Brief communication: Thinning of debris-covered and debris-free glaciers in a warming climate

• Published in: The Cryosphere
• Main Author: A. Banerjee
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2017
• Subjects: geo; envir; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-11-133-2017; http://www.the-cryosphere.net/11/133/2017/tc-11-133-2017.pdf; https://doaj.org/article/69ad1c8bec6742e1ae12217a760b2c0e

Recent geodetic mass-balance measurements reveal similar thinning rates on glaciers with or without debris cover in the Himalaya–Karakoram region. This comes as a surprise as a thick debris cover reduces the surface melting significantly due to its insulating effects. Here we present arguments, supported by results from numerical flowline model simulations of idealised glaciers, that a competition between the changes in the surface mass-balance forcing and that of the emergence/submergence velocities can lead to similar thinning rates on these two types of glaciers. As the climate starts warming, the thinning rate on a debris-covered glacier is initially smaller than that on a similar debris-free glacier. Subsequently, the rate on the debris-covered glacier becomes comparable to and then larger than that on the debris-free one. The time evolution of glacier-averaged thinning rates after an initial warming is strongly controlled by the time variation of the corresponding emergence velocity profile.