Dear Dr. Terhaar,

I have read your answers to both reviewers' comments and based on that I invite you to submit a revised version of your work addressing point by point each reviewer's concern. In particular, I recommend that you clearly address two major concerns of reviewer 2 and clarify how the amount of anthropogenic carbon has been estimated in both the model simulations and from the data.

Thank you so much for your efforts,

Kind regards,

Marilaure Grégoire

Dear Dr. Terhaar,
I have read the revised version of your manuscript as well as the reviewers comments on that revised version. Both reviewers have appreciated your efforts in improving the first submitted version and agree that most of their comments have been taken into account. However, one of the reviewers considers that some of his/her comments have not been taken into account with sufficient details. More specifically, she/he pointed to a misunderstanding in the use of the TTD method that leads to conclude to an overestimation of Cant based on observations. She/he strongly disagrees that based on model simulations you have robust arguments to suggest an overestimation of the data-estimated Cant , especially because the model underestimates CFC inventories and hence Cant. This point needs to be thoroughly addressed in your revisions. The reviewer is also asking complementary information as concerns the comparison of the three model configurations with 1) justification for not running the ORCA2 simulation since the pre-industrial era in order to avoid an impact of the initialization process in 1958, 2) differences in terms of vertical resolution and parameterization of mixing processes. I recommend that you clarify all these points in a revised version.
Thank you for your efforts,
Kind regards,
Marilaure Grégoire

Dear Dr. Terhaar,
I have read the revised version of your manuscript and based on that and on the feedback from the reviewer, I am pleased to accept your paper for publication in Biogeosciences.
Thank you so much for your efforts,
Kind regards,
Marilaure Grégoire