Abstract
Abstract
Supraglacial debris strongly modifies melt rates on debris-covered glaciers, yet simulating this effect remains challenging because modelling the full surface energy balance (SEB) and the vertical conduction of heat through the debris layer requires many (unknown) parameters, which are often poorly constrained and highly site-specific. Here, we develop a physically based parameterization and calibration procedure for sub-debris melt rates, which links a simplified formulation of the SEB to heat conduction through the debris. The model is tuned using mass-balance measurements and debris surface temperatures from the debris-covered region of the Djankuat Glacier (Caucasus) and uses a minimal number of input data to reproduce the observed debris-related melt-modification effects. An optional relative melt enhancement for thin debris extends the procedure into a regime where the model physics are not valid, and sub-debris melt is governed by other processes than heat conduction alone. This allows the model to be applied in (large-scale and long-term) debris-covered glacier evolution frameworks where the full range of debris thicknesses could occur. As hard-to-constrain inputs have been replaced with simplified and tunable parameters, the approach balances the trade-off between model complexity and physical realism and can be transferred to other debris-covered glaciers, provided that sufficient observations for model calibration are available.