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 lO'm3. 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.