Climate change across the Eocene/Oligocene and Oligocene/Miocene transitions: IODP Expedition 342, Newfoundland sediment drifts

Carbon dioxide, CO2, is a powerful greenhouse gas and its concentration in Earth's atmosphere has increased by around 35% since the start of the Industrial Revolution (in ca. 250 yrs) to a level that is higher than at any time in the past 800 thousand years as measured in air bubbles obtained from ice cores. If man-made (anthropogenic) CO2 emissions to the atmosphere follow projected rates, then by 2100, concentrations will reach values not seen since the Palaeogene epoch (ca. 65-23 million years ago, Ma) when Earth's climate was much warmer than today, featuring, for example, a genuinely green Greenland. These startling observations provide a powerful incentive to improve our understanding of the workings of the Palaeogene climate system.

The Cenozoic palaeoclimate record is largely pieced together from the analysis of deep-sea sediments. It reveals a long-term climatic deterioration since the early Eocene (~55 Ma) with superimposed higher-frequency (10 to 100 thousand year timescale) variations including those paced by changes in Earth's orbit of the Sun and more extreme changes, both transient excursions and more persistent shifts in climate-state. In each case, the palaeoclimate archive indicates a close relationship between the climate signal observed and perturbation to the global carbon cycle.

To decipher the physical and biogeochemical mechanisms that forced these changes in climate and the responses (feedback effects) we must determine rates and full magnitude of the changes involved. Until now this has proved difficult because virtually all of our records of pre-Plio-Pleistocene climate change come from sites where sediments accumulate very slowly (~ 1 cm per thousand years). Integrated Ocean Drilling Program Expedition, IODP Exp., 342 addresses this problem directly by having drilled a series of holes at sites where deep-sea sediments have accumulated at unusually fast rates (up to 10 cm per thousand years) in sediment drifts that were swept and piled up under the influence flow path of the Deep Western Boundary Current on J Anomaly Ridge and Southeast Newfoundland Ridge. The drill site area is famous because it is the graveyard of RMS Titanic, which sank after colliding with an iceberg en route from Southampton, England, to New York City, USA, in April 1912 and of the Andrea Gail, the commercial swordfish vessel from Gloucester, Massachusetts, lost at sea with all hands during the "Perfect Storm" of October 1991. These sediments drilled provide an archive of changes in chemistry, flow history, and depth structure of waters exiting the Nordic seas and Arctic Ocean during the transition into a world with major ice caps in both hemispheres from an ice-free world featuring a genuinely green Greenland and lush forests on Antarctica.

The proposed project will generate new high-resolution records of core-scanning X-ray fluorescence (XRF) and targeted oxygen and carbon isotopes of bulk CaCO3 in Exp. 342 drill cores: (i) To produce high quality chronologies and correlations among the expedition sites and ties to existing records from sites elsewhere where sedimentation rates are slower. (ii) To evaluate the climatic significance of these cyclostratigraphic records and lay the groundwork for a full quantitative geochemical analysis of the changes in ocean temperature, ice volume and CO2 levels involved.

1. Who will benefit from this research?

This project will benefit the following specific users: Palaeoceanographers & Palaeoclimatologists; Marine Geologists; Ocean & Climate scientists; Earth System Scientists; 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 the most recent interval in Earth's history when CO2 levels in the atmosphere are thought to have been close to the levels projected for the year 2100. The records to be generated will be of much higher temporal resolution than those previously obtained for this interval (we have drilled into sea floor sediments with unusually high rates of deposition) and thereby make fundamental advances for those seeking to understand climate sensitivity (to CO2 forcing), ocean acidity and circulation changes associated with perturbations in the global carbon cycle and the stability of early ice sheets. Knowledge of the stratigraphy of the Newfoundland sediment drifts acquired during Expedition 342 will inform plans to return to the Nerwfoundland sediment drifts and acquire comparative records for other intervals of geologic time.

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

A number of activities will be undertaken. We will engage with the communities of Palaeoceanographers & Palaeoclimatologists, Marine Geologists, Ocean, Climate and Earth System scientists through attendance at conferences, participation in workshops (eg. the Santa Cruz Cenozoic CCD meeting scheduled for Dec 2012) at no cost to this proposal. Liebrand and the PI and will feature the scientific results of this project and the broad Exp. 342 context in invited talks and seminars at institutions around the world. The multidisciplinary nature of the science involved will naturally ensure that value is added through interaction with a broad scientific community.

To ensure maximum effectiveness of the scientific results of the proposed study we will also: share information quickly (e.g. via google spreadsheets) with other members of the science party during the moratorium period; communicate openly with collaborators within and without the science party; publish results in a timely manner in the peer reviewed literature; initiate new studies and seek new collaborations where valued; participate in Ocean & Earth Day at the National Oceanography Centre Southampton (March 2013); communicate major scientific findings to the media.

In terms of media communication, IODP Exp 342 benefits from the involvement of two dedicated scientific outreach professionals. At the onset of the expedition the Exp 342 trailer video, viewable at http://youtu.be/QraUO3db6fk, had been viewed >1400 times and the expedition listed >3000 followers via social media (see, www.joidesresolution.org for details). Six further 10 min-long video documentaries were produced shipboard and disseminated during the expedition and have already resulted in >10,000 viewings and a further video is planned for the post-cruise sampling party. Thereafter, a full length documentary will be produced from all footage. Further exposure has been achieved via web media features see http://boingboing.net/2012/09/05/at-sea-for-science.html