Tuesday, March 29, 2011

Large-scale assessment of Arctic Ocean shows significant increase in freshwater content

Terra Daily: The freshwater content of the upper Arctic Ocean has increased by about 20 percent since the 1990s. This corresponds to a rise of approx. 8,400 cubic kilometres and has the same magnitude as the volume of freshwater annually exported on average from this marine region in liquid or frozen form. This result is published by researchers of the Alfred Wegener Institute in the journal Deep-Sea Research. The freshwater content in the layer of the Arctic Ocean near the surface controls whether heat from the ocean is emitted into the atmosphere or to ice. In addition, it has an impact on global ocean circulation.

Around ten percent of the global mainland runoff flows into the Arctic via the enormous Siberian and North American rivers in addition to relatively low-salt water from the Pacific. This freshwater lies as a light layer on top of the deeper salty and warm ocean layers and thus extensively cuts off heat flow to the ice and atmosphere. Changes in this layer are therefore major control parameters for the sensitive heat balance of the Arctic.

We can expect that the additional amount of freshwater in the near-surface layer of the Arctic Ocean will flow out into the North Atlantic in the coming years. The amount of freshwater flowing out of the Arctic influences the formation of deep water in the Greenland Sea and Labrador Sea and thus has impacts on global ocean circulation.

…The freshwater content of the Arctic Ocean may rise due to increased sea ice or glacier melt, precipitation or river inputs. Less export of freshwater from the Arctic - in the form of sea ice or in liquid form - also results in a rise in the freshwater content. The authors of the study point to altered export of freshwater and altered inputs from near-coastal areas in Siberia to the central Arctic Ocean as the most probable reasons….

The German icebreaker Polarstern, where much of this research was conducted, shot by Bruce McAdam, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

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