The Heat Is Online

Sea-Ice Loss Hastens Thawing of Permafrost

Sea-ice loss threatens permafrost

 

The rapid disappearance of Arctic sea ice could warm temperatures inland and hasten permafrost's thaw

 

Environmental Science and Technology, June 25, 2008

 

As Arctic sea ice vanishes, permafrost could warm much more quickly than previously thought, according to new research. Melting permafrost could then release its vast stores of carbon into the atmosphere, accelerating global warming. The study is the first to link the loss of sea ice to warmer temperatures hundreds of miles inland.

 

The extent of Arctic sea ice has declined precipitously in recent years; last year, it reached a modern-day record low that was 39% below the long-term average from 1979 to 2000. Air temperatures over Arctic land were also warmer than usual late last summer and fall, prompting researchers from the National Center for Atmospheric Research (NCAR) and the National Snow and Ice Data Center to ask whether the sea-ice loss and land warming were related. The researchers' study was published June 13 in Geophysical Research Letters.

 

To find connections between land and sea temperatures, David Lawrence of NCAR and colleagues analyzed global climate simulations with NCAR's Community Climate System Model. The simulations revealed that during periods of sustained rapid ice loss, the rate of climate warming over northern Alaska, Canada, and Russia is 3.5 times greater than the average rates projected by climate models for this century. The warming can extend as much as 1500 kilometers inland and is strongest in autumn.

 

Although the mechanisms that link sea ice to inland warming are not fully understood, Lawrence says, they likely involve changes in ocean albedo, which is the amount of sunlight reflected by a surface. As ice melts, the ocean surface becomes darker and absorbs more heat from sunlight. "Some of the heat goes into melting more ice, and some [of it] accumulates in the ocean," he says, and in autumn, heat rises out of the ocean as the air above it cools. Warm air can then move over land and melt permafrost, which releases its stored carbon as either CO2 or methane.

 

This year's sea-ice extent is currently on track to break last summer's record low. However, scientists are not yet sure whether the trend will continue. If sea ice continues to disappear, "we may see a period of accelerated change," Lawrence notes.

 

-- Erika Engelhaupt

 

(c) 2008 American Chemical Society

 

http://pubs.acs.org/subscribe/journals/esthag-w/2008/jun/science/ee_seaice.html