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Unformatted text preview: 1 Climate Records Landforms give ice extent (not continuous, hard to date) More continuous records 1. Sedimentary rocks (to 2.5 by) 2. Ocean sediments (last 150 my) 3. Ice cores (annual to millenial resolution, to about 700 ky) 4. Tree rings (annual resolution, last 10 ky) 5. Corals (seasonal resolution, last 2-10 ky) 6. Lake sediments (often decades to centuries) 7. Historical records (decades to few hundred years) Proxies: Pollen, fauna, grain sizes, isotopes On what time scales does climate vary? 725 Ice cover 20 ka 727 Pieter Brueghel Hunters in the Snow, 1575 726 Bristle cone pine Tree Rings Bristle Cone Pine 762 Kilomanjaro Ice Core records Mt. Kilomanjaro 766 Kilo top 2 728 Reedy Glacier, Antarctica Antarctic Ice sheet 729 Bubbles in Vostock ice core, Antarctica k: T, CO2, CH4 vs. time CO2 from gas bubbles (cold when low CO2) Temperature from isotopes Methane from gas bubbles (high = wet, when warm) Ice Core Record 730 Vostock: T, Al, Na, acid vs. time Aluminum = silicate dust (arid when cold) Sodium = sea salt from wind (windy when cold) Acid = volcanic eruptions Note lack of correlation to Temp Temperature from isotopes Ice Core Record Milankovitch cycles: 400ky How do we know temperature? Notation for Oxygen Isotopes: 18 O = (R sample /R std- 1)*1000 R i = 18 O/ 16 O = 1/500 2 728 Reedy Glacier, Antarctica Antarctic Ice sheet 729 Bubbles in Vostock ice core, Antarctica k: T, CO2, CH4 vs....
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This note was uploaded on 11/30/2010 for the course GEOL 125Lxg at USC.