New climate archives from the high latitude North Atlantic Ocean: Preliminary results from IODP Exp 342, Newfoundland sediment drifts

Abstract:

The geologic record holds a rich history of abrupt ecological and climate change events but our understanding of the ocean-atmosphere dynamics involved is not well developed, particularly for high CO₂ warm climate states of the pre-Quaternary because the deep-sea records available typically come from low sedimentation rate (of 1-2 cm/kyr) sites that do not permit studies on times scales similar to or shorter than the ~1500 year mixing time of the ocean.

The principle objective of IODP Expedition 342 (drilled summer, 2012) was to target sediment drifts off Newfoundland with unusually high rates of sedimentation in order to investigate, for the first time, the stability of the Cenozoic greenhouse and icehouse climate states on sub-orbital timescales. The sedimentary sequences drilled accumulated directly under the flow path of the Deep Western Boundary Current and are well-situated to provide an archive of changes in chemistry, flow history, and depth structure of waters exiting the Nordic seas and Arctic Ocean during the transition from ice-free peak Cenozoic warmth in the early Eocene to the onset of Arctic sea ice formation and the growth of major ice sheets on Antarctica. The sediment drift deposits drilled are characterized by high sedimentation rates and clay-rich lithologies hosting spectacularly well-preserved calcareous microfossils (benthic and planktic) and sand-sized lithic fragments. These remarkable archives present an exciting opportunity to address some long-standing questions of relevance to this session. For example: (1) How stable was the Eocene greenhouse climate state? (2) Is large amplitude suborbital variability in Earth’s climate restricted to the late Pleistocene? (3) When and why did Earth shift to its present climate state with large ice sheets in both hemispheres? (4) How valid are suggestions of Eocene bipolar glaciation? (5) How and why did the carbonate chemistry (CCD) and circulation of the North Atlantic Ocean change in association with these shifts in global climate?