Abstract
Abstract. Three glacier–rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955–2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr−1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr−1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere against climate change.
Highlights
Glacier–rock glacier interactions related to Holocene glacier fluctuations (e.g. Haeberli, 2005) and the current evolution of small debris-covered glaciers having survived to the postLittle Ice Age (LIA) warming (e.g. Bosson and Lambiel, 2016) are important issues in high-mountain studies
The methods used in this study first allowed to obtain series of images depicting at first sight conspicuous landscape evolutions: Figs. 6, 7, and 8 show the orthophotos and orthoimages obtained at each site together with the delineated boundary between debris-covered and rock glacier morphology areas and the front slope base at each time
As mentioned in the “Material and methods” section, no reliable and complete digital elevation model (DEM) could be obtained for the Navarro Valley in 1955, which explained the lack of elevation change measurements at Navarro and Presenteseracae
Summary
Glacier–rock glacier interactions related to Holocene glacier fluctuations (e.g. Haeberli, 2005) and the current evolution of small debris-covered glaciers having survived to the postLittle Ice Age (LIA) warming (e.g. Bosson and Lambiel, 2016) are important issues in high-mountain studies. Bosson and Lambiel, 2016) are important issues in high-mountain studies. They may provide key insights into the mechanisms of rock glacier development (Dusik et al, 2015) and of cryosphere stability and resilience against climate changes; the latter topic is of societal importance in arid–semiarid mountain areas, where the potential permanence of underground solid water resources subsequent to deglaciation may constitute a nonnegligible water resource Kääb et al, 1997; Krainer and Mostler, 2000; Ribolini et al, 2007; Monnier et al, 2014; Janke et al, 2015). Kinnard: Pluri-decadal (1955–2014) evolution of glacier–rock glacier transitional landforms
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