A Dusty Greenland Is Speeding Up Glacial Melt

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"A Dusty Greenland Is Speeding Up Glacial Melt"

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CREDIT: http://www.jpl.nasa.gov

Greenland provides one of the best real-time visuals of climate change — cleaving glaciers the size of buildings cascading into the ocean as one long, slow river of ice returning to the sea. A new study shows that a layer of dust covering much of Greenland’s ice sheet could be speeding up this process.

A paper published in the journal Nature Geoscience suggests that dust particles embedded in Greenland’s massive ice sheet are gathering more heat than the otherwise white, reflective surface would and causing melting to accelerate. The scientists write that “recent warming in the Arctic has induced an earlier disappearance of the seasonal snow cover, uncovering large areas of bare soil and thus enhancing dust erosion.”

Dust absorbs the sunlight and re-radiates it as heat. This causes earlier snowmelt that in turn exposes ice beneath the snow sooner than otherwise would have been expected — creating a feedback loop.

This reduction in reflectivity is generating a lower albedo, a term used to indicate how well a surface reflects solar energy, across the landmass. More than three-quarters of Greenland is covered by an ice sheet that can reach up to two miles in thickness. If all 684,000 cubic miles of ice melted it could raise sea levels by up to 24 feet. “Greenland’s melt already accounts for about 30 percent of current sea level rise, which has been 8 inches since the 1880s, though the rate has been increasing in recent decades,” reports Climate Central.

“Dust gets transported to the Arctic by wind in the atmosphere,” Marie Dumont, a scientist at France’s meteorological agency who led the new study, told Climate Central. “High latitude sources of impurities can easily be redeposited on Greenland’s surface.”

The bright white surface of the Greenland Ice Sheet reflects well over half of the sunlight that falls on it. In summer, this reflectiveness helps the ice sheet maintain itself: less absorbed sunlight means less heating and melting. In the past decade, however, satellite observations show a drop in Greenland’s reflectiveness. The darker surface absorbs more sunlight, accelerating melting.

The bright white surface of the Greenland Ice Sheet reflects well over half of the sunlight that falls on it. In summer, this reflectiveness helps the ice sheet maintain itself: less absorbed sunlight means less heating and melting. In the past decade, however, satellite observations show a drop in Greenland’s reflectiveness. The darker surface absorbs more sunlight, accelerating melting.

CREDIT: Climate.gov

Prior to this study, the darker-looking surface on Greenland’s ice as seen from satellite imagery was commonly attributed to an increase in ice granule size that would be expected to occur as a result of the warmer temperatures happening across the planet due to climate change.

Another recent study found that reduced Arctic sea ice is having a similar effect by creating large areas of relatively dark ocean that are replacing higher albedo glaciers. This open water absorbs more of the sun’s energy and is likely having a much larger impact on the warming of the planet than previously expected.

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