Satellite record set for low ice extent

Arctic sea ice cover likely melted to its seasonal low Sept. 16, at 1.32 million square miles the lowest summer minimum extent in the satellite record.

“We are now in uncharted territory,” National Snow and Ice Data Center Director Mark Serreze said Sept. 19. “While we’ve long known that as the planet warms up, changes would be seen first and be most pronounced in the Arctic, few of us were prepared for how rapidly the changes would actually occur.”

Useful satellite data on sea ice became available in late 1978 with the launch of NASA’s Scanning Multichannel Microwave Radiometer satellite, NSIDC says on its website.

The center said the Arctic used to be dominated by multiyear ice, ice that survived through several years, but in recent years “the Arctic is increasingly characterized by seasonal ice cover and large areas are now prone to completely melt away in summer.”

NSIDC defines the Arctic’s sea ice extent as the total area covered by at least 15 percent of ice. That sea ice extent varies from year to year due to weather conditions, but has shown “a dramatic overall decline” in the last 30 years, with this year’s minimum nearly 50 percent lower than the 1979 to 2000 average.

Arctic sea ice cover grows in the winter when the sun sets in the Arctic for several months, and shrinks in the summer as the sun rises higher in the northern sky, NSIDC said, with the Arctic sea ice reaching its minimum extent in September.

NSIDC said minimum extent number was preliminary, as changing weather conditions could push the ice extent lower.

—Petroleum News