Glacier surge at Usherbreen, Svalbard

Abstract

Usherbreen started to surge in 1978, and the front has advanced 1.5 km and covered an area of 4.5 km². During the first two years the front advanced more than 1 m/d, and the front was still advancing 0.15— 0.20m/d in 1985, seven years after the start. The mean gradient of the lower 7 km decreased from 3.3 grad. to 1.8 grad. during the surge. The volume of ice transported down the glacier from higher to lower parts during the surge was 815 x 10⁶m³. which is almost 20% of the total glacier volume. Old icecored ridges in front of the glacier were reactivated, and the whole ridge system was pushed forward, in the summer of 1985 at a speed of about 0.05 m/d. Parts of the ridge system were moved 200 m during this surge. New ridges were developed on the flat sandur in front of the old ridge system. This demonstrates that the glacier advanced further than in any previous surge.