3-D flow velocity time-series analysis from SAR-derived datasets towards maritime glaciers in the Namcha Barwa, Southeastern Tibetan Plateau

In reaction to a warming climate in the Southeastern Tibetan Plateau (SETP), the direction and intensity of surface flow in maritime glaciers undergo adjustments, causing glacial debris flow and ice avalanches. The safe operation of mega transportation projects across the region has been seriously threatened, e.g., the Sichuan-Tibet transportation corridor. Consequently, the measurement in three dimensions (3-D) consistently merits attention in the surface flow evolution for this glaciated region. In this study, we first mapped the 3-D and long-term surface flow of the glacier ensemble in the Namcha Barwa during 2019–2022 using the space-borne Synthetic Aperture Radar (SAR) technique, specifically applying the pixel offset tracking (POT) method to obtain deformation estimation of SAR-derived data. Subsequently, 3-D glacier velocities were acquired from the Multidimensional Small Baseline Subset (MSBAS) method conducted with the above datasets. Results show that two fast-moving glaciers were detected in the glacier ensemble, namely Dem Glacier and Namjagbrawa Glacier. Dem Glacier mainly flows eastward horizontally with a velocity of approximately 120 m/yr. And the inconspicuous vertical changes reveals that the glacier has sufficient winter supply. Although the detectable proportion of Namjagbrawa Glacier is relatively small, SAR results can perform well in limited pixels verified through optical results. It flows swifter over roughly −150 m/yr in the east, north, and vertical directions due to the vast elevation differences. However, other glaciers in the ensemble generally maintained slow flow, with multidimensional velocities below 20 m/yr. All glaciers' flow velocities and the local climate in temporal are parallelism in the variations, which exhibit summer-accelerated and winter-slowed seasonal patterns. There were no surge signs during the study phase, which does not preclude the possibility of future emergence. The maritime glaciers in the SETP should be therefore multidimensional and continuous monitored to implement early warning and forecasting for mega transportation projects.