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Orbital-Scale Interactions in the Climate System

Explore the fast and slow response times of different climate system components and the influence of ice-driven responses on the climate. Learn about the orbital cycles and their effects on regions remote from Northern Hemisphere ice sheets. Understand the relationship between CO2 levels and ice volume, as well as the causes of abrupt deglaciations.

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Orbital-Scale Interactions in the Climate System

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  1. Chapter 12 Orbital-Scale Interactions in the Climate System 報告學生:彭炯博

  2. Orbital-Scale Forcing and Response Revisited • Fast response time. • Slow response time.

  3. Fast response time • One part of the climate system has a fast response time , measured in months or years. • Example: monsoon. • No thermal inertia and so easily influenced by other parts of the climate system.

  4. Slow response time • One part of the climate system has a slow response time, measured in many thousands of years. • Example: ice sheets. • Have a large thermal inertia and independent from other parts of the climate system.

  5. Ice-Driven Responses

  6. Ice-Driven Responses in High Northern Latitude

  7. Region of ice-driven responses

  8. North Atlantic surface response to ice

  9. The ice sheets to influence Atmosphere • A clockwise flow of wind occurred around the central dome of North American ice sheet. • The presence of a high-albedo ice surface at latitudes where snow does not fall today. • The hung ice sheet ???.

  10. Climate in Northern Europe and Asia

  11. European vegetation France

  12. Surface-ocean sensitivity test

  13. Responses of windblown debris in East Asia to ice colume

  14. In summary the ice volume signal can be transferred far from the immediate proximity.

  15. Orbital Cycles in Regions Remote from Northern Hemisphere Ice N. African monsoon ~ 23,000 years, a summer season phenomenon Ice-sheet signals ~ 41,000 and 100,000 years , a winter season phenomena So, no significant effect may be felt across the eq. Yet, ice sheet signal shows up in many faraway regions

  16. Responses of windblown debris in the Arabian Desert to ice volume Pollen responses in South America to ice volume

  17. Pollen responses in New Zealand to ice volume Response of Southern Ocean temperature to ice volume

  18. Northern or southern ice sheet forcing? Out-of-phase summer insolation between the hemispheres

  19. Phasing of insolation vs. ice volume

  20. Global transfer of signals from Northern hemisphere ice sheets, via sea level: continental vs marine climate deep water formation CO2

  21. CO2 Level and Ice Volume Which Drives Which ?

  22. Relative timing of ice volume and changes in CO2

  23. Why Have Ice Sheets Grown Larger since 0.9 Myr Ago ?

  24. Changes in 18O in the last 4.5 Myr

  25. Ice slipping may affect ice sheet volume

  26. What Causes Abrupt Deglaciations?Strong summer insolation peaks pace rapid deglaciations

  27. Strong summer insolation peaks pace rapid deglaciations

  28. Numerical model: insolation control of ice volume

  29. Conceptual (SPECMAP) model of ice-driven climate changes

  30. Summary • Climate scientists are close to a full theory of ice sheet variations over the last 2.75 Myr. For the first two-thirds of this interval, growth and melting of northern hemisphere ice sheets were controlled by changes in summer insolation at rhythms of 41,000 and 23,000 years, as Milankovitch predicted. By 900,000 years ago, global cooling permitted ice sheets to begin growing larger. The dominant 100,000-year rhythm of change in these ice sheets was paced by changes in summer insolation but ultimately governed by internal feedbacks produced by the ice sheets, including changes in atmospheric CO2.

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