Water mass distribution and Polar Front structure in the Southwestern Barents Sea

Abstract

The water mass distribution in the southwestern Barents Sea, the thermohaline struc- ture of the western Barents Sea Polar Front, and the formation of local water masses are described based on an analysis of historical hydrographic data and a recent process-oriented field experiment. This study concentrated on the frontal region between Bj0rn0ya and Hopen Island where Arctic water is found on the Spitzbergen Bank and Atlantic Water in the Bear Island Trough and Hopen Trench. Distributions of Atlantic, Arctic, and Polar Front waters are consistent with topographic control of Atlantic water circulation. Seasonal buoyancy forcing disrupts the topographic control in the surface layer, altering the frontal structure, and affecting local water mass formation. In the winter, the topographic control is firmly established and both sides of the front are vertically well-mixed. Winter cooling creates sea-ice over Spitzbergen Bank and convectively formed Modified Atlantic Water in the Bear Island Trough and Hopen Trench. In the summer, heating melts the sea-ice, producing a surface meltwater pool that can cross the polar front, disrupting topographic control and substantially increasing the vertical thermohaline gradients in the frontal region. The meltwater pool produces the largest geostrophic shear in the region.