the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Aug 2023
Eddy-induced chlorophyll profile characteristics and underlying dynamic mechanisms in the South Pacific Ocean
Abstract. Many studies have consistently demonstrated that the near-surface phytoplankton chlorophyll (Chl) levels in anticyclonic eddies (AEs) are higher than in cyclonic eddies (CEs) in the South Pacific Ocean (SPO) using remote sensing data, which is attributed to higher phytoplankton biomass or physiological adjustments in AEs. However, the characteristics of the Chl profile induced by mesoscale eddies and their underlying dynamic mechanism have not been comprehensively studied by means of field measurement. In this study, we mainly utilized BGC-Argo data to investigate the relationships between Chl levels and environmental factors (CPhyto, Nitrate, Temperature and Light) and the underlying dynamic mechanisms of mesoscale eddies in SPO. Our findings showed that, the elevated Chl levels in AEs primarily result from increased phytoplankton biomass within the Mixed Layer Depth (MLD), which is induced by enhanced nutrient availability due to the deepening MLD in AEs. At depths ranging from 50 m to 110 m (the depth between the bottom of the mixed layer and pycnocline), the dominant factor affecting higher Chl levels in CEs is the physiological adaptation of phytoplankton, driven by reduced temperature and light availability. Between 110 m and 150 m (near the depth of pycnocline or bottom of the euphotic zone), both phytoplankton biomass induced by eddy pumping and physiological adjustments for lower light and temperature contributed to higher Chl levels in CEs. At depths exceeding 150 m (beyond the euphotic zone), higher Chl in AEs is primarily influenced by phytoplankton biomass as a result of the downwelling by eddy pumping. To a certain extent, this work would advance our comprehensive understanding of the physical-biological interactions of mesoscale eddies and their impacts on primary productivity throughout the water column, which has important implications for accurately assessing the biogeochemical processes and ocean carbon cycle.
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RC1: 'Comment on egusphere-2023-1735', Anonymous Referee #1, 04 Oct 2023
General comments :
In part 2.3 the authors mentioned that they are using BGC-Argo delayed mode data for their study. Presently, the chlorophyll-A has not been qualified in delayed mode in the South Pacific area (https://biogeochemical-argo.org/cloud/document/implementation-status/BGC_summary.pdf) . So a very important comment, the authors should really improve the description of the dataset first.
The BGC-Argo chlorophyll-A qualification is very heterogeneous presently from a float to another and it is not mentioned in the manuscript. Moreover, there is no mention in the manuscript of the major feature of the Chlorophyll-A measurements, based on fluorescence. According to me it requires careful use of this Chlorophyll-A dataset without ignoring this feature.
I think that dealing with this issue is a prerequisite before trying to compare BGC-Argo Chlorophyll-A profiles with satellite data. The chlorophyll-A BGC-Argo, based on fluorescence data, are affected by the non photochemical quenching and this can have a huge impact on the Chlorophyll-A estimation mainly at the surface.
It is not clear in the manuscript whether the authors are using raw data from the BGC-Argo dataset or the adjusted fields (corrected in real-time of the quenching); this should be mentioned as a first step. Then, depending on the option chosen (raw vs. adjusted), the authors must describe their treatment of the data and explain in details the quality control that they are applying on the data (it is mentioned, but there is no details).
Comments on the Figures :
Considering that the MLD is close to 50m, it is hard to see that the figure 2 highlights any difference between AES and CES in CHL concentration as mentioned in the text, a zoom of the figure could be added.
Still on the BGC-Argo dataset, the figure 4c. is not obviously illustrating an increase of nutrients in the area of 50m to 110m as mentioned by the authors, from AES to CES. If the BGC-Argo data nitrate profiles are qualified in delayed mode as mentioned by the authors, they are provided with uncertainties and these uncertainties are within +-1 micromol per kg. I think that the authors should also consider carefully the uncertainties of the dataset before concluding.
Based on these different remarks, to further evaluate whether this study is relevant, as it is presently difficult to check exactly what data are used, how they are qualified and whether the data are used correctly, the authors should consider revisiting deeply their "data" part (http://www.argodatamgt.org/) . It could be also useful to mention the Argo WMO of the floats that they are using in their study. These are the reasons why I think that this manuscript needs major revision before being reconsidered.
Citation: https://doi.org/10.5194/egusphere-2023-1735-RC1 -
AC3: 'Reply on RC1', Meng Hou, 24 Oct 2023
Dear Reviewer:
Thank you very much for your crucial and constructive suggestions, which let us find the shortcomings in our study, and we also learned more knowledge from your comments. Your comments helped us a lot, and solved the problem where we were confused (the chlorophyll level measured by BGC-Argo does not meet our expectations in the ocean surface layer). We answered your comments in the following pages, and revised the manuscript, all the changes are highlighted in red.
General comments:
Comment 1: In part 2.3 the authors mentioned that they are using BGC-Argo delayed mode data for their study. Presently, the chlorophyll-A has not been qualified in delayed mode in the South Pacific area. So a very important comment, the authors should really improve the description of the dataset first.
Response: Thanks for your extremely professional suggestion. For the data usage problem mentioned in part 2.3, we found that we mistakenly believed that 'Quality controlled data' was equivalent to 'delayed mode data' by reading relevant articles and websites where the data came from (https://www.seanoe.org/data/00311/42182/#96562). The chlorophyll-a data we used produced by BGC-Argo were 'Quality controlled data'.
In the downloaded dataset (Quality controlled data), there are two types of chlorophyll-a data, one labeled 'CHLA' and another labeled 'CHLA_ADJUSTED'. The chlorophyll-a data we used originally is labeled 'CHLA', and this data has not been optimized for non-photo-chemical quenching (NPQ) effects. The chlorophyll-a data labeled 'CHLA_ADJUSTED' is adjusted data and has been optimized for NPQ effects. So, we used the adjusted data of chlorophyll-a redone the experiment.
We rephrased these sentences : “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used” (Page 4, line 114).
Comment 2: The BGC-Argo chlorophyll-A qualification is very heterogeneous presently from a float to another and it is not mentioned in the manuscript. Moreover, there is no mention in the manuscript of the major feature of the Chlorophyll-A measurements, based on fluorescence. According to me it requires careful use of this Chlorophyll-A dataset without ignoring this feature. I think that dealing with this issue is a prerequisite before trying to compare BGC-Argo Chlorophyll-A profiles with satellite data.
The chlorophyll-a measured by BGC-Argo, based on fluorescence data, is affected by the non-photochemical quenching and this can have a huge impact on the Chlorophyll-a estimation mainly at the surface. It is not clear in the manuscript whether the authors are using raw data from the BGC-Argo dataset or the adjusted fields (corrected in real-time of the quenching); this should be mentioned as a first step.
Then, depending on the option chosen (raw vs. adjusted), the authors must describe their treatment of the data and explain in details the quality control that they are applying on the data (it is mentioned, but there is no details).
Response:
Thanks for your suggestion. The ratio of chlorophyll-a fluorescence (measured by the sensors) to chlorophyll-a concentration varies as a function of non-photo-chemical quenching (NPQ) [1]. Chlorophyll fluorescence of phytoplankton decreases when exposed to ambient light. The chlorophyll-a data labeled 'CHLA_ADJUSTED' we used has been optimized for NPQ effects [2]. (Page 4, line114).
The temperature data we used is labeled 'TEMP_ADJUSTED'. Some times, the data labeled 'DATA_ADJUSTED' is lacked in some floats, then we will use data labeled 'DATA' with mode 'A'. For nitrate data, according to the manual, the data we used is labeled 'NITRATE' with mode 'A' [3]. Similarly, bbp, and PAR data with mode 'A' were used. The data labeled 'DATA_ADJUSTED' or with mode 'A' are adjusetd data. (Page 4, line115).
Then, we converted the adjusted profile data into vertical profile data with an accuracy of 1m according to PRES (sea water pressure) data, and then smoothed them with a 15-point moving mean filter and median filter to remove noises. Finally, we plotted the profiles in eddies of different polarity (Page 5, line128).
In the end, we redone the experiment using adjusted data, and all the tables and figures are updated. The variation of the experimental results is mainly concentrated in the Mixed Layer Depth, the second paragraph of part 3.3 and the second paragraph of part 4.
We rephrased these sentences, and added references : “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects...)(Page4 line114)”; “Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises. (Page4 lines125-129)”
Comments on the Figures:
Comment 1: Considering that the MLD is close to 50m, it is hard to see that the figure 2 highlights any difference between AEs and CEs in CHL concentration as mentioned in the text, a zoom of the figure could be added.
Response: Thanks for your suggestion. We added a zoom of figure 2 from 0-50m in supporting information, and the relationship of Chl concentration in AEs and CEs can also be seen in Table 1.
Comment 2: Still on the BGC-Argo dataset, the figure 4c. is not obviously illustrating an increase of nutrients in the area of 50m to 110m as mentioned by the authors, from AEs to CEs. If the BGC-Argo data nitrate profiles are qualified in delayed mode as mentioned by the authors, they are provided with uncertainties and these uncertainties are within +-1 micromol per kg. I think that the authors should also consider carefully the uncertainties of the dataset before concluding.
Based on these different remarks, to further evaluate whether this study is relevant, as it is presently difficult to check exactly what data are used, how they are qualified and whether the data are used correctly, the authors should consider revisiting deeply their "data" part (http://www.argodatamgt.org/). It could be also useful to mention the Argo WMO of the floats that they are using in their study.
Response:
Thanks for your suggestion. As mentioned previously, the data we used is labeled 'NITRATE' with mode 'A'. The small difference of nitrate concentrations between AEs and CEs in the South Pacific Ocean (SPO) is due mainly to the oligotrophic nature of the SPO, where nitrate concentrations are inherently low. On the other hand, according to statistics, there are more than 400 nitrate profiles in this area. Therefore, we believe that these nitrate data with mode 'A' are reliable. The nitrate data also used in other paper [4].
We added BGC-Argo's ID number in this manuscript (6901659，6901660，6901687，6902701), as the unique identifier that they can be found on the website: https://biogeochemical-argo.org/data-access.php (Page 4, line 113)
We rephrased these sentences: “There are 4 BGC-Argo floats were used in our study (ID: 6901659，6901660，6901687 and 6902701), they can be found on the website: https://biogeochemical-argo.org/data-access.php.”
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
We also rephrased the second paragraph of part 3.3, the second paragraph of part 4 and the second paragraph of part 5 due to the modulation of data (chlorophyll, BBP).
The second paragraph of part 3.3: “In MLD, the concentration of CPhyto in AEs was found to be higher compared to CEs, which was consistent with the Chl results. The Chlʹ=21% and the Cphytoʹ=5.1% in MLD, suggest that although the Chl in AEs was much higher than in CEs, the biomass was not significantly higher (Figure 3, Table 1). The θ profile precisely explains this phenomenon, θʹ=15.6% in this layer, indicating that the pigment concentration per individual phytoplankton cell in AEs is higher than in CEs. That is, in MLD, the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton, and induced the higher of Chlʹ than Cphytoʹ. ”
The second paragraph of part 4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light. Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth (Figure 4c). Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (Figure 4a) (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the Chlʹ lower than Cphytoʹ. However, the opposite situation has emerged currently, the Chlʹ is higher than Cphytoʹ in MLD (Table 1). This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (Table 1).”
The second paragraph of part 5: “In MLD, AEs have a higher Chl concentration than CEs, is driven by both biomass and physiological adjustment of phytoplankton, and the physiological adjustment plays a predominate role. As a result of the convergent subsidence, AEs deepened MLD and can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. The deepening MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption, and the higher temperature in AEs plays a little negative contribution.”
References:
[1]Bittig, Henry C., et al. "A BGC-Argo guide: Planning, deployment, data handling andusage." Frontiers in Marine Science 6 (2019): 502.
[2]Schmechtig, C., et al. "Bio-Argo quality control manual for the Chlorophyll-A concentration, Ifremer." (2018).
[3]Johnson, Kenneth, et al. "BGC-Argo quality control manual for nitrate concentration." (2021).
[4]Xiu, P., & Chai, F. (2020). Eddies affect subsurface phytoplankton and oxygen distri-butions in the North Pacific Subtropical Gyre. Geophysical Research Letters, 47, e2020GL087037. https://doi. org/10.1029/2020GL087037
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AC2: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
We updated our reply, and fixed some errors.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues：“… and the distribution of sea surface Chl concentration in eddies of different polarity was investigated”
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence. “Our study indicate that the characteristics of Chl profiles and their influencing factors vary across different depths in seawater. The contribution of phytoplankton biomass and physiological regulation to Chl concentration is different at different depths. Therefore, it is not sufficient and can not provide complete information to study the effect of eddies on Chl only using remote sensing data. This study filled this gap, and will have significant implications for enhancing our understanding of the biogeochemical processes and carbon cycle associated with eddies.” (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence:“The dataset provided by AVISO for identifying and tracking eddies from January 2000 to August has been selected. The eddies obtained through the interpolation algorithm and amplitude exceeding less than 1cm and lifetime less than 10 days have been excluded to reduce errors.” (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m. We rephrased the sentence:“Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises.”(Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1): “CPhyto (phytoplankton carbon) was calculated from BBP which is defined as: CPhyto = 0.19 × (53607× BBP700 × (700/550) + 2.5), it represents the quantity of phytoplankton biomass.” ; “the higher the value of , means the greater the Chl concentration in AEs compared to CEs. indicates the mean Chl concentration in AEs, and represents the mean Chl concentration in CEs, while means Chl mean values outside eddies. ” (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1. We rephrased the sentence:“In MLD, the Chl concentration in AEs was slightly higher than that in CEs” (Page 7, line 174).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence:“In general, the phytoplankton biomass was mainly affected by nitrate concentration (Sukigara, 2022). This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.” (Page 10, lines 239-242).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response: Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence：“This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.”
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. We add a reference.
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference.
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. Due to data modification, we rephrased the second section of part4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light (Poppeschi et al., 2022). Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the lower than . However, the opposite situation has emerged currently, the is higher than in MLD. This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (He et al., 2021).”
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence: “Therefore, it’s difficult for CEs to carry the eutrophic water to surface from the deep ocean through eddy pumping, however, AEs can contact more nutrients because of the deepening MLD.”(Page 12, lines 301-302).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence: “In this study, we mainly utilized biogeochemical-argo (BGC-Argo) data to investigate the relationships between Chl levels…” (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence: “and environmental factors (CPhyto, nitrate, temperature and light) and the underlying dynamic mechanisms of mesoscale eddies in SPO.” (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3. “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used”
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion.
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
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AC3: 'Reply on RC1', Meng Hou, 24 Oct 2023
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RC2: 'Comment on egusphere-2023-1735', Anonymous Referee #2, 08 Oct 2023
Comment on “Eddy-induced chlorophyll profile characteristics and underlying dynamic mechanisms in the South Pacific Ocean”
by Meng Hou, Jie Yang, Ge Chen, Guiyan Han, Yan Wang and Kai Wu
General comments:
The study analyses the impact of dynamic processes within mesoscale eddies on chlorophyll, biomass, nitrate, temperature, and light in the upper ocean of the South Pacific. The aim is to decipher the relationship between physical-biological interactions of mesoscale eddies and primary productivity. Hereby, chlorophyll can be used as an index for marine primary production. The study is based on measurements by BGC-Argo floats and satellite measurements in the South Pacific Ocean. The report addresses relevant scientific questions and gives new insight into the influence of mesoscale eddies on primary productivity at different levels in the upper ocean. My main concerns are about the presentation and discussion of the data. The figures need to be improved in order to better understand the authors' conclusions. In the discussion, it is sometimes difficult for the reader to distinguish the results of this study from previous studies, which has to be clarified. More explanations in the methods would be great. Conclusions are stated clearly. I recommend publication of this manuscript after major revision. Please see my comments below in the specific comments.
Specific comments:
Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Page 10, line 242-244: In case this is common knowledge a reference is missing.
Page 11, line 253-258: Reference is missing for the statement.
Page 11, line 256-258: Please rephrase.
Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Figure 3 and 4: Same scale of the y axis would be helpful for comparison.
Technical comments:
Page 1, line 16: Please explain the acronym “BGC”
Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Page 3, line 71: “driver” – Should it say “drive”?
Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used. for this study.
Page 9, line 208: Please either delete “although” or “while”.
Page 9, line 212: Do you mean “lower rate”?
Page 11, line 249: Blank missing.
Page 12, line 292, 293: Should say “feeds” and “attracts”
Citation: https://doi.org/10.5194/egusphere-2023-1735-RC2 -
AC1: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues.
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m (Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1) (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1 (Page 7, line 173).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 10, lines 238-241).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response:
Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence.
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. This is one of a conclusion in our study, we have rephrased the sentence (Page 10, lines 238-241).
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference (Page 11, line 260).
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 11, lines 256-258).
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 300-301).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3.
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion. We rephrased the sentence, according to the latest data, it means the value Chlʹ is higher than Cphytoʹ (Page 9, line 214).
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
-
AC2: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
We updated our reply, and fixed some errors.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues：“… and the distribution of sea surface Chl concentration in eddies of different polarity was investigated”
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence. “Our study indicate that the characteristics of Chl profiles and their influencing factors vary across different depths in seawater. The contribution of phytoplankton biomass and physiological regulation to Chl concentration is different at different depths. Therefore, it is not sufficient and can not provide complete information to study the effect of eddies on Chl only using remote sensing data. This study filled this gap, and will have significant implications for enhancing our understanding of the biogeochemical processes and carbon cycle associated with eddies.” (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence:“The dataset provided by AVISO for identifying and tracking eddies from January 2000 to August has been selected. The eddies obtained through the interpolation algorithm and amplitude exceeding less than 1cm and lifetime less than 10 days have been excluded to reduce errors.” (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m. We rephrased the sentence:“Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises.”(Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1): “CPhyto (phytoplankton carbon) was calculated from BBP which is defined as: CPhyto = 0.19 × (53607× BBP700 × (700/550) + 2.5), it represents the quantity of phytoplankton biomass.” ; “the higher the value of , means the greater the Chl concentration in AEs compared to CEs. indicates the mean Chl concentration in AEs, and represents the mean Chl concentration in CEs, while means Chl mean values outside eddies. ” (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1. We rephrased the sentence:“In MLD, the Chl concentration in AEs was slightly higher than that in CEs” (Page 7, line 174).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence:“In general, the phytoplankton biomass was mainly affected by nitrate concentration (Sukigara, 2022). This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.” (Page 10, lines 239-242).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response: Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence：“This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.”
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. We add a reference.
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference.
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. Due to data modification, we rephrased the second section of part4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light (Poppeschi et al., 2022). Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the lower than . However, the opposite situation has emerged currently, the is higher than in MLD. This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (He et al., 2021).”
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence: “Therefore, it’s difficult for CEs to carry the eutrophic water to surface from the deep ocean through eddy pumping, however, AEs can contact more nutrients because of the deepening MLD.”(Page 12, lines 301-302).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence: “In this study, we mainly utilized biogeochemical-argo (BGC-Argo) data to investigate the relationships between Chl levels…” (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence: “and environmental factors (CPhyto, nitrate, temperature and light) and the underlying dynamic mechanisms of mesoscale eddies in SPO.” (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3. “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used”
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion.
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
-
AC1: 'Reply on RC2', Meng Hou, 24 Oct 2023
Status: closed
-
RC1: 'Comment on egusphere-2023-1735', Anonymous Referee #1, 04 Oct 2023
General comments :
In part 2.3 the authors mentioned that they are using BGC-Argo delayed mode data for their study. Presently, the chlorophyll-A has not been qualified in delayed mode in the South Pacific area (https://biogeochemical-argo.org/cloud/document/implementation-status/BGC_summary.pdf) . So a very important comment, the authors should really improve the description of the dataset first.
The BGC-Argo chlorophyll-A qualification is very heterogeneous presently from a float to another and it is not mentioned in the manuscript. Moreover, there is no mention in the manuscript of the major feature of the Chlorophyll-A measurements, based on fluorescence. According to me it requires careful use of this Chlorophyll-A dataset without ignoring this feature.
I think that dealing with this issue is a prerequisite before trying to compare BGC-Argo Chlorophyll-A profiles with satellite data. The chlorophyll-A BGC-Argo, based on fluorescence data, are affected by the non photochemical quenching and this can have a huge impact on the Chlorophyll-A estimation mainly at the surface.
It is not clear in the manuscript whether the authors are using raw data from the BGC-Argo dataset or the adjusted fields (corrected in real-time of the quenching); this should be mentioned as a first step. Then, depending on the option chosen (raw vs. adjusted), the authors must describe their treatment of the data and explain in details the quality control that they are applying on the data (it is mentioned, but there is no details).
Comments on the Figures :
Considering that the MLD is close to 50m, it is hard to see that the figure 2 highlights any difference between AES and CES in CHL concentration as mentioned in the text, a zoom of the figure could be added.
Still on the BGC-Argo dataset, the figure 4c. is not obviously illustrating an increase of nutrients in the area of 50m to 110m as mentioned by the authors, from AES to CES. If the BGC-Argo data nitrate profiles are qualified in delayed mode as mentioned by the authors, they are provided with uncertainties and these uncertainties are within +-1 micromol per kg. I think that the authors should also consider carefully the uncertainties of the dataset before concluding.
Based on these different remarks, to further evaluate whether this study is relevant, as it is presently difficult to check exactly what data are used, how they are qualified and whether the data are used correctly, the authors should consider revisiting deeply their "data" part (http://www.argodatamgt.org/) . It could be also useful to mention the Argo WMO of the floats that they are using in their study. These are the reasons why I think that this manuscript needs major revision before being reconsidered.
Citation: https://doi.org/10.5194/egusphere-2023-1735-RC1 -
AC3: 'Reply on RC1', Meng Hou, 24 Oct 2023
Dear Reviewer:
Thank you very much for your crucial and constructive suggestions, which let us find the shortcomings in our study, and we also learned more knowledge from your comments. Your comments helped us a lot, and solved the problem where we were confused (the chlorophyll level measured by BGC-Argo does not meet our expectations in the ocean surface layer). We answered your comments in the following pages, and revised the manuscript, all the changes are highlighted in red.
General comments:
Comment 1: In part 2.3 the authors mentioned that they are using BGC-Argo delayed mode data for their study. Presently, the chlorophyll-A has not been qualified in delayed mode in the South Pacific area. So a very important comment, the authors should really improve the description of the dataset first.
Response: Thanks for your extremely professional suggestion. For the data usage problem mentioned in part 2.3, we found that we mistakenly believed that 'Quality controlled data' was equivalent to 'delayed mode data' by reading relevant articles and websites where the data came from (https://www.seanoe.org/data/00311/42182/#96562). The chlorophyll-a data we used produced by BGC-Argo were 'Quality controlled data'.
In the downloaded dataset (Quality controlled data), there are two types of chlorophyll-a data, one labeled 'CHLA' and another labeled 'CHLA_ADJUSTED'. The chlorophyll-a data we used originally is labeled 'CHLA', and this data has not been optimized for non-photo-chemical quenching (NPQ) effects. The chlorophyll-a data labeled 'CHLA_ADJUSTED' is adjusted data and has been optimized for NPQ effects. So, we used the adjusted data of chlorophyll-a redone the experiment.
We rephrased these sentences : “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used” (Page 4, line 114).
Comment 2: The BGC-Argo chlorophyll-A qualification is very heterogeneous presently from a float to another and it is not mentioned in the manuscript. Moreover, there is no mention in the manuscript of the major feature of the Chlorophyll-A measurements, based on fluorescence. According to me it requires careful use of this Chlorophyll-A dataset without ignoring this feature. I think that dealing with this issue is a prerequisite before trying to compare BGC-Argo Chlorophyll-A profiles with satellite data.
The chlorophyll-a measured by BGC-Argo, based on fluorescence data, is affected by the non-photochemical quenching and this can have a huge impact on the Chlorophyll-a estimation mainly at the surface. It is not clear in the manuscript whether the authors are using raw data from the BGC-Argo dataset or the adjusted fields (corrected in real-time of the quenching); this should be mentioned as a first step.
Then, depending on the option chosen (raw vs. adjusted), the authors must describe their treatment of the data and explain in details the quality control that they are applying on the data (it is mentioned, but there is no details).
Response:
Thanks for your suggestion. The ratio of chlorophyll-a fluorescence (measured by the sensors) to chlorophyll-a concentration varies as a function of non-photo-chemical quenching (NPQ) [1]. Chlorophyll fluorescence of phytoplankton decreases when exposed to ambient light. The chlorophyll-a data labeled 'CHLA_ADJUSTED' we used has been optimized for NPQ effects [2]. (Page 4, line114).
The temperature data we used is labeled 'TEMP_ADJUSTED'. Some times, the data labeled 'DATA_ADJUSTED' is lacked in some floats, then we will use data labeled 'DATA' with mode 'A'. For nitrate data, according to the manual, the data we used is labeled 'NITRATE' with mode 'A' [3]. Similarly, bbp, and PAR data with mode 'A' were used. The data labeled 'DATA_ADJUSTED' or with mode 'A' are adjusetd data. (Page 4, line115).
Then, we converted the adjusted profile data into vertical profile data with an accuracy of 1m according to PRES (sea water pressure) data, and then smoothed them with a 15-point moving mean filter and median filter to remove noises. Finally, we plotted the profiles in eddies of different polarity (Page 5, line128).
In the end, we redone the experiment using adjusted data, and all the tables and figures are updated. The variation of the experimental results is mainly concentrated in the Mixed Layer Depth, the second paragraph of part 3.3 and the second paragraph of part 4.
We rephrased these sentences, and added references : “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects...)(Page4 line114)”; “Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises. (Page4 lines125-129)”
Comments on the Figures:
Comment 1: Considering that the MLD is close to 50m, it is hard to see that the figure 2 highlights any difference between AEs and CEs in CHL concentration as mentioned in the text, a zoom of the figure could be added.
Response: Thanks for your suggestion. We added a zoom of figure 2 from 0-50m in supporting information, and the relationship of Chl concentration in AEs and CEs can also be seen in Table 1.
Comment 2: Still on the BGC-Argo dataset, the figure 4c. is not obviously illustrating an increase of nutrients in the area of 50m to 110m as mentioned by the authors, from AEs to CEs. If the BGC-Argo data nitrate profiles are qualified in delayed mode as mentioned by the authors, they are provided with uncertainties and these uncertainties are within +-1 micromol per kg. I think that the authors should also consider carefully the uncertainties of the dataset before concluding.
Based on these different remarks, to further evaluate whether this study is relevant, as it is presently difficult to check exactly what data are used, how they are qualified and whether the data are used correctly, the authors should consider revisiting deeply their "data" part (http://www.argodatamgt.org/). It could be also useful to mention the Argo WMO of the floats that they are using in their study.
Response:
Thanks for your suggestion. As mentioned previously, the data we used is labeled 'NITRATE' with mode 'A'. The small difference of nitrate concentrations between AEs and CEs in the South Pacific Ocean (SPO) is due mainly to the oligotrophic nature of the SPO, where nitrate concentrations are inherently low. On the other hand, according to statistics, there are more than 400 nitrate profiles in this area. Therefore, we believe that these nitrate data with mode 'A' are reliable. The nitrate data also used in other paper [4].
We added BGC-Argo's ID number in this manuscript (6901659，6901660，6901687，6902701), as the unique identifier that they can be found on the website: https://biogeochemical-argo.org/data-access.php (Page 4, line 113)
We rephrased these sentences: “There are 4 BGC-Argo floats were used in our study (ID: 6901659，6901660，6901687 and 6902701), they can be found on the website: https://biogeochemical-argo.org/data-access.php.”
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
We also rephrased the second paragraph of part 3.3, the second paragraph of part 4 and the second paragraph of part 5 due to the modulation of data (chlorophyll, BBP).
The second paragraph of part 3.3: “In MLD, the concentration of CPhyto in AEs was found to be higher compared to CEs, which was consistent with the Chl results. The Chlʹ=21% and the Cphytoʹ=5.1% in MLD, suggest that although the Chl in AEs was much higher than in CEs, the biomass was not significantly higher (Figure 3, Table 1). The θ profile precisely explains this phenomenon, θʹ=15.6% in this layer, indicating that the pigment concentration per individual phytoplankton cell in AEs is higher than in CEs. That is, in MLD, the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton, and induced the higher of Chlʹ than Cphytoʹ. ”
The second paragraph of part 4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light. Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth (Figure 4c). Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (Figure 4a) (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the Chlʹ lower than Cphytoʹ. However, the opposite situation has emerged currently, the Chlʹ is higher than Cphytoʹ in MLD (Table 1). This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (Table 1).”
The second paragraph of part 5: “In MLD, AEs have a higher Chl concentration than CEs, is driven by both biomass and physiological adjustment of phytoplankton, and the physiological adjustment plays a predominate role. As a result of the convergent subsidence, AEs deepened MLD and can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. The deepening MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption, and the higher temperature in AEs plays a little negative contribution.”
References:
[1]Bittig, Henry C., et al. "A BGC-Argo guide: Planning, deployment, data handling andusage." Frontiers in Marine Science 6 (2019): 502.
[2]Schmechtig, C., et al. "Bio-Argo quality control manual for the Chlorophyll-A concentration, Ifremer." (2018).
[3]Johnson, Kenneth, et al. "BGC-Argo quality control manual for nitrate concentration." (2021).
[4]Xiu, P., & Chai, F. (2020). Eddies affect subsurface phytoplankton and oxygen distri-butions in the North Pacific Subtropical Gyre. Geophysical Research Letters, 47, e2020GL087037. https://doi. org/10.1029/2020GL087037
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AC2: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
We updated our reply, and fixed some errors.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues：“… and the distribution of sea surface Chl concentration in eddies of different polarity was investigated”
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence. “Our study indicate that the characteristics of Chl profiles and their influencing factors vary across different depths in seawater. The contribution of phytoplankton biomass and physiological regulation to Chl concentration is different at different depths. Therefore, it is not sufficient and can not provide complete information to study the effect of eddies on Chl only using remote sensing data. This study filled this gap, and will have significant implications for enhancing our understanding of the biogeochemical processes and carbon cycle associated with eddies.” (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence:“The dataset provided by AVISO for identifying and tracking eddies from January 2000 to August has been selected. The eddies obtained through the interpolation algorithm and amplitude exceeding less than 1cm and lifetime less than 10 days have been excluded to reduce errors.” (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m. We rephrased the sentence:“Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises.”(Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1): “CPhyto (phytoplankton carbon) was calculated from BBP which is defined as: CPhyto = 0.19 × (53607× BBP700 × (700/550) + 2.5), it represents the quantity of phytoplankton biomass.” ; “the higher the value of , means the greater the Chl concentration in AEs compared to CEs. indicates the mean Chl concentration in AEs, and represents the mean Chl concentration in CEs, while means Chl mean values outside eddies. ” (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1. We rephrased the sentence:“In MLD, the Chl concentration in AEs was slightly higher than that in CEs” (Page 7, line 174).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence:“In general, the phytoplankton biomass was mainly affected by nitrate concentration (Sukigara, 2022). This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.” (Page 10, lines 239-242).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response: Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence：“This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.”
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. We add a reference.
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference.
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. Due to data modification, we rephrased the second section of part4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light (Poppeschi et al., 2022). Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the lower than . However, the opposite situation has emerged currently, the is higher than in MLD. This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (He et al., 2021).”
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence: “Therefore, it’s difficult for CEs to carry the eutrophic water to surface from the deep ocean through eddy pumping, however, AEs can contact more nutrients because of the deepening MLD.”(Page 12, lines 301-302).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence: “In this study, we mainly utilized biogeochemical-argo (BGC-Argo) data to investigate the relationships between Chl levels…” (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence: “and environmental factors (CPhyto, nitrate, temperature and light) and the underlying dynamic mechanisms of mesoscale eddies in SPO.” (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3. “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used”
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion.
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
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AC3: 'Reply on RC1', Meng Hou, 24 Oct 2023
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RC2: 'Comment on egusphere-2023-1735', Anonymous Referee #2, 08 Oct 2023
Comment on “Eddy-induced chlorophyll profile characteristics and underlying dynamic mechanisms in the South Pacific Ocean”
by Meng Hou, Jie Yang, Ge Chen, Guiyan Han, Yan Wang and Kai Wu
General comments:
The study analyses the impact of dynamic processes within mesoscale eddies on chlorophyll, biomass, nitrate, temperature, and light in the upper ocean of the South Pacific. The aim is to decipher the relationship between physical-biological interactions of mesoscale eddies and primary productivity. Hereby, chlorophyll can be used as an index for marine primary production. The study is based on measurements by BGC-Argo floats and satellite measurements in the South Pacific Ocean. The report addresses relevant scientific questions and gives new insight into the influence of mesoscale eddies on primary productivity at different levels in the upper ocean. My main concerns are about the presentation and discussion of the data. The figures need to be improved in order to better understand the authors' conclusions. In the discussion, it is sometimes difficult for the reader to distinguish the results of this study from previous studies, which has to be clarified. More explanations in the methods would be great. Conclusions are stated clearly. I recommend publication of this manuscript after major revision. Please see my comments below in the specific comments.
Specific comments:
Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Page 10, line 242-244: In case this is common knowledge a reference is missing.
Page 11, line 253-258: Reference is missing for the statement.
Page 11, line 256-258: Please rephrase.
Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Figure 3 and 4: Same scale of the y axis would be helpful for comparison.
Technical comments:
Page 1, line 16: Please explain the acronym “BGC”
Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Page 3, line 71: “driver” – Should it say “drive”?
Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used. for this study.
Page 9, line 208: Please either delete “although” or “while”.
Page 9, line 212: Do you mean “lower rate”?
Page 11, line 249: Blank missing.
Page 12, line 292, 293: Should say “feeds” and “attracts”
Citation: https://doi.org/10.5194/egusphere-2023-1735-RC2 -
AC1: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues.
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m (Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1) (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1 (Page 7, line 173).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 10, lines 238-241).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response:
Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence.
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. This is one of a conclusion in our study, we have rephrased the sentence (Page 10, lines 238-241).
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference (Page 11, line 260).
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 11, lines 256-258).
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 300-301).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3.
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion. We rephrased the sentence, according to the latest data, it means the value Chlʹ is higher than Cphytoʹ (Page 9, line 214).
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
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AC2: 'Reply on RC2', Meng Hou, 24 Oct 2023
Dear Reviewers:
We would like to thank you for carefully reading our manuscript. We appreciate the comments and suggestions, your crucial comments helped us solve a lot of problems. In the following, we include a point-by-point response to the comments from each reviewer. In the revised manuscript, all the changes have been highlighted in red.
We updated our reply, and fixed some errors.
Comment 1: Page 3, line 76: What do you mean with “polar eddies”? Do you mean eddies of different polarity?
Response: Thanks for your suggestion. Yes, it mean eddies of different polarity (AE/CE), and we have revised grammar issues：“… and the distribution of sea surface Chl concentration in eddies of different polarity was investigated”
Comment 2: Page 3, lines79-89: It is unusual to place the results at the end of the introduction. I would rather formulate specific scientific questions to be answered in this study and/or describe the structure of the paper (data, methods, results, discussion…)
Response: Thanks for your crucial comment, we delete these results and rephrased these sentence. “Our study indicate that the characteristics of Chl profiles and their influencing factors vary across different depths in seawater. The contribution of phytoplankton biomass and physiological regulation to Chl concentration is different at different depths. Therefore, it is not sufficient and can not provide complete information to study the effect of eddies on Chl only using remote sensing data. This study filled this gap, and will have significant implications for enhancing our understanding of the biogeochemical processes and carbon cycle associated with eddies.” (Page 3, lines 79-83).
Comment 3: Page 4, line 95: In the introduction, the authors state that “winter mixing enhances the productivity of AEs and CEs”. I was wondering, whether the dataset from “January 2000 to August 2021” might be imbalanced in terms of seasonality. It is worth to analyse, whether the the interaction between dynamic processes of mesoscale eddies and chlorophyll is related to seasonal variability (at least summer and winter condition). Also, I am missing some general information about mesoscale eddies such as the generation mechanisms and formation regions.
Response:
Thanks for your suggestion. The sentence “winter mixing enhances the productivity of AEs and CEs” was cited from previous research, and we have add a reference afeter the sentence. We read the article again carefully and find that, in South Pacific Ocean, whether in winter or summer, chlorophyll concentration in AEs is higher than CEs, chlorophyll concentration in AEs is higher than CEs. In winter, the difference of chlorophyll concentration between AEs and CEs is more obvious. SO, the change of seasons did not affect the results of the experiment.
The generation mechanism of eddies is complex, with factors such as wind, ocean currents, changes in submarine topography, and geostrophic effects. In the nearshore area, eddies are more prevalent and can move both eastward and westward. In the open ocean, our study did not take into account he generation mechanisms and formation regions of eddies, so we did not provide a detailed description of these characteristics of eddies. We also referred Chelton's article, he described the detail characteristics of eddies, and the AVISO data we used is from Chelton’s arithmetic.
Comment 4: Page 5, line 119-121: Please rephrase the sentence, as it is hard to understand.
Reponse: Thanks for your suggestion. We rephrased the sentence:“The dataset provided by AVISO for identifying and tracking eddies from January 2000 to August has been selected. The eddies obtained through the interpolation algorithm and amplitude exceeding less than 1cm and lifetime less than 10 days have been excluded to reduce errors.” (Page 5, lines 119-121).
Comment 5: Page 5, line 125-128: What vertical resolution do the float profiles have (before interpolation). Are there any criteria to omit profiles with a coarse vertical resolution?
Response: Thanks for your suggestion. There are significant uncertainty in the vertical resolution of these float profiles. In the process of these floats floating up, they will constantly measure the surrounding physical parameters. It may be a few meters to measure a value, and it may be tens of centimeters to measure a value, and the resolution decreases with the depth increased. To facilitate data processing, we interpolate these data according to the depth at where they were measured, so that each profile has a vertical resolution of 1m. We rephrased the sentence:“Preprocessing are performed before BGC-Argo data being used. There are significant differences in the vertical resolution of these float profiles. To facilitate data processing, we interpolated these data according to the depth at where they were measured, the interpolated profile data exhibits an accuracy of 1 meter. In the end, these profile data was smoothed with a 15-point moving mean filter and median filter to remove noises.”(Page 5, lines 126-128).
Comment 6: Page 5, line 135-145: Please give some explanations on the significance/meaning of Cphyto and equation (1) as it would be easier to understand.
Response: Thanks for your suggestion. Cphyto (phytoplankton carbon) can represent the quantity of biomass, and was calculated from BBP which is defined as: Cphyto = 0.19 × (53607 × BBP700 × (700/550) + 2.5). Equation (1) means relative differences of Chl between AEs and CEs, the higher the value of Chl', means the greater the Chl concentration in AEs compared to CEs. We added more description of Cphyto and equation (1): “CPhyto (phytoplankton carbon) was calculated from BBP which is defined as: CPhyto = 0.19 × (53607× BBP700 × (700/550) + 2.5), it represents the quantity of phytoplankton biomass.” ; “the higher the value of , means the greater the Chl concentration in AEs compared to CEs. indicates the mean Chl concentration in AEs, and represents the mean Chl concentration in CEs, while means Chl mean values outside eddies. ” (Page 5, lines 134-137, 141-146).
Comment 7: Page 6, line 152: Why exactly is this area (16°S-24°S, 160°W-144°W) used for this study.
Response: Thanks for your suggestion. The area belongs to the central location of the South Pacific Ocean, and the marine environment is relatively stable. On the other hand, the BGC-Argo floats is more concentrated in this region, and these floats have more kinds of data, so we choosed the area in this study.
Comment 8: Page 7, line 171: The higher Chl concentration in AEs than in CEs is impossible to see in Figure 2. I would suggest to split up Figure 2 into three depth section: 0-50m, 50-150m, 150-300m depth with different x-axis to better resolve the small changes at depth. Same with Figure 3 and 4.
Response: Thanks for your suggestion. We are quite agree with you, and we have added these pictures in supporting information. We added reference of table 1, the relationship of Chl concentration in AEs and CEs can also be seen in Table 1. We rephrased the sentence:“In MLD, the Chl concentration in AEs was slightly higher than that in CEs” (Page 7, line 174).
Comment 9: Page 10, line 236-237: I don’t understand the sentence, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence:“In general, the phytoplankton biomass was mainly affected by nitrate concentration (Sukigara, 2022). This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.” (Page 10, lines 239-242).
Comment 10: Page 10, line 237-239: Do you mean anticorrelation between Cphyto and nitrate? Anyway, the relationship between these two parameters is hard to see in the upper 120m as the decrease of the nitrate is very weak.
Response: Thank you for your important comment, and we are quite agree with you. Our original meaning is that, with the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m. On the other hand, the nitrate concentration in AEs is higher than in CEs, the result is consistent with the distribution of Cphyto concentration (Cphyto in AEs is higher than in CEs). Therefore, there is a strong correlation between nitrate concentrations and phytoplankton biomass. In the upper 120m, when the light conditions can meet the needs of phytoplankton growth, phytoplankton will grow and consume nitrate, the phytoplankton biomass and nitrate concentration will eventually reach a balance state. So, in the upper 120m the decrease of the nitrate is not obvious. In the end, we rephrased the sentence：“This is also illustrated by the fact that the nitrate and CPhyto profiles exhibited high correlations. With the rapid decline of phytoplankton biomass, the nitrate concentration increases rapidly at around 150m.”
Comment 11: Page 10, line 242-244: In case this is common knowledge a reference is missing.
Response: Thanks for your suggestion. We add a reference.
Comment 12: Page 11, line 253-258: Reference is missing for the statement.
Response: Thanks for your suggestion. We added a reference.
Comment 13: Page 11, line 256-258: Please rephrase.
Response: Thanks for your suggestion. Due to data modification, we rephrased the second section of part4: “In MLD, our research showed that the higher Chl concentration in AEs compared to CEs is driven by both biomass and physiological adjustment of phytoplankton. Whether biomass or pigment concentration is responsible for the difference in Chl concentration between AEs and CEs, is ultimately relies on the influence of eddies on nutrients, temperature and light (Poppeschi et al., 2022). Due to the modulation mechanism of the eddies on the MLD (AEs deepen the MLD and CEs make it shallower), AEs can contact deeper nutrient lines, the mixing of turbulent flow enables AEs to have higher nutrient concentrations and promotes phytoplankton growth. Meanwhile, because of the function of the eddy pump, AEs have a higher temperature relative to the CEs (temperature′=1.8%). On the one hand, the higher temperature in AEs promotes the metabolic capacity of phytoplankton and promotes the growth of phytoplankton, increasing the biomass. On the other hand, higher temperature will also reduce the concentration of pigment in phytoplankton cells, and finally weaken the Chl concentration within AEs, making the lower than . However, the opposite situation has emerged currently, the is higher than in MLD. This suggests that temperature may not be the primary determinant influencing phytoplankton's physiological adjustment in MLD, but the light. The deepened MLD in AEs increased the vertical migration of subsurface phytoplankton, resulting in a reduction in light exposure, and thus contributing to an increase in cellular pigment due to light adaption (He et al., 2021).”
Comment 14: Page 11, line 258-261: Do you refer to this study or to previous studies? Please give a reference.
Response: Thanks for your suggestion. We have rephrased the sentence to make it clear what we mean, the sentence continues the previous sentence, we added a reference in Response 11.
Comment 15: Page 12, line 300-301: This sentence is hard to understand, please rephrase.
Response: Thanks for your suggestion. We rephrased the sentence: “Therefore, it’s difficult for CEs to carry the eutrophic water to surface from the deep ocean through eddy pumping, however, AEs can contact more nutrients because of the deepening MLD.”(Page 12, lines 301-302).
Comment 16: Figure 3 and 4: Same scale of the y-axis would be helpful for comparison.
Response: Thank you very much for your advice, and we are quite agree with you. We have replotted figure 3 and 4. We also added pictures with depth section: 0-50m, 50-150m, 150-300m for Figure3 and 4 in supporting information.
Technical comments:
Comment 17: Page 1, line 16: Please explain the acronym “BGC”
Response: Thanks for your suggestion. We rephrased the sentence: “In this study, we mainly utilized biogeochemical-argo (BGC-Argo) data to investigate the relationships between Chl levels…” (Page 1, line 16).
Comment 18: Page 1, line 17: “…Nitrate, Temperature and Light…” – Should be written in lower case.
Response: Thanks for your suggestion. We rephrased the sentence: “and environmental factors (CPhyto, nitrate, temperature and light) and the underlying dynamic mechanisms of mesoscale eddies in SPO.” (Page 1, line 17).
Comment 19: Page 1, line 18: “Our findings showed that, …” – Incorrect comma, please delete.
Response: Thanks for your suggestion. We deleted the comma, and rephrased the sentence. (Page 1, line 18)
Comment 20: Page 1, line 24: “(…euphotic zone) ,” – Incorrect blank, please delete.
Response: Thanks for your suggestion. We deleted the blank (Page 1, line 24).
Comment 21: Page 3, line 71: “driver” – Should it say “drive”?
Response: Thanks for your suggestion. Yes, and we corrected the word (Page 3, line 71).
Comment 22: Page 4, line 103: Please explain the acronyms “ZEU/BBP” and why ZEU and BBP are used for this study.
Response: Thanks for your suggestion. We rephrased the sentence (Page 4, line3 99-100). The data ZEU/BBP we used from BGC-Argo data are explained in part 2.3. “The adjusted data of Chl (has been optimized for non-photo-chemical quenching effects), BBP (particulate backscattering coefficients), temperature, PAR (photosynthetic available radiation) and nitrate produced by BGC-Argo were used”
Comment 23: Page 9, line 208: Please either delete “although” or “while”.
Response: Thanks for your suggestion. Word “while” was deleted (Page 9, line 210).
Comment 24: Page 9, line 212: Do you mean “lower rate”?
Response: Thanks for your suggestion.
Comment 25: Page 11, line 249: Blank missing.
Response: Thanks for your suggestion. We added a blank (Page 11, line 250).
Comment 26: Page 12, line 292, 293: Should say “feeds” and “attracts”
Response: Thanks for your suggestion. We rephrased the sentence (Page 12, lines 291-293).
Supplement:
We updated the algorithm for Cphyto and added references: Cphyto = 0.19 × (53607× BBP700 × (700/550) + 2.5) (Page5, lines 135-136).
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AC1: 'Reply on RC2', Meng Hou, 24 Oct 2023
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