The Arctic Ocean is supplied with water from the Atlantic and Pacific through the Nordic Seas and the Bering Strait. Changes in temperature, salinity and density are seen in the Amundsen, Makarov and Beaufort Basins. The greatest changes in the temperature field are seen in the Atlantic Water layer, where the temperature at the most has increased with 0.50 degrees C from the 1990s to the 2000s, together with moving 25 meters on average up in the water column. The Pacific Water in the Beaufort Basin has thickened and increased in temperature from the early 1990s to the late 2000s. The interannual variability in both the Atlantic and Pacific Waters is large, and still clouding any certain evidence of a long-term trend continuing through the 2000s. In particular, the Atlantic Water temperature starts to decrease in the early 2000s in the Eurasian Basin. The cold halocline, which shields the surface layer from the warm Atlantic Water, disappeared during the 1990s in the Amundsen Basin, only to reappear during the late 2000s.
A consequence of the increasing temperature in the Atlantic layer is seen in a change of direction in the horizontal shear between the Eurasian and Canadian Basins. The Arctic Ocean density field is controlled by the salinity, but the changes in the temperature field have proved to be large enough to shift the shear. The shear change is caused by decreasing temperatures in the Amundsen Basin, connected with continuing increasing temperatures in the Makarov Basin. The temperature in the Amundsen Basin is still decreasing, observed by recent data. The Arctic Ocean is becoming fresher from early the 2000s, and especially in the upper surface layer in the Canadian Basin.