The summer melt of Arctic sea ice wasn't quite as bad this year as the last two years. But it still ranked as the third biggest melt in 30 years.
The National Snow and Ice Data Center announced Thursday that the Arctic sea ice reached its annual minimum last Saturday. The ice cap is now growing again with the onset of fall.
Last Saturday, sea ice covered about 2 million square miles of ocean. The biggest melt in 30 years happened in 2007, when the ice cap covered 1.6 million square miles. In 2008, the ice covered 1.8 million square miles.
The reason the ice cap did not shrink as much this year as it did in the previous two years is that summer temperatures were relatively cooler, especially in the Chukchi and Beaufort seas, according to the center, based in Boulder, Colo.
A smaller decline doesn't imply a recovery, said Walter Meier, a research scientist at the center.
The Arctic ice cap has increased in size about 14 times in the past 31 years, but the overall trend is a steady decline in the size of the pack, according to the center's charts. The trend of declining sea ice corresponds to a rise in temperature over the same period, Meier said.
It's more useful to look at the long-term trend than year to year, Meier said. The record ice loss of 2007 happened during an unusual Arctic summer. A destructive confluence of events -- winds and unusually-high temperatures -- triggered dramatic losses from an already weakened ice pack, Meier said.
This summer, roughly 50 percent of the ice pack is just a year old -- meaning that it is weaker and thinner. In the past, multi-year ice would have represented 75 percent of the ice pack. "That's a really dramatic change," Meier said.
Arctic sea ice is important because it helps moderate warmer temperatures elsewhere. Experts blame global warming for the increased melting of sea ice and fear that eventually no sea ice will survive the summer.
Mead Treadwell, of the U.S. Arctic Research Commission, said he flew over the Beaufort Sea on a Coast Guard flight this week for hundreds of miles without seeing any multi-year ice.
"It's a significant difference for anyone who has been watching this ocean for some time," Treadwell said.
The Snow and Ice Data Center said Thursday that the Beaufort Sea lost even more ice than it did in 2007's record year because southwesterly winds pushed the ice edge toward the northeast.
Elizabeth Bluemink contributed to this report. Find her online at adn.com/contact/ebluemink or call 257-4317.