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Interactive Modelling of Glacier Climatic Mass Balance in the Karakoram Range Open Access

Descriptions

Other title
Subject/Keyword
Karakoram glaciers
debris-covered glaciers
glacier
interactive atmosphere-alpine glacier modelling
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Collier, Sarah E
Supervisor and department
Bush, Andrew (Earth and Atmospheric Sciences)
Examining committee member and department
Sutherland, Bruce (Physics, Earth and Atmospheric Sciences)
Menounos, Brian (Geography, University of Northern British Columbia)
Kavanaugh, Jeff (Earth and Atmospheric Sciences)
Swaters, Gordon (Math)
Department
Department of Earth and Atmospheric Sciences
Specialization

Date accepted
2015-01-20T10:00:39Z
Graduation date
2015-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Glacier behaviour in the Karakoram region of the greater Himalaya shows strong spatial and temporal heterogeneity and, in some areas, anomalous trends compared with glaciers elsewhere in High Asia. Knowledge of the mass balance fluctuations of Karakoram glaciers, as well as of the important driving factors and interactions between them, is limited by a scarcity of observational data. A novel approach to simulating atmosphere-cryosphere interactions is developed as a multi-scale solution to the paucity of information in this region: a process-based climatic mass balance (CMB) model is interactively coupled with a regional atmospheric model (Weather and Research Forecasting model, or WRF). The coupled model (hereafter WRF-CMB) is used to (1) investigate the surface-energy and climatic-mass fluxes of glaciers in the Karakoram over an ablation season, and (2) compare the traditional, one-way approach to simulations of glacier CMB with an interactive one. Both simulations reproduce observed magnitudes of CMB, with improvements arising from the inclusion of feedbacks from the CMB model to WRF. Supraglacial debris is prevalent in the Karakoram, with an estimated mean proportion of glacier area covered by debris of ~20 %. As debris exerts a strong control on glacier melt, there is a need to determine its influence on glacio-hydrological processes in this region. Therefore, a debris component is introduced into the CMB model that provides the first numerical treatment of moisture fluxes and phase changes in the debris layer to date, using simple parameterizations for the debris ice and water content and the latent heat flux. A case study is performed for the Miage Glacier in the Italian Alps, due to the availability of eddy covariance measurements over glacier debris cover. By comparing a “dry” and a “moist” simulation, the importance of moisture on the surface-energy and climatic-mass balance of debris-covered glaciers is investigated. Sub-debris ice melt during the ablation season is reduced when moisture effects are considered, mainly due to surface heat extraction by the latent heat flux, while during transition seasons, the presence of ice at the base of the debris layer contributes to a reduction in simulated ablation. To investigate glaciological and meteorological changes that arise due to the presence of debris in the Karakoram, the modified CMB model is introduced into WRF-CMB and two simulations are performed: one that treats glacier surfaces as debris-free and one that introduces an idealized specification for debris thickness. Debris cover strongly reduces simulated ablation, particularly at lower altitudes, with a regional mean reduction in mass loss of 30 % over an ablation season. By altering surface boundary conditions, the presence of debris also impacts near-surface meteorological conditions and atmospheric boundary layer dynamics, through changes in the turbulent exchanges of heat and moisture between the glacier surface and the atmosphere. The research presented in this thesis contributes towards an improved understanding of glacier behaviour in the Karakoram and lays the foundation for investigations of glacier change in this region over longer time periods.
Language
English
DOI
doi:10.7939/R3ZP3W79T
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Collier, E., Moelg, T., Maussion, F., Scherer, D., Mayer, C., and Bush, A. B. G.: High-resolution interactive modelling of the mountain glacier–atmosphere interface: an application over the Karakoram, The Cryosphere, 7, 779-7-95, doi:10.5194/tc-7-779-2013, 2013.Collier, E., Nicholson, L.I., Brock, B.W., Maussion, F., Essery, R. and Bush, A. B. G.: Representing moisture fluxes and phase changes in glacier debris cover using a reservoir approach, The Cryosphere, 8, 1429--1444, doi:10.5194/tc-8-1429-2014, 2014.

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