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Título

When Ice Sheets Hit the Brakes: How Carbon Cycle Slowed the Big Freeze 34 Million Years Ago

Texto do resumo

The Eocene-Oligocene Transition (EOT), approximately 34 million years ago (Ma), represents one of the most significant climate shifts in Earth's history, marked by the rapid expansion of the East Antarctic Ice Sheet (EAIS). This study aims to elucidate the impact of ice sheet dynamics on the global carbon cycle during the EOT by utilizing multi-proxy evidence. Our research was conducted at a shallow shelf location in the United States Gulf Costal Plain and employed various proxies, including sediment core analysis, microfossil counting data, elemental and isotopic measurements, and lipid biomarker assessments. We also used an Earth System model to simulate the observed changes. The study identifies a marked drop in sea levels of approximately 40 meters coinciding with the onset of the EOT around 34.4 Ma. This regression is linked to increased organic flux and extensive EAIS glaciation, which contributed to significant biogeochemical feedback mechanisms. The initial sea level fall delivered a pulse of organic carbon to the oceans, driving observed deep ocean carbonate dissolution. This process acted as a transient negative feedback to climate cooling, demonstrating the complex interplay between ice sheet expansion and global carbon cycling. Our findings provide critical insights into the feedback mechanisms that influenced the EOT, emphasizing the role of ice sheets in modulating Earth's carbon reservoirs and climate system. Understanding these geological processes is vital for predicting future climate dynamics in the context of contemporary ice sheet melt and global carbon cycle disturbances. Integrating geological proxies with climate models is essential for unraveling the intricate relationships between ice sheets, sea levels, and carbon cycling.

Palavras Chave

Eocene-Oligocene Transition; East Antarctic Ice Sheet; global carbon cycle; sea level fall; biogeochemical feedbacks