07 Nov 2023
 | 07 Nov 2023
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

The Temporal Phasing of Rapid Dansgaard–Oeschger Warming Events Cannot Be Reliably Determined

John Slattery, Louise C. Sime, Francesco Muschitiello, and Keno Riechers

Abstract. Dansgaard–Oeschger (DO) warming events occurred throughout the last glacial period. Greenland ice cores show a rapid warming during each stadial to interstadial transition, alongside abrupt loss of sea ice and major reorganisation of the atmospheric circulation. Other records also indicate simultaneous abrupt changes to the oceanic circulation. Recently, an advanced Bayesian ramp fitting method has been developed and used to investigate time lags between transitions in these different climate elements, with a view to determining the relative order of these changes. Here, we subject this method to a critical review. Using ice core data, climate model output, and carefully synthesised data representing DO warming events, we demonstrate that the method suffers from noise-induced bias of up to 15 years. This bias means that the method will tend to yield transition onsets that are too early, and we find that the estimated timings of noisier transitions are more strongly biased. Further investigation of DO warming event records in climate models and ice core data reveals that the bias is on the same order of magnitude as potential timing differences between the abrupt transitions of different climate elements. Additionally, we find that higher-resolution records would not reduce this bias. We conclude that time lags of less than 20 years cannot be reliably detected, as we cannot exclude the possibility that they result solely from the bias. This prevents the unambiguous determination of the temporal phasing of DO warming events.

John Slattery et al.

Status: open (until 20 Jan 2024)

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John Slattery et al.

Model code and software

DO_Temporal_Phasing John Slattery

John Slattery et al.


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Short summary
Dansgaard–Oeschger events are a series of past abrupt climate change events, during which the atmosphere, sea ice, and ocean in the North Atlantic underwent rapid changes. One current topic of interest is the order in which these different changes occurred, which remains unknown. In this work, we find that the current best method used to investigate this topic is subject to substantial bias. This implies that it is not possible to reliably determine the order of the different changes.