D. M. Sigman, T. W. Trull, A. J. Lourey, and K. L. Karsh, Nitrogen isotope constraints on Subantarctic biogeochemistry, Journal of Geophysical Research – Oceans, in review. Brunelle, B. G., D. M. Sigman, M. S. Cook, L. D. Keigwin, G. H. Haug, B. Mingram, and G. Schettler, Evidence from diatombound nitrogen isotopes for Subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes, Paleoceanography, in review. Granger, J., D. M. Sigman, M. Prokopenko, and P. D. Tortell, A method for nitrite removal in nitrate N and O isotope analysis, Limnology and Oceanography: Methods, in review. Galbraith, E. D., D. M. Sigman, R. S. Robinson, T. F. Pedersen, “Nitrogen in Past Marine Environments”, in Nitrogen in the Marine Environment (2nd edition), edited by D. A. Bronk, M. R. Mulholland, and D. G. Capone, in review. Houlton, B. Z., D. M. Sigman, and L. O. Hedin, Isotopic evidence for large gaseous nitrogen losses from tropical rainforests, Proceedings of the National Academy of Sciences, in review. ary faults. Results using this new theory indicate very weak faults in Taiwan, Japan and Niger delta. Furthermore this work shows that the upper crust is relatively strong, which raises the fundamental question of how a crust containing weak faults is able to be strong. John Suppe Blair Professor of Geology Ph.D., 1969, Yale University email: [email protected] Two-Year Bibliography Books (with J. Shaw, C. Connors, editors) Seismic Interpretation of Contractional Fault-Related Folds: an AAPG Seismic Atlas. American Association of Petroleum Geologists, 156pp, 2005. Refereed articles: San Andreas fault in southern California: Three-dimensional fault models and earthquake scenarios. Journal of Geophysical Research, v. 109, B04313, 17 pp, 2004. Essay Review of John Rodgers “The Company I Kept.” American Journal of Science, v. 304, p. 285-286, 2004. (with Erickson, S. G., and Strayer, L. M.) Numerical modeling of hinge-zone migration in fault-bend folds. . In McClay, K. ed., “Thrust Tectonics and Hydrocarbon Systems” American Association of Petroleum Geologists Memoir, 82, p. 438-452, 2004. (with L. M. Strayer and S. G. Erickson) Influence of growth strata on the evolution of fault-related folds: Distinct-element models. . In McClay, K. ed., “Thrust Tectonics and Hydrocarbon Systems” American Association of Petroleum Geologists Memoir, 82, p. 413-437, 2004. (and Chris Connors and Yikun Zhang) Shear fault-bend folding. In McClay, K. ed., “Thrust Tectonics and Hydrocarbon Systems” American Association of Petroleum Geologists Memoir, 82, p. 303-323, 2004. (with A. Ferrari, X. Wang and C. Jia) The Yakeng detachment fold, China. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds. American Association of Petroleum Geologists, p. 110-113, 2005. (with J. H. Shaw and S. C. Hook) Pitas Point anticline, California, USA. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds. American Association of Petroleum Geologists, p. 60-62, 2005. (with J. H. Shaw and C. D. Connors) Part 1: Structural Interpretation Methods. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds. American Association of Petroleum Geologists, p. 1-58, 2005. (with F. Corredor and J. H. Shaw) Shear fault-bend fold, deep water Niger Delta. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds. American Association of Petroleum Geologists, p. 87-92, 2005. (with A. Hubert-Ferrari and Jerome Van Der Woerd) Irregular earthquake cycle along the southern Tianshan, China (Aksu area). Journal of Geophysical Research, v. 110, B06402, doi:10.1029/2003JB002603, 2005. Since I am in the midst a one-year sabbatical I should be brief. I am currently Visiting Professor of Tectonics at Caltech and in the second half of the sabbatical will be at the Ludwig Maximillians University in Munich. The stay in Germany is the first part of a total of one-year of sojourns supported by an honorific award from the Alexander von Humboldt Foundation. I spent much effort in the spring as the scientific organizer of an “International Conference on Theory and Application of Fault-Related Folding in Foreland Basins” which was attended by a stellar cast of ~70 international experts and ~140 Chinese, held in Beijing 25-27 June, followed by a logistically ambitious one-week field trip for 110 people to remote areas of far western China to observe many examples of actively growing anticlines, which was the phenomenon of interest to this conference. The conference was enormously successful and is being followed by two major collections of papers; one is a Memoir of the American Association of Petroleum Geologists and the other a special section of the Journal of Geophysical Research. I am involved in many papers and with the editing. So many of my former students and friends were involved in the conference that it could be considered a Festschrift. However my main current focus is completing a major monograph on fault-related fold theory to be published by Princeton University Press. In addition I have obtained a surprising result in critical-taper wedge theory which allows one to determine absolute fault strength from wedge taper data, independent of significant assumptions about material properties. This is an important contribution to the longstanding controversy over the strength of major plate-bound30 (with Li-Fan Yue and Jih-Hao Hung) Structural geology of a classic thrust belt earthquake: the 1999 Chi-Chi earthquake Taiwan (Mw7.6). Journal of Structural Geology v, 27, 20582083, 2005. (with A. Hubert-Ferrari, Ramon Gonzalez-Mieres, X. Wang) Active folding of the landscape in the southern Tianshan, China. Journal of Geophysical Research, submitted, 2005. (with Ramon Gonzalez-Mieres) Relief and shortening in detachment folds. Journal of Structural Geology, submitted, 2005. Mass balance and thrusting in detachment folds. (In K. McClay, J. H. Shaw and J. Suppe, editors) Thrust-Related Folding, American Association of Petroleum Geologists Memoir, submitted, 2005. (with K. McClay and J. H. Shaw), editors, Thrust-Related Folding, American Association of Petroleum Geologists Memoir, (chapter manuscripts in review), 2005. Other miscellaneous publications: (with Dengfa He) Guidebook for fieldtrip in souh and north Tianshan foreland basin, Xinjiang Uygur Autonimous Region, China: International Conference on Theory and Application of Fault-Related Folding in Foreland Basins, 78 pp, 2005. Articles in press or submitted submitted: (with Kauan-Yin Lai,Yue-Gau Chen, Jih-Hao Hung and Ya-Wen Chen) Fault geometry related surface deformation of an active fault: evidence from geomorphic features and coseismic slip. Quaternary International, in press, 2005. to planktonic communities and in determining the net nitrogen budget of ecosystems. A new project on phytoplankton nitrogen dynamics now makes the link between the carbon and nitrogen cycles explicit, by investigating the potential for N assimilation to control the composition of photosynthetic planktonic assemblages. Ward lab has a web page where all of this is described. http://geoweb.princeton.edu/research/ecomicrobio/ecomicrobio.html Bess B. Ward William J. Sinclair Professor of Geosciences Ph.D., 1982 University of Washington 1. “Biocomplexity of Aquatic Microbial systems: Relating diversity of Microorganisms to Ecosystem Function” (O’Mullan, Adhitya) (http://geoweb.princeton.edu/research/ biocomplexity/index.html) 2005 was the last official year of this collaborative project, involving several other institutions, all working in Chesapeake Bay and coordinated through Princeton as the lead institution. Microbial biogeochemical cycling of the elements regulates a dynamic environment in which the cycles of different elements are linked through the physiology of microorganisms. Our present understanding of ecosystem function has been gained through physical/chemical approaches to measurement and modeling of the net transformations. These approaches necessarily rely on gross simplifications about the role and regulation of the various functional groups (guilds) involved. Recent advances in molecular microbial ecology have shown the microbial world to contain immense diversity and complexity at every level: redundancy and duplication of functional genes within a single organism; molecular diversity among functional genes that encode the same process in different organisms; large genetic diversity among different organisms apparently engaged in the same biogeochemical function within single communities; great variability in the species composition of different communities that apparently perform equally well. The goal of this project is to investigate the functional relationship between complexity in microbial communities and the physical/chemical environment at a range of biological and ecological scales. Previously, such analysis was technologically limited by the inability to assay large numbers of samples simultaneously for a large number of genes and phylotypes. Using gene array technology, we will be able to detect the distribution and differential expression of functional genes in natural systems. The gene arrays, along with My research concerns the marine and global nitrogen cycle, using molecular and immunological probes for marine bacteria and bacterial processes (especially nitrification and denitrification), and measuring the rates of N transformation processes. We have ongoing research on denitrification in several suboxic zones of the world ocean (Arabian Sea, Eastern Tropical North and South Pacific) and in Antarctica, the genes involved in nitrogen assimilation by phytoplankton, diversity of functional guilds of bacteria involved in the nitrogen cycle of aquatic systems, and the role of metals in nitrogen redox biogeochemistry. Some of the main projects are summarized explicitly below. Microbes control many of the important biogeochemical processes that occur in the oceans as well as on land. They contribute to the trace gas cycles that influence climate; they utilize and produce nutrients that are involved in eutrophication; and they are even capable of cleansing the environment by degrading a vast variety of chemical compounds, both naturally occurring and anthropogenically produced. My research focuses on the nitrogen cycle and the microorganisms involved in transformations of inorganic and organic nitrogen in the ocean and in sediment environments. This research makes use of technical approaches that range from molecular biology to stable isotope biogeochemistry. The two main bacterial groups we study are the nitrifiers, autotrophs that oxidize ammonium to nitrite and nitrate, and the denitifiers, heterotrophs that can respire nitrate in the absence of oxygen. The linked activities of these two groups can be crucial in determining the chemical form and supply of nitrogen 31 4. “Draft Level Sequencing of a Selection of Nitrifying Bacteria” (O’Mullan) and “Microbial genome sequencing; The complete genome sequence of a mini consortium of marine ammonia oxidizers” Sequencing is nearly complete for the entire genome of five ammonia-and nitrite-oxidizing bacteria. Nitrobacter hamburgensis 14X was grown in our lab and I extracted the DNA that was used for sequencing. Ward lab is the lead on the N. hamburgensensis genome and annotation is currently underway. In the NSF project, we are sequencing two additional ammonia oxidizers, including Nitrosococcus oceanus. The Moore foundation microbial genome project has agreed to sequence another N. oceanus genome, and that project is now underway. a full suite of ecosystem process measurements, are deployed along a transect that spans the eutrophic -oligotrophic gradient from the inland waters of the Chesapeake Bay out to the Sargasso Sea. Experiments and functional gene studies focus on key transformations in the carbon and nitrogen cycles (C fixation, N fixation, nitrification, denitrification, urea assimilation). The goal of these experiments is to determine how microbial species diversity affects the major energy and nutrient flows within ecosystems, and to assess the degree of stability or instability associated with changes in redundancy within guilds of microorganisms responsible for major nitrogen and carbon pathways. The field work for this project has been completed (~20 field trips/research cruises have been completed in Chesapeake Bay, the Choptank River and the Sargasso Sea). Both microarrays (using 70-bp oligomer probes) and macroarrays (using ~350 bp PCR products) derived from functional genes for ammonia monooxygenase, nitrite reductase and nitrogenase, have been developed and applied in this system. The array technology is robust and “works” for most genes. Genes encoding the essential enzymes RuBisCO (rbcL) and nitrate reductase (NR) in eukaryotic phytoplankton were used in the first successful second generation array to analyze phytoplankton communities in the English Channel. This array detected both community composition (DNA) and gene expression (mRNA) in natural assemblages and demonstrated the power of the approach. 5. “Diversity and distribution of denitrifying bacteria in relation to chemical distributions in theoxygen minimum zone of the Arabian Sea” (Jayakumar, Tuit, Rich) The Arabian Sea is one of three regions in the open ocean where significant denitrification occurs in the water column. Nitrous oxide is an intermediate in the denitrification pathway, and is also produced during aerobic nitrification at low oxygen tensions. It is very effective as a greenhouse gas, and what controls its production and release from marine systems is not well understood. Nitrous oxide accumulates in a characteristic pattern in oxygen minimum zones (OMZs), such as that found in the Arabian Sea. In previous work (Granger and Ward, 2003), we showed that denitrification by cultured bacteria in the lab could be limited by copper availability, leading to the accumulation of denitrification intermediates in the medium. We hypothesized that copper availability in OMZs might be quite low, low enough in fact to limit denitrification at the nitrous oxide reduction step, thus leading to accumulation of nitrous oxide. Copper limitation might also lead to accumulation of nitrite in denitrifying bacteria that possess the copper type nitrite reductasae, rather than the iron enzyme. Thus, if copper limitation were a fact of life in the OMZ, we might expect that the iron NiR should be more common than the copper NiR. We have now completed three major cruises in the last three years, one each to the three major oxygen minimum zones of the world ocean. Using chelators and various carbon and nutrient additions to manipulate the natural communities in trace metal clean incubations, we have shows that Carbon is probably the most important limitation in these systems, that denitrification is very Anammox (anaerobic ammonium oxidation) is a recently discovered step in thee N cycle, that performs essentially thee same role as denitrification. We have made some of the first measurements of this process in Chesapeake Bay, and in the OMZ regions of thee ocean (Jeremy Rich). Contrary to the first reports by Danish and German investigators, we find the anammox occurs in both sediments and the water column, but is not the dominant process. We hypothesize that our methods, which were designed to minimize artifacts we perceived in the original methods, may be responsible for the different conclusions. This is a very controversial area in which we are keenly involved and plan to continue working (pending proposals). 2. “What limits denitrification and bacterial production in Lake Bonney, Antarctica?” (Tuit) During the two recent field seasons, we developed and tested a series of flow cytometric assays for bacterial abundance and physiological state in samples from Lake Bonney, where denitrification appears to proceed normally in one lobe of the lake but not the other. Hypotheses about the ability of trace metals to limit denitrification in natural environments were tested on laboratory cultures and on incubation experiments in the lake. It appears that copper availability can indeed regulate denitrification but this is probably not the fundamental reason for the dysfunctional N cycle in Lake Bonney. 3. “Center for Environmental Bioinorganic Chemistry” (Jayakumar, Tuit) The two forms of dissimilatory (respiratory) nitrite reductase, the cd-NiR (nirS gene) and Cu-NiR (nirK gene), are distributed across the Bacterial and Archaeal domains in a great diversity of microorganisms. Because trace metal availability can limit denitrification in the lab, we hypothesized that metal distributions might influence the type of nir found in natural marine assemblages. The first step in addressing this hypothesis is to describe the distribution and diversity of nir genes in marine systems. One paper (Jayakumar, Francis and Ward, 2004) describes the diversity and distribution of nirS genes in the low oxygen coastal waters of the Arabian Sea in the continental shelf region of India. The sequences found here are the first reported for a water column environment, and are quite different from those previously reported from sediment environments. 32 Ward, B. B. Temporal variability in nitrification rates and related biogeochemical factors in Monterey Bay. Marine EcologyProgress Series, 292: 97-109, 2005. Allen, A. E., B. B. Ward and B. K. Song. Characterization of diatom (Bacillariophyceae) nitrate reductase genes and their detection in marine phytoplankton communities. Journal of Phycology, 41:95-104, 2005. O’Mullan, G. D. and B. B. Ward. Comparison of temporal and spatial variability of ammonia-oxidizing baceria to nitrification rates in Monterey Bay, CA. Applied and Environmental Microbiology, 71: 697-705, 2005. Casciotti, K. L. and B. B. Ward. Nitric oxide reductase (norB) genes identified in ammonia-oxidizing bacteria. FEMS Microbial Ecology, 52: 197-205, 2005. Song, B., and B. B. Ward. Genetic diversity of benzoyl coenzyme A reductase genes detected in denitfiying isolates and estuarine sediment communities. Applied and Environmental Microbiology, 71:2036-2045, 2005. 6. “Functional diversity of phytoplankton N assimilation” (Adhitya, Allen) Diatoms are an important component of marine photosynthetic assemblages, and tend to be especially important in coastal and upwelling systems. We hypothesize that their ability to utilize variable and high nitrate concentrations and to grow more rapidly on nitrate than many other phytoplankton, is partly responsible for their success. We will investigate the response of important diatom groups to changing N and light regimes in an upwelling scenario to test this hypothesis. Initial work on the key gene, nitrate reductase, was done by Andy Allen (a post doc) who found the first diatom NR gene, and by Anita Adyhitya (student), who investigated the NR gene diversity in diatoms associated with seagrass beds. This work lays the foundation for quantitative assays of diatom gene expression, which we will use to study differential success of various phytoplankton groups in response to N availability. Articles In Press Taroncher-Oldenburg, G. and B. B. Ward. Oligonucletoide microarrays for the study of microbial communities. In: DNA Analysis by Nonradioactive Probes (Ed.) Hilario, E. and Mackay, J.F., Humana Press, Totowa, NY, USA. Bronk, D. A. and B. B. Ward. Inorganic and organic nitrogen cycling in the Southern California Bight, Deep-Sea Research. Ward, B. B. and G. D. O’Mullan. Community level analysis: Genetic andbiogeochemcial approaches to investigate community composition and function inaerobic ammonia oxidation. In: Method in Enzymology. Ed: J. Leadbetter. Glatz, R. E., P. W. Lepp, B. B. Ward and C. A. Francis. Microbial diversity in the watercolumn of permanently ice-covered Lake Bonney, Antarctic, Geobiology. Two-Year Bibliography Refereed articles: Jiang, W., A. Saxena, B. Song, B. B. Ward, T. J. Beveridge, S. C. B. Myneni. Elucidation of functional groups on Gram-positive and Gram-negative bacterial surfacesusing infrared spectroscopy. Langmuir Langmuir, 20:11433-11442, 2004. Song, B., and B. B. Ward. Molecular characterization of the assimilatory nitratereductase gene and its expression in the marine green alga Dunaliella tertiolecta. Journal of Phycology, 40: 721-731, 2004. Jenkins, B. D., G. F. Steward, S. M. Short, B. B. Ward and J. P. Zehr. Fingerprinting diazotroph communities in the Chesapeake Bay by using a DNA macroarray. Applied and Environmental Microbiology, 70: 1767-1776, 2004. Steward, G. F., B. D. Jenkins, B. B. Ward and J. P. Zehr. Development and testing of a DNA macroarray to assess nitrogenase (nifH) gene diversity. Applied and Environmental Microbiology, 70: 1455-1465, 2004. Jayakumar, D. A., C. A. Francis, S. W. A. Naqvi and B. B. Ward. Diversity of nitrite reductase genes in the denitrifying water column of the coastal Arabian Sea. Aquatic Microbial Ecology, 34: 69-78, 2004. Ward, B. B., J. Granger, M. T. Maldonado, K. L. Casciotti, S. Harris and M. L. Wells. Denitrification in the hypolimnion of permanently ice-covered Lake Boney, Antarctica. Aquatic Microbial Ecology, 38: 295-307, 2005. Ward, B. B. Molecular approaches to marine microbial ecology and the marine nitrogen cycle. In: Annual Review of Earth and Planetary Science, 33:301-333, 2005. Submitted Jackson, G. A., B. B. Ward, G. D. O’Mullan, C. A. Francis, M. A. Voytek, D. Eveillard.Estimating total numbers of microbial operational taxonomic units (OTUs) using DNA sequence data, Applied and Environmental Microbiology. Ward, B. B., Nitrogen Cycling in Aquatic Environments. In: Manual ofEnvironmental Microbiology. Ward, B. B. Nitrification in marine systems. In: Nitrogen in the Marine Environment, Eds. D. G. Capone, D. A. Bronk and M. Mulholland. Adhitya, A., F. I. M. Thomas and B. B. Ward. Diversity of nitrate reductase genes from planktonic and epiphytic environments in seagrass communities, Microbial Ecology. 33 34 Princeton Geosciences 2006 35 Guyot Hall, front entrance. Princeton University Department of Geosciences Guyot Hall Princeton, NJ 08544-1003 36