Surge-front propagation and velocities during the early-1993-95 surge of Bering Glacier, Alaska, USA, from sequential SAR imagery

The initiation and propagation of the 1993-95 surge of Bering Glacier, Alaska, U.S.A., was observed using ERS-1 synthetic aperture radar (SAR) imagery. Images were acquired before and during the surge, between November 1992 and October 1993. Terrain-corrected and co-registered imagery was used to measure the propagation of the surge front. Surface undulations interpreted to be evidence of accelerated flow, indicating surge initiation in late winter, were observed in the 26 March 1993 image. From 19 May to 25 August 1993, the mean propagation velocity of the surge front was 90 in d(-1). The surge reached the terminus shortly after 25 August 1993. The central area of the calving terminus then advanced into proglacial Vitus Lake at a mean rate of 19 in d(-1) between 9 August and 18 October 1993. Feature matching was used to measure discrete velocity vectors between 9 August and 13 September; the vectors were kriged onto a uniform grid and used to compute the principal strain rates. Shattering of the calving front and dramatically increased iceberg calving were accompanied by high compressive strain rates immediately up-glacier from the calving front.