Dynamics of the spatiotemporal velocity of glaciers on the eastern slope of Mount Gongga, China, under climate change

The quantitative assessment of glacier flow velocity dynamics plays a pivotal role in understanding its response mechanisms concerning climate warming. This work provides a systematic quantitative assessment of the deceleration status of glaciers in this region by investigating the motion evolution of typical glaciers in Mount Gongga in recent years, thereby revealing the seasonal dynamics and inter-annual evolution over an extensive time span. We used the optical flow-small baseline subset (OF-SBAS) method to compute the time-series velocities of the Hailuogou Glacier and the Mozigou Glacier using 178 archived Sentinel-1 satellite synthetic aperture radar (SAR) images from 2014 to 2021. The findings revealed a prominent seasonal pattern in glacier motion, characterised by cyclic variations in velocity from cold to warm seasons. Moreover, we identified variations in velocities across distinct regions of the glacier surface, underscored by the lag in the peak time node of glacier flow with increasing elevation. This pattern may have been determined by a combination of internal and external factors, including mass accumulation and ablation-driven subglacial drainage, as well as the glacier geomorphological setting. Furthermore, during 2015‒2021, the glaciers on the eastern slope of Mount Gongga exhibited an overarching trend of deceleration. Notably, the ablation area of the Hailuogou Glacier recorded the most substantial deceleration, exceeding 8% per year. This study underscores the efficacy of the OF-SBAS method in extracting long-term glacier velocities. This work also establishes a robust foundation for the analysis of spatiotemporal fluctuations in glacier movement within the context of climate warming.