Alaska's Columbia Glacier continues on disintegration course

December 07, 2005

Alaska's rapidly disintegrating Columbia Glacier, which has shrunk in length by 9 miles since 1980, has reached the mid-point of its projected retreat, according to a new University of Colorado at Boulder study.

Tad Pfeffer, associate director of CU-Boulder's Institute of Arctic and Alpine Research, said the glacier is now discharging nearly 2 cubic miles of ice annually into the Prince William Sound, the equivalent of 100,000 ships packed with ice, each 500 feet long. The tidewater glacier -- which has its terminus, or end, in the waters of the Prince William Sound -- is expected to retreat an additional 9 miles in the next 15 years to 20 years before reaching an equilibrium point in shallow water near sea level, he said.

Pfeffer presented his latest findings at a news briefing at the fall meeting of the American Geophysical Union Dec. 5 to Dec. 9 in San Francisco. Pfeffer, CU-Boulder doctoral student Shad O'Neel and other researchers from CU-Boulder and around North America have been monitoring the glacier with time-lapse photography, aerial photography, satellites, seismometers, lasers and other instruments.

The Columbia Glacier is now the single largest glacial contributor to sea level in North America, producing about 10 percent of the water volume entering the sea from all Alaskan glaciers each year, said Pfeffer. Sliding roughly 80 feet a day, the Columbia Glacier is among the world's fastest-moving glaciers and the last of Alaska's 51 tidewater glaciers to exhibit a drastic retreat.

The glacier's retreat appears to be due to a combination of complex physical processes, he said. "The start of the retreat in 1980 is not the direct result of global warming, but was triggered by longer-term warming," said Pfeffer. "The Columbia Glacier, like all Alaska glaciers, is melting at an increased rate, but the enormous volume of loss accompanying the retreat is much greater than melt alone."

The retreat of the Columbia Glacier and Alaska's other tidewater glaciers are believed to be influenced by a slow warming trend that began in the Northern Hemisphere about 500 years ago, he said. The Muir Glacier in Alaska's Glacier Bay, for example, began its retreat in the late 1800s, according to researchers.

But the Columbia Glacier, which is about three miles wide in places and up to 3,000 feet thick, has thinned up to 1,300 feet in places during the past 25 years. The thinning is believed to be caused, in part, by seawater pressure floating the submerged glacier terminus slightly and "stretching it like taffy" as the glacier speed has increased, he said.

"When tidewater glaciers thin to a critical level, they seem to reach a point where they speed up discharging ice into the ocean and can't slow down," said Pfeffer, who is also an associate professor in CU-Boulder's engineering college. Pfeffer said he believes the ongoing retreat of the Columbia Glacier will eventually create a vast fjord rivaling the spectacular Glacier Bay.

The ongoing research on the Columbia Glacier retreat can be used as a model for the current behavior of glaciers in Greenland and Antarctica, where more than 90 percent of the Earth's ice is locked up, he said. Greenland and Antarctica are believed by scientists to be major contributors to global sea rise.

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

The Columbia Glacier has been under intense scrutiny since the late 1970s, when the U.S. Geological Survey determined that a marked increase in its calving rate might pose a threat to shipping lanes in Prince Williams Sound, site of the devastating 1989 Exxon Valdez oil spill. The initial USGS studies were begun by glaciologist Mark Meier, who came to CU-Boulder in 1986 as INSTAAR's first director and who remains on the faculty as an emeritus professor.

While climate-forcing events like the warming underway at high latitudes of Earth may appear to be occurring in small steps, the ultimate response of glaciers and other parts of the environment may be significantly larger and faster, Pfeffer said. "High latitudes respond to climate change in tricky and very unpredictable ways."
-end-
The research was funded in part by the National Science Foundation and the U.S. Geological Survey.

University of Colorado at Boulder

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.