Rock glacier distribution across the Himalaya

• Published in: Global and planetary change Vol. 239; p. 104481
• Main Authors: Harrison, Stephan, Jones, Darren B., Racoviteanu, Adina E., Anderson, Karen, Shannon, Sarah, Betts, Richard A., Leng, Ruolin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2024; Elsevier
• Subjects: Climate change; Climatology; Earth Sciences; Glaciology; Himalaya; Hydrology; Rock glaciers; Sciences of the Universe; Water supplies; Climate change; Water supplies; Rock glaciers; Himalaya; HIMALAYA; NEPAL
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2024.104481

In High Mountain Asia, human-induced climate warming threatens the cryosphere. Expected long-term reductions in future runoff from glacial catchments raises concerns regarding the sustainability of these natural ‘water towers’ and the implications of reduced water availability for regional human and ecological systems. Ice-debris landforms (I-DL), containing ice whether moving or not include rock glaciers and ice-cored moraines, and are likely to be climatically more resilient than debris-covered and debris-free glaciers. Recent work has shown that rock glaciers contain globally valuable water supplies yet over High Mountain Asia information regarding their number, spatial distribution, morphometric characteristics and water content are scarce. Here, we present the first systematic estimate of the current extent and distribution of rock glaciers for a subset of High Mountain Asia (the Himalaya). A sample of 2070 intact and relict rock glaciers were digitized on Google Earth imagery from the Western, Central and Eastern Himalaya regions and then quantitative and qualitative characteristics were analysed regionally based on topographic data from the NASA Shuttle Radar Topography Mission (SRTM) Version 3.0 and then aggregated across the Himalaya using an “upscaling” method. The majority of the digitized landforms (∼65%) were categorised as intact rock glaciers (i.e., ice-debris Landforms, or I-DLs, containing ice) and the remainder as relict rock glaciers (i.e., discrete debris accumulations or DDAs, not containing ice). They range in elevation from 3225 to 5766 m a.s.l., with the lowest in the Central Himalaya. Sampled relict and intact rock glaciers are primarily situated on northern quadrants. Over the entire Himalaya, we identified ∼25,000 landforms, with a total estimated areal coverage of 3747 km2. The area upscaling method was validated in the Manaslu region of Nepal using high-resolution Planet data (5 m) and freely available, fine spatial resolution optical satellite data accessed through Google Earth Pro and ESRI basemaps. In absence of complete rock glacier inventories over the Himalaya, our approach proves useful to investigate the nature, distribution and infer potential future behaviour of these landforms across the Himalaya in a changing climate. •Climate change in the mountains of the Himalaya is driving glacier melting and associated changes in water supplies to downstream areas.•This impacts the water supplies for hundreds of millions of people and ecosystems and is seen as a great challenge for future sustainable development in this part of central Asia.•However, large volumes of ice are contained are contained in rock glaciers (ice-debris landforms common in high arid mountains) although research on the number and extent of these in the Himalaya is limited.•In this paper, we present the first systematic estimate of the current extent and distribution of rock glaciers for the Himalaya and show that around 25,000 landforms exist in the region, with a total estimated areal coverage of 3747 km2.•We argue that rock glaciers constitute hydrologically valuable long-term water stores and, with continued climatically-driven glacier recession and mass loss, their value is likely to become increasingly important.