Scientists explain ‘08 sea ice record

People in Alaska who’ve experienced an exceptionally cool summer and early winter snow may be wondering why the Arctic sea ice reached its second lowest extent on record this year. The ice shrank to an average minimum area of 1.8 million square miles in September 2008, compared with 1.65 million square miles in September 2007.

The National Snow and Ice Data Center has provided an explanation.

Apparently, newly formed Arctic ice actually covered a record area of 73 percent of the Arctic basin in March. But because this first-year ice was very thin it was especially prone to melting during the summer. And as the ice melted, solar energy entering the ocean warmed the water. The warm water, in turn, accelerated the melting process and proved a major factor in reducing the ice cover — the rate of ice lost in August was the highest recorded since reliable satellite observations began.

In fact, the NSIDC scientists think that because the ice was especially thin, the total sea ice volume at the 2008 minimum was probably the lowest ever recorded.

And had the Arctic summer been as warm as in 2007, the minimum areal extent would also have beaten the 2007 record.

“I find it incredible that we came so close to beating the 2007 record without the especially warm and clear conditions we saw last summer,” said NSIDC research scientist Julienne Stroeve. “I hate to think what 2008 might have looked like if weather patterns had set up in a more extreme way.”

NSIDC senior scientist Mark Serreze warned that the 2008 reversal of the multiyear decline in the sea ice minimum should not be assumed to mark the start of a recovery of the Arctic ice cap.

“When you look at the sharp decline that we’ve seen over the past 30 years, a ‘recovery’ from lowest to second lowest is no recovery at all,” Serreze said. “Both within and beyond the Arctic the implications of the decline are enormous.”

—Alan Bailey