Surface ice velocity, radar backscatter and frontal changes - links to datafiles

Seasonal glacier ice velocities are important for precisely estimating annual ice discharge and understanding controlling mechanisms, but these measurements for a large number of Greenlandic glaciers are limited by low temporal resolution. We present seasonal changes in ice velocities, radar backscatter to mark the onset and extent of melt season and ice front positions of 45 Greenlandic glaciers using Sentinel-1 SAR data for the period 2015-2017. Seasonal velocity fluctuations of roughly half of the glaciers appear to be primarily controlled by surface-melt induced changes in the subglacial hydrology. This includes glaciers that speedup with the onset of surface melt and glaciers with comparable late winter and early melt season velocities showing significant slowdown during most of the melt season and speedup winter. Nearly 25% glaciers show strong correspondence between ice speed and terminus changes. Our results pinpoint the seasonal variations highlighting the variable influence of meltwater on year-around ice velocities.