GPS reflectometry study detecting snow height changes in the Southern Patagonia Icefield

Southern Patagonia Icefield (SPI) glaciers have been retreating and shrinking at high rates in recent decades, significantly contributing to sea level rise. In spite of the importance of the SPI, very little is known about its mass balance apart from models lacking in situ validation, such as snow accumulation/ablation at high altitude. On the ground, snow changes are normally measured with stakes planted on snow frequently visited. Automation is possible by the use of ranging sensors, based on laser, radar or ultrasound, installed as part of automatic weather stations. In this study, we use for the first time in the SPI the technique of Global Positioning System Reflectometry (GPS-R) for measuring snow level changes. GPS-R uses observations from GPS satellites tracked by GNSS (Global Navigation Satellite Systems) ground stations. GNSS stations, typically installed according to geodetic network standards for geodynamics purposes (e.g., glacial isostatic rebound studies), inadvertently also record the signal reflected on the snow surface in the antenna surroundings. The GPS-R snow level variations were compared to an ultrasonic sensor installed nearby, operating simultaneously between October 2015 and February 2016. During this period the two datasets exhibited a correlation of 0.91 and an RMS of 17 cm, confirming that GNSS receivers can be used not only for geodetic purposes but also for snow accumulation/ablation monitoring in SPI.