Boulder researchers stunned by rapid retreat of Arctic sea ice

Bill Scanlon, Rocky Mountain News

Published September 21, 2007 at midnight

Text size

More Local News

BOULDER - There was less ice in the Arctic Ocean last week than at any time in the 30 years it's been measured, researchers said Thursday.

"The amount of ice loss this year absolutely stunned us," said scientist Mark Serreze of the University of Colorado's National Snow and Ice Data Center.

"It didn't just beat all previous records - it completely shattered them."

The drop was so drastic that the scientists now think the Arctic could be ice-free for at least one day in as few as 13 summers - 50 years sooner than researchers were predicting just a few years ago.

The new ice-free area is so large California and Texas could fit into it, said NSIDC scientists.

The old record was set two years ago, on Sept. 20 and 21, 2005, when ice covered at least 15 percent of the ocean surface over a stretch of slightly more than 2 million square miles.

By August of this year, scientists knew that a new record was coming. But it wasn't until last week, when the ice finally stopped receding, that they learned it shattered the old mark by 460,000 square miles.

The CU scientists blame the declining sea ice, in part, on greenhouse gases that they say have elevated temperatures 2 to 7 degrees Fahrenheit across the Arctic. They also say there can be strong natural variability from year to year in Arctic sea ice.

It's not easy to determine when the melt season has decisively ended each September, the scientists said. But the team has recorded five days of little change. The sea-ice minimum usually happens in September, and the maximum in March.

Bill Chapman, an arctic climate researcher from the University of Illinois, said the Boulder center's numbers align with satellite data.

"The climate models had been showing somewhere between 2070 and 2100" for the first ice-free summer day in the Arctic, he said. "But the pace of the observed sea-ice decline is much faster than that - way ahead of the trend any of the models are showing. It certainly opens the door to it possibly happening 15 or 20 years from now."

The researchers used satellite data from NASA, the National Oceanic and Atmospheric Administration and the U.S. Department of Defense.

Climate models going back 30 years have agreed that the Arctic sea is getting more ice-free over time, and that it's a clear indicator of carbon dioxide emissions, NSIDC research scientist Walt Meier said Thursday.

scanlon@RockyMountainNews.com or 303-954-2897

Subscribe to the Rocky Mountain News