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As the Arctic Gets Darker, Earth Is Getting Warmer

By: Seth Borenstein
Published: February 18, 2014

WASHINGTON — The Arctic isn't nearly as bright and white as it used to be because of more ice melting in the ocean, and that's turning out to be a global problem, a new study says.

With more dark, open water in the summer, less of the sun's heat is reflected back into space. So the entire Earth is absorbing more heat than expected, according to a study published Monday in the Proceedings of the National Academy of Sciences.

That extra absorbed energy is so big that it measures about one-quarter of the entire heat-trapping effect of carbon dioxide, said the study's lead author, Ian Eisenman, a climate scientist at the Scripps Institution of Oceanography in California.

The Arctic grew 8 percent darker between 1979 and 2011, Eisenman found, measuring how much sunlight is reflected back into space.

"Basically, it means more warming," Eisenman said in an interview.

The North Pole region is an ocean that mostly is crusted at the top with ice that shrinks in the summer and grows back in the fall. At its peak melt in September, the ice has shrunk on average by nearly 35,000 square miles — about the size of Maine — per year since 1979.

Snow-covered ice reflects several times more heat than dark, open ocean, which replaces the ice when it melts, Eisenman said.

As more summer sunlight dumps into the ocean, the water gets warmer, and it takes longer for ice to form again in the fall, Jason Box of the Geological Survey of Denmark and Greenland said in an email. He was not part of the study.

(MORE: Arctic Didn't Melt As Much in 2013)

While earlier studies used computer models, Eisenman said his is the first to use satellite measurements to gauge sunlight reflection and to take into account cloud cover. The results show the darkening is as much as two to three times bigger than previous estimates, he said.

Box and University of Colorado ice scientist Waleed Abdalati, who was not part of the research, called the work important in understanding how much heat is getting trapped on Earth.

MORE: Alaskan Glaciers in Retreat

Muir Glacier and Inlet (1895)

Muir Glacier and Inlet (1895)

In the photo above, the west shoreline of Muir Inlet in Alaska's Glacier Bay National Park & Preserve is shown as it appeared in 1895. Notice the lack of vegetation on the slopes of the mountains, and the glacier that stands more than 300 feet high. See the glacier as it looked in 2005 on the next page. (USGS/Bruce Molnia)

  • Muir Glacier and Inlet (1895)
  • Muir Glacier and Inlet (2005)
  • Plateau Glacier (1961)
  • Plateau Glacier (2003)
  • Bear Glacier (1920s)
  • Bear Glacier (2005)
  • Northwestern Glacier (1920s-1940s)
  • Northwestern Glacier (2005)
  • Northwestern Glacier (1909)
  • Northwestern Glacier (2004)
  • Pedersen Glacier (1920s-1940s)
  • Pedersen Glacier (2005)
  • Pedersen Glacier (1909)
  • Pedersen Glacier (2005)
  • Reid Glacier (1899)
  • Reid Glacier (2003)
  • Muir Glacier and Inlet (1890)
  • Muir Glacier and Inlet (2005)
  • Muir Glacier and Inlet (1896)
  • Muir Glacier and Inlet (2005)
  • Yale Glacier (1937)
  • Yale Glacier (2006)
  • Muir Glacier and Inlet (1880s-1890s)
  • Muir Glacier and Inlet (2005)
  • Muir Glacier (1941)
  • Muir Glacier and Inlet (1950)
  • Muir Glacier and Inlet (2004)
  • Carroll Glacier (1906)
  • Carroll Glacier (2004)
  • Muir Inlet (1976)
  • Muir Inlet (2003)
  • McCarty Glacier (1909)
  • McCarty Glacier (2004)
  • McCarty Glacier (1909)
  • McCarty Glacier (2004)
  • Muir and Adams Glaciers (1899)
  • Muir and Adams Glaciers (2003)
  • Yalik Glacier (1909)
  • Yalik Glacier (2004)
  • Denali National Park (1919)
  • Denali National Park (2004)
  • Northwestern Glacier (1920s-1940s)
  • Northwestern Glacier (2005)
  • Toboggan Glacier (1905)
  • Toboggan Glacier (2008)
  • Muir Inlet (1895)
  • Muir Inlet (2005)

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