The Black Sea Upwelling System: Analysis on the Western Shallow Waters
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper provides an in-depth climatological analysis of the Black Sea Upwelling system and discusses the newly proposed upwelling indices (CUTI and BEUTI), which provide an important scientific basis for understanding the dynamics of the Black Sea ecosystem. The research theme has high academic value and practical significance. However, there are some areas for improvement in the article:
1. Line 10, Abbreviations in the summary should read Coastal Upwelling Transport Index (CUTI).
2. Line 11, Biologically Effective Upwelling Transport Index (BEUTI).
3. Line 178, ‘Figure 2.’ should read ‘Figure 2.’ Note the formatting of the icons and similar issues should be corrected accordingly.
4. Line 185,186, Equations need to be edited in MathType.
5. Line 309, ‘Table 1.’ should read ‘Table 1.’
6. Line 457, ‘1982,’ should read ‘1982;’.
7. Line 464, year 1905 should not be bolded and similar formatting issues in the references should be corrected.
Comments on the Quality of English LanguageThis paper provides an in-depth climatological analysis of the Black Sea Upwelling system and discusses the newly proposed upwelling indices (CUTI and BEUTI), which provide an important scientific basis for understanding the dynamics of the Black Sea ecosystem. The research theme has high academic value and practical significance. However, there are some areas for improvement in the article:
1. Line 10, Abbreviations in the summary should read Coastal Upwelling Transport Index (CUTI).
2. Line 11, Biologically Effective Upwelling Transport Index (BEUTI).
3. Line 178, ‘Figure 2.’ should read ‘Figure 2.’ Note the formatting of the icons and similar issues should be corrected accordingly.
4. Line 185,186, Equations need to be edited in MathType.
5. Line 309, ‘Table 1.’ should read ‘Table 1.’
6. Line 457, ‘1982,’ should read ‘1982;’.
7. Line 464, year 1905 should not be bolded and similar formatting issues in the references should be corrected.
Author Response
Dear reviewer,
- For comments 1, 2 and 3, the necessary corrections were made, as the comments 1. Line 10, Abbreviations in the summary should read Coastal Upwelling Transport Index (CUTI); 2. Line 11, Biologically Effective Upwelling Transport Index (BEUTI) and 3. Line 178, ‘Figure 2.’ should read ‘Figure 2.’ Note the formatting of the icons and similar issues should be corrected accordingly.
- For "Line 185,186, Equations need to be edited in MathType": the equations 4 and 5 were edited in MathType and an additional paragraph were included as new lines 186 - 189. For equation 4 the reference Bakun, 1973 was included also. The phrase "Where, the x corresponds to the zonal component, and the y to the meridional component." was excluded from the text.
- For "Line 309, ‘Table 1.’ should read ‘Table 1.’" - the formatting has been corrected as well as the following comments 4. Line 457, ‘1982,’ should read ‘1982;’. and
- for the review comment "Line 464, year 1905 should not be bolded and similar formatting issues in the references should be corrected." - The formatting issues in the reference mentioned in line 464, such as the bolding of the year 1905, have been rectified in accordance with the review comment. as well as for similar references issues.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe CUTI index by definition is calculated by two components, but in the paper it was estimated by Ekman transport only, so it becomes similar to the Bakun Index. The alongshore sea surface height gradient is substantial in western part of the Black Sea and can be estimated by altimetry or tide gauge data. This correction probably decrease distinctly CUTI values and will change general conclusions. Also, there are not any mentions concerning a role of the wind stress curl-driven vertical velocity (Ekman pumping/sucking) in the coastal zone. It is advisable to explain these omissions.
Discussion and conclusions are frequently, but rather unwisely extend to the whole North-Western shelf or even the Black Sea entirely, though all the results are concerned to the Romanian coast alone. It relates also to the title of the paper, including Climatological Analysis, for which 30-year time-series is sufficient to present not only season cycle, but climatic tendencies as well. It is desirable to restrict geographical and meaning content of the investigation results.
General suggestion to use indices like CUTI or BEUTI, developed for large-scale ocean upwellings, for inland seas with specific oceanographic conditions is hardly efficient.
Terms ‘meromictic, hypolimnion, metalimnion, epilimnion’ are wide-spread in limnology, but in oceanography it nearly not used when describing marine environment.
Expression ‘The method uses planetary boundary layer theory and geostrophic wind approximation’ better to substitute by the reference of concrete ECWMF reanalysis.
It is desirable to insert equations into the text by means of an equation editor with corresponding explanations.
Author Response
Comments 1: The CUTI index by definition is calculated by two components, but in the paper it was estimated by Ekman transport only, so it becomes similar to the Bakun Index. The alongshore sea surface height gradient is substantial in western part of the Black Sea and can be estimated by altimetry or tide gauge data. This correction probably decrease distinctly CUTI values and will change general conclusions. Also, there are not any mentions concerning a role of the wind stress curl-driven vertical velocity (Ekman pumping/sucking) in the coastal zone. It is advisable to explain these omissions.
Response 1: Thank you for pointing this out. The reviewer correctly points out that the Coastal Upwelling Transport Index (CUTI) calculation in this study was simplified by focusing solely on Ekman transport, omitting the alongshore sea surface height gradient component. This simplification does indeed make the current CUTI estimates more akin to the Bakun Index. We acknowledge that the alongshore sea surface height gradient can be substantial in the western Black Sea and could be estimated using altimetry or tide gauge data. However, incorporating this component into the CUTI calculation is beyond the scope of the present study due to inconsistencies observed between the available tide gauge data and the in-situ temperature and salinity measurements. Furthermore, the reviewer highlights the absence of discussion regarding the role of wind stress curl-driven vertical velocity (Ekman pumping/sucking) in the coastal zone. We acknowledge this omission and recognize the potential importance of Ekman pumping/sucking in influencing upwelling dynamics. However, a detailed investigation of this process requires high-resolution wind data and sophisticated modeling techniques, which are not within the scope of this climatological analysis. Furthermore, we plan to address these limitations in future research by: Incorporating alongshore sea surface height gradients: We will explore the use of altimetry data to estimate the alongshore sea surface height gradient and incorporate it into the CUTI calculation. This will provide a more comprehensive assessment of upwelling dynamics in the western Black Sea, as well as investigate Ekman pumping/sucking to conduct high-resolution modeling studies to examine the role of wind stress curl-driven vertical velocity in the coastal upwelling process. This will enhance our understanding of the complex interplay between wind forcing and upwelling dynamics in the region and to understand in depth the nearshore dynamics that can influence other processes).
Comment 2: Discussion and conclusions are frequently, but rather unwisely extend to the whole North-Western shelf or even the Black Sea entirely, though all the results are concerned to the Romanian coast alone. It relates also to the title of the paper, including Climatological Analysis, for which 30-year time-series is sufficient to present not only season cycle, but climatic tendencies as well. It is desirable to restrict geographical and meaning content of the investigation results.
Response 2: The reviewer's comment regarding the broad geographical scope of the discussion and conclusions in relation to the specific focus on the Romanian coast is well-taken. The way the discussion and conclusions are currently written might unintentionally suggest that the results of the study apply to a larger area than the data actually supports. To address this, the manuscript was revised to ensure that the interpretations and generalizations are explicitly confined to the Romanian coastal region, which is the primary focus of the study. Additionally, the title was refined to better reflect the specific geographical context of the research. The term "Climatological Analysis" will be retained, as the 30-year time series used in the study is indeed sufficient to characterize both seasonal cycles and long-term climatic trends. However, the title will be modified to explicitly indicate the focus on the Romanian coast (Western Black Sea shallow waters), ensuring clarity and accuracy in conveying the scope of the investigation.
Com3: General suggestion to use indices like CUTI or BEUTI, developed for large-scale ocean upwellings, for inland seas with specific oceanographic conditions is hardly efficient.
Response 3: We agree with the reviewer's concern about the applicability of indices like CUTI and BEUTI, which were developed for large-scale ocean upwellings, to the specific conditions of an inland sea like the Black Sea is valid. The Black Sea's unique characteristics, such as its limited wind-driven upwelling, strong stratification, and significant riverine influence, distinguish it from the open ocean environments for which these indices were originally designed. We included the paragraph lines 412 - 424: "While the Coastal Upwelling Transport Index (CUTI) and Biologically Effective Upwelling Transport Index (BEUTI) have proven valuable in open ocean settings, their application to the semi-enclosed and highly stratified Black Sea necessitates a nuanced interpretation. Directly applying these indices, originally designed for large-scale, wind-driven upwelling systems, may not fully capture the complex upwelling dynamics influenced by factors such as riverine input and unique bathymetry. Therefore, validation with in-situ observations of upwelling events, as presented in this study, is crucial for assessing the accuracy and applicability of CUTI and BEUTI within the Black Sea context. Despite these limitations, these indices remain valuable tools for understanding the relative variability and seasonal patterns of upwelling along the Romanian Black Sea coast. By focusing on comparative analyses and trend identification rather than absolute quantification, we can utilize CUTI and BEUTI to gain insights into the drivers and potential ecological impacts of upwelling in this unique marine environment."
Com4: Terms ‘meromictic, hypolimnion, metalimnion, epilimnion’ are wide-spread in limnology, but in oceanography it nearly not used when describing marine environment.
Response 4: We have, accordingly changed the meromictic terminology with the oceanographic term: "strong stratified ".
Com5: Expression ‘The method uses planetary boundary layer theory and geostrophic wind approximation’ better to substitute by the reference of concrete ECWMF reanalysis.
Response5: Agree. I have, accordingly, modified the phrase and included the citation to emphasize this point. Lines: 172 - 174 "The coastal upwelling index time series is calculated using monthly average wind fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis [19]..." Also, for Copernicus Marine Services, I included the complete citation. The final references:
19.Hersbach, H.; Bell, B.; Berrisford, P.; Hirahara, S.; Horányi, A.; Muñoz‐Sabater, J.; Nicolas, J.; Peubey, C.; Radu, R.; Schepers, D.; Simmons, A.; Soci, C.; Abdalla, S.; Abellan, X.; Balsamo, G.; Bechtold, P.; Biavati, G.; Bidlot, J.; Bonavita, M.; De Chiara, G.; Dahlgren, P.; Dee, D.; Diamantakis, M.; Dragani, R.; Flemming, J.; Forbes, R.; Fuentes, M.; Geer, A.; Haimberger, L.; Healy, S.; Hogan, R.J.; Hólm, E.; Janisková, M.; Keeley, S.; Laloyaux, P.; Lopez, P.; Lupu, C.; Radnoti, G.; de Rosnay, P.; Rozum, I.; Vamborg, F.; Villaume, S.; Thépaut, J-N. (2017): Complete ERA5 from 1940: Fifth generation of ECMWF atmospheric reanalyses of the global climate. Copernicus Climate Change Service (C3S) Data Store (CDS). (Accessed on 10-11-2023)
20. Grégoire, M.; Vandenbulcke, L.; Capet, A. (2020). Black Sea Biogeochemical Reanalysis (CMEMS BS-Biogeochemistry) (Version 1) set. Copernicus Monitoring Environment Marine Service (CMEMS). https://doi.org/10.25423/CMCC/BLKSEA_REANALYSIS_BIO_007_005_BAMHBI. https://marine.copernicus.eu/ (accessed on 10 November 2023).
Com6: It is desirable to insert equations into the text by means of an equation editor with corresponding explanations.
Response 6: Thank you for pointing this out. I agree with this comment. All equations were edited using MathType and explanations of symbols were included. Lines 182 - 193.
