Due to recent warm and record-warm summers in Greenland (Nghiem et al. 2012), the melt of the ice-sheet surface and the subsequent runoff are increasing (Shepherd et al. 2012). About 84% of the mass loss from the Greenland ice sheet between 2009 and 2012 resulted from increased surface runoff (Enderlin et al. 2014). The largest melt occurs in the ablation zone, the low marginal area of the ice sheet (Van As et al. 2014), where melt exceeds wintertime accumulation and bare ice is thus exposed during each melt season. In the higher regions of the ice sheet (i.e. the accumulation area), melt is limited and the snow cover persists throughout the year. It is in the vast latter area that models struggle to calculate certain mass fluxes with accuracy. A better understanding of processes such as meltwater percolation and refreezing in snow and firn is crucial for more accurate Greenland ice sheet mass-budget estimates (Van Angelen et al. 2013).
In May 2012, the field campaign ‘Snow Processes in the Lower Accumulation Zone’ was organized by the Geological Survey of Denmark and Greenland (GEUS) at the KAN_U automatic weather station (67 degrees N, 47 degrees W; 1840 m above sea level), which delivers data to the Programme for Monitoring of the Greenland Ice Sheet (PROMICE; Van As et al. 2013) and is one of the few weather stations located in the lower accumulation area of Greenland. During the expedition, we installed thermistor strings, firn compaction monitors and a snowpack analyzer; we drilled firn cores, performed firn radar measurements, gathered meteorological data, dug snow pits and performed dye-tracing experiments. One important objective of the campaign was to understand the thermal variability in the snowpack during the melt season by monitoring with high-precision temperature probes [...].
Below, we present observations from the period 02 May to 23 July and interpret the atmosphere–surface interaction and its impact on the subsurface snow layers, with the goal to quantify refreezing in the Greenland accumulation area.
2015. no 33, 65-68 p.