Open ocean DMS air/sea fluxes over the eastern South Pacific Ocean

C. A. Marandino (1) , W. J. de Bruyn (2) , S. D. Miller (3) , E. S. Saltzman (1)

1 ESS - Department of Earth System Science [Irvine]
2 Department of Physical Science
3 ASRC - Atmospheric Sciences Research Center

Air/sea fluxes of dimethylsulfide (DMS) were measured by eddy correlation over the Eastern South Pacific Ocean during January 2006. The cruise track extended from Manzanillo, Mexico, along 110° W, to Punta Arenas, Chile. Bulk air and surface ocean DMS levels were also measured and gas transfer coefficients (k_DMS) were computed. Air and seawater DMS measurements were made using chemical ionization mass spectrometry (API-CIMS) and a gas/liquid membrane equilibrator. Mean surface seawater DMS concentrations were 3.8±2.2 nM and atmospheric mixing ratios were 340±370 ppt. The air/sea flux of DMS was uniformly out of the ocean, with an average value of 12±15 ?mol m^?2 d^?1. Sea surface concentration and flux were highest around 15° S, in a region influenced by shelf waters and lowest around 25° S, in low chlorophyll gyre waters. The DMS gas transfer coefficient exhibited a linear wind speed-dependence over the wind speed range of 1 to 9 ms^?1. This relationship is compared with previously derived of k from DMS, CO₂, and dual tracer data from the Atlantic and Pacific Ocean, and with the NOAA/COARE gas transfer model. The model generated slope of k vs. wind speed is at the low end of those observed in previous DMS field studies.

Domaines: Océan, Atmosphère

C. A. Marandino, W. J. de Bruyn, S. D. Miller, E. S. Saltzman. Open ocean DMS air/sea fluxes over the eastern South Pacific Ocean. Atmospheric Chemistry and Physics Discussions, 2008, 8 (3), pp.12081-12114. ⟨hal-00304274⟩