Going, going, gone…Arctic summer sea ice

A new study expects summer sea ice in the Arctic to shrink from 2.8 million square miles to a mere 620,000 square miles within 30 years. Average autumn temperatures for 2005-2008 were 5 degrees Celsius above what had been predicted for the year 2070.

Conducted by scientists from the Joint Institute for the Study of Atmosphere and Ocean and the National Oceanic and Atmospheric Administration (NOAA) working with climate change models from the U.N. Intergovernmental Panel on Climate Change, the official report will appear later today in the Geophysical Research Letters review.

Much of the reason why this same type of story keeps coming up – ice melting and temperatures rising faster than ever before – has to do with the albedo effect and positive feedback loops. As more ice melts, there is less white ice to reflect the sunlight back into the atmosphere. Instead, the dark surface of the ocean absorbs the heat, warming the water and amplifying the problem of melting sea ice. With a positive feedback loop, a change in one direction causes a response in the same direction. So: a little melting —> a lot of melting.

A few years ago, the New Yorker had an excellent three-part series on global warming and its consequences for the Arctic, devoting a large amount of space to explaining the workings of the albedo effect (registration required).

The author of the three-part series in the New Yorker, Elizabeth Kolbert, also provided this succint definition of the albedo effect:

Albedo is a measure of reflectivity. The ice in the Arctic, and also in the Antarctic, reflects a tremendous amount of sunlight back into space. This is a very significant factor in shaping the earth’s climate. In the Arctic, the ice, and particularly the sea ice, is melting, and this is changing the earth’s reflectivity. More heat is being absorbed, which is causing more sea ice to melt, and so on. This is a good example of positive feedback. It’s taking a relatively small change to the system and amplifying it into a much larger one. There are several positive feedbacks in the climate system that are known, and quite possibly others that haven’t yet been identified, and all are cause for concern.

News link: Study: Arctic sea ice melting faster than expected (Associated Press)*

*Some other newspaper headlines today have reported, “Arctic sea ice gone in 30 years.” While this tone is rather alarmist, it is important to keep in mind that this is summer sea ice – not sea ice in general. Of course, that does not really make the situation any less dire for polar bears, whales, krill, and other organisms in the Arctic, but the headlines could be misleading in any case.

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