Arctic ice on the move

Ice extent record minima, the opening of the Northeast or Northwest Sea Passages... The Arctic is often in the news these days. Modelling and forecasting its moves as well as its reaction to climate change are important issues.

The Arctic is one of the areas on Earth that is the most subject to climate change. Ice in the Arctic forms and melts with the seasons - fluctuating from one year to another. These fluctuations are even more visible under the influence of a warming climate.

Record melts, due to especially warm summers, were observed in the past few years. In September 2007, a record low sea ice extent was observed in the Arctic. As a result, for the first time ever, open water was observed in north-eastern Siberia up to 82° latitude. In 2008 and 2009, the sea ice extent level was very low again, although it did not meet the 2007 record. In 2009, navigation was possible north of Russia and America at the end of summer (the so-called North-East and North-West routes, linking the Atlantic and Pacific Ocean), an event that will most likely be increasingly frequent.

Explaining and making predictions about the decrease of the sea ice extent is a complex problem. When sea ice melts, the sun's radiation is absorbed by the ocean surface, amplifying the melt. On the other hand, increasing the area of the surface area of open water should encourage the formation of clouds which have the opposite effect. Widening the open water area in conjunction with more frequent Arctic storms tends to increase the impact of wind waves and swell on the ice cover, breaking it into small ice floes. Sea ice also plays a significant role in ocean's water mass formation and circulation by affecting water salinity and density when forming and melting. Finally, winds and currents constantly move the ice, piling or opening it up, making it a very complex and dynamic material.

Scatterometers and microwave sensors make it possible to monitor these changes in the Arctic, such as a decrease in its surface area. These aspects have been observed for several years. Furthermore, ice movements, forming at the edges of the ice pack and then drifting, are also monitored. In the near future, Cryosat satellite will also measure ice thickness. Modelling helps to better understand and forecast the movements of the ice and its formation and melting.

Credits : CNES - Mercator Océan - MyOcean
Data: NERSC (www.nersc.gov)
Realisation : Mira Production (www.mira.fr)
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