GPS Interferometric Reflectometry measurements of ground surface elevation changes in permafrost areas in northern Canada

Abstract

Abstract. Global Positioning System Interferometric Reflectometry (GPS-IR) is a relatively new technique which uses reflected GPS signals to measure surface elevation changes to study frozen ground dynamics. At present, more than 200 GPS stations are in continuous operation in the Northern Hemisphere permafrost areas. They were originally designed and maintained for tectonic and ionospheric studies. However, only one site in Barrow, Alaska has so far been used to study permafrost by GPS-IR. Moreover, GPS-IR has high requirements on ground surface condition, which needs to be open, flat, and homogeneous. In this study, we screen 3 major GPS networks in Canada and identify 12 out of 38 stations located in permafrost areas as useful ones where reliable reflectometry measurements can be obtained. We narrow our focus to 5 Canadian Active Control System stations and obtain their daily GPS-IR estimated surface elevation changes. We find that the ground surface subsided in Alert and Resolute Bay respectively by 0.79 ± 0.04 cm yr−1 (2012–2017) and 0.70 ± 0.02 cm yr−1 (2003–2014), but uplifted in Iqaluit by 0.35 ± 0.04 cm yr−1 (2010–2017). At the other two sites respectively in Repulse Bay and Baker Lake, the trends are not statistically significant. The linear trends of deformation were negatively correlated with those of the thaw indices in Alert, Resolute Bay, and Iqaluit. Furthermore, in Resolute Bay, we also find that the end-of-thaw elevations during 2003–2012 were highly negatively correlated with the square root of thaw indices. This study highlights multiple useful GPS stations in northern Canada, where multi-year, continuous, and daily GPS-IR estimated surface deformation can be obtained and used to study frozen ground dynamics at various temporal scales and across a broad region.