title: The early Miocene onset of a ventilated circulation regime in the Arctic Ocean.
abstract: 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 climate. 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 Ocean. 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 optimum, although it remains unclear if there is a causal relationship between these two events.
authors.affiliation: Department of Geology and Geochemistry, Stockholm University, SE-106 91 Stockholm, Sweden. martin.jakobsson@geo.su.se
authors.forename: Martin
authors.initials: M
authors.lastname: Jakobsson
authors.forename: Jan
authors.initials: J
authors.lastname: Backman
authors.forename: Bert
authors.initials: B
authors.lastname: Rudels
authors.forename: Jonas
authors.initials: J
authors.lastname: Nycander
authors.forename: Martin
authors.initials: M
authors.lastname: Frank
authors.forename: Larry
authors.initials: L
authors.lastname: Mayer
authors.forename: Wilfried
authors.initials: W
authors.lastname: Jokat
authors.forename: Francesca
authors.initials: F
authors.lastname: Sangiorgi
authors.forename: Matthew
authors.initials: M
authors.lastname: O'Regan
authors.forename: Henk
authors.initials: H
authors.lastname: Brinkhuis
authors.forename: John
authors.initials: J
authors.lastname: King
authors.forename: Kathryn
authors.initials: K
authors.lastname: Moran
mesh_terms: D001110:Arctic Regions; D001267:Atlantic Ocean; D017753:Ecosystem; D005618:Fresh Water / Q000032:analysis; D049690:History, Ancient; D010100:Oxygen / Q000032:analysis; D012623:Seawater / Q000032:analysis / Q000737:chemistry; D013997:Time Factors; D014872:Water Movements
chemical_list: D010100:Oxygen