Climate: ‘We are headed for a seasonally ice-free ocean’

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Sparse ice along the east coast of Greenland during the peak of the summer melt season. @bberwyn photo.

Arctic once again loses thick multiyear ice

Staff Report

At the end of its melt season, the Arctic’s ice cover fell to the fourth lowest extent in the satellite record, both in the daily and monthly average, according to scientists at the National Snow and Ice Data Center (NSIDC). Sea ice extent hit 4.41 million square kilometers (1.70 million square miles) on September 11 and averaged 4.63 million square kilometers (1.79 million square miles) for the month of September.

This year edged out 2008 as the fourth lowest extent since satellites started regularly monitoring sea ice in 1979. The lowest Arctic extent on record occurred in 2012, when sea ice measured 3.62 million square kilometers (1.40 million square miles).

Arctic sea ice may not hit a record low level every year, but there’s now doubt it’s declining steadily, at the rate of about 13.4 percent per decade, according to National Snow and Ice Data Center experts, who released their latest sea ice update this week.

The final measurements for this year show that the ice extent ended up as the fourth-lowest on record, with the nine lowest September ice extents during the satellite record all occurring in the last nine years.

“What we have seen this summer reinforces our conclusions that Arctic sea ice extent is in a long-term decline and that we are headed for a seasonally ice-free ocean,” said NSIDC director Mark Serreze.

The downward trend in the extent of summer sea ice is  important because it influences how much sunlight is reflected, which in turn affects climate. The loss of summer ice is affecting Arctic ecosystems and is making the region more accessible to shipping and other activities.

This summer melt season began earlier than average and the maximum winter extent was the lowest on record. Between the seasonal maximum extent in February and the minimum in September, the Arctic Ocean lost a total of 3.91 million square miles of ice—the seventh largest total melt season ice loss in the satellite record.

“Every year since 2007 has seen more than 10 million square kilometers of seasonal ice melt, reflecting both a transition towards thinner winter ice that melts out more easily in summer as well as changes in the Arctic climate that foster more ice melt each year,” said NSIDC senior scientist Julienne Stroeve.

The pace of seasonal ice loss was especially brisk in July, with Arctic-wide temperatures reaching the second-warmest level during the satellite record (with 2007 ranked as the warmest).

“Another characteristic of this summer was further loss of the thicker multiyear portion of the ice pack. In the past, most of this multiyear ice was too thick and compact to melt completely, but now it’s more vulnerable,” said Walt Meier, research scientist at the NASA Goddard Space Flight Center. Meier is an affiliate scientist at NSIDC and is part of the Arctic Sea Ice News and Analysis team.

“Ten years ago this would have been an astonishing summer of ice melt,” said Ted Scambos, NSIDC’s lead scientist. “Now it is just another season in a decade of low years.”

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