Climate threshold at the Eocene-Oligocene transition; Antarctic ice sheet influence on ocean circulation

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doi: 10.1130/2009.2452(11)
Author(s): Miller, Kenneth G.; Wright, James D.; Katz, Miriam E.; Wade, Bridget S.; Browning, James V.; Cramer, Benjamin S.; Rosenthal, Yair
Author Affiliation(s): Primary:
Rutgers University, Department of Earth and Planetary Sciences, Piscataway, NJ, United States
Osservatorio Geologico di Coldigioco, Italy
Rensselaer Polytechnic Institute, United States
Texas A&M University, United States
Volume Title: Late Eocene Earth; hothouse, icehouse, and impacts
Volume Author(s): Koeberl, Christian, editor; Montanari, Alessandro
Source: Special Paper - Geological Society of America, Vol.452, p.169-178; Geological Sociaty of America (GSA) Penrose conference, Ancona, Italy, Oct. 3-6, 2007, edited by Christian Koeberl and Alessandro Montanari. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0072-1077. ISBN: 978-0-8137-2452-2 CODEN: GSAPAZ
Note: In English. NSF grants EAR-06-06693 and OCE-06-23256. 86 refs.; illus., incl. strat. col.
Summary: We present an overview of the Eocene-Oligocene transition from a marine perspective and posit that growth of a continent-scale Antarctic ice sheet (25×106 km3) was a primary cause of a dramatic reorganization of ocean circulation and chemistry. The Eocene-Oligocene transition (EOT) was the culmination of long-term (107 yr scale) CO2 drawdown and related cooling that triggered a 0.5 ppm-0.9 ppm transient precursor benthic foraminiferal δ18O increase at 33.80 Ma (EOT-1), a 0.8 ppm δ18O increase at 33.63 Ma (EOT-2), and a 1.0 ppm δ18O increase at 33.55 Ma (oxygen isotope event Oi-1). We show that a small (∼25 m) sea-level lowering was associated with the precursor EOT-1 increase, suggesting that the δ18O increase primarily reflected 1-2°C of cooling. Global sea level dropped by 80±25 m at Oi-1 time, implying that the deep-sea foraminiferal δ18O increase was due to the growth of a continent-sized Antarctic ice sheet and 1-4°C of cooling. The Antarctic ice sheet reached the coastline for the first time at ca. 33.6 Ma and became a driver of Antarctic circulation, which in turn affected global climate, causing increased latitudinal thermal gradients and a "spinning up" of the oceans that resulted in: (1) increased thermohaline circulation and erosional pulses of Northern Component Water and Antarctic Bottom Water; (2) increased deep-basin ventilation, which caused a decrease in oceanic residence time, a decrease in deep-ocean acidity, and a deepening of the calcite compensation depth (CCD); and (3) increased diatom diversity due to intensified upwelling.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Alabama; Antarctic ice sheet; Antarctica; Cenozoic; East Pacific; Eocene; Equatorial Pacific; Isotope ratios; Isotopes; Leg 199; Lithostratigraphy; Lower Oligocene; New Jersey; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1218; Ocean Drilling Program; Oligocene; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleogene; Paleotemperature; Sea-level changes; Stable isotopes; Tertiary; United States; Upper Eocene
Coordinates: N085300 N085300 W1352200 W1352200
Record ID: 2009074337
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