Collaborative Research: EAGER: A Dual-Band Radar for Measuring Internal Ice Deformation: a Multipass Ice-Penetrating Radar Experiment on Thwaites Glacier and the McMurdo Ice Shelf
Dual-Band Multipass Radar
This project will develop a new ice-penetrating radar system that can simultaneously map glacier geometry (three-dimensional ice-sheet internal architecture and subglacial topography) and glacier flow (vertical velocity of ice) along repeat profiles. Forecasting ice-sheet contribution to sea level requires an estimate for the initial ice-sheet geometry and the parameters that govern ice flow (ice rheology) and slip across bedrock (bed friction). Existing ice-sheet models cannot independently initialize ice rheology and bed friction from conventional observations of surface velocities and glacier geometry. These non-unique solutions for ice-sheet initial state introduce substantial uncertainty into ice-sheet model simulations of past and future ice-sheet behavior. Spatially-distributed vertical velocities of ice measured by this radar system can be directly compared to simulated vertical velocities produced by glacier models. Thus, this radar technology will allow ice rheology to be constrained independently from bed friction, leading to higher fidelity simulations of past and future ice-sheet behavior and more accurate projections of future sea level. The new radar system will integrate two existing radars (the multi-channel coherent radio-echo depth sounder and the accumulation radar) developed by the Center for the Remote Sensing of Ice Sheets, but also includes new capabilities. An eight-element very high frequency (VHF; 140-215 MHz) array will have sufficient cross-track aperture to swath map internal layers and the ice-sheet base in three dimensions. A single ultra high frequency (UHF; 600-900 MHz) antenna will have the range and phase resolution to map internal layer displacement with 0.25 mm precision. The VHF array will create 3D mappings of layer geometry that enable measurements of vertical velocities by accounting for spatial offsets between repeat profiles and changing surface conditions. The vertical displacement measurement will then be made by determining the difference in radar phase response recorded by the UHF antenna for radar profiles collected at the same locations at different times. The UHF antenna will be dual-polarized and thus capable of isolating both components of complex internal reflections, which should enable inferences of ice crystal orientation fabric and widespread mapping of ice viscosity. Initial deployment of the radar will occur on the McMurdo Ice Shelf and Thwaites Glacier, Antarctica. The dual-band radar system technology and processing algorithms will be developed with versatile extensible hardware and user-friendly software, so that this system will serve as a prototype for a future community radar system.
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