Evolution of Atlantic thermohaline circulation; early Oligocene onset of deep-water production in the North Atlantic

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doi: 10.1130/G22545.1
Author(s): Via, Rachael K.; Thomas, Deborah J.
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 34(6), p.441-444. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. With GSA Data Repository Item 2006087. 43 refs.; illus., incl. sketch maps
Summary: The flow of deep-water masses is a key component of heat transport in the modern climate system, yet the role of deep-ocean heat transport during periods of extreme warmth is poorly understood. The present mode of meridional overturning circulation is characterized by deep-water formation in both the North Atlantic and the Southern Ocean. However, a different mode of meridional overturning circulation operated during the extreme greenhouse warmth of the early Cenozoic, during which time the Southern Ocean was the dominant region of deep-water formation. The combination of general global cooling and tectonic evolution of the Atlantic basins over the past ∼55 m.y. ultimately led to the development of a mode of overturning circulation characterized by both Southern Ocean and North Atlantic deep-water sources. The change in deep-water circulation mode may, in turn, have affected global climate; however, unraveling the causes and consequences of this transition requires a better understanding of the timing of the transition. New Nd isotope data from the southeastern Atlantic Ocean indicate that the initial transition to a bipolar mode of deep-water circulation occurred in the early Oligocene, ca. 33 Ma. The likely cause of significant deep-water production in the North Atlantic was tectonic deepening of the sill separating the Greenland-Norwegian Sea from the North Atlantic.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Climate change; Cooling; Cores; Deep-sea environment; Deep-water environment; Geochemistry; Iceland-Faeroe Ridge; Isotope ratios; Isotopes; Leg 113; Leg 208; Lower Oligocene; Marine environment; Marine sediments; Metals; Mid-ocean ridges; Nd-144/Nd-143; Neodymium; North Atlantic; ODP Site 1262; ODP Site 1263; ODP Site 1264; ODP Site 689; Ocean Drilling Program; Ocean circulation; Oligocene; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleogene; Plate tectonics; Rare earths; Reconstruction; Sediments; South Atlantic; Southern Ocean; Stable isotopes; Tertiary; Thermohaline circulation; Walvis Ridge
Coordinates: S643101 S643100 E0030600 E0030559
S271100 S271100 E0013500 E0013400
S283200 S283200 E0024700 E0024700
S283200 S283200 E0025100 E0025100
Record ID: 2006051795
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