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North Atlantic Drift Current and Abrupt Climate Change

  1. Apr 13, 2010 #1
    There is a belief that a complete interruption of the North Atlantic drift current could cause abrupt climate change.

    The amount of heat transported by the North Atlantic drift current and the Gulf stream is 8 times smaller than the amount of heat transported by the atmosphere transferring the summer heat that is absorbed by the ocean.

    That mechanism (a complete interruption of the North Atlantic drift current) is not capable of causing the Younger Dryas 1000 year abrupt cold period. It also is not capable of causing the Heinrich events.


    http://www.americanscientist.org/issues/id.999,y.0,no.,content.true,page.1,css.print/issue.aspx

    http://www.atmos.washington.edu/~david/Gulf.pdf


     
  2. jcsd
  3. Apr 14, 2010 #2

    Xnn

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    Saul;

    The article's you've linked to appear to be fairly correct.

    I also agree that Heinrich events were not caused by changes in Atlantic ocean currents.
    The ice shelf responsible for Heinrich events was located near the Hudson strait.
    That's a long way from the Atlantic and the Gulf currents. It was unstable and once it started to fall apart (just like an avalanche) there was not much that was going to stop it. However, now that it is gone, it is gone.

    Now, what some people have realized, is that while we are not going to see another precisely Heinrich event in the near future, it is entirely possible that we may witness another collapse of a very large ice shelf. The West Antarctic is the area of prime concern as there is a large amount of ice grounded on land that is already underwater. Clearly, this is not a stable situation. Once it starts to break up, there is very little that can stop it.

    Heinrich and the Younger Dryas were primarily a Northern Hemipshere events. So, it we are about to witness a breakup of the the West Antarctic, then there is no similar analogy.
     
  4. Apr 15, 2010 #3
    The ice purge during the Heinrich events is from multiple ice sheets. The bing purge ice sheet mechanism could not explain ice sheet purges from multiple ice sheets.

    As a side note the current abrupt Greenland ice sheet purge into the Atlantic ocean has abruptly stopped. Why it started and why it abruptly stopped (Five separate and independent ice sheet flows is not known.)

    But back to the melt water pulse. A total stoppage of the North Atlantic drift current could not have caused the Younger Dryas abrupt cooling. The during the Younger Dryas abrupt cooling the Northern Hemispere went from interglacial warm (insolation at the critical 65N was the highest in 100,000 years) to glacial cold with 70% of the cooling occurring within 15 years. The remainder of the Younger Dryas cooling was complete in 40 years.

    During the Younger Dryas each winter the North Atlantic ocean frozen to the latitude of mid-Spain.

    The Younger Dryas is a Heinrich event. These are cyclic events. The melt water pulse is a red herring and the ice sheet surges is also a red herring.

    There is a misconception as the first guess as to what caused the cyclic Heinrich event was incorrect, that a Heinrich event cannot occur during an interglacial. That is not correct. The Younger Dryas occurred. What caused the Younger Dryas? What caused the 8,200 year ago cooling event.

    All of the previous interglacial periods ended abruptly. The climate forcing function is the same. Its affect on the planet, however, depends on the stage of the glacial/interglacial cycle when it occurs as well as specifics that are connected with the forcing function.
     
  5. Apr 16, 2010 #4
    Has the younger dryas not been noted as starting about 500 years earlier in the Southern Hemisphere. This largely from ice cores from mid lattitude glaciers?
     
  6. Apr 16, 2010 #5
    Thank you for posting this, it gives cause for thought and cetainly suggests much more work need to be done before we can reliably and confidantly explain some of these things.
     
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