Hot water drilling in the firn layer of Greenland's percolation zone

The intermixed thermal and structural framework of cold firn, water-saturated firn and ice layers in Greenland's percolation zone can be challenging to penetrate with core drills. Here, we present our experiences using a hot water drill for research on the firn layer of the percolation zone. We built and deployed a lightweight and easily transportable system for drilling a transect of ~15 cm diameter boreholes through the full firn column thickness, to depths exceeding 100 m. An instrumented drill stem provides a scientific measurement of the firn properties while drilling. The system was successful at gaining rapid access to the firn column with mixed wet and cold conditions, was easily transported to the site and across the glacier surface, and required a small field crew to operate. The boreholes are well suited for in situ investigations of firn processes in Greenland percolation zone.