A study of the potential for using trends of GPS displacements to determine TWS trends in Poland

Permanent stations of the Global Positioning System (GPS) enable the registration of elastic deformations of the Earth’s surface that occur in response to variations in hydrological mass loads over continental areas. Analysis of long-term changes in displacements observed by a set of GPS permanent stations allows for the identification of deformations induced by long-term changes of the Terrestrial Water Storage (TWS). Densely distributed GPS stations provide adequate spatial coverage for regional scale analysis and their exact spatio-temporal analysis. We use a set of vertical displacements for the period 2010-2020 observed by 493 GPS permanent stations situated in Poland and neighboring regions, whose observations were processed by the Nevada Geodetic Laboratory (NGL). 213 of these stations exhibit more than 80% of temporal coverage with Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On satellite missions. We use these vertical displacements and invert them using elastic Earth theory and load Love numbers to infer trends of TWS in Poland. The obtained results were compared with independent estimates of TWS trends derived from the GRACE and GRACE Follow-On missions, and other external datasets. The analysis demonstrates that GPS-observed vertical displacements provide a reliable source of information for the assessment of TWS trends in Poland.