Studies of glacier-hydrology have focused on clean Alpine glaciers, and recently ice sheet outlet glaciers, but there are few studies on debris-covered glaciers. It is known debris affects ablation rates, and that debris-covered glaciers evolve differently to their debris-free counterparts, but how the debris influences the hydrology is poorly understood. This thesis aims to understand the influence of the debris on the hydrological system and water balance of Miage Glacier, Western Italian Alps. The supraglacial hydrology was studied by modelling ablation using a distributed energy balance melt model, and measuring supraglacial stream discharges; the structure and evolution of the englacial and subglacial network was investigated using dye tracing and water chemistry monitoring; and the proglacial runoff was examined through detailed hydrograph analysis. Glacier velocity measurements were used to investigate the debris’ influence on the glacier dynamics. High ablation rates occurred on clean ice and beneath thin debris on the upper glacier, resulting in large supraglacial streams which led into an efficient drainage system. Glacier velocities had a greater magnitude and variability close to the upper glacier moulins. Thick debris on the lower glacier reduced ablation, and consequently the discharge of supraglacial streams and efficiency of the hydrological network. Despite locally inefficient subglacial drainage, glacier velocities on the lower glacier remained subdued, partly because the debris attenuated water inputs. This attenuation reduced the occurrence of high amplitude diurnal cycles in the proglacial runoff and confined them to particularly warm weather. Lag times from peak air temperature to peak runoff were long relative to comparable debris-free glaciers. Evaporation of rainfall from debris-surfaces was high, and dependant on the debris permeability, suggesting this is an important water balance component. Under climate warming, it is predicted the ablation of Miage Glacier will increase, but this may be negated given an increase in debris cover.

Antarctic debris-covered glaciers are potential archives of long-term climate change. However, the geomorphic response of these systems to climate forcing is not well understood. To address this concern, I conducted a series of field-based and numerical modeling studies in the McMurdo Dry Valleys of Antarctica (MDV), with a focus on Mullins and Friedman glaciers. I used data and results from geophysical surveys, ice-core collection and analysis, geomorphic mapping, micro-meteorological stations, and numerical-process models to (1) determine the precise origin and distribution of englacial and supraglacial debris within these buried-ice systems, (2) quantify the fundamental processes and feedbacks that govern interactions among englacial and supraglacial debris, (3) establish a process-based model to quantify the inventory of cosmogenic nuclides within englacial and supraglacial debris, and (4) isolate the governing relationships between the evolution of englacial /supraglacial debris and regional climate forcing. Results from 93 field excavations, 21 ice cores, and 24 km of ground-penetrating radar data show that Mullins and Friedman glaciers contain vast areas of clean glacier ice interspersed with inclined layers of concentrated debris. The similarity in the pattern of englacial debris bands across both glaciers, along with model results that call for negligible basal entrainment, is best explained by episodic environmental change at valley headwalls. To constrain better the timing of debris-band formation, I developed a modeling framework that tracks the accumulation of cosmogenic 3He in englacial and supraglacial debris. Results imply that ice within Mullins Glacier increases in age non-linearly from 12 ka to ~220 ka in areas of active flow (up to >> 1.6 Ma in areas of slow-moving-to-stagnant ice) and that englacial debris bands originate with a periodicity of ~41 ka. Modeling studies suggest that debris bands originate in synchronicity with changes in obliquity-paced, total integrated summer insolation. The implication is that the englacial structure and surface morphology of some cold-based, debris-covered glaciers can preserve high-resolution climate archives that exceed the typical resolution of Antarctic terrestrial deposits and moraine records.

An increase in the number of debris-covered glaciers and expansion of debris cover across many glaciers has been documented in many of the world’s major glacierised mountain ranges over the last 100 years. Debris cover has a profound impact on glacier mass balance with thick layers insulating the underlying ice and dramatically reducing ablation, while thin or patchy cover accelerates ablation through albedo reduction. Few debris-covered glaciers have been studied in comparison with ‘clean’ glaciers and their response to climatic change is uncertain. Remote sensing, integrated with field data, offers a powerful but as yet unrealised tool for studying and monitoring changes in debris-covered glaciers. Hence, this thesis focuses on two key aims: i) to test the utility of visible/near infrared satellite sensors, such as TERRA ASTER, for studying debris-covered glaciers; ii) to develop techniques to fully exploit the capability of these satellite sensors to extract useful information, and monitor changes over time. Research was focused on four interrelated studies at the Miage Glacier, in the Italian Alps. First, a new method of extracting debris-thickness patterns from ASTER thermal-band imagery was developed, based on a physical energy-balance model for a debris surface. The method was found to be more accurate than previous empirical approaches, when compared with field thickness measurements, and has the potential advantage of transferability to other sites. The high spatial variability of 2 m air temperature, which does not conform to a standard lapse rate, presents a difficulty for this approach and was identified as an important area for future research. Secondly, ASTER and Landsat TM data are used to map debris-cover extent and its change over time using several different methods. A number of problems were encountered in mapping debris extent including cloud cover and snow confusion, spatial resolution, and identifying the boundary between continuous and sporadic debris. Analysis of two images in late summer 1990 and 2004 revealed only a small up glacier increase in debris cover has occurred, confirming other work’s conclusions that the debris cover on Miage Glacier increased to its present extent prior to the 1990s. A third area of research used ASTER DEMs to monitor surface elevation changes of the Miage Glacier over time to update previous studies. Surface velocities on the glacier tongue were also calculated between 2004-2005 using feature-tracking of ASTER orthorectified visible band imagery and ASTER DEMs. However, ASTER DEMs were found to be rather poor for both applications due to large elevation errors in topographically rough parts of the glacier, which prevented a full analysis and comparison of results to previous surface elevation and velocity studies. Finally, the lithological units of the debris cover were mapped, based on the spectral differences of different rock types in the debris layer, providing information both on the location and concentration of different rock types on the surface. Therefore, the identification in the variation in emissivity throughout the glacier surface can be identified, which in turn has an impact upon calculated surface temperatures and ablation respectively. Overall, this research presents a significant contribution to understanding the impact of a debris layer on an alpine glacier, which is an area of key interest and current focus of many present glaciological studies. Since future glacial monitoring will increasingly have to consider supraglacial debris cover as a common occurrence, due to climate warming impacts of glacial retreat and permafrost melting. This contribution is achieved through the successful application of methods which utilise ASTER data to estimate debris thickness and debris extent, and the lithological mapping of debris cover. Therefore, the potential for incorporating these remote sensing techniques for debris-covered glaciers into current global glacier monitoring programs has been highlighted. However the utility of ASTER derived DEMs for surface elevation change analysis and surface velocity estimations in a study site of steep and varied terrain has been identified as questionable, due to issues of ASTER DEM accuracy in these regions.