Calculation of Ice Velocities in the Jakobshavn Isbrae Area Using Airborne Laser Altimetry

The ability to measure velocities of fast-moving glaciers is essential to the understanding and interpretation of their dynamics and related processes. This is especially important in the Jakobshavn drainage basin of the Greenland ice sheet, where a significant portion of the ice sheet mass loss occurs and the iceberg calving rate is high. In this article, we present a method for using airborne laser altimetry data to determine surface velocities in portions of the Jakobshavn drainage basin that have distinct elevation features. By examining correlations between repeat elevation surveys, the motion of these features, the most distinct of which are crevasses, is tracked. Results show that for areas with a standard deviation in elevation in excess of 1 m, displacement of features can be tracked to a precision of 1–2 m, and the corresponding velocities can be retrieved. The maximum velocity of the Jakobshavn Isbrae, at its calving front, is found to be nearly 7 km yr−1. Ice stream boundaries and flow patterns can also be observed in the derived velocity data.