Eocene CO2 on orbital to million year timescales

Abstract

The early Eocene features distinctive coupling between biogeochemical cycles and climate, raising fundamental questions about Earth system functioning during major climate transitions and on orbital timescales. For instance, the transition to peak Eocene warmth is ushered in by a major shift in redox conditions and deep ocean circulation, while orbitally-paced hyperthermal events are associated with substantial carbon injections of uncertain origin.  CO2 change is thought to play a key role in these events, yet despite recent progress, resolution is still lacking for most shorter time intervals.  Here we present new, high-resolution boron isotope data from both benthic and planktic foraminifera that shed new light on Eocene carbon cycling. Using new approaches for conversion of boron isotope data to pH and CO2, we improve estimates of absolute CO2 concentrations and the change in CO2 over key events.  Our data demonstrate a pervasive link between CO2 and climate in the Eocene hothouse over a range of timescales and provide novel constraints on carbon sources and climate sensitivity.