Snow density and water equivalent from snow pits Snow cover:Snow cover GlacioBasis Zackenberg:Since 2008, the GlacioBasis programme has been monitoring the glacier surface mass balance at the A.P. Olsen Ice Cap and its response to climate forcing. Greenland’s glaciers and Ice Caps are losing mass at a rate more than double of the Ice Sheet when adjusted for size, accounting for 14-20 % of the total sea level rise contribution from Greenland. As the glaciological component of a core WMO GCW CryoNet site and a contributor to the GTN-G through WGMS, the GlacioBasis datasets complement the ongoing monitoring based at Zackenberg, enable process-based understanding of physical processes driven by glacier melt water run-off in the downstream terrestrial and marine ecosystems, and can inform regional and global assessments under AMAP and IPCC. GlacioBasis operates the year-round automatic monitoring of A.P. Olsen Ice Cap near-surface weather at three stations, a network of ablation stakes covering the entire altitude range, and geophysical survey campaigns on the ground (radar snow depth) and airborne (surface elevation from lidar, ice thickness from radar). GlacioBasis data collection is adaptively updated to support research in processes emerging as key sources of nonlinearity in the cryosphere, including melt water retention and albedo feedbacks. As a representative Northeast Greenland Ice Cap, A.P. Olsen observations delivered by GlacioBasis are available to the national and international remote sensing and climate modelling communities for calibration, validation and upscaling purposes.