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Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.


Fig. 1. Idealized North Atlantic surface (red arrows) and deep water (blue arrow) circulation during MIS 3 stadial events.
Fig. 1. Idealized North Atlantic surface (red arrows) and deep water (blue arrow) circulation during MIS 3 stadial events.

Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

Nature
Vol. 443, No. 7111, pp.561-564, doi:10.1038/nature05121, 5 Oct 2006.

Matthew W. Schmidt1,2, Maryline J. Vautravers3,4, and Howard J. Spero1

1 Department of Geology, University of California, Davis, California 95616, USA.
2 Present address: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
3 Hadley Centre for Climate Prediction and Research, Met Office, Exeter, UK.
4 Present address: British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK
ABSTRACT:
Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean- atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratiomeasurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.
Download data from the WDC Paleo archive:
North Atlantic SST and Salinity Reconstructions, Text or Excel format.

To read or view the full study, please visit the Nature website.
It was published in Nature, Vol. 443, No. 7111, pp.561-564, doi:10.1038/nature05121, 5 Oct 2006.
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