HR: 13:55h
AN: A42D-02    [PDF]
TI: Ten Years of Robust Sources and Sinks of Atmospheric CO2 inferred from 13CO2 and pCO2 Measurements in the NOAA/CMDL Network
AU: * White, J W
EM: james.white@colorado.edu
AF: INSTAAR/Environmental Studies, Campus Box 450 University of Colorado, Boulder, CO 80309 United States
AU: Miller, J B
EM: John.B.Miller@noaa.gov
AF: NOAA/CMDL, 325 Broadway, Boulder, CO 80305 United States
AU: Tans, P P
EM: Pieter.Tans@noaa.gov
AF: NOAA/CMDL, 325 Broadway, Boulder, CO 80305 United States
AU: Conway, T J
EM: Thomas.J.Conway@noaa.gov
AF: NOAA/CMDL, 325 Broadway, Boulder, CO 80305 United States
AB: Prediction of future climate is dependent upon the trajectory of the rising concentration of carbon dioxide, which is, in turn, dependent upon the operation of both the terrestrial and oceanic components of the carbon cycle. Because the uptake of carbon in the oceans and land operates via different mechanisms, it is useful to calculate separately the uptake (or release) by each. Atmospheric measurements of CO2 concentrations and the relative carbon-13 content offer the possibility to resolve oceanic and terrestrial carbon fluxes at relatively high spatial and temporal resolution. Even though the global totals of oceanic and terrestrial uptake derived using d13C are somewhat uncertain, we will show that both the spatial and temporal patterns are robust. Since 1990, nearly 90,000 d13CO2 measurements have been made on air collected from more than 60 globally distributed sites in the NOAA/CMDL air sampling network. When combined with measurements of CO2 made on the same air, these data allow us to calculate the oceanic and terrestrial contributions to the total surface uptake of CO2 as a function of space and time. The most prominent result of our analysis is the large and sustained uptake of carbon in the temperate Northern Hemisphere (TNH), punctuated by periods of enhanced uptake centered around 1992 and 1997. The mean size of the uptake in the TNH is ~3+/-1 GTonC/yr, roughly half the size of the total fossil fuel flux to the atmosphere. The earlier period of enhanced uptake may be associated with the eruption of Mt. Pinatubo in 1991. The reasons for the enhanced terrestrial uptake in 1997 are less clear. The next result that stands out is the large release of carbon from the tropical biosphere that occurred during the 1997-1998 El Nino. The 1998 terrestrial flux in the tropics is about 2 to 3 GTon C more than the 1991-1997 mean. Coinciding with the SST transition typical of El Nino, we also estimate that tropical oceanic fluxes rose 2 by GtonC, sustained for two years. Perhaps the most interesting results derived from the atmospheric d13C data are the periods of enhanced terrestrial carbon uptake in the tropics in 1996 and the TNH in 1997. Whereas the other features of the record discussed so far have been previously addressed, these large signals have never been addressed and have no clear explanation.
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting