Thick, Old Arctic Ice Nearly Gone

Jan. 18, 2008 -- A new study using satellite measurements of Arctic sea ice have revealed that thinner ice that's only two or three years old now accounts for 58 percent of the ice cover -- up from 35 percent in the mid-1980s.

Meanwhile, ice older than nine years had all but disappeared by 2007.

The extinction of the older, thicker ice is effectively melting away the Arctic Ocean's hedge against complete summer meltdowns, say researchers.

"The thinning is consistent with long-term warming," said ice researcher James Maslanik of the University of Colorado in Boulder.

Maslanik is the lead author of a paper reporting the thinning ice published in the latest issue of the journal Geophysical Research Letters.

The key difference in the new study from those done in the past is that the researchers were able, for the first time, to distinguish and measure different thicknesses of perennial ice -- that's ice which survives summer melts to grow thicker for multiple winters.

The result is that the researchers can better calculate the sea ice volume in addition to how much area the sea ice is covering.

Both are critical numbers for deciphering how the Arctic Ocean is responding to global warming.

"In our study, in the maps, there are a couple of places where the ice thickness has increased," said Maslanik, "but it doesn't balance out with the losses."