Stochastic resonance in the North Atlantic

Large, abrupt changes between warm and cold modes of North Atlantic climate exhibit spectral power at similar to 1500 years, yet some climatic changes were linked to outburst floods and other events that are unlikely to have been truly periodic. We hypothesize that a weak periodic forcing has combin ed with "noise" from ice sheet-related events to cause the observed mode sw itches. This stochastic resonance hypothesis predicts a recurrence pattern between warmings that is distinct from the predictions of simple periodic a nd stochastic models and at least some other models. The ice isotopic data from central Greenland ice cores are consistent with the stochastic resonan ce hypothesis but not with other models we have tested. We thus support arg uments for the existence of a periodicity of similar to 1500 years in the N orth Atlantic climate system and for the importance of ice sheet events in forcing North Atlantic changes.