Understanding anomalous glacier fluctuations


   School of Geosciences

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  Dr A J Dugmore, Dr R Bingham  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

Summary

This field-based project will utilise geomorphology, tephrochronology and remote sensing to better understand how Icelandic glacier fluctuations can be decoupled from climate drivers.

Project background

The overall aim of this project is to understand what may decouple Icelandic glacier fluctuations from climate drivers. This is important because of Iceland’s strategic location close to the atmospheric and oceanic polar fronts, the sensitivity of Icelandic glaciers to climate change, and the vital role of glacial runoff in hydropower generation. Iceland’s many varied glaciers provide a rich source of palaeoenvironmental data, as well as current management challenges.

In the 20th - 21st centuries, changes in summer temperature have driven the fluctuations of many Icelandic glacier margins, but not all fluctuations, for all glaciers, all of the time. Indeed, some of the glaciers that have responded in predictable ways to climate in the present did not do so in the past (and might not in the future).

The neighbouring icecaps of Eyjafjallajökull and Mýrdalsjökull encapsulate these issues- and provide an ideal research area. The glaciers have a high turnover with ice flowing from divides to termini in < 200 years, and their outlets have a wide range of hypsometries and potential topographic pinning points. Some outlets have been strongly affected by subglacial eruptions, whereas others have not.

The Sólheimajökull outlet glacier from Mýrdalsjökull has the longest and most complex record of Holocene fluctuations in Iceland – with ice reaching sea level during the earliest phases of neoglaciation ca. 5ka BP, and anomalous advances through the later Holocene into medieval times. Ice divide migration due to a strong precipitation gradient and the growth of the icecap, might explain this, as might large-scale sub-glacial topographic change related to the 939 AD Eldgjá eruption.

It is known that tephra fall in 1947 AD caused a 7 yearlong re-advance of a northern outlet of Eyjafjallajökull against a regional trend of glacier retreat, but both the short- and longer-term effects of many other ash falls on different parts of the ice caps are unknown.

An outstanding tephra record in southern Iceland, with numerous well-dated tephra layers, can be used to date glacial landforms and deposits. This provides a world-class opportunity to assess spatial and temporal fluctuations of glaciers around entire ice caps in order to gain unparalleled insights into potential drivers of change in the past, present and future, in Iceland and elsewhere.

Research questions

Focussing on Mýrdalsjökull-Eyfjallajökull icecaps and the twin influences of topography and tephra fallout:

1.           What processes could drive ice divide migration (e.g. precipitation gradients and ice cap growth or topographic change driven by volcanic processes)?

2.           What are the influences of topographic pinning points and feedbacks between glacier over-deepening at the snout and the formation of large terminal moraines, on ice-margin responses to climate change?

3.           How has the deposition of air-fall tephra in glacier ablation zones affected their responses to climate?

4.           Can tephra stratigraphy in proglacial areas and empirical data on the impacts of tephra-falls on ablation rates be used to assess the potential impacts of past tephra fallout on glacier fluctuations?

5.           What are the multi-decadal effects on glacier fluctuations of tephra outcrops in current ablation zones (i.e. the re-exposure of tephra layers initially buried within the glacial accumulation zones)

Methodology

A case study approach will be used to develop empirical records of glacier fluctuations around two icecaps in Iceland. Patterns of ice-marginal fluctuations will be mapped using remote sensing and ground survey. In addition to original data collection, a large archive of existing geomorphological mapping and tephrochronology will be mobilised to structure new dating efforts. Geomorphic data will be combined with mapping at a range of scales, which will utilise national topographic datasets and original mapping using UAVs. Tephrochronology will be used to date selected moraine systems and related outwash records. These will be integrated within a GIS and tools developed in Tephrabase (www.tephrabase.org). Electron microprobe analysis and LA-ICPMS will be used to ensure the tephrostratigraphy is rigorous.

Objectives:

To use geomorphological mapping and tephrochronology to date Holocene glacier fluctuations around the Mýrdalsjökull icecap, in order to test ideas of ice-divide migration due to (a) precipitation gradients during ice cap growth and (b) subglacial topographic change.

To integrate tephra stratigraphy in proglacial areas and empirical data on the impacts of tephra-falls on ablation rates to assess the impact of past tephra falls on melting rates in glacial ablation zones and the potential impacts of tephra fallout on glacier fluctuations.

To utilise remote sensing and weather records to assess long-term impacts on ablation from the slow migration of tephra outcrops down glacier (i.e. assess the re-exposure of tephra layers initially buried within the glacial accumulation zones).

Plan:

Year 1: Literature review, analysis of existing tephrochronology, geomorphic records, mapping and imagery, fieldwork in Iceland (summer 2025). Development of research collaborations; write review paper (paper 1).

Year 2: Interpretation of data from fieldwork, geochemical analysis of the tephra layers, synthesis, fieldwork in Iceland (summer 2026). Attendance at international workshops; write paper on the varied influences of tephra on glacier fluctuations (paper 2).

Year 3: Further analysis (as Year 2), interpretation of results, write paper assessing the potential for ice-divide migration and its role in driving glacier fluctuations (paper 3); thesis writing (hybrid format) and international conference presentation.

Training

A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. The student will have training in Edinburgh and in Iceland so they are able to undertake geochemical microanalysis for tephrochronology, utilise and interpret RS data, develop GIS frameworks (in Edinburgh) operate UAVs, and apply tephrochronology in geomorphological mapping (in Iceland).

Requirements

A background in Physical Geography or Earth Sciences, an appetite for substantial fieldwork in remote areas, and a driving licence are required. Experience of GIS, geomorphologic mapping and fieldwork in montane areas is desirable.

Geography (17) Geology (18)

Funding Notes

Funded project see eligibility criteria here - https://www.ed.ac.uk/e4-dtp/how-to-apply/entry-and-eligibility-criteria

References

• Bingham, R.G.; N.R.J. Hulton and A.J. Dugmore 2003. Modelling the southern extent of the last Icelandic ice sheet. Journal of Quaternary Science, 18 (2), 169-181.
• Dugmore, A.J., Thompson, P.I., Streeter, R.T., Cutler, N.A., Newton, A.J. and Kirkbride, M.P., 2020. The interpretative value of transformed tephra sequences. Journal of Quaternary Science, 35(1-2), pp.23-38.
• Dugmore, A.J. and Sugden, D.E., 1991. Do the anomalous fluctuations of Sólheimajökull reflect ice‐divide migration? Boreas, 20(2), pp.105-113.
• Kirkbride, M.P. and Dugmore, A.J., 2003. Glaciological response to distal tephra fallout from the 1947 eruption of Hekla, south Iceland. Journal of Glaciology, 49(166), pp.420-428.
• Kirkbride, M.P. and Dugmore, A.J., 2006. Responses of mountain ice caps in central Iceland to Holocene climate change. Quaternary Science Reviews, 25(13-14), pp.1692-1707.
• Kirkbride, M.P. and Dugmore, A.J., 2008. Two millennia of glacier advances from southern Iceland dated by tephrochronology. Quaternary Research, 70(3), pp.398-411.

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