James W. B. Rae

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Contact Details: Postal address: Dept. of Earth Sciences University of Bristol Wills Memorial Building Queen's Road BRISTOL BS8 1RJ Office: Wills Building Room N (behind Great Hall) E mail address: james.rae (at) bristol.ac.uk Telephone: +44 (0)117 33 15197 Fax: +44 (0)117 925 3385

Research Interests:

Earth's climate plays a crucial role in how our planet has evolved in the past and how it will evolve in the future. I am interested in novel geochemical methods of tracing the diverse processes that control climate. I aim to develop an in-depth understanding of how such tracers work, in order to be able to exploit their true potential in answering fundamental questions about the earth's environment.

PhD Project:

"Boron isotopes in benthic foraminifera: calibration, calcification and glacial-interglacial CO₂"

Supervisors:

The boron isotope composition (&delta¹¹B) of tiny marine shells (foraminifera) has long been considered one of the most promising tools for tracking past climate change. Excitement about this technique stems from its ability to track the CO₂ system in seawater. This may allow us to:
1) Track past levels of atmospheric CO₂, and thus reconstruct the relationship between past CO₂ and climate change;
2) Trace deep ocean carbon storage, and thus understand why natural CO₂ cycles happen.
Furthermore the underlying theory for why boron isotopes should record pH (and thus CO₂ - think acid rain) is unusually well understood. However the full potential of this "proxy" of past pH has not hitherto been realised, due to uncertainties in various aspects of the proxy systematics and difficulties in making accurate and precise boron isotope measurements.

My PhD research has developed a new method of measuring boron isotopes by Muti-Collector Inductively-Coupled-Plasma Mass-Spectrometry (MC-ICPMS). This technique overcomes difficulties including small sample sizes (~10 nanograms of boron), high blanks and large mass fractionation to obtain accurate and precise data (± 0.25 &permil, ~0.025 pH, 2 sd), from samples as small as 10 benthic (deep sea-dwelling) foraminifera. We have used our new method to thoroughly test the &delta¹¹B - pH proxy with an extensive "core-top" calibration of recent deep sea benthic foraminifera. We find a good match between pH calculated from foram boron isotope measurements and nearby ocean pH measurements. This suggests our understanding of the &delta¹¹B - pH proxy is sound, and that we may use boron isotope measurements to track the ocean CO₂ system in the past. My initial "down-core" measurements of foraminiferal &delta¹¹B reveal a strong coupling between deep ocean carbon storage and atmospheric CO₂ during the last deglaciation, highlighting the vast potential of this technique to improve our understanding of past changes in the carbon cycle. Such improved understanding of ocean-atmosphere CO₂ exchange is crucial in our predictions of the fate of fossil fuel CO₂ in the ocean-atmosphere system, and thus the future path of anthropogenic climate change.

Source of funding:

NERC

Start and finish dates:

October 2007- April 2011

Further Information: