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Last Glacial Maximum

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Last Glacial Maximum

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    1. Last Glacial Maximum

    2. Last Glacial Maximum LGM = 22 – 14 ky Deglaciation = 14-10 ky Holocene = 10 ky on Peak deglacial= 6-7 ky LGM Most recent glaciation (most detailed record) Largest ice volume

    3. LGM

    4. LGM

    5. LGM

    6. LGM Sea level Different locations 100-130m 110 m lower Based on coral reef drilling 129 m – CLIMAP 120 m – Fairbanks (1989)- Barbados

    7. LGM Snowlines Solid line = modern snowline Dashed = LGMSolid line = modern snowline Dashed = LGM

    8. LGM Orbital Configuration Similar to today Ice sheets were developing in response to earlier minimum Sluggish response of ice sheets Maintenance of cold climate by feedbacks (GH gases)

    9. LGM- Orbital Configuration

    10. LGM- Orbital Configuration

    11. LGM Temperatures (CLIMAP- 1970-80’s) Overall average 4°C cooler Poles 6-10°C cooler Greenland ice core data = 5-10°C Tropics 0-2°C cooler (controversial)

    12. LGM CLIMAP

    13. LGM Winds Stronger pole to equator gradient Also strong winds off the ice sheets Aridity Cooler and drier Amazon controversy Dust More, 10x more in layers of the Greenland ice sheets Mahovald et al. 1999- 2.5x more globally, 20x more high lats loess ..

    14. LGM - loess

    15. LGM Ocean Circulation Stronger winds ? stronger upwelling Decreased NADW / increased GNAIW Age of deep waters Pacific ~ to today (1600yrs) vs. LGM ~1670 Atlantic today = 350 yrs vs. LGM = 675 yrs

    16. LGM Vegetation Reduce terrestrial biomass by 25% Transfer from the continents to the oceans From ~2160 gTC to 1630 gTC Terrestrial organic carbon ~ -25 per mil d13C Reduce ocean d13C value by 0.4 per mil

    17. LGM Greenhouse gases CO2- LGM = 190 ppm Pre-Industrial = 280 ppm (~360ppm today) CH4 LGM = 300 ppb Pre-Industrial = 650 ppb (today ~1400 ppb) Vary with climate Seem to lag atm temperature change by a few 100- yrs, but lead ice volume

    18. EPICA Dome C

    19. EPICA Core Dome C

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