PaleoClimate

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PaleoClimate

• Mechanisms for
• Glacial-Interglacial Oscillations

By Gillian Robbins
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Ice Ages

• 1. Huronian
• (2.7-2.3 billion yrs ago)
• 2. Snowball Earth
• (850-630 million yrs ago)
• 3. Andean Saharan
• (460-430 million yrs ago)
• 4. Present Age
• (40 million yrs ago-Today)

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Climate Variation
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The Milankovitch Debate

• Oscillation Theories
• 1920 Milankovitch Cycles
• Orbital Forcing
• VS
• 1990-94 Imbrie, Ghil, and Saltzman
• 2000 Gildor and Tziperman
• Milankovitch is incomplete (at the 100,000
  yr time scale)

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Sea-Ice Switch Mechanism,Model

• Develop Ocean-atmosphere-sea, ice-land, ice
  climate system box model
• Results
• self sustaining oscillations without external,
  Milankovitch forcing.
• The asymmetric sawtooth structure is observed
• Conclude
• Abrupt sea-ice growth and retreat acts as a
  switch for glacial-interglacial changes

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Switch is On

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Switch is Off

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Why 100 kyr?
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The future of the Holocene?

• Global Warming and its impacts
• Becoming an ice free environment
• Resulted feedbacks in climate system

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Ref

• Hezi, G., Tziperman, E. (2001) Journal of
  Geophysical Research 106, 9117-9133.
• Hezi, G., Tziperman, E. (2003) Philosophical
  Transactions Royal Society London 361, 1935-1944
• Pixar
• An unidentified user lecture figure from MIT