A large dome of fresh water has been building up in the Arctic Ocean over the last 15 years. The water is spilling into the north Atlantic and cooling Europe caused by a change in wind direction. Since 2002, the sea surface in the studied area has risen by about 15 cm, and the volume of fresh water has increased by some 8000 cubic km – around 10% of all the fresh water in the Arctic Ocean. Anti-cyclonic winds move the surface waters so that they pile up in the centre of the anti-cyclone, doming the sea surface.
Researchers from the Centre for Polar Observation and Modelling (CPOM) at University College London and the UK’s National Oceanography Centre used data from ESA’s ERS-2 and Envisat satellites (the largest Earth observation satellite ever built) to measure sea-surface height over the western Arctic from 1995 to 2010. The scientists conclude that the dome could be a result of strong Arctic winds accelerating a large ocean circulation known as the Beaufort Gyre, causing the sea surface to bulge. A change in the direction of the wind would cause the fresh water to spill into the rest of the Arctic Ocean and even reach the north Atlantic. This could slow a key ocean current, stemming from the Gulf Stream, and subsequently cool Europe.
This current keeps the continent relatively mild compared to other areas at similar latitudes. 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. Sea ice can be measured by different types of satellite data. Radar altimeters on satellites such as the two used in the study, Envisat and ERS-2, can be particularly useful when observing inaccessible areas like the Arctic.
Envisat, , will mark 10 years in orbit in March. ERS-2 was retired in July 2011, but 20 years of data from it and predecessor ERS-1 on oceans, land, ice and atmosphere will continue to be used by scientists for years to come. ESA will continue to monitor the Arctic with the upcoming Sentinel series of Earth-observing satellites for Europe’s Global Monitoring for Environment and Security (GMES) programme. Later this year, the first results of seasonal changes in sea-ice thickness from data acquired by ESA’s CryoSat-2 satellite will be presented.
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