Atlantic sources of the Arctic Ocean surface and halocline waters

Data obtained during the last 20 years from selected hydrographic sta-tions throughout the Arctic Ocean basins and at the continental slopes and northern parts of the surrounding shelf seas are examined to esti-mate the contribution of Atlantic water to the upper part of the Arctic Ocean water column, and to follow the circulation of the Atlantic derived halocline waters around the Arctic Ocean basins. A substantial frac-tion of the Atlantic water entering the Arctic Ocean in the two infl ow branches, the Fram Strait branch and the Barents Sea branch, is trans-formed into less dense waters. The infl ow through Fram Strait encounters and melts sea ice. Its upper part becomes less saline, and in winter, ice formation homogenizes this low salinity upper part into a winter mixed layer, which follows the boundary fl ow eastward. The infl ow over the Barents Sea mainly becomes colder, less saline and denser due to cooling and net precipitation, but melting of sea ice also here creates a less dense upper layer, which is subsequently homogenized by haline convection.