Summary: The Recurrence Time of Dansgaard­Oeschger Events and Limits on the Possible
Periodic Component
PETER D. DITLEVSEN, MIKKEL S. KRISTENSEN, AND KATRINE K. ANDERSEN
The Niels Bohr Institute, Department of Geophysics, University of Copenhagen, Copenhagen, Denmark
(Manuscript received 15 April 2004, in final form 2 December 2004)
ABSTRACT
By comparing the high-resolution isotopic records from the Greenland Ice Core Project (GRIP) and the
North Greenland Ice Core Project (NGRIP) ice cores, the common climate signal in the records has been
approximately separated from local noise. From this, an objective criterion for defining Dansgaard­
Oeschger (DO) events is achieved. The analysis identifies several additional short-lasting events, increasing
the total number of DO events to 27 in the period 12­90 kyr before present (BP). The quasi-regular
occurrence of the DO events could indicate a stochastic or coherent resonance mechanism governing their
origin. From the distribution of waiting times, a statistical upper bound on the strength of a possible periodic
forcing is obtained. This finding indicates that the climate shifts are purely noise driven with no underlying
periodicity.
1. Introduction
Abrupt temperature shifts between cold (stadial)
states and warm (interstadial) states [Dansgaard­
Oeschger (DO) events] are observed in the Greenland
ice core isotope records (Dansgaard et al. 1993;

Source: Andersen, Katrine Krogh - Niels Bohr Institute for Astronomy, Physics and Geophysics, Københavns Universitets

Collections: Geosciences; Environmental Sciences and Ecology