Asignatura 2.07 Impacto del cambio global en los ciclos del N, P, C y metales The CARBON cycle in the 2070-2100 horizon: vulnerability of the carbon cycle in the ocean Marta Álvarez Rodríguez IMEDEA, CSIC-UIB Esporles, Mallorca Palma de Mallorca, February 2010
Ciclo global del carbono y su perturbación antropogénica +161 1.9 Land sink 5.4 1.7 Land use change 21.9 20 -220 +65 -125 +18 1.6 +100 Ciclo global del carbono Natural TIC vs anthropogenic TIC 2000 vs. 60 CANT not measured in ocean Biology assumed in steady state Preindustrial era: steady state carbon cycle in ocean, inputs= outputs 0.8 = 0.6 + 0.2 Antropocene: 1.9 CANT input
First 180 years the ocean absorbed 44% of emissions Last 20 years the ocean absorbed 36% of emissions Variability in the CANT uptake less efficiency?? 36% 43% 29% + to - 13-23% Sabine and Feely, 2005 55-26%
Semanas Escala Temporal 1 año 100-1000 años Chisholm, Nature 2000 > 106 años From Riebesell Variability in the CANT uptake less efficiency?? Bomba Biológica Bomba Física o de Solubilidad
Capacity of the ocean to uptake CANT Main buffering reaction in the ocean: H2CO3 + CO32-<-> 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 (TA-TIC) y en los sedimentos • CO32-: escalas de cientos de años • CO32- sed: varios miles de años
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 the 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. . Capacidad del océano para captar CANT Main buffering reaction in the ocean: H2CO3 + CO32-<-> 2 HCO3- DIC/pCO2 * (1/solub · Revelle) • Buffering by seawater CO32-: • CANT consumes CO32-, so reduces buffering capacity (Revelle factor) • lower Revelle => higher uptake • with increasing pCO2 atm, Rev increases • temporal scale => 300 yr
Capacidad del océano para captar CANT • 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. .
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. . Capacidad del océano para captar CANT • 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
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. . Capacidad del océano para captar CANT • Dynamics of the ocean CANT uptake by CO32-: 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.
Interacción océano-atmósfera-tierra y clima http://www.mri-jma.go.jp/Project/1-21/1-21-1/1-21-1-en.htm
Vulnerabilidad en la captura del CO2 natural & Antropogenico • 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 Vulnerabilidad en la captura del CO2 natural & Antropogenico
Vulnerabilidad en la captura del CO2 natural & Antropogenico 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
Vulnerabilidad en la captura del CO2 natural & Antropogenico 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.
vast depositions under continental shelfs and Arctic permafrost • crystalline solid of gas trapped in frozen cage of six water molecules Vulnerabilidad en la captura del CO2 natural & Antropogenico FEEDBACK ANALYSES Estimate for 20 y 100y uncertainty/ PgC PgC understanding Feedback Buffer capacity reduction ANTHROPOGENIC CO2 Chemical feedback: Positive <5 300 low/high - More stratification => reduction of exchange of surface to deep waters - MOC change? Circulation feedback: Positive 6-8 400 Med/Med NATURAL CO2 • Tª increase => less solubility • Sal decreases => more solubility / affects TA S/T (Solubility) feedback: Positive 15 150 low/ Med-high At circulation cte, - what happens to Exp Prod: controls => light nutrients, grazing.. - hard-tissue pump: decrease calcification / ballast effect Ocean biology: Positive 10-15 150 high/low negative • More stratification => • reduction upward input of TIC, • POC sedimentation aprox cte Circulation feedback: negative -20 -400 Med/Med Methane feedback: Positive 0 ??? Extrem high/low
Vulnerabilidad en la captura del CO2 natural & Antropogenico
Vulnerabilidad en la captura del CO2 natural & Antropogenico • 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
Observed changes in the CO2 air-sea fluxes Red dots: new data Grey/purple: regions with low sampling density
Observed changes in the CO2 air-sea fluxes February • New climatology – climat 2002 • Red values: higher new pCO2 • Blue values: lower new pCO2 August
Observed changes in the CO2 air-sea fluxes
Observed changes in the CO2 air-sea fluxes North Atlantic
Linear trend in sea surface pCO2, 1990 to 2006 Atmospheric pCO2 increased by 1.7 μatm year-1 4 3 pCO2increase [μatm year-1] 2 North-south divide at approx 45 oN with higher increase in the north 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 0.2 0.1 SST increase[o C year-1] 0 Large differences in SST change, explain 20% change NAO related changes? Schuster et al. (2009) DSR II, in press
Observed changes in the CO2 air-sea fluxes Southern Ocean