As the Earth System evolves in response to accumulating carbon dioxide emissions, the ongoing role of the ocean in the global carbon cycle is unclear. In the present day, carbon uptake is acting to buffer atmospheric levels, and the weight of evidence suggests that that will continue at least until century-end. At the same time, it is recognised that dynamic reorganization of the ocean carbon cycle has taken place in the geological past. The high-latitude oceans make the major contribution to present-day mitigation and, most likely, past change. Understanding of carbon cycle dynamics in these important and complex regions, however, has been critically hampered by limited observations and imperfect Earth System Models with long-standing biases and uncertainties. Consequently, process-level understanding of the high-latitude oceans is under-developed. The paleo-oceanographic archive provides a unique window into the long-timescale evolution of the high-latitude ocean carbon cycle. Its utility is yet to be exploited to its full potential for developing process-level understanding and improving model predictions. My UKRI FLF programme will capitalize on recent advances in the paleo-record, improved observation of contemporary ocean biogeochemistry, and new approaches to ocean modelling, to constrain our understanding and projections of a changing high-latitude ocean carbon cycle.