Ice age oscillations in atmospheric CO2 are moderated by ocean circulation and stored in the deep ocean carbon reservoir, but the mechanisms connecting the atmosphere-terrestrial biosphere-deep ocean carbon cycle remain unclear. From deep sea sediment cores, we use benthic carbon isotopes (d13C) from Cibicides wuellerstorfi to reconstruct past ocean circulation and carbon cycle changes. With globally distributed benthic d13C records spanning the last 30 kyrs, we can examine changes in the 3D geometry of ocean water masses across the deglaciation, from the Last Glacial Maximum (LGM) to today. By estimating the mean change in whole ocean d13C from the LGM to today, we estimate the change in terrestrial carbon storage associated with deglacial climate change. Furthermore, we can investigate the different sources of variability in benthic d13C with Principal Component Analysis (PCA). Separating out the primary signals in benthic d13C allows us to interpret transient changes in d13C in terms of changes in ocean circulation and carbon storage. An enhanced understanding of the relationships between climate change and the ocean carbon storage is timely as ~30% of anthropogenic CO2 is currently absorbed by the ocean.