Overview: The authors are presenting a new, regional pCO2-product specifically designed for the North American Atlantic coastal region that provides monthly pCO2 at a .25-degree spatial resolution from 1993-2021. The product uses integrated random forest and linear regression methods incorporating observational products in order to generate their monthly reconstructed pCO2-product. This allows for analysis of regional, seasonal, and yearly trends in addition to an uncertainty calculation. The authors find through validation that their product provides high accuracy, improving public access for more precise, higher resolution coastal carbon dynamics in the NAACOM region.

There is great need for products like these to be publicly accessible, and this contributes an important resource to the scientific community. The authors do a nice job of introducing the field, the data gaps, and where this product can contribute to those gaps. I do recommend for publication, following a few edits as outlined below.

One edit I have for the paper regards the interchangeable use of fCO2 and pCO2. In section 2.1 the authors mention that “both are commonly used in oceanographic studies”, which is accurate. However, they are not interchangeably used. At the end of section 2.2 an equation to convert pCO2 to fCO2 is provided, but it’s unclear at what point this conversion is made. Figure 2 shows values in fCO2, but the rest of the figures use pCO2. I recommend a clear statement about conversion with the introduction of fCO2, as well as consistency in the figures (I would convert figure 2 to showing pCO2 or at least have a clear statement on the conversion and reason for fCO2 presentation in the figure caption).

My second edit has to do with the calculation of uncertainty. There is a calculation representing the inputs (u_inputs), but some of the products are in the original resolution and others are linearly interpolated to that resolution. Does the interpolation introduce more error, and is this taken into account? Additionally, I will note that I greatly appreciate the inclusion of an uncertainty calculation and the strength it lends to the product. I would have liked to see it highlighted a bit more in the rest of the paper results—some of the data could also be discussed with uncertainty included, rather than purely keeping the uncertainty in one section at the end of the paper. I think the addition of the uncertainty calculation makes this product stronger, and should be displayed as such.

Finally, Figure 5 and figure 7, and the associated discussions in 3.2 and 3.4, present some extremely interesting data. We compare some of the regional differences and the products effectiveness of capturing broader pCO2 patterns across the North Atlantic coast. I would have loved to had this extrapolated on a little further, and perhaps seen more numbers broken down by region. We can visually look at the figures, but it’s a little hard to assess and I think the paper would be strengthened by expanding this section a little more with increased quantitative results.

Specific Comments:

Figure 1: I felt that the colors of this figure made it difficult to interpret. The way the lines were drawn made the topography difficult to see. For consistency with the other figures in the paper, I would suggest shifting the coastal contour line to being black.  Then perhaps make the Gulf stream and Labrador current lines dotted or dashed lines (also, change Gulf Stream’s color if you shift contour to black), so they don’t block as much topography. I would match the labels of the regions to the lines denoting the regions, and finally increase the deviation in the color scale. Right now, it’s not very easy to tell a difference between 800-1000m, and similarly between 0-300m is all about the same tone.

Equations: center the equations in the document

Lines 183-184: The nature of this sentence is implying an interchangeable use of fCO2 and pCO2, which I don’t think is accurate

Line 284+: Authors show an area-mean bias of +0.17, but with the regional breakdown and discussion, I’d be very curious how that bias varies by region. Can we see numbers for the other regions as well?

Figure 5: Similar edit suggestions to figure 1; update contour line to be black and match the colors of regional names to the lines denoting the regions

Figure 6: the error bar denotes one standard deviation of the monthly mean climatology, but didn’t the authors also actually calculate a pCO2 error? Why is that not included in any of the figures?

Line 415: The statement “This uncertainty is deemed reasonable” confused me. Deemed reasonable by who? What metrics are being used? “reasonable” is a very vague term.

Acknowledgments: Make sure to include the SOCAT statement from the website that they ask you to include when you use their product (“The Surface Ocean CO2 Atlas (SOCAT) is an international effort, endorsed by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmosphere Study (SOLAS) and the Integrated Marine Biosphere Research (IMBeR) program, to deliver a uniformly quality-controlled surface ocean CO2 database. The many researchers and funding agencies responsible for the collection of data and quality control are thanked for their contributions to SOCAT.”)