Piecewise polynomial fitting of the mass change trend of the Greenland ice sheet

To investigate the trend of mass changes in the Greenland Ice Sheet (GrIS), a piecewise polynomial function was constructed to fit the mass change time series. Gravity satellite data from the GRACE (Gravity Recovery And Climate Experiment) and its continuation, GRACE Follow-On (GRACE-FO), from January 2003 to December 2023, were used. The optimal filtering method for inverting the time series was determined using the generalized triangular cap method, with a Fan filter radius of 300 km. Swarm satellite data were used as constraints in an improved singular spectrum analysis to fill missing values in the time series and reconstruct the GrIS mass change time series. Based on this reconstruction, the study area was divided into six sub-regions: Southwest (XN), Southeast (DN), Northwest (XB), Northeast (DB), Central (ZX), and Mid (ZB), and mass change time series were established for each sub-region. The experimental results show that, during the study period, the Greenland Ice Sheet exhibited an overall downward trend, with a mass loss rate of -16.2824 Gt/month. The average monthly mass loss rates for the sub-regions XN, DN, DB, XB, ZX, and ZB were -2.4363 cm/month, -1.7730 cm/month, -0.6749 cm/month, -0.9854 cm/month, 0.3682 cm/month, and 0.0118 cm/month, respectively. Due to their proximity to the Arctic, the mass loss rates in the XB and DB regions were relatively slower. The ZB region displayed a relatively stable trend in ice mass, while the ZX region, located in the central part of the island, showed a phenomenon of mass growth.