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The early Miocene onset of a ventilated circulation regime in the Arctic Ocean


Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate1. Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic’s deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean2. Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated (‘ventilated’) conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor ‘lake stage’, to a transitional ‘estuarine sea’ phase with variable ventilation, and finally to the fully ventilated ‘ocean’ phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum3, although it remains unclear if there is a causal relationship between these two events.

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Figure 1: Schematic map of the present ocean circulation in the Arctic Ocean.
Figure 2: Correlation between a synthetic seismogram representing the stratigraphy of the ACEX sites and seismic reflection profile AWI-91090, and the ACEX age model.
Figure 3: Palaeo-geographic/palaeo-bathymetric reconstruction for the late early Miocene.
Figure 4: A schematic illustration of the Fram Strait opening and hypothetical water exchange development between the Arctic Ocean and North Atlantic.


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Financial support was received from Stockholm University, the Swedish Research Council (VR), the Swedish Royal Academy of Sciences through a grant financed by the Knut and Alice Wallenberg Foundation, and the Netherlands Organization for Scientific Research (NWO). The ACEX expedition was carried out by the Integrated Ocean Drilling Program (IODP). We thank the IODP European Science Operator (ESO), the Swedish Polar Research Secretariat as well the ship fleet management, captains and crews of the icebreakers Oden, Vidar Viking and Sovetskiy Soyus. N. Welters is thanked for sample processing. Comments and suggestions from M. Siddall are acknowledged. This is a contribution from the Stockholm University Climate Research Centre (SUCLIM).

Author Contributions M.J. and J.B. initiated the paper. M.J. compiled the palaeo-bathymetric reconstruction, performed the core-seismic integration and took part in the development of the oceanographic analysis, which was led by B.R. and J.N. The age model was developed by J.B., M.F provided 10Be data, H.B and F.S. provided micropalaeontological information, and J.K provided palaeointensity data. W.J. compiled the age-width estimation for the Fram Strait from geophysical data. All authors discussed the results and provided input to the manuscript during its development.

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Correspondence to Martin Jakobsson.

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Jakobsson, M., Backman, J., Rudels, B. et al. The early Miocene onset of a ventilated circulation regime in the Arctic Ocean. Nature 447, 986–990 (2007).

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