August 11, 2011

MIT: Climate Report Fails To Capture Reality Of Thinning Ice

According to MIT researchers, the most recent global climate report fails to capture the reality of the changing Arctic seascape.

The researchers said the most recent global climate report fails to capture trends in Arctic sea-ice thinning and drift, and in some cases substantially underestimates these trends. 

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report estimates that an ice-free Arctic summer by the year 2100.

However, Pierre Rampal, a postdoc in the Department of Earth, Atmosphere, and Planetary Sciences (EAPS), and colleagues say it may happen several decades earlier.

The IPCC issues reports that represent an average of many findings, and is sometimes criticized for forecasting according to the "lowest common denominator" of climate research.

The team found that the forecasts were significantly off after comparing IPCC models with actual data. 

Rampal says part of the problem may be inadequate modeling of mechanical forces acting on and within the ice in the Arctic basin.

According to Rampal, the IPCC models have largely focused on temperature fluctuations, which are one way to lose or gain ice.

"If you make a mistake at this level of the model, you can expect that you are missing something very important," Rampal said in a press release.

He said mechanical forces can play a significant role in winter, when little melting occurs but when strong winds and ocean currents can wreak drastic effects on the ice's shape and movement.

Most of the Arctic Ocean is covered with a thick sheet of ice in the winter.  But winter ice today is thinner, meaning it breaks up easier under the influence of winds and currents.  This leads to even more ice break up in the summer.

Rampal said large cracks in winter's ice cover help create new ice, since the extremely cold air in contact with the liquid ocean promotes refreezing.

Because "everything is coupled" in these intricate feedback loops, "it's hard to predict the future of Arctic sea ice," Rampal said in a press release.

Although it is impossible to say for sure when there could be an ice-free Arctic, the IPCC said that its 2007 report may have painted too rosy a picture.

"If you look at the scientific knowledge things do seem to be getting progressively worse," said Rajendra Pachauri, IPCC chair, in an interview reported by The New York Times.

The findings will be published in the Journal of Geophysical Research - Oceans.


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