Structures and Deformation in Glaciers and Ice Sheets - a Research Project
Recently, a major synthesis of structural glaciology has been published by Stephen Jennings and Michael Hambrey in the prestigious American academic journal Reviews of Geophysics. This synthesis covers 200 years of glaciological research on the topic, including 50 years by Michael. For the general reader, the main findings are summarised in the first paragraph below, while the full length paper (134 pages long) is outlined in the Abstract in the second paragraph. Both short and long articles are available for free download. We hope our readers find these articles of interest.
Grosser Aletschgletscher, Swiss Alps, in 2008 (Photo Michael Hambrey).
Plain Language Summary
Glacier ice covers about 10% of Earth's land surface and has a profound influence on human activity. As ice continues to melt around the world in response to anthropogenic and natural global heating, the dynamics of glaciers and ice sheets are changing. As this review emphasizes, understanding glacier dynamics is achieved by investigating the brittle and ductile structures that characterize glaciers. The importance of this aspect of glaciology is increasingly being recognized, and draws on its close affinity with structural geology, although interaction between the disciplines to date has been limited. Brittle structures include crevasses, crevasse traces, and a wide variety of faults. Ductile structures include foliation (a layered structure that results from deformation), folds on many scales, and less universally known structures such as ogives and boudins.
This review describes, illustrates, and explains the origin of these structures in terms of stress and strain. It also considers areas of controversy, unresolved issues, and offers pointers to future research. A more comprehensive understanding of glacier and ice sheet dynamics is needed to better predict their response to climate change, and ultimately their contribution to sea-level rise. Structural glaciology can play a large part in this process.
https://eos.org/editors-vox/glacier-structures-history-written-in-the-iceScientific abstract
The aims of this review are to: (a) describe and interpret structures in valley glaciers in relation to strain history; and (b) to explore how these structures inform our understanding of the kinematics of large ice masses, and a wide range of other aspects of glaciology. Structures in glaciers give insight as to how ice deforms at the macroscopic and larger scale.
Structures also provide information concerning the deformation history of ice masses over centuries and millennia. From a geological perspective, glaciers can be considered to be models of rock deformation, but with rates of change that are measurable on a human time-scale. However, structural assemblages in glaciers are commonly complex, and unraveling them to determine the deformation history is challenging; it thus requires the approach of the structural geologist.
A wide range of structures are present in valley glaciers: (a) primary structures include sedimentary stratification and various veins; (b) secondary structures that are the result of brittle and ductile deformation include crevasses, faults, crevasse traces, foliation, folds, and boudinage structures. Some of these structures, notably crevasses, relate well to measured strain-rates, but to explain ductile structures analysis of cumulative strain is required. Some structures occur in all glaciers irrespective of size, and they are therefore recognizable in ice streams and ice shelves. Structural approaches have wide (but as yet under-developed potential) application to other sub-disciplines of glaciology, notably glacier hydrology, debris entrainment and transfer, landform development, microbiological investigations, and in the interpretation of glacier-like features on Mars.
http://doi.org/10.1029/2021RG000743