Dear Dr. Mahieu and co-authors,

Thank you for the revised submission. I am generally satisfied with the changes you made following the comments by the referees. Going through the manuscript myself, I have listed my comments below. Please prepare the final version of your manuscript taking into account these comments.

In the title: Antarctic Bottom Water (without –s) as this study measured only one type at one location.

Section 2.1 is clearly part of the methods and should thus be moved to Section 3.
I suggest to call the water mass defined here as Lower AABW, not as Low AABW. Just like other well-known water masses like Lower CDW, etc.

Please place all 2 in CO2 in subscript.

Please check the references because many are incomplete.

As to the data used in this study, there are several more OISO cruises (as also in the GLODAP tables). Please provide the arguments for including the cruises that the authors did, while excluding others.

As to the supplement Table S1 (and discussion in the main text) with the adjustments from the different quality control efforts, it is shown that AT at the OISO cruises did not receive any adjustments. However, this is not the complete story. The GLODAP table says that there is not sufficient data for comparison in this region, upon which the OISO data did not get an adjustment because this could not be argued safely. This is actually the same as getting no quality control. This should be made clear in the manuscript.

L5 Shouldn’t the University of Liverpool be mentioned?
L9 Antarctic bottom water (AABW) is known …

L9 … but the sink is hardly quantified …
L13 in the framework of …

L16 At this location, the main sources of AABW are the low-saline … (fresh is not the word here, because this is a saline water mass; I suggest to skip “younger” because: younger against what?)

L20 SO has not been defined before
L24 hydrographic (not: hydrological)

L27 AABW
L27-28 This sentence is trivial, and if not followed by which of these processes are important or how they function, not necessary/useful.

L43 3% is more like the maximum. Mostly Cant is much less. I suggest to write here: less than 3%

L53-55 “Thus, there is a need to better explore the CT and Cant temporal variability in the deep ocean, especially in the SO where observations are relatively sparse.” I cannot understand the connection of this concluding sentence with the previous text in this paragraph. Please modify.

L56 AABW (without –s) Please change this throughout the manuscript.
L58 … by covering a major part of the world ocean floor …

L84 Study area
L86 framework

L98 is dominated by (instead of: is mainly governed)
L111 … Lower Circumpolar …

L112 I think HSSW is generally the abbreviation for High Salinity Shelf Water
L116-117 The PE deepest point of the PET is 3750 m, …

L158-160 “The accuracy of CT and AT measurements was ensured by daily analyses of Certified Reference Materials (CRMs) provided by A.G. Dickson laboratory (Scripps Institute of Oceanography).” This is indeed important to warrant the accuracy. For the interpretation it is also important to know the accuracy. Please give the accuracy here.

L164 silicate (no capital)
L171 using (instead of: considering)

L171 I do not understand why the value of 33 umol/kg was used, as the mean value from GLODAPv2 is 32.4 umol/kg. Even if the error because of this is small, it does increase it for no good reason.

L187-188 from deep waters free of anthropogenic CO2 …
L245-246 “the theoretical Cant trend at the AABW formation sites would be of the order of +8 μmol.kg-1.decade-1.” How was this calculated? Only part of the AABW, when it is formed, contains water that has been at the surface. Only that part could follow the atmospheric increase on CO2. What percentage of surface water was assumed as contributing to AABW?

L288 experiences
L310 and ends … (instead of: and lasts)

L315 … in the 1980s in the Indian sector of the Southern Ocean …
L316 quality control (instead of: qualification)

L427 “recognized freshening of AABWs over the last decades (Rintoul, 2007).” With a reference from 2007, this is not about the last decades. Please change wording or give a different reference.

L484 change to: GLODAPv2.2021
L504 Please add info on what kind of this reference is and possibly where it can be found online.

L506 Cycles (also in other cases where this journal is concerned)
L538 pages: 205-206

L551 pCO2
L602 should be cited as: 18, GB1042, doi:10.1029/2002GB002017

L606 should be cited differently, similar as above
L624 pages: 346-349

L636 pages: 1221-1224
In many cases the references are incomplete, for example missing page numbers. Please go through the references and correct them.

Figure 1 Please add that these are very rough transport paths. The dashed line for the ACC gives the position, says the caption. What position? The ACC is wide; please explain. The path of the AABW in the Weddell Sea is not correct. Neither is the path of the AABW from Prydz Bay and Cape Darnley, which flows along the coast to the west and enters the Weddell circulation.

Figure 2 The term is Hovmöller diagram.

Thank you and best wishes
Mario Hoppema