Ground-penetrating radar imaging reveals glacier's drainage network in 3D

Gregory Church,Andreas Bauder,Melchior Grab,Hansruedi Maurer

doi:10.5194/tc-15-3975-2021

Abstract

Abstract. Hydrological systems of glaciers have a direct impact on the glacier dynamics. Since the 1950s, geophysical studies have provided insights into these hydrological systems. Unfortunately, such studies were predominantly conducted using 2D acquisitions along a few profiles, thus failing to provide spatially unaliased 3D images of englacial and subglacial water pathways. The latter has likely resulted in flawed constraints for the hydrological modelling of glacier drainage networks. Here, we present 3D ground-penetrating radar (GPR) results that provide high-resolution 3D images of an alpine glacier's drainage network. Our results confirm a long-standing englacial hydrology theory stating that englacial conduits flow around glacial overdeepenings rather than directly over the overdeepening. Furthermore, these results also show exciting new opportunities for high-resolution 3D GPR studies of glaciers.

Highlights

Glacier movement is the combination of internal ice deformation and basal motion
In alpine glaciers and in Greenland, the subglacial drainage network is fed from surface meltwater that is routed through the englacial drainage network (Fountain and Walder, 1998)
The majority of the ice–bed interface is identifiable as a weak reflection (Fig. 2), indicating that subglacial water is not present

Summary

Introduction

Glacier movement is the combination of internal ice deformation and basal motion. Basal motion comprises both ice sliding over the glacier bed and the deformation of subglacial till (Cuffey and Paterson, 2010). At the beginning of the melt season and with an increased availability of surface meltwater, the subglacial drainage network often experiences an increase in water pressure, since the drainage network cannot adapt quickly enough to the increase in meltwater influx (Iken et al, 1983) During these periods with increased subglacial water pressure, changes in the glacier’s sliding velocity are often observed (Gudmundsson et al, 2000; Sugiyama and Gudmundsson, 2004; Macgregor et al, 2005), and it has been widely documented that increased glacier sliding velocities have the potential to increase the glacier’s mass loss (Zwally et al, 2002; Joughin et al, 2008; Schoof, 2010). Whilst the existence of these variations in ice flow velocities are undisputed, there are limited observations of the hydrological system’s geometry and its temporal variations, hampering a deeper understanding of these seasonal variations (Hart et al, 2015; Church et al, 2020)

Methods

Results

Discussion

Conclusion