Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles

Schmidt, M. W. and Vautravers, M. J. and Spero, H. J. (2006) Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles. Nature, 443. 561-564; doi:10.1038/nature05121. DOI 10.1038/nature05121

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Abstract

Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard–Oeschger cycles1, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux2. 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 climate3, 4, 5. 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 ratio measurements 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 cycle6 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.

Item Type: Article
Uncontrolled Keywords: 2006 AREP IA52 2006 P
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Nature
Volume: 443
Page Range: 561-564; doi:10.1038/nature05121
Identification Number: 10.1038/nature05121
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:03
Last Modified: 23 Jul 2013 10:08
URI: http://eprints.esc.cam.ac.uk/id/eprint/661

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