SPATIO-TEMPORAL GEOID HEIGHT VARIATIONS IN THE TIEN SHAN REGION DERIVED FROM GRACE-FO DATA

Abstract

This study investigates the spatio-temporal variability of geoid height within the Tien Shan orogenic system using GRACE-FO satellite data for the period 2019–2025. The analysis is based on monthly GFZ RL06.3 global geopotential models processed with low-degree coefficient replacement, DDK3 decorrelation filtering, and subsequent seasonal-trend decomposition of the time series. The results show that geoid height variations in the region are controlled by the combined influence of hydrological, cryospheric, and geodynamic processes. The seasonal component exhibits stable intra-annual recurrence with an average amplitude of about 3.6 mm, with positive extrema occurring in spring and negative extrema in autumn. Against this background, a long-term negative trend was identified, most pronounced in the high-mountain areas of the Tien Shan, where the rate of decrease reaches 0.53 mm/yr. The spatio-temporal consistency between the 2024 anomalies and the increase in regional seismic activity suggests a possible tectonic contribution to the observed signal. The obtained results confirm the potential of satellite gravimetry as an effective tool for regional monitoring of contemporary mass redistribution and geodynamic activity.