Studies have been carried out using various methods to estimate the Greenland ice sheet mass balance. Remote sensing techniques used to determine the ice sheet volume includes airborne and satellite radar and laser methods and measurements of ice flow of outlet glaciers use InSAR satellite radar interferometry. Direct mass changes of the Greenland Ice Sheet (GrIS) are obtained using gravitational change measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. All of these methods have limitations. Satellite radar altimetry (e.g. from European Remote Sensing Satellites) does not work on sloping surfaces and is affected by radar penetration into the snow. InSAR estimates require knowledge of outlet glacier thickness. GRACE has limited spatial resolution and is affected by mass variations not just from ice changes, but also from hydrologic and ocean mass variability and mass redistribution within the solid Earth. The accuracy of ice mass and ice volume estimates can be assessed by comparing results from different techniques. Here, we focus on volume loss estimates from ICESat, ATM and LVIS data.

We estimate catchment-wide ice volume change in northwest Greenland during 2003-2009 using Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter data (Zwally, 2011). Elevation changes are often reported to be largest near the frontal portion of outlet glaciers. However, due to relative large spacing between tracks, ICESat does not capture elevation change on all glaciers, which leads to an underestimation of the catchment-wide volume change. To improve the volume change estimate, we supplement ICESat data with altimeter surveys from NASA's Airborne Topographic Mapper (ATM) during 2002-2010 (Krabill, 2011) and NASA’s Land, Vegetation, and Ice Sensor (LVIS) during 2010 (Blair and Hofton et al., 2010). The Airborne data is mainly concentrated along the ice margin and therefore significantly improve the estimate of the total volume change.

Our results show that including ATM and LVIS data with the ICESat data increase the estimate of the catchment-wide ice volume loss by 10-20 percent.