the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Dec 2024
Assessing and optimizing the role of wind forcing and upper-ocean dynamics in marine pollution transport simulations using surface drifters in the Canary Current System
Abstract. This study investigates the sensitivity of undrogued drifter trajectory simulations in the Macaronesia region, selected for their similarity to the behavior of marine litter transport in the upper ocean. The research evaluates the influence of various physical processes, including advection schemes, horizontal dispersion, windage and Stokes drift. A total of 320 simulations were conducted, incorporating different combinations of these processes, the modeled trajectories were compared with real drifter data. The analysis demonstrated that the inclusion of windage and/or Stokes drift significantly improved the agreement between modeled and observed trajectories, particularly when windage factors (WDF) ranged from 2.5 % to 5 %. Horizontal dispersion exhibited minimal influence on the trajectories, indicating that turbulent diffusion had a limited effect under the study conditions. While both advection schemes (RK2 and RK4) produced comparable results, RK4 outperformed RK2 in scenarios involving pronounced mesoscale activity. This research highlights the relevance of using undrogued drifters to mimic marine litter transport and underscores the importance of incorporating windage and/or Stokes drift in trajectory simulations, particularly in regions like Macaronesia, where mesoscale processes play a critical role.
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RC1: 'Comment on egusphere-2024-3913', Anonymous Referee #1, 22 Jan 2025
Review of “Assessing and optimizing the role of wind forcing and upper-ocean dynamics in marine pollution transport simulations using surface drifters in the Canary Current System” by Cubas et al.
The manuscript is aimed at assessing and optimizing the role of wind forcing and upper-ocean dynamics in marine pollution transport simulations using surface drifters in the Canary Current System. First of all, this study is based on a very limited drifter dataset in the above region and it remains unclear why the specific time period was chosen and how many drifters in total were available during that time period. The authors further need to provide more information on the used Lagrangian modeling framework “TrackMPD” including differences to other such tools. As regards the results and discussion, this section is merely a technical description; that is, a discussion is essentially lacking (e.g., sensitivity of input datasets, broader implications). Moreover the referencing is generally inadequate, particularly in terms of previous drifter-based marine pollution studies, and a figure of the study region showing the Canary Current System should also be provided for context. With that said, I recommend rejection of the manuscript in its present form as much more work is required to make a substantial contribution to marine pollution research.
Citation: https://doi.org/10.5194/egusphere-2024-3913-RC1 -
AC2: 'Reply on RC1', Francisco Machín, 27 Feb 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3913/egusphere-2024-3913-AC2-supplement.pdf
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AC2: 'Reply on RC1', Francisco Machín, 27 Feb 2025
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RC2: 'Comment on egusphere-2024-3913', Anonymous Referee #2, 30 Jan 2025
Review of “Assessing and optimizing the role of wind forcing and upper-ocean dynamics in marine pollution transport simulations using surface drifters in the Canary Current System” by Cubas et al.
The manuscript presents a sensitivity study of numerical simulations of drifter trajectories, with respect to e.g. wind drift factor, Stokes drift, diffusivity and propagation scheme.
The manuscript is generally quite easy to read, with clear and good language.
However, the main weakness is the lack of novelty and substantial conclusions.Numerous earlier studies have investigated the role and impact of the same parameters, and a general consensus is that a wind drift factor of around 3% is giving best results for this type of drifter, or a slightly lower factor if the Stokes drift is added explicitly. This manuscript uses wind drift factors of 0%, 1%, 2.5%, 5% and 7%, and finds best results with the values 2.5% and 5%. Thus the manuscript confirms what is already well known, but does not contribute a precise optimal value that could e.g. be included in a review study. A possible dependency of wind drift factor on wind speed is mentioned, but also this is not investigated.
The study also includes diffusivities between 0 and 5 m2/s (but uses mostly 0 and 1m2/s). No justification is given for the choice of these numbers, which seem quite low, and there is also no discussion of why a diffusivity would improve the skill score.
The study also finds that second and fourth order Runge Kutta schemes give similar performance, except for a single case where fourth order gives better agreement with the observed drifter. However, this should also be discussed in light of the given time step, which is fixed as 1 hour. For a smaller time step, differences would be even smaller, and for a larger time step, fourth order would certainly be necessary.
Figure 2 summarises most of the results, but is unnecessarily difficult to read, with the defined scenarios in Table 3 on the x-axis. Thus the reader must look back and forth between the figure and Table 3 to see what the scenarios represent. Figures with physical parameters on the x-axis (such as Figure 4) are much easier to read.
The only novelty of the study would be application to this specific region. However, the sensitivity parameters investigated should be generic and related to the specific type of drifter, and not depending on the specific region. Thus instead, this study would be an indirect validation of how well the ocean- and atmospheric models perform in this region - but this is not discussed at all.
With the above mentioned weaknesses, and in particular the lack of novelty, I recommend rejection of the manuscript in its present form.
Citation: https://doi.org/10.5194/egusphere-2024-3913-RC2 -
AC1: 'Reply on RC2', Francisco Machín, 27 Feb 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3913/egusphere-2024-3913-AC1-supplement.pdf
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AC1: 'Reply on RC2', Francisco Machín, 27 Feb 2025
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EC1: 'Reflection on the two reviewer comments on egusphere-2024-3913', Erik van Sebille, 13 Feb 2025
Dear authors
Thank you again for submitting your work to Ocean Science. The open discussion of your manuscript is now closed, and I assume you have seen the two anonymous referee comments posted earlier.
The referees are very critical of the novelty and relevance of your study, and both recommend rejection of the manuscript. It appears very unlikely that you will be able to fix these problems upon revision, so I discourage submission of a revised manuscript.
Instead, I hope you can use some of the pointers and suggestions of the referees to reshape your manuscript and find another journal where this work may find a place.
Kindest regards
Erik van Sebille
Citation: https://doi.org/10.5194/egusphere-2024-3913-EC1 -
AC3: 'Reply on EC1', Francisco Machín, 27 Feb 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3913/egusphere-2024-3913-AC3-supplement.pdf
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AC3: 'Reply on EC1', Francisco Machín, 27 Feb 2025
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