HR: 11:20h
AN: GC12A-05    [Abstracts]
TI: Forecasting Ocean Uptake of CO2: A Small Difference Between Large Numbers
AU: * Huebert, B J
EM: huebert@hawaii.edu
AF: University of Hawaii, Dept of Oceanography, Honolulu, HI 96822, United States
AB: It is incredible how well we know present and past carbon cycle budgets (including the ocean uptake of CO2), based on observed atmospheric CO2 time series, emission inventories, and precise isotopic and O/N measurements. But none of these can be used to forecast future oceanic CO2 uptake. Neither can paleo variations: the inhabited Earth has never experienced this much greenhouse forcing. To forecast uptake, we need to compute a small difference between large numbers: about 92 PgC into and 90 PgC out of the ocean annually. The IPCC acknowledges that these gross fluxes are uncertain to 20 percent (at best), but does not note the ramifications of this uncertainy. We show here that as little as a 3 percent change in emission and deposition fluxes (globally averaged over countless regional chemical and physical variations) could double the rate of atmospheric CO2 increase or just as easily change its sign to a net CO2 ocean emission. This is not a forecast, of course, but a simple sensitivity analysis. At the moment we cannot be certain even what the sign of the net ocean CO2 flux will be in a few decades. Most of the research done so far cannot improve on this alarming uncertainty, because past fluxes can not be extrapolated into a non-linear future. This small difference is a very large loose cannon. It is critical that vastly increased attention be given to quantifying the factors that control both exchange velocities and delta-pCO2 values. The goal should be that each factor is well enough quantified that at least the functional form of its impact on exchange fluxes can be incorporated into regionally-specific climate models. Improving exchange velocity models requires the development of instruments that can complement the current LiCor instruments at measuring CO2 fluxes via eddy covariance, with fewer (or at least different) sensitivity and noise problems. Viable options exist.
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0428 Carbon cycling (4806)
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting