The Marine carbon cycle. Carbonate chemistry Carbon pumps Sea surface pCO 2 and air-sea flux The sink for anthropogenic CO 2 Seawater Carbonate chemistry Inorganic carbon exists as several forms in sea water: Hydrated dissolved CO 2 gas.
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CO2(g) + H2O H2CO3
H2CO3 H+ + HCO3-
HCO3-H+ + CO32-
Typically, 90% of the carbon exists as bicarbonate,
9% as carbonate,
1% as dissolved CO2 and undissociated H2CO3 (usually lumped together).
[CO2(g)] = x pCO2sw = where
*pCO2air is determined by the atmospheric mixing ratio, i.e. if the mixing ratio is 370ppm and atmospheric pressure is 1 atm, pCO2air is 370 atm.
Global mean air-sea flux, calculated from pCO2 measurements
The flux is set by patterns of sea-surface pCO2sw, forced by:
Water cools and sinks
Water warms and upwells?
In high productivity regions, CO2 is taken out of the surface water by plankton growth and sinks in a particle "rain" to depth.
Soft tissueOcean biological pumps
CO2 + H2O CH2O +O2.
Ca++ + 2HCO3- H2O +CO2 + CaCO3
Bomb radiocarbon x 1020 atoms
Tropospheric bomb radiocarbon
The atmospheric bomb tests of the 50s and 60s injected a “spike” of radiocarbon into the atmosphere which was subsequently tracked into the ocean. This signal provides a good proxy for anthropogenic CO2 over decadal time scales.
Log10 number of deaths per conflict
Estimates of the global ocean sink 1990-1999
Reference Sink (Pg C yr-1)
IPCC (2001) 1.7+/- 0.5
OCMIP-2 Model 2.5+/- 0.4
(ten ocean carbon
Not very well!
Iron fertilisation -- deliberate or
pH change mediates against calcite-
Reduction in THC offset by increased
efficiency of nutrient utilisation
Other unforeseen ecosystem changes
Process Effect on CO2 uptake
Conclusions 100 years.