Details of Award
NERC Reference : NE/P009492/1
Glaciological Applications of Seismic Full Waveform Inversion (FWI): Insight from a Novel Approach to Evaluating the Seismic Properties of Ice
Training Grant Award
- Lead Supervisor:
- Dr A D Booth, University of Leeds, School of Earth and Environment
- Grant held at:
- University of Leeds, School of Earth and Environment
- Science Area:
- Earth
- Terrestrial
- Overall Classification:
- Earth
- ENRIs:
- Environmental Risks and Hazards
- Global Change
- Science Topics:
- Seismic reflection
- Uncertainty communication
- Antarctic ice
- Ice shelf collapse
- Ice shelves
- Glacial & Cryospheric Systems
- Polar ice
- Snow
- Climate & Climate Change
- Sea level rise
- Glacial processes
- Geophysical surveying
- Oil and gas
- Seismic waves
- Earth Resources
- Glacial hazards
- Ice processes
- Geohazards
- Abstract:
- The collapse of floating ice shelves around the Antarctic coast will result in accelerated global sea-level rise, but our understanding of collapse mechanisms is limited. Ice shelves exert a buttressing force on their tributary ice masses which is removed following a collapse. Tributary glaciers respond by accelerating, thereby delivering more ice to the Southern Ocean. Following the collapse of Larsen B Ice Shelf in, the flow speed of its tributaries increased by >200%. Evidence from climate models suggests that the shallow (firn) layers of Larsen B became denser in the years preceding collapse, creating firn/ice properties that favoured catastrophic collapse. The evolving density of firn can be effectively monitored using seismic surveys - indeed, seismic methods were applied in 2014-5 on the Larsen C Ice Shelf (LCIS; NERC MIDAS project), and evidenced density anomalies consistent with the proposed mechanism for the Larsen B collapse. However, there is current debate about the accuracy of firn/ice density estimates derived from seismic data. Central to this studentship is a recent innovation for characterising physical subsurface properties, including density, from seismic data, termed Full Waveform Inversion (FWI). Our CASE partner, ION-GXT, is a leader in FWI for the seismic hydrocarbon industry, where it is applied to improve imaging of oil-bearing targets. In glaciers, seismic velocity is sensitively linked to density, but most velocity:density conversions are empirical in nature and therefore of limited accuracy. One widespread empirical model founds a velocity:density relationship on ice core data from the South Pole, yet this ice is not necessarily representative of that elsewhere. The power of FWI is that it circumvents empirical models, offering physical subsurface properties (including density) direct from the seismic data. Developing FWI algorithms for glacier applications is the core focus of this studentship. The project has significant bilateral benefits since ION-GXT have identified ice as a valuable testing-ground for developing next-generation FWI methods. Ice is structurally simple compared to the geology of a hydrocarbon province therefore ION-GXT will work with the student to validate generic 'pseudo-elastic' approaches to FWI. Using data from seismic campaigns on the LCIS (NERC MIDAS project, NE/L006707) and British Antarctic Survey (BAS) missions on Thwaites Glacier, the student will assess the compatibility of current survey acquisition with an FWI framework. Observations will be transferred into forthcoming BAS acquisitions on Thwaites Glacier and Rutford Ice Stream, where seismic properties have implications for thermal structure and ice crystal fabric. Furthermore, the student will undertake their own FWI-compliant acquisitions on Norway's Hardangerjokulen ice cap in collaboration with the EvoGlac project (KLIMAFORSK-funded, Bergen University), and in the environs of BAS's Antarctic Rothera Station via a CASS proposal. FWI validation will be provided by independent density estimates at all sites, obtained through borehole logging. Research questions to be addressed are: 1. How should glaciological seismic standards be adapted to implement an FWI workflow? 2. How sensitively does FWI estimate seismic velocity and density with respect to established approaches? 3. Do the internal properties of the target ice masses show structure consistent with the effects of a warming climate? 4. Can the experience of glaciological FWI be transferred into improvements for the industrial seismic setting? FWI methods represented a step-change in hydrocarbon seismic imaging, and equally powerful advantages are envisaged in this unique glaciological application. The collaboration between experts in glacier geophysics (University of Leeds, BAS, Aberystwyth University, Swansea University) and leading industrial insight (ION-GXT) provides the studentship with an exciting and pertinent research challenge.
- NERC Reference:
- NE/P009492/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Industrial CASE
This training grant award has a total value of £88,292
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - RTSG | Total - Student Stipend |
|---|---|---|
| £17,296 | £11,000 | £59,997 |
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