STUDYING FROZEN GROUND DYNAMICS BY USING GNSS INTERFEROMETRIC REFLECTOMETRY: ACHIEVEMENTS AND POTENTIAL SYNERGY WITH INSAR

Permafrost has been warming and thawing in the last decades in response to global warming. Monitoring the changes of the active layer and near-surface permafrost is crucial for revealing their dynamics. GNSS interferometric reflectometry (GNSS-IR) is a relatively new technique for studying frozen ground dynamics. In this paper, we summarized the major achievements in applying GNSS-IR to the signal-to-noise ratio data recorded by the continuous GNSS sites in permafrost areas in the Arctic and Qinghai-Tibet Plateau. We identified 23 sites in the Arctic permafrost regions which are suitable for GNSS-IR studies. We used the GNSS-IR-retrieved surface elevation changes to investigate the multi-year, interannual, and seasonal changes of the frozen ground. We improved the commonly-used GNSS-IR algorithm for estimating soil moisture in permafrost areas by mitigating the bias introduced by seasonal surface deformation. We also analogized GNSS-IR to InSAR, and advocated for a synergy between their observations to obtain improved, quantitative, and insightful measurements of the ever-warming frozen ground.