Changes of the North Atlantic deep circulation at the Eirik Drift since the Pliocene

Author(s): Müller-Michaelis, A.; Uenzelmann-Neben, G.
Author Affiliation(s): Primary:
Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The global climate and its changes are coupled to the ocean circulation. The surface ocean stores and transports heat and freshwater, interacts with the overlying atmosphere and thereby impacts the climate. The global Thermohaline circulation (THC) is described as a conveyor belt for heat and freshwater within the world's oceans. Deep-water formation in high latitudes is the driving mechanism of the THC. It connects the surface circulation with the reversed deep circulation. The Eirik Drift, located offshore southern Greenland, lies closely downstream of the deep-water formation regions of the Nordic Seas and is built under the influence of the deep branch of the North Atlantic THC. The sedimentary packages and structures of the Eirik Drift therefore bear information about strength and direction of the North Atlantic deep-water circulation in a changing climate. High-resolution seismic reflection data collected during RV Maria S. Merian cruise MSM12/2 in 2009 were incorporated with geological information from ODP Leg 105 Site 646 and IODP Expedition 303 Sites 1305-1307 and led to a seismostratigraphic analysis of the sedimentary structure of the Eirik Drift. For the Pliocene Epoch we observed an intensification of the deep circulation at the Eirik Drift along with the climate reversal to the early Pliocene warm period (≈5.6 Ma, horizon R2). The maximum intensity of the deep circulation at the Eirik Drift is documented in an erosional unconformity at ≈4.5 Ma. The deep circulation at the Eirik Drift remained strong during the transition to Pliocene cooling (≈3.2 Ma) until ≈2.5 Ma (horizon R1), when the onset of ice rafting documents the intensification of Northern Hemisphere glaciation. During the series of glaciations of the Pleistocene Epoch a shallowing and weakening of the deep current system at the Eirik Drift was observed. The observation of intensification of the deep circulation during warm climate conditions and weakening during cold climate phases is in conflict to our expectations. We suggest in our interpretation a southward shift of the deep-water formation region along with a shift of the deep current system during cold climate with enhanced ice extent. This implies that the main North Atlantic deep circulation just affected the Eirik Drift during warm phases and that during cool phases solely weak branches of the deep circulation system overflowed the Eirik Drift.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Eirik Drift; Expedition 303; Expeditions 303/306; IODP Site U1305; IODP Site U1306; IODP Site U1307; Integrated Ocean Drilling Program; Labrador Sea; Leg 105; Neogene; North Atlantic; Northwest Atlantic; ODP Site 646; Ocean Drilling Program; Ocean circulation; Pliocene; Quaternary; Tertiary
Coordinates: N581400 N581400 W0453800 W0453900
N572800 N572900 W0483200 W0483200
N581236 N581236 W0482206 W0482206
Record ID: 2014062118
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