Testing the extent and timing of past glaciations on the largest sub-Antarctic island, South Georgia

Lead Research Organisation: University of Exeter
Department Name: Geography

Abstract

The sub-Antarctic islands are ideally placed to investigate past ice and climate changes, with records of their ancient glaciation important for understanding various aspects of the Earth system. Due to the islands' unique location between warm-maritime and cold-polar climates, the size of sub-Antarctic ice-cap advances provide a potentially valuable means of calibrating the sensitivity of ice-sheet models, ensuring the climate parameters used to force them are realistic and the outputs 'good' for the future. Variations in the scale and timing of glacial events can also provide critical information on the mechanisms and phasing of climate changes between regions and hemispheres. The same data constrain the whereabouts and persistence of glacial refugia, and inform biologists on the geological conditions governing the evolution and diversity of life in the Southern Ocean.
To improve ice-sheet models, explain patterns of climate change, and interpret the biodiversity of the world's oceans, information on sub-Antarctica's glacial past is required. However, fundamental questions relating to the age, magnitude, and number of past glaciations remain unanswered. For the largest sub-Antarctic island, South Georgia, at least one major glacial advance is already known from ice-carved troughs and sediment ridges (moraines) found on the sea-floor of the shallow shelf surrounding the island today. Yet its age is unknown. As in other parts of Antarctica, the most recent episode of glaciation - The Last Glacial Maximum - is likely to have left behind the best record of ice-cap advance and melting. However, even here, there is no consensus, with two conflicting hypotheses prevailing: one suggesting a limited ice extent, restricted to the near-shore fjords; the other proposing that the ice cap was extensive, reaching the outer parts of the shelf around most of the island. Answers to which hypothesis is correct lie in the study of the submarine topography and sediments, which have yet to be investigated in any detail.
This project proposes a pioneering study to examine the extent and timing of past glaciations on South Georgia, from a marine perspective, for the first time. I will provide a robust test of the hypotheses that, either: (i) the Last Glacial Maximum ice cap was of restricted extent and thus that one or more major ice cap glaciations that reached outer shelf limits pre-date the last glacial period; or that (ii) the Last Glacial Maximum ice cap was extensive, and a chronology of retreat is recorded in the shelf's landscape and sediments.
Existing and newly-collected sonar bathymetry data will be utilised to map out the glacial features on the South Georgia shelf in unprecedented detail. Six sediment cores, among the first recovered from the shelf, will be analysed and dated. The project will target moraines marking the limits of former ice-caps, from the shelf edge to the coastal fjords. I will determine the age of the most extensive glaciation, and the age of intermediate retreat or terminal limits. Physical analyses of sediments will reconstruct environmental conditions during and since the Last Glacial Maximum, to the present day, and perhaps through older cold or warm periods. Resolving the number and extent of former shelf glaciations preserved in sub-Antarctic records will be a major outcome of the project, as will vital new information on the behaviour and reach of the Last Glacial ice cap.
New records will be set in the context of Earth's climate and evolutionary histories, and form the first marine palaeo-constraints on sub-Antarctic glaciation, benefiting modellers, climate scientists and biologists. The project will also provide baseline geological data for use by habitat mapping projects and fisheries. This research will shed new light on Southern Ocean ice and climate history, and set a new agenda for future study of past glacial change in the near-polar regions.

Planned Impact

A. Who will benefit from this research?
Academics: This research will benefit glaciologists predicting the impacts of future climate change on the planet, especially those modelling ice sheets in the Southern Hemisphere who require palaeo-data to constrain simulations. It will serve biologists mapping the biodiversity of the South Georgia shelf, where the glacial history is critical for interpreting the evolution of marine fauna. Climatologists will benefit from new data studying the forcing of glacial changes, with the potential for insights into the regional and global climate system. Habitat mappers who require details of seabed geology to develop habitat models, will also be direct beneficiaries of this work.
Government/Industry: The Government of South Georgia and South Sandwich Islands (GSGSSI) will benefit from new geological survey in the protected South Georgia Maritime Zone (SGMZ). Via improved habitat and biodiversity information, this research will directly impact upon management of the marine realm. Fisheries will have access to baseline geological data currently unavailable for the SGMZ. Environmental managers can also use new results to place recent glacial retreat into long-term context; glacier recession has come at environmental cost through the spread of invasive species, and further glacier melting is a key issue facing management of the island.
Society: Work on glacier change, particularly through improving constraints on ice-sheet models has impacts for society as a whole because of the risk of future ice-sheet change and sea-level rise. Schools and a work experience student will benefit from post-cruise activities, while museums will benefit from a new non-specialist publication. As an UK overseas territory, South Georgia also possesses a history of science exploration that is relevant to all of British society.
Project: The project will benefit PI Graham and his collaborators. Work will foster relations between NERC centres (BAS), facilities (e.g. BOSCORF) and partner universities in Durham and Leipzig.

B. How will they benefit from this research?
Academia: Ice sheet modellers will be provided with key datasets for use in future models. They will be kept informed of results at meetings, through the scientific literature, and via the SCAR-ACE Community Ice Sheet project. Key datasets will be communicated to a team of biologists working on South Georgia's marine biodiversity. Constraints on the timing and extent of shelf glaciations will be integrated with the interpretation of recent biodiversity surveys on the shelf, via planned meetings and a workshop, to shed light on the evolution of marine life in sub-Antarctic waters. Climate scientists and habitat mappers will be provided with new geological records, delivered through online databases, scientific papers, meetings (e.g. the International Forum on the sub-Antarctic) and a workshop, which will improve knowledge of past climates, and help produce better habitat models.
Government/Industry: Bathymetry and core data will be provided to the GSGSSI, UKHO and fisheries, via online metaservers (e.g. PANGAEA) and an existing online GIS database run by the South Georgia government. New baseline data on the geology of the shelf will be of wide benefit to industry, and work with biologists will help in future conservation decisions on South Georgia's marine ecosystems.
Society: Schools will benefit from interaction with polar science. A work experience student will have the opportunity to participate in a placement to gain experience of academic life. A non-specialist brochure will spread results widely, via the South Georgia and SPRI museums.
Project: The project will allow the proponent to further develop skills in marine geoscience research, gain experience as a PI, develop skills in managing projects and budgets, and benefit from the opportunity to convey results through journals, impact activities, and conferences.

Publications

10 25 50

Related Projects

Project Reference Relationship Related To Start End Award Value
NE/K000527/1 01/12/2012 31/07/2013 £59,364
NE/K000527/2 Transfer NE/K000527/1 01/08/2013 30/11/2014 £42,972
 
Description Summary of findings and outcomes

- Through the collation of sea-floor topographic datasets as part of this project, we have been able to map out the glacial landforms across the entire South Georgia continental shelf, revealing the imprint of past ice cap advance and retreat on South Georgia in unprecedented detail. Sampling of some of the moraine features that comprise this submarine landscape has been successful, and we have been able to constrain the ages for the sediments which tie the record of ice cap fluctuations to a known chronology. These results have allowed us to test the hypothesis of a limited ice cap extent on the island, showing to our surprise that the former ice cap was extensive. Moreover, we have been able to reconstruct a significant advance of the ice cap during the Antarctic Cold Reversal, giving whole new insight into the dynamics of sub-polar Southern Ocean ice masses during a particularly poorly known period of Earth's history. The findings extend the cryospheric footprint of the ACR into the Atlantic Sector for the first time and reveal that the South Georgia ice cap was more sensitive to past climate forcing than previously implied. The study was published in Nature Communications on March 17th 2017.
- We are engaged in discussion with benthic biologists at the University of Southampton and BAS regarding the link between glacial geology and evolution of shelf fauna. Evidence for this includes attendance at a South Georgia Marine Protected Area workshop in May 2017. Future work combining and further testing the various models of shelf glaciation are in discussion.
- We have published a compilation of high-resolution multibeam bathymetry datasets from South Georgia's fjords, from which we have made new observations of the fjord glacial geomorphology and proposed a chronological model for the formation of fjord moraines that can go on to be tested further.
- We have published a review of sub-Antarctic glaciation in a leading Quaternary Science journal.
- We have contributed towards a German-led study of methane venting from South Georgia fjord-bottom sediments, supported by NERC funding to PI Graham.
- Project funding helped towards hosting a successful session on the glacial, climatic and geological evolution of South Georgia and the sub-Antarctic Southern Ocean at EGU 2014. PI Graham was lead convener.
- New international research networks have been established with the Alfred-Wegener Institute for Polar and Marine Research (AWI), in Bremerhaven, and researchers working on methane seepage from the South Georgia sea-floor at the MARUM, University of Bremen. PI Graham has been involved with two collaborative ship-time proposals to the German DFG, to continue to investigate the history of ice cap glaciation in the sub-Antarctic using seismic profiling techniques to look at the geological evolution of the South Georgia block in more detail.
- A PhD studentship started in October 2014 at the University of Nottingham (PI Graham is co-supervisor, with Prof. Melanie Leng), which is exploring oceanographic changes around South Georgia through the Holocene using the analysis of foraminiferal changes in sediment cores collected as part of the project.
- A MSc student, co-supervised by PI Graham, successfully defended his thesis at the University of Bremen. The thesis looked at Holocene climatic variability from core material and geophysical data obtained during this NERC project.
Exploitation Route - on completion of the project, data will be made publically-available in the South Georgia online GIS database, and will be of potential use to a variety of researchers from a range of disciplines
- geological history will be provided to biologists who are assessing the marine biodiversity of the South Georgia shelf (collaboration ongoing)
- we will open a dialogue with fisheries representatives at BAS who are keen to know how geology relates to fish stocks and abundance
- variety of further academic proposals and collaborations resulting directly from the study (German and UK led).
- we remain committed to supporting a PhD proposal which will focus on testing the sensitivity and behaviour of past ice caps on South Georgia using an ice-sheet numerical model.
Sectors Aerospace, Defence and Marine,Environment,Other

URL http://www.bbc.co.uk/news/science-environment-39303480
 
Description - Academic: New findings have been incorporated into the RAISED consortium; a community reconstruction of the extent and timing of the last glacial maximum and deglaciation of Antarctica. - Academic/Industry: Glacial geological results are being utilised by marine biologists studying the biodiversity of sea-floor habitats around South Georgia. I am in discussion with Oliver Hogg, a PhD student at NOCS/BAS, who will use mapped glacial features as part of new habitat mapping. The results may also be used by fisheries industry to assess the spatial production of fish stocks; I am in contact with fisheries representatives at the British Antarctic Survey. -Data dissemination: on publication of our latest results, mapping results will be made available through the South Georgia GIS. -Public award and lecture: I was awarded the British Antarctic Survey Laws Prize in 2013, and part of my South Georgia project was presented at the resulting public lecture. -Press: Widespread national and international press coverage of the paper published in Nature Communications (March 2017).
Sector Environment
Impact Types Policy & public services

 
Description Trans-Antarctic Association Awards
Amount £1,000 (GBP)
Organisation TransAntarctic Association 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2015 
End 07/2015
 
Description Alfred-Wegener Institute and MARUM partnerships 
Organisation Alfred-Wegener Institute for Polar and Marine Research
Country Germany 
Sector Public 
PI Contribution PI Graham has been co-writing proposals to the German DFG to fund ship-time to mount future field work to South Georgia; specifically, to look at the record of glacial advance and retreat from the buried seismic record. It is anticipated that success in the ship-time bids will lead to new grant proposals to UK research councils to apply for funds to carry out the scientific investigation.
Collaborator Contribution Academic collaboration.
Impact Outcomes: grant proposal Proposed work involves geologists, geophysicists, oceanographers, chemists, and biologists. Invitation to participate in scientific cruises on the RV Merian in 2017.
Start Year 2014
 
Description Durham University raised beach modelling 
Organisation Durham University
Department Department of Geography
Country United Kingdom 
Sector Academic/University 
PI Contribution I am working together with Prof. Mike Bentley and Dr. Natasha Barlow on the glacial history of South Georgia via shared results and discussion.
Collaborator Contribution Prof. Mike Bentley and Dr. Natasha Barlow are enhancing our understanding of South Georgia glacial history via shared results and discussion.
Impact Outcomes: convergence of ideas regarding scientific results.
Start Year 2015
 
Description BAS Laws Prize Lecture 2013 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Public lecture inspired questions from the audience and discussion with scientists outside of my discipline.

Promoted greater interest in geoscience work at sea and in South Georgia's icy history
Year(s) Of Engagement Activity 2013
 
Description Press release for Nature Communications paper and related media interest - March 2017 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Paper was the most read article on BBC Science News on the 19th March 2017. Full article still available here and reached a wide international readership: http://www.bbc.co.uk/news/science-environment-39303480
Year(s) Of Engagement Activity 2017
 
Description Talk for the Royal Geographical Society South West Region lecture series 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact X number of people attended the evening talk.
Year(s) Of Engagement Activity 2017
URL http://www.rgs.org/WhatsOn/In+your+region/South+West.htm