Geometric evolution and ice dynamics during a surge of Bakaninbreen, Svalbard

• Published in: Journal of Glaciology
• Main Authors: Murray, Tavi, Dowdeswell, Julian A., Drewry, David J., Frearson, Ian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1998
• Subjects: glacier; Journal of Glaciology; Svalbard
• Online Access: http://dx.doi.org/10.1017/s0022143000002604; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000002604

Abstract Bakaninbreen, Svalbard, started surging in 1985 and developed a steep surge front where fast-moving ice impinged on stagnant non-surging ice. This front, which was 20- 25 m high in 1985, became a steep and heavily crevassed feature about 60 m high. The surge continued through 1986-95. Annual surge-front propagation rate was 1.0 1.8 km a −1 during 1985-89; this rate dropped considerably during 1989 95 and the front became less steep. Front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over-riding appear minor. Ice velocities were slower than the average propagation rate of the front. The surge affected Bakaninbreen in four zones: (1) Upper region where extensive flow, fast propagation rates and negative vertical strain occurred, resulting in widespread crevassing and stranded blocks tens of metres above the post-surge ice surface, (2) Mid-glacier region where initial strong compression was associated with ice thickening which started before the arrivai of the surge front. Horizontal strain rates were very low but vertical strain rates were tip to 300 mmd −1 . As (he front passed, the horizontal velocity increased and about 500 m behind it became extensive. Negative vertical strain and ice down-draw occurred as ice velocities dropped, (3) Surge front where ice velocity was high but vertical strain remained positive associated with compression. (4) Lower region below the iront where only compression occurred, resulting in the formation of a fore bulge, a thickening of the ice of up to 50 m above pre-surge levels. The fore bulge affected the whole 1.7 km below the, now halted, surge front. The glacier has not advanced, Bakaninbreen’s surge was characterized by a long active phase, approximately 10 years, low ice velocities and low basal shear stresses compared to glaciers in lower latitudes, and an indistinct surge termination.