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14. Last 125 kyr - Pre-show The Day After Tomorrow In 7-10...

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Pre-show: The Day After Tomorrow “In 7-10 days, when this storm is over, we’ll be in a new ice age.”
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14. The last 125,000 yr & abrupt climate change The world 20 ka Iceberg armadas & conveyor Greenland: 10-20°C in 50 years? Monsoons The Younger Dryas 12.9 ka
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Would we be starting into an ice age w/o CO2? deglaciation future today Insolation w/m2 65°N No! Broecker & EPICA ‘04 use stage 11/Termination V analog, very long interglacial “The interglacial stage following Termination V was exceptionally long—28,000 years compared to, for example, the 12,000 years…[for the present] interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.” Epica members, 2004, Nature Yes! Laskar’s astronomical solution predicts that we would be entering a glacial if not for anthropogenic CO2 5-6 kyr lag
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reflects both temperature and ice-volume changes δ 18O: Proxy ice-volume (sea-level) measurement
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Arabian Sea for July-September 1979, showing the large area of high productivity waters that develops under the influence of the southwest monsoon Arabian Sea for April-June 1979, a period of low productivity preceding the development of the southwest monsoon. http://disc.gsfc.nasa.gov/oceancolor/scifocus/classic_scenes/04_classics_arabian.shtml Monsoons Monsoons seasonally reversing winds and precipitation Due to land-sea contrast Modern example: “Indian” monsoon Rainy season (May/June-Aug. in India/SE Asia)
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Indian Monsoon affects a large area of the planet from Africa to Australia Surface winds August Surface currents August Monsoons:seasonally reversing winds & precip
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heat up N hemisphere continent in summer rising air (low), onshore winds winter cold continents, offshore winds strongly affected by 19/23 kyr precessional cycle Last glacial maximum: weaker monsoon Peak monsoon ~8 kyr Why not 10-11 kyr at insolation max? Lag in climate system explains changes in precipitation in Quaternary Med. How the monsoon works: land-sea contrasts http://www.nc-climate.ncsu.edu/edu/k12/.Monsoons
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http://www.geo.uu.nl/Research/Geochemistry/SAP.html High precipitation results in low salinity cap, anoxia/suboxia, sapropels organic rich (>2%) sediments during precessional minima (minima have higher insolation, high P/E, stronger monsoon) Mediterranean organic-rich sediments
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Evidence of wetter Sahara 8 ka The top image shows the Safsaf Oasis on the surface of the Sahara. The bottom (using radar) is the rock layer underneath, revealing black channels cut by the meandering of an ancient river that once fed the oasis.
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Mediterranean Milankovitch beat
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Carbonate cycles lower Pliocene (Punta di Maiata, Sicily, Italy )
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Clicker question What are monsoons?
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