In this paper , Emily Newsom and co-authors Laure Zanna and Jonathan Gregory, showed that the relative depth of ocean heat sequestration, which varies widely across climate models and paces the rate of surface climate warming, is strongly correlated to interior ocean stratification. Using a novel regional decomposition method, they showed that this relationship is entirely driven by mid-latitude ventilation processes and explains 70% of the variance in heat penetration depth across CMIP5/CMIP6 models. Therefore, uncertainty in future projections of ocean heat uptake can be reduced by constraining present-day ventilation. This can be achieved by correcting SST biases in climate models and improving subgrid representations of ocean processes which are key goals of M²LInES.