Glaciers in the Himalayas are shrinking

 Shrinking glaciers in the Himalayas linked to monsoon changes and heat  

High Mountain Asia, often called the “Third Pole,” holds the largest store of ice outside the Arctic and Antarctic. Its glaciers have shaped landscapes, nourished rivers, and sustained communities for thousands of years. But today, these frozen giants are shrinking at a troubling pace. Shifting precipitation patterns, driven by climate change, could reshape water security and environmental hazards for one of world’s most populated regions, research shows. Glaciers across High Mountain Asia are losing more than 22 gigatons of ice per year, the equivalent to nearly 9 million Olympic swimming pools, according to research from the University of Utah and Virginia Tech. The impact of a warming climate on glacial loss is undisputed, this new study provides the first evidence that seasonal shifts in rainfall and snowfall patterns, particularly of the South Asian monsoons, are also exacerbating glacier melting across the region. Scientists have long agreed that warming temperatures drive the retreat, yet new evidence reveals another culprit: shifting rainfall and snowfall patterns, especially those tied to the South Asian monsoon.

“These findings highlight that glaciers dominated by the South Asian monsoons, such as the Central Himalaya, Western Himalaya and Eastern Himalaya, are especially vulnerable,” said Sonam Sherpa, assistant professor at the University of Utah and lead author of the study. “If the timing and intensity of the monsoon continues to alter, it could accelerate ice loss and threaten water availability for millions downstream.” While rising temperatures explain much of the retreat, researchers show that the timing and type of precipitation now play a major role. Rain falling instead of snow fuels melt, and shorter or weaker monsoon seasons reduce the ice that glaciers can accumulate. High Mountain Asia is known as the “Third Pole” because it holds the world’s largest reserve of glacier ice outside the Arctic and Antarctic. The region’s glaciers feed lakes and rivers which supply freshwater to more than 1.4 billion people across South and Central Asia, sustaining agriculture, hydropower and drinking water. As glaciers retreat more rapidly, rivers will depend less on glacial melt and increasingly on rainfall as their main source of water. “Looking ahead, a faster retreat of mountain glaciers will shift the main source of river flow from glacier melt to rainfall, thereby heightening the risk of droughts in downstream regions for future generations,” said Susanna Werth, assistant professor at Virginia Tech and co-author of the study.

High-lying glaciers in the southern parts of the Central Himalayas accumulate during the summer, rather than in the winter. At higher elevations, cold temperatures turn annual monsoon precipitation into intense snowfall which feeds the glaciers. Glaciers retreat because they either receive less snowfall or experience more melting than usual. While warming itself drives melting, it also alters rain and snowfall patterns. This can shorten the precipitation season, reduce precipitation amount or cause a shift from snow to rainfall on the glaciers, driving even more melting due to less accumulation on glaciers. To understand these shifts, the researchers used satellite gravimetry from NASA’s GRACE and GRACE-FO missions. These satellites can “weigh” changes in water storage, including ice, by measuring gravity variations. Scientists corrected the data to account for groundwater use, soil moisture, surface water and snow. They paired this with climate reanalysis models, dividing the year into four phases: winter, premonsoon, monsoon, and postmonsoon. By analyzing rainfall and snowfall separately, they revealed how timing and precipitation type affect glacier mass. The experts found that glaciers respond more strongly to seasonal precipitation than to annual totals. 

Accelerated glacier-melt patterns also carry significant risks. Faster melting can increase the likelihood of glacial lake outburst floods, a growing threat in mountain regions worldwide as receding glaciers retreat in response to climate change. Together with follow-up cascading hazards, including landslides and river flooding, unstable glaciers can devastate vulnerable communities. Cycles repeating every 3 to 4.5 years and 5 to 8 years match the natural rhythm of South Asian monsoons. In the Central Himalaya, glacier loss was tied to reduced premonsoon rainfall. In the Eastern Himalaya, declining postmonsoon snowfall accelerated retreat. In the Western Himalaya, increased summer rain caused rain-on-ice events that sped melting. These details show that the seasonality of rain and snow is as important as overall precipitation amounts. Different climate systems influence each subregion. Monsoon-fed glaciers in the Central and Eastern Himalaya show the highest rates of ice loss. Glaciers dominated by the Westerlies, such as those in the Pamir–Hindu Kush and Karakoram, show slower declines or in some cases slight gains. The Tien Shan, influenced by Siberian systems and western cyclones, also shows significant losses. These contrasts highlight how winds and precipitation phase shifts shape glacier health differently across the mountains.

Climate projections suggest stronger and more intense monsoons in the coming decades, with possible changes in their timing. By 2100, ice loss in monsoon-dominated basins could reach 38–58%, depending on future emissions. Such a shift would profoundly affect river flows, agriculture and disaster risks. The study emphasizes that improved monitoring networks are urgently needed to capture rain, snow and temperature changes across high-altitude regions. Rapid melting brings hazards which are both immediate and long-term. Glacial lake outburst floods are becoming more common as ice retreats, creating unstable lakes held back by fragile moraine walls. Landslides and river floods often follow, putting downstream communities at risk. “This risk is not only about long-term water shortages but also about immediate threats to lives and infrastructure,” said Sherpa. High Mountain Asia’s glaciers are retreating under the combined weight of heat and shifting monsoons. Seasonal timing and the balance of rain versus snow now shape their fate more than annual totals.

Protecting communities downstream will require better observation and planning that accounts for these seasonal fingerprints. The research makes clear that what happens in these mountains will ripple far beyond their valleys, potentially impacting the lives of more than a billion people. The key findings of the analysis are given below:-

In the central and western Himalayan regions where glaciers typically grow during the summer, ice losses are now linked with increased rainfall. 

Repeating patterns in glacier retreat occur at 3–4.5-year and 5–8-year cycles, aligning with natural variability in monsoon patterns. This raises urgent questions about how future climate-driven monsoon shifts will impact long-term glacier health.

In eastern regions of the Himalaya, ice dynamics could be associated with reduced snowfall.

The researchers emphasize the urgent need for denser and more accurate monitoring networks of rainfall, snowfall and related climate variables. Improved observation systems are critical for predicting the impacts of monsoon alterations and guiding adaptation strategies around the whole area.