InSAR observations of the 1993–95 Bering Glacier (Alaska, U.S.A.) surge and a surge hypothesis

Abstract

Time-varying accelerations were observed on Bagley Icefield during the 1993–95 surge of Bering Glacier, Alaska, U.S.A., using repeat-pass synthetic aperture radar interferometry. Observations were from datasets acquired during winter 1991/92 (pre-surge), winter 1993/94 (during the surge) and winter 1995/96 (post-surge). The surge is shown to have extended 110 km up the icefield from Bering Glacier to within 15 km or less of the flow divide. Acceleration and step-like velocity profiles are strongly associated with an along-glacier series of central phase bull’s-eyes with diameters of 0.5–4 km. These bull’s-eyes are interpreted to represent glacier surface rise/fall events of ∼3–30 cm during 1–3 day observation intervals and indicate possible migrating pockets of subglacial water. We present a surge hypothesis that relates late-summer climate to englacial water storage and thence to the subglacial water dynamics — pressurization, hydraulic jacking, depressurization and migration — suggested by our observations.