Large-scale assessment of the Arctic Ocean: significant increase in freshwater content since 1990s

[OKIsItJustMe]

http://www.awi.de/en/news/press_releases/detail/item/ozeanographie/?tx_list_pi1=6&cHash=0d02ee59862a2c12e2670da4987215c2

24. March 2011: Large-scale assessment of the Arctic Ocean: significant increase in freshwater content since 1990s

Bremerhaven, 24 March 2011. 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.



Dr. Benjamin Rabe from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association and his colleagues have evaluated a total of over 5,000 measured salt concentration profiles. To measure the depth distribution of the salt concentration, researchers used sensors from ships or mounted sensors on large ice floes so the data were recorded during the ice drift through the Arctic Ocean. Furthermore, measured values from submarines were inputted in the analyses. Major portions of the data stem from expeditions during International Polar Year 2007/2008. “The well coordinated research programmes in the Arctic have substantially improved the database in these difficult to access areas,” reports Rabe, who will again sail to the central Arctic on the research vessel Polarstern in the coming summer. The dense network of observations in recent years made it possible for the first time to come up with a comparative assessment of the freshwater content in the Arctic Ocean.

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The title of the original publication by Benjamin Rabe, Michael Karcher, Ursula Schauer, John M. Toole, Richard A. Krishfield, Sergey Pisarev, Frank Kauker, Rüdiger Gerdes and Takashi Kikuchi is: “An assessment of Arctic Ocean freshwater content changes from the 1990s to the 2006-2008 period“ and appeared in the journal Deep-Sea Research I 58 (2011) 173-185 (http://dx.doi.org/10.1016/j.dsr.2010.12.002">doi:10.1016/j.dsr.2010.12.002).

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[Vinnie From Indy]

1. Was reading about research done on ice cores taken from Greenland ice cap

This research shows quite clearly that in the past there was a huge influx of fresh water into the arctic and that influx caused the ocean conveyor belt of heat to drastically change. The change brought an ice age to the northern latitudes. Freshwater makes the ocean less salty and that in turn shuts down the gulf stream etc.