Ice-dynamic conditions across the grounding zone, Ekströmisen, East Antarctica

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A detailed investigation was performed of ice-dynamic conditions across the southern grounding zone of Ekstroem ice shelf, at the mouth of a regular EastAntarctic outlet glacier not characterized by ice-streaming. Accurate field measurements along a profile of 20 km length served as input in a two-dimensionalnumerical ice-flow model in order to calculate the variation of stress, strain-rate and velocity components with depth. The model results pointed to a sharptransition between the mechanics of grounded and floating ice and the occurrence of a narrow transition zone in between of only a few km width. Shearing inhorizontal planes, most of it at the base, was found to be the dominant flow mechanism in grounded ice. This part was also characterized by a distinctsuccession of surface undulations which are in turn controlled by variations in resistive stresses at the bottom. The associated phase shift between drivingstress and basal drag was found to be accomodated by differential longitudinal pushes and pulls at the base. The flow in the upper half of the profile, on theother hand, was extensive everywhere. The adjacent ice shelf was characterized by small stress and velocity gradients in both the vertical and horizontaldirections of the vertical section, and little deformation. A calculated longitudinal deviatoric normal stress of only a tenth of the value required for freelyfloating ice shelves is indicative of a large backstress originating from friction along the sidewalls of the narrow embayment.

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ISI/Scopus peer-reviewed
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Mayer, C. and Huybrechts, P. (1999): Ice-dynamic conditions across the grounding zone, Ekströmisen, East Antarctica , Journal of Glaciology, 145 (50), pp. 384-393 .

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