Meltponds Accelerating Loss of Arctic Sea Ice
24.02.2009 - Water & Oceans, Ice & Snow, Other, Arctic
A recent study published in the Journal of Geophysical Research is at odds with some of the computer models in the IPCC's Fourth Assessment Report. The IPCC's computer models had forecast an average loss of 2.5% in sea ice extent per decade from 1953 to 2006, whereas the actual rates turned out to be about 7.8% per decade.
The sea ice receded so much that it reached an all time low area of 4.14m km2 in September 2007 and that it left both the North-west and North-east Passages ice-free in the summer of 2008.
One of the reasons for the difference between simulations and reality are the so-called "melt-ponds". Melt ponds are pools of melted ice and snow that form on the sea ice during the spring and the summer. As they are darker than the surface of the ocean, they absorb a lot more sunlight, further increasing their temperature and accelerating the melting process. The IPCC's computer models did not factor the melt ponds into their models.
Melt ponds may play a growing role in future melting as first year ice, which melts in summer and freezes in autumn, replaces old multi-year ice, which remains frozen all year round.
According to PÅl Prestud, the director of the Centre for International Climate and Environmental Research (CICERO) in Oslo and author of a 2007 UN report on the melting of the ice and snow, global climate models have been good at predicting temperature, but have not been very good at predicting sea ice. "This research is one piece of the puzzle that will help us understand the physical processes involved in the melting of the Arctic and predict better what will happen in future," he said.
