A revised outlook for the Arctic 2008 summer sea ice minimum shows ice extent will be below the 2005 level but not likely to beat the record year of 2007.

Chances that the 2008 ice extent will fall below last year's record minimum is about 8 percent.

Chances that the 2008 ice extent will fall below last year's record minimum is about 8 percent.

Chances that the 2008 ice extent will fall below last year's record minimum is about 8 percent, researchers forecast after having run a number of different models predicting the fate of the Arctic sea ice this summer. But there's still reason for concern; the scientists are almots certain the ice extent will fall below the minimum of  2005, which was the second lowest year on record.

With a probability of 80% the minimum ice extent in 2008 will be in the range between 4,16 and 4.70 million km2.

Since weather forecasts for September are not available, the article is based on a probabilistic forecast: Given a certain range of atmospheric variability and the known conditions at the beginning of the melt season, how large is the probability that sea ice extent will fall below a certain value? The researchers have employed a technique named ‘ensemble simulation’ where atmospheric conditions from the years 1988 through 2007 have been prescribed to force an ocean-sea model.

The ocean-sea ice model calculates oceanic circulation, temperature, and salinity as well as sea ice drift, thickness, and concentration among other variables. The model incorporates the basic dynamical and thermodynamic equations that govern ocean and sea ice. Thus, it is able to reconstruct, starting from given initial conditions, the history of ocean and sea development through time. Input to the model are several atmospheric quantities that are necessary to calculate the heat, water and momentum exchanges between the different media. One can say that the model is "forced" by these atmospheric data.

The article is written by the DAMOCLES researchers Frank Kauker, Ruediger Gerdes and Michael Karcher.

The article is related to The SEARCH Sea Ice Outlook, which is an international effort to provide an integrated, community-wide summary of the state of arctic sea ice over the 2008 summer season. It is a response by the scientific community to the need for better understanding of the arctic sea ice system, given the drastic and unexpected sea ice decline witnessed in 2007.

The Sea Ice Outlook produces monthly reports based on an open and inclusive process that synthesizes input from a broad range of scientific perspectives. The intent is to summarize all available information from ongoing observing and modeling efforts to provide the scientific community, stakeholders, and the public the best available information on the evolution of the arctic sea ice cover.

Jul 4, 2008
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