15_pleistocene - Pleistocene Transition into the Pleistocene

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Pleistocene Transition into the Pleistocene Glacial-interglacial cycles for the past 2.7 m.y. Overall cooling trend = increase in δ 18 O Increase in amplitude of oscillations increasing instability
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Glacial Interglacial Cycles Lisecki and Raymo, 2005 = LR04 Stack Plio Pleist
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Pleistocene Transition Raymo, 1994 Site 607- North Atlantic Holocene 5c MIS 2/1 IG G 41k world 100k world
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Glacial Interglacial Cycles Fig 1 from Raymo and Huypers, 2008 Mid Pleistocene transition - MPT
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MIS 3 Rahmstorf, 2002 Marine data: Sachs and Lehman, 1999)
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41k vs 100 k Worlds Imbrie et al., 1992 δ 18 O climate record Earth’s eccentricity record Separated by the Mid Pleistocene Transition (MPT) Stopped here
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Imbrie et al., 1984
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100k Problem Imbrie et al., 1992
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100k Problem Related to the size of the glaciers. Mix et al., Leg 138, 1995 Eastern Equatorial Pacific Benthic record IG G 41 k 100 k
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100k Problem Regolith Hypothesis (Clark and Pollard, 1998) Easily deformable sediment (regolith) under the ice allowed more sliding = thinner ice = more rapid response By MPT- glaciers largely on bedrock- able to grow larger
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100k Problem Ruddiman 11-15 Variations in ice sheet volume (also low lat proxies) * Threshold in size of ice sheets- Larger can survive weak insolation maxima * Thinner, easier to melt during 41k
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41k Paradox Precession has the greatest impact on summer insolation, so why is there no 23k cycle during 41k world and limited 23k variability during 100k world? Ruddiman 11-1
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41k Paradox Huybers (2006) Summers with greatest insolation are shorter than average. Need to look at total summer insolation Raymo et al. (2006) Northern and southern ice growth cancel each other out ( Ruddiman (2006) 41k CO2 feedback strong
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Stage 11 Problem 1 2 3 4 5 Marine Isotope stages (MIS) .1 .3 .5 Stage 11 problem- limited forcing linked to large Termination between 12 and 11 5 7 9 11 13
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Sequence of events Ice volume clearly lags insolation by several 1000 yrs Ruddiman Fig. 9-9
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Sequence Fedorov and Philander, 2003 CO 2 and temperature covary during G/IG cycles (forcing CO2 (fast response) / ice volume (slow response) SST) Vostock Ice core records
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NADW Review Ruddiman 10-14 Higher δ 13 C = younger Increased NADW supported by: - Pa/Th - Nd isotopes
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NADW Review McManus et al., 2004 Glacial- weaker AMOC IG- Stronger AMOC
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NADW review Piotrowski et al., 2005
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This document was uploaded on 07/08/2011.

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15_pleistocene - Pleistocene Transition into the Pleistocene

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