Surge (glacier)

Glacial surges are short-lived events where the flow velocity on a portion of a glacier can increase up to 100 times faster than normal during a few months or years. It is associated with an important transportation of ice mass down-glacier, often but not always causing the advance of the glacier front. Surge events are likely an extreme case of the continuous spectra of glacier instabilities. Surging glaciers cluster around a few areas. High concentrations of surging glaciers occur in the Karakoram, Pamir Mountains, Svalbard, the Canadian Arctic islands, Alaska and Iceland, although overall it is estimated that only one percent of all the world's glaciers ever surge. In some glaciers, surges can occur in fairly regular cycles, with cycle periods commonly ranging from 15 to 100 years or more. In other glaciers, surging remains unpredictable. The period of stagnation and build-up between two surges typically lasts 10 to 200 years and is called the quiescent phase. During this period the velocities of the glacier are significantly lower, and the glaciers can retreat substantially.