Distribution of Dimethylsulfide andDimethylsulfoniopropionate in Arctic Shelf Region

Dimethylsulfide (DMS) is the most abundant biogenic sulfur-bearing compounds emitted from ocean to the atmosphere. DMS is oxidized in the atmosphere and condensed as aerosols, which affect the radiative balance of the Earth directly or indirectly. Ice algae are known to accumulate high amount of dimethylsulfoniopropionate (DMSP; precursor of DMS) in their cell for the purpose of cryoprotection. Therefore, the sulfur compound has potential significance in the Arctic climate. Observations in the Arctic Ocean were carried out in September, 1999 and from August to October, 2000. The concentrations of dissolved DMS, dissolved DMSP and particulate DMSP were determined for seawater samples collected at 7-9 water depths within 200 m from the surface at the 21 stations along the Beaufort shelf. Mean concentration of DMS in surface water was about 1.4 nmol/l (Range 0.2 17.5 nmol/l) . This suggests that the flux of DMS from this region to the atmosphere is moderate in the observed period. DMS and DMSP appeared within the upper 20 m of the water column, at most of the stations. Concentrations of particulate DMSP were relatively high, though that of dissolved DMSP and DMSP were low. This suggests the bacterial consumption of dissolved DMSP and DMS may active in summer. Relatively high concentrations of DMS and DMSP were found at the stations along Barrow Canyon, where the warm water mass was observed. Since the warm water mass in Barrow Canyon is believed to have originated from North Bering Sea, that indicates the Pacific water mass could affect the production of those sulfur compounds. High concentrations of particulate DMSP (maximum 30 nmol/l) were also found at the stations influenced by ice melt water rather than river water. That indicates ice algae are significant producer of DMSP and DMS in Arctic Ocean.