Dear Dr. Feistel,

Thank you for your interesting manuscript and congratulation to the 2018 Fridtjof Nansen medal.

The two referees were happy with the manuscript and had only few comments. Your answers to those are satisfactory, however, I would have expected to see (part of) those back in the manuscript, as this would enhance the understanding for the readers. I am adding some comments, which I hope you will include in the final submission.

“Outside oceanography is the only the scientific community recognises salinity.” I think the problem of the referee lies in the phrasing. Please consider: Oceanography is the only the scientific community that recognises salinity.

Referee #2: Does he mean density salinity or Reference Composition salinity?
- Neither nor. Density Salinity is recommended as the currently best estimate for Absolute Salinity, while Reference-Composition Salinity is the currently best estimate for Absolute Salinity of SSW.
Editor: Did you address this in the manuscript?

Referee #2: For standard seawater, Sp is mathematically equivalent to SR, since the two are related by a fixed conversion factor, so in some sense, the distinction between Sp and Absolute Salinity is only justified for seawater that differs from standard seawater. It seems to me, however, that from a practical viewpoint, one does not really have the choice at the moment when numerically modelling the ocean but to neglect composition anomalies and to assume fixed composition, since if only one evolution equation is used to describe salinity, it has to be for reference composition salinity SR or equivalently Sp, since the equations for both quantities are exactly the same but for boundary conditions.
- Appendix A.20 of the TEOS-10 Manual discusses the question of modelling several salinity variables.
Editor: Please briefly address this in the manuscript.

Moreover, isn’t it a problem that density also depends on pressure and on the precise value of gravity at the place of measurement?
- Density measurements are carried out under laboratory conditions at well-known air pressure. Using the TEOS-10 equation of state, the results are transferred to in-situ conditions at known pressure. This is briefly mentioned in additional text in Section 5.1. Gravity conditions affect the local pressure via the hydrostatic equation but are largely irrelevant if the pressure itself is measured rather than computed.
Editor: Please briefly address this in the manuscript.

P17, L13 I do not understand this sentence. Please make clear.

Reference Budéus update:
G. Th. Budéus: Potential bias in TEOS10 density of sea water samples,
Deep Sea Research Part I: Oceanographic Research Papers, 134, 41-47, 2018,
https://doi.org/10.1016/j.dsr.2018.02.005.

Burchard et al: update avauilable? Doi?
Feistel 2017. Please provide translation of the German title.

Comment by Hannes Schmidt: Comment on Page 7 Line 26–30
I think Schmidt touches a problem that needs more explanation in the manuscript. Please add (part of) your answer to the manuscript.
Comment by Hannes Schmidt: Comment on Page 10 Line 27
Same as above.

With best wishes
Mario Hoppema