Mixed messages from Arctic sea ice data?

This summer’s melt of Arctic sea ice resulted in the third lowest ice extent since satellite ice observations started in 1979, and a continuing prevalence of thin ice that is vulnerable to future melting. But a detailed analysis of this year’s sea ice data shows some improved preservation of multiyear ice, according to an Oct. 6 report from the National Snow and Ice Data Center.

“We’ve preserved a fair amount of first-year ice and second-year ice after this summer compared to the past couple of years,” said Walt Meier, an NSIDC scientist. “If this ice remains in the Arctic through the winter, it will thicken, which gives some hope of stabilizing the ice cover over the next few years. However, the ice is still much younger and thinner than it was in the 1980s, leaving it vulnerable to melt during the summer.”

When the sea ice reached its minimum extent for this year, 49 percent of the ice was less than one year old and 32 percent was second-year ice, with the remaining 19 percent of the ice being older than two years. By comparison, in 2007 and 2008 the second-year ice only constituted 21 percent and 9 percent respectively of the ice cover.

Decline in thickness

Sea surface temperatures in the Arctic during this year’s melt season, although slightly lower than in the last two years, remained higher than normal. NSIDC attributes this year’s cooler conditions to cloudy skies during the late summer.

And this year’s increase in the ice extent is in part attributable to atmospheric conditions in August and September spreading out the ice pack, NSIDC said.

“It’s nice to see a little recovery over the past couple years, but there’s no reason to think that we’re headed back to conditions seen back in the 1970s,” said NSIDC Director and Senior Scientist Mark Serreze. “We still expect to see ice-free summers sometime in the next few decades.”

—Alan Bailey