Preprints
https://doi.org/10.5194/tc-2020-228
https://doi.org/10.5194/tc-2020-228

  21 Sep 2020

21 Sep 2020

Review status: this preprint is currently under review for the journal TC.

Modelling steady states and the transient response of debris-covered glaciers

James Ferguson and Andreas Vieli James Ferguson and Andreas Vieli
  • Glaciology and Geomorphodynamics Group, Institute of Geography, University of Zurich

Abstract. Debris-covered glaciers are commonly found in alpine landscapes of high relief and play an increasingly important role in a warming climate. As a result of the insulating effect of supraglacial debris, their response to changes in climate is less direct and their dynamic behaviour more complex than for debris-free glaciers. Due to a lack of observations, here we use numerical modelling to explore the dynamic interactions between debris cover and glacier evolution over centennial timescales. The main goal of this study is to understand the effects of debris cover on the glacier's transient response. To do so, we use a numerical model that couples ice flow, debris transport and its insulating effect on surface mass balance and thereby captures dynamic feedbacks that affect the volume and length evolution. In a second step we incorporate the effects of cryokarst features such as ice cliffs and supraglacial ponds on the dynamical behaviour. Our modelling indicates that thick debris cover delays both the volume response and especially the length response to a warming climate signal. Including debris dynamics therefore results in glaciers with extended debris-covered tongues and that tend to advance or stagnate in length in response to a fluctuating climate and hence remember the cold periods more than the warm. However, when including even a relatively small amount of melt enhancing cryokarst features in the model, the length is more responsive to periods of warming and results in substantial mass loss and thinning on debris covered tongues, as is also observed in remote sensing.

James Ferguson and Andreas Vieli

 
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Status: final response (author comments only)
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James Ferguson and Andreas Vieli

James Ferguson and Andreas Vieli

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Short summary
Debris-covered glaciers have a greater extent than their debris-free counterparts due to insulation from the debris cover. However, the transient response to climate change remains poorly understood. We use a numerical model that couples ice dynamics and debris transport and vary the climate signal. We find that debris cover delays the transient response, especially strong for the extent. However, adding cryokarst features near the terminus greatly enhances the response.