November 27th, 2012 by Joshua S Hill
The spectacular Columbia Glacier in Alaska is expected to halt its retreat in 2020 when it reaches a new stable position approximately 15 miles upstream from the stable position it had held prior the 1980s.
Currently 425 square miles, the multi-branched Columbia Glacier will halt at a new stable position in 2020, and measuring in at 26 miles long. First documented in 1794 at 41 miles in length, it currently measures somewhere around 34 miles in length.
The halt is predicted using computer models mapping the retreat under current warming conditions, conducted under the leadership of William Colgan of the CU-Boulder headquartered Cooperative Institute for Research in Environmental Sciences.
After witnessing the imagery of Columbia Glacier’s epic retreat as documented in James Balog’s collection of time-lapse photography of disappearing glaciers around the world, Colgan decided to attempt to answer when the glacier would halt its retreat.
Colgan and his team used computer models to document the current and historical activity of the Columbia Glacier, and upon finding the most accurate simulated representation, they ran the simulation into the future to witness the predicted changes.
They found that the terminus of the glacier will retreat into water around 2020 that is sufficiently shallow to proivde a stable position through the rest of the century.
The current rate of icebergs calving into the ocean has increased, says Colgan, due to warmer air temperatures in the region. “Presently, the Columbia Glacier is calving about 2 cubic miles of icebergs into the ocean each year — that is over five times more freshwater than the entire state of Alaska uses annually,” he said. “It is astounding to watch.”
The fact that the Columbia Glacier is now expected to halt retreat has surprised many scientists, who expected that glaciers would continue to retreat, adding easily definable amounts of freshwater to the oceans.
“Many people are comfortable thinking of the glacier contribution to sea level rise as this nice predictable curve into the future, where every year there is a little more sea level rise, and we can model it out for 100 or 200 years,” Colgan said.
“I think the hope was that once we saw climate change happening, we could act to prevent some irreversible consequences,” Colgan added, “but now we are only about eight years out from this retreat finishing — it is really sad. There is virtually no chance of the Columbia Glacier recovering its pre-retreat dimensions on human time-scales.”
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