Getting to the Bottom of Ice Shelves

Overview

Models indicate that global sea levels will rise by 0.4 to 0.8 m this century [1], displacing millions of people and exposing coastal cities to extremely significant, in some cases existential, risks. Global sea-level rise is currently dominated by melting ice from fast-flowing glaciers (or ice streams) that drain the Greenland and West Antarctic ice sheets, terminating in the ocean as ice shelves. These ice shelves are vulnerable to collapse [2,3], however the factors controlling ice-shelf vulnerability remain poorly defined largely owing to the difficulty in accessing modern sub-ice-shelf settings. This PhD doctoral training project would aim to address this important knowledge gap by analysing sediments from beneath an ice shelf that collapsed in the past, to explore the precise environmental conditions that triggered its demise and help to understand the behaviour and response of other ice shelves in the near future.

The Minch Ice Stream drained the NW sector of the British-Irish Ice Sheet ~30-15 kyr ago [4,5]. It provides a world-class test-bed on which to analyse and understand processes operating within contemporary ice streams and ice shelves [5]. The Minch Ice Stream, was comparable in size and discharge to the present-day Rutford Ice Stream in West Antarctica but has an exposed bed that preserves abundant geological and geomorphological evidence of periodic ice-shelf stability and ice-shelf disintegrations [4] (Fig.1).

Like the dynamic ice streams of the Amundsen Sea Embayment, West Antarctica, the bed of the Minch Ice Stream also deepens inshore, making it potentially vulnerable to a phenomenon known as marine ice-sheet instability [6,7]. Determining the conditions and processes at the grounding line – the point at which ice shelves start to float – is vital in order to understand whether rapid glacier retreat in marine-based West Antarctica and parts of Greenland today will lead to ice-shelf collapse and trigger the irreversible chain-reaction of marine ice-sheet instability in the near future.

The key aim of this PhD research project will be to determine the changing environmental conditions beneath the ice shelf close to the grounding line of an ice stream, before and after it collapsed. This in turn will help to elucidate the key drivers of grounding-line change and the causes of ice-shelf collapse. Access to comparable contemporary sites, for example in West Antarctica, is normally too hazardous and/or impossible. Therefore, the PhD candidate will conduct a range of different analyses on carefully selected cores from former sub-ice-shelf and grounding-zone settings. Crucially, the student’s data and interpretations, which they will be encouraged to present at conferences and publish in journal articles, will feed into future numerical ice-sheet models – improving predictive capability in ice-sheet change and sea-level rise as the world warms beyond the 1.5°C threshold.

Click on an image to expand

Image Captions

Image owned/copyright (C) T. Bradwell, 2019

Methodology

The research methodology will be interdisciplinary and innovative, supervised by leading experts in their fields. The studentship will involve desktop analytical and experimental laboratory work collecting geological and geophysical data, and conducting detailed sedimentological and biogeochemical analyses. The project will use new and recently acquired high-resolution bathymetric and geophysical data, seabed sediment cores and geochronological data. The studentship will be based in Stirling but will also have access to world-class laboratory facilities at the University of Glasgow as well as other state-of-the-art facilities if/when appropriate (e.g. BOSCORF-NOC, SUERC/East Kilbride, etc).
The research methodology is designed to run in well-defined, but complementary, sequential phases: (i) sediment core analysis with emphasis on physical properties (grain size, X-ray CT, IRD counts, laminography) to understand sediment cyclicity and glaciological setting; (ii) geochemical analysis of sediment cores (XRF) to explore sediment flux provenance (terrestrial vs marine; biogenic vs ice-rafted layers); (iii) micropalaeontological and alkenone analysis to reconstruct palaeo sea-water temperatures, salinities and sea-ice extents. The successful candidate will receive dedicated training in each of the complementary techniques by the supervisory team, and she/he will be expected to contribute to the evolution and enhancement of the methodology throughout the project.

Project Timeline

Year 1

• Review of previous work and methodological capabilities
• Research design and technique familiarisation
• Doctoral training methods programme
• Bespoke training in advanced core analysis methods (eg NERC-BOSCORF training course; Jan 2021)
• Multi-proxy physical properties analysis of sediment cores from sub-ice-shelf and non-ice shelf settings (in Stirling & Durham)
• PhD progression paper (Yr1)
• UK Conference presentation (Sep 2021)

Year 2

• Advanced analytical skills training (ECORD Summer School; Sept 2021)
• Compilation and analysis of downcore geophysical data
• Multi-proxy biogeochemical and alkenone analysis of sub-ice-shelf sediment cores (in Stirling & Glasgow)
• Micro-palaeontological (foraminiferal) analysis
• Manuscript preparation & submission
• UK Conference presentation
• Yr2 Progression review (Sept 2022)

Year 3

• Final lab analyses of key interval material
• Synthesise multi-proxy analyses on common time/depth scale; time-space considerations;
• Data assimilation and pathway to write-up
• Continue manuscript(s) preparation
• International conference presentation
• Start thesis write-up
• Yr3 Progress review (Sept 2023)

Year 3.5

• Finalise & submit thesis for PhD examination

Training
& Skills

Training in specialist and complementary transferable skills is the most important aspect of a PhD programme. This PhD comes with a generous ~£10k Research and Training Support Grant to cover internal and external training, analytical costs and consumables. It will also provide the means to travel to/from sites – allowing the successful candidate to benefit from supervision in more than one UK academic institution (Stirling, Glasgow, Newcastle).

Over the 3.5-year programme, specialist training will be provided in: marine (core and seabed) geophysical data acquisition and interpretation; (marine) sediment core acquisition and analysis techniques, including X-ray CT scanning; multi-sensor geophysical core logging; micro-XRF spectrometry (ITRAX); IR, UV and colour spectrometry; construction of age-depth models using Bayesian methods; alkenone isomer analysis; isoprenoid analysis; micro-palaeontological analysis; statistical techniques; bespoke software training; high-quality oral presentation training; high-quality scientific manuscript and poster production training.

As a NERC-IAPETUS2 student, in Year 1, she/he will also receive more generic doctoral training in research skills and techniques; health and safety in the workplace; effective research environment; research management; personal effectiveness; communication skills; manuscript and grant writing; networking and team-working; thesis troubleshooting; interview preparation and career management. The student will join a vibrant community of staff and postgraduate students at the University for Stirling (BES) and be part of the wider IAPETUS postgraduate groups at Glasgow and Newcastle. The primary supervisor will meet with the student at least monthly; the whole supervisor team will meet with the student at least twice a year.

References & further reading

[1] IPCC 2014. Climate Change 2014: Synthesis Report to the Fifth Assessment Report of the IPCC. https://www.ipcc.ch/report/ar5/syr/

[2] Alley, R. et al. 2007. Science 315, 1838-1841. https://doi.org/10.1126/science.1138396

[3] IPCC, 2018. Global warming of 1.5ï‚°C. An IPCC Special Report. https://www.ipcc.ch/sr15/

[4] Bradwell, T. et al., 2007. Journal of Quaternary Science 22: 609-617. https://doi.org/10.1002/jqs.1080

[5] Bradwell, T. et al., 2019. Science Advances 5, eaau1380. https://doi.org/10.1126/sciadv.aau1380

[6] Schoof, C. 2012. Journal of Geophysical Research 112, F03S28. https://doi.org/10.1029/2006JF000664

[7] Gandy N. et al. 2018. The Cryosphere 12, 3635-3651. https://doi.org/10.5194/tc-12-3635-2018, 2018.

Further Information

For further information or informal applications contact Dr Tom Bradwell:
tom.bradwell@stir.ac.uk

Apply Now