The Concept of Steady State, Cyclicity and Debris Unloading of Debris-Covered Glaciers

Abstract

It can easily be expected that debris-covered glaciers show a different response on external forcing compared to clean-surface glaciers. The supra-glacial debris cover acts as an additional transfer layer for the energy exchange between atmosphere and ice. The related glacier reaction is the integral of local effects, which changes strongly between enhanced melt for thin debris layers and considerably reduced melt for thicker debris. Therefore, a realistic feedback study can only be performed, if both the ice flow and the debris-influenced melt is treated with a high degree of detail. We couple a full Stokes representation of ice dynamics and the most complete description of energy transfer through the debris layer, in order to describe the long-term glacier reaction in the coupled system. With this setup, we can show that steady-state conditions are highly unlikely for glaciers, in case debris is not unloaded from the surface. For continuous and complete debris removal from the lowermost glacier tongue, however, a balance of the debris budget and the glacier conditions are possible. Depending on displacement and removal processes, our results demonstrate that debris-covered glaciers have an inherent tendency to switch to an oscillating state. Then, glacier mass balance and debris balance are out of phase, such that glacier advance periods end with the separation of the heavily debris-loaded lowermost glacier tongue, at time scales of decades to centuries. As these oscillations are inherent and happen without any variations in climatic forcing, it is difficult to interpret modern observations on the fluctuation of debris-covered glaciers on the basis of a changing climate only.

Vegetation Ecology of Debris-Covered Glaciers (DCGs)—Site Conditions, Vegetation Patterns and Implications for DCGs Serving as Quaternary Cold- and Warm-Stage Plant Refugia

“…The supraglacial debris has significant effects on the mass balance of glaciers and on flow dynamics. While a thin debris cover enhances melt rate due to reduced surface albedo compared to clean-ice glaciers and consequently a higher absorption of solar radiation, a supraglacial debris mantle of a couple of centimeters or more significantly reduces melt rate and glacier mass loss as heat transfer to the upper edge of the ice body is reduced [27,89,90]. The critical debris thickness separating the two opposing glaciological controls is around 2 cm ([89], Figure 4b), although substrate color may cause deviations from this value in either direction.…”

A low-cost and open-source approach for supraglacial debris thickness mapping using UAV-based infrared thermography

“…Supraglacial debris is present in the ablation zone of many mountain glaciers worldwide (Scherler et al, 2018;Herreid and Pellicciotti, 2020) and can influence their mass balance, geometry and dynamics through the modification of sub-debris ice melt rates (e.g. Rowan et al, 2015;Ferguson and Vieli, 2020;Mayer and Licciulli, 2021;Rounce et al, 2021;Delaney and Anderson, 2022). Important sources of debris supply are steep headwalls, valley slopes and lateral moraines, and subglacial till (e.g.…”

“…Debris deposited on the glacier surface, as well as debris melted out of the ice, accumulates in the ablation zone and often forms a continuous debris layer (e.g. Anderson et al, 2018;Wirbel et al, 2018;Ferguson and Vieli, 2020;Mayer and Licciulli, 2021).…”

Numerical study of the error sources in the experimental estimation of thermal diffusivity: an application to debris-covered glaciers

“…A glacier's response to climate forcing is drastically modified by its debris cover (Østrem, 1959;Rowan et al, 2015;Huo et al, 2021;Mayer and Licciulli, 2021;Nicholson et al, 2021). However, debris cover has only recently been incorporated into global scale glacier models (Rounce et al, 2015) because it was previously assumed to affect only a relatively small part of the glacier (Hock et al, 2019).…”