As glaciers across the eastern Himalayas disappear at some of the fastest rates in High Mountain Asia, scientists have reconstructed the history of a colossal glacier that once flowed through Arunachal Pradesh’s Dibang Valley, offering fresh insights into how climate change has shaped—and continues to reshape—the region’s mountains.
A new international study has revealed that an ancient glacier stretched nearly 100 kilometres through the Dri Valley, drained by the Dri River, a major tributary of the Dibang River, in present-day Arunachal Pradesh.
The glacier descended to elevations of 1,300–1,500 metres—among the lowest glacier limits documented anywhere in High Mountain Asia. Today, the Dri Valley lies near Anini, an emerging offbeat tourism destination in the Mishmi Hills known for its spectacular mountain landscapes and waterfalls.
Published in the journal Quaternary Science Reviews, the research was led by Shashank Nitundil of the University of Manchester, along with Christopher M. Darvill, Abi Stone, David Fink, Philip D. Hughes, Matt D. Tomkins and Krista Simon.
The study was carried out in collaboration with the Australian Nuclear Science and Technology Organisation (ANSTO), while fieldwork was supported by Emudu Trekkers and members of the Idu Mishmi community, the traditional custodians of the Dibang Valley.
The study fills a major gap in Himalayan climate research by providing the first directly dated glacial chronology from the southern slopes of the eastern Himalayas east of Mount Everest—a region that had remained largely unexplored despite receiving some of the heaviest monsoon rainfall in High Mountain Asia.
To reconstruct the glacier’s history, the researchers analysed 63 rock samples using cosmogenic beryllium-10 exposure dating, a technique that determines how long rocks have remained exposed after glaciers retreated. The analysis enabled the team to establish the most detailed timeline yet of glacier advances and retreats in the Dibang Valley.
The findings show that the Dri palaeo-glacier reached its maximum extent more than 44,800 years ago, and possibly as early as 58,500 years ago. By around 19,600 years ago, the glacier had already retreated substantially, and by 12,600 years ago it had withdrawn to the upper valleys. Around 13,300 years ago, even the high-altitude cirques at nearly 3,700 metres had become ice-free.
The study provides new insights into glacier behaviour in one of India’s wettest mountain regions. Rather than monsoon rainfall alone determining glacier fluctuations, the researchers found that glacier evolution was primarily controlled by temperature through its interaction with precipitation and the region’s rugged topography.
During colder periods, abundant monsoon moisture fell largely as snow, allowing glaciers to expand dramatically. As temperatures rose, an increasing share of precipitation fell as rain instead of snow, reducing glacier accumulation and accelerating ice loss.
According to the authors, the findings demonstrate a “threshold-like response”, in which relatively small increases in temperature fundamentally altered glacier behaviour, making the monsoon-fed glaciers of the eastern Himalayas particularly sensitive to warming.
“The Dri Valley and the region around Anini are often described as a ‘valley of waterfalls’, with countless cascades set within one of India’s most spectacular mountain landscapes,” said lead author Shashank Nitundil. “Much of that dramatic landscape was sculpted by a glacier that once descended to one of the lowest elevations documented anywhere in High Mountain Asia.
By linking the evidence preserved in the landscape with a detailed timeline, we’ve been able to reconstruct how this giant glacier evolved over tens of thousands of years, providing an important benchmark for understanding glacier change in this critical monsoon-dominated region.”
The findings are especially relevant today. Recent observations cited in the study show that glaciers around Namche Barwa in the far eastern Himalayas are now among the fastest-thinning in High Mountain Asia, underscoring the urgency of understanding how these glaciers responded to past climate change.
The Dibang Valley, located in Arunachal Pradesh’s Mishmi Hills, receives nearly 2,800 mm of annual rainfall, with almost 90 per cent falling during the Indian Summer Monsoon. The basin currently contains around 219 glaciers covering roughly 200 sq km, making it an ideal natural laboratory for studying how monsoon-fed glaciers respond to climatic shifts.
Beyond reconstructing the region’s Ice Age history, the researchers say the new chronology provides an important benchmark for understanding the future of Himalayan glaciers, which sustain rivers supplying freshwater to billions of people across South and Southeast Asia.
The study also bridges a long-standing geographical gap in Himalayan palaeoglaciology and provides critical evidence for predicting how monsoon-dominated glaciers may respond to continued global warming.
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