Dynamic thinning of Antarctic glaciers from along-track repeat radar altimetry

Since 2002, the Envisat radar altimeter has measured the elevation of the Antarctic icesheet with a repeat cycle of 35 days. This long and regular time series is processed using an along-trackalgorithm to depict in detail the spatial and temporal pattern of elevation change for the whole icesheet. We use this dataset to examine the spatial and temporal pattern of Pine Island Glacier (PIG)thinning and compare it to the neighbouring glaciers. We also examine additional areas, especially inEast Antarctica whose mass balance is poorly known. One advantage of the finer along-track spacing ofmeasurements is that it reveals places of dynamic thinning in regions of rapid ice flow. We observe theacceleration of thinning on PIG. Over the entire basin, the volume loss increased from 7 km3 a\textendash1 during2002\textendash06 to48 km3 a\textendash1 during 2006\textendash10. We also observe accelerated thinning on the lower tens ofkilometres of Thwaites Glacier, with a mean thinning of 0.18ma\textendash1 over its entire basin during ourobservation period. We confirm the dynamic thinning of Totten Glacier but we do not detectsignificantly accelerated thinning on any glacier elsewhere than on the coast of the Amundsen Sea.