Quaternary Science Reviews, August 10, 2012, Vol.48, p.43(11)
To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.quascirev.2012.06.006 Byline: Lukas Jonkers (a), Maarten A. Prins (b), Matthias Moros (c)(d), Gert Jan Weltje (e), Simon R. Troelstra (b), Geert-Jan A. Brummer (a)(b) Abstract: Rapid climatic switches during marine isotope stage 3 (29-59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of icebergs and sea ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for ice rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and [delta].sup.18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the ice-rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes. Author Affiliation: (a) Royal Netherlands Institute for Sea Research, Dept. Marine Geology, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands (b) VU University Amsterdam, Faculty of Earth and Life Sciences, Dept. Earth Sciences, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands (c) Leibniz Institute for Baltic Sea Research, Warnemunde, Seestra[sz]e 15, D-18119 Rostock, Germany (d) Bjerknes Centre for Climate Research, Allegaten 55, NO-5007 Bergen, Norway (e) Delft University of Technology, Geotechnology Department, PO Box 5048, 2600 GA Delft, The Netherlands Article History: Received 25 June 2011; Revised 3 June 2012; Accepted 8 June 2012
Ocean Circulation -- Analysis ; Proxy -- Analysis ; Sediments (Geology) -- Analysis ; Sea Ice -- Analysis ; Universities And Colleges -- Analysis
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