Dense water formation and circulation in the Barents Sea

Dense water masses from Arctic shelf seas are an important part of the Arctic thermohalinesystem. We present previously unpublished observations from shallow banks inthe Barents Sea, which reveal large interannual variability in dense water temperature andsalinity. To examine the formation and circulation of dense water, and the processes governinginterannual variability, a regional coupled ice-ocean model is applied to the BarentsSea for the period 1948-2007. Volume and characteristics of dense water are investigatedwith respect to the initial autumn surface salinity, atmospheric cooling, and sea-ice growth(salt flux). In the southern Barents Sea (Spitsbergen Bank and Central Bank) dense waterformation is associated with advection of Atlantic Water into the Barents Sea and correspondingvariations in initial salinities and heat loss at the air-sea interface. The characteristicsof the dense water on the Spitsbergen Bank and Central Bank are thus determinedby the regional climate of the Barents Sea. Preconditioning is also important to densewater variability on the northern banks, and can be related to local ice melt (Great Bank)and properties of the Novaya Zemlya Coastal Current (Novaya Zemlya Bank). The dense water mainly exits the Barents Sea between Frans Josef Land and Novaya Zemlya, whereit constitutes 63% (1.2 Sv) of the net outflow and has an average density of 1028.07 kgm−3. 0.4 Sv enters the Arctic Ocean between Svalbard and Frans Josef Land. Covering9% of the ocean area, the banks contribute with approximately 1/3 of the exported densewater. Formation on the banks is more important when the Barents Sea is in a cold state(less Atlantic Water inflow, more sea-ice). During warm periods with high throughflowmore dense water is produced broadly over the shelf by general cooling of the northwardflowing Atlantic Water. However, our results indicate that during extremely warm periods(1950s and late 2000s) the total export of dense water to the Arctic Ocean becomesstrongly reduced.