1. Heidelberg Academy of Sciences, c/o Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
2. Potsdam Institute for Climate Impact Research, PO Box 601203, 14412 Potsdam, Germany
3. Alfred Wegener Institute for Polar and Marine Research, Bussestrasse 24, 27570 Bremerhaven, Germany
4. Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany

Correspondence to: Holger Braun¹ Correspondence and requests for materials should be addressed to H.B. (Email: holger.braun@iup.uni-heidelberg.de).

Abstract

Many palaeoclimate records from the North Atlantic region show a pattern of rapid climate oscillations, the so-called Dansgaard–Oeschger events, with a quasi-periodicity of 1,470 years for the late glacial period^{1, 2, 3, 4, 5, 6}. Various hypotheses have been suggested to explain these rapid temperature shifts, including internal oscillations in the climate system and external forcing, possibly from the Sun⁷. But whereas pronounced solar cycles of 87 and 210 years are well known^{8, 9, 10, 11, 12}, a 1,470-year solar cycle has not been detected⁸. Here we show that an intermediate-complexity climate model with glacial climate conditions simulates rapid climate shifts similar to the Dansgaard–Oeschger events with a spacing of 1,470 years when forced by periodic freshwater input into the North Atlantic Ocean in cycles of 87 and 210 years. We attribute the robust 1,470-year response time to the superposition of the two shorter cycles, together with strongly nonlinear dynamics and the long characteristic timescale of the thermohaline circulation. For Holocene conditions, similar events do not occur. We conclude that the glacial 1,470-year climate cycles could have been triggered by solar forcing despite the absence of a 1,470-year solar cycle.

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