Long‐term spatiotemporal variability in the surface velocity of Eastern Himalayan glaciers, India

Abstract

Investigation of spatiotemporal variation in glacier velocity is imperative to comprehend glacier mass and volume loss as a function of their sensitivity to climate change. The long‐term glacier velocity record for the Eastern Himalayan region is of utmost importance owing to its data scarcity and climate sensitivity. Here, we present a long‐term dataset spanning more than two decades (1994–2020) of glacier surface velocity for the entire Sikkim Himalaya by applying image correlation methods on the multi‐temporal Landsat images. Our results demonstrate an average glacier surface velocity decline from 15.7 ± 5.69 (1994/96) to 12.88 ± 2.09 m yr−1 (2018/2020), that is a decline of ~15% during the period of investigation. Trend analysis shows a decreasing trend in median velocity (32.2%) at a rate of 0.25 m yr−1. Despite the general decline in average glacier velocity, the rate of slowdown of individual glaciers is extremely heterogeneous (3.6–20 m yr−1). Our study shows that up to 32% of the observed heterogeneity in velocity variation can be explained by the variation in glacier size. The present study highlights that large glaciers with thick ice cover move faster compared to small glaciers (even those situated on steep slopes). The findings are significant and have direct implications for assessing future water availability scenarios and modelling glacio‐hydrology in the region.

Post-Little Ice Age glacial lake evolution in Svalbard: inventory of lake changes and lake types

“…The rate of glacial mass loss in Svalbard between 2000 and 2019 has been estimated at −7 Gt yr −1 (Noël and others, 2020). It is therefore lower than the corresponding rate in Alaska (−75 Gt yr −1 ), which is the highest worldwide (Jakob and others, 2021; Zemp and others, 2012; Rick and others, 2022), but significantly higher than that in the Himalaya (−2.86 Gt yr −1 ) (Kaushik and others, 2022). Thus, if we normalise the rate of deglaciation of the regions listed with respect to the area occupied by glaciers there per 100 km 2 , the highest value is invariably found in Alaska (−0.25 Gt yr −1 /100 km 2 ), followed by Svalbard (−0.02 Gt yr −1 /100 km 2 ) and the Himalaya (−0.01 Gt yr −1 /100 km 2 ) (Noël and others, 2020; Jakob and others, 2021; Kaushik and others, 2022; Rick and others, 2022).…”

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

“…According to the investigation, 32% of glaciers have accelerated, 24.5% have slowed down, and 43.5% have remained unchanged (Zhou et al, 2021). Literature suggests that, in comparison to the Western Himalayas, glaciers in the Eastern and Central Himalayas move more slowly (Bolch et al, 2012;Kaushik et al, 2022). Interestingly, western Himalayan glaciers accelerated during the nal decade of the 20th century followed by a steady slow down (Scherler et al, 2011;Azam et al, 2014;Sam et al, 2018;Sahu and Gupta 2019;, however, with intra-regional heterogeneity.…”

“…The Himalayan glaciers constitute the largest mass of ice found outside of the polar regions, with an area and volume of ~ 40,000 km 2 (Azam et al, 2021) and 3500 km 3 (Azam et al, 2021), respectively. The Himalayan glaciers, which are also aptly known as the "water towers of the world," are the principal sources of perennial rivers like the Ganges, the Indus, and the Brahmaputra, and these rivers provide water for millions of people (Bajracharya et The velocity of a glacier is a crucial factor to comprehend its mass (Dehecq et al, 2019), ice volume (Sattar et al, 2019), surge activity (Quincey et al, 2011), topography (Sam et al, 2018), and its response to climate change (Garg et al, 2019;Zhao et al, 2020;Kaushik et al, 2022). To be more speci c, decreasing glacier velocity denotes a reduction in ice mass, whereas increasing glacier velocity denotes an increase in ice mass within the glacier system (Heid and Kääb, 2012a).…”

Glacier Surface Velocity Variations in the West Kunlun Mts. with Sentinel-1A Image Feature-Tracking (2014–2023)

“…By contrast, offset tracking of the intensity of SAR image pairs to estimate the displacements can partially overcome the shortage of image interference. Hence, this technique is widely used for glacier velocity estimation [15].…”