Warming of the Arctic continued to be widespread in 2008 and 2009, and in some cases, dramatic. Linkages between air, land, sea, and biology were evident. The report documents consistent trends of warming for the atmosphere, sea ice, and Greenland and many indicators of warming for the ocean, land, and biology. Featured in the biology section: reindeer, marine mammals, murres (comparison of impacts on thick-billed and common murres), fisheries in the Bering Sea, fisheries in the Barents Sea, Arctic char, and goose populations.
Summary statements from the report:
Surface air temperature anomalies reached an unprecedented +4°C during October through December 2008. There is evidence that the effect of higher air temperatures in the lower Arctic atmosphere is contributing to changes in the atmospheric circulation in both the Arctic and northern mid-latitudes. The annual mean Arctic temperature for the year 2008 was the fourth warmest year for land areas since 1990.
The extent of the 2009 summer sea ice cover was the third lowest value of the satellite record (beginning in 1979) and >25% below the 1979 - 2000 average.
Springtime multiyear ice extent was the lowest in 2008 in the data record since 2000.
Recent estimates of Arctic Ocean sea ice thickness from satellite altimetry show a remarkable overall thinning of ~0.6 m in ice thickness between 2004 and 2008. Within a declassified submarine data release area (covering ~38% of the Arctic Ocean), the overall mean winter thickness of 3.6 m in 1980 can be compared to a 1.9 m mean during the last winter of the ICESat record—a decrease of 1.7 m in thickness. This combined submarine and satellite record shows a long-term trend of sea ice thinning over submarine and ICESat records that span three decades.
In 2008, there was an unprecedented amount of fresh water in the surface layer of the Arctic Ocean. The source of the fresh water was melting sea ice. The heating of the ocean in areas of extreme summer sea ice loss (for instance, summer surface water temperatures in the Beaufort Sea were more than 3°C above average) was contributing to record high surface air temperatures in the fall (October through December) over the Arctic Ocean.
Since 2005, the Bering Sea has been relatively cold with more sea ice in the winter and spring than normal. In 2008 and 2009, the winter sea ice extent in the Bering Sea was at a near record maximum, not seen since the early 1970s, and ocean temperatures were at a near record minimum (Figure F2). Under these conditions, cold water species, such as Arctic cod, have returned toward the south.
At present Bering Sea climate change and ecosystem response are more effectively characterized by natural variability with multiple years of warm and cold temperatures, than by an emerging global warming trend or by an influence from the major summer sea ice losses in the Arctic Ocean proper. (An excellent graphic of the shift from benthic to pelagic production that occurs with loss of sea ice and changes in ocean water temperatures is included in the report summary.)