Can we Predict the Local/Global Distribution of Dimethylsulfide?

Abstract

Dimethylsulfide (DMS) appears to be relatively widespread in oceanic waters. Concentrations of DMS in seawater vary significantly in space within specific areas. Detailed analysis failed to provide any simple correlation of DMS in seawater with chlorophyll a or primary production. Shipboard measurements of DMS in air and water, as well as surface chlorophyll, were taken in the North Atlantic in the summer of 1989 during NASA CITE-3’s northern hemisphere missions. Large-scale changes associated with features such as the Gulf Stream can be seen; however, no striking correlations were observed among these parameters over time once the ship remained on a single station. ODAS, a spectro-radiometer mounted and operated from an aircraft, provided relative chlorophyll values derived from the radiances collected. Tropospheric DMS values were simultaneously collected in-flight by E. Saltzman and D. Cooper (RSMAS, Miami). Preliminary results from three missions show a decrease in relative chlorophyll numbers with increasing concentrations of atmospheric DMS. A bloom of the cyanobacterium Oscillatoria seen on the very surface at one station was not accompanied by an equivalent DMS signal in water nor in air. We analyzed the relationships between plant biomass, CITE-3 DMS, and shipboard DMS data for the northern hemisphere missions. Whether the concentrations of in-flight atmospheric DMS observed were the result of the algal communities surveyed by the spectro-radiometer or the meteorological conditions before, and during, each mission will be discussed.