It is now well documented that atmospheric carbon dioxide concentration (pCO2) changed in parallel to the growth and decay of polar ice sheets over the last 800,000 years. However the mechanisms that cause these variations in CO2, and exactly how they are related to Earths’ climate remains much debated. This is a crucial issue given the current anthropogenic increase in pCO2 and it was recently identified by the IPCC as a key uncertainty in our understanding of the climate system as a whole. Although the exact processes are contested based on the magnitude and rapidity of the rates of carbon exchange, it is generally accepted that changes in oceanic carbon storage play a vital role in causing glacial-interglacial CO2 change. The overall aim of this proposal is to better understand the role of intermediate waters ventilated in the Southern Ocean in the rise of CO2 during the last deglacial.To achieve this aim, we will use the boron isotope-pH proxy in planktic foraminifera from a suite of key locations (Southern Ocean and Equatorial Pacific) to reconstruct oceanic pH changes during the last deglaciation, with the objective of documenting where and when CO2 was leaked to the atmosphere from the deep Southern Ocean during the deglacial. The generated data will be then tested against a new model output of the GENIE Earth System Model, in order to determine the relative importance of the deep carbon reservoir in driving Glacial-Interglacial CO2 change.