Ocean Temperature Changes Across the Eocene-Oligocene Boundary

Lead Research Organisation: University of Bristol
Department Name: Chemistry

Abstract

One of the major challenges in palaeoclimate research is understanding the transition from the ice-free, high carbon dioxide 'greenhouse world' of the Cretaceous and Paleogene to the colder, low carbon dioxide 'icehouse world' in which we live today. During this long-term climate evolution, one of the most dramatic events was the relatively rapid growth of permanent ice sheets on the Antarctic continent and co-occurring drop in sea level about 34 million years ago (the Eocene-Oligocene, or E-O, boundary). It is thought that this event was caused by a decrease in atmospheric carbon dioxide levels and/or a change in ocean circulation. Obviously, a crucial piece of data is a high-resolution record of ocean temperatures during this transition; to achieve this, we will develop geochemical records in sediments from ODP Site 1218 in the equatorial Pacific. However, our ability to interpret such records from Site 1218 / and comparable sites / is limited by a number of factors. The classical approach for obtaining sea surface temperature records is by analysing the oxygen isotopic composition in the calcium carbonate shells of foraminifera living in the surface waters of the ocean. Unfortunately, it is becoming clear that such records are typically compromised, because the foraminifera shells dissolve and recrystallise in the deep part of the ocean, effectively erasing the original temperature signal. Bottom water temperature records, based on oxygen isotopes in benthic foraminifera, are more reliable; these records, however, are hard to interpret because the oxygen isotopes are affected by both temperature and global ice volume / which obviously changed dramatically across the E-O boundary. Thus, to obtain high resolution ocean temperature records requires the application of new approaches. One of these tools is based on the composition of cellular fats in marine microorganisms / the TEX86 proxy. The rings in these compounds are related to the structure of the organism's cell membrane, such that the number of rings increases with the temperature of the growth environment. Because this proxy is based on organic compounds, it is not susceptible to the same dissolution concerns that affect proxies based on calcium carbonate shells. To obtain bottom water temperatures we will measure the amount of magnesium that has partitioned into the benthic foraminiferal calcium carbonate shells (Mg/Ca ratios). Mg/Ca ratios are not affected by ice volume and have been used to develop long-term records of deep ocean cooling; but they are also affected by the distribution of carbonate species in the ocean and that appeared to change dramatically at the E-O boundary as well. Therefore, we will measure both the Mg/Ca ratios and B/Ca ratios, which reflect carbonate ion distributions; together they can be used to decipher both the temperature and alkalinity change in the deep ocean. These two approaches will be applied in parallel for twenty-five samples spanning the E-O boundary. This will allow us to determine exactly how much the deep and shallow Equatorial Pacific cooled across this major climate event. It will also allow us to determine if there were any negative feedbacks in the system; for example, did the build up of ice sheets slow down erosion and allow carbon dioxide concentrations to build up again? Finally, by comparing deep and shallow ocean cooling, we will be able to evaluate models of ocean circulation change.

Publications

10 25 50
 
Title Bristol Green Capital Arts Programme 
Description The 2015 Green Capital Arts Programme comprised dozens of events, exhibits and neighbourhood arts projects. 
Type Of Art Artistic/Creative Exhibition 
Year Produced 2015 
Impact I made numerous contributions, all informed by past climate research funded by the NERC (and others), including: 1) Writing the introduction to the programme brochure 2) Partnering with the Festival of Ideas to deliver the Coleridge Lectures and other talks 3) Co-curating the Fog Bridge Exhibit (Fujiko Nakaya) as part of the In Between Time Festival 4) Helped to develop a programme around climate change, past and present, as part of the Withdrawn installation in Leigh Woods (Luke Jerrams) in partnership with the National Trust 
URL https://www.bristol2015.co.uk/
 
Title The Uncertain World by Alex Lucas 
Description The Uncertain World was commissioned by me and done by local street artist Alex Lucas. It is a series of drawings of modern-day Bristol, inundated by prehistoric levels of flooding and populated by Cretaceous sea creatures; the goal was to show how past climate can be used to explore and constrain uncertainty. Numerous postcards were distributed and some images were sold in Alex Lucas's shop. A major mural was painted on a University owned building that abuts one of Bristol's busiest roads. 
Type Of Art Artwork 
Year Produced 2015 
Impact The art has been used in numerous publications, including in various Bristol Green Capital programmes (Future Leaders Summit Programme and Arts Programme). It will also be used in an upcoming commentary in Nature Geoscience. The mural was featured in online video Magazine Made in Bristol and 24/7 Magazine (note link below is brief; main articles have now been removed) 
URL http://www.bristol247.com/channel/culture/art/street-art/plesiosaurs-on-park-row
 
Description Confirmation of major global sea surface temperature change across the Eocene-Oligocene boundary
Exploitation Route Developing collaborations with renewable energy sector: Our results highlight the important role of atmospheric carbon dioxide as a climate driver, emphasising the need to move to a carbon neutral economy. Approaches developed here are currently being applied to other programmes (e.g. Descent Into the Icehouse)
Sectors Environment

 
Description This was a small grant and the focus was to survey IODP Sites for opportunities in biomarker characterisation of past climate change. The sites examined were deemed inappropriate for reconstruction of past temperature or carbon dioxide characterisation but could be revisited by different types of investigations (i.e. reconstruction of hydrological change).
First Year Of Impact 2012
Sector Environment
Impact Types Societal

 
Description Collaboration with Bristol City Council and Resilience Group 
Organisation Bristol City Council
Country United Kingdom 
Sector Public 
PI Contribution I have collaborated with Bristol City Council in a) publicity for the Green Capital; b) attendance at COP21, representing the UK and Bristol; and c) serving on various strategic groups including the city's Resilience Sounding Board.
Collaborator Contribution They have helped raise the profile of the research (i.e. attendance at COP21) and helped identify priority areas.
Impact Many of the talks, events and blogs are related to this activity and noted where appropriate.
Start Year 2014
 
Description 2017 Public Talks and Arts Exhibits 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact RDP continues to engage the public, with 5 new events/workshops/talks during 2017. These were mainly in the Bristol region.
Year(s) Of Engagement Activity 2017
 
Description Ancient 'dead seas' offer a stark warning for our own near future - Blog on The Conversation 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Blog read by over 7300
Year(s) Of Engagement Activity 2016
URL https://theconversation.com/ancient-dead-seas-offer-a-stark-warning-for-our-own-near-future-47984
 
Description Living in the Futures Past 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact During 2015-2016, Pancost was interviewed by Susan Kucera on past and future climate change. Those conversations - as well as others - were compiled into the film Living in Futures Past, released at film festivals in early 2018. The film was produced by and stars Jeff Bridges. Info available at: http://www.imdb.com/title/tt7683148/ and http://reneelertzman.com/appearance/living-in-the-futures-past/
Year(s) Of Engagement Activity 2018
URL http://www.imdb.com/title/tt7683148/
 
Description Public talks 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Deriving from our palaeoclimate research, we have given over 50 talks, science cafes, debates in various venues (mostly but not exclusively local to Bristol). Collectively, these have reached over 5000 people. In many cases, these were discussions/debates with important figures, including Mayor of Bristol George Ferguson, the Bristol Youth Mayors, members of Bristol City Council, our MPs and MEPs.

Much discussion with public, further talks and film screenings arranged, talks blogged about.
Year(s) Of Engagement Activity 2011,2012,2013,2014,2015
URL http://transitionclevedon.wordpress.com/2013/03/14/notes-from-tuesdays-talk-on-climate-change-dr-mar...