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.

An integrated geophysical study of Vestbakken Volcanic Province, western Barents Sea continental margin, and adjacent oceanic crust

“…This change resulted in opening of the Fram Strait (Fig. 1) and a deepwater connection to the Arctic Ocean basin in Early Miocene Jakobsson et al 2007). The extensional component also detached two continental slivers from the western Barents margin: the East Greenland Ridge (Døssing et al 2008) and the Hovgård Ridge (Myhre et al 1982) (Fig.…”

Batiacasphaera bergenensis and Lavradosphaera elongata — New dinoflagellate cyst and acritarch species from the Miocene of the Iceland Sea (ODP Hole 907A)

“…B. bergenensis sp. nov. occurred shortly after the Middle Miocene Climate Transition (MMCT, 14.2-13.7 Ma), during which cooler arctic surface waters likely reached the Iceland Plateau due to the establishment of a protoEast Greenland Current and a ice drift pattern across the Fram Strait similar to today (Jakobsson et al, 2007;Knies and Gaina, 2008;. It exhibits low abundance (c. 0.3% of the total dinocyst assemblage) in the lowermost Serravallian, but a significant acme (47%) occurs at~13.39 Ma.…”

Response of marine palynomorphs to Neogene climate cooling in the Iceland Sea (ODP Hole 907A)

“…The cooler surface waters in the Iceland Sea than in the Norwegian Sea may be attributed to enhanced exchange of water masses with the Arctic Ocean and the Nordic Seas since~14 Ma (Jakobsson et al, 2007). As the Transpolar Drift has been active in the past 15 Ma (Haley et al, 2008), the opening of the Fram Strait led to the establishment of a modern-like ice drift pattern with export from the Arctic Ocean into the western Nordic Seas (Fig.…”

“…The opening of Fram Strait and the subsidence of the Greenland-Scotland Ridge (GSR) have led to an enhanced exchange of water masses between the Arctic Ocean and the North Atlantic via the Nordic Seas (Bohrmann et al, 1990;Wright and Miller, 1996;Poore et al, 2006;Jakobsson et al, 2007;Knies and Gaina, 2008). Jakobsson et al (2007) assumed that Fram Strait reached sufficient width (40-50 km; present-day width 400 km) to efficiently ventilate the Arctic Ocean at~17. 5 Ma,and began to open at greater depth by~14 Ma, which is supported by benthic foraminiferal evidence from the Lomonosov Ridge and Fram Strait (Kaminski et al, 2006;Kaminski, 2007).…”