Abreu, Lúcia de

Hillaire-Marcel, Claude

Hodell, David A.

Vernal, A. de

Voelker, Antje H. L.

Laboratório Nacional de Energia e Geologia Repository

Overturning Circulation in the North Atlantic Ocean during Marine Isotope Stage 11c

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2010 AGU Fall Meeting You may print by clicking on this Print  button. To return to the previous page, close thisbrowser window or click the 'X' button in the top right corner of the page. ID# PP41B-1623Location: Poster Hall (Moscone South)Time of Presentation: Dec 16 8:00 AM - 12:20 PM Overturning Circulation in the North Atlantic Ocean During Marine Isotope Stage 11cA. H. Voelker1, 2; L. de Abreu1; C. Hillaire-Marcel3; A. de Vernal3; D. A. Hodell41. Unid. Geologia Marinha, LNEG, Amadora, Portugal.2. CIMAR Associated Laboratory, CIIMAR, Porto, Portugal.3. GEOTOP, UQAM, Montreal, QC, Canada.4. Dept. of Earth Sciences, Univ. Cambridge, Cambridge, United Kingdom. With a duration of 28 ky Marine Isotope Stage (MIS) 11c was the longest lasting interglacial ofthe last 1 My. It had eccentricity values similar to the Holocene and is therefore often used forcomparison between these two interglacials. Here we combine new benthic and plankticforaminifer proxy records from sites drilled during IODP Exp. 303 and 306 with published datato map hydrographic conditions in the surface and deep waters of the North Atlantic Ocean andthus the state of the overturning circulation. The combined sites cover water depths from 1145to 4595 m and are from key positions that allow to monitor changes along the major surfaceand deep-water current pathways.Along the Gulf Stream, North Atlantic Drift and Portugal Current, surface water conditions weresimilar between 426 and 398 ka and surface and thermocline waters experienced only minorvariations throughout the interglacial interval. The G. inflata Mg/ Ca records of IODP Site U1313at 41°N shows, however, that the winter mixed layer started to cool already after 404 ka, i.e. 6ka earlier than the demise of the interglacial. In comparison to the open North Atlantic surfacewaters, sites in the Labrador Sea and under the influence of the polar West Greenland (IODPSite U1305) and Labrador Currents (IODP Site U1303) recorded millennial-scale oscillationsand surface waters here were less well ventilated until 408 ka. Similar oscillations were alsodocumented at IODP Site U1308 by the polar species N. pachyderma (s), which at this sitemost likely reflects winter conditions, hinting at a potential signal transfer from the Labrador Seathrough the subpolar mode water.In the deep ocean oxygen isotope values were at a similar level for the sites bathed by upperand lower North Atlantic Deep Water (NADW) throughout MIS 11c. Only IODP Site U1305 from3518 m water depth off southern Greenland and recording the Denmark Strait Overflow Water(DSOW) reveals slightly heavier values pointing to a cold DSOW. Ventilation at the differentdeep water levels, however, and thus convection depth or strength varied. Throughout MIS 11c,the best ventilated water mass was the lower NADW and like today ventilation was slightlybetter in the western than the eastern basin. Nevertheless, DSOW at site U1305 was wellventilated only after 407 ka, so that the good ventilation of the lower NADW must derive fromthe Iceland Scotland Overflow Water pointing to deep convection in the Norwegian Sea. Theupper NADW was well ventilated only after 418 ka, potentially as a result of the variable surfacewater conditions in the Labrador Sea that could have inhibited deep convection. Below 4000 mventilation also increased only after 418 ka but these levels still experienced periods with astronger Antarctic Bottom Water influence until 409 ka. Overall the combined data reveals thatthe North Atlantic overturning circulation was at its strongest level between 409 and 400 kacontemporary with highest sea level. The colder winter mixed layer temperatures at site U1313during this period could actually indicate a better preconditioning for the deep convection.Contact InformationAntje H. Voelker, Amadora, Portugal, 2610-143, click here to send an emailScholarOne Abstracts® (patent #7,257,767 and #7,263,655). © ScholarOne, Inc., 2010. All Rights Reserved.ScholarOne Abstracts and ScholarOne are registered trademarks of ScholarOne, Inc.Terms and Conditions of Use

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Overturning Circulation in the North Atlantic Ocean during Marine Isotope Stage 11c

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