Direct measurements of ice-shelf bottom melting rates by phase sensitive radar

This paper describes the novel technique of using a phase-sensitive radio-echo system to determine the basal melt rate along a short profile near Halley Station on the Brunt Ice Shelf. After an interval of nine days the change in the thickness of ice, between a near surface reflecting horizon and the ice-shelf base, was measured. The utilization of internal reflectors as a reference horizon corrects for the effects of accumulation and densification that might occur over the measurement interval. During the nine-day interval the ice shelf thinned by 0.032 + or - 0.004 m, the strain rate contribution to this thinning was 0.003 + or - 0.001 m, giving a localized melt rate of 1.17 + or - 0.17 m/yr. Our measured value agrees well with a traditional continuitymethod. The accuracy of the phase sensitive radar system allows the spatial variation in basal melt-rate to be measured over a short time interval, permitting for the first time a measurement of the seasonal variation in melt rateThis paper describes the novel technique of using a phase-sensitive radio-echo system to determine the basal melt rate along a short profile near Halley Station on the Brunt Ice Shelf. After an interval of nine days the change in the thickness of ice, between a near surface reflecting horizon and the ice-shelf base, was measured. The utilization of internal reflectors as a reference horizon corrects for the effects of accumulation and densification that might occur over the measurement interval. During the nine-day interval the ice shelf thinned by 0.032 + or - 0.004 m, the strain rate contribution to this thinning was 0.003 + or - 0.001 m, giving a localized melt rate of 1.17 + or - 0.17 m/yr. Our measured value agrees well with a traditional continuity method. The accuracy of the phase sensitive radar system allows the spatial variation in basal melt-rate to be measured over a short time interval, permitting for the first time a measurement of the seasonal variation in melt rate

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