The findings represent more than 25 years of study of the glacier by CU-Boulder Emeritus Professor Mark Meier of the Institute for Arctic and Alpine Research.
Meier will present his findings Tuesday Dec. 11, at the fall meeting of the American Geophysical Union in San Francisco, Calif.
Located near Valdez, the Columbia Glacier calves icebergs into Prince William Sound. The glacier has been under intense study since the late 1970s, when the U.S. Geological Survey determined that a marked increase in its calving rate might pose a risk to shipping lanes in the sound, site of the devastating 1989 Exxon Valdez oil spill.
The Columbia Glacier is a tidewater glacier, which means its terminus rests on bedrock about a thousand feet below sea level.
In 1977, the glacier was 41.3 miles long and, at its terminus, was moving at 1.3 miles per year, said Meier. By 1999, the glacier’s length had decreased to 33.5 miles, but its speed at the terminus had increased to 5.5 miles per year, or more than 80 feet per day.
"Over the past two decades, the glacier retreated just under 8 miles," said Meier "Our models suggest a further retreat of nearly 10 miles over approximately the next decade, meaning that the rate of retreat will essentially double."
The glacier has been thinning at its terminus at an advanced rate over the past twenty years. As the river of ice thins it becomes lighter, and other forces begin to contribute to its flow.
Tremendous pressure created by millions of tons of ice melts some of the ice underneath. This water under pressure acts like a hydraulic system, reducing friction between the glacier and the ground beneath, and allowing the glacier to flow faster, said Meier, former director of INSTAAR.
The bottom of the glacier is essentially very close to floatation, according to Meier, meaning that this area is close to being completely supported by the water underneath.
"The interesting thing here is the relationship between rate of retreat and calving speed – or how fast icebergs break off of the glacier at its terminus," said Meier. "The faster the glacier calves, the faster ice will flow to the terminus to replace what is lost. However, the terminus of the glacier is currently in deeper water than it once was and it is thinner on the whole."
Due to these factors – speed from buoyancy created by water underneath, faster calving in the deep water and a thinner terminus – the glacier is calving faster than precipitation can replenish its supply of ice. The net effect is that the entire Columbia Glacier is receding faster and faster, he said.
"Usually we use simple laminar flow models that assume a steady rate of flow at all points along the glacier. These models don’t take into account the dynamics of what’s going on at the terminus, which is quite a lot," Meier said.
Meier joked that if his predictions are correct, a new fjord, possibly to be named "Port Columbia" may be formed within the next few decades.
Co-authors on the paper, titled, "The Past and Future Dynamics of the Columbia Glacier, Alaska" are CU-Boulder student/faculty Research Assistant Josh Cohn, INSTAAR Associate Director and civil, architectural and environment engineering Assistant Professor Tad Pfeffer and Robert Krimmel of the U.S. Geological Survey.