The topographic and structural evolution of Antarctica

Overview

Approximately 98% percent of Antarctica currently lies buried beneath an ice sheet. It has therefore been challenging to understand how the continent has evolved over time. Rock samples from exposed land near the coast, and from offshore, have helped locate Antarctica as a keystone in earlier supercontinents, but the assembly of the Antarctic craton is less well understood. Beneath the ice, geophysical exploration has enabled hypotheses to be developed about the geological makeup and structure of Antarctica (e.g. Ferraccioli et al 2011). What is less often established is the link between these geological data and the operation of surface and tectonic processes over timescales of the ice sheet, present for ca. 34 Million years (Jamieson et al., 2014), and under preglacial conditions when rivers, weathering and hillslope processes operated (Sugden & Jamieson, 2018).

The overarching aim of this project is to understand the long-term tectonic and erosion history of the landscape beneath the Antarctic Ice Sheet.

Why does this matter? Firstly, the landscape is a first-order control on the behaviour of the overlying ice sheet. Despite this, the topography beneath the ice is less well known than the surface of Mars, with implications for ice dynamics and the response to changing climate. Secondly, by better mapping the landscape we might understand the geological evolution of the continent, how it was assembled, reorganised, and modified over timescales of thousands to hundreds of millions of years.
Geophysical characterisation of subglacial topography has improved recently (Fretwell et al., 2013) but other studies have shown significant topographic structural detail can be determined using satellite imagery (Ross et al., 2014; Jamieson et al., 2016). In other regions across the planet, the organisation and shape of topography records a mix of surface and tectonic processes (e.g. Clubb et al., 2016). We will apply a range of techniques to determine Antarctica’s bedrock landscape evolution and to consider its potential impacts on ice sheet flow.
Depending on the student’s specific interests and skills, five fundamental unknowns could be addressed: 1) What is the valley structure beneath the Antarctic Ice Sheet? 2) Is valley structure geologically controlled? 3) What is the relationship between tectonic structure and ice sheet behavior? 4) What does the subglacial geomorphology tell us about pre-glacial fluvial and tectonic interactions? 5) Can the subglacial topography provide insight into past ice sheet extent and flow during warm periods (e.g. super-interglacials)?

Click on an image to expand

Image Captions

UnderAntarctica.png – Figure1: We need to add more detail to the understanding of the landscape beneath the ice: it records patterns of past ice sheet and landscape evolution.

MODISTopography.jpg – Figure2: MODIS mosaic (grey) and related sub-ice topography (colours) illustrating the subglacial valley structure detail that can be extracted from satellite data of the ice surface in the Ellsworth-Whitmore Mountains of West Antarctica.

Methodology

We propose an approach that will combine satellite image mapping, morphometric (shape) analysis and geophysical data interpretation: The student will use satellite mosaics such as RADARSAT (Jezek et al., 1999, Annals of Glaciology) and the MODIS Mosaic of Antarctica (MOA: Haran et al., 2014, NSIDC) in combination with surface digital elevation models (REMA: Howat et al., 2019; Cryosat: Slater et al., 2018) to map subglacial valleys and ridges to generate a birds-eye view of the topographic network of Antarctica. We propose that a computer vision mapping technique can be developed by the student to semi-automate this mapping. The student will then conduct morphometric analysis in two ways: Firstly, using the recently produced high-resolution REMA DEM and open-source software developed by the supervisory team (lsdtopotools.github.io) we will analyse areas of exposed mountains, such as ridgetops and valleys, to better understand their process of evolution, using analogues from other countries to support our findings. The recently generated GeologyMap of Antarctica will supplement this analysis so that we can identify if there are geologic controls on the morphology of the Transantarctic Mountains and other areas of exposed topography. Secondly, morphometric analysis of the network of subglacial valleys mapped from RADARSAT will help identify potential large and small-scale structures in the landscape that could be linked to ancient, and perhaps more modern, tectonics. Finally, these analyses will be supported by investigation of existing radio echo sounding (RES) data that provides detail on subglacial bed morphology, and by analysis of geophysical potential field data (magnetics and gravity) to make links between subglacial topography, geology and tectonics.
This project will suit someone who is comfortable with geophysics and/or quantitative remote sensing although suitable training will be provided.

Project Timeline

Year 1

Develop valley and ridge structure extraction techniques from ice surface mosaics. Learn morphometric techniques. Review literature and consider Antarctic and non-Antarctic analogues for processes. Training on RES analysis and scripting/python.
From first year, and throughout the project the student will be encouraged to write papers for publication. This will benefit their career and will enable us to support the development in writing skills and in going through the publication process. In addition, from the outset the student will be involved with the Scientific Committee for Antarctic Science (SCAR: www.scar.org) via its PAIS and SERCE groups science research programmes. These SRPs aim to understand the solid earth behaviour and the past ice sheet dynamics of Antarctica and the student will therefore have significant opportunity to contribute to the goals of SCAR and will have unique opportunities to network with leading scientists in the field.

Year 2

Conduct morphometric analysis of REMA, SCAR Geology Map and the valley structures. Supplement analysis with RES data to understand topographic detail. Drafting associated papers.

Year 3

Integration of potential field data and overall interpretation of landscape structure. Consideration of implications of topographic structure on ice sheet behaviour. Drafting associated papers.

Year 3.5

Complete write-up of thesis (we anticipate this will be a thesis produced as a set of papers).

Training
& Skills

IAPETUS2 provides a wide range of training opportunities to its students. In respect of this project, two of the most relevant are the ‘Introduction to modellng in Python’ and ‘Advanced statistics in R’ modules, but we will discuss the student’s needs and interests at the outset of the project.
In addition, training in RES data analysis and interpretation will be provided within the project. The student will gain specific skills in data processing, analysis and 2.5D visualisation of geophysical data using geophysical software packages. Opportunities to gain experience in the acquisition of directly analogous near-surface geophysical methods (i.e. ground penetrating radar) can also be made. Geophysical skills are highly sought after by environmental and engineering consultancies.
This project will also provide training in how to extract quantitative information from DEMs, as well as Python programming for topographic analysis and running command line tools. The student will gain experience in efficiently analysing large and complex datasets.

References & further reading

Clubb, F.J., Mudd, S.M., Attal, M., Milodowski, D.T. & Grieve, S.W.D. The relationship between drainage density, erosion rate, and hilltop curvature: Implications for sediment transport processes. Journal of Geophysical Research: Earth Surface. 2016, 121(10), 1724.

Ferraccioli, F., Finn, C.A., Jordan, T.A., Bell, R.E., Anderson, L.M. & Damaske, D. East Antarctic rifting triggers uplift of the Gamburtsev Mountains. Nature. 2011; 479, 388-392.

Fretwell, P. and many others. Bedmap2: improved ice bed, surface and thickness datasets for Antarctica. The Cryosphere. 2013. 7, 375-393.

Howat, I.M., Porter, C., Smith, B.E., Noh, M.-J., and Morin, P. The Reference Elevation Model of Antarctica. The Cryosphere. 2019; 13, 665-674.

Jamieson, S.S.R., Stokes, C.R., Ross, N., Rippin, D.M., Bingham, R.G., Wilson, D.S., Margold, M. & Bentley, M.J. The Glacial Geomorphology of the Antarctic Ice Sheet Bed. Antarctic Science. 2014; 26, 724-741.

Jamieson, S.S.R., Ross, N., Greenbaum, J.S., Young, D.A., Aitken, A.R.A., Roberts, J.L., Blankenship, D.D., Sun, B. & Siegert, M.J. An extensive subglacial lake and canyon system in Princess Elizabeth Land, East Antarctica. Geology. 2016; 44, 87-90.

Ross, N., Jordan, T.A., Bingham, R.G., Corr, H.F.J., Ferraccioli, F., Le Brocq, A., Rippin, D.M., Wright, A.P., Siegert, M.J. The Ellsworth Subglacial Highlands: inception and retreat of the West Antarctic Ice Sheet. Geological Society of America Bulletin. 2014; 126(1-2), 3-15.

Slater, T., Shepherd, A., McMillan, M., Muir, A., Gilbert, L., Hogg, A.E., Konrad, H. & Parrinello, T. A new digital elevation model of Antarctica derived from Cryosat-2 altimitry. The Cryosphere. 2018. 12, 1551-1562.

Sugden, D.E. & Jamieson, S.S.R. The pre-glacial landscape of Antarctica. Scottish Geographical Journal. 2018; 134, 203-223.

Further Information

Dr. Stewart Jamieson, Department of Geography, Durham University, Durham, UK. Stewart.Jamieson@durham.ac.uk Tel: +44 (0)191 3341990

Dr. Neil Ross, School of Geography, Politics and Sociology, Newcastle, UK. Neil.Ross@ncl.ac.uk Tel: +44 (0)191 2085111

Dr. Fausto Ferraccioli, British Antarctic Survey, Cambridge, UK. ffe@bas.ac.uk +44 (0)1223 221400

Dr. Fiona Clubb, Department of Geography, Durham University, Durham, UK. Fiona.j.clubb@durham.ac.uk +44 (0)191 3341852

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