Changes in equatorial Atlantic Ocean thermohaline circulation across the mid-Pleistocene transition

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Author(s): Yehudai, Maayan; Kim, Joohee; Seguí, Maria Jaume; Goldstein, Steven L.; Pena, Leopoldo D.; Haynes, Laura; Hoenisch, Baerbel; Farmer, Jesse R.; Ford, Heather L.; Raymo, Maureen E.; Bickert, Torsten
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Columbia University of New York, United States
University of Bremen, Germany
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Mid-Pleistocene Transition (MPT) marked a change in the duration of glacial-interglacial cycles from ∼41 to ∼100kyr between ∼1.3-0.7 Ma. A recent study (Pena and Goldstein, Science, 2014) from the Southern Atlantic Ocean found evidence for major disruptions in the global thermohaline circulation (THC) between MIS 25-21 (∼950-850 ka), which may have triggered intensified glacial periods and the onset of the 100 kyr cycles. We report new Nd isotope data on Fe-Mn oxide encrusted foraminifera and fish debris from ODP Site 926 (3.719N,42.908W, 3598 m) between ∼1.2-0.4 Ma, in order to evaluate changes in the THC in the equatorial Atlantic, through comparison with North and South Atlantic sites. The ODP 926 εNd values fall in-between those in the North Atlantic (DSDP 607) and South Atlantic (ODP 1088 and 1090) throughout the studied interval, consistent with mixing between northern and southern end-members, and supporting the interpretation that the data represent the THC signal at this site. Pre-MPT data show smaller glacial-interglacial differences compared to the greater post-MPT glacial-interglacial variability. As Pena and Goldstein (2014) observed in the South Atlantic, during MIS 23 at ∼900 ka, εNd values do not shift significantly toward North Atlantic more negative values, consistent with a weak THC through this critical weak interglacial. Comparing ODP 926 and DSDP 607 data, εNd values converge during most interglacial peaks (excepting MIS 23) and diverge otherwise. This observation indicates that northern-sourced water masses dominate the site during peak interglacials, and confirms that the THC has been strongest during peak interglacials throughout the studied interval. Otherwise, diverging εNd values indicate a stronger southern-source signal and weaker northern-source signal at the ODP 926 site. This confirms that there was an active but variable THC system before, during, and after the MPT, with stronger deep water export from the North Atlantic during interglacials.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Ceara Rise; DSDP Site 607; Deep Sea Drilling Project; Equatorial Atlantic; IPOD; Leg 154; Leg 163; Leg 177; Leg 94; Mid-Atlantic Ridge; North Atlantic; Northeast Atlantic; ODP Site 1090; ODP Site 926; ODP Site 988; Ocean Drilling Program; South Atlantic
Coordinates: N034309 N034309 W0425430 W0425430
N654215 N654215 W0345216 W0345216
S425449 S425449 E0085359 E0085359
Record ID: 2018008125
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