GLOBAL AIR-SEA FLUX OF CO2 - AN ESTIMATE BASED ON MEASUREMENTS OF SEA-AIR PCO(2) DIFFERENCE

Approximately 250,000 measurements made for the pCO(2) difference betw een surface water and the marine atmosphere, Delta pCO(2), have been a ssembled for the global oceans. Observations made in the equatorial Pa cific during El Nine events have been excluded from the data set, Thes e observations are mapped on the global 4 degrees x 5 degrees grid for a single virtual calendar year (chosen arbitrarily to be 1990) repres enting a non-El Nino year. Monthly global distributions of Delta pCO(2 ) have been constructed using an interpolation method based on a later al advection-diffusion transport equation. The net flux of CO2 across the sea surface has been computed using Delta pCO(2) distributions and CO2 gas transfer coefficients across sea surface. The annual net upta ke flux of CO2 by the global oceans thus estimated ranges from 0.60 to 1.34 Gt-C.yr(-1) depending on different formulations used for wind sp eed dependence on the gas transfer coefficient, These estimates;Ire su bject to an error of up to 75% resulting from the numerical interpolat ion method used to estimate the distribution of Delta pCO(2) over the global oceans, Temperate and polar oceans of the both hemispheres are the major sinks for atmospheric CO2, whereas the equatorial oceans are the major sources for CO2. The Atlantic Ocean is the most important C O2 sink, providing about 60% of the global ocean uptake, while the Pac ific Ocean is neutral because of its equatorial source flux being bala nced by the sink flux of the temperate oceans, The Indian and Southern Oceans take up about 20% each.