Progressive thinning of Greenland's west-central flank and northwest coastal margin from operation icebridge laser altimetry.

We analyze Airborne Topographic Mapper laser altimetry data from the first three years of NASA's Operation IceBridge, with the purpose of measuring elevation changes in the flank of the ice sheet encompassing the Jakobshavn basin and adjacent areas, and the northwest coastal margin roughly between Thule and Upernavik. Our results show that thinning in both areas has continued and accelerated between 2009/2010 and 2010/2011. We show an ice/firn volume loss of 35+/-5 km(3)/yr between spring 2009 and 2010, increasing to 86+/-3 km(3)/yr between spring 2010 and 2011 for the west-central flank region. The increase in thinning was concentrated along the low-elevation portion of the ice sheet and near the Jakobshavn channel, and probably indicates a mixture of dynamic thinning and a surface mass imbalance. We also measure a region of higher-elevation thickening. For the northwest coastal margin, the limitations of our sampling of the complex area preclude a robust calculation of volume change. However our results here show major acceleration in thinning of the Upernavik ice stream main channel, thinning on every glacier we examined, and a coastward migration of the high-elevation area of thickening.