The Unpredictable Surge of Glaciers

During most of their lives, surge glaciers behave like normal glaciers, traveling perhaps only a couple of inches per day. However, at [#highlight2]intervals[/highlight2] of 10 to 100 years, these glaciers move forward up to 100 times faster than usual. The surge often progresses along a glacier like a great wave, proceeding from one section to another. Subglacial streams of melt water pressure under the glacier might lift it off its bed, overcoming the friction between ice and rock, thus freeing the glacier, which rapidly slides downhill. Surge glaciers also might be influenced by the climate, volcanic heat, or earthquakes.

Some 800 years ago, Alaska’s Hubbard Glacier advanced toward the sea, retreated, and advanced again 500 years later. Since 1895, this seventy-mile-long river of ice has been flowing steadily toward the Gulf of Alaska at a rate of approximately 200 feet per year. In June 1986, however, the glacier surged ahead as much as 47 feet a day. Meanwhile, a western tributary, called Valerie Glacier, advanced up to 112 feet a day. Hubbard’s surge closed off Russell Fiord with a formidable ice dam, whose caged waters threatened the town of Yakutat.

About 20 similar glaciers around the Gulf of Alaska are heading toward the sea. If enough surge glaciers reach the ocean and raise sea levels, a flood of ice would surge into the Southern Sea. The additional sea ice floating toward the tropics would increase Earth’s albedo and lower global temperatures, perhaps enough to initiate a new ice age.