Transient Greenland Ice-Sheet mass variations from multiple geodetic data over the last two decades

Exact quantifications of the interannual and transient ice mass balance of Greenland Ice-Sheet (GrIS) are important for unraveling its complex dynamic processes under an increasingly warmer earth. In this study, we aim to analyze the transient mass variations of the GrIS over past two-decades, from April 2002 to April 2020. To achieve this, we integrate densely sampled time series data from various sources, including Global Positioning System (GPS) coordinates, Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (GRACE-FO) gravimetry, and Surface Mass Balance (SMB) model. The Principal Component Analysis (PCA) method is applied to improve the characterization of the GPS common-mode components associated with the interannual oscillation. We found that there was an abnormal subsidence of the bedrock surrounding Jakobshavn Isbræ in West GrIS during 2016 to 2019, which could be primarily attributed to the elastic mass loading effects caused by the deceleration of glaciers linking to the pronounced decrease of ice discharge. To improve the accuracy of the elastic loading signals estimated by GRACE/GRACE-FO around the margins of Greenland, we proposed a GPS-based scale factor method and yielded a scale factor of 2.58±0.15. After the analysis of multi-source loading signals, we suggest that the current transient dynamic process of the GrIS is predominantly influenced by the runoff of meltwater, which is triggered by warm and dry atmospheric circulations characterizing by interannual climate episodes.