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Publication Detail
Climate threshold at the Eocene-Oligocene transition: Antarctic ice sheet influence on ocean circulation
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Conference Proceeding
  • Authors:
    Miller KG, Wright JD, Katz ME, Wade BS, Browning JV, Cramer BS, Rosenthal Y
  • Publication date:
  • Pagination:
    169, 178
  • Journal:
    Special Paper of the Geological Society of America
  • Volume:
  • Status:
  • Print ISSN:
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 × 10 6 km 3 ) was a primary cause of a dramatic reorganization of ocean circulation and chemistry. The Eocene-Oligocene transition (EOT) was the culmination of long-term (10 7 yr scale) CO 2 drawdown and related cooling that triggered a 0.5%-0.9% transient precursor benthic foraminiferal δ 18 O increase at 33.80 Ma (EOT-1), a 0.8% δ 18 O increase at 33.63 Ma (EOT-2), and a 1.0% δ 18 O 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 δ 18 O 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 δ 18 O 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. © 2009 The Geological Society of America.
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