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

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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.