Columbia Glacier Decline Reaches Mid-way Point

Alaska's Columbia Glacier has shrunk in length by 9 miles since 1980 and has reached the halfway point of its expected retreat, a new study reports.

The glacier is now discharging into Prince William Sound nearly 2 cubic miles of ice annually, the equivalent of 100,000 ships packed with ice, each 500 feet long. Researchers expect the glacier to retreat another 9 miles in the next 15 to 20 years.

The thinning glacier is currently the single largest glacial contributor to sea level in North America. It produces about 10 percent of the water volume entering the sea from all Alaskan glaciers each year, said Tad Pfeffer, associate director of the Boulder Institute of Arctic and Alpine Research at the University of Colorado.

The glacier is sliding about 80 feet a day, making it one of the fastest moving glaciers in the world. The Columbia Glacier is about three miles wide in places and up to 3,000 feet thick, but in the past 25 years, parts of it have thinned by up to 1,300 feet.

A slow warming trend that began in the Northern Hemisphere about 500 years ago is believed to be influencing the retreat of the Columbia Glacier and other similar Alaskan glaciers that flow out into the sea, called tidewater glaciers.

"Up until about 50 years ago, the perception was that Greenland and Antarctica were essentially monolithic pancakes of ice," Pfeffer said. "We now understand that these large ice masses are made up of very different sub-regions that respond uniquely to climate forcing."

--Ker Than

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