HR: 17:45h
AN: C34A-08    [Abstracts]
TI: Response of debris-covered glaciers to climate change
AU: * Benn, D I
EM: doug@st-andrews.ac.uk
AF: School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL United Kingdom
AU: Lindsey, N
EM: lin@st-andrews.ac.uk
AF: School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL United Kingdom
AU: Kathryn, H
EM: HandsK@halcrow.com
AF: School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL United Kingdom
AB: The presence of supraglacial debris strongly influences glacier ablation, and the mass balance of debris-covered glaciers differs significantly from that of clean glaciers in similar climatic settings. Predicting the response of debris-covered glaciers to climate change is important for hazard mitigation strategies in many high mountain environments, especially where temporary lakes are likely to form on stagnating glacier tongues. Accurate prediction of glacier evolution requires a robust mass balance function which incorporates the effect of debris cover. We present a new model for calculating ablation beneath supraglacial debris layer from meteorological data, based on coupling the surface energy balance and conductive heat flux through the debris layer. The model performs well in a wide range of climatic settings, and results correlate well with measured melt rates in the European Alps and Svalbard. The ablation model is used to construct theoretical mass balance curves for debris covered glaciers, providing surface boundary conditions for glacier flow models. Modelled mass balance curves display reverse gradients on glacier termini where the effect of thickening debris cover with decreasing altitude outweighs that of higher air temperatures. This explains the widely-noted tendency for debris-covered glaciers to stagnate under warming climates. When the mass balance of the glacier as a whole is negative, increasing ablation with altitude causes the lower tongue to decrease in gradient. As gradients and ice thicknesses decline, the process is reinforced by a positive feedback with velocity, so less ice is delivered to the terminal zone. Low surface gradients encourage the formation of supraglacial ponds which can grow rapidly, significantly increasing mass loss from the glacier and potentially posing flood hazards.
DE: 1827 Glaciology (1863)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting