Ice motion measurements, south-west Greenland Ice Sheet

From May 2009 to May 2013, seven dual-frequency GPS receivers were
deployed along a 120 km-long transect in the south-west of the
Greenland Ice Sheet. Two additional dual-frequency GPS receivers
were deployed perpendicular to longitudinal ice flow at ~14 km
inland: one 5 km distant from June 2011 to May 2013, and another
2.5 km distance from May 2012 to May 2013. Each receiver recorded
position observations every 10 seconds or 30 seconds (depending on
configuration), enabling resolution of horizontal and vertical ice
motion. Sites were powered by solar panels and operated 24 hours a
day during summer but shut down in the autumn. Absolute ice
displacements at each site were obtained for each summer and winter
period in the absence of continuous measurements. Position
measurements were kinematically corrected relative to an off-ice base
station using TRACK (Chen, 1999). Daily velocities were then obtained
by differencing across 24-hour periods, whilst continuous velocities
were obtained through application of a sliding 6-hour differencing window.

At each GPS site we also measured
(1) the near-surface air temperature every 15 minutes year-round,
(2) net seasonal ablation using ablation stakes, and
(3) at several selected sites melt rates using sonic ranging sensors.

This version 1 of the dataset has been succeeded by a new version with
ice motion records at 1-day resolution rather than 2-day resolution. In other
respects the dataset has not changed.