Tom Chalk
Thomas Chalk is a researcher at the Centre Nationale de Recherche Scientifique (CNRS), in Aix-en-Provence, France. He specializes in environmental science and palaeoclimatology using geochemical tools. He uses geochemistry as a tool to reconstruct and understand modern environments and past climate, notably including proxies based on the element boron and its isotopes. With this he has a strong research focus on the reconstruction of ancient pH and atmospheric carbon dioxide. He is also interested into how calcifying organisms are impacted by climate change, and/or how they can influence Earth’s climate themselves. Thomas uses experiments in the laboratory and the field to try and better understand the links between the ocean, climate, and carbonate minerals.
Improving Neogene CO₂ Reconstructions: Collection, Calibration, and Innovation in the boron isotope pH proxy.
Neogene records of greenhouse gas forcing are generally of the highest quality from geological time, yet when we zoom in there are many gaps, and extremely few highly resolved records prior to the ice cores, and none prior to the Pliocene. Contained within this period are the Pliocene-Pleistocene transition and Middle Pleistocene Transition (3.4–2.5 million years ago and ~1.2–0.6 million years ago respectively) which both represent major shifts in the Earth’s climate, and are both associated with global cooling, yet their fingerprints are quite different. I will present investigations into the use of the boron isotope pH and CO2 proxy over the last 10 million years. A community-wide effort is devoted to improving our knowledge of past CO2 measurements from the boron isotope proxy. Through the standardisation of data processing methods and repeal of out-dated or erroneous records, this will improve accuracy and precision of ancient atmospheric records. In addition, new methods of data generation, data archives, and calibration are allowing new data sources to be investigated and older results re-interpreted. Here I will combine records of pH gradients derived from multiple species of foraminifera and of intrasample variability derived from laser ablation alongside high precision and orbitally resolved “traditional” solution measurements. We move towards a continuous sedimentological record of atmospheric CO2 which will have wide reaching implications for climate sensitivity calculations, palaeoclimate, palaeoceanography, and more over the last ~7 million years.
