Ice shelf basal melting at the grounding line, measured from seismic observations

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Abstract
Analysis of seismic data provides a new technique to measure basal melting of an ice shelf close to the grounding line. Internal reflections have been observed within the ice on a seismic reflection profile at the grounding line of Ronne Ice Shelf. The changes in ice thickness above and below these reflections have been used in a steady state model to calculate the basal mass flux of the ice shelf soon after the ice begins to float. Strain rates within the ice, calculated during the modeling, agree with values from nearby survey data. The calculated melt rates range between 0 and 7 m yr−1 with an estimated standard error of ±2.4 m yr−1, in reasonable agreement with earlier estimates based on surface glaciological observations. Limitations in the method include the difficulties in determining reflector geometry from a single seismic section and also the limitations imposed by the assumption of steady state. Additional seismic data would greatly reduce these limitations.