Dynamics of the Oligocene cryosphere: mid-to-high latitude climate variability and ice sheet stability

Lead Research Organisation: University of Southampton
Department Name: School of Ocean and Earth Science

Abstract

The sensitivity of global climate to increasing atmospheric carbon dioxide (CO2) levels is one of the biggest issues currently facing humanity. Quantifying the sensitivity of the Earth's climate system to changes in CO2 levels in the geologic past is one way of reducing the uncertainty in future climate predictions. If man-made (anthropogenic) CO2 emissions to the atmosphere follow projected rates, by 2100 concentrations will reach values not seen on Earth since the Oligocene epoch ~23 to 34 million years ago (Ma). Back then, geologists infer that Earth was warmer than today, featuring a genuinely green Greenland and a waxing and waning East Antarctic Ice Sheet (EAIS) that drove high amplitude sea level change (~40 m). These startling observations provide a powerful incentive to improve our understanding of the workings of that past climate system.

The focus of this proposal is on an important, but understudied, interval of time (~26 to 28 Ma) for which published palaeoclimate records indicate the biggest repeated (100 thousand-year time scale) changes in Antarctic ice volume and high-latitude temperatures of the entire Oligocene epoch. Our proposed study will generate geological data to both test this interpretation of Oligocene high-latitude climate instability and further elucidate the nature of ice-sheet and temperature variability. Validation of the existence of dynamic Antarctic ice sheets, however, would present a major scientific problem because numerical analysis of ice sheet behavior suggests that, in the absence of big changes in CO2 levels, a large Antarctic ice sheet should be stable once formed because of strong hysteresis properties associated with ice sheet geometry.

Several important questions are therefore raised:

1. How resilient were the early Antarctic ice sheets to CO2 change?
2. Do the numerical models give a false sense of the stability of both the Oligocene and, by extension, present day East Antarctic Ice Sheet?
3. Was Oligocene CO2 variability much greater than indicated in existing reconstructions?
4. Is it possible that ice sheets existed beyond Antarctica during the Oligocene?

The main factor that has limited progress in tackling these questions has been a lack of suitable sedimentary sections on which to work. We propose to exploit new deep-sea sediment archives recovered from the Antarctic and Newfoundland margins during Integrated Ocean Drilling Program Expeditions 318 and 342, respectively, on which our investigator team played significant roles (see Part 1, Case for Support). Our project will use (i) the Antarctic cores to test for the erosive products of dynamic behaviour (advance and retreat) on the East Antarctic margin, and (ii) the Newfoundland cores to test if high-latitude climatic conditions in the Northern Hemisphere were conducive to ice-sheet growth. Intriguingly, the drill cores from the Newfoundland margin contain abundant conspicuous angular sand sized lithic fragments that have been interpreted to be of ice-rafted origin-hinting at the presence of some form of nearby ice in the Oligocene. Our work will be accomplished through novel investigation of detrital isotope geochemistry on the Antarctic margin and application of organic geochemical temperature proxies in the high-latitude North Atlantic. Critical to our approach will be generation of high-resolution datasets that can be precisely dated and correlated to one another, as well as other high-resolution datasets around the globe.

Planned Impact

1. Who will benefit from this research?

This project will benefit the following specific users: Palaeoceanographers & Palaeoclimatologists; Climate and Cryosphere scientists; Earth System Scientists; the industrial hydrocarbon exploration sector of the UK economy; the wider community of scientists working on the problem of anthropogenic climate change; school children and the wider public interested in the exploration of the oceans and Earth.

2. How will they benefit from this research?

This project will make a significant scientific advancement towards understanding the stability of an interval in Earth's history when existing records suggest that Antarctic ice sheets underwent repeated large scale growth and retreat despite little apparent change in atmospheric carbon dioxide levels and the ice sheet stability predicted by numerical climate models. The records to be generated are from the Antarctic and Newfoundland margins in the Southern and North Atlantic Oceans, respectively, and will be of higher fidelity (time resolution) than those previously obtained for this interval. We will sample drillcores of sediments recovered from the deep ocean by Integrated Ocean Drilling Program Expeditions 318 (Bohaty, sedimentologist and van de Flierdt, inorganic geochemist) and 342 (Wilson, Co Chief Scientist). These sediments have unusually high rates of deposition and crucially, are well-suited, not only to record the terrestrial and marine imprint of high-latitude climate variability but also to the construction of these records with excellent age control (benthic stable isotope, palaeomagnetic and cyclostratigraphies). Improved knowledge of the stratigraphy of the Newfoundland sediment drifts and global glacial-interglacial cycles acquired during our project will also be used to improve the UK Industrial knowledge base that underpins techniques used to discover new petroleum reserves in deep-water settings.

3. What will be done to ensure that they benefit?

i) Our results will be made available for peer and public scrutiny by presentation in scientific meetings and publication in the
scientific literature.
ii) Follow-up dissemination to the wider public will be achieved in the first instance through media interviews to national and global news networks (eg., AP, Reuters); this is the most efficient channel for high impact and can ultimately result in spin-out feature articles (e.g., http://www.newscientist.com/issue/2661).
iii) Working with our Knowledge Exchange Officer, we will prepare summaries of important findings for press releases to new wires and postings on the University of Southampton and NOCS news websites (http://www.noc.soton.ac.uk/index.php).
iv) Rapid dissemination to the Earth System Science community during the course of the project will be achieved by presentations at international meetings and participation in workshops.
v) Meetings in Soton and Abingdon with Dr Andrew Davies (Neftex, UoS Ocean & Earth Sci departmental Stakeholder Advisory Board) to discuss the implications of our work for improving the knowledge base that underpins training in the key skill set used to discover new hydrocarbon reserves in deep-water settings.
vi) Our results will be incorporated into NOCS "Ocean & Earth" day activities used to enthuse young people in science and wider participation in Higher Education.
vii) We will leverage UK/NERC Impact from ANDRILL and IODP investment in high-profile science impact activities. For example, two dedicated scientific outreach professionals participated in IODP Exp 342 and Mr D. Brinkhuis produced and disseminated a series of 10 min-long video clips during the expedition and post-cruise plus a 20 min. documentary that debuted at Fall AGU 2012. Available online, these videos have already resulted in >27,750 viewings (25/6/13).

Publications

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Liebrand D (2018) Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean. in Paleoceanography and paleoclimatology

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Liebrand D (2017) Evolution of the early Antarctic ice ages. in Proceedings of the National Academy of Sciences of the United States of America

 
Description This project was focused on understanding the climate system during the early stages of the modern 'Icehouse' climate phase, which first developed during the Oligocene epoch following rapid global cooling and the onset of Antarctic glaciation at the Eocene-Oligocene Transition (34 million years ago). Our results point to a dynamic Antarctic ice-sheet that repeatedly advanced and retreated on orbital (20 to 400 thousand year) timescales. However, these oscillations in glacial activity are linked to carbonate dissolution cycles throughout the deep ocean basins, which complicate proxy climate records in deep-sea drillcores. We are working to further deconvolve the different signals, but we are able to identify a direct connection between high-latitude climate and ocean chemistry. Future work will seek to further assess the nature of short-term Antarctic ice-sheet variability through the Oligocene and repercussions for ocean temperature and global climate change.
Exploitation Route To inform policy on human-driven climate change.
Sectors Education,Environment

 
Description The results of this project highlight the sensitivity of the Antarctic ice sheets to climate change and contribute to the growing body of evidence of past dynamic ice sheet behaviour. This is something we've highlighted in our engagement efforts, and will continue to do so as we published additional findings resulting from the project.
First Year Of Impact 2017
Sector Education,Environment
Impact Types Societal,Policy & public services

 
Description NERC SPITFIRE DTP
Amount £60,000 (GBP)
Organisation University of Southampton 
Sector Academic/University
Country United Kingdom
Start 09/2016 
End 02/2019
 
Description International Ocean Discovery Program 
Organisation International Ocean Discovery Programme (IODP)
Country United States 
Sector Charity/Non Profit 
PI Contribution The International Ocean Discovery Program (and predecessor programs) is an international marine research collaboration that explores Earth's history and dynamics using ocean-going research platforms to recover data recorded in seafloor sediments and rocks and to monitor subseafloor environments. IODP depends on facilities funded by three platform providers with financial contributions from five additional partner agencies. Together, these entities represent 26 nations whose scientists are selected to staff IODP research expeditions conducted throughout the world's oceans. I have sailed on two IODP expeditions to the Antarctic region, and I am currently participating as a shore-based scientist in two recent expeditions. Analysis of drillcores retrieved on these expeditions forms the basis my ongoing NERC-funded research projects.
Collaborator Contribution My research is critically dependent on scientific drillcores recovered from deep-marine environment by IODP's drill ship, the JOIDES Resolution. Long drillcores retrieved using the JOIDES Resolution's riserless drill string technology are essential to developing the high-resolution palaeoceanographic records that are central to my research program.
Impact All outputs from my research team are made possible by this collaboration.
Start Year 2014
 
Description Postgraduate outreach efforts 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Research activities that are an offshoot of this funded project were highlighted by postgraduate students at the Univ. of Southampton who have participated in local science events in the city (e.g., 'Pint of Science').
Year(s) Of Engagement Activity 2016,2017,2018
 
Description University undergraduate recruitment 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact I highlighted some of the research supported by this grant in short presentation for undergraduate recruitment days at the University of Southampton.
Year(s) Of Engagement Activity 2017,2018