Dear Author,

Thank you for submitting a revised version of your manuscript submitted to Biogeosciences, which I am glad to accept for publication provided that you consider the referees' comments below.

I look forward to seeing this paper published and thank you for considering Biogeosciences to publish these very interesting results.

Best regards,
Jean-Pierre Gattuso
BG Editor



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Referee #1

This paper is much improved in the re-submitted version. Shorter, easier to read, and a good use of the heavy armament in the Princeton-GFDL complex. The history of the field is a bit abbreviated, but that would only lengthen the paper. I only have one comment for curiosity. The authors note the strong signals in the Red Sea. I suspect that the Persian Gulf has perhaps stronger riverine signals overlaid due to the significant river input at the northern end, and older but good quality alkalinity data are available (e.g. Brewer, P. G. and D. Dyrssen (1985). Chemical Oceanography of the Persian Gulf. Prog. Oceanog.,14,41-55.) The Persian Gulf influence is small on the oceanic scale, but it may offer an interesting end member for the discussion.

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Referee #3

The authors have responded to all of the comments I made. They have not been ignored. Although I do not completely agree with all of their responses to my comments (for instance, a lack of certainty about errors in the Alk* values does not in my opinion justify omitting statistical hypothesis testing), I think the most serious and obvious mistakes have been corrected. However, perhaps not surprisingly given the scale of the changes, other errors have now crept in as detailed below. There are also grammatical errors, references to the wrong figures or figures that no longer exist, etc. I recommend that the manuscript needs to be checked through rigorously one more time by the authors before it can be accepted.

Line 22: The numbers are wrong. 0.5 – 1.6 Gt C y-1 (in Table 3 of Berelson 2007) converts (multiply by 1000, divide by 12 then multiply by 2) to 80-270 TMol alkalinity y-1. The “x 10” should also be removed.

Line 50: “interested calcium” ?

Line 105 should be changed to read “...plus the small (in most places) residual variation...” It is negligible across most of the ocean but in fact rather important in several regions.

Line 203: there is no figure 6d anymore.

Line 211: Only Fig 7b is relevant and it only shows the Bay of Bengal.

Line 223: Fig 7 no longer shows this.

Line 231: Fig 8 no longer shows data from the Red Sea.

Line 238: better to say “abiotic carbonate formation” (I presume that is the intent) because inorganic carbon(ate) is PIC.