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Cryosphere Today: Extent of summer ice in the Arctic.

Lecture on abrupt changes in summer sea ice extent


Friday 28th August Dr. Bruno Tremblay gives a lecture on abrupt changes in summer sea ice extent in the Arctic Ocean at IMO's headquarters in Reykjavík.


The year 2007 marked a record low in Arctic summer sea-ice extent, with 20% less ice area than the previous all-time record minimum of 2005 - the difference is more than 12 times the area of Iceland. This is part of a long-term trend of more than 8% ice extent decline per decade since the late seventies.

Analysis of simulation results from the Community Climate System Model (CCSM3), show that the Arctic could be free of ice in the summer around the years 2040, and that the transition to a summer ice-free Arctic could happen rapidly, i.e., over the course of a few years.

Sixty percent of all global climate models in IPCC also show abrupt transitions to an ice-free Arctic. While they mostly show abrupt transitions, all these models still underestimate the decline in sea-ice extent as compared to the satellite record (1979 -2006).

The sea ice albedo feedback is often cited as being responsible for the large changes in future sea ice conditions in the Arctic.

In this presentation we look at other feedbacks mechanisms involving the atmosphere (clouds) and the ocean in promoting ice free conditions. Simulations from control and forced runs are presented to bring to light the effect of increased greenhouse gas on sea ice changes.

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