Climate threshold at the Eocene-Oligocene transition

Antarctic ice sheet influence on ocean circulation

Kenneth Miller, James Wright, Miriam E. Katz, Bridget S. Wade, James V. Browning, Benjamin S. Cramer, Yair Rosenthal

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)169-178
Number of pages10
JournalSpecial Paper of the Geological Society of America
Volume452
DOIs
StatePublished - Jan 1 2009

Fingerprint

ice sheet
Oligocene
Eocene
climate
cooling
sea level
Antarctic Bottom Water
thermohaline circulation
ocean
drawdown
ventilation
oxygen isotope
deep sea
acidity
global climate
residence time
upwelling
diatom
calcite
ocean circulation

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

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title = "Climate threshold at the Eocene-Oligocene transition: Antarctic ice sheet influence on ocean circulation",
abstract = "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.",
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Climate threshold at the Eocene-Oligocene transition : Antarctic ice sheet influence on ocean circulation. / Miller, Kenneth; Wright, James; Katz, Miriam E.; Wade, Bridget S.; Browning, James V.; Cramer, Benjamin S.; Rosenthal, Yair.

In: Special Paper of the Geological Society of America, Vol. 452, 01.01.2009, p. 169-178.

Research output: Contribution to journalArticle

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