Quantifying supraglacial debris-related melt-altering effects on the
Djankuat Glacier, Russian Federation, Part 1: comparison of surface
energy and mass fluxes over clean and debris-covered ice
Abstract
This work presents a comparison of the meteorology and the surface
energy and mass fluxes of the clean ice and debris-covered ice surfaces
of the Djankuat Glacier, a partly debris-covered valley glacier situated
in the Caucasus. A 2D spatially distributed and physically-based energy
and mass balance model at high spatial and temporal resolution is used,
driven by meteorological data from two automatic weather stations and
ERA5-Land reanalysis data. Our model is the first that attempts to
assesses the spatial variability of meteorological variables, energy
fluxes, mass fluxes, and the melt-altering effects of supraglacial
debris over the entire surface of a (partly) debris-covered glacier
during one complete measurement year. The results show that the
meteorological variables and the surface energy and mass balance
components are significantly modified due to the supraglacial debris. As
such, changing surface characteristics and different surface
temperature/moisture and near-surface wind regimes persist over
debris-covered ice, consequently altering the pattern of the energy and
mass fluxes when compared to clean ice areas. The eventual effect of the
supraglacial debris on the energy and mass balance and the
surface-atmosphere interaction is found to highly depend upon the debris
thickness and area: for thin and patchy debris, sub-debris ice melt is
enhanced when compared to clean ice, whereas for thicker and continuous
debris, the melt is increasingly suppressed. Our results highlight the
importance of the effect of supraglacial debris on glacier-atmosphere
interactions and the corresponding implications for the changing melting
patterns and the climate change response of (partly) debris-covered
glaciers.