Decadal evolution of a very small heavily debris-covered glacier in an Alpine permafrost environment

Abstract

ABSTRACT. Glacier response to climate forcing can be heterogeneous and complex, depending on glacier system characteristics. This article presents the decadal evolution of the Tsarmine Glacier (Swiss Alps), a very small and heavily debris-covered cirque glacier located in the Alpine periglacial belt. Archival aerial photogrammetry and autocorrelation of orthophotos were used to compute surface elevation, volume and geodetic mass changes, as well as horizontal displacement rates for several periods between 1967 and 2012. A GPR survey allowed us to investigate glacier thickness (15 m . This might be explained by the combined influence of debris cover, shadow, snow redistribution and permafrost conditions on this very small glacier.

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

“…However, the proportion of cold ice seems low at the base of the debris-covered glacier zones if we consider, as other authors, basal sliding signature as an indicator of temperate ice (Mayer et al, 2006;Bingham et al, 2008; Figure 8). The basal sliding pattern also clearly appears at the decadal timescale at Tsarmine glacier (Capt et al, 2016). The influence of water here is likewise supported by the marked seasonal variation of surface velocities, the recording of maximum horizontal velocities in early summer when the water production is very high and field observations and audition of water circulation.…”

“…The high measured resistivities (>500 k m, with extended zones >5000 k m) reveal that these sectors are composed of massive sedimentary ice with probably low debris content. The current thickness of the glaciers is unknown, except in Tsarmine where a GPR survey in 2015 revealed respectively mean and maximum thickness of 15 and 35 m (Capt et al, 2016). According to its dimension and the height of the surrounding moraines, this glacier is likely the thickest of the three studied here.…”

“…The Tsarmine glacier is identified in the Swiss glacier inventory (Fischer et al, 2014). The decadal mass balance variations and current geometry of this 4 × 10 6 m 3 ice mass are presented in Capt et al (2016). These results exhibit its atypical behavior over time (mass balance divergence since the 2000s) and space (reversed ablation pattern) in comparison with other local glaciers, due to the combined influence of the decimeters thick debris cover, permafrost conditions, avalanching and solar shading on this very small glacier.…”

“…The surface topography is undifferentiated, except in Tsarmine, where many arcuate rounded ridges are present. They were generated by the compressive stress induced during the downward migration of the snow and ice accumulated in the 1960s to mid-1980s period (Capt et al, 2016). Water runoff is observable or audible in summer especially in gullies (Figure 2).…”

“…These particular systems are composed of a flowing ice mass mainly formed by the metamorphosis of snow (WGMS, 2008;Cogley et al, 2011;Dobhal, 2011), and associated, possibly frozen, debris accumulations. The existence of this type of glacier is especially related to the influence of the surrounding relief upon snow accumulation and shadow effects (Paasche, 2011;Capt et al, 2016). The size class of glaciers remains an open question in glaciology but 0.01-0.5 km 2 appear suitable thresholds to define very small glaciers (e.g., Kuhn, 1995;Fischer et al, 2014;Pfeffer et al, 2014).…”