Arctic freshwater bulge detected

CPOM scientists have discovered that the freshwater stored in the western Arctic Ocean has increased by 8000 km3 between the mid 1990s and 2010 by looking at changes in the sea surface height measured by the European Space Agency Satellites ERS-2 and Envisat.

This increase in fresh water corresponds to an increase in the anti-cyclonicity (clockwise in the Northern Hemisphere) of the wind over the western Arctic. Anti-cyclonic winds move the surface waters so that they pile up in the centre of the anti-cyclone, doming the sea surface. These findings are reported in Nature Geoscience (publication date – 22nd Jan 2012). Models had suggested that the action of the wind on the sea surface could cause a raised dome of freshwater to form in the middle of the Beaufort Gyre, but until now, there had been no continuous observations of sea-surface height to categorically demonstrate this. A reversal of the wind could lead to the release of this fresh water into the rest of the Arctic Ocean and possibly beyond.

Lead author, Katharine Giles says “We were surprised to find that our results also suggested that something else was going on. When we looked at our data on a year-to-year basis we noticed that the changes in the sea surface height did not always follow what the wind was doing so we thought about reasons as to why this might happen. One idea is that sea ice forms a barrier between the atmosphere and the ocean. So, as the sea-ice cover changes, the effect of the wind on the ocean might also change.”

UCL Lunch Hour Lecture: Here Katharine Giles describes the results from this paper (between minutes 10 and 20) along with an introduction about the Arctic sea ice and ocean, the use of satellites to monitor it, in particular CryoSat-2. UCL Lunch Hour Lecture youtube channel

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