Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ciclo global del carbono y su perturbación antropogénica +161 1.9 Natural TIC vs anthropogenic TIC 1.7 2000 vs. 60 +65 -125 CANT not measured in ocean Biology assumed in steady state Land sink Land use change 5.4 21.9 20 -220 +18 1.6 +100 Preindustrial era: steady state carbon cycle in ocean, inputs= outputs 0.8 = 0.6 + 0.2 Antropocene: 1.9 CANT input The Global Carbon Budget [Pg C]. Positive values represent atmospheric increase (or ocean/land sources), negative numbers represent atmospheric decrease (sinks). 1800-1979 1980-1999 Atmospheric increase 116 ± 4 65 ± 1 36% Emissions (f. fuel, cement) +156 ± 20 +117 ± 5 43% Ocean Inventory –90 ± 19 -37 ± 8 29% Net terrestrial +50 ± 28 -15 ± 9 + to - +82 to +162 +24 ± 12 Land-use change Sabine and Feely, 2005 13-23% *Resid.180 terrestrial sinkocean –32 to -112 44% of -39 ± 18 55-26% First years the absorbed emissions Last 20 years the ocean absorbed 36% of emissions Bomba Biológica Semanas Bomba Física o de Solubilidad Escala Temporal 1 año 100-1000 años > 106 años Chisholm, Nature 2000 From Riebesell Main buffering reaction in the ocean: H2CO3 + CO3 2- <-> 2 HCO3 - - aumento CO2 en atm es la fuerza termodinámica que empuja al CANT en el océano -Sin la qca del CO2 un 70% del CANT estaría en atm, no un 50% como ahora - CO32- factor limitante, está en el agua (CO32- ≈TA-TIC) y en los sedimentos - CO32-: escalas de cientos de años - CO32- sed: varios miles de años Main buffering reaction in the ocean: H2CO3 + CO32- <-> 2 HCO3 - DIC/pCO2 * (1/solub · Revelle) Buffering by seawater CO32-: - CANT consumes CO3 2-, so reduces buffering capacity (Revelle factor) - higher Revelle => lower uptake - with increasing pCO2 atm, Rev increases - temporal scale => 300 yr Libro Sarmiento & Gruber. Figure 10.2.1: (a) The global mean instantaneous change in surface ocean DIC resulting from a given change in H2CO3 concentration for the S450 and S750 scenarios in which CO2 is stabilized at 450 ppm and 750 ppm, respectively. The large reduction in this ratio through time is a measure of th reduction in the oceanic buffer capacity of surface waters. (b) The annual oceanic uptake for S450 and S750 scenarios, using either full (nonlinear) chemistry (solid lines) or simplified linear chemistry (dashed lines). The nonlinear CO2 chemistry of seawater leads to a dramatic reduction in the future oceanic uptake of CO2, with the effect becoming larger as the atmospheric perturbation increases. From Sarmiento et al. [1995]. Other possible buffering reactions in the ocean: - sea-floor carbonates - terrestrial carbonates - silicate (igneous rocks) weathering Libro Sarmiento & Gruber. Figure 10.2.2: Fractions of anthropogenic CO2 sequestered by various abiological processes plotted as a function of anthropogenic CO2 release. The approximate e-folding timescales for each process are given at the right. The fraction remaining in the atmosphere for a given timescale is the difference between 1 and the level of the cumulative curve. For example, on timescales of 4000 years, the fraction remaining in the atmosphere after equilibration is determined by the magnitude sequestered by the ocean by reaction with carbonate and sea-floor CaCO3. For an mission of 4000 Pg C, these two processes remove about 87% of the emission, leaving 13% in the atmosphere. From Archer et al. [1997]. Current ocean CANT uptake: - CANT only in the upper 1000m aprox - oceans have absorbed 30% of total emissions - after 200 yr only a small fraction of the ocean is equilibrated with the atm (about 8%) - why? - dynamics constraints to uptake capacity Time-scales for the ocean CANT uptake: - several hundreds of years: ocean - 4000 yr: carbonate rocks - 10 000 yr: land carbonates - million yr: igneous rocks on land Figure 10.2.3: Time series of instantaneous fractional contributions of four different processes to the sequestration. The four processes are ocean invasion, reaction of the anthropogenic CO2 with mineral calcium carbonates at the sea floor, reaction with calcium carbonates on land, and sequestration by silicate weathering. Note that the exact shape of the atmospheric pulse response depends on the size of the pulse because of the nonlinearity of the oceanic buffer factor. This pulse here has been calculated for a pulse size of 3000 Pg of carbon. Based on results by Archer et al. [1997]. Dynamics of the ocean CANT uptake by CO3 2-: which is the limiting step - air-sea gas exchange ORR - thermohaline circulation Pulse responses: 64% of pulse disappears in less than 1 yr Additional 23% in 2 yr 6% in 15 yr… Time scales reflect the renovation time of each ocean realms. Libro Sarmiento & Gruber. Figure 10.2.4: Effective mixed layer pulse-response functions for the box-diffusion model, the HILDA model, the 2-D model, and the Princeton general circulation model. Inset shows the pulse-response functions for the first ten years. Modified from Joos et al. [1996]. http://www.mri-jma.go.jp/Project/1-21/1-21-1/1-21-1-en.htm Carbon-climate feedback: Future climate changes associated with the buildup of greenhouse gases in the atmosphere will likely modify processes related with the carbon cycle in the atmosphere, ocean and land. These alterations will also impact or change the atmospheric composition and thus future climate => feedbacks: - positive: those accelerating climate change - negative: those decelerating climate change From Riebesell Ocean CANT uptake scales linearly with the exponential CO2 atmospheric increase => - max. potential sink for next 20 yr (without feedbacks) is 60-80 PgC - for next 100 yr, depends on the CO2 emissions How sensitive is the oceanic sink to natural and human induced changes over the next 20 – 100 yr? => risk and vulnerability assessment on carbon pools Vulnerable carbon pools, magnitude and likelihood of the release to the atmosphere of the carbon stored Vulnerability: maximum part of the total carbon stock that would be released into the atm over the time scale indicated. FEEDBACK ANALYSES Feedback ANTHROPOGENIC CO2 Chemical feedback: Estimate for 20 y 100y PgC PgC uncertainty/ understanding Buffer capacity reduction Circulation feedback: Positive <5 300 low/high - More stratification => reduction of exchange of6-8 surface 400 to deep watersMed/Med Positive - MOC change? - vast depositions under continental shelfs and-Tª Arctic increase => less solubility Positive 15 permafrost 150 low/ Med-high -crystalline solid of gas trapped in frozen - Sal decreases => more solubility / affects At circulation cte, cage of six water Positive 10-15 150molecules high/low TA More stratification => - what happens to Exp Prod: controls => light negative - reduction upward input of TIC, nutrients, grazing.. - POC sedimentation aproxMed/Med cte negative -20 -400 - hard-tissue pump: decrease calcification / Methane feedback: Positive 0 ballast effect Circulation feedback: NATURAL CO2 S/T (Solubility) feedback: Ocean biology: ??? Extrem high/low Summary -The ocean response without climate change is different from that with feedbacks - ocean uptake without feedbacks is high, several hundred PgC - ocean uptake with feedbacks reduces sink, feedbacks are mainly positive - feedbacks will increase with climate change effect, consequently more CANT will remain in the atm - vulnerability depends on different C pools, some processes are still uncertain => need for integrating and interdisciplinary research Red dots: new data Grey/purple: regions with low sampling density February New climatology – climat 2002 • Red values: higher new pCO2 • Blue values: lower new pCO2 August Linear trend in sea surface pCO2, 1990 to 2006 4 3 2 North-south divide at approx 45 oN with higher increase in the north pCO2 increase [μatm year-1] Atmospheric pCO2 increased by 1.7 μatm year-1 1 Schuster et al. (2009) DSR II, in press Linear trend in sea surface temperature 1990 to 2006 Linear trend in sea surface temperature 1970 to 1989 0.1 Large differences in SST change, explain 20% change NAO related changes? SST increase [o C year-1] 0.2 0 Schuster et al. (2009) DSR II, in press Le Queré et al (Science, 2008)