'Dramatic thinning' of Arctic ice since 1975

Combined Arctic ice observations have shown decades of loss.

University of Washington researchers compiled modern and historic measurements to get a full picture of how Arctic sea ice thickness has changed. The results show a thinning in the central Arctic Ocean of 65 percent between 1975 and 2012. September ice thickness, when the ice cover is at a minimum, is 85 percent thinner for the same 37-year stretch.

Lead author Ron Lindsay said that the ice is thinning dramatically, adding they knew the ice was thinning, but we now have additional confirmation on how fast, and we can see that it's not slowing down.

The study helps gauge how much the climate has changed in recent decades, and helps better predict an Arctic Ocean that may soon be ice-free for parts of the year.

The project is the first to combine all the available observations of Arctic sea ice thickness. The earlier period from 1975 to 1990 relies mostly on under-ice submarines. Those records are less common since 2000, but have been replaced by a host of airborne and satellite measurements, as well as other methods for gathering data directly on or under the ice.

At least for the central Arctic basin, even our most drastic thinning estimate was slower than measured by these observations,"said co-author Axel Schweiger.

The new study, he said, also helps confirm the methods that use physical processes to calculate the volume of ice each month. Using all these different observations that have been collected over time, it pretty much verifies the trend that we have from the model for the past 13 years, though our estimate of thinning compared to previous decades may have been a little slow.

What they see now is a little above the trend, but it's not inconsistent with it in any way, Lindsay said. It's well within the natural variability around the long-term trend.

The study is published in The Cryosphere.