Carbon Deposition Rates and Deep Water Residence Time in the Equatorial Atlantic Ocean Throughout the Last 160,000 Years

  1. E.T. Sundquist and
  2. W.S. Broecker
  1. W. B. Curry and
  2. G. P. Lohmann

Published Online: 18 MAR 2013

DOI: 10.1029/GM032p0285

The Carbon Cycle and Atmospheric CO: Natural Variations Archean to Present

The Carbon Cycle and Atmospheric CO: Natural Variations Archean to Present

How to Cite

Curry, W. B. and Lohmann, G. P. (1985) Carbon Deposition Rates and Deep Water Residence Time in the Equatorial Atlantic Ocean Throughout the Last 160,000 Years, in The Carbon Cycle and Atmospheric CO: Natural Variations Archean to Present (eds E.T. Sundquist and W.S. Broecker), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM032p0285

Author Information

  1. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1985

ISBN Information

Print ISBN: 9780875900605

Online ISBN: 9781118664322

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Keywords:

  • Carbon cycle (Biogeochemistry)—Congresses;
  • Atmospheric carbon dioxide—Congresses;
  • Geological time—Congresses;
  • Paleothermometry—Congresses;
  • Geology, Stratigraphic—Congresses

Summary

In the deep, silled basins of the equatorial Atlantic Ocean, large changes have occurred in the rates of carbonate production and dissolution, deep water residence time, and rates of organic carbon accumulation over the last 160,000 years. Accumulation of carbonate in shallow, relatively undissolved sediments decreased by one half during glacial maxima, reflecting reduced surface water production of carbonate. The most severe dissolution occurred during stage 4 (64,000 to 75,000 years B.P.) when carbonate accumulation decreased abruptly below 3750 m. Benthic foraminiferal δ13C decreased below 3750 m during all glacial maxima, reflecting greater remineralization of organic carbon and reduced dissolved oxygen concentrations below sill depth (˜3750 m) within the eastern Atlantic. While the reduced [O2] inferred during stage 2 (13,000 to 32,000 years B.P.) can be attributed predominantly to increased residence time of the deep water, the lower [O2] during stage 4 resulted largely from increased delivery of organic carbon to the deep eastern basins. No bathymetric gradient in benthic foraminiferal δ13C is detectable during stage 5e (115,000 to 125,000 years B.P.), implying that the eastern Atlantic was as well ventilated with deep water during the last interglacial period as it is today. During stages 1 and 5, organic carbon accumulation was constant below 3000 m. During stages 2, 3 and 4, the accumulation of organic carbon increased below 3750 m, reflecting in part better preservation because of reduced oxygen conditions.