Research Overview

Here is an introduction to my research. For more details see individual project pages and publications

Ancient climates and modern questions

I spend most of my working-life creating geochemical proxy datasets in order to understand ancient environmental processes. My focus is on reconstructing global processes, such as oceanic anoxia and acidification of the oceans, during periods of past global warming. These geological processes represent major hazards for life on Earth and have directly caused mass extinctions in the past. We are also seeing these processes occur in real-time today as we continue to modify our natural environment via anthropogenic activities, including dumping fertilisers in the ocean from runoff and the burning of fossil fuels

Illustration of some of the major processes we can study with geochemical proxies. Image credit M. Schobben

The aftermath of climate catastrophe

There are many examples of perturbations to the global climate system, and each one gives us unique insights into how the Earth responds to rapid change. Although we don't have a perfect analogue for modern climate change, we can learn a lot of each of these events. In recent years, I have moved my research to focus on understanding climate 'recovery' processes, which help return the Earth to a stable state in the aftermath of a global warming event. There are natural feedback process that occur as a result of warming and act to remove the CO2 from the atmosphere-ocean system on long timescales. Examples of these mechanisms include organic carbon burial due to heightened productivity in the oceans, and enhanced silicate weathering.

Eventually the climate recovers, but this takes hundreds of thousands to millions of years.

And the carbon emission must end first to allow the system to recover.

Multi-proxy geochemical toolbox

I have worked (directly and indirectly) with a diverse suite of traditional and non-traditional geochemical proxies, with each one giving a different and unique insight in past environmental change that can be linked together for a holistic view of Earth system change. My focus at the moment is on using metal isotopes as novel proxies for the global extent of seafloor anoxia and local evolution of redox conditions (U and Mo) or potentially to reconstruct primary productivity (Zn, Cd, Ni). In the past I have also used B isotopes as a proxy of ocean pH, C isotopes to understand the balance of carbon emission and burial processes, sequential Fe-speciation and S isotopes to reconstruct local redox conditions. These proxies are compared to systems like Sr, Ca, Li and Mg to identify changes in weathering regimes and attempt to couple terrestrial and marine systems.

Biogeochemical models and proxy integration

I work with colleagues who specialise in biogeochemical modelling in order to integrate geochemical datasets with knowledge of climate evolution. The development of coupled isotope-biogeochemical model frameworks is an exciting direction for the field! It allows us to quantify the environmental processes that drive the geochemical datasets. In doing so we take an internally consistent view of the global Earth system during climate perturbation events, and have a more robust understanding of what our proxies mean.

The present is the key to understanding the past

Our understanding of past climates is only as good as the tools we use. And these are only as good as our knowledge of modern systems. This is why I study the details of proxy behaviour and preservation in modern environments. Recently this has involved assisting with measurements of trace metal isotopes in modern low-oxygen environments. We also apply these techniques to well known examples of environmental change, in addition to looking back into 'Deep Time'.

Carbonates as an archive

I have focused on using carbonate sediments as an archive for changes in past ocean chemistry. The idea is that when carbonates precipitate in the ocean, as an organism such as foraminifera, they sample the ambient ocean chemistry. Some trace metals are incorporated into the carbonate crystal lattice, preserving it over millions of years for us to study today. In order to use these sediments effectively I have spent a significant amount of time, together with the help of a PhD student, testing methods to dissolve the carbonate, whilst avoiding other components in a sediment such as clays and other minerals.

This is not as simple as it sounds!

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