Glacier Velocity Changes in the Himalayas in Relation to Ice Mass Balance

Yu Zhou,Jianlong Chen,Xiao Cheng

doi:10.3390/rs13193825

Abstract

Glacier evolution with time provides important information about climate variability. Here, we investigated glacier velocity changes in the Himalayas and analysed the patterns of glacier flow. We collected 220 scenes of Landsat-7 panchromatic images between 1999 and 2000, and Sentinel-2 panchromatic images between 2017 and 2018, to calculate surface velocities of 36,722 glaciers during these two periods. We then derived velocity changes between 1999 and 2018 for the early winter period, based on which we performed a detailed analysis of motion of each individual glacier, and noted that the changes are spatially heterogeneous. Of all the glaciers, 32% have sped up, 24.5% have slowed down, and the rest 43.5% have remained stable. The amplitude of glacier slowdown, as a result of glacier mass loss, is significantly larger than that of speedup. At regional scales, we found that glacier surface velocity in winter has uniformly decreased in the western part of the Himalayas between 1999 and 2018, while increased in the eastern part; this contrasting difference may be associated with decadal changes in accumulation and/or melting under different climatic regimes. We also found that the overall trend of surface velocity exhibits seasonal variability: summer velocity changes are positively correlated with mass loss, i.e., velocity increases with increasing mass loss, whereas winter velocity changes show a negative correlation. Our study suggests that glacier velocity changes in the Himalayas are spatially and temporally heterogeneous, in agreement with studies that previously highlighted this trend, emphasising complex interactions between glacier dynamics and environmental forcing.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The estimates derived from different techniques vary, they consistently show that the Himalayan glaciers are experiencing significant thinning and mass loss, thereby affecting ice fluxes and river discharge
By differencing the Landsat-7 and Sentinel-2 derived velocities, we map velocity changes over nearly two decades, and, combining the data with glacier mass balance, we show the complex patterns of glacier flow in the Himalayas

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is of great importance to understand glacier evolution with time because it provides direct evidence for climate change [2,8,9]. The estimates derived from different techniques vary, they consistently show that the Himalayan glaciers are experiencing significant thinning and mass loss, thereby affecting ice fluxes and river discharge. Dehecq et al [9] investigated the response of glacier flow to mass changes at regional scales. They estimated time-series glacier velocities from 2000 to 2016, Remote Sens.

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