Radar-Derived Ice Thickness and Bed Topography Measurements of the Bering-Bagley Glacier System, Alaska

Despite their relatively small size when compared to the planet's large ice sheets, Alaskan glaciers have proven a major contributor to global sea-level rise in response to changing climate. However, substantial uncertainties exist in estimates of regional ice loss for these glaciers due to insufficient measurements of bed elevation and ice thickness. Such metrics are essential in quantifying ice flux, or the rate of ice flow per unit cross-sectional area - information critical to performing ice flow modelling and for determining how particular glaciers will contribute to sea-level rise. Low-frequency (tens of meters wavelength) radar sounding has proven a valuable tool in providing such information for temperate ice masses, where crevasses and englacial heterogeneities such as liquid water provide difficulties in terms of signal scattering and attenuation.

The Bering-Bagley glacial system is of particular interest in terms of Alaskan glacier dynamics due to its characteristic surge behavior. W e present bed elevation and ice thickness measurements for Bering Glacier, along wit h the transition between the the western portion of the Bagley Icefield and Bering Glacier. Data were acquired as part of NASA's Operation IceBridge Alaska using the University of Arizona's chirped long-wavelength radar system, which operates at either a 2.5 MHz center-frequency with a 2.5 MHz bandwidth or a 5 MHz center-frequency with a 5 MHz bandwidth. Additional data were acquired using a monopulse, 2.5 MHz center-frequency radar built at the Geophysical Institute of the University of Alaska at Fairbanks. Subsurface reflectors have been distinguished from off-nadir echoes from surface topography, or " clutter", by simulating surface echoes using a facet-based geometrical optics simulator which employs a regional digital elevation model of topography. We find i ce thickness maxima of approximately 1 km throughout the Bering-Bagley transition zone and along the upper extent of Bering Glacier. This new bed elevation and ice thickness data can help to both determine regional ice flux and also to better understand the role of bed topography on Bering's retreat- surge dynamics .