Improving the precision of Antarctic GNSS time series through non-tidal loading corrections

Abstract. Precise Global Navigation Satellite System (GNSS) measurements are essential for monitoring vertical land motion in Antarctica, where geophysical processes such as glacial isostatic adjustment (GIA) and ice mass change produce complex and often subtle deformation signals. However, a substantial portion of the variability in GNSS time series is caused by non-tidal loading (NTL), which can bias trend estimates and obscure geophysical signals if left uncorrected. This study evaluates the impact of 11 NTL correction model combinations from EOST (École & Observatoire des Sciences de la Terre, Strasbourg) and ESMGFZ (Earth System Modelling Group of GeoForschungsZentrum Potsdam) on vertical GNSS time series at three East Antarctic stations located in Dronning Maud Land (DML) using five datasets processed with distinct strategies. Results show that NTL corrections substantially reduce root mean square (RMS), noise, and seasonal amplitudes in datasets with high initial variability, particularly in precise point positioning (PPP)-based solutions, while network-based and combined solutions show limited improvement or even increased variability. Among loading components, non-tidal atmospheric loading (NTAL) consistently yielded the greatest reductions, while the added contribution of non-tidal oceanic (NTOL) and hydrological (HYDL) loading were beneficial only in specific GFZ model combinations in PPP-processed datasets. GFZ corrections generally outperformed EOST at two stations, where RMS values were reduced by more than 20 %. On the other hand, EOST corrections were more effective at one station, where RMS values were reduced by approximately 15 %. These results demonstrate the critical role of processing strategy, NTL model choice, and station environment in improving Antarctic GNSS time series for geophysical interpretation.