Dear Camille Richon,
I have read the answers you have provided to the comments of both reviewers and based on that I encourage you to submit a revised version of your work. Both reviewers mention important points of improvements that need to be carefully tackled. For instance, both reviewers request that you further the validation exercise of the ocean model by notably proposing quantitative metrics. We are not asking you to repeat the validation exercise performed in Richon et al (2017) but rather to summarize that exercise by for instance adding a table showing the performance of the model (e.g RMS, Bias,..) and extending this validation using other data sets (e.g. satellite data, climatologies). Moreover, reviewer 1 has serious criticisms concerning the quality of the P deposition provided by the atmospheric model (even the averaged value provided by the model seems critical). You mention in your answer that this Pcomb deposition provided by LMDz-INCA is the only spatial data available so far and you agree that the quality may be improved. We have then the feeling that you are rather performing a sensitivity studies of your model results to Pcomb deposition. In that case, I would agree with reviewer 1 that it would have been needed to use different sets of Pcomb (e.g. perturbing the conditions based for instance on an assessment of the potential error/inter-annual variability). I would like that you clearly acknowledge the limitations of your approaches and that you make clear which robust messages can be derived from your work giving the limitations mentioned above.
The revised version will be sent for a second round to the reviewers.
I thank you so much for all your efforts in improving your manuscript.
Kind regards,
Marilaure Grégoire

Dear Dr. Richon,
The two reviewers have analyzed the revised version of your manuscript entitled “Modeling the biogeochemical impact of atmospheric phosphate deposition from desert dust and combustion sources to the Mediterranean Sea “. Both acknowledge the improvements made in this revised version. Especially efforts in showing the performances of the model were appreciated. However, one of the reviewers (reviewer 2) still have concerns concerning the coarse resolution of the atmospheric model (LMDz) used in the simulations and hence on its capacity in providing sound estimations of Pdust and Pcomb for deriving robust conclusions. He/she agrees that an ensemble approach would be probably too much demanding but he/she recommends to assess uncertainty in model simulations due to the coarse atmospheric forcings by running the model for different years and checking that your conclusions still hold. Probably, considering the very coarse spatial resolution, daily forcings for Pcomb are not absolutely needed (figure 3 does not show a significant seasonal variability due to the constancy of the emission of anthropogenic P) and monthly forcing would allow running the model for several years and not only for 2005.
The main message of your work is that the deposition of phosphate from combustion has to be taken into account in future modeling studies of the Mediterranean Sea because it is dominant at the scale of the Mediterranean sea, and in some regions it represents more than 10 times that from dust with effects 10 times higher as well. The reviewer would like to see some more proofs that it is a general feature and not only the case in 2005.
You mentioned that the value of Pdust for 2005 lies in the range of the interannual variability during 1997-2012. However, we lack this information for Pcomb which seems to be available as well (You only mention the wildfire emissions what about the combustion due to anthropogenic activities). At least, I guess that a graph showing how the value used for Pcomb in your simulations lies in the interannual variability would be helpful as well as an information on the interannual variation of the spatial patterns. It will allow to assess whether 2005 is a typical year or not. It will also show how your message mentioned in the abstract that Pcomb is dominant compared to Pdust in 2005 holds for the other years.
Here below, you will find some other comments that I have when reading your revised version.
I thank you for your efforts in answering clearly the last concerns from reviewer 2 and mine provided here below.
Kind regards,

Marilaure Grégoire

Abstract: Lines 10-11: Please clarify how this conclusion holds for the other years.
Introduction, line 31-33: ‘… for marine biology..” I would be more specific.
Line 42: What do you mean by “constrain”?
Line 64: “. The Mediterranean Sea is also a hot–spot for climate change impacts (Lejeusne et al., 2010)” This sentence seems to be a little bit disconnected from the rest of the paragraph. I suggest that you either remove it or that you detail somehow the link between climate change and aerosols emission.
Lines 67-69: please give a reference
Lines 76-80: Please synthetize in 2-3 lines the main outcome of Richon et al 2017
Line 81: I would say: “..;by further considering the contribution of P from combustion sources in addition to that from anthropogenic…”
Line 101: “the authors” please specify who? Hamon et al ., 2015
Line 113: I would not say that PISCES is a Monod-type model but rather that the uptake of nutrient (e.g; nitrate, ammonium, phosphate, iron and silicate) by phytoplankton is governed by a Monod-type model. Besides, I would start by a general description of PISCES (e.g. lines 118-122) then I would go to specific feature of the model (e.g. description of nutrient uptake formulation).
Line 118: trophic level and not biological levels.
Line 135: “Biogeochemical variables are prognostically calculated instead of being read from forcing files”. This sentence is not necessary (you have a model so the model computes the state variables.
Line 136: “Biogeochemical characteristics of the latest version of the NEMOMED12/PISCES model are evaluated in Richon et al. (2017). » This sentence is similar to the next one.
Please uniformize the definition of chlorophyll a. Sometimes you use Chl a, sometimes chlorophyll a.
Lines 190-191: “The Pcomb deposition fields from LMDz–INCA used here have a coarser resolution than for Pdust of 1.27◦ in latitude by 2.5◦ in longitude”. This is confusing since we are told that the study wants to have consistent atmospheric inputs provided by the same model (see lines 162-164). Please clarify.
Line201: “.. which leads to a general agreement of modeled surface P concentrations with …” to which model are you referring? I guess that this is a global estimation? Please specify.
Lines 207-208: P surface concentrations and deposition produced by LMD model? If yes, please link appropriately with Lines 209- which refer to LMDz performances as well because as it is written we have the feeling that these two parts are not related to the same model evaluation.
Line 255: something is missing in the sentence. Please reformulate.

Line 310: “.. available at a too coarse time resolution to perform oceanic simulations..”. Please justify because looking at figure 3 we do not have the feeling that Pcomb has significant variability.

Line 331: this is clearer to use Table 3 instead of This table.

Line 344: You are not really assessing the impact of atmospheric deposition on the phosphate budget
but rather on the phosphate surface concentration. So I would remove budget.

Line 446: Please define PM2.5 and PM 10.I do not think that it has been already defined above.

Lines 451-454: “Although total mass deposition of phosphorus from desert dust exceeds that of combustion aerosols, the latter are much more soluble than lithogenic dust. » Please clarify. In the abstract we are told the reverse. Do you mean that the higher flux in the abstract results from the use of different solubility coefficients?


Legend figure 5: “..; map represents the 50 % Pdust proportion limit” compared to 2005 for Pcomb? Or 1997-2012 for Pcomb as well? Please clarify.
Figure 9: legend: I guess that it is the reference primary production and not the reference PO4.
Table 3: “Relative atmospheric contribution (%) to total PO4 supply in different sub–basins of atmospheric sources”. I would remove “of atmospheric sources”?

Dear Dr. Richon,
I have read the revised version of your manuscript as well as the answers you have provided to all the remaining comments and I found that you have successfully addressed all of them. Therefore, I am pleased to accept your manuscript for publication in Biogeosciences.
Thank you for your efforts and for having submitted your work to Biogeosciences.
Kind regards,
Marilaure Grégoire