Dear Jiang Zhu,
Thank you for providing a response to the editorial and reviewers' comments on your manuscript. Based on these comments i would like to invite you to provide at your earliest convenience a revised manuscript, in line with your response to review comments, with changes tracked/highlighted in order to aid in evaluating your revisions.

When you prepare your revised manuscript, I would like to encourage you to reconsider your dismissal of one particular review comment, regarding the illustration of the 'LGM' CESM ocean state (reviewer 2). You state that:

"The global volume-mean ocean temperature in the LGM simulation decreased by 0.15°C during the last 900 years. We will add this information in the revised manuscript. We do not think the comparison of the modeled whole ocean temperature with Bereiter et al. (2018) offer new insights regarding our findings, as our study uses CESM1 in a “perfect model” scenario to explore the assumptions associated with estimating ECS from knowledge of paleoclimate forcing and response."

However, it seems entirely relevant to me (and i invite you to respond) whether or not the ocean is at thermal equilibrium in your LGM simulation, and whether or not its state is one in which a significant net heat flux to/from the ocean exists, due to e.g. disequilibrium effects. A global ocean cooling of only 0.15oC is quite far from a realistic equilibrium LGM ocean state, based on observations such as the noble gas isotope measurements of Bereiter et al. (2018) for example. I would therefore suggest that when noting the mean ocean temperature change of 0.15oC in your LGM simulation (which i agree is important) you also provide a short discussion of why this result differs from observations such as those of Bereiter et al. (2018) (i.e. is it due to a disequilibrium ocean state?), and also what arguments you can advance for why your analysis and conclusions regarding ocean dynamical feedbacks etc... are unaffected by the ocean's energy/heat budget not being at equilibrium. In response to my own comments on a related theme you have proposed that the surface ocean is at equilibrium, even if the deep ocean is indeed far from equilibrium. I still think it is important to comment on this issue in the manuscript, since it is not obvious that the surface ocean or atmosphere can really be at thermal equilibrium if the deep ocean is in the process of accumulating heat over thousands of years (with a fixed TOA energy balance). The resulting changes might be slow, but they will accumulate into a different 'true LGM' state. Or, to state things differently, if you are indeed analysing a disequilibrium ocean state, then it might be more accurate to see the simulation as a transient cooling experiment and not as a comparison with the 'LGM', as modelled or reconstructed in other studies. Please therefore add a short note on why you believe it is not relevant for your study that the deep ocean heat budget is not at equilibrium in your simulations (if indeed this is the case).

I look forward to reading your revised manuscript, and your response to my last comments, pertaining to those of Reviewer 2.

With best wishes,
Luke

Thank you for your response.

I have recommended that the manuscript now be published.

With best wishes,
Luke Skinner