Arctic Ice Thinning Much Faster Than Scientists Thought

Scientists have discovered that Arctic sea ice, the ice that freezes and floats on waters in the Arctic, is thinning at a much faster rate that they previously thought.

In a new study published in the journal The Cryosphere researchers using modern and historic measurements got an extensive view of the changes in the thickness of the Arctic ice over the past few decades.  According to the measurements, the ice found in the central Arctic has thinned approximately 65 percent from 1975 to 2012, from 11.7 feet to 4.1 feet.

The thinning is even more extreme for sea-ice levels in September, when the sea ice is at its lowest after the summer melt.  During the same period between 1975 and 2012, the ice thickness in September thinned 85 percent, from 9.8 feet to 1.4 feet.

"The ice is thinning dramatically," lead researcher, a climatologist at the University of Washington (UW) Applied Physics Laboratory, Ron Lindsay says. "We knew the ice was thinning, but we now have additional confirmation on how fast, and we can see that it's not slowing down."

Researchers used data from a number of different sources, making this study the first to combine all available observations on the Arctic sea ice thickness.  From 1975 to 1990, most of the ice thickness readings came from under-ice submarines using sonar to measure the ice drift so they could determine where they could safely surface.  Since 2000, most of the readings are based on airborne and satellite measurements such as NASA's IceSat satellite.

The data suggests that from 1975 to 2000, the Arctic sea ice thinned 36 percent, a little less than half of what the study found.

"At least for the central Arctic basin, even our most drastic thinning estimate was slower than measured by these observations," coresearcher of the study and polar scientist at the UW Applied Physics Laboratory, Axel Schweiger says. "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."

The data in the study ends in 2012, when summer sea-ice levels dropped to a record low.  Since that time, ice levels have actually increased, the researchers said.

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