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					Glacial/Interglacial cycles




   Dansgaard/Oeschger
   Cycles: 1500-year temp.
   Changes in Greenland ice



                              - 35 o/oo


                              d18O ice

                              - 45 o/oo
Ice-rafted Debris (IRD) in the North Atlantic:
Heinrich Events
Bond et al., 1993
     glacier                          Ocean

                      Bedrock pinning
                      point
     glacier                       Ocean

            Geothermal heat

     glacier                  Ocean
     glacier
                                        Binge-Purge Model
                  melting

  glacier
                                Ocean
New Bedrock pinning
point
  Salt-Oscillator model of ocean circulation



Thermohaline
                                Heat and
 convection          +          Moisture


            -                         +


     Freshwater            +
        inputs                        Ice Sheet
                                        Melting
Blunier et
al., 1998
Marchal et
al., 1999
Broecker, 2003.
                t




Teller, 2004.
YD
1 Sv = 1 million m3/sec
Hughen, 1998, Atmospheric radiocarbon and ocean
circulation
YD
Lowell
et al., 2006
• The North Atlantic is now growing fresher- about 0.2
  Sv of water per year added over the past 30 years.
• Lake Agassiz outbursts: up to 5 to 10 Sv per year
• Need rapid, massive melting
Overpeck et al., 2006

				
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posted:7/28/2013
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