Document Type
Article
Publication Title
Annals of Glaciology
Publisher
International Glaciological Society
Publication Date
2009
Abstract
We conducted two-dimensional continuous multi-offset georadar surveys on Bench Glacier, south-central Alaska, USA, to measure the distribution of englacial water. We acquired data with a multichannel 25MHz radar system using transmitter–receiver offsets ranging from 5 to 150 m. We towed the radar system at 5-10 kmh-1 with a snow machine with transmitter/receiver positions established by geodetic-grade kinematic differentially corrected GPS (nominal 0.5m trace spacing). For radar velocity analyses, we employed reflection tomography in the pre-stack depth-migrated domain to attain an estimated 2% velocity uncertainty when averaged over three to five wavelengths. We estimated water content from the velocity structure using the complex refractive index method equation and use a three-phase model (ice, water, air) that accounts for compression of air bubbles as a function of depth. Our analysis produced laterally continuous profiles of glacier water content over several kilometers. These profiles show a laterally variable, stratified velocity structure with a low water content (0-0.5%) shallow layer (20-30 m) underlain by high water content (1-2.5%) ice.
DOI
10.3189/172756409789097540
Rights
© Bradford et al
Comments
Link to publisher's website: http://www.igsoc.org/