Science

Alaska's Columbia glacier to stop retreat in 2020

Alaska's Columbia glacier, one of the fastest-moving glaciers in the world, is expected to cease its retreat by 2020 and stop calving icebergs, which have been boosting sea levels all over the globe.

Will stop 24 km upstream from where it was in 1980s

Alaska's Columbia glacier, one of the fastest-moving glaciers in the world, is expected to cease its retreat in less than 10 years and stop calving icebergs, which have contributed to an increase in sea levels all over the globe.

The glacier, covering some 1,100 square kilometres, has been retreating at a rapid rate starting in the 1980s — something scientists have attributed to global warming. When it was first documented in 1794, it was 66 kilometres in length.  By 1995, that had shortened to 58 kilometres, and 55 in late 2000.

Since 1989, the Co-operative Institute for Research in Environmental Sciences, heaquartered in Boulder, Co., has been monitoring and analyzing the glacier.

That data was put through a computer model, which predicts that it will stabilize in 2020 and stop its retreat. That would mean the glacier would be about 42 kilometres long and about 24 kilometres upstream from where it was in the late 1980s, according to the study published in the online journal Cryosphere, which is supported by the European Geophysical Union.

If the glacier does stabilize, that should slow the massive discharge of ice into ocean water that started in the 1980s and accelerated with the warming trend, the study's authors said.

"Presently, the Columbia glacier is calving about two cubic miles [about 8.3 cubic kilometres] of icebergs into the ocean each year — that is over five times more freshwater than the entire state of Alaska uses annually," said the report's lead author William Colgan. "It is astounding to watch."

Over the years, Colgan’s team has witnessed massive pieces of ice detach from the glacier, made famous in the documentary Chasing Ice, and float away.

Colgan was inspired to examine the glacier more closely due to the work of James Balog, an American photographer, mountaineer and founder of the Extreme Ice Survey (EIS).  Balog is featured in Chasing Ice

The EIS set up cameras at 18 glaciers around the world, from Greenland and Alaska to the Andes and the Himalayas. Through  time-lapse photography, the EIS was able to document the rapid retreat of those glaciers.

Colgan says the results of the computer prediction has surprised scientists who are trying to estimate the rise in sea levels in the future. Those estimates involved calculating the amount of ice cracking away from glaciers.

Colgan says it's evident now that those forecasts will be unpredictable as ice breaking from a single glacier can be "turned on" suddenly and then "turned off" just as rapidly as glaciers stabilize.

Located 150 kilometres east of Anchorage, the Columbia glacier has been the focal point of research into how tidewater glaciers react to a warming climate. 

Water from the glacier flows south out of the Chugach Mountains and towards Prince William Sound.

Since studies began on the glacier there had been hope that its retreat could be stopped much earlier. But Colgan says those hopes are past.

"It is really sad," he said. "There is virtually no chance of the Columbia Glacier recovering its pre-retreat dimensions."

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