CREDIT: AP Photo/Becky Bohrer
Winter ice cover on Alaska’s lakes has declined over the last 20 years, a new study has found.
The study, published in The Cryosphere, looked at radar satellite radar imagery from lakes in Alaska’s North Slope and found a decrease in “grounded ice” — or ice frozen completely to the bottom of a lake — of 22 percent from 1991 to 2011. In all, that meant a decrease in ice cover of about 7 to 8.6 inches from 1991 to 2011 and of about 8.2 to 14.9 inches from 1950 to 2011.
“Prior to starting our analysis, we were expecting to find a decline in ice thickness and grounded ice based on our examination of temperature and precipitation records of the past five decades from the Barrow meteorological station,” Cristina Surdu, lead author of the study, told Phys.org. “At the end of the analysis, when looking at trend analysis results, we were stunned to observe such a dramatic ice decline during a period of only 20 years.”
The authors state that it’s changes in air temperature and precipitation that have made the most difference in the timing, duration and thickness of ice cover on Arctic lakes. That’s in line with other studies on climate change’s effect on the Arctic, which has been found to warm more quickly than other regions — as ice and snow decline due to warming, more heat is absorbed by water and land instead of reflected, causing more ice to retreat. The loss of sea ice particularly affects the Arctic’s warming, with the white, reflective ice giving way to dark, heat-absorbing ocean.
Warming is already affecting the Arctic’s wildlife. In October, about 10,000 walruses unable to find sea ice in the Arctic Ocean packed onto beaches in Northwest Alaska, seeking rest. The large numbers of the group put young walruses at risk of being trampled. Sea ice loss in the Arctic is also causing phytoplankton, which make up the base of the Arctic marine food chain, to bloom up to 50 days early, a trend which could throw off the balance of the marine ecosystem. And since polar bears spend more time on land now due to decreased sea ice, they’re mating more often with grizzly bears, resulting in hybrid offspring that used to be rare.