Uppermost crustal structure regulates the flow of the Greenland Ice Sheet

G A Jones,M Schimmel,A M G Ferreira,A Berbellini,A Morelli,B Kulessa

doi:10.1038/s41467-021-27537-5

Abstract

The flow of the Greenland Ice Sheet is controlled by subglacial processes and conditions that depend on the geological provenance and temperature of the crust beneath it, neither of which are adequately known. Here we present a seismic velocity model of the uppermost 5 km of the Greenlandic crust. We show that slow velocities in the upper crust tend to be associated with major outlet glaciers along the ice-sheet margin, and elevated geothermal heat flux along the Iceland hotspot track inland. Outlet glaciers particularly susceptible to basal slip over deformable subglacial sediments include Jakobshavn, Helheim and Kangerdlussuaq, while geothermal warming and softening of basal ice may affect the onset of faster ice flow at Petermann Glacier and the Northeast Greenland Ice Stream. Interactions with the solid earth therefore control the past, present and future dynamics of the Greenland Ice Sheet and must be adequately explored and implemented in ice sheet models.

Highlights

The flow of the Greenland Ice Sheet is controlled by subglacial processes and conditions that depend on the geological provenance and temperature of the crust beneath it, neither of which are adequately known
The Greenlandic crust primarily comprises an Archaean and early Proterozoic crystalline basement (Fig. 1), which was formed during a series of orogenic events that later stabilised to form a key component of the Laurentian shield[2]
From late April to September we observe a reduction in the number of sources originating in the Denmark Strait with secondary sources of Rayleigh waves observed at periods shorter than 4 s (Supplementary Fig. 1)

Summary

Introduction

The flow of the Greenland Ice Sheet is controlled by subglacial processes and conditions that depend on the geological provenance and temperature of the crust beneath it, neither of which are adequately known. The basal geological conditions beneath an ice sheet or glacier are a fundamental control on ice flow with the substrate and the presence of liquid water being a key prerequisite for fast ice flow. Successive rifting events during the late Devonian to earliest Carboniferous resulted in the development of sedimentary basins to the west and east of Greenland and culminated in the opening of the Labrador Sea in ~ 62 Ma and the North Atlantic in ~ 56 Ma2. Till has been observed beneath the North-East Greenland Ice Stream, Greenland’s only ice stream, but the sedimentary source rocks have yet to be identified[16]. Where any till was observed, it was entrained in the ice and limited to a few decimetres[17]

Methods

Results

Conclusion