Concentrations and fluxes of dissolved biogenic gases (DMS, CH₄, CO, CO₂) in the equatorial Pacific during the SAGA 3 experiment

Abstract

The equatorial Pacific Ocean is a source of both sulfur and carbon to the atmosphere. In February and March 1990, as part of the Soviet‐American Gases and Aerosols (SAGA 3) expedition, dimethysulfide (DMS), methane (CH 4 ), carbon monoxide (CO), and carbon dioxide (CO 2 ) partial pressures were determined in both surface seawater and the overlying atmosphere of the central equatorial Pacific Ocean (15°N to 10°S, 145°W to 165°W). The partial pressures were used to calculate the net flux of these gases from the ocean to the atmosphere. The average regional DMS and CO fluxes were similar, 7.1 and 4.2 μmol/m 2 /d, respectively. The mixing ratio of CH 4 in surface seawater was close to equilibrium with the overlying atmosphere and hence the average flux was only 0.39 μmol/m 2 /d. The flux of CO 2 clearly dominated the air‐sea carbon exchange with an average regional flux of 5.4 mmol/m 2 /d.