Analysing frozen Foraminifera by Cryostage LA-ICPMS: Neogene CO2, patterns, cycles, and climate sensitivity.

Knowledge of past concentrations of atmospheric carbon dioxide (CO2) has transformed our understanding of earths climate: past, present, and future. Ice cores have yielded 800,000-years of high resolution and high precision data, revolutionising Earth system science.

Marine sediment records provide the opportunity for highly resolved records of ocean and past ocean pH (and therefore ocean and atmosphere CO2 content) over millions of years by means of the 11B-pH proxy, but present progress is currently hampered by large sample size requirements and intensive laboratory techniques limiting throughput and applicability.

Innovation is therefore required to answer a number of key questions, including: how do spatial variations in ocean carbon flux cause natural climate variability?, and does climate sensitivity vary with background state?

By analysing small samples frozen into a blank-free ice puck, ForCry exploits the increased sensitivity of laser ablation 11B analysis to enable the next generation of past climate data to be recovered.

This novel approach allows analyses to be conducted on 20 individual plankton representing a ~10fold reduction in sample size, but while maintaining precision.

Additionally, this approach removes costly chemical purification steps and leads to higher throughput which makes high-resolution CO2 reconstructions using the 11B-pH proxy a viable option to augment and extend the ice core CO2 records.

ForCry has 4 objectives: i) to develop this novel technique and optimise the hardware for efficient data collection from carbonates and other archives: ii) to calibrate through culture and field sample collection the 11B-pH proxy in multiple species of foraminifera: iii) to map ocean pH change in four dimensions using a data inversion model; and iv) to reconstruct CO2 change at high resolution over key past intervals (e.g.

Mid-Miocene) that are highly relevant to a warm future, thus probing the state dependency of climate sensitivity.