Accelerating ice loss from peripheral glaciers in North Greenland

We use ICESat data from February 2003 to October 2009 to estimate elevation changes over the ice surface. We estimate height changes over the ice surface, on a regular grid with a resolution of 500x500 m that covers all of Greenland’s peripheral glaciers. We use all available ICESat data to create height time series at each grid point. At each grid point, we fit a trend, a second-order surface topography, and a seasonal term to account for the annual surface changes. The observed height change rates from ICESat are interpolated into a regular grid of 500x500 m. The interpolation is performed using the ordinary kriging method. We used the observed elevation change rates to estimate an empirical semi-variogram. Next, we fit an exponential model variogram (with a range of 60 km) to the empirical semi-variogram to take the spatial correlation of elevation change rates into account in the error budget. For each grid point, we estimate elevation change rate dh and associated error. We correct the observed height change rates for firn compaction, elastic uplift rates from present-day mass changes, and long-term past ice changes (Glacial Isostatic Adjustment- GIA). We correct for GIA, using the GNET-GIA empirical model of Khan et al. (2016). For each grid point, we estimate the GIA uplift rate and the associated uncertainty. To correct for elastic uplift of the bedrock, we convolve ice loss estimates of peripheral glaciers and the Greenland ice sheet with the Green’s functions derived by Wang et al. (2012) for elastic Earth model iasp91 with refined crustal structure from Crust 2.0.