Himalayan glaciers losing ice, slowing down as climate change intensifies: Study

Dehradun: Glaciers in Ladakh’s Zanskar region are thinning rapidly and moving more slowly than they did three decades ago, with scientists linking the trend to sustained ice loss driven by a warming climate, according to a new study by researchers from IIT Bombay and Australia’s Monash University.Authored by Tirthankar Ghosh and Raaj Ramsankaran of IIT Bombay, and Felicity S McCormack and Andrew N Mackintosh of Monash University, Australia, the study, published in the journal The Cryosphere, analysed 12 selected glaciers in the Zanskar Basin in Ladakh region using satellite observations spanning 1992 to 2023. The researchers found a statistically significant slowdown in glacier flow across the region, accompanied by persistent glacier thinning.Average glacier movement declined by 2.43 m per year every decade, while overall flow speeds dropped by around 16% during the study period. Mean glacier velocity along the central flowline fell from 31.1 m per year in 1992 to 26.2 m per year in 2023.According to the authors, though they appear frozen in place, glaciers are constantly moving downhill at a very slow pace under the force of gravity. However, as a glacier thins and loses mass, the force driving its movement downhill decreases, causing the glacier to flow more slowly.

At the same time, glacier thinning accelerated markedly. Average ice loss increased from about .22 m annually between 2000 and 2005 to nearly .57 m per year during 2015-2020. The most severe thinning occurred at lower elevations, particularly below 5,000 m, where glaciers are more vulnerable to rising temperatures and melting.Glaciers in lower-altitude zones slowed nearly three times faster than those at higher elevations.

“Some glacier sections lost more than 1.3 m of ice annually, particularly near their termini where melting is most intense,” said Ghosh.The study concludes that climate-driven glacier thinning is the primary driver of this slowdown. As glaciers lose mass and become thinner, the gravitational force pulling the ice downhill weakens, reducing their flow. However, scientists noted that glacier behavior is also influenced by localised factors, including slope geometry, debris cover, sub-glacial conditions and terminus type.Despite a general weakening across regional glacier systems, certain lake-terminating glaciers like the Drang Drung Glacier maintained higher velocities and even localised acceleration near their termini. According to researchers, these discrepancies highlight how complexly climate change interacts with unique, glacier-specific traits.The findings come amid rising anxiety over Himalayan water security. The heavily glacierised Zanskar region acts as a vital freshwater reservoir for downstream communities and rivers. Alarmingly, climate records show a pattern of rising summer temperatures and dropping winter snowfall. These trends are projected to worsen in the coming decades, driving down snow accumulation and triggering faster melt and mass loss.