Revving the engine of ocean circulation; Antarctic Circumpolar Current development, late Eocene-early Oligocene

Author(s): Katz, Miriam E.; Cramer, Benjamin; Esmay, Gar; Liu, Chengjie; Miller, Kenneth; Rosenthal, Yair; Toggweiller, J. R.; Wade, Bridget S.; Wright, James D.
Author Affiliation(s): Primary:
Rensselaer Polytechnic Institute, Department of Earth and Environmental Sciences, Troy, NY, United States
Other:
Theiss Research, United States
Rutgers University, United States
ExxonMobil Exploration Company, United States
Geophysical Fluid Dynamics Laboratory/NOAA, United States
University of Leeds, United Kingdom
Volume Title: Geological Society of America, 2010 annual meeting
Source: Abstracts with Programs - Geological Society of America, 42(5), p.541; Geological Society of America, 2010 annual meeting, Denver, CO, Oct. 31-Nov. 3, 2010. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: A critical climate and oceanographic transition occurred during the late middle Eocene to mid-Oligocene (∼38-28 Ma), marked by global cooling and development of continental-scale Antarctic ice sheets. Progressive development of the Antarctic Circumpolar Current (ACC) and reorganization of global ocean circulation accompanied this climate transition. The ACC "engine" began to develop in the middle Eocene with shallow flow through the Drake Passage, followed by rapid deepening of the Tasman gateway (late Eocene to early Oligocene), and more gradual deepening of the Drake Passage through the remainder of the Oligocene. The ACC is a dominant feature of present-day ocean circulation and climate, influencing the strength of meridional overturning circulation, transition depth from surface to deep ocean, gas exchange rate between atmosphere and deep ocean, and global surface heat distribution. Here, we present high-resolution benthic foraminiferal d18O and d13C records with Mg/Ca data from Atlantic Slope Project corehole 5 (ASP-5; ∼600 m paleodepth, southeast US continental slope) and d18O and d13C records from ODP Site 1053 (∼1500-1750 m paleodepth; Blake Nose), with comparisons to published isotopic records (Cramer et al. 2009). We show that strengthening of interbasinal deepwater thermal differentiation during the early Oligocene was accompanied by the development of a significant carbon isotopic (d13C) offset between mid-depth (∼600 m) and deep (>1000 m) waters in the western North Atlantic. We interpret the d13C offset to indicate development of low O2 conditions associated with vertical stratification of nutrients, analogous to the modern low O2 zone (∼700-1000 m deep) that results from ventilation by Antarctic Intermediate Water. These records show that the engine of modern ocean overturning circulation, the ACC, gradually, but significantly, impacted global ocean circulation even while it was in the early development stage in the late middle Eocene to mid-Oligocene.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Antarctic Circumpolar Current; Atlantic Ocean; Blake Nose; Blake Plateau; C-13/C-12; Calcium; Carbon; Cenozoic; Cooling; Drake Passage; Eocene; Global change; Ice sheets; Isotope ratios; Isotopes; Leg 171B; Lower Oligocene; Magnesium; Metals; Mg/Ca; North Atlantic; Nutrients; O-18/O-16; ODP Site 1053; Ocean Drilling Program; Ocean circulation; Oligocene; Oxygen; Paleo-oceanography; Paleoclimatology; Paleogene; Stable isotopes; Tertiary; Upper Eocene
Coordinates: N295932 N295932 W0763125 W0763125
Record ID: 2012009031
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