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Research at St Andrews

Rosanna Greenop


Research overview

Current Research

I am currently working on a NERC-funded project to determine changes in the surface water radiocarbon age for the North Atlantic over the past 50,000 years. Knowing the radiocarbon content of the surface ocean (or radiocarbon reservoir age) is important for both inferring past changes in ventilation rates and determining the timing of past changes in climate and ocean circulation.

Changes in radiocarbon reservoir age will be determined using independent age models constructed from tephrochronology and 230Th normalised sediment flux rates (to estimate sedimentation rate changes). This information, alongside additional measurements of benthic radiocarbon ages will then be used to infer past changes in the Atlantic Meridonial overturning circulation- an important component of our climate system.

Research Background

My PhD project conducted at the University of Southampton was focused on using the boron isotope proxy to investigate the relationship between atmospheric CO2 and Antarctic ice sheet decline during the Cenozoic. Results of ice sheet modelling experiments suggest that once ice sheets have grown, due to a powerful hysteresis effect, they are inherently stable and consequently high levels of CO2 are needed in order to initiate deglaciation. Growing evidence from a number of palaeorecords suggest that the West and East Antarctic ice sheets may have retreated during warm intervals of the Cenozoic. However, the atmospheric CO2 rise that would be expected to accompany intervals of ice sheet retreat have not been seen in reconstructions of palaeo-CO2.

The primary objective of the project was to reconstruct CO2 during intervals of climate warming in the Miocene. In order to determine the evolution of CO2, changes in the boron isotope composition of seawater (δ11Bsw) and foraminifera ecology were also investigated through time.

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