Ice-stream ice-shelf interaction on Carslon Inlet, West Antarctica

Abstract

The effects of tides on motion upstream of the grounding line of Carlson Inlet, West Antarctica, was investigated. This was done through simultaneous GPS measurements at several sites both upstream and downstream from the grounding line. Of particular interest was the role of basal friction in determining the spatial range of horizontal stress transmission. For this type of investigation the Carlson Inlet was judged to a particularly well suited because basal friction varies by several order of magnitude in transverse direction across the ice stream. In accordance with theoretical predictions, it was discovered that the spatial scale of stress transmissions is reduced with increasing basal friction. Temporally induced variations in horizontal speed with a periodicity of about two weeks were detected on the part of Carlson Inlet where basal friction is low. Where basal friction is high, no such temporal variations in flow were observed. Perliminary modeling works shows that for sufficiently low basal-friction, non-linear interaction between the two main semi-diurnal tidal components (S2 and M2) gives rise to a strong fortnightly (Msf) horizontal tidal component in the flow upstream from the grounding line.