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

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.

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).