Influence of basal ice shelf conditions on ice sheet stability in Dronning Maud Land through radio-echo sounding and ice-sheet modelling.

Radio-echo sounding is a widespread remote sensing method used in glaciology to obtain a wide range of information concerning boundary conditions of ice sheets. Radar emits electromagnetic waves. They propagate through the ice until they encounter dielect ric heterogeneities. The central concept of radio-echo sounding is the study of properties of such echo wave through the analysis of both power and two-way travel time. Power provides direct information about the nature of ice/bedrock or ice/ocean interfa ces (till, rock, water, marine ice). Two-way travel time is a function of reflectors depth. Bedrock reflects the greatest part of the wave. However, some reflectors occur in the body of an ice mass. Usually, these reflectors are characterized by a wide an d continuous extension and they are assumed to be isochronous. Their geometries depend on history of the ice dynamics. By introducing these constraints in inverse models, we can infer boundary conditions as surface accumulation rate, basal melting, basal sliding and till deformation. During austral summer 2010-2011, several radio-echo sounding profiles were surveyed nearby the grounding line in Dronning Maud Land, Antarctica. Furthermore, airborne radar data were collected in the region thanks to EUFAR su pport This project will focus on the treatment and analysis of data acquired during this field expedition and on the definition of the nature of the bed. This project is part of a large project aiming to achieve a profound analysis of ice/bedrock or ice/o cean interface through study of bed-returned power and isochrones architecture. It will allow us to determine the influence of grounding line and ice rises on ice flow through ice shelf and ice stream in East Dronning Maud Land.