Pluri-decadal (1955–2014) evolution of glacier–rock glacier transitional landforms in the central Andes of Chile (30–33° S)

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 (1955Historical ( -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.

Proposal for geomorphological mapping of debris-covered and rock glaciers and its application to Tröllaskagi Peninsula (Northern Iceland)

“…The classifications of Hóladalsjökull as a debris-covered glacier, and the mix of debris and ice flows located in Fremri-Grjótárdalur cirque as rock glaciers, have been proposed and demonstrated by previous experimental studies (Kellerer-Pirklbauer, Wangensteen, Farbrot, & Etzelmüller, 2008;Tanarro et al, 2019) and are in agreement with those defined in previous publications (e.g. Kirkbride, 2011;Janke et al, 2015;Monnier & Kinnard, 2017;Knight, Harrison, and Jones 2019). These formations are located on the northern slope of the Viðinesdalur valley, which flows into the Skagafjorður near the village of Hólar (65°42 ′ N-65°44 ′ N and 18°56 ′ W-19°02 ′ W, 160 m).…”

“…The lower part does not display clearly defined flow structures (Figure 4(D)). Numerous depressions and drainage incisions develop, mainly running W-E and SSW-ENE following the slope direction, revealing internal water flow channels (Janke et al, 2013;Monnier & Kinnard, 2017).…”

Global glacier volume projections under high-end climate change scenarios

“…A further limitation of the model is the simple treatment of katabatic winds, which is modelled by scaling the synoptic wind speed. This could be improved by parameterising katabatic winds based on the grid box slope and the temperature difference between the glacier surface and the air temperature using the Prandtl model (Oerlemans and Grisogono, 2002). Another drawback of the model is the coarse resolution of the grid boxes, which makes it unfeasible to include some process that affects local mass balance such as hillside shading, avalanching, blowing snow, and calving.…”

“…A component of the energy available to melt ice comes from the sensible heat flux, which is related to the temperature difference between the surface and the elevation level and the wind speed. Glaciers often have katabatic (downslope) winds which enhance the sensible heat flux and increase melting (Oerlemans and Grisogono, 2002). It is important to represent the effects of katabatic winds on the mass balance when trying to model glacier melt, particularly at lower elevations where the katabatic wind speed is highest.…”

Decoupled kinematics of two neighbouring permafrost creeping landforms in the Eastern Italian Alps

“…Humlum (1988) defined this type of rock glaciers as "talus-derived rock glaciers", indicating landforms derived from talus accumulation and with no relationships with glacial deposits. The small magnitude and spatial pattern of the elevation change rates are compatible with the downslope expansion of the landform (longitudinal profile adaptation and advection of topographic features due to extensive flow) and is not indicative of massive ice loss (Kääb and Vollmer, 2000;Monnier and Kinnard, 2017). The existence of a small glacier during the LIA in the area occupied by the rock glacier can be likely ruled out.…”