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AGU: Paleoceanography

 

Index Terms

  • Meteorology and Atmospheric Dynamics: Paleoclimatology
  • Oceanography: General: Paleoceanography
  • Oceanography: Physical: Sea level variations
  • Oceanography: Physical: Western boundary currents

Abstract

PALEOCEANOGRAPHY, VOL. 16, NO. 3, P. 293, 2001
doi:10.1029/1999PA000474

Late Quaternary changes of western equatorial Atlantic surface circulation and Amazon lowland climate recorded in Ceará Rise deep-sea sediments

Carsten Rühlemann

Department of Geosciences, University of Bremen, Bremen, Germany

Bernhard Diekmann

Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

Stefan Mulitza

Department of Geosciences, University of Bremen, Bremen, Germany

Martin Frank

Institute for Isotope Geology and Mineral Resources, Department of Earth Sciences, ETH Zentrum, Zürich, Switzerland

Today the western tropical Atlantic is the most important passage for cross-equatorial transfer of heat in the form of warm surface water flowing from the South into the North Atlantic. Circulation changes north of South America may thus have influenced the global thermohaline circulation system and high northern latitude climate. Here we reconstruct late Quaternary variations of western equatorial Atlantic surface circulation and Amazon lowland climate obtained from a multiproxy sediment record from Ceará Rise. Variations in the illite/smectite ratio suggest drier climatic conditions in the Amazon Basin during glacials relative to interglacials. The 230Thex-normalized fluxes and the 13C/12C record of organic carbon indicate that sea level fluctuations, shelf topography, and changes of the surface circulation pattern controlled variations and amplitude of terrigenous sediment supply to the Ceará Rise. We attribute variations in thermocline depth, reconstructed from vertical planktic foraminiferal oxygen isotope gradients and abundances of the phytoplankton species Florisphaera profunda, to changes in southeast trade wind intensity. Strong trade winds during ice volume maxima are associated with a deep western tropical Atlantic thermocline, strengthening of the North Brazil Current retroflection, and more vigorous eastward flow of surface waters.

Received 26 October 1999; accepted 26 January 2001; published 1 June 2001.

Citation: Rühlemann, C., B. Diekmann, S. Mulitza, and M. Frank (2001), Late Quaternary changes of western equatorial Atlantic surface circulation and Amazon lowland climate recorded in Ceará Rise deep-sea sediments, Paleoceanography, 16(3), 293–305, doi:10.1029/1999PA000474.

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