The cold event 8200 years ago documented in oxygen isotope records of precipitation in Europe and Greenland

Climate Dynamics, Vol. 14, p. 73-81, 1998 

U. von Grafenstein, J. Jouzel
Laboratoire de Modélisation du Climat et de l'Environnement, DSM, CEA Saclay, Ormes de Merisier, F-91191 Gif-sur-Yvette, France.
H. Erlenkeuser
Leibniz-Labor für Altersbestimmung und Isotopenforschung der Christian-Albrechts-Universität zu Kiel (CAU), Max-Eyth-Strasse 11, D-24118 Kiel, Germany.
J. Müller
Lehrstuhl für Allgemeine, Angewandte und Ingenieur-Geologie, Technische Universität München, D-85747 Garching, Germany.
S. Johnsen
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.

Stable oxygen isotope ratios of ostracod valves in Late Glacial and Holocene sediments of core AS 92-5 from deep lake Ammersee (southern Germany) reflect variations of mean oxygen isotope ratios in past atmospheric precipitation. The record reconfirms the strong similarity of climate evolution in Europe and Greenland during the last deglaciation. For the first time in Europe, we find a 200-year-long negative d18O-excursion, which is contemporaneous with the strongest negative d18O-excursion in the Greenland ice around 8.2 ky before present. The 8.2 ky isotopic event on both sides of the North Atlantic ocean is interpreted as a cold period, most probably induced by a perturbation of the North Atlantic thermohaline circulation. We discuss two possible triggering mechanisms: (1) weak forcing (as proposed by Alley et al.), and (2) forcing by a strong and sudden freshwater pulse from the collapse of the Hudson Ice Dome.