Climate conditions in the Barents Sea are determined by both Atlantic and Arctic climate systems, and the winter North Atlantic Oscillation (NAO) explains about 15-20% of the inter-annual variability in air and sea temperatures in the southern region. The climate oscillates between warm and cold states. The warm state is characterized by low air pressure over the Sea giving southwesterly winds which cause increased Atlantic inflow, higher seasonal temperatures, and more northward positioning of the Polar Front.
Air pressure, winds, and air temperature
Consequently, there is less ice, and heat flux from the sea surface to the atmosphere is high. A high heat flux causes low air pressure and the cycle is closed. The cold state is characterized by a high-pressure center blocking the Atlantic inflow, low sea temperatures and more ice. Low heat flux from ocean to atmosphere thereby creates a high atmospheric pressure. It is uncertain whether the atmosphere is driving the ocean or the ocean driving the atmosphere. In either case, local positive feedback mechanisms are required to strengthen and maintain the existing state, whether warm or cold. Exposed only to local forces, marine climate can be stable; inducing a flip-flop between warm and cold states requires external forcing by large-scale oceanic and atmospheric circulation. In the Barents Sea, a positive NAO index is associated with several processes controlling inflow; high NAO is associated with both a higher volume flux and higher temperatures of the inflowing water (Ingvaldsen and Loeng, 2009). Spatial and temporal variability of air temperature in the Barents Sea depends greatly on solar radiation, atmospheric circulation, and transport of warm or cold waters by sea currents. During January, air temperatures range from -7oC in the south to -25oC in the north; during July, temperatures range from 12oC in the south to 1oC in the north. There is substantial inter-annual variability of air temperature, but clear similarities occur in year-to-year fluctuations, at least in the southern region (Ozhigin et al., 2011).