Review article: The hydrology of debris-covered glaciers – state of the science and future research directions

Abstract

12Debris-covered glaciers (DCGs) are characterised by distinct hydrological systems that differ 13 fundamentally from those observed on clean-ice valley glaciers. To date, most studies of DCG 14 hydrology have focused on supraglacial hydrology, given that surface streams are broadly 15 accessible and repeat observations can lead to conceptual models of channel evolution. Few have 16 characterised englacial conduits and their layout, and none have directly investigated potential 17 subglacial drainage networks in any setting. In this review, we summarise the current state of 18 knowledge relating to DCG hydrology with a global focus, and present our own field observations 19 to illustrate the distinct nature of DCG landforms on a receding high-elevation glacier in the 20Himalaya. We draw on recent work that has gone some way towards providing a process-based 21 understanding of the formation and evolution of englacial and subglacial hydrological pathways 22 and consider the role that DCG hydrology plays in regulating water supplies to downstream 23 communities, contrasting this information with clean-ice examples. We conclude by identifying 24 important knowledge gaps that might be considered priorities for future research into DCG 25 hydrology. 26

Glacial and geomorphic effects of a supraglacial lake drainage and outburst event, Everest region, Nepal Himalaya

“…The few observations of outburst floods from high-elevation debris-covered glaciers suggest a distinct seasonal cycle of hydrological development that contrasts with clean ice glaciers (e.g. Fyffe et al, 2015;Miles et al, 2017a;Narama et al, 2017). Rather than a gradual up-glacier progression of an efficient, connected drainage network (e.g.…”

“…Carrivick and Tweed, 2016;Cook et al, 2016;Harrison et al, 2018). Outburst floods from water within the glacier system are generally smaller in magnitude, but they can occur repeatedly due to seasonal and interannual variations in storage within a glacier's hydrological system, whether water is impounded supraglacially (Miles et al, 2017a;Narama et al, 2017;Watson et al, 2017), englacially (e.g. Benn et al, 2017;Rounce et al, 2017), subglacially (e.g.…”

Spatio-temporal changes in the six major glaciers of the Chitral River basin (Hindukush Region of Pakistan) between 2001 and 2018

“…The studied glaciers that have experienced regular upward shift in the ELA may be due to the increased avalanche events triggered by steep topography (Azam et al 2018) and the regular earthquake events in the area. As avalanching, rockfalls and landslides from adjacent rocks (triggered by freeze-thaw process or earthquakes) contribute to the glacier surface debris (Nagai et al 2013;Markus and Christian 2012;Miles et al 2017) which cause rapid melting in some cases.…”

Contextualizing lobate debris aprons and glacier-like forms on Mars with debris-covered glaciers on Earth

“…This is an active area of research, where new data are being collected (e.g. Miles et al, 2017; Steiner and Pellicciotti, 2016; Yang et al, 2017), models continue to be refined (e.g. Aubry-Wake et al, 2018; Evatt et al, 2015; Fyffe et al, 2014; Groos et al, 2017; Lejeune et al, 2013; Rounce et al, 2015; Shaw et al, 2016), and data-model evaluation progresses (e.g.…”