Abstract
Melting at the base of the Antarctic Ice Sheet influences ice dynamics and our ability to recover ancient climatic records from deep ice cores. Basal melt rates are affected by geothermal flux, one of the least constrained properties of the Antarctic continent. Estimates of Antarctic geothermal flux are typically regional in nature, derived from geological, magnetic or seismic data, or from sparse point measurements at ice core sites. We analyse ice-penetrating radar data upstream of South Pole revealing a ~100 km long and 50 km wide area where internal ice sheet layers converge with the bed. Ice sheet modelling shows that this englacial layer configuration requires basal melting of up to 6 ± 1 mm a−1 and a geothermal flux of 120 ± 20 mW m−2, more than double the values expected for this cratonic sector of East Antarctica. We suggest high heat producing Precambrian basement rocks and hydrothermal circulation along a major fault system cause this anomaly. We conclude that local geothermal flux anomalies could be more widespread in East Antarctica. Assessing their influence on subglacial hydrology and ice sheet dynamics requires new detailed geophysical observations, especially in candidate areas for deep ice core drilling and at the onset of major ice streams.
Highlights
The East Antarctic Ice Sheet drains to the coast through conduits of fast flowing ice, known as ice streams, from an interior dominated by slow moving ice of the high, cold, polar-desert
The adjacent West Antarctic region is predicted by many studies to be a region of elevated geothermal flux[5,7,36,37], linked to the existence of a major Cretaceous to Cenozoic rift system[38]
Hot mantle as the direct source for the observed geothermal anomaly is unlikely given the localised area of identified ice sheet melting and low background geothermal flux values we found
Summary
The East Antarctic Ice Sheet drains to the coast through conduits of fast flowing ice, known as ice streams, from an interior dominated by slow moving ice of the high, cold, polar-desert. We examined new radar data collected as part of the ESA PolarGAP campaign over the South Pole region[12] (Fig. 1a and Supplementary Material 1) This data provides a direct measurement of ice thickness, revealing major subglacial basins extending from the Weddell Sea over 750 km into the interior of East Antarctica (Fig. 1a). Upstream of South Pole, close to the ice divide between the Foundation and Beardmore Glacier catchments, ice flow is slow (Fig. 1b) allowing examination of basal processes using ice sheet internal layering (Fig. 2) This is an area of particular interest as models suggest it may contain some of the planet’s oldest ice, preserving records of important climatic transitions[14]. Ice flow speeds[16] rather than elevated geothermal flux, supported by evidence of so-called organised flow[13] and a buried shear margin[16] close to South Pole (Fig. 1b)
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