Arctic sea ice continues to shrink, according to the latest satellite data. And in a scenario all too familiar to people of a certain age, the ice that is left has been replaced by a younger, thinner version of itself.

According to the US National Snow and Ice Data Center, the maximum extent of Arctic sea ice last winter was the fifth lowest on record. All sixth lowest maximums have occurred in the last six years (press release).

This year’s maximum was 15.16 million square kilometres, which is smaller than the 1979-2000 average by an area roughly the size of Texas (or France). Younger, thinner ice which melts every year is now 70% of Arctic sea ice, says the NSIDC, meaning melting is easier. In the 1980s and 90s this type of ice was between 40 and 50% of the total.

“Ice extent is an important measure of the health of the Arctic, but it only gives us a two dimensional view of the ice cover,” says Walt Meier of the NSIDC, which is run by the University of Colorado at Boulder. “Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover.”

Thomas Wagner, chief snow and ice scientist for NASA, adds, “The thicker ice particularly is very important, because it’s the thicker ice that survives the summer to stay around and reflect that summer sunlight.” (Reuters.)

The latest NSIDC data comes just days after a study in Geophysical Research Letters warned that the Arctic could be nearly ice free in 30 years, rather than the 90 some have been predicting (AFP story, research paper).

Headline watch

Ice, Ice Maybe – WSJ

Image: Arctic sea ice extent for March, 2009 / NSIDC