Evidence for a palaeo-subglacial lake on the Antarctic continental shelf

Gerhard Kuhn,Werner Ehrmann,Claus-Dieter Hillenbrand,Steffen Wiers,Thomas Frederichs,Johann P Klages,José M Mogollón,Frank O Nitsche,James A Smith,Sabine Kasten

doi:10.1038/ncomms15591

Abstract

Subglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized. Here we present evidence for a palaeo-subglacial lake on the Antarctic continental shelf. A distinct sediment facies recovered from a bedrock basin in Pine Island Bay indicates deposition within a low-energy lake environment. Diffusive-advection modelling demonstrates that low chloride concentrations in the pore water of the corresponding sediments can only be explained by initial deposition of this facies in a freshwater setting. These observations indicate that an active subglacial meltwater network, similar to that observed beneath the extant ice sheet, was also active during the last glacial period. It also provides a new framework for refining the exploration of these unique environments.

Highlights

Subglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized
Modelling suggests that subglacial lakes were more widespread in Antarctica during the last glacial maximum (LGM; 23–19 ka before present (BP)) when grounded ice had extended farther onto the continental shelf[12]
The low chloride concentrations measured in the fine-grained sediments of basal Unit 3 are interpreted to indicate freshwater conditions during its deposition

Summary

Introduction

Subglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized. Diffusive-advection modelling demonstrates that low chloride concentrations in the pore water of the corresponding sediments can only be explained by initial deposition of this facies in a freshwater setting These observations indicate that an active subglacial meltwater network, similar to that observed beneath the extant ice sheet, was active during the last glacial period. One alternative to the logistical and technical challenges of in situ lake drilling[16] that can address some of the objectives of subglacial lake exploration is the investigation of subglacial lakes that once existed beneath former ice sheets[17] This offers significant advantages because we can obtain a more complete understanding of the bed properties (that is, geology and topography) and can sample and analyse the sediments without complex logistics. Coring at Lake Whillans recovered a soft diamicton, interpreted as a subglacial till deposited during intermittent ice-stream grounding phases that followed lake drainage events, but no subglacial lake sediments[9]

Methods

Results

Conclusion