"South Pacific Paleogene Climate" IODP Expedition 378: Stratigraphy, Chronology and Provenance of late Eocene-early Oligocene South Pacific sediments

Over the last 66 million years, Earth's climate has changed from a near ice-free "Greenhouse" world to an "Icehouse" world, where large ice sheets cover huge areas of land in both the northern and southern hemispheres. Although some of this change has been gradual, the first time Antarctica was covered with a large ice sheet occurred approximately 33.9 Million years ago. This transition is referred to as the Eocene-Oligocene Transition.

A large drop in atmospheric carbon dioxide concentrations has been proposed as the main cause of the first major Antarctic glaciation. However, another key condition for ice sheets forming on Antarctica is that this continent needed to be thermally isolated from warm waters that spread from the Earth's equator. In the present day, a large, cold deep-water current circles Antarctica, thereby providing a temperature barrier. This current is called the Antarctic Circumpolar Current, and some research suggests that the first Antarctic glaciation occurred when this deep-water current first started. However, this claim is debated. It is currently difficult to solve this debate as there are insufficient records that can trace the start of the Antarctic Circumpolar Current accurately.

Scientific ocean drilling programmes like the International Ocean Discovery Program (IODP) and its predecessors are the only way to recover the archives of past climate change locked away in deep-sea sediments stored on our ocean floor. The south Pacific Ocean is a key area that is dominated by the Antarctic Circumpolar Current, however, it remains entirely unexplored by scientific ocean drilling. This will change with IODP Expedition 378, which will go to the South Pacific and recover key sediments and enable us to look back at climate dynamics when large ice sheets first formed on Antarctica.

Here, we propose to use these sediments to investigate when the Antarctic Circumpolar Current first appeared in the South Pacific by looking at the chemistry and mineralogy of the past sediments across the Eocene-Oligocene Transition. We will also make an initial assessment of how the ice volume changed over longer timescales during the same time interval, using the chemistry of microscopic fossils that live on the ocean floor, called benthic foraminifera. Combining these preliminary ice volume records with the chemistry and mineralogy records should improve our understanding of the role of the Antarctic Circumpolar Current in the first major glaciation of Antarctica.

Anthropogenic climate change is now regularly in the public consciousness, especially with grassroots movements like the Extinction Rebellion and the Global Climate Strike pushing our governing bodies to be more proactive on taking action. Past climate variability of the southernmost Pacific Ocean remains relatively poorly understood, especially with respect to the role of changing deep-water circulation in driving Antarctic glaciation. This project will help improve our knowledge of this region's past climate, and should better constrain the onset of the cold, circumpolar deep-water circulation around Antarctica.

We expect the results of our proposed research to benefit a wide range of users and communities, including, specialist UK and international Earth sciences, palaeoclimate and ocean drilling communities, national and international policy-making bodies and the general public. To reach as wide a group as possible, we plan a combination of dissemination, communication and outreach activities targeted at different audiences.

IODP Exp. 378 research will fundamentally improve our understanding of how global circulation drove and responded to Antarctic glaciation. The proposed research will especially provide useful insights to policymakers about how future scenarios driven by anthropogenic climate change may affect Earth's global thermohaline circulation patterns, and how this may affect climate in other regions through complex teleconnections. The research findings will be presented as open access publications in appropriate high-impact journals, and all data will be uploaded to open access databases. In collaboration with the UCL Public Engagement Office, publication announcements will be promoted through press releases, as well as on social media, professional and academic platforms to optimise the impact and visibility of publications. These actions will ensure the results are disseminated to the wider scientific community, as well as the general public and policy makers.

We also expect interest in IODP Exp. 378 by the general public because of the exploration-driven nature of the expedition. The south Pacific Ocean remains a remote and inaccessible region about which little is known. We will communicate what our findings reveal about this enigmatic region through a number of outreach events specifically targeting the general public. IODP Expedition 378 is sailing with three specialist outreach officers originating from three different continents (see http://iodp.tamu.edu/scienceops/precruise/southpacific/participants.html). By collaborating with these outreach specialists whilst on the ship to produce blogs, videos and live streams, we expect to reach a globally distributed audience. We also plan a number of postcruise outreach events building upon the shipboard materials. This will include incorporating IODP Exp. 378 science into a public open access lecture at the UCL Science Centre, school visits through the Geobus and the participation in a European Researchers' Night, most likely hosted as a 'Science Uncovered Night' at the Natural History Museum in London.