The sequence of events in the global carbon cycle during deglaciations is not entirely understood. Here, we analyse mean ocean δ13C and δ18O in an updated compilation of foraminifera stable isotope data consisting of 902 time series from 381 sediment cores covering up to the past 23,000 years. We use changes in mean ocean temperature from ice cores to split δ18O into its temperature and seawater components. We then show that a 0.47±0.05permil rise in mean ocean δ13C occurred quasi-synchronously with changes in seawater δ18O and is lagging the rise in atmospheric CO2 during Termination I by ∼2,000 years. Since mean ocean δ13C is mainly recording net changes in land carbon storage and seawater δ18O is mainly depicting the rise in global mean sea level this implies that land carbon varied in-phase with sea level and not with atmospheric CO2.