Abstract
AbstractHere we use polarimetric measurements from an Autonomous phase-sensitive Radio-Echo Sounder (ApRES) to investigate ice fabric within Whillans Ice Stream, West Antarctica. The survey traverse is bounded at one end by the suture zone with the Mercer Ice Stream and at the other end by a basal ‘sticky spot’. Our data analysis employs a phase-based polarimetric coherence method to estimate horizontal ice fabric properties: the fabric orientation and the magnitude of the horizontal fabric asymmetry. We infer an azimuthal rotation in the prevailing horizontalc-axis between the near-surface (z≈ 10–50 m) and deeper ice (z≈ 170–360 m), with the near-surface orientated closer to perpendicular to flow and deeper ice closer to parallel. In the near-surface, the fabric asymmetry increases toward the center of Whillans Ice Stream which is consistent with the surface compression direction. By contrast, the fabric orientation in deeper ice is not aligned with the surface compression direction but is consistent with englacial ice reacting to longitudinal compression associated with basal resistance from the nearby sticky spot.
Highlights
IntroductionThere are two components to ice-sheet motion: internal deformation (governed by ice rheology) and basal sliding (governed by basal properties and subglacial hydrology)
There are two components to ice-sheet motion: internal deformation and basal sliding
The goal of this study is to assess the potential of using the Autonomous phase-sensitive Radio-Echo Sounder (ApRES) and the polarimetric coherence method to estimate ice fabric within ice streams
Summary
There are two components to ice-sheet motion: internal deformation (governed by ice rheology) and basal sliding (governed by basal properties and subglacial hydrology). Our understanding of ice fabric within the polar ice sheets is primarily informed by measurements from ice cores underneath ice divides and domes, which have low ice velocities (Wang and others, 2002; Fujita and others, 2006; Montagnat and others, 2014). This geographic limitation on direct observations of ice fabric limits our understanding of how fabric impacts ice dynamics and suggests a need for new geophysical methods for investigating ice fabric and its dependence and influence on ice flow across different flow regimes. The ApRES has recently been used to conduct polarimetric radar sounding measurements in complex flow regions, with Brisbourne and others (2019) focusing on ice rises in the Weddell sea sector of Antarctica
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