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

• Main Authors: Slattery, John, Sime, Louise C., Muschitiello, Francesco, Riechers, Keno
• Format: Text
• Language: English
• Published: 2023
• Subjects: Greenland; Greenland ice cores; ice core; Sea ice
• Online Access: https://doi.org/10.5194/egusphere-2023-2496; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2496/

Dansgaard–Oeschger (DO) warming events oc curred throughout the last glacial period. Greenland ice cores show a rapid warming during each stadial to interstadial tran sition, alongside abrupt loss of sea ice and major reorgani sation of the atmospheric circulation. Other records also in dicate simultaneous abrupt changes to the oceanic circula tion. 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 repre senting 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 nois ier 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 deter mination of the temporal phasing of DO warming events.