Freshwater content of the Arctic Ocean increased since 1990s

A new scientific study published in the journal Deep Sea Research documents how the freshwater content of the Arctic Ocean has increased substantially since the 1990s. This recent increase in Arctic freshwater is believed to be due to melting sea ice, increased input from rivers, and wind-induced changes in ocean circulation.

The Arctic is frozen ocean, surrounded by the northern edges of continents.

The Arctic Ocean has a light layer of freshwater that lies on top of a denser and deeper layer of salty seawater. Scientists are interested in studying the freshwater layer because it has the potential to flow out into the North Atlantic Ocean in the coming years and alter global ocean circulation patterns and climate.

Until recently, data on the Arctic Ocean’s salinity levels have been sporadic and limited to a few sampling stations. In a press release, lead study author Dr. Benjamin Rabe from the Alfred Wegener Institute for Polar and Marine Research notes:

… well coordinated research programs in the Arctic have substantially improved the database in … difficult to access areas.

Thanks to these programs, Rabe and his colleagues were able to analyze over 5,000 salt concentration profiles over large portions of the Arctic Ocean.

Salinity data from the years 2006-2008 show that the freshwater content of the upper Arctic Ocean has increased by 8,400 cubic kilometers of water when compared to observations taken from 1992 to 1999. For illustrative purposes, 8,400 cubic kilometers of water is slightly less than the amount of water contained in Lake Superior (12,000 cubic kilometers).

There is a good deal of regional variation in the new freshwater accumulated in the Arctic Ocean. Changes are more pronounced in the Eurasian basins than the North American basins. Overall, the increase of freshwater in the Arctic has depressed the depth of the upper less-saline layer by approximately 7 meters. Furthermore, the increased input of freshwater has decreased the average salinity in upper Arctic waters by about 0.5 parts per thousand (full strength seawater measures 35 parts per thousand on the salinity scale).

Image Credit: Hannes Grobe, Alfred Wegener Institute

The study on increasing fresh water in the Arctic Ocean was published in the February 2011 issue of Deep Sea Research. Continued collaborative research programs in the Arctic Ocean will be critical for tracking future polar changes in freshwater content on such a large scale.

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