The role of atmospheric CO2 in the first great ice ages: insights from very high-resolution boron isotope records

The concentration of carbon dioxide (CO2) in the atmosphere is often said to be the "control knob" of Earth's climate. For instance, recent work at Southampton has confirmed that a decline in atmospheric CO2 played a key role in triggering the establishment of large Northern Hemisphere ice sheets 2.7 million years ago (Martinez-Boti et al., 2015; www.thefosterlab.org). On shorter timescales, ice core records have shown that CO2 also plays a crucial role in driving the well documented glacial-interglacial cycles of the past 2.7 million years (Quaternary Period) by amplifying the effects of small variations in solar radiation due to changes in Earth's orbit around the Sun. The exact processes involved and the sensitivity of the Earth to changes in CO2, however, remain key gaps in our understanding of the Earth system with clear relevance for our warm future (e.g. Martinez-Boti et al., 2015). In this project we will examine and use the initial glacial-interglacial cycles of the Quaternary, centered on Marine Isotope Stage 100 around 2.5 million years ago (Shakun et al., 2017), as a test-bed to address these fundamental knowledge gaps.