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Northeast Atlantic Paleoclimatic Changes over the Past 600,000 Years

By
W. F. Ruddiman
W. F. Ruddiman
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A. McIntyre
A. McIntyre
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Published:
January 01, 1976

In the subpolar Atlantic Ocean during the Quaternary Period, water-mass environments have migrated across more than 20° of latitude, which is equivalent to temperature oscillations of the ocean surface of at least 12°C. The migrations have occurred along a northwest-trending axis at mean rates of approximately 100 m/yr sustained over intervals of several centuries. During peak glaciations, polar water moved south to lat 42°N, where an abrupt frontal system separated the cyclonic subpolar gyre from the anticyclonic subtropical gyre.

Seven complete climatic cycles have occurred in the past 600,000 yr, within which at least 11 separate major southward advances of polar water have occurred. Both in number and shape, these cycles are correlative to oxygen isotopic cycles in the western equatorial Pacific Ocean and to palynologic cycles determined from a core from Macedonia. The northeast Atlantic cycle geometries are not so uniformly saw-toothed in form as isotopic curves from the equatorial Atlantic Ocean and Caribbean Sea because of interruptions by short but severe cold climatic pulses lasting for intervals as short as a few thousand years. One such pulse, which lasted only 7,000 yr, retained at least 90% of its original peak intensity despite vertical mixing.

Quantitative determination of the absolute input rates of the major sediment fractions over the glacial and interglacial portions of the last major climatic cycle shows that coccoliths and foraminifera were deposited two to three times more rapidly during interglaciations than glaciations; in converse proportions, coarse and fine terrigenous detritus was preferentially rafted into the northeast Atlantic Ocean during glaciations. The absence of coccoliths in polar water accounts for the existence of glacial coccolith-barren zones.

At the scale of local sediment redistribution (related to siting factors), fine coccolith carbonate is most easily redistributed. The absolute abundance of all coarse and fine components increases at higher net sedimentation rates, but fine carbonate increases most rapidly.

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GSA Memoirs

Investigation of Late Quaternary Paleoceanography and Paleoclimatology

R. M. Cune
R. M. Cune
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J. D. Hays
J. D. Hays
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Geological Society of America
Volume
145
ISBN print:
9780813711454
Publication date:
January 01, 1976

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