Interactive Modelling of Glacier Climatic Mass Balance in the Karakoram Range

  • Author / Creator
    Collier, Sarah E
  • 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.

  • Subjects / Keywords
  • Graduation date
    Spring 2015
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.