Summer predictions for Arctic sea ice

graph of estimates from the SEARCH sea ice outlookLast week, an international group of researchers released their best estimates for Arctic sea ice extent over the summer melt season. The scientists are compiling their estimates so that they can better predict changes in Arctic sea ice. Credit: SEARCH Sea Ice Outlook
Average Arctic sea ice extent this May was the third lowest in the satellite record. Does that mean that ice extent will reach a new record low this summer? Or will it recover somewhat over recent years? Last week sea ice scientists from around the world shared their best answers to those questions, in the June report of the Sea Ice Outlook. For the report, the researchers used a variety of methods to predict how sea ice will behave this summer, such as statistical methods or computer models. Julienne Stroeve, who led the submission from NSIDC this year, said, “The project is meant to improve our understanding of Arctic sea ice changes.”

The Sea Ice Outlook pools the knowledge of sea ice researchers and shares those methods with their colleagues and the people around the world. University of Alaska geophysicist Hajo Eicken, who organizes the effort, said "Because this discourse on sea ice happens out in the open, the Outlook is a way for experts from other disciplines and the interested public to get a better perspective on the inner workings of sea ice science." While summer ice extent has been clearly shrinking over the years, in any given summer its extent may vary because of the weather.

Over the thirty-year satellite record, sea ice has shown a dramatic decline. In September, generally the lowest month of the year for Arctic sea ice extent, sea ice has dropped by more than 30 percent since 1979. That decline doesn’t run in a straight line, however, with each year falling a little lower than the last. Instead the ice extent dances around that downward trend line, buoyed by cold weather or winds that spread the ice pack apart, or forced downwards by sunny warm weather and winds that push the ice together. That means that predicting the ice extent in any given year is a difficult challenge, requiring researchers to combine data about sea ice extent and volume with models that factor in weather, atmospheric circulation, and ice movement. “The September ice cover still depends in large part on the summer weather,” Stroeve said. And weather can only be  predicted with accuracy seven to ten days in advance.

Most of the predictions for this year’s summer ice extent suggest that the ice will again fall far below normal, with about two-thirds of the estimates projecting a minimum sea ice extent lower than last year. The scientists will update their estimates each month during the summer, and at the end of the melt season the group will analyze how well their predictions compared to reality. NSIDC researcher Walt Meier said, “By comparing our outlooks with each other and seeing what others are doing, we can both better understand and better work together to improve understanding.”

Researchers hope that if they can better understand the changing Arctic, people could better prepare for and react to those changes. Meier said, “The impacts of reduced sea ice are already being felt. It is not like a switch gets turned on when the summer sea ice is gone and people and wildlife start being affected by it. They are already being affected and those impacts will grow in future years.” For more details on the forecasts, visit the Study of Environmental Arctic Change: Sea Ice Outlook Web site.

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