WATERLOO, Ontario, Feb. 3 (UPI) -- Alaska's icy lakes are melting earlier than usual each year, and far fewer are freezing through to the bottom during the winter, suggesting that land ice is mirroring the losses seen in sea ice in the region.
Using Europe's ERS satellites, researchers combed through 20 years of data and found that these shallow, icy lakes are melting earlier than usual and have melt water in them for longer than they used to. This has affected the landscape of land ice along Alaska's coastal Arctic plains, a signal of the effects of climate change.
"We're seeing warmer air temperatures; we're seeing sea-ice extent decreasing; and we're seeing a general greening of the Arctic with the treeline moving north. The lakes are part of that story," said Dr. Cristina Surdu from the University of Waterloo, Ontario, Canada.
Surdu and her colleagues focused on the 400 or so lakes near Barrow, the largest settlement on Alaska's North Slope. These lakes measured up to 23 sq. miles and were not deeper than 5 feet. Using the data from the ERS satellites, the researchers were able to sense the signature of water, even if it was below 3 inches of ice.
They found that over the years the amount of water freezing right through to the bed was getting smaller and smaller. From 1991 to 2011, they found that the fraction of this ice had dropped by 22 percent and was equivalent to the lakes' ice caps reducing by 7 to 8 inches.
The results of this research have been published in the The Cryosphere.
Apart from the 1.7°C drop in mean air temperature in the region, climate change seems to have affected the precipitation patterns of the region. Snow is critical to development of the ice caps, acting like an insulator.
"If it falls at the beginning of the ice season, it slows down the thickening of the ice on these lakes; whereas, if it falls at the end of the ice season, it helps retain the ice because it insulates that ice from warming temperatures," said Surdu.
The satellites used have now been decommissioned by the ESA, but the agency is launching the Copernicus-Sentinel program that will relay faster and more comprehensive data.