Hydrologic implications of GNSS vertical displacements in cold regions: insights from Northeast China

Ground-based Global Navigation Satellite System (GNSS) vertical displacements are increasingly used to infer terrestrial water storage (TWS) variations, but their applicability remains uncertain where weak hydrological signals coexist with non-hydrological deformation processes. This study evaluates the potential of GNSS-derived vertical displacements to capture TWS variability in Northeast China (NEC), a representative cold region characterized by weak hydrologic variability, a sparse GNSS network, and widespread freeze-thaw processes. Vertical displacements from GNSS, GRACE, and the Noah land surface model during 2012–2023 were compared. At the regional scale, network-mean GNSS displacements calculated using all examined stations were moderately correlated with GRACE- and Noah-based estimates (R = 0.61 and 0.68, respectively). At the station scale, GNSS captured long-term and interannual TWS variations at most stations, but its seasonal cycle differed markedly from GRACE and Noah. Agreement between GNSS and GRACE degraded substantially in winter (R = 0.30), possibly due in part to non-elastic deformation associated with freeze-thaw processes. Regional-average snow water equivalent was weakly correlated with station-mean vertical displacements from GNSS (R = 0.10), GRACE (R = 0.28), and Noah (R = −0.21), while correlations between TWS anomalies and vertical displacements were −0.60, −0.88, and −0.91, respectively. These results suggest that snow mass alone does not dominate seasonal TWS variability in NEC. Overall, GNSS vertical displacements capture regional and interannual TWS variations in cold regions, highlighting their potential for large-scale hydrological monitoring. However, possible non-elastic deformation associated with freeze-thaw processes requires further investigation to improve GNSS-based hydrological applications in complex cold-region environments.