Ni

EARTH
SCIENCES

Yunyan Ni

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E-mail: Yunyan.Ni@bristol.ac.uk
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	PhD title: Atmospheric Carbon Dioxide Variation in Quaternary Climate Cycles Funding: ORS and Univeristy Scholarship Supervisors: Dr.Tim Elliott and Prof. Paul Pearson (Cardiff University) Academic career: 1995-1999: BSc Geology, Beijing University (China) 1999-2002: MSc Geology, Institute of Geology and Geophysics, Chinese Academy of Sciences (China)

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Project Summary:

We know from studies of air bubbles trapped in ice cores that carbon dioxide levels in the Earth's atmosphere have varied in a rhythmic way overthe last 400,000 years, and that these variations are closely linked to the glacial-interglacial climate cycle. This project aims to use marine sediment cores to extend this record back through time, beyond the age range covered by the ice core record. The principle technique will be boron isotope analysis of planktonic foraminifer shells which, it has previously been argued, reflects the pH of calcification, which in turn is largely controlled by atmospheric CO₂ (an acidic gas).
The technique will be developed using Thermal Ionization Mass Spectrometry. Samples from various sites and ages will be analyzed. Samples from the last few climate cycles will be studied to determine how accurately the method constructs known variations, then the method will be applied further back in time. Of particular interest is the "mid-Pleistocene revolution", about 900,000 years ago, when predominantly 40 kyr climate cycles gave way to the present 100 kyr dominance. I intend to investigate the hypothesis that regular carbon dioxide variations also occurred before this time. The data will
be used to study variations in the global carbon cycle on time scales of Milankovitch (orbital) variation.