Ocean circulation during Eocene extreme "greenhouse" climatic warmth

• Main Author: Cameron, Adele Jane
• Format: Thesis
• Language: unknown
• Published: 2016
• Subjects: Newfoundland; Southern Ocean; Labrador Sea; North Atlantic Deep Water; North Atlantic
• Online Access: https://oro.open.ac.uk/63173/; https://oro.open.ac.uk/63173/1/699820%20%281%29.pdf; https://doi.org/10.21954/ou.ro.0000f6c5

The Early Eocene (≈ 47-56 Ma) 'greenhouse' climate represented the warmest climatic conditions witnessed in the last 90 million years, with peak Eocene warmth (the Early Eocene Climatic optimum, EECO) occurring around 50-52 Ma (Sexton et al. 2006; Bijl et al. 2009; Zachos et al. 2008; Littler et al. 2014) with subsequent global cooling thereafter (Sexton et al. 2006; Zachos et al. 2008). Ocean circulation plays a critical role in redistributing thermal energy across the planet and providing ventilation to the deepest parts of the ocean. Understanding how it may have operated in a globally warm world with little equator-to-pole gradients is paramount to understanding how it may respond to increasing temperatures today. The prevailing view of the early Eocene ocean was that deep-water formation was confined to the Southern Ocean, with little or no deep-water formation in the North Atlantic, unlike today. This study explores whether there is evidence for deep-water formation in the high latitude North Atlantic during the extreme climatic warmth of the early Eocene and its stability across transient climatic excursions. It also explores the strength and vigour of ocean circulation and whether this was influenced by the global decline in temperature following early Eocene peak-warmth. It utilises the neodymium isotopic signature of fossilised fish teeth (εNd) that is widely utilised to trace the movements of deep-water masses and can be used to reconstruct paleo-oceanic circulation along with detrital εNd that is an indicator of sediment provenance. It combines these with fish tooth rare earth element concentrations and sediment core XRF. Four key locations are utilised. Two on the Newfoundland margin in the West North Atlantic, and one from the high North Atlantic in the Labrador Sea, both ideal locations to identify the potential outputs of North Atlantic deep-water formation. The fourth site is Demerara Rise in the Equatorial Atlantic, chosen to monitor changes in the dominant source of deep-water sources from the ...