SVALPEN Svalbard Radar Snow Penetration Experiment

Abstract

Studying the extent and thickness of sea and glacial ice in a warming climate is important since they have both local and global significance in the form of feedback loops, climate effects, and ship transport, among others. While the extent of ice is well studied using satellite-based radar remote sensing, thickness estimates are not achieving satisfactory accuracies required to produce high-quality remote sensing products. Main driver of this uncertainty is the lack of understanding of radar signal penetration into snow overlaying the ice. In this thesis, we aim to characterize how well a 24 GHz frequency-modulated continuous-wave radar system is able to observe structure in and under a snowpack, and the conditions where radar penetration is ambiguous. This is done by performing different radar measurements, complemented with auxiliary snow measurements, at different sites.We find that the radar signal penetrates even deep snowpacks, with ice lenses being identified up to a depth of 110 cm and glacial ice at 140 cm. The surface of lake ice is easily identified under a shallow snowpack, and even the bottom of 1-meter-thick ice is observed, although already a few tens of centimeters of snow cause the bottom reflection to vanish. Additionally, we find that the burial of the radar in fresh and wind-blown snow temporarily causes a loss of signal from deeper in the snow, which mostly recovers over time. More importantly, the onset of melt on snow surface quickly blinds the radar, as even a small amount of liquid water is enough to block the signal. In conclusion, it is clear that such a radar system is able to detect some structure in snow and often the ice underneath. However, more studies need to be performed in snow on sea ice, which had to be left out of this study for logistic reasons.