Internal Structure and Current Evolution of Very Small Debris-Covered Glacier Systems Located in Alpine Permafrost Environments

Jean-Baptiste Bosson,Christophe Lambiel

doi:10.3389/feart.2016.00039

Abstract

This contribution explores the internal structure of very small debris-covered glacier systems located in permafrost environments and their current dynamical responses to short-term climatic variations. Three systems were investigated with electrical resistivity tomography and dGPS monitoring over a 3-year period. Five distinct sectors are highlighted in each system: firn and bare-ice glacier, debris-covered glacier, heavily debris-covered glacier of low activity, rock glacier and ice-free debris. Decimetric to metric movements, related to ice ablation, internal deformation and basal sliding affect the glacial zones, which are mainly active in summer. Conversely, surface lowering is close to zero (-0.04 m yr-1) in the rock glaciers. Here, a constant and slow internal deformation was observed (c. 0.2 m yr-1). Thus, these systems are affected by both direct and high magnitude responses and delayed and attenuated responses to climatic variations. This differential evolution appears mainly controlled by (1) the proportion of ice, debris and the presence of water in the ground, and (2) the thickness of the superficial debris layer.

Highlights

Numerous positive and negative feedbacks characterize the current adaptation of glacier systems to climatic changes (WGMS, 2008; Haeberli et al, 2013)
The internal structure and the current dynamical responses to short-term climatic variations were respectively assessed in the three study sites with Electrical Resistivity Tomography (ERT) and Differential GPS (dGPS)
This study proposes a comprehensive analysis of the relationship between the structure and the current evolution of small debris-covered glaciers located in permafrost environments

Summary

Introduction

Numerous positive and negative feedbacks characterize the current adaptation of glacier systems to climatic changes (WGMS, 2008; Haeberli et al, 2013). The melt rate increases below a few centimeters of thickness threshold (2– 8 cm, e.g., Hagg et al, 2008) because more incoming shortwave radiation is absorbed in relation to the albedo reduction. This effect is canceled out by the thickening of the debris layer beyond this threshold: its low thermal conductivity induces an exponential reduction of the ablation rate. The development of decimeters to meters thick debris cover constitutes one of the most efficient negative feedback to current climatic changes, while worldwide glacier shrinkage is expected over the decades (e.g., Huss and Hock, 2015)

Methods

Results

Conclusion