Arctic sea ice reaches lowest extent for 2013
Monday, September 23, 2013, 9:59 -
The amount of ice in the Arctic Ocean this summer was at its sixth-lowest level on record on September 13-- but it's still much higher than last year's record low.
Analysis of satellite data by the U.S. National Snow and Ice Data Center (NSIDC) and NASA showed that the sea ice extent shrunk to 5.10 million square kilometres (1.97 million square miles).
That's still substantially higher than last year's record low minimum.
"On Sept.16, 2012, Arctic sea ice reached its smallest extent ever recorded by satellites at 3.41 million square kilometres (1.32 million square miles)," NASA says. "That is about half the size of the average minimum extent from 1981 to 2010."
Experts say an unusually cold summer in the northernmost latitudes triggered a considerable recovery from last year, but it comes as no surprise.
"I was expecting that this year would be higher than last year," said Walt Meier, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Md. "There is always a tendency to have an uptick after an extreme low; in our satellite data, the Arctic sea ice has never set record low minimums in consecutive years."
Still, scientists say it's not a sign of a long-term recovery.
According to NASA, the ice cap covering the Arctic Ocean shrinks and expands with the passing of the seasons, melting in the summer and refreezing during the long, frigid Arctic winter. Despite these occasional ups and downs in sea ice extent, the trend over the past several decades has pointed to less sea ice in the summer over time.
"The remaining Arctic sea ice cover is much thinner on average than it was years ago," NASA says. "Satellite imagery, submarine sonar measurements, and data collected from NASA’s Operation IceBridge, an airborne survey of polar ice, indicate that the Arctic sea ice thickness is as much as 50 percent thinner than it was in previous decades, going from an average thickness of 12.5 feet (3.8 meters) in 1980 to 6.2 feet (1.9 meters) in recent years."
The thinning is due to the loss of older, thicker ice, which is being replaced by thinner seasonal ice.