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The Climate System and Glaciation Chapter 10

This chapter explores long-term global cooling trends, focusing on significant climatic fluctuations over millions of years. It examines historical data from Vostok Station and the Greenland Ice Core GISP2B, revealing a cooling trend of 0.22°C per million years. The discussion includes key theories of climate change, such as Milankovitch cycles and their components—eccentricity, axial precession, and obliquity. Additionally, the chapter highlights the role of atmospheric composition, including greenhouse gases, and the impact of major glacial episodes on Earth's thermal balance and climate dynamics.

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The Climate System and Glaciation Chapter 10

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  1. The Climate System and Glaciation Chapter 10

  2. Long Term Global Cooling Trend -16oC 55 million years 0.22oC /million years

  3. Vostock Station CoreAntarctica

  4. A Greenland Ice Core GISP2B Site 1144 Planktonic Core

  5. Temperature reconstructed from Greenland Ice core

  6. Global temperature- instrumental record

  7. Thermal Balance

  8. Major Theories on Climate Change • Orbital Forcing • (Astronomical Theory, Milankovitch Cycles) • Changes in Atmosphere • Reflection-Transmission • Global Circulation Patterns • Atmosphere • Ocean

  9. 3. Variations in Earth - Sun Relations (Astronomical Theory, Milankovitch Cycles) • One of the most popular theories • Used to explain several types of phenomena through geologic time • Can be modeled simply

  10. Cycle Components

  11. Eccentricity • About 100,000 years • Change in orbit shape and center • Main component 110,000 years, minor component 413,000 years • Currently more circular • Jan 3 perihelion, July 4 aphelion • 6% difference between January and July • At Maximum ellipse • 20 to 30% difference

  12. Orbital Data • March 20 – September 22 = 186 Days • Aphelion 94,400,000 Miles • September 22 – March 20 = 179 Days • Perihelion 91,400,000 Miles

  13. Insolation vs Latitude

  14. Precession (wobble) • North pole pointing at the North Star, to having the North pole pointing at the star Vega • 22,000 year cycle is composed of a 19,000 cycle and a 23,000 year cycle).

  15. Two Components of Milankovitch Cycle

  16. The Next 25,000 years

  17. Climate and the Atmosphere

  18. Thermal Balance

  19. An object will heat up if energy is added: • A temperature at the surface of the earth will be reached such that Energy in = Energy out • T = 275 K = 2°C (Calculated surface temperature) • Actual surface temperature is 15°C. Difference reflects the greenhouse effect.

  20. Atmospheric Transmittance

  21. Composition of dry atmosphere below 25km

  22. Atmospheric Transmittance

  23. Composition of the atmosphere below 25km

  24. CO2

  25. Methane

  26. Nitrous Oxides (NxO)

  27. Glaciations • High Altitude • Sensitive to short term conditions (decades) • High Latitude

  28. Ash column generated by the eruption of Mount Pinatubo on June 12, 1991.

  29. Mount Pinatubo Plume

  30. Dust Veil Index • DVIa= 0.97 RmaxEmaxTmo • DVIb= 52.5 TdmaxEmaxTmo • DVIc= 4.4 Q EmaxTmo • DVI = DVIa+DVIb+DVIc • Krakatoa (1883) = 1,000

  31. Deep Global Circulation

  32. Major Atmospheric Circulation Cells

  33. Glaciations • High altitude • Short term sensitivity (decades) • Advances and retreats • High latitude • Long term sensitivity (centuries) • Thinning

  34. Major glacial pulses Illinois Episode Wisconsin Episode

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