Comments

There are a few minor issues, which need to be addressed before publication, see comments below.

1. One thought I had, if I may … the text (L353) says that the user is “encouraged to contact the authors for more details on the data”. I find this statement controversial. As I understand the mission of ESSD, it is exactly this text here, which should present those details. From my point of view, the only reason for text around data is to enable people to use it - without contacting the authors, at least not to learn only about “details on the data”.

Response:

Thanks for your comments. We carefully read them and here are responses to the comments and a revision plan about the manuscript. The formal revision will be made based on all feedbacks.

The controversial statement will be made more specific as ‘All data are freely available to users and organized in an easy-to-read and easy-to-use way. Users should be able to apply the data based on this description paper and the detailed Readme.dat file included in the dataset. Contacting the authors is also welcome for obtaining the raw data or informing research aims.’

2. L51 "tidal pumping mechanisms (Du et al., 2022; Grasso et al., 2018; Jiang et al., 2013)"

Not sure about these references. Each paper includes a discussion of tidal pumping, yes, but some of them do not really talk about the mechanisms causing tidal pumping to contribute to transport. These mechanisms (among others) could be tidal trapping (Okubo, 1973) or triggered by along-channel irregularities in cross-sectional area, see papers cited in, e.g., Geyer and Ralston (2011).

Okubo, A. (1973). Effect of shoreline irregularities on streamwise dispersion in estuaries and other embayments. Netherlands Journal of Sea Research, 6(1–2), 213–224. https://doi.org/10.1016/0077-7579(73)90014-8

Geyer, W. R., & Ralston, D. (2011). The dynamics of strongly stratified estuaries. In Treatise on estuarine and coastal science (pp. 37–51). Elsevier. https://doi.org/10.1016/b978-0-12-374711-2.00206-0

Response:

We keep and supplement references which are more concentrated on tidal pumping mechanisms and their effects on sediment transport, revision will be made as ‘...various tidal pumping mechanisms (Du et al., 2022; Geyer and Ralston, 2011; Jiang et al., 2013; Okubo, 1973) also have impacts on sediment and ETM dynamics.’

3. L51 "have impacts on" -> have an impact on

Response:

This will be revised.

4. L52 "high turbidity will suppress turbulence mixing" more precise ... sediment-induced stratification can suppress turbulent mixing

Response:

Thanks for the detailed explanation and we will follow this precise expression.

5. L53 "locations of ETMs are usually highly turbid with active" well, the abbreviation "ETM" already implies that turbidity is comparatively high, please rephrase

Response:

Agree, this will be revised as ‘Therefore, locations of ETMs usually have active and complex fluid and sediment dynamics, and are hotspots in estuary research.’

6. L54 "including reclamation and engineering structures significantly affect turbidity levels and the ETMs"

This is very general ... reclamation probably refers to the loss of intertidal area; what about channel deepening? If you cite that Winterwerp paper, please formulate a bit closer to the actual processes. Otherwise, there are more general texts on the subject, which you can cite.

Response:

This will be rephrased as ‘Additionally, human interventions including reclamation, channel deepening, and engineering structures significantly affect turbidity levels and the ETMs. For example, reclamations can influence the accommodation space for suspended fine sediments and therefore reduce system resilience to engineering works such as channel deepening (Winterwerp et al., 2013).’

7. L66 "within the passage, are still poorly" -> within the passage are still poorly

Response:

Will be revised as commented.

8. L77 "The outcomes of this dataset are manifold: ... developing AI-based predictive tools tasked with resolving near-bed high-SSC suspension dynamics"

These outcomes you are talking about, did this already happen, or is this science fiction? If anything has been published (and it has, right?) please include the citations here. If this is ongoing or planned, please make this clear.

Response:

Relevant references are added and this part is rephrased as ‘The outcomes and prospect of this dataset are manifold: it enhances continuity of observational data, advances our understanding of hydro- and sediment dynamics within both the NP and the broader ETM of the CE (e.g., Ge et al., 2018; Zhou et al., 2021), and can produce datasets available for improving numerical models or developing AI-based predictive tools in future works tasked with resolving near-bed high-SSC suspension dynamics.’

9. L88 "bifurcation orders" what are "bifurcation order"? I guess you are referring to the branch-channel-passage "order"? Please explain

Response:

This sentence will be revised using a more common introduction to the Changjiang Estuary as ‘The Changjiang Estuary has three-level bifurcations and four outlets (Wang et al., 2015).’

10. L94 "source for the inner shelf" source of what? Freshwater, sediments, nutrients ...

Response:

It will be revised using a more specific expression: ‘The Changjiang River is a major source of freshwater for the inner shelf of the East China Sea (Figure 1).’

11. L117 You might consider to cite Becker et al. (2018), who show how inverse salinity profiles are a side effect of differential advection in presence of sediment-induced density stratification.

Becker, M., C. Maushake and C. Winter (2018). "Observations of Mud‐Induced Periodic Stratification in a Hyperturbid Estuary." Geophysical Research Letters 0(0).

Response:

This paper will be cited in the revision.

12. L121 "synergistic impacts" sounds nice, what does this mean?

Response:

Ge et al., (2018) discussed a positive feedback loop of physical processes controlling the formation process of concentrated benthic suspension during weak tidal mixing. In this feedback loop, the formation of CBS leads to 1) TKE suppression, 2) stratification enhancement, 3) sediment mixing confinement, 4) hindered settling and higher suspended sediment concentration near the bed, which further benefit the formation of CBS. On the other hand, the salt wedge can also suppress vertical mixing and therefore influencing hydrodynamics and interacting with other dynamics, e.g., the CBS formation. So, we previously use ‘synergistic impacts’ to indicate potential combined, complicated effects of salt wedge and CBS on hydrodynamics. In the revision, we will try to make it more specific,

‘In the NP, observations frequently reveal the presence of a salt wedge and concentrated benthic suspensions (Chen et al., 2019; Ge et al., 2018; Pu et al., 2015; Xue et al., 2009), underscoring the significance of their synergistic impacts on regional hydrodynamics, as both of them can influence the stratification and mixing conditions.’

13. L146 channel-shoal systems ... you might cite Geyer et al. (2020) - which you cite later in the text anyway.

Geyer, W. R., D. K. Ralston and J.-L. Chen (2020). "Mechanisms of Exchange Flow in an Estuary With a Narrow, Deep Channel and Wide, Shallow Shoals." Journal of Geophysical Research: Oceans 125(12): e2020JC016092.

Response:

This citation will be added, ‘Strategically positioned measurement stations spanning both shoals and the deeper channel are essential to effectively monitor lateral flows and sediment transport in complex channel - shoal systems (Geyer et al., 2020), such as the NP.’

14. L183 "a high sampling frequency of 16 Hz" 16 Hz is not particularly high for an ADV. 32 Hz would be quite normal, and since some time and in certain conditions 64 Hz is possible, too

In which coordinate system did you collect the data? How did you rotate velocities from beam over instrument to earth coordinates? Same question for the ADCPs, coordinate system, and rotation? Please describe in the text.

Response:

We agree that the frequency of 16 Hz is not quite high, and the previous words have been revised. We collect the data in the ENU coordinate system, and the velocity data are directly recorded as ‘Velocity (Beam1-X-East)’, ‘Velocity (Beam2-Y-North)’, ‘Velocity (Beam3-Z-Up)’. The ADCP data are also collected in ENU coordinate system. This information will be supplemented in the manuscript as ‘Both ADCP and ADV collected data in ENU coordinate systems.’

15. L184 "capturing accurate velocity data" Would you include these data in the data set, if they weren't accurate?

Response:

Here the word ‘accurate’ may cause misunderstandings, therefore deleted. For the ADV data, we conducted quality control based on the Beams Correlation, and applied a bandpass filter to despike the data for TKE calculation. With these measures, we hope to provide high-quality data to the readers. But this does not mean the data are absolutely accurate.

16. L188"Water elevation, salinity, temperature, and turbidity were measured by the OBS"

I guess you are saying that you determined water level elevation from the pressure sensor, which is contained in the OBS-3A, right? Could you make this clear, otherwise it reads as if you are using a backscatter sensor to measure pressure - see also L260

Response:

Thanks for highlighting this point. Yes, the water level elevation was detected by the pressure sensor of OBS-3A. This sentence will be revised as, ‘Salinity, temperature, and turbidity were measured by the OBS-3A mounted at 0.4 (2015, 2018) or 0.9 (2016, 2017) mab. In addition, water level elevation was also detected by the pressure sensor of OBS-3A.’

17. L214 "ship-installed mud collector"

Please include the OBS-SSC calibration curves in this data publication. Your data set obviously contains SSC as a parameter, which is not measured but derived from optical backscatter.

Response:

The calibration will be added in the revision.

18. L218 "The ASM was calibrated together with the OBS"

Do you see the vertical stripes in the data (Figure 12)? It seems that there are some systematic errors, which might be a side effect of the strategy you applied to calibrate the ASM. They are not dramatic, though, right? The patterns are still there. However, the ASM consists of a lot of individual OBSs. Please describe how you calibrated all these small OBSs. Note, I'm asking this because you included SSC in the data set. You could choose to include only raw data, provide what you have in terms of calibration data, and leave the calibration to the user. But as long as you choose to provide second order parameters, the way how you arrived there should be clear.

Response:

The vertical stripes are systematic errors relating to the calibration, and we will directly discuss about the errors. In the revised manuscript, the calibrated regression relation between optically sensed turbidity (from both OBS and ASM) and suspended-sediment concentration will be included in section 4.3 Data Processing.

19. L221 "operational interruptions occasionally arose" -> "operation was occasionally interrupted"

Response:

Revised as commented.

20. L238 "Wind data was sourced from the" is that correct? Please check and rephrase

Response:

This sentence has been rephrased as: ‘Wind data at (122°E, 31.25°N) was collected from the European Centre for Medium-Range Weather Forecasts (ECMWF) to provide meteorologic information, which may help to better understand and utilize this dataset.’

21. L303 Did you despike the ADV data? For example, using a method in the line of Goring and Nikora (2002)? I believe it is fair to say that this is common practice. Spikes in ADV data can contribute substantially to the variance of the fluctuations, and corrupt the TKE estimate. If not, why was that not required? Please describe this in the text.

Goring, D. G. and V. I. Nikora (2002). "Despiking Acoustic Doppler Velocimeter Data." Journal of Hydraulic Engineering 128(1): 117-126.

Response:

The ADV data were first cleaned according to beam correlation. Then the spikes in ADV data were further removed with a 0.5 – 3 Hz bandpass filter (Kularatne and Pattiaratchi, 2008). This information will be added in section 4.3 Data Processing.

22. L313 The use of PSU as salinity unit is outdated, I suggest to follow www.teos-10.org, especially in a recent publication on data

Response:

We carefully check the information from www.teos-10.org. Section 2.1 Data Processing of the document (https://www.teos-10.org/pubs/TEOS-10_Primer.pdf) writes ‘At present, most conductivity-measuring oceanographic instruments report data that is converted to, and calibrated using, Practical Salinity S_P. This will not change. In fact, S_P will continue to be the primary salinity value stored in archives (S_P is then best thought of as a conductivity measure with the temperature and pressure dependencies removed). DO NOT ARCHIVE S_A!’  

We think Practical Salinity Unit should lead to better consistency in terms of data archiving, and this data description paper should also be consistent with the archived data. However, we appreciate your suggestion and will follow this suggestion in our research work in the future.

References

• Du, Z., Yu, Q., Peng, Y., Wang, L., Lin, H., Wang, Y., and Gao, S.: The Formation of Coastal Turbidity Maximum by Tidal Pumping in Well‐Mixed Inner Shelves, J. Geophys. Res. Ocean., 127, 1–29, https://doi.org/10.1029/2022JC018478, 2022.
• Ge, J., Zhou, Z., Yang, W., Ding, P., Chen, C., Wang, Z. B., and Gu, J.: Formation of Concentrated Benthic Suspension in a Time-Dependent Salt Wedge Estuary, J. Geophys. Res. Ocean., 123, 8581–8607, https://doi.org/10.1029/2018JC013876, 2018.
• Geyer, W. R. and Ralston, D. K.: The Dynamics of Strongly Stratified Estuaries, in: Treatise on Estuarine and Coastal Science, vol. 2, Elsevier, 37–51, https://doi.org/10.1016/B978-0-12-374711-2.00206-0, 2011.
• Jiang, C., De Swart, H. E., Li, J., and Liu, G.: Mechanisms of along-channel sediment transport in the North Passage of the Yangtze Estuary and their response to large-scale interventions Topical Collection on the 11th International Conference on Cohesive Sediment Transport, Ocean Dyn., 63, 283–305, https://doi.org/10.1007/s10236-013-0594-4, 2013.
• Kularatne, S. and Pattiaratchi, C.: Turbulent kinetic energy and sediment resuspension due to wave groups, Cont. Shelf Res., 28, 726–736, https://doi.org/10.1016/j.csr.2007.12.007, 2008.
• Okubo, A.: Effect of shoreline irregularities on streamwise dispersion in estuaries and other embayments, Netherlands J. Sea Res., 6, 213–224, https://doi.org/10.1016/0077-7579(73)90014-8, 1973.
• Wang, Z. B., Van Maren, D. S., Ding, P. X., Yang, S. L., Van Prooijen, B. C., De Vet, P. L. M., Winterwerp, J. C., De Vriend, H. J., Stive, M. J. F., and He, Q.: Human impacts on morphodynamic thresholds in estuarine systems, Cont. Shelf Res., 111, 174–183, https://doi.org/10.1016/j.csr.2015.08.009, 2015.
• Zhou, Z., Ge, J., van Maren, D. S., Wang, Z. B., Kuai, Y., and Ding, P.: Study of Sediment Transport in a Tidal Channel‐Shoal System: Lateral Effects and Slack‐Water Dynamics, J. Geophys. Res. Ocean., 126, https://doi.org/10.1029/2020JC016334, 2021.

General comments

The authors of this article present a very nice series of observations made over 4 years in one of the largest estuaries in the world, the Chanjiang Estuary. Many publications exist on this system, but this series of measurements is concentrated in the zone of maximum turbidity, on the main channel and the lateral zones during tidal cycles (semi-diurnal and ST/NT), in high and low hydrological periods. This series will be studied and used by other researchers.

- In the title I would not have indicate “NP-ChaM campaign”: too specific and which only be understood by specialists of the area.

Response:

The title will be revised as ‘Multi-year observations of near-bed hydrodynamics and suspended sediment within the turbidity maximum of the Changjiang Estuary’ to avoid being too specific.

Specific comments

1. In the general presentation it is not clearly indicated the mesotidal character of the estuary: level of tidal range

Response:

We will provide more detailed information on the estuary, including its tidal range, in Section 1 (L58 – L65).

2. Fig 10: No more units (PSU) of salinity

Response:

The unit of ‘psu’ will be removed in the revised manuscript.

3. Line 215: you never indicate the size of sediments: sand, fine sand, silts, clays.

Response:

Previous studies show that the mean floc diameters measured in the North Passage of the Changjiang Estuary ranged from 14 to 95 mm (Guo et al., 2017). Clayey silt is the dominant sediment type, primarily deposited in the lower reaches of the Changjiang Estuary (ETM Zone), in the muddy area, and on the outer estuary (Liu et al., 2010). Such information will be included in the revised version.

4. Give curves of calibration between NTU and mg/L

Response:

The calibrated regression relation between optically sensed turbidity and suspended-sediment concentration will be included in section 4.3 Data Processing.

5. Figure 4a: Why do you have an increase of Hs on 215C and not the other points? - As each parameter is presented separately in the paper, it is hard to combine all parameters for a specific period. I suggest make one zoom for example during a semi-diurnal tidal cycle during Spring Tide and High Flow to distinguish the functionning during ebb and flood between central stations and shoal stations (i.e. 2015 day 8 to 9/01)

Response:

We realize that the Hs measured at 2015B and 2015C was higher than at 2015A and 2015D, with Hs at 2015C being the highest. This is speculated to be related to the locations of 2015B and 2015C, which are very close to the heads of groynes, potentially impacting wave propagation. Since the purpose of this data description paper is to present the integrity and potential of the dataset, and more importantly, to highlight the differences/similarities of each measurement, we organized the results by measured variables and synthesized the same parameters from different measurements together. We appreciate your suggestion; however, such detailed figures already exist in other research papers using parts of this dataset, such as Ge et al., (2018) and Zhou et al., (2019). The information about channel-shoal exchange, spring-neap or dry-wet variations provided by this dataset are encouraged to be explored in more separate and detailed research papers.

Technical comments:

6. On fig. 1, it would be good to zoom on the area studied and clearly indicate the bathymetry and positions of stations.

Response:

Fig 1 will be revised as recommended.

7. On fig.1, it is a shame not to represent with the same form the points positioned in the channel and those positioned laterally.

Response:

For the visualization of site positions in Figure 1, colors indicate the measurement period, and shapes distinguish multiple sites from the same year. Site 2015B, 2015C, 2016A, 2017A are relatively close to the shallow shoal, we plan to draw these sites using different sizes to represent whether they are in the deep channel or close to the shallow shoals.

8. Table 2: add columns with range of depth and river flow values

Response:

Table 2 will be revised as suggested.

9. Table 3: August instead of Augest

Response:

This typo has been corrected.

10. Table 3: I suggest to indicate in the legend the colors of different squares (full day, part time, absence, not deployed) instead in the table itself.

Response:

We will add a sperate legend instead of including it at the corner of the table itself.

11. Fig 3: do you indicate with the arrows the direction from which the wind is coming? Normally it is So I suggest to indicate on the vertical axis North and South direction to be clear.

Response:

Indeed, the wind vectors are plotted with arrows from the coming direction, we will add ‘north’ for the y-axis of wind subplots.

12. On different figures (6 to 12: specify NT/ST and HRF (high river flow) and LRF (Low River flow) on each figures.

Response:

High and low river flows will be mentioned in the captions of each panel. In addition, we will try to add shading to indicate the spring and neap tides, similar to Figure 5. However, the decision to keep these shadings will also depend on the aesthetic effects of such visualization.

References

1. Ge, J., Zhou, Z., Yang, W., Ding, P., Chen, C., Wang, Z. B., & Gu, J. (2018). Formation of Concentrated Benthic Suspension in a Time-Dependent Salt Wedge Estuary. Journal of Geophysical Research: Oceans, 123(11), 8581–8607. https://doi.org/10.1029/2018JC013876

2. Guo, C., He, Q., Guo, L., & Winterwerp, J. C. (2017). A study of in-situ sediment flocculation in the turbidity maxima of the Yangtze Estuary. Estuarine, Coastal and Shelf Science, 191, 1–9. https://doi.org/10.1016/j.ecss.2017.04.001

3. Liu, H., He, Q., Wang, Z., Weltje, G. J., & Zhang, J. (2010). Dynamics and spatial variability of near-bottom sediment exchange in the Yangtze Estuary, China. Estuarine, Coastal and Shelf Science, 86(3), 322–330. https://doi.org/10.1016/j.ecss.2009.04.020

4. Zhou, Z., Ge, J., Wang, Z. B., Maren, D. S., Ma, J., & Ding, P. (2019). Study of Lateral Flow in a Stratified Tidal Channel‐Shoal System: The Importance of Intratidal Salinity Variation. Journal of Geophysical Research: Oceans,  124(9), 6702–6719. https://doi.org/10.1029/2019JC015307