Effects of wind speed and gas exchange parameterizations on the air-sea CO2 fluxes in the equatorial Pacific Ocean -: art. no. C08S03

[1] During the recent GasEx-2001 cruise in the Equatorial Pacific aboard the NOAA ship Ronald H. Brown, carbon measurements were made in the region of 3 degreesS, 125 degreesW. Continuous surface water fCO(2) measurements were conducted onboard in both underway and discrete analysis modes. During the 15-day experiment, surface water fCO(2) values averaged 473 +/- 2 muatm, providing a constant condition of supersaturation and flux of CO2 from the ocean to the atmosphere. The relationship of gas transfer with wind speed developed in this study is used along with regional estimates of air-water fCO(2) differences to determine CO2 fluxes in the equatorial Pacific. The regional fCO(2) fields are estimated from algorithms developed from previous measurements collected on the Ronald H. Brown and Ka'imimoana over the past 10 years between 5 degreesN and 10 degreesS, 90 degreesW and 165 degreesE. Using the W. McGillis et al. gas transfer-wind speed relationship, we estimate an average flux of 1.5 +/- 0.4 mol C m(-2) yr(-1) for the study region, with a six-fold difference in the regional efflux of CO2 between the strong El Nino events of 1986 - 1987 and 1997 - 1998 and the La Nina events of 1996 and 1999 - 2001 (i.e., 0.1 to 0.56 Pg C yr(-1)). The combined effects of uncertainties in the gas transfer velocity and wind fields lead to average difference of 27% between the lowest and highest estimates of the CO2 flux from the region. In contrast, the uncertainties in the fCO(2)-SST relationships give an average difference of about 35% between the lowest and highest estimates of the CO2 flux.