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  • Mike Doran <mike@usinter.net>
    Nature 411, 157 - 162 (2001); doi:10.1038/35075500 http://www.nature.com/cgi-taf/DynaPage.taf?
    Message 1 of 1 , Jan 27, 2003
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      Nature 411, 157 - 162 (2001); doi:10.1038/35075500

      http://www.nature.com/cgi-taf/DynaPage.taf?
      file=/nature/journal/v411/n6834/abs/411157a0_fs.html&dynoptions=doi104
      3519026

      Closing of the Indonesian seaway as a precursor to east African
      aridification around 3–4 million years ago

      MARK A. CANE* AND PETER MOLNAR†

      * Lamont-Doherty Earth Observatory of Columbia University, Palisades,
      New York 01964-8000, USA † Department of Earth, Atmospheric, and
      Planetary Sciences, Massachusetts Institute of Technology, Cambridge,
      Massachusetts 02139, USA; and Department of Geological Sciences,
      Cooperative Institute for Research in Environmental Science, Campus
      Box 399, University of Colorado, Boulder, Colorado 80309, USA

      Correspondence and requests for materials should be addressed to
      M.A.C (e-mail: mcane@...).

      Global climate change around 3–4 Myr ago is thought to have
      influenced the evolution of hominids, via the aridification of
      Africa, and may have been the precursor to Pleistocene glaciation
      about 2.75 Myr ago. Most explanations of these climatic events
      involve changes in circulation of the North Atlantic Ocean due to the
      closing of the Isthmus of Panama. Here we suggest, instead, that
      closure of the Indonesian seaway 3–4 Myr ago could be responsible for
      these climate changes, in particular the aridification of Africa. We
      use simple theory and results from an ocean circulation model to show
      that the northward displacement of New Guinea, about 5 Myr ago, may
      have switched the source of flow through Indonesia—from warm South
      Pacific to relatively cold North Pacific waters. This would have
      decreased sea surface temperatures in the Indian Ocean, leading to
      reduced rainfall over eastern Africa. We further suggest that the
      changes in the equatorial Pacific may have reduced atmospheric heat
      transport from the tropics to higher latitudes, stimulating global
      cooling and the eventual growth of ice sheets.

      Comment:

      This study I basically agree with even as it doesn't get into the
      specific causal mechanism other than the movement of the terresphere
      and displacement of a more saline resource of the S. Pacific w/ a
      more diluted source in the N. Pacific. A warm, saline body of water
      is going to be a conductive body--and will allow EMFs to travel, say,
      from strong flaring/CME event all the way from the S. Pacific.
      Imagine an El Nino type CME event where there is 900 proton per CM
      solar wind, earth directed, in the S. Hemispheric "summer" -- you
      might have 20 hours or more of EMF directed on a region with powerful
      contrasting EMF gradiants between terresphere and ocean--at all times
      impacting Africa. Already Africa is the most struck land mass on
      earth--as it is south of the fair weather Mediterranean. 5 million
      years ago the Straights of Gilbralter closed and the Med dried up
      like the Dead Sea is--leaving behind a salt layer--but then it
      reflooded. This kind of activity would create incredible fair weather
      voltages when contrasted with the pulses of EMF that could come from
      the Pacific oceans. This is an interesting study, but again, could go
      further if were exactly understood what, say, a Kelvin wave REALLY is
      from a Gaia standpoint.
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