Contrasting dynamics of past climate states and critical transitions via dimensional analysis
Résumé
While major climate transitions in the past can be clearly identified, our understanding of the underlying mechanisms and timescales remains limited. To address this, we conducted a dimensional analysis of benthic stable isotope records across various timescales to explore how Cenozoic climatic fluctuations relate to changes in feedback mechanisms. Our analysis reveals that climate responses to orbital forcing differ significantly between warmer and colder periods. Specifically, during the Icehouse state, a high number of feedback mechanisms predominated at obliquity and eccentricity timescales, whereas, in the Warmhouse and Hothouse states, feedback mechanisms were more prominent at precession timescales. During the Coolhouse state, the number of active feedbacks was low, and no single timescale dominated. Additionally, coupling between climate signals affecting oxygen and carbon isotope records was notably high only during the Icehouse state and low or absent in other states. We also observed that during the Paleocene-Eocene Thermal Maximum (PETM), there was an unusually high number of active feedbacks and very high coupling across all timescales, indicating a significant perturbation of the climate system. In conclusion, our findings suggest that a singular model of interconnected feedbacks may not adequately capture Cenozoic paleoclimate variability. Instead, different numbers of active feedbacks and varying levels of coupling, operating over different timescales, influenced the stability and variability of each climate state.
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