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The last 600ky…

The last 600ky…. LGM Last Glacial Maximum 18Ky. Paleoclimataology. Lecture notes from Ellen Druffel. 1. Eccentricity. • 3% range of variation of E-S distance due to eliptical orbit around Sun, Pull of large planets • Now, perihelion occurs during northern Winter (3 January)

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The last 600ky…

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  1. The last 600ky… LGM Last Glacial Maximum 18Ky

  2. Paleoclimataology Lecture notes from Ellen Druffel

  3. 1. Eccentricity • 3% range of variation of E-S distance due to eliptical orbit around Sun, Pull of large planets • Now, perihelion occurs during northern Winter (3 January) • 100ky and 413ky periods • Now, e =.0167 (relatively circular)

  4. 2. Tilt - Reason for Seasons • Now tilt is 23.5°, and is decreasing. • Higher the tilt, higher the seasonal differences • Has gone from 24.5° -22.2°, varied by pull of large planets • 41 ky period

  5. 3. Precession - WobbleVaries E-S distance with season • Variation of the direction in which the E axis leans. • Caused by the pull of Sun and moon on Earth • Now Earth’s axis points to Polaris • 23 ky stronger period - combined wobble and slow turning of eliptical orbit. Now 11Kya

  6. On the long term…the precessional index Eccentricity variations at 100Ky and 413Ky modulate the amplitude of the precession cycle. This is why we have the 100Ky ice age cycle!

  7. How orbital theory, climate records (18O)and northern hemisphere insolation (i.e. melting in N. Atlantic) compare over the past 600ky. now LGM 18ky Cold warm

  8. BLAG invokes chemical weathering

  9. Molnar & England, 1990

  10. Molnar & England, 1990

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