Older sea ice in the Arctic giving way to younger, thinner ice

Washington, Jan 12 : A new study by University of Colorado at Boulder researchers has indicated that sea ice in the Arctic is giving way to younger, thinner ice, making it more susceptible to record summer sea-ice lows.

For the research, the team used satellite data going back to 1982 to reconstruct past Arctic sea ice conditions. They also used passive microwave, visible infrared radar and laser altimeter satellite data from the National Oceanic and Atmospheric Administration, NASA and the U.S. Department of Defense, as well as ocean buoys to measure and track sections of sea ice.

According to Research Professor James Maslanik of CU-Boulder's Colorado Center for Astrodynamics Research, there has been a nearly complete loss of the oldest, thickest ice and that 58 percent of the remaining perennial ice is thin and only 2-to-3 years old.

"We followed the ice in sequential images and track it back to where it had been previously, which allowed us to infer the relative ages of the ice sections," said William Emery, co-author of the study.

"This thinner, younger ice makes the Arctic much more susceptible to rapid melt," said Maslanik. "Our concern is that if the Arctic continues to get kicked hard enough toward one physical state, it becomes increasingly difficult to reestablish the sea ice conditions of 20 or 30 years ago," he added. A September 2007 study by CU-Boulder's National Snow and Ice Data Center indicated last year's average sea ice extent minimum was the lowest on record, shattering the previous September 2005 record by 23 percent.

According to the study, the portion of ice more than five years old within the multi-year Arctic icepack decreased from 31 percent in 1988 to 10 percent in 2007. Ice 7 years or older, which made up 21 percent of the multi-year Arctic ice cover in 1988, made up only 5 percent in 2007, the research team reported.

"The replacement of older, thicker Arctic ice by younger, thinner ice, combined with the effects of warming, unusual atmospheric circulation patterns and increased melting from solar radiation absorbed by open waters in 2007 all have contributed to the phenomenon," said Sheldon Drobot, co-author of the study.

"These conditions are setting the Arctic up for additional, significant melting because of the positive feedback loop that plays back on itself," he added.

"Taken together, these changes suggest that the Arctic Ocean is approaching a point where a return to pre-1990s ice conditions becomes increasingly difficult and where large, abrupt changes in summer ice cover as in 2007 may become the norm," said the research team.

ANI