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Exploring ‘collapse structures’ as a hitherto unidentified component of glacier mass loss


Project Description

This project aims to test the hypothesis that failure to account for the formation of large subglacial cavities under some glaciers may result in severe underestimations of glacier mass loss. Glacier melting is usually measured as loss from the surface, but this cavity formation is important because it means that melting also occurs from underneath. Consequently, the rate at which such glaciers are thinning and shrinking is actually greater than previously considered. This has potentially important implications for our measurements of present (and estimates of future) mass balance changes of these glaciers under a warming climate.

The cavities we are interested in have been identified through the appearance of cauldron-like ’collapse structures’ present in the surface of the lower reaches of some Alpine and Arctic glaciers. These structures are not unlike those created in ice that overlies localised geothermal hot-spots, such as the Icelandic ice-cap Vatnajökull, that lies over the volcanic crater Grimsvötn. Comparable structures have been reported from elsewhere, but are unrelated to volcanism. These features are characterised by arcuate crevasses/fractures, formed as a result of the partial collapse of ice into the cavity below. These cavities are a response to a combination of the melting of both subglacial channel walls and ceilings.

Glacial collapse structures have received virtually no study to date, yet we believe such structures may be common. We thus hypothesise that these collapse structures and underlying cavities may be significant in glacier mass balance for two reasons:

1. Substantial outflow of water from these glaciers suggests that subglacial roof and wall melt-back may be contributing to overall mass loss in a previously unacknowledged way.

2. Subsequent complete collapse of such structures into the underlying cavity represents a significant ’jump’ in the rate at which a glacier retreats. In other words, a collapse may serve to sever the stagnant snout from the rest of the glacier, accelerating the apparent rate at which a glacier retreats.

Both of these hypothesised consequences have a significant, yet currently unquantified, potential impact on glacier mass balance, and there is therefore a need to better understand the significance of these glaciological features and their role on glacier retreat. The driving purpose of this proposal is to explore how common and widespread these collapse structures are throughout Arctic and Alpine locations, and then to carry out targeted fieldwork (probably in Switzerland) to explore in depth the evolution and role of collapse structures in glacier mass balance.

Funding Notes

This NERC ACCE DTP studentship is fully funded for 3.5 years in the first instance, and students must complete their PhD in four years. The studentship covers: (i) a tax-free annual stipend at the standard Research Council rate (£15,009 for 2019-2020, but typically increases annually in line with inflation), (ii) research costs, and (iii) tuition fees at the UK/EU rate. You can extend your funding period for up to 3 months by applying for an industrial placement.

References

ENTRY REQUIREMENTS: Students with, or expecting to gain, at least an Upper Second Class Honours degree, or equivalent, are invited to apply. The interdisciplinary nature of this programme means that we welcome applications from students with backgrounds in any relevant subject that provides the necessary skills, knowledge and experience for the DTP, including environmental, biological, chemical, mathematical, physical and social sciences.

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