Details of Award
NERC Reference : NE/J014419/1
Geotechnical centrifuge modelling of crevassing in glaciers and ice sheets
Grant Award
- Principal Investigator:
- Professor BR Rea, University of Aberdeen, Sch of Geosciences
- Co-Investigator:
- Dr AJ Brennan, University of Dundee, Civil Engineering
- Grant held at:
- University of Aberdeen, Sch of Geosciences
- Science Area:
- Earth
- Marine
- Terrestrial
- Overall Classification:
- Earth
- ENRIs:
- Global Change
- Science Topics:
- Climate & Climate Change
- Palaeoenvironments
- Glacial & Cryospheric Systems
- Materials testing & eng.
- Toughness
- Abstract:
- Omitted from the 2007 IPCC Fourth Assessment Report on Climate Change was the potential contribution from ice sheets to global sea level. This reflected the level of uncertainty with respect to the ice dynamics (motion) and mass balance (snow and ice accumulation vs. snow and ice loss) of the extant ice sheets in Greenland and Antarctica. One potential key control on ice dynamics is glacier crevassing which can facilitate the routing of surface melt water to the ice sheet bed leading to increased sliding velocities on outlet glaciers. Additionally, crevassing controls the production of icebergs at marine terminating margins, through which the Greenland Ice Sheet disposes of ~50% and the Antarctic Ice Sheet almost all of their respective annual ice loss. Iceberg production (calving) may be through a combination of both bottom-up and top-down crevassing but atmospheric warming, by increasing the availability of melt water to fill surface crevasses, is likely to be the main driver of change, in the short term at least. Only recently have advances been made in the development of physics-based crevassing/calving relationships with incorporation into predictive numerical models. These advances are vital for improving our predictions for the response of the big ice sheets to future warming. However, only one study to date has tested these physics-based crevassing relationships and then only for shallow water-free crevasses. Given the current research focus on glacier crevassing, there is an urgent need to test crevassing models. To do this in the field is however challenging, due to difficulties of working in crevasse zones of glaciers, measuring the depth of what ultimately ends in a hairline crack at depth and associating the crevasse with the instantaneous stress/strain field. Project Partner DB has a project in preparation to deploy instrumentation for continuous water level monitoring in crevasses on Kronebreen, Svalbard. Geophysical imaging is currently problematic for example signal attenuation on 'warm' temperate glaciers, signal interference from adjacent crevasses in crevasse fields and obtaining the resolution to image the crevasse (crack) tip. Likewise controlling water-depth to force crevasse penetration would present significant challenges for example, the volume of water needed for filling a crevasse or connection with the englacial drainage system leading to water loss etc. Field monitoring of glacier crevassing is thus in its infancy. A modelling approach therefore represents an ideal way forward. However, lab-floor models are useless because the stresses relevant to crevasse propagation increase as a function of both the self-weight stress (gravity x ice density x ice thickness) and crack length i.e. the crevasse depth. The geotechnical centrifuge is a unique modelling tool which allows the magnitude self weight stresses to be reproduced, with stress equivalence between the prototype (real world) and the model by scaling down the dimensions in the model but 'enhancing' gravity. This is achieved by 'flying' (spinning) the model in the centrifuge such that an Nth scale model flown at N times gravity generates the same self-weight stress as the prototype. Scaling relationships are already established for all the parameters relevant to this study so no scaling issues are anticipated, but the standard modelling of models centrifuge technique will be employed to confirm this. Then a series of models will be run, replicating the stress levels experienced in a prototype glacier section ~50x80x50 m. Pre-cast crevasses will be filled with water to facilitate step-wise full-depth crevasse penetration allowing the current state of the art physics-based models to be tested. This project will provide a proof of concept which will facilitate further grant applications where more complex models (e.g. bottom-up and top-down) can be built and used to test and develop physical models.
- NERC Reference:
- NE/J014419/1
- Grant Stage:
- Completed
- Scheme:
- Small Grants (FEC)
- Grant Status:
- Closed
- Programme:
- Small Grants
This grant award has a total value of £51,585
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DA - Estate Costs | DI - Staff | DI - T&S | DA - Other Directly Allocated |
|---|---|---|---|---|---|---|
| £7,515 | £8,086 | £13,332 | £1,244 | £6,094 | £5,922 | £9,393 |
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