Bridging the Timing Gap: Connecting Late Pleistocene Southern Ocean and Antarctic Climate Records

In light of current concerns over greenhouse-gas emissions and related temperature rise it is important to understand the mechanisms operating in the global climate system. This understanding may allow us to anticipate human-induced climate change and related ecosystem vulnerability. The Southern Ocean plays a central role in defining Earth's climate because it is a location where cold deep waters rise to the surface and exchange gases and heat with the atmosphere. One of the most important gases for the climate system is carbon dioxide (CO2). Since the oceans contain about 60 times more carbon than the atmosphere, it only takes a small perturbation in the ocean to have a large climate impact. Atmospheric CO2 levels have shown systematic changes over the past 800,000 years as revealed by gasses trapped in ice cores, and recent evidence has come to light that shows that CO2 can increase rapidly over only hundreds of years. We still do not know how and why these changes in CO2 occur but their size and speed suggests that they must have been driven by changes in the deep ocean.

Mechanisms that have been put forward to explain lower atmospheric CO2 concentrations during past cold (glacial) periods focus on increased CO2 uptake in the Southern Ocean. This could have been achieved by a combination of increased sea ice cover and a more layered structure in the water column, which prevents CO2 from escaping to the atmosphere. The concept is supported by modelling evidence and predicts that we should find old, carbon-rich waters in the deep Southern Ocean during past cold times. If this layered water structure was removed, then these deep waters would release CO2 to the atmosphere as ice ages came to a close. Records from ice cores show us that the actual rise of CO2 during the end of the last ice age ('last deglaciation') happened in multiple steps. So far, however, it has been very difficult to obtain records from the Southern Ocean to test the hypothesis posed above, or the alternative hypothesis that carbon sequestration in the South was achieved due to more active CO2 uptake by planktonic marine plants. What we have been lacking is a suitable recorder ('archive') of past environmental conditions directly in the Southern Ocean that can resolve time increments of about 100 years or less, similar to in the record preserved in ice cores.

With our project we aim to transform understanding of the Southern Ocean's role in climate change by creating detailed records of the circulation, temperature, and CO2 chemistry of the Southern Ocean at the end of the last ice age and into the current warm period (past 25,000 years) at unprecedented temporal resolution. To achieve this we will make geochemical measurements on the skeletons of fossil deep-sea corals, a novel archive that allows us to create unique coupled records of past oceanographic change on a precise and accurate timescale. The skeletons of deep-sea corals are formed using the chemical ingredients of the seawater that they live in. This means that during the lifetime of a coral (~100 years) a record of water mass composition and temperature is captured as they grow. By performing a suite of geochemical measurements on each fossil coral, we can reconstruct environmental conditions at the time it grew. Repeating this exercise for hundreds of corals will allow us to construct the first directly dated record of the Southern Ocean's behaviour since the last ice age. Our new record will allow comparison of the relative timing of environmental changes in the Southern Ocean with those of ice core records. It will therefore address one of the most hotly debated questions in global climate change research, the origin of changes in atmospheric CO2 and temperature on time scales of hundreds to thousands of years.

Beyond the scientific community, we have identified six end-user groups.


a) Secondary school students and teachers - a new workshop on the ocean's role in climate change delivered to schools through GeoBus: GeoBus is a highly successful educational outreach program developed and run by the Department of Earth & Environmental Sciences at the University of St Andrews. Climate-focused workshops are of particular interest to teachers and students, given the presence of climate science (and skeptics) in the media and news. We propose to deliver a workshop for secondary schools on climate change to be taught in Chemistry and Physics class slots, which will engage pupils in STEM subjects.


b) Policy makers - improved understanding of a key region for global climate that will help inform the IPCC: Over the last 10 years the Intergovernmental Panel on Climate Change (IPCC) has developed an increasing emphasis on the role of palaeoclimate to inform policymakers on how the climate system can operate. Our work will inform the next IPCC report thereby have a lasting benefit to a wide community of policy forming bodies, who require improved projections of the path of atmospheric CO2 rise and associated climate change, ocean acidification, and ecosystem change. The investigators of this proposal will furthermore commit to visiting each of their local MPs to establish a link for these decision makers to climate science.


c) General Public - Project Website and Public Lectures and Events: Significant action on climate change is likely only to be achieved with a groundswell of public understanding and concern. Our project provides an excellent teaching opportunity for public engagement with CO2 rise and associated climate change. This effort will be linked with existing and new outreach websites. We will also publicize our research through Facebook and Twitter, providing links to the website and our latest talks, press releases, and papers. We will continue to partake outreach events including 'Pint of Science', and Nature Live talks at the Natural History Museum.


d) Undergraduates: We will engage undergraduate students directly in the project by enabling hands-on laboratory expertise, a passion for scientific endeavour, and a deep knowledge of the research field. Summer projects and final year projects provide a great opportunity for advisors and students to integrate education and research beyond the classroom, advance discovery and understanding, while providing training on solving scientific problems and laboratory skills. Major findings will also be posted on the Departmental Facebook pages allowing the wider undergraduate community to maintain awareness of cutting-edge research activities that are happening in their building.


e) Training and mentoring of PDRAs: This project will enhance the career development of two named PDRAs (Wilson and Chen) as well as benefit the onward career of recently hired Faculty member and co-I Rae. PI LR and Co-I TvdF both have excellent track records in actively training and advising postdoctoral scholars. They will also help Rae to develop effective mentoring skills throughout the course of this project.


f) Increasing Women in STEM: The proposal supports two mid-career female investigators who will provide mentorship and role models for junior women in STEM subjects. We will include sections on our websites that touch on how women provide leadership in STEM subjects, from being Chief Scientist on a research cruise, to leading research teams as well as the paths we took to get here. Efforts will be made to include female undergraduates in the project through direct internships and through outreach presentations. Impact will be assessed by website traffic and event attendance.