Antarctic Ice Shelf Thickness Change from Multi-Mission Lidar Mapping

Over half of the drainage from the Antarctic ice sheet is through its peripheral ice shelves, floating extensions of the land ice covering 10% of the total ice covered area. The thinning of Antarctic ice shelves reduces their ability to buttress the glaciers that flow into them and makes the shelves more susceptible to fracture and overall collapse. Here, we calculate rates of ice thickness change and bottom melt for Antarctic ice shelves from a combination of Operation IceBridge Airborne Topographic Mapper (ATM) and Land, Vegetation and Ice Sensor (LVIS) measurements. Our technique is a novel processing scheme for co-registering airborne data in a Lagrangian reference frame that allows for the advection of the ice. This method reduces the effects from motion of ice thickness gradients, such as cracks and crevasses, which can saturate Eulerian-derived estimates. We focus on four different ice shelves in Antarctica that vary in terms of the processes that drive their change, their size and their repeat coverage. We find that ice thickness variations of the Larsen-C ice shelf are dominated by firn and surface processes over our observation period. The Wilkins ice shelf is sensitive to short time-scale coastal and upper-ocean processes, and basal melt is the dominate contributor to the ice thickness change over the period. At Pine Island in the previously grounded region between the 1996 and 2011 grounding lines, we find that ice shelf thinning rates exceed 40 m/yr. The thickness change is dominated by strong submarine thinning. Regions near the grounding zones of the Dotson and Crosson ice shelves are thinning rapidly due to intense basal melt. The changes to the ice shelves in the Amundsen Sea Embayment are likely contributing to the changes in the influxing glaciers and should be closely monitored. The NASA ICESat-2 mission will provide a revolutionary observational dataset for estimating ice thickness change in the future.