Thermally induced icequakes detected on blue ice areas of the East Antarctic ice sheet

Over a year of seismic observations, similar to 5000 short duration icequakes were detected by a permanent broadband station installed at the Princess Elisabeth base, located similar to 180 km inland in eastern Dronning Maud Land, East-Antarctica. Icequake detection via seismic waveform pattern recognition indicates the presence of two dominating clusters of events, totalizing similar to 1500 icequakes. The corresponding icequake locations point towards two distinct zones of outcropping blue ice areas (BIAS) located respectively at 4 and 1 km from the seismic station, both on the leeward side of a nunatak protruding through the ice sheet. The temporal occurrence of these icequakes suggests a close genetic link with thermal contraction of ice caused by significant surface cooling controlled, in summer by variations in diurnal solar radiation and in winter by strong cooling during cold katabatic regimes. Further analysis demonstrates the dependence of these icequakes on the absolute surface temperature and on its temporal change. Besides providing information on the ice fracture mechanics and rheology, investigations of thermal icequakes may be regarded as a ground-based proxy for the monitoring of the thermal state of BIAS, and characterization of ice-sheet ablation zones.