The duration of the Bølling-Allerød period (Greenland Interstadial 1) in the GRIP ice core

Annals of Glaciology, Vol. 42, Number 1, pp. 337-344(8), 2005

I.K. Seierstad, S.J. Johnsen and B.M. Vinther
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
J. Olsen
Department of Physics and Astronomy, University of Århus, Ny Munkegade, DK-8000 Århus, Denmark.

A new dating of the Bølling-Allerød period (Greenland Interstadial event 1) in the GRIP ice core is presented. Newly measured profiles of δD and δ18O, as well as existing profiles of Ca2+, NH4+, dust and NO3-, have been used for the dating. As seasonal variations can be observed in all six components, it was possible to simultaneously count annual layers in the profiles in order to obtain a multi-parameter dating. The new data presented in this study include a total of 36.85 m of stable-isotope profiles of 1 cm resolution from five sections of the Bølling-Allerød period in the GRIP ice core. The annual-layer counting suggests a duration of the complete Bølling-Allerød period, as revealed in the GRIP ice core, of 1627 ± 52 years. This estimate contrasts with an earlier finding from the same GRIP ice core, where the Bølling-Allerød was found to span 2168 years (Hammer, in press). This estimate was based on layer counting, using dust concentrations only.