Abstract
Recent studies have aroused concerns over the potential for ice draining the Weddell Sea sector of West Antarctica to figure more prominently in sea-level contributions should buttressing from the Filchner-Ronne Ice Shelf diminish. To improve understanding of how ice-stream dynamics there evolved through the Holocene, we interrogate Radio-Echo Sounding (RES) data from across the catchments of Institute and Moller Ice Streams (IIS and MIS), focusing especially on the use of internal layering to investigate ice-flow change. As an important component of this work, we investigate the influence that the orientation of the RES acquisition-track with respect to ice flow exerts on internal layering, and find that this influence is minimal unless a RES flight track parallels ice flow. We also investigate potential changes to internal layering characteristics with depth to search for important temporal transitions in ice-flow regime. Our findings suggest that ice in northern IIS, draining the Ellsworth Subglacial Highlands, has retained its present ice-flow configuration throughout the Holocene. This contrasts with less topographically-constrained ice in southern IIS and much of MIS, whose internal layering evinces spatial changes to the configuration of ice flow over the past ~10,000 years. Our findings confirm Siegert et al.’s (2013) inference that fast flow was diverted from Bungenstock Ice Rise during the Late Holocene, and suggest that this may have represented just one component of wider regional changes to ice flow occurring across the IIS and MIS catchments as the West Antarctic Ice Sheet has thinned since the Last Glacial Maximum.
Highlights
Many ice streams draining the West Antarctic Ice Sheet (WAIS) rest on beds below current sea level that deepen inland, rendering them vulnerable to rapid retreat [e.g., Schoof, 2007; Joughin and Alley, 2011; Ross et al, 2012; Favier et al, 2014]
Our findings confirm Siegert et al.’s (2013) inference that fast flow was diverted from Bungenstock Ice Rise during the Late Holocene and suggest that this may have represented just one component of wider regional changes to ice flow occurring across the Institute Ice Stream (IIS) and Möller Ice Stream (MIS) catchments as the West Antarctic Ice Sheet has thinned since the Last Glacial Maximum
We have analyzed in detail the patterns of radio echo-sounded internal ice sheet layering within the Institute and Möller Ice Streams (IIS and MIS), West Antarctica
Summary
Many ice streams draining the West Antarctic Ice Sheet (WAIS) rest on beds below current sea level that deepen inland, rendering them vulnerable to rapid retreat [e.g., Schoof, 2007; Joughin and Alley, 2011; Ross et al, 2012; Favier et al, 2014]. Dynamic instability is further evinced by observations that some ice streams experience spatial migration [Echelmeyer and Harrison, 1999; Catania et al, 2005], dramatic decelerations or “shutdowns” [Retzlaff and Bentley, 1993; Catania et al, 2006], and flow switching or ice stream piracy between neighboring systems [Jacobel et al, 1996; Conway et al, 2002; Vaughan et al, 2008] These phenomena require improved understanding and representation in generation ice sheet models as they aim toward better forecasts of ice sheet response to climatic forcing [cf., Vaughan et al, 2013]. Several recent studies collectively suggest that the WSS may be far more dynamic than previously thought
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