13. Icehouse - Pre-show: The Day After Tomorrow 13. Descent...

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Pre-show: The Day After Tomorrow
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13. Descent into the Icehouse ca. 3 Ma sea level peak Glaciation of Antarctica ca. 34 million years ago 2.6 Ma ice ages begin Very large ice ages last million yr
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18O and sea level δ Million yr scale Late Cretaceous-Eocene: ephemeral Antarctic ice: 15-30 m sea-level changes Oligocene-mid Miocene: large, variable Antarctic ice 30-60 m sea-level changes late Pliocene-Recent: Antarctic and large, variable Northern Hemisphere ice: 30-120 m sea-level
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Paradise Lost: Into the Icehouse +14 Icehouse Greenhouse 33.5 Ma Big Chill 33rd millionth Anniversary
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Benthic foraminiferal δ 18O (‰) Age (Ma) Miller et al., 1987 colder, more ice warmer, less ice 10 20 30 40 50 60
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Greenhouse-Icehouse transition ca. 34 Ma
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Unlocking the Icehouse: ca. 34 Ma glaciation Miller et al. (1991) CaCO3 748
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55 m eustatic lowering Oi1 NJ ~0.5-0.8‰ due to ice; ~75-100% modern EAIS 1-2°C deep-sea cooling ca. 34 Ma (e. Oligocene) Oi1 1‰ δ 18O increase
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Heartbeat of the Greenhouse-Icehouse transition Animation courtesy of D. Pollard after DeConto and Pollard (2002) Beginning illustrates Greenhouse ice growth and decay (~3X CO2) End illustrates Oligocene Icehouse (<2.8X CO2 )
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Earliest Oligo. Oi1 1‰ δ 18O increase benthic foram. δ 18O increase Atlantic, Pacific, Indian, Southern Beginning of Icehouse: near modern sized ice sheets E. Antarctica Major changes in deep- sea circulation Global cooling: pollen, mammalian, floral, ostracod, benthic foraminiferal changes Drop in CO2 (Pagani)
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Mt. Everest Collision began ~50 Ma Accelerated in Miocene Increased weathering = atm. CO2 decrease CaSiO3 + CO2 = CaCO3 + SiO2 Tibetan Plateau Decreasing CO2 since 50 Ma
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Ocean Heat Transport major tectonic events influence oceanic circulation Opening or closing of critical gateways Narrow passages link major ocean basins Two critical gateways Opening of Drake Passage producing the Antarctic Circumpolar Current (ACC) Uplift of the Isthmus of Panama stopped equatorial flow between Atlantic and Pacific Explore Antarctica - L. Crossley Opening of Tasman Seaway Opening of Drake Passage Closing of Isthmus of Panama
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www.scotese.com closed gateways open gateways Open: ACC, thermal isolation of Antarctica to initiate glaciations Closed: flow from north kept Antarctica warm
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What is an Icehouse world? A)
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This note was uploaded on 12/16/2011 for the course SEA CHANGE 110 taught by Professor Miller during the Spring '11 term at Rutgers.

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13. Icehouse - Pre-show: The Day After Tomorrow 13. Descent...

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