Glacier-surface velocities in Gangotri from Landsat8 satellite imagery

A glacier's mass balance and dynamics are regulated by changes in ice velocity. As a result, estimating glacier flow velocity is a crucial part of temporal glacier monitoring of its health, response to climate change parameters, and its effect on increasing the sea level rise. In this study, we estimated the Gangotri glacier surface velocities from 2014 to 2021. We used remote sensing-based techniques to estimate the Gangotri surface velocity since it provides such measurements regularly for a vast geographical area. Sub-pixel correlation of Landsat 8 imagery was used by using the COSI- Corr (co-registration of optically sensed images and correlation) tool to determine surface velocities over the Gangotri glacier. Our derived velocities values match the ground truth velocities values comparatively well. Gangotri surface velocities vary over the various regions of the glacier, and from year to year. Our study indicated that the middle region of the ablation zone and the accumulation zone had higher velocities across all the years, while the boundary regions of the glacier show lower speeds. The average velocities range varies from ∼13 m/year in the accumulation zone to ∼22m/year. For the ablation zone, the average velocities range from ∼ 11m/year in the ablation zone to ∼18m/year. The average surface velocity showed a high decrement of 26 % from 2014 to 2021. The general surface velocities in Gangotri vary from ∼8 m/y to∼ 61 m/y± 1.9 from 2014 to 2021.