Christopher Day

I am an isotope geochemist researching palaeoclimate and environmental reconstruction within the Environmental Proxies Isotopes & Climate (EPIC) group that I lead. Please do contact me by e-mail with any questions regarding laboratory or research interests.

Proxy development:

A significant amount of research conducted by our group (EPIC) and collaborators is developing and calibrating proxies for environmental change, using cave stalagmite samples.

Stalagmite measurements add significantly to the more traditional marine- and ice-core records. They provide extremely high resolution records of e.g. the hydrological cycle (monthly in certain cases), are well preserved, and can be dated in absolute terms using U-Th or U-Pb dating.

To make best use of stalagmite archives we need to calibrate the response of their chemistry to environmental change. To achieve this, I built a laboratory setup for growing carbonate crystals in controlled, cave-analogue conditions – the ‘Oxford Cave’. Some of my past work was calibrating the response of e.g. O, C, Ca, Mg, Ba, Sr, Cd to changes in rainfall amount and temperature.

Research is also ongoing with less traditional proxies , (e.g. clumped isotopes, Li-isotopes) to further develop our understanding of these systems and to widen the scope for environmental reconstruction (e.g. weathering intensity).

Palaeoclimate reconstruction:

With students and collaborators, knowledge from the Oxford Cave is applied to palaeoclimate reconstruction projects in e.g. Morocco, Southern Chile, China. We demonstrate, amongst others, the use of Cd as a sensitive proxy for changes in rainfall amount and the application of Ca isotopes for reconstructing absolute change in rainfall amount during abrupt climate change events.

CaveCalc forward modelling software tool:

CaveCalc is a numerical forward-model for speleothem and dripwater chemistry written by Dr. Robert Owen. Proxies modelled include carbon isotopes (stable and radiocarbon), oxygen isotopes, calcium isotopes and trace metals (Mg, Ba, Sr). Processes include bedrock dissolution, carbon dioxide degassing and calcite precipitation. CaveCalc can explicitly model semi-open system bedrock dissolution. It is based on PHREEQC, and is open source.

CaveCalc is being used in increasingly interesting ways, e.g. work led by Franzi Lechleitner to reconstruct absolute values of past soil pCO2 , or work led by Heather Stoll to reconstruct evolving initial solution δ13C to better constrain ongoing changes in the soil carbon cycle above caves.

Stable Isotope Laboratory management:

My research runs alongside managing the department Stable Isotope laboratory, a central hub for research into oceanic, terrestrial, hydrological and carbon cycles. Both sides of my role complement each other, with a vested interest in continually improving the capability of the Stable Isotope laboratory to best serve our research interests.