Field-based investigations of the subsurface environment of a high-elevation debris-covered glacier

Abstract

Debris-covered glaciers comprise around a third of all glaciers in High Mountain Asia, and thus represent a critical source of meltwater for those living in the foothills of the region. Many of these debris-covered glaciers are situated at elevations exceeding 4,500 m above sea level and display a number of unique supraglacial features and mass balance characteristics arising from the spatially variable thickness of their supraglacial debris layers. Given their remoteness, these glaciers are difficult to access; field-based data are severely lacking, particularly for the subsurface environment, meaning both the parameterisation and validation of numerical modelling experiments are frequently based on assumptions and calculations. To address this gap, this research investigates the subsurface environment of a high-elevation debris-covered glacier, Khumbu Glacier, Nepal Himalaya, through a series of field-based experiments. In particular, the thermal regime, subsurface hydrology, and englacial debris content of Khumbu Glacier are targeted. The results reveal that Khumbu Glacier has a polythermal regime, with a notable proportion of temperate, and potentially warming, ice towards the terminus, which may support the presence of a persistent subsurface hydrology. The glacier’s drainage system transports meltwater inefficiently during the early melt season, but has the capacity for more efficient transport with greater inputs. Meltwater transit through a large chain of linked supraglacial ponds is slow, which may promote enhanced surface ablation and, together with a warming thermal regime, may increase the glacier’s sensitivity to future climatic warming through time. However, in
contrast, the continued melt-out of a relatively high englacial debris content may act to suppress melt rates within only a few decades. Combined, the data presented in this thesis provide a suite of empirical observations that can reduce the current uncertainties inherent in contemporary numerical predictions of debris-covered glacier evolution and water resource availability within the region

Date of Award	2020
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Bryn Hubbard (Supervisor), Tristram Irvine-Fynn (Supervisor) & Duncan Joseph Quincey (Supervisor)