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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)