An improved understanding of the partitioning of carbon between the atmosphere, terrestrial biosphere, and ocean allows for more accurate predictions of future atmospheric CO2 concentrations under various fossil-fuel CO2-emission scenarios. One of the more poorly quantified relevant processes is the interannual variability in the uptake of fossil-fuel CO2 from the atmosphere by the terrestrial biosphere and ocean. Existing estimates, based on atmospheric measurements, indicate that the oceanic variability is large(1-3). Here we estimate the interannual variability in global net air-sea CO2 nux using changes in the observed wind speeds and the partial pressure of CO2 (p(co2)) in surface sea water and the overlying air. Changes in seawater P-co2 are deduced from interannual anomalies in sea surface temperature and the regionally and seasonally varying temperature-dependence of seawater P-co2, assuming that variations in sea surface temperature reflect seawater P-co2 changes caused by thermodynamics, biological processes and water mixing. The calculated interannual variability in oceanic CO2 uptake of 0.4 Ct Cyr(-1) (2 sigma) is much less than that inferred from the analysis of atmospheric measurements(1-3). Our results suggest that variable sequestration of carbon by the terrestrial biosphere is the main cause of observed year-to-year variations in the rate of atmospheric CO2 accumulation.
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