Thomas ChalkScientist

Centre européen de recherche et d'enseignement de géosciences de l'environnement (CEREGE)1

ForCry (Horizon Europe - ERC StG 101040461)
Analysing frozen Foraminifera by Cryostage LA-ICPMS: Neogene CO₂, patterns, cycles, and climate sensitivity

Knowledge of past concentrations of atmospheric carbon dioxide (CO₂) is fundamental to our understanding of earth’s climate: past, present, and future. Ice core records, the international effort to retrieve trapped bubbles of ancient atmosphere, have provided high resolution and high precision data for the last 800,000 years which has revolutionised Earth system science. ForCry, a technique designed by awardee Thomas Chalk will enable the next generation of past climate data to be recovered. Marine sediment records provide the opportunity to recover spatially and temporally excellent data records from modern and past ocean pH conditions (and thus CO₂ content). However, to date these records are hampered by labour intensive laboratory techniques limiting throughput, and large sample requirements limiting applicability. Improvement is required to access important questions about our climate such as: ‘what controls the spatial changes in ocean carbon flux which dominate natural climate variability?’, and ‘does climate sensitivity change with background state?’. ForCry enables the increased sensitivity of laser ablation methodology to be realised using tiny samples by freezing them into an essentially contaminant-free ice ‘puck’. This allows analyses to be conducted with a ~10–fold reduction in sample size while maintaining precision. ForCry will explore multiple facets of Earth System Science to expand the use of laser ablation to new fossil archives, while seeking to map ocean pH change in 4 dimensions. The CO₂ content will be used to examine the state dependency of climate sensitivity in warmer times of the geological past. ForCry will examine our ocean's role in setting and/or moderating CO₂ past present and future at an unprecedented level.

• 1Aix-Marseille Université/CNRS/IRD/INRAE