Presentation on theme: "Ciclo global del carbono +65 -125 1.7 Land use change +18 21.9 20 1.9 Land sink 1.6 +100 5.4 -220 +161 y su perturbación antropogénica Preindustrial era:"— Presentation transcript:
Ciclo global del carbono +65 -125 1.7 Land use change +18 21.9 20 1.9 Land sink 1.6 +100 5.4 -220 +161 y su perturbación antropogénica Preindustrial era: steady state carbon cycle in ocean, inputs= outputs 0.8 = 0.6 + 0.2 Antropocene: 1.9 C ANT input Natural TIC vs anthropogenic TIC 2000 vs. 60 C ANT not measured in ocean Biology assumed in steady state
First 180 years the ocean absorbed 44% of emissions Last 20 years the ocean absorbed 36% of emissions 36% 43% 29% 13-23% 55-26% + to - Sabine and Feely, 2005
Chisholm, Nature 2000 Bomba Biológica Bomba Física o de Solubilidad Escala Temporal 1 año 100-1000 años > 10 6 años Semanas From Riebesell
Main buffering reaction in the ocean: H 2 CO 3 + CO 3 2- 2 HCO 3 - - aumento CO 2 en atm es la fuerza termodinámica que empuja al C ANT en el océano -Sin la qca del CO 2 un 70% del C ANT estaría en atm, no un 50% como ahora - CO 3 2- factor limitante, está en el agua ( CO 3 2- ≈ TA-TIC) y en los sedimentos - CO 3 2- : escalas de cientos de años - CO 3 2- sed: varios miles de años
Buffering by seawater CO 3 2- : - C ANT consumes CO 3 2-, so reduces buffering capacity (Revelle factor) - higher Revelle => lower uptake - with increasing pCO 2 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 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. . DIC/pCO2 * (1/solub · Revelle) Main buffering reaction in the ocean: H 2 CO 3 + CO 3 2- 2 HCO 3 -
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. .
Current ocean C ANT uptake: - C ANT 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 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. . Time-scales for the ocean C ANT uptake: - several hundreds of years: ocean - 4000 yr: carbonate rocks - 10 000 yr: land carbonates - million yr: igneous rocks on land
Dynamics of the ocean C ANT uptake by CO 3 2- : which is the limiting step - air-sea gas exchange ORR - thermohaline circulation 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. . 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.
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
Ocean C ANT 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 Circulation feedback: Positive 6-8 400 Med/Med Ocean biology: Positive 10-15 150 high/low negative ANTHROPOGENIC CO 2 S/T (Solubility) feedback: Positive 15 150 low/ Med-high NATURAL CO 2 Chemical feedback: Positive <5 300 low/high Circulation feedback: negative -20 -400 Med/Med Methane feedback: Positive 0 ??? Extrem high/low Feedback Estimate for 20 y 100y uncertainty/ PgC PgC understanding Buffer capacity reduction - More stratification => reduction of exchange of surface to deep waters - MOC change? -Tª increase => less solubility - Sal decreases => more solubility / affects TA More stratification => - reduction upward input of TIC, - POC sedimentation aprox cte At circulation cte, - what happens to Exp Prod: controls => light nutrients, grazing.. - hard-tissue pump: decrease calcification / ballast effect - vast depositions under continental shelfs and Arctic permafrost -crystalline solid of gas trapped in frozen cage of six water molecules
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 C ANT will remain in the atm - vulnerability depends on different C pools, some processes are still uncertain => need for integrating and interdisciplinary research
Linear trend in sea surface pCO 2, 1990 to 2006 4 3 2 1 Atmospheric pCO 2 increased by 1.7 μatm year -1 pCO 2 increase [μatm year -1 ] Schuster et al. (2009) DSR II, in press North-south divide at approx 45 o N with higher increase in the north
0 0.1 0.2 Linear trend in sea surface temperature 1970 to 1989 Schuster et al. (2009) DSR II, in press SST increase [o C year -1 ] Large differences in SST change, explain 20% change NAO related changes? Linear trend in sea surface temperature 1990 to 2006