Springtime snow on Arctic sea ice has thinned dramatically in the last 50 years, up to about half in some areas, according to new research by the National Aeronautics and Space Administration and University of Washington.

The new findings, published in the Journal of Geophysical Research, tracks changes in snow depth over several decades and asserts the snow levels dropped by about a third in the Western Hemisphere and half near Alaska.

The study combines data from NASA's Bromide, Ozone, and Mercury Experiment field campaign, NASA's Operation IceBridge flights and readings acquired from 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," Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, California, principal investigator for BROMEX and a coauthor of the new study, said in an agency news release. "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 discovered that, since the Soviet period, the spring snow pack has thinned from 14 inches to 9 inches, or 35 centimeters to 22 centimeters, in the western Arctic and from 13 inches to 6 inches, or 33 centimeters to 14.5 centimeters, in the Beaufort and Chukchi seas, north and west of Alaska.

The study researchers settled on their dire conclusions despite considerable uncertainty in the historical estimates.

The authors said that delayed freezing of the sea surface may contribute to the thinning trend, as heavy snowfalls in September and October have been landing on open ocean.

The implications of the thinner snow cover are still not certain, but "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 Seattle-based UW.