Abstract
Dimethylsulfide (DMS) atmospheric and oceanic concentrations and eddy covariance air/sea fluxes were measured over the N. Atlantic Ocean during July 2007 from Iceland to Woods Hole, MA, USA. Seawater DMS levels north of 55°N ranged from 3 to 17 nM, with variability related to the satellite‐derived distributions of coccoliths and to a lesser extent, chlorophyll. For the most intense bloom region southwest of Iceland, DMS air/sea fluxes were as high as 300 μmol m−2 d−1, larger than current model estimates. The observations imply that gas exchange coefficients in this region are significantly greater than those estimated using most gas transfer parameterizations. South of 55°N, DMS levels were lower and the gas transfer coefficients were similar to those observed in other regions of the ocean. The data suggest that DMS emissions from the bloom region may be significantly larger than current estimates. The anomalous gas exchange coefficients likely reflect strong near‐surface, water column DMS gradients influenced by physical and biological processes.
Highlights
[2] Oceanic emissions of DMS play a potentially important role in the earth’s climate system, due to their role as a precursor for sulfate aerosol
[3] Estimates of the air/sea DMS flux are based on the expression: F = kDC, where DC is derived from near surface ($1 –5 m) seawater concentration measurements, and k is a gas transfer coefficient typically based on deliberate tracer and 14C studies [Nightingale et al, 2000a, 2000b; Wanninkhof, 1992]
‘‘bulk’’ near surface DMS concentrations, and 2) the physics of transport of DMS across the air/sea interface is analogous to that of inert gases. The validity of these assumptions is supported by recent shipboard eddy covariance DMS flux measurements in tropical and subtropical Atlantic and Pacific open ocean waters [Blomquist et al, 2006; Huebert et al, 2004; Marandino et al, 2007, 2008]
Summary
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