Multisystem Synthesis of Radar Sounding Observations of the Amundsen Sea Sector From the 2004–2005 Field Season

Winnie Chu,Dustin M Schroeder,Duncan A Young,Riley Culberg,Andrew M Hilger,Helene Seroussi,Donald D Blankenship,David G Vaughan,Thomas M Jordan

doi:10.1029/2021jf006296

Abstract

The Amundsen Sea Embayment of the West Antarctic Ice Sheet contains Thwaites and Pine Island Glaciers, two of the most rapidly changing glaciers in Antarctica. To date, Pine Island and Thwaites Glaciers have only been observed by independent airborne radar sounding surveys, but a combined cross‐basin analysis that investigates the basal conditions across the Pine Island‐Thwaites Glaciers boundary has not been performed. Here, we combine two radar surveys and correct for their differences in system parameters to produce unified englacial attenuation and basal relative reflectivity maps spanning both Pine Island and Thwaites Glaciers. Relative reflectivities range from −24.8 to +37.4 dB with the highest values beneath fast‐flowing ice at the ice sheet margin. By comparing our reflectivity results with previously derived radar specularity and trailing bed echoes at Thwaites Glacier, we find a highly diverse subglacial landscape and hydrologic conditions that evolve along‐flow. Together, these findings highlight the potential for joint airborne radar analysis with ground‐based seismic and geomorphological observations to understand variations in the bed properties and cross‐catchment interactions of ice streams and outlet glaciers.

Highlights

The contribution of potentially unstable marine ice sheet sectors is one of the major sources of uncertainty in projections of sea-level rise (IPCC, 2013)
The AGASEA data were collected at Thwaites Glacier (TG) using the 60 MHz center frequency, 15 MHz bandwidth High Capability Airborne Radar Sounder (HiCARS) system (Peters et al, 2007)
We process both channels with 10 coherent summations and 5 incoherent averages using HiCARS processing parameters that match those used in prior studies of unfocused AGASEA data (Schroeder, Blankenship, Young, & Quartini, 2014)

Summary

Introduction

The contribution of potentially unstable marine ice sheet sectors is one of the major sources of uncertainty in projections of sea-level rise (IPCC, 2013). Airborne radar echo sounding is one of the powerful geophysical methods used to investigate the subglacial environment at a catchment-scale (Dowdeswell & Evans, 2004). Changes in reflectivity have been used to infer variations in basal thermal state (Chu et al, 2018; MacGregor et al, 2016), basal roughness (e.g., Jordan et al, 2017), and bed lithology (e.g., Siegert et al, 2016). Descriptions of bed echo character, such as specularity content and trailing bed echo ( known as cross-track energy), enable further investigations on subglacial drainage geometry (e.g., Schroeder et al, 2013) and basal roughness (e.g., Young et al, 2016)

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Discussion

Conclusion