Snow cornice dynamics as a control on plateau edge erosion in central Svalbard

Abstract

Snow cornices grow extensively on leeward edges of plateau mountains in central Svalbard. A dominant wind direction, a snowdrift source area and a sharp slope transition largely control the formation of snow cornices in a barren peri‐glacial landscape. Seasonal snow cornice dynamics control bedrock weathering and erosion in sedimentary bedrock on the Gruvefjellet plateau edge in the valley Longyeardalen. Air, snow and ground temperature sensors, as well as automatic time‐lapse cameras on a leeward facing plateau edge were used to study seasonal cornice dynamics. These techniques allowed for monitoring of cornice accretion, deformation and collapse/melting in great detail. The active layer of the top plateau edge is characterized by high moisture content due to rain before freeze‐up in autumn and cornice meltdown during spring thaw. Thus frost weathering there can be very efficient in this otherwise cold and dry environment. Within the first autumn snowstorms, a vertical fully developed cornice was in place (190 cm thick). The backwall surface beneath the thickest part of the cornice remained in the ice segregation ‘frost cracking window’ for almost nine months. Highly weathered rock material from the plateau edge is thus incorporated into the cornice during cornice accretion. Brittle snow deformation leads to the opening of cornice tension cracks between the cornice mass and the snowpack on the plateau. These cracks are a prerequisite for cornice collapses, and often trigger cornice fall avalanches on the slope beneath. In these open cornice tension cracks, weathered rock debris, plucked from the plateau edge, can be visible, demonstrating the erosional property of the cornices. The cornice will either collapse or melt, resulting in suspended sediment transport downslope by cornice fall avalanche or release as rock fall respectively. Therefore, cornices both promote and trigger high weathering rates on Gruvefjellet, and thus control presently the development of the rockwall free faces and the talus cones. Copyright © 2012 John Wiley & Sons, Ltd.

Reconstruction of Loch Lomond Stadial (Younger Dryas) glaciers on Ben More Coigach, north-west Scotland, and implications for reconstructing palaeoclimate using small ice masses

“…The longer shaping of such features over several snowmelt seasons under cold‐climate conditions that would have prevailed for some time after deglaciation at higher altitudes is likely to have contributed to the deep incisions. Furthermore, the development of snow cornices along the plateau edge may also have contributed to gully erosion both directly, through subnival fluvial erosion, and indirectly, by ‘pre‐conditioning’ the plateau edge and enhancing fluvial erosion: observations on Svalbard demonstrate that snow cornices promote and trigger denudation (Eckerstorfer et al ., ,b). We have noted similar associations of cold‐based ice connections and gullies elsewhere in a palaeoglaciological context (e.g.…”

Seasonal Arctic Coastal Bluff Dynamics in Adventfjorden, Svalbard

“…As the snow bank moved, a sediment layer detached from the bluff face, demonstrating that the snow bank had probably frozen to the bluff face prior to deformation (cf. Eckerstorfer et al, 2012). Subsequent snowfall or windblown deposition filled the cavity with sub-horizontal, bowl-shaped layers of snow.…”

Surface morphological types and spatial distribution of fan-shaped landforms in the periglacial high-Arctic environment of central Spitsbergen, Svalbard

“…Moreover, the amount of precipitation is slightly lower than in Adventdalen. These two facts might influence the amount of snow cover that can be accumulated along the edges of the mountain ridges, and consequently limit the number of cornice-fall avalanches, which are very common in the vicinity of Longyearbyen (Eckerstorfer & Christiansen, 2011;Eckerstorfer, Christiansen, Vogel, & Rubensdotter, 2013). Further research on this aspect is needed, and a comparison in terms of the characteristics and morphometry of fans located in the vicinity of Petuniabukta with those of the Adventdalen region would be helpful in better understanding the evolution of fan surface morphology in high-Arctic periglacial settings.…”