C028-0014
Ice sheet surface velocity determination from ICESat-2 repeat tracks

Thursday, 10 December 2020
Poster
Canyon Breyer, Scripps Institution of Oceanography, La Jolla, CA, United States, Grace Barcheck, Cornell University, Earth and Atmospheric Sciences, Ithaca, NY, United States, Rodrigo Gomez-Fell, University of Canterbury, Christchurch, New Zealand, Trevor Hillebrand, Los Alamos National Laboratory, Los Alamos, NM, United States, Benjamin H Hills, Applied Physics Laboratory University of Washington, Polar Science Center, Seattle, WA, United States, Lynn M Kaluzienski, University of Maine, School of Earth and Climate Sciences, Orono, ME, United States, Joseph Martin, University of Victoria, Victoria, BC, Canada, David Polashenski, University of Alaska Fairbanks, Fairbanks, AK, United States and Daniel Shapero, University of Washington, Applied Physics Laboratory, Seattle, WA, United States
Abstract:
Improved understanding and forecasting of sea-level rise due to the changing cryosphere require regular high-resolution observations of ice-sheet motion. We present a methodology to calculate short repeat-time ice-sheet surface velocity using the new Advanced Topographic Laser Altimeter System aboard the ICESat-2 satellite. We use cross-correlation of altimetric time series from successive ground tracks to determine along-track displacement of surface elevation features over the satellite’s 91-day revisit period, allowing us to estimate surface velocity between repeats. We demonstrate our methodology on Foundation Ice Stream (FIS), Antarctica, where the ice flow direction is well-aligned with the satellite tracks. Velocity resolution is initially limited by spacing of along-track data points. The pre-processed ICESat-2 land ice height product (ATL06) has a nominal along-track resolution of 20 m, yielding an along-track velocity resolution of ~80 m/year when comparing two subsequent orbit cycles. We improve along-track velocity determination by generating an analogous land ice height product with 5-m sample spacing from ATL03 point clouds, yielding velocity resolution of ~20 m/year, and by implementing sub-sample determination of correlation peaks. The along-track velocities obtained using this technique for fast-moving regions of FIS and its ice shelf are broadly similar to along-track velocities extracted from the MEaSUREs Antarctic Surface Velocity dataset. Velocity determination for slower moving ice is less successful. Additional analysis of intersecting ground tracks to calculate a two-dimensional velocity field is forthcoming.

We are developing an open-source Python toolkit that will integrate the ICESat-2 data retrieval package Icepyx to enable users to calculate updated velocities with a reproducible workflow each time new data becomes available. This tool will allow for more frequent observation of along-track changes in surface ice-sheet dynamics over a broader area of the polar regions than previously possible.

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