Estimation of Ice Basal Reflectivity of Byrd Glacier using RES data

Abstract

Ice basal reflectivity is much needed for the determination of ice basal conditions and for the accurate modeling of ice sheets to estimate future global mean sea level rise. Reflectivity values can be determined from the received radio echo sounding data if the power loss caused by different components along the two-way transmission of electromagnetic waves is accurately compensated. For the large volume of received radio echo sounding data collected over Byrd glacier in 2011-2012 with a multichannel radar system, the spherical spreading loss caused due to two-way propagation, power reduction due to roughness and relative englacial attenuation is compensated to estimate the relative reflectivity values of the Byrd glacier ice base. In order to estimate the scattered incoherent power component due to roughness, the distributions of echo amplitudes returned from the air-firn interface and from the ice – bed interface are modeled to estimate RMS height variations. The englacial attenuation rate for two-way propagation along the ice depth is modeled using the collected radar data. The estimated air-firn interface roughness parameters are relatively cross verified using Neal’s method and with correlations to the Landsat image mosaic of Antarctica. Estimated relative basal reflectivity values are validated using cross-over analysis and abruptness index measurements. From the Byrd relative reflectivity map, the corresponding echograms at the locations of potential subglacial water systems are checked for observable lake features. The results are checked for correlations with previously predicted lake locations and subglacial flow paths. While the results do not exactly match with the previously identified locations with elevation changes, high relative reflectivity values are observed close to those locations, aligning exactly or close to previously predicted flow paths providing a new window into the subglacial hydrological network. Relative reflectivity values are clustered to indicate the different potential basal conditions beneath the Byrd glacier.