Timing of meltwater pulse 1a and climate responses to meltwater injections

Paleoceanography, Vol. 21, PA4103, doi:10.1029/2006PA001340, 2006

J.D. Stanford, E.J. Rohling, S.E. Hunter and A.P. Roberts
National Oceanography Centre, University of Southampton, Southampton, UK.
S.O. Rasmussen
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
E. Bard
Collège de France, Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635 and Université d'Aix-Marseille III, Europôle de l'Arbois, Aix-en-Provence, France.
J. McManus
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA.
R.G. Fairbanks
Lamont-Doherty Earth Observatory and Department of Earth and Environmental Science, Columbia University, Palisades, New York, USA.

ABSTRACT.
The temporal relationship between meltwater pulse 1a (mwp-1a) and the climate history of the last deglaciation remains a subject of debate. By combining the Greenland Ice Core Project δ¹⁸O ice core record on the new Greenland ice core chronology 2005 timescale with the U/Th-dated Barbados coral record, we conclusively derive that mwp-1a did not coincide with the sharp Bølling warming but instead with the abrupt cooling of the Older Dryas. To evaluate whether there is a relationship between meltwater injections, North Atlantic Deep Water (NADW) formation, and climate change, we present a high-resolution record of NADW flow intensity from Eirik Drift through the last deglaciation. It indicates only a relatively minor 200-year weakening of NADW flow, coincident with mwp-1a. Our compilation of records also indicates that during Heinrich event 1 and the Younger Dryas there were no discernible sea level rises, and yet these periods were characterized by intense NADW slowdowns/shutdowns. Clearly, deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition. Instead, our results emphasize that the location of meltwater pulses may be more important, with NADW formation being particularly sensitive to surface freshening in the Arctic/Nordic Seas.