Geophysics and thermodynamics at South Pole Lake indicate stability and a regionally thawed bed

Abstract

Subglacial lakes require a thawed bed either now or in the past; thus, their presence and stability have implications for current and past basal conditions, ice dynamics, and climate. Here, we present the most extensive geophysical exploration to date of a subglacial lake near the geographic South Pole, including radarimaged stratigraphy, surface velocities, and englacial vertical velocities. We use a 1.5-dimensional temperature model, optimized with our geophysical data set and nearby temperature measurements, to estimate past basal-melt rates. The ice geometry, reflected bed-echo power, surface and vertical velocities, and temperature model indicate that the ice-bed interface is regionally thawed, contradicting prior studies. Together with an earlier active-source seismic study, which showed a 32-m deep lake underlain by 150 m of sediment, our results suggest that the lake has been thermodynamically stable through at least the last 120,000 years and possibly much longer, making it a promising prospective site for sediment coring.