Radar‐Detected Englacial Debris in the West Antarctic Ice Sheet

Kate Winter,John Woodward,Neil Ross,Stuart A Dunning,David E Sugden,Riley Culberg,Matthew J Westoby,Dustin M Schroeder,Martin J Siegert,Andrew S Hein,Shasta M Marrero

doi:10.1029/2019gl084012

Abstract

AbstractStructural glaci‐geological processes can entrain basal sediment into ice, leading to its transportation and deposition downstream. Sediments potentially rich in essential nutrients, like silica and iron, can thus be transferred from continental sources to the ocean, where deposition could enhance marine primary productivity. However, a lack of data has limited our knowledge of sediment entrainment, transfer, and distribution in Antarctica, until now. We use ice‐penetrating radar to examine englacial sediments in the Weddell Sea sector of the West Antarctic Ice Sheet. Radargrams reveal englacial reflectors on the leeside of nunataks and subglacial highlands, where Mie scattering analysis of the reflectors suggests particle sizes consistent with surface moraine sediments. We hypothesize that these sediments are entrained at the thermal boundary between cold and warm‐based ice. Conservative estimates of >130 × 109 kg of englacial sediment in Horseshoe Valley alone suggest that the ice sheet has significant entrainment potential unappreciated previously.

Highlights

Once entrained in glacier ice, sediments, including those rich in essential nutrients like silica and iron, can be transferred from continental sources to the ocean by ice flow, and iceberg production and transport (Death et al, 2014; Hawkings et al, 2014, 2018; Nicholls et al, 2012)
Conservative estimates of >130 × 109 kg of englacial sediment in Horseshoe Valley alone suggest that the ice sheet has significant entrainment potential unappreciated previously
We propose that basal sediments in Horseshoe Valley are entrained within glacial ice through repeated melting and freezing processes at the glacial bed, characteristic of warm‐based ice (Alley et al, 1997; Hubbard & Sharp, 1993)

Summary

Introduction

Once entrained in glacier ice, sediments, including those rich in essential nutrients like silica and iron, can be transferred from continental sources to the ocean by ice flow, and iceberg production and transport (Death et al, 2014; Hawkings et al, 2014, 2018; Nicholls et al, 2012). This can create layers of ice‐rafted debris in deep‐sea deposits (Leventer et al, 2006; Pierce et al, 2011), such as the North Atlantic Heinrich layers (Heinrich, 1998). Recent improvements in the collection and processing of IPR data allow us to investigate mechanisms of sediment entrainment and transfer in the Weddell Sea sector of the West Antarctic Ice Sheet (WAIS)

Methods

Results

Discussion

Conclusion