Radar attenuation and temperature within the Greenland Ice Sheet

Journal of Geophysical Research F: Earth Surface
By: , and 

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Abstract

The flow of ice is temperature-dependent, but direct measurements of englacial temperature are sparse. The dielectric attenuation of radio waves through ice is also temperature-dependent, and radar sounding of ice sheets is sensitive to this attenuation. Here we estimate depth-averaged radar-attenuation rates within the Greenland Ice Sheet from airborne radar-sounding data and its associated radiostratigraphy. Using existing empirical relationships between temperature, chemistry, and radar attenuation, we then infer the depth-averaged englacial temperature. The dated radiostratigraphy permits a correction for the confounding effect of spatially varying ice chemistry. Where radar transects intersect boreholes, radar-inferred temperature is consistently higher than that measured directly. We attribute this discrepancy to the poorly recognized frequency dependence of the radar-attenuation rate and correct for this effect empirically, resulting in a robust relationship between radar-inferred and borehole-measured depth-averaged temperature. Radar-inferred englacial temperature is often lower than modern surface temperature and that of a steady state ice-sheet model, particularly in southern Greenland. This pattern suggests that past changes in surface boundary conditions (temperature and accumulation rate) affect the ice sheet's present temperature structure over a much larger area than previously recognized. This radar-inferred temperature structure provides a new constraint for thermomechanical models of the Greenland Ice Sheet.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Radar attenuation and temperature within the Greenland Ice Sheet
Series title Journal of Geophysical Research F: Earth Surface
DOI 10.1002/2014JF003418
Volume 120
Issue 4
Year Published 2015
Language English
Publisher American Geophysical Union
Publisher location Richmond, VA
Contributing office(s) Geosciences and Environmental Change Science Center
Description 26 p.
First page 1
Last page 26
Online Only (Y/N) N
Additional Online Files (Y/N) N