Topic
Bergschrund
About: Bergschrund is a research topic. Over the lifetime, 7 publications have been published within this topic receiving 313 citations. The topic is also known as: rimaye.
Papers
TL;DR: The principal points of water input to a glacier are the bergschrund in cirques and crevasse fields lower on the glacier as discussed by the authors, and the amplitude of subglacial water-pressure fluctuations is large just down-glacier from these points.
Abstract: The principal points of water input to a glacier are the bergschrund in cirques, and crevasse fields lower on the glacier. Crevasse fields commonly occur over convexities at the heads of overdeepenings in glacier beds. The amplitude of subglacial water-pressure fluctuations is large just down-glacier from these points of water input. Erosion by quarrying is likely in such areas. Erosion is thus inferred to be localized on the headwalls of cirques and overdeepenings. In the case of overdeepenings, this leads to a positive feedback process in which a perturbation in the bed causes crevassing at the surface, resulting in erosional forces that accentuate the perturbation. When subglacial water flows up an adverse bed slope leading out of a cirque or overdeepening, much of the viscous energy dissipated is used to warm the water to keep it at the pressure melting temperature as the ice thins and the pressure decreases. In such situations, subglacial conduits are maintained by high water pressures rather than by melting of conduit walls. In the limit, water pressures apparently become so high that water is forced out along the ice-bed interface and the conduits collapse. The products of erosion are then no longer flushed out, and a protective till layer accumulates. By limiting erosion on such adverse bed slopes, this till layer controls the geometry of these overdeepened basins.
220 citations
TL;DR: In this article, a suite of environmental measurements from three cirque glacier bergschrunds, including the first temperature series recorded at depth throughout most of an annual cycle, was reported.
Abstract: Glaciers produce cirques by scouring their beds and sapping their headwalls, but evidence to constrain models of these processes has been elusive. We report a suite of environmental measurements from three cirque glacier bergschrunds, including the first temperature series recorded at depth throughout most of an annual cycle. Compared to the ambient air, the bergschrunds were colder in summer and warmer in winter. Freeze-thaw cycles were rare, and relatively stable subfreezing temperatures persisted from November until May. Using a model for rock fracturing driven by ice segregation, we demonstrate that favorable conditions for fracturing occur not only on the headwall above the glacier, but also within the bergschrund, where periglacial weathering and glacial transport can act together to drive cirque headwall retreat. A small (∼3 °C) year-round decrease in temperatures to conditions more typical of the Pleistocene would likely intensify the weathering process. Though so far ignored in all glacial landscape evolution models, the bergschrund likely plays an essential role in the sculpting of alpine landscapes.
104 citations
TL;DR: The top of Mont Blanc is a dry snow zone as discussed by the authors, and the cold infiltration zone extends between about 4 300 and 3 800 m Its lower limit is lined by large cracks and ice cliffs, similar to bergschrunds near rock faces, which can descend as far as the 0°C isotherm of the mean annual air temperature, 3 100-3 200 m.
Abstract: The top of Mont Blanc is a dry snow zone The cold infiltration zone extends between about 4 300 and 3 800 m Its lower limit is lined by large cracks and ice cliffs, similar to bergschrunds Near rock faces this limit is the bergschrund, which can descend as far as the 0°C isotherm of the mean annual air temperature, 3 100-3 200 m- At Col du Dome ( c , 4 250 m), 15 m deep temperature has increased 18 deg between the years 1911 and 1973, probably due to infiltration which happened there in the last few years The ice in the ablation area is entirely temperate, while in dryer areas of the Alps it may be at 1°C to — 3°C in the vicinity of the firn line
26 citations
TL;DR: In this paper, a semi-implicit ADI scheme is proposed and the effects on mass conservation assessed by a comparison with the original ADI model on an alpine glacier.
Abstract: A number of improvements have been made to an existing two-dimensional ice-flow model applied to an alpine glacier. Analysis of the results of the existing model revealed several shortcomings. The first concerns the lack of mass conservation of the applied alternating-direction-implicit (ADI) scheme. A semi-implicit (SI) scheme is therefore proposed and the effects on mass conservation assessed by a comparison with the ADI scheme. The comparison is first carried out with a simple theoretical glacier for which the improvement is significant. Concerning the real case of Glacier de Saint-Sorlin, France, the initial deviation in mass conservation was much less pronounced such that the new scheme, although improving mass conservation, does not significantly change the modelled dynamics. However, other shortcomings that have a more profound impact on the modelling of glacier behaviour have been identified. The ice thickness may become negative over some gridpoints, leading to an inconsistency. The problem is partly resolved by incorporating extra checks on critical gridpoints at the glacier border. Finally, with the help of ice particle tracking, unrealistic ice settlement above the bergschrund has been identified as the main reason for spurious dynamic effects and has been corrected.
19 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2012 | 1 |
| 2007 | 1 |
| 1991 | 1 |
| 1989 | 1 |
| 1983 | 1 |