Motion and calving at LeConte Glacier, Alaska

Abstract

An analysis of motion and calving in the terminus region of LeConte Glacier delineates controls which are important to tidewater glacier stability. Ice velocities in this region are quite high; at the terminus they exceed 27 m d⁻¹. Our analysis reveals fluctuations in velocity that are forced by ocean tides, surface melt and precipitation. However, the overall velocity is steady over seasonal time intervals. LeConte's terminus position varied substantially, even given this steady ice influx, establishing a correlation between the calving flux and the terminus position (flux out). Although this correlation is largely numerical, the occurrence of calving events is not purely stochastic. Calving occurs as floatation is approached, and multiple short-lived triggers may force calving events by promoting a buoyancy instability. These triggers may include the tide, water input, and water depth. Flexure of the nearly floating portion of the glacier promotes crevasse growth, and helps to initiate calving.