Bed Topography of Fast-flowing Outlet Glaciers and Ice-sheet Margins

Abstract:

Radar sounding and imaging of fast-flowing glaciers and ice-sheet margins are major challenges in radioglaciology. The extremely rough surfaces and lossy ice near the bed of these areas results in large attenuation of the signals propagating through this ice, making airborne radar sounding of these regions very challenging. High-sensitivity radars with Synthetic Aperture Radar (SAR) processing and cross-track arrays are required to reduce the scattered signals caused by surface clutter to obtain discernable bed echoes. We developed such radars with cross-track arrays and have operated them on both medium- and long-range aircraft. Over the last several years, we have collected data over outlet glaciers in Greenland and Antarctica, and we recently reprocessed data over some of the key glaciers with SAR and array processing algorithms to further reduce surface clutter. We also enhanced the resulting echograms with image processing techniques to bring out weak bed echoes, enabling the generation of both bed topographies and ice thickness estimates for the most challenging parts of these outlet glaciers. In this presentation, we will discuss relevant issues; show sample results of SAR-, array-, and image-processing algorithms; present bed topographies; and discuss what must be done to fully sound and image outlet glaciers and ice-sheet margins.