Recreating the South Orkney Ice Cap: a sentinel of Antarctic Ice Sheet change?

Overview

The sub-Antarctic islands are particularly sensitive to regional environmental change and, therefore, act as indicators for future change on the Antarctic continent further south (e.g. Graham et al., 2017). The islands of the South Orkney Plateau (SOP), just north of the Antarctic Peninsula, still house a number of marine-terminating glaciers (Fig. 1) that are presently experiencing rapid retreat.

The SOP micro-continent also lies in a unique oceanographic position between deep, cold ocean currents formed in the Weddell Sea and the dominant Antarctic Circumpolar Current (ACC) (Fig. 2). Recent observations reveal a poleward shift in the westerly winds that help drive the ACC, which has increased the upwelling of warm Circumpolar Deep Water on to Antarctica’s continental shelves (e.g. Peck et al., 2015). This warm water incursion is thought to be the main driver of recent ice-shelf thinning, glacier acceleration and retreat in Antarctica. With ice sheets increasingly responding to oceanic drivers (including increased heat supply) there is a critical need to improve our understanding of these environmental controls, and the resulting response of the cryosphere. Unfortunately, the links between environmental drivers and the dynamic process of glacier retreat are complex and difficult to explain from observations or models alone.

Over timescales longer than a few decades, unravelling glacier retreat behaviour can only be done by looking to the recent geological past, for example by investigating the response of ice masses during last deglaciation and Holocene warm periods. By having its own discrete ice cap with a relatively simple geometry but in a key environmental location, the South Orkneys are ideally situated for an integrated study of climatic change, oceanic drivers and the associated glaciological response (cf. Hodgson et al., 2014) – information that is critically needed to inform future predictions of Antarctic ice-sheet change.

The aim of this project is, therefore, to understand the pattern and controls of ice retreat of the South Orkney Plateau since the Last Glacial Maximum.

Click on an image to expand

Image Captions

BAS-10009286_crop.JPG to be added to Overview section:
Figure 1: A view of the glaciated South Orkney Islands close to Signy Island where glaciers still terminate in the ocean. Exactly how do these glaciers respond to oceanic warming? (Photo credit: Robert Paterson)

SOP_FigureV1_c.jpg to be added to Overview section:
Figure 2: Location of the South Orkney Plateau (pink outline) in a key oceanographic setting between the Antarctic Circumpolar Current and Weddell Gyre. AP – Antarctic Peninsula. How much warm water has reached glaciers on the SOP in the recent geological past as the ACC has shifted towards Antarctica?
Over timescales longer than a few decades, unravelling glacier retreat behaviour can only be done by looking to the recent geological past, for example by investigating the response of ice masses during last deglaciation. As a discrete ice cap with a relatively simple geometry but in a key location, the South Orkneys are ideally situated for an integrated study of climatic change, oceanic drivers and the associated glaciological response (cf. Hodgson et al., 2014) – information that is critically needed to inform future predictions of Antarctic ice-sheet change.

Methodology

This project will use new marine geophysical and geological datasets alongside numerical ice-sheet modelling to characterise the retreat behaviour of South Orkneys ice masses in response to regional drivers. Specifically, the student will map seafloor landforms and sediments in glacial troughs on the southern SOP to determine deglacial retreat behaviour since the Last Glacial Maximum ~20 000 years ago. They will also derive palaeoenvironmental proxy records (e.g. of sea ice/water mass/oceanic temperature changes) for the same time period from marine sediment cores. Integration of these datasets will enable the processes controlling retreat behaviour (e.g. external forcing like oceanic warming vs. internal glaciological response) to be determined. We will use any available glacial history information (terrestrial and marine; e.g. Dickens et al., 2014) to constrain our understanding of ice retreat patterns and rates.

In order to develop an understanding of the controls on the pattern of glaciation identified from the above approach we will use the PISM ice sheet model to simulate past ice dynamics. We will constrain the model using the marine and terrestrial datasets outlined above and will test the response of the ice masses to a range of potential forcing factors. These will include ocean temperature changes, climate evolution, sea ice melange and local topographic controls. The modelling will therefore identify and quantify the combination of factors that controlled the behaviour of the ice (e.g. Jamieson et al., 2014).
There may be an opportunity to acquire new terrestrial environmental change datasets (lake cores, moss records) from the South Orkneys in collaboration with British Antarctic Survey logistics. Support for sub-Antarctic glacial history work will come from strong links with project mentors Professors Mike Bentley and Dominic Hodgson at Durham and British Antarctic Survey, respectively, and the student will be further supported by other members of the large, energetic Polar research communities in both Cambridge and Durham. Sediment core analyses will involve working away for short periods (a few weeks) at other UK and international laboratories e.g. Alfred-Wegener Institute, Germany.

Project Timeline

Year 1

Develop an understanding of glacier retreat (drivers and glaciological response) for sub-Antarctic island/Antarctic Peninsula glaciers; develop skills for marine geophysical and geological data analysis; determine retreat chronology from marine sediment cores. Organise workshop on sub-Antarctic glacial history.

Year 2

Analyse marine datasets to determine new retreat histories (ice sheet limits and configuration, rates of retreat); produce first proxy records for environmental change from marine sediment cores; become familiar with PISM ice-sheet model and conduct initial set-up experiments; develop writing skills.

Year 3

Finalise environmental change records; numerically model deglacial retreat of the South Orkney ice cap with constraints from marine observations; draft publications; present outcomes to IAPETUS2 and at international conference; draft thesis.

Year 3.5

Submit thesis; finalise remaining publication manuscripts.

Training
& Skills

Techniques of glacial landform and sediment mapping from geophysical datasets, marine sediment core laboratory analysis, and ice-sheet modelling form the core of this project. Applicants must be numerate with some previous experience of environmental geoscience being particularly beneficial. Specific training in all aspects of work will be delivered at the British Antarctic Survey in Cambridge and at Durham University, and at partner institutes for specific laboratory analyses.

The student will be supported in broader skills training via PhD training programmes at the British Antarctic Survey and through the award-winning Career and Research Development (CAROD) group at Durham (thesis writing, writing for publication, presentation skills, enterprise skills etc.). In addition, IAPETUS2 provides a wide range of training opportunities to its students. In respect of this project, one of the most relevant is the ‘Introduction to modelling in Python’ module. The student will gain specific skills in modelling using the Parallel Ice sheet Model (PISM). Environmental modelling skills are highly sought after by environmental and engineering consultancies.

Throughout: The student will be encouraged to write papers for publication throughout the duration of the project. This will benefit their career and will enable us to support the development in writing skills and in going through the publication process. The project is specifically designed to give the student a broad, cross-disciplinary skillset that includes quantitative analyses; training is designed to ensure that the student becomes a well-rounded scientist who is comfortable working independently and in teams.

References & further reading

Dickens, W.A., Graham, A.G.C., Smith, J.A., Dowdeswell, J.A., Larter, R.D., Hillenbrand, C.-D., Trathan, P.N., Arndt, J.E., Kuhn, G., 2014. A new bathymetric compilation for the South Orkney Islands region, Antarctic Peninsula (49°-39°W to 64°-59°S): Insights into the glacial development of the continental shelf. Geochem., Geophys., Geosys., 15, 2494-2514.

Graham, A.G.C., Kuhn, G., Meisel, O., Hillenbrand, C.-D., Hodgson, D.A., Ehrmann, W., Wacker, L., Wintersteller, P., Ferreira, C., Romer, M., White, D., & Bohrmann, G., 2017. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation. Nature Comms., 8, 14798.

Hodgson, D.A., Graham, A.G.C., Roberts, S.J., Bentley, M.J., Ó Cofaigh, C., Verleyen, E., Vyverman, W., Jomelli, V., Saunders, K., M., Selkirk, P.M., Mackintosh, A., Hedding, D.W., Nel, W., Hall, K., McGlone, M.S., Van der Putten, N., Dickens, W.A., Smith, J.A., 2014. Terrestrial and submarine evidence for the extent and timing of the Last Glacial Maximum and the onset of deglaciation on the maritime-Antarctic and sub-Antarctic islands. Quaternary Science Reviews, 100, 137-158.

Jamieson, S.S.R., Vieli, A., Ó Cofaigh, C., Stokes, C.R., Livingstone, S.J. & Hillenbrand, C-D. Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model. Journal of Geophysical Research: Earth Surface. 2014;119:247-263.

Peck, V.L., Allen, C.S., Kender, S., McClymont, E.L., Hodgson, D.A., 2015. Oceanographic variability on the West Antarctic Peninsula during the Holocene and the influence of upper circumpolar deep water. Quaternary Science Reviews, 119, 54-65.

Further Information

Dr Kelly Hogan
British Antarctic Survey (BAS)
Cambridge
https://www.bas.ac.uk/profile/kelgan/#publications
Email: kelgan@bas.ac.uk
Tel: +44 (0) 1223 221617

Dr Stewart Jamieson
Department of Geography
Durham University https://www.dur.ac.uk/geography/staff/geogstaffhidden/?id=8469
Email: Stewart.Jamieson@durham.ac.uk
Tel: +44 (0) 191 3341990

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