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 CANT input

Natural TIC vs anthropogenic TIC2000 vs. 60

CANT not measured in oceanBiology assumed in steady state

1

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

Emissions (f . f uel, cement) +156 ± 20 +117 ± 5

Ocean I nventory –90 ± 19 -37 ± 8

Net terrestrial +50 ± 28 -15 ± 9

Land-use change +82 to +162 +24 ± 12

*Resid. terrestrial sink –32 to -112 -39 ± 18

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 BiológicaBomba Biológica Bomba Física o Bomba Física o de Solubilidadde Solubilidad

Escala Escala Temporal Temporal 1 año1 año

100-1000 años100-1000 años

> 10> 1066 años años

Semanas Semanas

From Riebesell

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

Buffering by seawater CO32-:

- CANT consumes CO3 2-, so reduces buffering capacity (Revelle factor)

- lower Revelle => higher 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 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. [1995].

DIC/pCO2 * (1/solub · Revelle) Main buffering reaction in the ocean:

H2CO3 + CO32- <-> 2 HCO3

-

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

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].

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

Dynamics of the ocean CANT uptake by CO3 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. [1996].

Pulse responses:64% of pulse disappears in less than 1 yrAdditional 23% in 2 yr6% in 15 yr…Time scales reflect the renovation

time of each ocean realms.

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

Circulation feedback: Positive 6-8 400 Med/Med

Ocean biology: Positive 10-15 150 high/low negative

ANTHROPOGENIC CO2

S/T (Solubility) feedback: Positive 15 150 low/ Med-high

NATURAL CO2

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

SummarySummary

-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

August

New climatology – climat 2002

• Red values: higher new pCO2

• Blue values: lower new pCO2

Linear trend in sea surface pCO2,1990 to 2006

4

3

2

1

Atmospheric pCO2 increased by 1.7 μatm year-1

pCO

2 in

crea

se [

μat

m y

ear-1

]

Schuster et al. (2009) DSR II, in press

North-south divide at approx 45 oN

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

SS

T i

ncr

ease

[o C

yea

r-1]

Large differences in SST change, explain 20% changeNAO related changes?

Linear trend in sea surface temperature 1990 to 2006

Le Queré et al (Science, 2008)