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Tuesday, June 28, 2011

Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2, Paleoceanography, 26, PA2101, doi: 10.1029/2011PA002114, by Marcus Gutjahr & Jörg Lippold

Paleoceanography, 26 (2011) PA2101; doi: 10.1029/2011PA002114
Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2
Key Points
  • North Atlantic Deep Water ventilated the deep N Atlantic during early MIS 2
  • Deep and intermediate water changes preceded Heinrich event 2
  • Heinrich event 2 was the result and not the cause for AMOC changes
Marcus Gutjahr 
Bristol Isotope Group, Department of Earth Sciences, University of Bristol, Bristol, UK
Jörg Lippold
Heidelberg Academy of Sciences, Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany


The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the Northern Hemisphere climate system. Significant interest went into the question of how excessive freshwater input through melting of continental ice can affect its overturning vigor and, hence, heat supply, to higher northern latitudes. Such forcing can be tested by investigating its behavior during extreme iceberg discharge events into the open North Atlantic during the last glacial period, the so-called Heinrich events (HE). Here we present neodymium (Nd) isotope compositions of past seawater, a sensitive chemical water mass tag, extracted from sediments of Ocean Drilling Program Site 1063 in the western North Atlantic (Bermuda Rise), covering the period surrounding HE 2, the Last Glacial Maximum, and the early deglaciation. These data are compared with a record of the kinematic circulation tracer (231Pa/230Th)xs extracted from the same sediment core. Both tracers indicate significant circulation changes preceding intense ice rafting during HE 2 by almost 2 kyr. Moreover, the Nd isotope record suggests the presence of deeply ventilating North Atlantic Deep Water early during Marine Isotope Stage 2 until it was replaced by Southern Source Water at ∼27 ka. The early switch to high (Pa/Th)xs and radiogenic ɛNd in relation to intensified ice rafting during HE 2 suggests that ice rafting into the open North Atlantic during major HE 2 was preceded by an early change of the AMOC. This opens the possibility that variations in AMOC contributed to or even triggered the ice sheet instability rather than merely responding to it.
Received 10 January 2011; accepted 31 May 2011; published 25 June 2011.
Citation: Gutjahr, M., and J. Lippold (2011), Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2Paleoceanography26, PA2101, doi: 10.1029/2011PA002114.

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