What is a glacier surge?

Asked by Norma

Surge-type glaciers are characterised by flow instabilities, with periods of fast flow followed by long quiescent periods. They are slow moving during their quiescent phases, when they thin and melt in their lower reaches, but accumulate snow and ice in their upper parts. The surge typically lasts 1-10 years, with quiescent phases of 10-100 years in Svalbard. Surge-type glaciers are common in smaller, polythermal glaciers, in places like Svalbard, but typical surging behaviour (repeated periods of rapid ice flow, interspersed with regular duractions of quiet stagnation and slow or no flow) are not generally recognised in Antarctica. Rapid increases of ice flow followed by slower flow have been recognised in some Antarctic Peninsula glaciers following ice-shelf collapse; however, this is likely to have been caused by a different mechanism. For more information and photographs, see the Glaciers Online website.