On 15 April 1912, the RMS Titanic, en route westward from Southampton, England, to New York City, USA, hit an iceberg off the Grand Banks of Newfoundland and sank, killing more than 1500 people. The two halves of the wreck lie between the volcanic seamounts of the Southeast Newfoundland Ridge because there the southward-flowing surface waters of the cold Labrador Sea carry icebergs to their intersection with the warm tongue of the Gulf Stream. Today the Titanic is bathed by the Deep Western Boundary Current because these new abyssal waters pass at depth under the Gulf Stream on their circuit throughout the deep basins of the world oceans (Fig. F1). IODP Expedition 342 is designed to study the nature of this deep current system near its northern sources during the balmy climates of the Paleogene (65.5 to ~21.8 Ma).

During the early Paleogene, global temperatures were considerably warmer than today and supported forests rather than ice sheets in the high polar latitudes (Greenwood et al., 2010). The early Paleogene greenhouse world represents a radiative forcing state that we are rapidly re-approaching. At current and projected rates of fossil fuel consumption, atmospheric greenhouse gas concentrations are set to rise to Paleogene levels in the next 80 y (National Research Council, 2011). How did the climate and ecosystems of the Paleogene world work? What should we expect in the next century? Although the Eocene is not a perfect analogue to the near future (Haywood et al., 2011), understanding Eocene climate dynamics will provide information on what to expect from a warmer planet.

The primary objectives of our program are to obtain a depth transect of drill cores between ~5 and 2 km water depth. Because the ocean is layered, with different water masses formed in various parts of the planet arranged above one another, our depth transect of drill sites will permit a detailed reconstruction of the chemistry, circulation, and history of Greenhouse Earth. Furthermore, because we will target sediment drifts that accumulate faster than typical deep-sea sediments, we should also be able to reconstruct the history of a warm Earth with unusual fidelity. These two things—detailed assessment of the structure and circulation of the warm-world ocean and unusually detailed climate history—will help us test models of Earth’s climate and ecosystem evolution that have been difficult or impossible to resolve with typical deep-sea or land-based records of the Eocene.

Our drilling target is J Anomaly Ridge and Southeast Newfoundland Ridge offshore Canada’s Grand Banks. The drill sites, not far from the Titanic’s resting place, are positioned to monitor the strength and chemistry of deepwater formation in the Atlantic as well as outflows from the Arctic basins through Baffin Bay and the Norwegian seaway (Fig. F2). Today, both the northward-flowing Gulf Stream and the southward-flowing Deep Western Boundary Current cross over the drilling area, leaving a record of their flow strength, chemistry, and biology in the sediment drifts beneath them (Fig. F1). The shape of the North Atlantic margin suggests that a similar current configuration occurred in the past, with any deep waters formed in the North Atlantic constrained to flow over the Newfoundland ridges. Therefore, Expedition 342 sites will be particularly useful to monitor the overturning history of the North Atlantic Ocean.

The Newfoundland ridges are mantled with some of the oldest sediment drifts known in the deep sea and range in age from the Late Cretaceous to Paleogene. Pliocene–Pleistocene drifts in the northeastern Atlantic commonly have sedimentation rates of 4–20 cm/k.y. and therefore can be used to study rates of abrupt climate change (Channell et al., 2010). Previous drilling of drifts on Blake Nose (off the southeastern United States) revealed sedimentation rates in the middle Eocene of ~5–6 cm/k.y., far higher than the ~1 cm/k.y. rates typical of previous Paleogene-focused drilling targets (Norris et al., 2001b). If, as expected, the Newfoundland sediment drifts also have high accumulation rates, we will obtain records of warm-period climates and evolution with unusual fidelity, and these will be particularly useful for assessing rates of change in the Earth system during both transient episodes of extreme warming (analogous to the near future) and transitions form warm climates into the glaciated world.

Expedition 342 is focused on the Paleogene record on the Newfoundland ridges. Although there is an extensive Cretaceous record of both drifts and fossil reefs in the seismic record, we do not have time to do justice to Cretaceous objectives without sacrificing our studies of the Paleogene system. Furthermore, although we will likely obtain a record from the majority of the Paleogene, our particular area of focus will be the middle Eocene to Oligocene interval where thick sediment drift deposits preserve unusually expanded records of the transition from the greenhouse world of the Eocene climatic optimum to the glaciated world of the Oligocene. Therefore, our expedition has four major objectives:

  • First, we aim to reconstruct a detailed history of the carbonate saturation state of the North Atlantic through numerous episodes of abrupt global warming. An interval of particular focus will be the middle Eocene to early Oligocene record, where we expect to find expanded records of hyperthermal events and the middle Eocene climatic optimum. This history of the carbonate system, coupled with detailed geochemical studies, will allow us to test theories for the origin of “hyperthermals”—abrupt periods of greenhouse gas–fueled warming known to punctuate the Paleocene and Eocene (Galeotti et al., 2010; Quillévéré et al., 2008; Sexton et al., 2011). Natural experiments with global changes such as hyperthermals can enhance our understanding of the consequences of abrupt climate change for Earth’s ecosystems, climate, and chemistry. This record will be enhanced by our efforts to obtain the first depth transect that captures the truly deep ocean as well as the intermediate depths captured in previous drilling programs (Norris, Kroon, Klaus, et al., 1998; Bralower, Premoli Silva, Malone, et al., 2002; Lyle, Wilson, Janecek, et al., 2002; Erbacher, Mosher, Malone, et al., 2004; Zachos, Kroon, Blum, et al., 2004; Pälike, Lyle, Nishi, Raffi, Gamage, Klaus, and the Expedition 320/321 Scientists, 2010; Zachos et al., 2005).

  • Second, we aim to obtain a very detailed record of the flow history of the Deep Western Boundary Current issuing from the North Atlantic. Today, deepwater formation draws warm water into the Nordic seas, keeping them warm. Our work will show how far back this pattern of overturning circulation extends and its influence on climates of the past greenhouse world.

  • Third, we aim to obtain a detailed record of the Eocene–Oligocene transition (EOT; ~33.7 Ma) and the onset of major glaciation following the warm climates of the Eocene. Our drill cores through the EOT will not only provide a highly resolved record of the events leading up to and following the greenhouse-to-icehouse transition, but they are also well positioned to display how Greenland and the high northern latitudes responded to this event.

  • Fourth, we aim to address major uncertainties in the development of the geologic timescale by obtaining records of the Eocene that can be used to link the astronomical timescale developed for the last ~40 m.y. to the “floating” timescale of the early Paleogene developed over a series of IODP and earlier drilling expeditions.

This drilling proposal completes the North Atlantic objectives laid out in a 1997 Marine Aspects of Earth System History (MESH) workshop on warm period dynamics and the Ocean Drilling Program (ODP) “Extreme Climates” program planning group (PPG) (see​program_admin/​sas/​ppg.html). This proposal also addresses initiatives of the IODP Initial Science Plan in the areas of extreme climates and rapid climate change. Finally, our expedition takes up proposals of the recent National Research Council report Understanding Earth’s Deep Past: Lessons for Our Climate Future (National Research Council, 2011), which advocates focused efforts to resolve the timescale and use mechanisms of past hyperthermal events as possible analogues for future global change.