Surface ocean cooling in the Eocene North Atlantic coincides with declining atmospheric CO2

Abstract

The Eocene (56–34 million years ago) is characterised by declining sea surface temperatures (SSTs) in the low latitudes (~4°C) and high southern latitudes (~8-11°C), in accord with decreasing CO2 estimates. However, in the mid-to-high northern latitudes there is no evidence for surface water cooling, suggesting thermal decoupling between northern and southern hemispheres and
additional non-CO2 controls. To explore this further, we present a multi-proxy (Mg/Ca, δ¹⁸O, TEX₈₆) SST record from Bass River in the western North Atlantic. Our compiled multi-proxy SST record confirms a net decline in SSTs (~4°C) between the early Eocene Climatic Optimum (53.3-49.1 Ma) and mid-Eocene (~44-41 Ma), supporting declining atmospheric CO2 as the primary mechanism of Eocene cooling. However, from the mid-Eocene onwards, east-west North Atlantic temperature gradients exhibit different trends, which we attribute to incursion of warmer waters into the eastern North Atlantic and inception of Northern Component Water across the early-middle Eocene transition.

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Identifiers

ORCID for Gordon Inglis: orcid.org/0000-0002-0032-4668

ORCID for David Evans: orcid.org/0000-0002-8685-671X

ORCID for Richard G. Stockey: orcid.org/0000-0001-5541-7987

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