The manuscript presents an extensive data-series of valuable data of air-sea exchange using EC technique as well as bulk calculated fluxes. The data shows the seasonal cycle and net excheange over one region in the Baltic Sea and is a valuable analysis. Some significant clarifications are needed to enrure full understanding of the use of the different methods and the accuracy.

Comments: The gas transfer velcocity is controlled bu severla factors (line 45 page 2), this is of particular importance for a coastal site and should be further discussed (see eg Garbet et al ., 2014).

Page 7, line 160. The choice of accurate data is unclear (26% of the time), is this due to wind directions only, what about fluxes below detection limit and other errors in the data. Is the non-stationarity the only quality control criteria?

Page 8,line 175: The parameteirsation is stated to be site specific, why is this? What makes the parameterisation site specific. it is enerally thought that the transfer coefficient could be generally described in terms of forcing processes.

Line 180: three sources of data: EC, Bulk and reconstructed, it is unclear how much data of each category and the distribution of situations. Does this in some way bias the analysis?

section 3.4: How are the large drops in salinity explained?

section 3.5: How can the variability in Chl-a be explained?

section 3.7: Also the variability in the wind is relevant, this should be discussed.

Page 13, line 340: Here upwelling is discussed as one explanation, it would require some further discussion on the relevance and frequency of upwelling at this site.

line 344: What is here meant by atmospheric deposition (of what)?

Line 352: Uncertainty estimates on these numbers should be discussed. In addition there are several other estimates to compare with, based on observations and/or modelling.

Appendix A: The EC method, Again, it is unclear if the non-stationalrity is enough as quality criteria (what about detection limit).

Two different criteria seems to be used for EC data (for budgets and estimates of transfer velocity). This should be further described and discussed.

Description of error estimate is unclear.

Garbe C S et al 2014 Ocean-Atmosphere Interactions of Gases and Particles eds P Liss and M

Johnson (Springer-Verlag) 55-112

Suggested upwelling literature:

Lehmann, A., Myrberg, K., 2008. Upwelling in the Baltic Sea - A review. J. Mar. Syst. 74, S3–S12. https://doi.org/10.1016/j.jmarsys.2008.02.010. 

Lehmann, A., Myrberg, K., Hoflich, K., 2012. A statistical approach to coastal upwelling in the Baltic Sea based on the analysis of satellite data for 1990–2009. Oceanologia 54, 369–393. https://doi.org/10.5697/oc.54-3.369. Norman, M., Parampil, S.R., Rutgersson, A., Sahl´ee, E., Norman, M.,

Parampil, S.R., Rutgersson, A., Sahl´ee, E., 2013. Influence of coastal upwelling on the air–sea gas exchange of CO 2 in a Baltic Sea Basin. Tellus B Chem. Phys. Meteorol. 65, 1–16. https://doi.org/10.3402/tellusb.v65i0.21831. 

Zhang, S., L. Wu, J. Arnqvist^, C. Hallgrenand A. Rutgersson. Mapping coastal upwelling in the Baltic Sea from 2002 to 2020 using remote sensing data. Int. J. of Appl. Earth Observation and Geoinformatics, Volume 114, November 2022, 103061, https://doi.org/10.1016/j.jag.2022.103061