Download PICES XV W1-3036 Invited The organic complexation in modeling

PICES XV
W1-3036
Invited
The organic complexation in modeling the iron geochemistry and bioavailability
Marie Boye1, Olivier Aumont2, Constant M.G. van den Berg3 and Hein J.W. de Baar4
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Laboratoire des Sciences de l’Environnement MARin, CNRS UMR 6539, Institut Universitaire Européen de la Mer, Technopole BrestIroise, Place Nicolas Copernic, 29280 Plouzané, France. E-mail: [email protected]
LODyC/IPSL/IRD, Centre IRD de Bretagne, BP 70, 29280 Plouzané, France
Department of Earth and Ocean Sciences, Nicholson Building, University of Liverpool, Liverpool, L69 3GP, United Kingdom
Royal Netherlands Institute for Sea Research (Royal-NIOZ), P.O. Box 59, Texel, 1790 AB den Burg, Netherlands
There is now compelling evidence that dissolved iron is principally complexed by organic ligands in oceanic
waters. This organic complexation is a central factor in oceanic iron cycling and playing a key role in iron
solubility and geochemistry, as well as in selective iron bioavailability. Despite this role of the physicalchemical speciation, cycling of the organic chelators in the ocean is still poorly understood. The chemistry of
iron, especially its organic complexation, is also poorly represented in the most of current biogeochemical
models. An overview of the distribution and speciation of the organic iron-chelators in the global ocean will be
presented to examine the vertical and horizontal gradients of the organic iron in relation to dissolved iron,
dominant planktonic assemblages, and circulation patterns. In situ data of the organic iron speciation will hence
be used to run the PISCES biogeochemical model to evaluate its impact on iron geochemistry and
bioavailability in the global ocean.
PICES XV
W1-3186
Oral
Modeling responses of iron enrichment in the equatorial Pacific Ocean
Fei Chai1, Lei Shi1, M-S Jiang2, Yi Chao3, Francisco Chavez4 and Richard Barber5
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School of Marine Science, 5471 Libby Hall, University of Maine, Orono, ME, 04469-5741, U.S.A. Email: [email protected]
Department of Environmental, Earth, and Ocean Sciences, University of Massachusetts Boston, Boston, MA, 02125, U.S.A.
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, U.S.A.
Monterey Bay Aquarium Research Institute, P.O. Box 628, 7700 Sandholdt Rd., Moss Landing, CA, 95039-0628, U.S.A.
Duke University, NSEES Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC, 28516, U.S.A.
Using a three-dimensional physical-biogeochemical model we have investigated the modeled responses of
diatom productivity and biogenic silica export to iron enrichment in the equatorial Pacific, and compared the
model simulation with in situ (IronEx II) iron fertilization results. In the eastern equatorial Pacific, an area of
500,000 km2 was enhanced with iron by changing the photosynthetic efficiency and silicate and nitrogen uptake
kinetics of phytoplankton in the model for a period of 20 days. The vertically integrated Chl-a and primary
production increased by about 3-fold five days after the start of the experiment, similar to that observed in the
IronEx II experiment. Diatoms contribute to the initial increase of the total phytoplankton biomass, but decrease
sharply after10 days because of mesozooplankton grazing. The modeled surface nutrients (silicate and nitrate)
and TCO2 anomaly fields, obtained from the difference between the “iron addition” and “ambient” (without
iron) concentrations, also agreed well with the IronEx II observations. The enriched patch is tracked with an
inert tracer similar to the SF6 used in the IronEx II. The modeled depth-time distribution of sinking biogenic
silica (BSi) indicates that it would take more than 30 days after iron injection to detect any significant BSi
export out of the euphotic zone. The numerical experiments demonstrate the value of ecosystem modeling for
evaluating the detailed interaction between silicon cycle and iron fertilization in the equatorial Pacific.
PICES XV
W1-2934
Oral
Influences of initial plankton conditions and mixed layer depth on the outcome of ironfertilization experiments
Masahiko Fujii1,2 and Fei Chai1
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School of Marine Sciences, 5706 Aubert Hall, University of Maine, Orono, ME, 04469-5706, U.S.A. E-mail: [email protected]
Sustainability Governance Project, Hokkaido University, N9W8, Sapporo, 060-0809, Japan
Several in situ iron-enrichment experiments have been conducted, but the response of the phytoplankton
community was different. We use a marine ecosystem model to investigate the effect of iron on phytoplankton
in response to different initial plankton conditions and mixed layer depth. Sensitivity analysis of the model
results to the mixed layer depth reveals that the modeled response to the same treatment of iron enhancement
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differed dramatically corresponding to different mixed layer depth. Magnitude of the iron-induced
biogeochemical responses in the surface water, such as maximum chlorophyll, is inversely correlated with the
mixed layer depth, similar to the observations. The significant decrease in maximum surface chlorophyll with
mixed layer depth results from the difference in diatom concentration in the mixed layer, which is determined
by vertical mixing. Sensitivity of the model to initial mesozooplankton (as grazers on diatoms) biomass shows
that the column-integrated net community production and export production are more strongly controlled by the
initial mesozooplankton biomass than by the mixed layer depth. Higher initial mesozooplankton biomass yields
high grazing pressure on diatoms, which results in no accumulation of diatom biomass. The initial diatom
biomass is also important to the outcome of iron enrichment but is not as crucial as the mixed layer depth and
the initial mesozooplankton biomass. This modeling study suggests not only mixed layer depth but also initial
biomass of diatoms and its principle grazers are crucial factors for the response of the phytoplankton community
to the iron enrichments, and should be considered in designing future iron-enrichment experiments.
PICES XV
W1-3230
Oral
A comparison of different NPZ models for the Northeast Pacific
Albert J. Hermann1, Thomas M. Powell2, Elizabeth L. Dobbins1, Sarah Hinckley3, Enrique N. Curchitser4, Dale
B. Haidvogel5 and Kenneth Coyle6
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Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, P.O. Box 357941, Seattle, WA, 98195,
U.S.A. E-mail: [email protected]
Department of Integrative Biology, U. C. Berkeley, 3060 Valley Life Sciences, Bldg. 3140, Berkeley, CA, 94720-3140, U.S.A.
Alaska Fisheries Science Center, 7600 Sand Point Way N.E., Seattle, WA, 98115, U.S.A.
Lamont-Doherty Earth Observatory of Columbia University, P.O. Box 1000, 61 Route 9W, Palisades, NY, 10964-8000, U.S.A.
Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Rd, New Brunswick, NJ, 08901-8521, U.S.A.
Institute of Marine Science, University of Alaska Fairbanks, P.O. Box 757220, Fairbanks, AK, 99775-7220, U.S.A.
As part of the synthesis phase of the Northeast Pacific US-GLOBEC program, we have begun simulating lower
trophic level (NPZ) dynamics of the Northeast Pacific between Baja California and the Bering Strait, out to
~1500 km offshore. As a first step, a “generic” NPZ model, presumed relevant to both the California Current
and the Gulf of Alaska under a single set of internal parameters for mesoplankton, was implemented on a 10-km
resolution grid (the Northeast Pacific grid; NEP) and simulated over a span of years which includes multiple El
Niños (and the 1997-1998 event in particular). The NEP model is embedded in a larger-scale circulation model
of the North Pacific. While some features of the area (e.g. upwelling-driven production off California) were
reproduced by the simple NPZ model, others features (e.g. higher production on the Gulf of Alaska shelf
relative to the basin, as evidenced by SeaWiFS data) were not well captured. These discrepancies underscore
the need for multiple size classes of phytoplankton and zooplankton, and/or the inclusion of iron as a limiting
micronutrient. To address these needs, we compare results from more complex NPZ models on the NEP grid,
including a multiple size class model initially developed for the Coastal Gulf of Alaska (CGOA-NPZ), both with
and without iron limitation. Through EOFs and other spatial analysis, we explore what is gained (and lost) by
the use of these more complex models of the Northeast Pacific, relative to the simpler NPZ model.
PICES XV
W1-3063
Poster
The importance of iron in a biogeochemical patch model of the NE Pacific iron
manipulation experiment, SERIES
Debby Ianson1, Christoph Voelker2, Kenneth L. Denman3, Eric Kunze4 and Nadja Steiner3
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Institute of Ocean Sciences, Fisheries and Oceans Canada, P.O. Box 6000, Sidney, BC, V8L 4B2, Canada
E-mail: [email protected]
Alfred Wegner Institute, Bremerhaven, Germany
Canadian Centre for Climate and Modeling Analysis, Victoria, BC, Canada
University of Victoria, Victoria, BC, Canada
We have developed a simple physical model, which is forced by using sulphurhexaflouride and CTD
observations, to emulate dilution as a function of time in the Subarctic Ecological Response to Iron Enrichment
Study (SERIES) iron manipulation experiment. Within this model we have embedded the 7-component
ecosystem model of Denman et al. (in press) that includes two size classes of phytoplankton and state variables
nitrogen, carbon and silica. Ecological parameters have been optimized using a genetic algorithm to best
reproduce observed chlorophyll observations (two size classes). The optimum parameter set varies little relative
to the one used with the same ecological model embedded in a 1-D physical model and that is able to simulate
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seasonal cycles at Station Papa. Our model results reproduce SERIES observations reasonably well, however
the diatom bloom is much more gradual in the model than it was in the natural system. We have experimented
with iron quota models and show that it is necessary to model luxury uptake of iron by diatoms to achieve both
the peak and abrupt crash of the diatom bloom.
PICES XV
W1-3146
Oral
Determination of iron solubility of Asian dust in the surface seawater
Atsushi Ooki1, Jun Nishioka2 and Tsuneo Ono1
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Hokkaido National Fisheries Research Institute, Fisheries Research Agency, 116, Katsurakoi, Kushiro, Hokkaido, 085-0802, Japan
E-mail: [email protected]
Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-Ku, Sapporo, 060-0819, Japan
Iron is an important trace nutrient for phytoplankton in the ocean. Recent studies have focused on the
relationship between iron budget and marine ecosystem response. In the open ocean, the main source of iron in
the surface layer is due to atmospheric deposition of mineral dust and/or supply from the deeper water. In the
North Pacific, the Asian Dust is the dominant source of mineral dust to the surface ocean. To determine the
amount of Asian Dust deposition and its related iron solubility in the seawater, it is essential to quantify the iron
supply from the atmosphere to the North Pacific. Wide range of iron solubility of mineral dust, from < 0.1% to
several percents reported by several recent studies, has caused large uncertainty of iron budget. The following
factors contribute to this uncertainty: 1) the experimental method has not been fully established because of the
difficulty measuring adsorption loss of iron; 2) atmospheric reaction would change the iron solubility of
mineral dust during the transport from the dust source region to the ocean; 3) anthropogenic iron, a main source
of iron in the urban air, may elevate the iron solubility of the dust like aerosol. We developed the extraction
method to resolve the adsorption loss problem. The iron solubility of Asian Dust particles collected in the loess
plateau (which is used as reference material) and the aerosol particle collected in the northern part of the
Japanese islands during the Asian Dust season were 1.6% and 1.4 - 2.4%, respectively. Atmospheric reaction of
Asian Dust particles does not change the iron solubility.
PICES XV
W1-3208
Oral
Phosphate and iron concentrations in an ocean carbon cycle model
Daisuke Tsumune1, Keith Lindsay2, Gokhan Danabasoglu2, Scott Doney3, Jun Nishioka4, Takeshi Yoshimura1,
Frank Bryan2 and Nakashiki Norikazu1
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Environmental Science Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba, 270-1194,
Japan. E-mail: [email protected]
Climate and Global Dynamics Division, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO, 80303-3000, U.S.A.
Woods Hole Oceanographic Institution, MA, 80303-3000, U.S.A.
Institute of Low temperature science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan
An ocean carbon cycle model is presented in the framework of the Community Climate System Model version 3
(CCSM3). This model is based on the Ocean Carbon Model Intercomparison Project (OCMIP-2) biotic carbon
model, modified by the addition of a prognostic equation for productivity and the inclusion of iron as a colimiting nutrient. Aeolian deposition is the sole source of iron, and scavenging of iron is parameterized based
on previous studies. The ocean general circulation model is based on CCSM3 POP with a resolution of 3.6
degree in longitude and 0.8 to 1.8 degree in latitude with 25 vertical levels. Previous studies with this model
found a number of biases in the distribution of nutrients relative to observations. In this study we investigated
the sensitivity of the simulation to the specification of the uptake ratio of phosphate and iron during production,
and to the parameterization of eddy mixing. An uptake ratio that is an increasing function of iron concentration
gave more realistic distribution than a uniform uptake ratio. A modification to the standard Gent-McWilliams
eddy mixing parameterization that more accurately treats near surface fluxes also resulted in improvements in
the carbon cycle simulation.
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PICES XV
W1-2827
Oral
Incorporating iron cycle into a lower trophic level marine ecosystem model, NEMURO
Naoki Yoshie1, Katsunari Sato2, Yasuhiro Yamanaka2,3 and Jun Nishioka4
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Biological Oceanography Section, Tohoku National Fisheries Research Institute, Fisheries Research Agency, Shinhama-cho 3-27-5,
Shiogama, 985-0001, Japan. E-mail: [email protected]
Graduate School of Environmental Science, Hokkaido University, N10W5, Kita-Ku, Sapporo, 060-0810, Japan
Ecosystem Change Research Program, Frontier Research Center for Global Change, 3173-25 Showa-machi, Kanazawa-Ku, Yokohama,
236-0001, Japan
Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-Ku, Sapporo, 060-0819, Japan
Iron is an important micronutrient for marine phytoplankton and controls primary productivity and trophic
structure of planktonic communities in HNLC regions. However iron cycle has not been explicitly included in
the lower trophic level marine ecosystem model, NEMURO (North Pacific Ecosystem Model Used for Regional
Oceanography) developed by CCCC/MODEL task team of PICES. In this study, we have explicitly introduced
iron cycle into NEMURO, to understand roles of iron in marine ecosystem and biogeochemical dynamics.
NEMURO with iron cycle includes with the following five iron compartments: (1) dissolved inorganic free iron
(Fef); (2) dissolved iron complexed with organic ligands (FeL); (3) particulate iron (Fe p); (4) particulate iron
attached on aeolian dust (FeD); and (5) iron included in biota (FeB). The model was applied to station A7
(41°30’N, 145°30’E) in the western subarctic North Pacific, where diatom blooms regularly in spring. The
model simulations showed seasonal variations of each iron compartment and successfully simulated the
temporal variations of dissolved iron observed from winter to early summer. The model results suggested the
concentration of dissolved iron in the surface water was mostly controlled by the supply of particulate iron from
the deep water associated with the winter deep mixing.
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