Inter-annual surface ice velocities of the Panchi Nala glacier, western Himalaya: trends and controlling factors

Abstract

Abstract Information on glacier velocity is imperative to understand glacier mass, ice volume, topography, surge events of the glacier and response to climate change. Present study investigates inter-annual surface ice velocity (SIV) of the Panchi Nala Glacier, western Himalaya to understand its dynamics. The SIV has been computed by the feature tracking technique using the Co-registration of Optically Sensed Images and Correlation (COSI-Corr) method applied on the multi-temporal Landsat (TM and OLI) and Sentinel − 2 MSI images acquired between 2000 and 2021. Results show that the mean velocity of the debris-covered tongue (4500–4800 m asl) of the Panchi Nala Glacier is 10.6 ± 5.6 m/y during the study period. Additionally, the highest average glacier velocity is 13.8 ± 4.6 m/y, whereas the lowest is 8.9 ± 2.8 m/y, respectively, observed in 2005 and 2015. Also, the 95% confidence interval of the mean annual velocity lies between 9.8 and 11.4 m/y during the entire study period. There is no significant trend in the velocity rather it is highly heterogeneous on the inter-annual scale. Further the influence of several factors namely slope, debris cover, altitude, annual average temperature and precipitation on SIV was also investigated. Results indicate that the annual heterogeneity in SIV is linked with the variation of summer precipitation. Statistically, a 100 mm increment of summer precipitation can reduce the velocity around 1.3 m/y. The main reason behind this is the Panchi Nala glacier is located in high-elevation (4500m to 5600 m asl) where the climate is much colder and during the summer precipitation, the lower temperatures cause the precipitation to take the form of snow, which freezes and accumulates on the glacier. This reduces the process of basal sliding leading to slow movement. Further, detailed investigations using high-resolution remote sensing images and field data along with additional parameters need to be carried out to elucidate the spatial SIV and comprehensive causes for inter-annual fluctuations.