Antarctic ice-sheet balance velocities from merged point and vector data

Abstract

Abstract We estimate Antarctic ice-flow balance velocities, which are the average speeds that ice must flow downslope through a volume assuming that there are equal amounts of ice entering and leaving the ice volume. We use the OSU (Ohio State University) digital elevation model of Antarctica, recent ice accumulation rate data and the BEDMAP ice-thickness data compilations for Antarctica to characterize the physical properties of the ice sheet that are included in the balance-velocity calculation. We adapt a flux algorithm from the hydrology literature that enables us to calculate the flux distribution from any cell in any order. Flux from one cell to its neighbors is partitioned as a simple function of surface slope direction. Digitized flow-stripe directions from satellite images minimize errors in flow direction where surface slopes are low or complex. We estimate errors in balance velocity arising from errors in the data and show semi-quantitatively how properties of the algorithm bias the balance-velocity result. We find a favorable comparison between our model and observed velocity data as well as the balance-velocity patterns reported by other researchers.