Predictions Of Arctic Summer Ice Melt Come With Lots Of Uncertainty

  • Date: 02/08/14
  • Yereth Rosen, Alaska Dispatch News

Every year, as Arctic sea ice thins, scatters and melts, scientists ask: How low will it go? While the long-term trend of less summer Arctic ice is clear, the short-term outlook for total melt in any given year is far murkier, thanks to the many and sometimes highly volatile factors that drive the final outcome.

Still, scientists are attempting to predict how much Arctic sea ice will remain at the end of this year’s melt, expected in mid to late September. The latest round of expert predictions, released July 23, yields a median of almost 2 square miles, far above the record-low 1.3 square miles in 2012 but below the 1981-2010 average of more than 2.5 million square miles.

That median comes from 28 separate forecasts by numerous sources gathered in a loose group called the Sea Ice Prediction Network, which is coordinated by the Arctic Research Consortium of the United States. The predictions in the July Sea Ice Outlook range from a low of 1.2 million square miles, which would be a record, to a high of 2.28 million square miles.

Outlooks are published every month over the summer, starting in June. Some individual forecasts are refined as summer ice and weather data streams in.

The forecasting exercise has been conducted since 2008, said Walt Meier, the NASA research scientist who pulls together the forecasts and compiles them into monthly reports. The prediction network has grown over time, he said, though forecasts are mostly ad-hoc projects, sidelines to researchers’ main work.

Forecasts often miss the mark

While more people are contributing information, accuracy so far has not improved noticeably, and no prediction superstar or reliably best method has emerged, Meier said.

“No one’s been bragging about it,” he said. “As far as I know, there hasn’t been one that’s superior to anybody else’s.”

There are statistical forecasts — such as the one submitted by Meier, which predicts 1.75 million square miles, plus or minus 200,000 — that crunch numbers based on past years’ ice patterns. There are models of varying sophistication, which Meier believes will likely turn out to be the most accurate predictors, if properly refined. There are “heuristic” forecasts, which are predictions made more on “a wing and a prayer” or a “gut feeling,” he said. And there are combination approaches.

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