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Presence of millennial-scale climatic cycles during the middle Eocene climatic optimum
Fox, Maddie Slawson, Jake Plink-Bjorklund, Piret
Fox, Maddie
Slawson, Jake
Plink-Bjorklund, Piret
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2024-04
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The Eocene epoch (55-34 million years ago) witnessed a transition from a greenhouse to an icehouse climate, marked by rapid, extreme global warming events known as hyperthermals. These events, triggered by spikes in atmospheric CO2 concentration, offer insights into Earth's response to high-magnitude CO2 changes, crucial for comprehending modern climate shifts. One such event, the Middle Eocene Climatic Optimum, was a major climatic shift lasting approximately 500 kyr. Orbital forcers, most notably variations in the amount of solar irradiance reaching Earth, are believed to explain many of the observed climatic variations in both this epoch and others. Changes in orbital patterns are widely believed to explain cyclicities on the 20,000 to 100,000 year scale, while changes in solar irradiance have effects on the sub-1,000 year scale. However, little work has been done to understand the influence of orbital cycles of periods between these, in the millennial range. This study investigates Middle Eocene Climatic Optimum temperature proxies from Ocean Drilling Program sites, revealing a statistically significant 2500 ± 250-year cycle, identified as the Hallstatt cycle. Linked to a spin-orbit coupling of Jovian planets, this astronomical origin suggests that solar system chaos during this period played a role in abnormal climate patterns. Understanding such complexities enhances predictions about current and future climates by acknowledging the substantial influence of external factors on climate dynamics.
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