WATER MASS-DISTRIBUTION AND POLAR FRONT STRUCTURE IN THE WESTERN BARENTS SEA

The water mass distribution in the western Barents Sea, the thermohali ne structure of the western Barents Sea Polar Front, and the local for mation of a dense water mass are described on the basis of an analysis of historical hydrographic data. This study concentrated on the front al region between Bjornoya and Hopen Island where Arctic water is foun d on the Spitsbergen Bank and Atlantic water in the Bear Island Trough and Hopen Trench. The distributions of Atlantic and Arctic waters in relation to topography were consistent with the hypothesis that the lo cation of the polar front is fixed at about the 250 m isobath by the b arotropic circulation of Atlantic water within the Bear Island Trough and Hopen Trench. In winter, vertical gradients of temperature and sal inity were weak throughout the frontal region, consistent with a barot ropic, topographically controlled front. In summer, vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh, warm surface water produced by melti ng ice. The topographic control of thermohaline properties at the surf ace was disrupted by the meltwater pool, and the meltwater contributed to water mass modification in the frontal region. The following seaso nal cycle of water mass formation was hypothesized: Summer heating mel ts the sea ice on the Spitsbergen Bank and produces the surface meltwa ter pool. This meltwater not only increases vertical thermohaline grad ients on the bank but also crosses the front and freshens the surface layer throughout the western Barents Sea. Subsequent winter cooling, w hich creates ice over the bank, also forms dense water in the Bear Isl and Trough and Hopen Trench by convective mixing of Atlantic water and the overlying meltwater.