The authors presented the carbonate data collected by the DFO in the Atlantic Zone Monitoring Program (AZMP) on the Canadian Atlantic Continental Shelf Between 2014 and 2020. This data set is valuable and useful for future comprehensive analysis and modeling work along the Atlantic Coasts. The continuation of these efforts is essential to monitor ocean acidification and to support fisheries management. However, there are several minor comments that authors should pay attention to:

1).  Equation (5), the expression of saturate state is wrong. And the symbol of the solubility product (Ksp or Ksp*) is not consistent with the main text.

2). Line 115 – 120. The geographic names are not labeled in either Figure 1 or Figure 3, which leads to confusion. In addition, it is hard to distinguish the TCEN transect, CGSL, and LC transect from Figure 3, especially when the names are not well labeled. Also, several other geographic names are mentioned in the main text yet are not labeled in Figure 1 or 3.

3). Line 150 -155. The Rimouski Station and 26 are not found in Figure 1 or Figure 3

4). Line 190 -195. What equations are used to calculate pH from absorbance value? Are pH samples corrected for dye perturbation?

5). Table 1. It is very useful to give a summary of the cruise information. However, I would strongly recommend adding one column to indicate what is measured carbonate parameters during the cruise because some syntheses only would like to use the measured data instead of extrapolated and calculated values.

5). The font size of the axis and color bar are too small in all the surface figures. Especially in Figures 6,7, 8. Also, the unit should be consistent as the main text (umol kg^-1)

6). Throughout the whole text including the figures,  the p of pCO₂ should be in italics 

7). I would suggest Figure9 a and b as one figure and c and d as another since they are not focusing on the same issue.

Review ESSE-2022-460

General Comments:

The paper provides an overview of carbonate chemistry parameters on the Canadian Atlantic Continental Shelf between 2014 and 2020. The authors have systematically measured at least two of the carbonate parameters in this region since 2014, allowing for the calculation of all carbonate chemistry. The paper presents valuable and important results in the context of the ongoing climate change and ocean acidification. However, there are some important points that must be addressed in this manuscript.

The main concern is with the figures' presentation and the general structure of this manuscript, particularly Figures 6, 7, and 8 (and discussion, see below). Despite the fact that the manuscript is well written, it is difficult to follow some of the authors' choices regarding the manuscript's structure. For example, why did the authors only show the maps of the surface and bottom of fall 2017 (Fig. 6 and 7), while the results for other seasons are in the annexes? In the same direction, it is not clear why only some parameters and seasons appear in Fig. 9. The authors should explain these choices more clearly in the main text. I suggests that the authors revise the acronyms used in the text, figure captions, and graphs, as they are not consistent.

I have two concerns about the carbonate chemistry data: (1) the TA-S relationship should not be used to derive the TA in sampling campaigns where TA was not measured, as the TA-S relationship shows an R2 that is far from the conservative mixing, particularly for data with salinity < 30; and (2) I strongly suggests that the authors perform a quality check of the carbonate chemistry calculations. In some oceanographic campaigns, the authors performed the analysis of the three-carbonate parameters (pH, DIC, TA). Therefore, the calculated values can be compared to the observed values for these three parameters. This is important because the water pCO2 was not directly measured.

Finally, the "Discussion and Conclusion" section is very short, and I don’t know if this is a general recommendation of the ESSD. If not, I recommend that the authors go deeper into the discussion. Furthermore, many passages of the results section are discussion, so it is necessary a rearrangement and a review of these sections.

Specific comments

Abstract: The abstract is highly informative, but more in a qualitative way. I would like to see more quantitative information. Moreover, some statement about temporal trends (if any) along the studies period would be great.

The Fig. 2 is great, but the labeling is very confuse and not all acronyms are explained. Some acronyms appear in the figure, but not in the caption whereas some acronyms appear in the caption, but not in the figure. Some texts in the figure are difficult to read. Please revise.  

The eq. 2 actually presents two equations of equilibrium. I recommend presenting:

CO2(aq) + H2O = H+ + HCO3-

HCO3- = H+ + CO32-

In the eq. 3 there is an error: it is not 2Ca+, it is Ca2+. Please refer to Millero (2007).

Millero, F. 2007. The Marine Inorganic Carbon Cycle. Chem. Rev. 107, 308-341.

There is another process, which is the dissolution and precipitation of CaCO3 that it is also very important in this context. The equation should appear in the text: Ca2+ + 2HCO3- = CaCO3 + CO2 + H2O.

Line 73: “For example, the dilution of sea water decreases all carbonate parameters, except for pCO2.” Avoid this type of generalization. Are you referring just to the Canadian Shelf? It should be explicated. The freshwater endmember is highly variable and can show higher or lower values of DIC, TA, than open ocean waters. Overall, tropical rivers present lower TA concentrations than temperate/boreal rivers, thus the impact of thermodynamic  processes during river-ocean mixing are largely variable (Cai et al., 2008; Cotovicz et al., 2020; Abril et al., 2021).

Cai, W.-J. et al. 2008. A comparative overview of weathering intensity and  HCO3− flux in the world’s major rivers with emphasis on the Changjiang, Huanghe,  Zhujiang (pearl) and Mississippi Rivers. Cont. Shelf Res. 28, 1538–1549. https://doi. org/10.1016/j.csr.2007.10.014

Cotovicz et al. 2020.  Carbon dioxide sources and sinks in the delta of the Paraíba do Sul River (Southeastern Brazil) modulated by carbonate thermodynamics, gas exchange and ecosystem metabolism during estuarine mixing.  Mar. Chem. 103869.

Abril et al. 2021. Thermodynamic uptake of atmospheric CO2 in the oligotrophic and semiarid São Francisco estuary. Mar. Chem. 103983.

Line 110. As I recommended before, please review all acronyms and be consistent in the text and in the figure captions.

Fig. 4. You should present the scale of pH (Total?).

Lines 220-230: You stated that “Since there are only a few surveys that include all three parameters (TA, pH and DIC), we have not produced the errors associated with the calculation of carbonate parameters because it would not be a representative calculation for the entire Atlantic Zone”.  I think the quality check is important for calculation purposes, particularly for water pCO2. I am not asking a complete error analysis, but some quality check is useful. As you used the TA-pH pair to calculate pCO2w, the presence of organic alkalinity (especially in nearshore, productive regions) can be significant and influence the pCO2 value. As you have some measurements including all three parameters (TA, pH and DIC), you can compare “calculated” x “observed” values.

Line 235: The TA can be estimated using the TA-salinity linear relationship only if the strength of the relationship is strong and almost conservative. The equation that you presented “ TA = 41.26 x S + 870.05 (r2 = 0.93, p < 0.001)” is far from the conservative mixing, and probably reflects some biological processes of production and/or consumption of TA. The Fig. 5b shows that data for salinities < 30 are highly dispersed from linearity, and this should affect TA estimation. Therefore, I recommend to calculate TA using the TA-salinity only for salinities > 30, or to remove this data from the manuscript.

The molecular formula of some nutrients are wrong. Please correct.

The structure of presentation of some Figures is not clear. For example, why did you present the fall 2017 maps in Figures 6 to 8, while for other seasons you present in Appendix A? Please refer also to the general comments.

Lines 330-335: This is discussion, not results.

Lines 343-345: This is also discussion.

Results for pH: As you have a high accuracy of pH measurements (0.005), I strongly recommend showing the results in two or three decimal places.

Lines 353-354: This is discussion, not results.

Lines 356-357: “The surface water pH is relatively uniform throughout the Atlantic Zone in the fall (∼7.8 to 8.1).” Not really.  The variability of 0.3 is not low.

Lines 362-364: This is discussion, not results.

Lines 375-377: “The surface waters of the USLE are undersaturated (Ωarg < 1) with respect to aragonite (and in some instances calcite) due to low TA and DIC”. This is discussion, not results. In addition, this explanation is weak. Indeed, the saturation state decreases probably due to decrease of TA compared to DIC. This can be investigate by plotting DIC/TA ratio against Ω.

Lines 380-381: This is discussion, not results.

Discussion and Conclusion: This section is short, and I do not know if this is a characteristic of papers published in ESSD. If this is not the case, I recommend expanding this section. Furthermore, there are very few literature citations here. This should be reviewed. Finally, there are many sections of the “results” section that are, in fact, discussion. Therefore, the structure of the manuscript should be reviewed, and the discussion should be enhanced.