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Synchronized Terrestrial-Atmospheric Deglacial Records Around the North Atlantic
1S. Bjorck and T. L. Rasmussen, Geological Institute, University of Copenhagen, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark. B. Kromer, Heidelberg Academy of Sciences, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany. S. Johnsen, Department of Geophysics, Niels Bohr Institute, Rockefeller Komplekset, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark, and Science Institute, Dunhage 3, Is-107, Reykjavik, Iceland. O. Bennike, GEUS, Thoravej 8, DK-2400 Copenhagen, Denmark. D. Hammarlund, G. Lemdahl, B. Wohlfarth, Department of Quaternary Geology, Lund University, Tornavagen 13, S-22363 Lund, Sweden. G. Possnert, Tandem Laboratory, Uppsala University, Box 533, S-75121 Uppsala, Sweden. C. U. Hammer, Department of Geophysics, Niels Bohr Institute, Rockefeller Komplekset, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark. M. Spurk, Institut fur Botanik, Universitat Hohenheim, Garbenstrasse 30, D-70593 Stuttgart, Germany.
Abstract:
On the basis of synchronization of three carbon-14 (14C)-dated lacustrine sequences from Sweden with tree ring and ice core records, the absolute age of the Younger Dryas-Preboreal climatic shift was determined to be 11,450 to 11,390 +/- 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising Delta14C values, is evident in all records and indicates an ocean ventilation change. This cooling is similar to earlier deglacial coolings, and box-model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the North Atlantic heat conveyor, although the Younger Dryas may have begun as an anomalous meltwater event.