The retreat of Alaska’s Columbia Glacier may halt by 2020
after climate change has melted 15 miles of the glacier, relative to its size
in 1794. A computer model predicted that the glacier will reach a stable
position when it is approximately 26 miles long, down from 41 miles.
"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," said William
Colgan of the University of Colorado lead author of the modeling study in a
One iceberg released by the glacier had a tragic history. In
1989, the Exxon Valdez maneuvered to avoid an iceberg calved from the Columbia
Glacier. The ship missed the iceberg, but hit a far larger obstacle…Alaska. The
ship ran aground and coated Prince William Sound and its wildlife in a thick
layer of crude.
By 2020, the waters around the outlet of the Columbia
Glacier may become less dangerous. The shrunken glacier will have reached a region
of shallow coastal water that will help it maintain its integrity until 2100.
Fewer icebergs won’t mean the threat from the glacier will
be gone. The waters of the glacier will have become part of the rising sea
levels that are already being associated with the increased destructive power
of coastal storms. However, the computer model predicts that the contribution
of the glacier, and others like it, will not be constant or easily predictable.
Glaciers’ melting may accelerate or decelerate over a short period of time.
"The variable nature and speed of the life cycle among
glaciers highlights difficulties in trying to accurately predict the amount of
sea level rise that will occur in the decades to come," Colgan said.
"I think the hope was that once we saw climate change
happening, we could act to prevent some irreversible consequences," Colgan
said, "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."
Columbia Glacier, Prince William Sound, Alaska as seen on Google Earth (NOAA, Wikimedia Commons)
Workers clean the beaches of Prince William Sound beaches after the Exxon Valdez oil spill. (NOAA, Wikimedia Commons)