Glacier-bed characteristics of midtre Lovénbreen, Svalbard, from high-resolution seismic and radar surveying

We conducted a seismic and radar survey of the central part of midtre Lovenbreen, a small, polythermal valley glacier in Svalbard. We determined the physical properties of the material beneath the glacier by measuring the reflection coefficient of the bed by comparing the energy of the primary and multiple reflections, and deriving the acoustic impedance. By making reasonable assumptions about the properties of the basal ice, we determined the acoustic impedance of the bed material as (6.78 +/- 1.53) x 10(6) kg m(-2) s(-1). We interpret the material beneath the glacier to be permafrost with up to 50% ice, and we speculate that the material may be frozen talus similar to a deposit observed directly by others beneath another Svalbard glacier. The implication for midtre Lovenbreen is that the basal material beneath the present glacier is not able to support fast flow. We conclude that midtre Lovenbreen has most likely had limited capability for faster flow in the past, with motion dominated by internal deformation. Midtre Lovenbreen is used as a 'study glacier' for the scientific community in Svalbard, and a large number of studies have been based there. Our results show that it cannot be used as an analogue for larger glaciers in Svalbard, having distinct basal boundary conditions.

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