How Do They Do It? Predictions are in for Arctic Sea Ice Low Point

Polar Bear on Arctic Sea Ice. Image-earthobservatory.nasa.gov

It's become a sport of sorts, predicting the low point of Arctic sea ice each year. Expert scientists with decades of experience do it but so do enthusiasts, whose guesses are gamely included in a monthly predictions roundup collected by Sea Ice Outlook, an effort supported by the U.S. government.

When averaged, the predictions have come in remarkably close to the mark in the past two years. But the low and high predictions are off by hundreds of thousands of square kilometers.

Researchers are working hard to improve their ability to more accurately predict how much Arctic sea ice will remain at the end of summer. It's an important exercise because knowing why sea ice declines could help scientists better understand climate change and how sea ice is evolving.

This year, researchers from the University of Washington's Polar Science Center are the first to include new NASA sea ice thickness data collected by airplane in a prediction.

They expect 4.4 million square kilometers of remaining ice (about 1.7 million square miles), just barely more than the 4.3 million kilometers in 2007, the lowest year on record for Arctic sea ice. The median of 23 predictions collected by the Sea Ice Outlook and released on Aug. 13 is 4.3 million.

"One drawback to making predictions is historically we've had very little information about the thickness of the ice in the current year," said Ron Lindsay, a climatologist at the Polar Science Center, a department in the UW's Applied Physics Laboratory.

To make their prediction, Lindsay and Jinlun Zhang, an oceanographer in the Polar Science Center, start with a widely used model pioneered by Zhang and known as the Pan-Arctic Ice Ocean Modeling and Assimilation System. That system combines available observations with a model to track sea ice volume, which includes both ice thickness and extent.