Glacier surges are characterized by cyclical advances related to internal changes in the glacier system, and occur in both terrestrial and tidewater glaciers. The surges are short-lived periods of rapid movement and sometimes advancing terminus, usually lasting somewhat more than 10 years.
Fridtjovbreen during surge 1997 Photo: M. Sund
In Svalbard the surge phase is generally longer than in e.g. Alaska. During the increase in velocity, rates of flow may reach more than 1000 times their normal value. The surge phase is intersected by longer quiescent phases of about 30 - 150 years, during which the glacier teminus is retreating. Surges occur independently of climatic variations, only the durations of the quiescent and surge phase is affected by climatic changes. Surge type glaciers should not be confused with those which are rapidly advancing or have sustained fast flow. The cause of the surge behaviour is still debated.
Surge-type glaciers represent only a small percentage of all glaciers and the phenomenon is highly concentrated in some glaciated regions like Svalbard, Iceland, Greenland, Alaska, the Pamirs and the Andes. Evidence of surging ice streams are believed to be found in Antarctica as well.