New research led by NASA and the University of Washington, Seattle, confirms that springtime snow on sea ice in the Arctic has thinned significantly in the last 50 years, by about a third in the Western Hemisphere and by half near Alaska.

The new study, published this month in the Journal of Geophysical Research, tracks changes in snow depth over decades. It combines data from NASA's Bromide, Ozone, and Mercury Experiment (BROMEX) field campaign, NASA's Operation IceBridge flights, and instrumented buoys and ice floes staffed by Soviet scientists from the 1950s through the 1990s.

"The snow cover is like a shield that can insulate sea ice," said Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, California, principal investigator for BROMEX and a coauthor of the new study.

"In this study, we had thousands of measurements of snow depth on sea ice to thoroughly validate NASA's aircraft observations. We knew Arctic sea ice was decreasing, but the snow cover has become so thin that its shield has become a veil."

The researchers found that, since the Soviet period, the spring snowpack has thinned from 14 inches to 9 inches (35 centimeters to 22 centimeters) in the western Arctic and from 13 inches to 6 inches (33 centimeters to 14.5 centimeters) in the Beaufort and Chukchi seas, north and west of Alaska, despite notable uncertainty in the historical estimates.

The authors speculate that delayed freezing of the sea surface may contribute to the thinning trend, as heavy snowfalls in September and October now fall into the open ocean.

What thinner snow cover will mean for sea ice is not certain. "The delay in sea ice freeze-up could be changing the way that heat is transported in the Arctic, which would, in turn, affect precipitation patterns. That's going to be a very interesting question in the future," said first author Melinda Webster, an oceanography graduate student at the University of Washington.

The full paper is online here.