Study on atmosphere-ocean interaction through marine biogehic sulfur compounds (dimethylsulfide)

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With support of this grant-in-aid, we performed following terms ; (1) development of automatic measurement system of atmospheric DMS, (2) measurement of DMS in the seawater and atmosphere over the western North Pacific in spring and winter, (3) setting up an observation station at Hachijojima Island to obtain time series of atmospheric DMS. In addition, analysis of transport pathway of air parcel by an isentropic trajectory Analysis was also performed, and we analyzed aerosol chemical compositions to detect the Kosa particle and oxidation products of DMS in the marine air. Moreover to obtain the distribution of chlorophyll-a in this area, remote sensing chlorophyll-a data derived from SeaWiPs satellite was analyzed.Sea-air DMS flux was estimated with DMS concentrations in the surface seawater and atmosphere, SST and surface wind speed. Relationship between sea-air DMS flux and atmospheric DMS abundance was analyzed.As a result of analysis, seawater DMS in spring was higher than in December by a factor of 1.5〜2 in this area. Chlorophyll-a concentration derived from SeaWiES was also higher in April than in December. These results were due to an increase of marine production in spring. In addition, high MSA and non sea-salt sulfate concentrations in aerosol were observed when air parcel was transported from the elevated chlorophyll-a area within 1〜2 days. According to column model approach, these elevated concentrations in aerosol were mainly due to the, high emission of DMS in the elevated chlorophyll-a area and rapid oxidation of DMS under the high ozone condition. Although Kosa events were observed in these observations, we did not succeed getting enough data to show any sign of impact of Kosa on marine production.