Glaciation of the eastern Himalayas: Palaeoglacial and palaeoclimatic insights from the Dibang Valley, India

The far eastern Himalayas, dominated by the Indian Summer Monsoon, receive some of the highest precipitation in High Mountain Asia, yet their glacial history remains poorly constrained. We present 63 new in situ cosmogenic 10 Be exposure ages from the Dri River catchment in Dibang Valley, Arunachal Pradesh, eastern Himalayas of India, providing the first directly dated Late Pleistocene glacial chronology along the southern slopes of the eastern Himalayas east of Mt. Everest. At its maximum, the Dri palaeoglacier extended ∼100 km, reaching one of the lowest toe altitudes in the Himalayas (1500–1300 m a.s.l.). This major advance occurred before mid-MIS 3 (∼44.8 ka), possibly as early as late-MIS 4 (≥58.5 ka). Glacial landforms further up valley dated to ∼19.6 ka indicate that the glacier had retreated by the end of the global Last Glacial Maximum, terminating at ∼1680 m a.s.l. By 12.6 ka the glacier had retreated to a length of ∼25 km to upland valleys, whilst cirques at ∼3700 m a.s.l. became ice-free by 13.3 ka. Glacial retreat coincided with regional warming, revealing a threshold-like response in which temperature increase enhanced melting and shifted monsoonal precipitation from snow to rain, reducing accumulation. Conversely, during colder phases, abundant monsoonal moisture coupled with lower temperatures enabled glacier expansion to considerable scales. This pattern demonstrates that glacier extent in the monsoon-dominated Himalayas was primarily temperature-driven, with precipitation acting as a secondary modulator, and highlights the climatic sensitivity of monsoonal glaciers to warming during deglacial transitions. The new chronology bridges a major spatial gap in Himalayan palaeoglaciology and provides critical constraints on how monsoon-dominated glaciers evolved across High Mountain Asia. • First 10 Be-dated Late Pleistocene glacial chronology from easternmost Himalayas. • At its maximum (≥58 ka), Dri palaeoglacier was ∼100 km in length reaching one of the lowest elevations in the Himalayas. • Cirques at 3700 m were ice-free by 14–13 ka; Dri palaeoglacier extent was only ∼25 km around 12.6 ka. • Glacier mass balance controlled mainly by temperature, not precipitation amount. • New record bridges major gap and refines monsoon-dominated glacier evolution.