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      The surface of the ice-age Earth.

      CLIMAP Project Members
      Science (New York, N.Y.)
      American Association for the Advancement of Science (AAAS)

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          Abstract

          In the Northern Hemisphere the 18,000 B.P. world differed strikingly from the present in the huge land-based ice sheets, reaching approximately 3 km in thickness, and in a dramatic increase in the extent of pack ice and marine-based ice sheets. In the Southern Hemisphere the most striking contrast was the greater extent of sea ice. On land, grasslands, steppes, and deserts spread at the expense of forests. This change in vegetation, together with extensive areas of permanent ice and sandy outwash plains, caused an increase in global surface albedo over modern values. Sea level was lower by at least 85 m. The 18,000 B.P. oceans were characterized by: (i) marked steepening of thermal gradients along polar frontal systems, particularly in the North Atlantic and Antarctic; (ii) an equatorward displacement of polar frontal systems; (iii) general cooling of most surface waters, with a global average of -2.3 degrees C; (iv) increased cooling and up-welling along equatorial divergences in the Pacific and Atlantic; (v) low temperatures extending equatorward along the western coast of Africa, Australia, and South America, indicating increased upwelling and advection of cool waters; and (vi) nearly stable positions and temperatures of the central gyres in the subtropical Atlantic, Pacific, and Indian oceans.

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          Author and article information

          Journal
          Science
          Science (New York, N.Y.)
          American Association for the Advancement of Science (AAAS)
          0036-8075
          0036-8075
          Mar 19 1976
          : 191
          : 4232
          Article
          191/4232/1131
          10.1126/science.191.4232.1131
          17781630
          b2e57f8b-c2ea-4f76-8777-bef91d57aded
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