Reduced North Atlantic Deep Water flux to the glacial Southern Ocean inferred from neodymium isotope ratios

Publication Type  Journal Article
Year of Publication  2000
Authors  Rutberg, R. L.; Hemming, S. R.; Goldstein, S. L.
Journal Title  Nature
Volume  405
Issue  6789
Pages  935-938
Journal Date  Jun 22
ISBN Number  0028-0836
Accession Number  ISI:000087732700046
Key Words  circulation; sea; delta-c-13; seawater; nd; sediment; stage-2; climate; vostok; carbon

The global circulation of the oceans and the atmosphere transports heat around the Earth. Broecker and Denton(1) suggested that changes in the global ocean circulation might have triggered or enhanced the glacial-interglacial cycles. But proxy data for past circulation taken from sediment cores in the South Atlantic Ocean have yielded conflicting interpretations of ocean circulation in glacial times-delta(13)C variations in benthic foraminifera(2-6) support the idea of a glacial weakening or shutdown of North Atlantic Deep Water production, whereas other proxies, such as Cd/Ca, Ba/Ca and Pa-231/Th-230 ratios, show little change from the Last Glacial Maximum to the Holocene epoch(7-9). Here we report neodymium isotope ratios from the dispersed Fe-Mn oxide component of two southeast Atlantic sediment cores. Both cores show variations that tend towards North Atlantic signatures during the warm marine isotope stages 1 and 3, whereas for the full glacial stages 2 and 4 they are closer to Pacific Ocean signatures. We conclude that the export of North Atlantic Deep Water to the Southern Ocean has resembled present-day conditions during the warm climate intervals, but was reduced during the cold stages. An increase in biological productivity may explain the various proxy data during the times of reduced North Atlantic Deep Water export.


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