High-resolution Boron and beyond Geologic reconstructions for carbon and climate processes

The link between climate and CO2 is not always straightforward, particularly during periods of multiple climatic and environmental changes, but atmospheric carbon dioxide (CO2) plays an important part in determining climate on human and geological timescales.

For example, state dependency of climate sensitivity, the response of Earth’s temperature to CO2, is a critical unknown for future climate projections and policy strategies.

Another unknown is the response of the Antarctic Ice Sheet (AIS) at different CO2 thresholds for its melting and growth, “hysteresis”, despite the fact that this will ultimate determine the magnitude of future sea level rise.

Existing records suggest that the ice sheet margin waxed and waned since the Eocene, ~50 million years ago (Ma), while CO2 varied within the likely range projected for year 2100 and Earth’s temperature progressively cooled.

HighBorG aims to resolve climate-AIS-CO2 unknowns on three periods of the geologic past: 52-46 Ma (hot Earth, high CO2, likely ice free), largely unexplored 39-23 Ma (when AIS was established), and 17-13 Ma (cold Earth, low CO2, dynamic AIS).

HighBorG focuses on reconstructing CO2-climate feedbacks at millennial/orbital timescales, a medium risk high gain opportunity necessary to resolve warming and cooling periods at different climate states.

To achieve this, a new automated system for purification-analysis will be developed, accompanied by a laser ablation split-stream approach, utilising new marine archives and cutting-edge methodologies.

Seasonal reconstructions from contemporaneous tropical corals will provide a novel way to constrain seawater composition, necessary to obtain accurate estimates of CO2.

Earth system modelling incorporating reconstructions will provide a new understanding of the mechanisms driving state dependent interactions between Earth’s orbit, CO2, temperature, cryosphere and carbon cycling, increasing our confidence to sea level/temperature projections for the future.