Written By: Jim Greenberg
Winter ice on the shallow lakes of Alaska’s Arctic coastal plain is declining, reveals analysis of twenty years of satellite imagery.
The study, published in The Cryosphere, included over 400 lakes and used data from Europe’s ERS satellites to determine the presence of water on the ground, even water covered by tens of centimeters of ice.
Results from the study show that the amount of grounded ice (ice that freezes right to the bottom of the lake) decreased by 22% from 1991 to 2011, an amount equivalent to the lake’s ice thickness being reduced by 18–22 cm.
This means that ice on many of the shallow lakes, which are often no more than 3 m deep, is melting earlier in the season, and that the lakes are retaining open water conditions for longer periods. Analysis of the images taken over the 20-year period showed that the ice declined most abruptly during the final six years of the investigation, reaching its lowest point in 2011.
Authors of the study say that climate change, including changes in air temperature and precipitation, contributed to changes recorded in the timing, duration, and thickness of ice cover on Arctic lakes.
Illustrating how changes in weather patterns can affect ice cover, Dr. Cristina Surdu, of the University of Waterloo, Ontario, lists snow as an example.
“Snow is a very important factor in all this because it is an insulator. If [snow] 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.”
She adds, “What we’re actually seeing is more snowfall at the beginning of the ice season, so the precipitation is working against the ice.”
Although the presence of increased liquid water beneath the lake ice increases the availability of fresh water, these changes to the lakes’ ecology may also have negative impacts. One such impact is the thinning of “ice roads,” routes depended upon by the residents of Barrow and its neighboring communities for essential resources.