To further understand the origin of the warming episodes of the Arctic Ocean, as manifested both by increased ocean temperatures and decreased ice cover in the last 20 years, we have investigated the changes in the GIN (Greenland-Iceland-Norwegian) Sea from a model and hydrographic observations. The beginning of the warming episode was first observed in the Arctic Basin north of the Svalbard Islands in early 1990.

The GIN Sea serves as the principal passageway of ocean currents between the North Atlantic and the Arctic Ocean, as well as the dominant location of deep water formation feeding the North Atlantic. One possible cause of these changes is attributed to increased inflows of warmer Atlantic-origin water into the Arctic.

Large, in-situ hydrographic data sets representing 10 years of measurements, as well as results from a global 20-year simulation, have been applied toward evaluating these changes. The model results were obtained from a 1/3 degree, 32 level global configuration of the Parallel Ocean Program (POP) model of Los Alamos, forced by daily reanalysis fluxes from ECMWF (1979-1997). In the southern Norwegian Sea, both observations and simulations show a steady increase of the mean temperature, starting in late 1988; however, only the observations show the large warm anomaly of June 1989. In the Fram Strait, the warmest inflow into the Arctic occurs in 1997.