The partitioning of carbon between earth surface reservoirs and the atmosphere is key to dictating the content of carbon dioxide in the atmosphere (pCO2), which acts as a feedback on global climate. Over past geological timescales the atmosphere has been a passenger to changing physics, chemistry and biology, most notably in the ocean. In modern and future times, the world is encountering the unusual experiment that the burning of fossil fuels and rising atmospheric pCO2 is, instead, acting as a driver of the physics, chemistry and biology of the ocean. This session invites contributions which address this interaction between the carbon cycle and the ocean both from a past and future perspective, encompassing but not restricted to glacial-interglacial pCO2 change, Southern Ocean processes, the ocean as a buffer to change and ocean acidification. One particular aspect of interest will be to explore what lessons can be learned from the past to help adapt to or mitigate against future changes.