Assessing the continuity of the blue ice climate record at Patriot Hills, Horseshoe Valley, West Antarctica

Kate Winter,Christopher J Fogwill,David E Sugden,Robert G Bingham,Neil Ross,Stuart A Dunning,Chris S M Turney,John Woodward,Shasta M Marrero,Nicholas R Golledge,Andrew S Hein

doi:10.1002/2015gl066476

Abstract

AbstractWe use high‐resolution ground‐penetrating radar (GPR) to assess the continuity of the Blue Ice Area (BIA) horizontal climate record at Patriot Hills, Horseshoe Valley, West Antarctica. The sequence contains three pronounced changes in deuterium isotopic values at ~18 cal ka, ~12 cal ka, and ~8 cal ka. GPR surveys along the climate sequence reveal continuous, conformable dipping isochrones, separated by two unconformities in the isochrone layers, which correlate with the two older deuterium shifts. We interpret these unconformities as discontinuities in the sequence, rather than direct measures of climate change. Ice sheet models and Internal Layer Continuity Index plots suggest that the unconformities represent periods of erosion occurring, as the former ice surface was scoured by katabatic winds in front of mountains at the head of Horseshoe Valley. This study demonstrates the importance of high‐resolution GPR surveys for investigating both paleoflow dynamics and interpreting BIA climate records.

Highlights

With a capacity to resolve internal layering within ice, ground penetrating radar (GPR) has transformed our ability to study and interpret historic changes in ice flow [Paren and Robin, 1975; Daniels et al, 1988; Fujita et al, 1999; Rippin et al, 2003, 2006; Woodward andKing, 2009; Sime et al, 2011; Drews et al, 2013]
Radar-detected stratigraphic relationships analyzed in conjunction with deuterium isotope records, ice-sheet model simulations and internal layer continuity analysis at the Patriot Hills
Blue Ice Area (BIA), West Antarctica, indicate the following: (1) stable periods of snow accumulation and ice flow have been interrupted by episodes of significant erosion, which have resulted in unconformities within the otherwise conformable stratigraphic record and (2)

Summary

Introduction

With a capacity to resolve internal layering within ice, ground penetrating radar (GPR) has transformed our ability to study and interpret historic changes in ice flow [Paren and Robin, 1975; Daniels et al, 1988; Fujita et al, 1999; Rippin et al, 2003, 2006; Woodward andKing, 2009; Sime et al, 2011; Drews et al, 2013]. Km (~0.8%) of the Antarctic continent [Winther et al, 2001] This is perhaps a function of the reduced performance of conventional snowmobile towed GPR surveys in these areas [Spaulding et al, 2013 and Turney et al, 2013], where the speed of travel results in a reduced scan rate relative to the distance traveled, which reduces the ability to image the detailed internal strata of BIAs. Defined as regions of exposed ice with a relatively low surface albedo [Bintanja, 1999], BIAs typically form on the leeward foreground of mountain ranges, where upwards ice flow around the mountains and/or into the mountain front compensates for surface ablation (similar to erosion-induced bedrock uplift in mountains). -called ‘horizontal coring’ offers considerable logistical benefits over vertical coring, such climate records require careful interpretation as the processes that have brought packages of ice to the surface may impact upon their continuity and their paleo significance

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Discussion

Conclusion