The relationship between sticky spots and radar reflectivity beneath an active West Antarctic ice stream
Isolated areas of high basal drag, or ‘sticky spots’, are important and poorly understoodfeatures in the force balance and dynamics of West Antarctic ice streams. Characterizing sticky spotsformed by thin or drying subglacial till using ice-penetrating radar is theoretically possible, as high radarbed-returned power (BRP) is commonly related to an abundance of free water at the ice/bed interface,provided losses from englacial attenuation can be estimated. In this study we use airborne radar datacollected over Evans Ice Stream to extract BRP profiles and test the sensitivity of BRP to the adoptedenglacial attenuation correction. We analyse 11 �20km profiles in four fast-flow areas where stickyspots have been inferred to exist on the basis of model and surface data inversions. In the majority ofprofiles we note that the increase in basal drag is accompanied by a decrease in BRP and suggest thatthis is evidence both for the presence of a sticky spot in those locations and that local variations insubglacial hydrology are responsible for their existence. A comparison is made between empirical andnumerical modelling approaches for deriving englacial attenuation, and our findings generally supportprevious studies that advocate a modelling approach.