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1. Decoding ice sheet behavior using englacial layer slopes: ENGLACIAL REFLECTOR SLOPES

   https://doi.org/10.1002/2017GL073417  

   Holschuh, Nicholas ; Parizek, Byron R. ; Alley, Richard B. ; Anandakrishnan, Sridhar ( June 2017 , Geophysical Research Letters)
2. Radar-detected englacial stratigraphy in the Pensacola Mountains, Antarctica: implications for recent changes in ice flow and accumulation

   https://doi.org/10.3189/2013AoG63A371  

   Campbell, Seth ; Balco, Greg ; Todd, Claire ; Conway, Howard ; Huybers, Kathleen ; Simmons, Christopher ; Vermeulen, Michael ( January 2013 , Annals of Glaciology)

   Abstract We used measurements of radar-detected stratigraphy, surface ice-flow velocities and accumulation rates to investigate relationships between local valley-glacier and regional ice-sheet dynamics in and around the Schmidt Hills, Pensacola Mountains, Antarctica. Ground-penetrating radar profiles were collected perpendicular to the long axis of the Schmidt Hills and the margin of Foundation Ice Stream (FIS). Within the valley confines, the glacier consists of blue ice, and profiles show internal stratigraphy dipping steeply toward the nunataks and truncated at the present-day ablation surface. Below the valley confines, the blue ice is overlain by firn. Data show that upward-progressing overlap of actively accumulating firn onto valley-glacier ice is slightly less than ice flow out of the valleys over the past ∼1200 years. The apparent slightly negative mass balance (-0.25 cm a -1 ) suggests that ice-margin elevations in the Schmidt Hills may have lowered over this time period, even without a change in the surface elevation of FIS. Results suggest that (1) mass-balance gradients between local valley glaciers and regional ice sheets should be considered when using local information to estimate regional ice surface elevation changes; and (2) interpretation of shallow ice structures imaged with radar can provide information about local ice elevationmore »changes and stability.« less
3. A comparison of automated approaches to extracting englacial-layer geometry from radar data across ice sheets

   https://doi.org/10.1017/aog.2020.42  

   Delf, Richard ; Schroeder, Dustin M. ; Curtis, Andrew ; Giannopoulos, Antonios ; Bingham, Robert G. ( April 2020 , Annals of Glaciology)

   Abstract Radar surveys across ice sheets typically measure numerous englacial layers that can often be regarded as isochrones. Such layers are valuable for extrapolating age–depth relationships away from ice-core locations, reconstructing palaeoaccumulation variability, and investigating past ice-sheet dynamics. However, the use of englacial layers in Antarctica has been hampered by underdeveloped techniques for characterising layer continuity and geometry over large distances, with techniques developed independently and little opportunity for inter-comparison of results. In this paper, we present a methodology to assess the performance of automated layer-tracking and layer-dip-estimation algorithms through their ability to propagate a correct age–depth model. We use this to assess isochrone-tracking techniques applied to two test case datasets, selected from CreSIS MCoRDS data over Antarctica from a range of environments including low-dip, continuous layers and layers with terminations. We find that dip-estimation techniques are generally successful in tracking englacial dip but break down in the upper and lower regions of the ice sheet. The results of testing two previously published layer-tracking algorithms show that further development is required to attain a good constraint of age–depth relationships away from dated ice cores. We recommend that auto-tracking techniques focus on improved linking of picked stratigraphy across signal disruptions tomore »enable accurate determination of the Antarctic-wide age–depth structure.« less
4. Interpreting englacial layer deformation in the presence of complex ice flow history with synthetic radargrams

   https://doi.org/10.1017/aog.2019.41  

   Elsworth, Cooper W. ; Schroeder, Dustin M. ; Siegfried, Matthew R. ( January 2020 , Annals of Glaciology)

   Abstract Fast ice flow on the Antarctic continent constitutes much of the mass loss from the ice sheet. However, geophysical methods struggle to constrain ice flow history at depth, or separate the signatures of topography, ice dynamics and basal conditions on layer structure. We develop and demonstrate a methodology to compare layer signatures in multiple airborne radar transects in order to characterize ice flow at depth, or improve coverage of existing radar surveys. We apply this technique to generate synthetic, along-flow radargrams and compare different deformation regimes to observed radargram structure. Specifically, we investigate flow around the central sticky spot of Whillans Ice Stream, West Antarctica. Our study suggests that present-day velocity flowlines are insufficient to characterize flow at depth as expressed in layer geometry, and streaklines provide a better characterization of flow around a basal sticky spot. For Whillans Ice Stream, this suggests that ice flow wraps around the central sticky spot, supported by idealized flow simulations. While tracking isochrone translation and rotation across survey lines is complex, we demonstrate that our approach to combine radargram interpretation and modeling can reveal critical details of past ice flow.
5. Radar‐Detected Englacial Debris in the West Antarctic Ice Sheet

   https://doi.org/10.1029/2019GL084012  

   Winter, Kate ; Woodward, John ; Ross, Neil ; Dunning, Stuart A. ; Hein, Andrew S. ; Westoby, Matthew J. ; Culberg, Riley ; Marrero, Shasta M. ; Schroeder, Dustin M. ; Sugden, David E. ; et al ( September 2019 , Geophysical Research Letters)