chapter_14 - Pleistocene Glaciations Pleistocene Chapter 14...

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Unformatted text preview: Pleistocene Glaciations Pleistocene Chapter 14 Dr. Emily Berndt Fundamentals of the Climate System EAS 253 I. Overview I. A. Viewed on multimillion-year time scales, Earth A. is presently in a glacial interval is B. Only during the past 2.5 million years have ice B. sheets extended from the Arctic into the northern latitudes northern C. There is something peculiar about the C. operation of Earth’s climate system during the past 2.5 million years that differs from the other 300 million years other Maximum Extent of Pleistocene Ice Sheet Pleistocene I. Overview I. D. There is evidence that the Pleistocene epoch D. was characterized by: was ii. cycles of growth and decay of continental . ice ice iii. Over a period from 1.8 m.y.a. to 12,000 i. y.a. y.a. E. Present warm interval is known as the E. Holocene epoch Holocene i. should end in several thousand years iii. Burning of fossil fuels could slow the i. transition to a glacial state transition I. Overview I. F. What causes the global cycles? ii. Changes in the distribution of . insolation insolation ii. Changes in atmospheric CO2 iiii. These changes are predictable ii. based on Earth’s orbit around the sun based iiv. These smaller forcings are more v. important on shorter time scales important II. Milankovitch Cycles II. A. Why has Earth’s climate system A. oscillated between glacial and interglacial states? interglacial Milankovitch Cycles Milankovitch Eccentricity Obliquity Precession II. Milankovitch Cycles II. B. Orbital Theory ii. Orbital Theory predates Milankovitch . Theory Theory ii. Kepler’s Laws s 1stt Law: The orbit of each planet is an The ellipse with the Sun at one focus ellipse nd 2nd Law: A lline joining a planet to the ine Sun sweeps out equal areas in equal times times rd 3rd Law: The square of a planet’s orbital The period is proportional to the cube of its semimajor axis semimajor Kepler’s Laws Kepler’s II. Milankovitch Cycles II. B. Orbital Theory ii. Orbital Theory predates Milankovitch . Theory Theory ii. Kepler’s Laws s Focus on the 1stt Law II. Milankovitch Cycles II. C. Changes in the Orbit through time II. Milankovitch Cycles II. D. Precession of the Spin Axis II. Milankovitch Cycles II. E. Obliquity Variations The Effects of the Sun and Moon on Earth’s Obliquity Moon II. Milankovitch Cycles II. F. Eccentricity Variations Less seasonal contrast Greater seasonal contrast II. Milankovitch Cycles II. G. Comparing Orbital Forcing and Climate G. Response Response ii. The combination of these orbital . forcings causes the climate system to oscillate between states oscillate iii. Displayed is a diagram similar to i. Daisyworld Daisyworld Stability of Glacial and Interglacial States Interglacial III. Glacial Climate Feedbacks III. ...
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