The Atlantic Meridional Overturning Circulation (AMOC) is a crucial component of global climate and marine ecosystems. It plays a significant role in redistributing heat and salt in the ocean, interacting with the atmosphere, and ventilating the ocean interior. However, there is still much uncertainty surrounding the timing and cause of the initiation and evolution of this system.
Researchers from the Institute of Earth Environment of the Chinese Academy of Sciences (IEECAS), the University of Hong Kong, and the University of Southampton have recently made groundbreaking discoveries regarding the emergence of the modern-like AMOC. Their study, published in Nature Geoscience on Oct. 16, utilized a novel method of tracing oxygenation using microbial biomarkers.
The research team focused on microbial source indicators, specifically glycerol dialkyl glycerol tetraethers (GDGTs), that can provide insights into the contribution of non-Thaumarchaeota archaea/bacteria in past oceanic environments. In geological samples, the abundance of non-Thaumarchaeota can indicate the oxygenation status of the ocean. This method was instrumental in evaluating the evolution of early AMOC.
The team’s findings revealed that the oxygenation of AMOC-feed waters decreased and reached its lowest point towards the end of the Eocene period, approximately 34 million years ago (Ma). However, with the initiation of large-scale Antarctic glaciation, which also coincided with the Eocene-Oligocene transition (EOT), AMOC-feed waters experienced improved oxygenation. This marked the onset of a more modern-like AMOC, suggesting a causal link between Antarctic glaciation and the emergence of this circulation system.
The timing and cause of the inception of Cenozoic AMOC have long been a subject of scientific inquiry. The team’s findings provide valuable insights into the mechanisms driving the AMOC. The study suggests that both vertical mixing and upwelling driven by Southern Ocean winds are crucial for sustaining the modern AMOC. This understanding advances our knowledge of the role of climatic events, such as Antarctic glaciation, in shaping the Earth’s climate system.
The research conducted by the IEECAS, the University of Hong Kong, and the University of Southampton sheds new light on the emergence of the modern-like AMOC. By utilizing microbial source indicators to trace oxygenation, the study offers a fresh perspective on the changes that occurred during the Eocene-Oligocene transition. The findings underscore the complex interactions between the ocean, atmosphere, and climate, emphasizing the need for further research in this field.
As the understanding of the AMOC continues to evolve, researchers will undoubtedly build upon these recent findings to deepen our knowledge of the Earth’s climate system. Exploring the intricate connections between glaciation events, oceanic circulation, and climate change will contribute to our understanding of past, present, and future climate dynamics. The study’s insights into the emergence of the AMOC open new avenues for investigating the mechanisms that shape our planet’s climate.