Hard rock landforms generate 130\u2009km ice shelf channels through water focusing in basal corrugations

Hafeez Jeofry,Mathieu Morlighem,Martin J Siegert,Prasad Gogineni,Thomas Jordan,Anne Le Brocq,Neil Ross,Alastair G.C Graham,Jilu Li

doi:10.1038/s41467-018-06679-z

Abstract

Satellite imagery reveals flowstripes on Foundation Ice Stream parallel to ice flow, and meandering features on the ice-shelf that cross-cut ice flow and are thought to be formed by water exiting a well-organised subglacial system. Here, ice-penetrating radar data show flow-parallel hard-bed landforms beneath the grounded ice, and channels incised upwards into the ice shelf beneath meandering surface channels. As the ice transitions to flotation, the ice shelf incorporates a corrugation resulting from the landforms. Radar reveals the presence of subglacial water alongside the landforms, indicating a well-organised drainage system in which water exits the ice sheet as a point source, mixes with cavity water and incises upwards into a corrugation peak, accentuating the corrugation downstream. Hard-bedded landforms influence both subglacial hydrology and ice-shelf structure and, as they are known to be widespread on formerly glaciated terrain, their influence on the ice-sheet-shelf transition could be more widespread than thought previously.

Highlights

Satellite imagery reveals flowstripes on Foundation Ice Stream parallel to ice flow, and meandering features on the ice-shelf that cross-cut ice flow and are thought to be formed by water exiting a well-organised subglacial system
The Foundation ice stream (FIS) has its trunk in West Antarctica and a wide complex drainage basin with about half its ice supplied by the Academy Glacier and Support Force ice stream in East Antarctica and the other half from West Antarctica
Numerous “active” subglacial lakes—those that experience outbursts or infilling of water due to periodic change in their hydropotential gradients20,21—exist beneath both Support Force and Academy Glaciers[22], indicating that Foundation Ice Stream is fed with significant volumes of basal water, of East Antarctic origin (Supplementary Figure 1)

Summary

Introduction

Satellite imagery reveals flowstripes on Foundation Ice Stream parallel to ice flow, and meandering features on the ice-shelf that cross-cut ice flow and are thought to be formed by water exiting a well-organised subglacial system. Ice-penetrating radar data show flowparallel hard-bed landforms beneath the grounded ice, and channels incised upwards into the ice shelf beneath meandering surface channels. M-channels are thought to be evidence of a well-organised subglacial-hydrological system, channelized by upward melting into the grounded ice by the basal water As it exits the grounded ice the subglacial water forms a buoyant plume due to being fresher than water within the ice shelf cavity. It entrains the warmer cavity water, and melts the underside of the floating ice to form an upward-incised channel[5], which we refer to as U-channels. We inspect ice-penetrating radar data across the Foundation ice stream (FIS) and Filchner-Ronne Ice Shelf (FRIS) to

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Conclusion