Flow patterns, hotspots and connectivity of land-derived substances at the sea surface of Cura&ccedil;ao in the Southern Caribbean

Bertoncelj, Vesna; Mienis, Furu; Stocchi, Paolo; van Sebille, Erik

doi:https://doi.org/10.5194/egusphere-2024-3112

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https://doi.org/10.5194/egusphere-2024-3112

Preprints

21 Oct 2024

| 21 Oct 2024

Flow patterns, hotspots and connectivity of land-derived substances at the sea surface of Curaçao in the Southern Caribbean

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

Abstract. The South Caribbean Island of Curaçao is abundant in coral reef communities, but they are declining. Land-derived nutrients and pollutants are a potential contributing factor to this decline, as these substances after entering the ocean, can be transported towards reef sites by ocean currents. To study the movement of the substances and their potential impact on coral reefs, we developed SCARIBOS, a fine-resolution hydrodynamic model of the South CARIBbean Ocean System, with a 1/100° resolution. SCARIBOS covers the period from April 2020 to March 2024 (excluding spin-up time) to analyse flow patterns within that period around the close proximity of Curaçao. Furthermore, SCARIBOS is used as hydrodynamic input for Lagrangian particle tracking analysis with the Parcels framework, where we assess the distribution of positively buoyant substances and explore connectivity within Curaçao’s coastlines as well as with nearby regions of Aruba, Bonaire, the Venezuelan islands, and a portion of the Venezuelan mainland. Results reveal two dominant processes: the northwest-directed Caribbean Current and weaker cyclonic eddies moving in the opposite direction. These flow patterns influence hotspot locations of higher substance concentrations observed during eddy events. Our analysis also highlights increased particle accumulation of land-derived substances in the northwest of Curaçao, corresponding to the prevailing currents. While the focus is on land-derived nutrients and pollutants, this methodology can be extended to study other particle types such as plastic debris and coral larvae, providing valuable insights for marine conservation efforts and environmental management.

Received: 04 Oct 2024 – Discussion started: 21 Oct 2024

Competing interests: At least one of the (co-)authors is a member of the editorial board of Ocean Science.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.

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Journal article(s) based on this preprint

27 May 2025

Flow patterns, hotspots, and connectivity of land-derived substances at the sea surface of Curaçao in the southern Caribbean

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

Ocean Sci., 21, 945–964, https://doi.org/10.5194/os-21-945-2025,https://doi.org/10.5194/os-21-945-2025, 2025

Short summary

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3112', Anonymous Referee #1, 08 Nov 2024

Bertoncelj et al. describe a 1/100 degree configuration of the CROCO ocean model for the Netherlands Antilles. Using four years of model surface current output combined with Lagrangian particle tracking experiments, they focus on the island of Curaçao and investigate (i) accumulation ‘hotspots’, (ii) intra-island connectivity, and (iii) the potential for nearby islands and the Venezuelan mainland to act as sources of pollutants for Curaçao. I enjoyed reading the manuscript and, assuming the model output is indeed made publicly available prior to publication, I imagine that these data will be valuable more broadly, for a part of the ocean that appears to be somewhat data sparse. I was particularly impressed with the quality of many of the figures. I recommend the manuscript for publication, but would ask the authors to consider the suggestions in the attached supplement, which can be considered as major revisions. These suggestions mainly relate to (i) more rigorous assessment of model hydrodynamics, and (ii) the clarity of some analyses/discussion, particularly relating to scenario 1.

Citation: https://doi.org/10.5194/egusphere-2024-3112-RC1
- AC1: 'Reply on RC1', Vesna Bertoncelj, 23 Jan 2025
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3112/egusphere-2024-3112-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-3112-AC1
RC2:
'Comment on egusphere-2024-3112', Anonymous Referee #2, 15 Nov 2024

Bertoncelj et al. introduce SCARIBOS, a regional configuration of the CROCO ocean model for the South CARIBbean Ocean System with a kilometre-scale horizontal resolution of 1/100 degree. The authors use four years (2020-2024) of surface velocity fields output by the model to undertake three Lagrangian particle tracking experiments using the OceanParcels framework to explore the surface connectivity of flows surrounding the island of Curaçao. The Lagrangian experiments allow the authors to investigate potential hotspots of marine pollutants around Curaçao, intra-island coastal connectivity, and the connectivity between the Curaçao coast and the neighbouring Aruba, Bonaire, Venezuelan islands, and the Venezuelan mainland. The authors should be commended for the Figures, especially those relating to the Lagrangian analysis, which convey the central findings both clearly and creatively. The manuscript is generally well written, although a more comprehensive description of the numerical modelling approach (including validation), further exploration of the role of mesoscale eddies in driving surface connectivity, and an improved discussion on the limitations and wider relevance of the findings are needed. I would recommend the manuscript for publication subject to major revisions addressing the comments attached below and the excellent suggestions made by Reviewer #1.

Citation: https://doi.org/10.5194/egusphere-2024-3112-RC2
- AC2: 'Reply on RC2', Vesna Bertoncelj, 23 Jan 2025
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3112/egusphere-2024-3112-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-3112-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3112', Anonymous Referee #1, 08 Nov 2024

Bertoncelj et al. describe a 1/100 degree configuration of the CROCO ocean model for the Netherlands Antilles. Using four years of model surface current output combined with Lagrangian particle tracking experiments, they focus on the island of Curaçao and investigate (i) accumulation ‘hotspots’, (ii) intra-island connectivity, and (iii) the potential for nearby islands and the Venezuelan mainland to act as sources of pollutants for Curaçao. I enjoyed reading the manuscript and, assuming the model output is indeed made publicly available prior to publication, I imagine that these data will be valuable more broadly, for a part of the ocean that appears to be somewhat data sparse. I was particularly impressed with the quality of many of the figures. I recommend the manuscript for publication, but would ask the authors to consider the suggestions in the attached supplement, which can be considered as major revisions. These suggestions mainly relate to (i) more rigorous assessment of model hydrodynamics, and (ii) the clarity of some analyses/discussion, particularly relating to scenario 1.

Citation: https://doi.org/10.5194/egusphere-2024-3112-RC1
- AC1: 'Reply on RC1', Vesna Bertoncelj, 23 Jan 2025
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3112/egusphere-2024-3112-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-3112-AC1
RC2:
'Comment on egusphere-2024-3112', Anonymous Referee #2, 15 Nov 2024

Bertoncelj et al. introduce SCARIBOS, a regional configuration of the CROCO ocean model for the South CARIBbean Ocean System with a kilometre-scale horizontal resolution of 1/100 degree. The authors use four years (2020-2024) of surface velocity fields output by the model to undertake three Lagrangian particle tracking experiments using the OceanParcels framework to explore the surface connectivity of flows surrounding the island of Curaçao. The Lagrangian experiments allow the authors to investigate potential hotspots of marine pollutants around Curaçao, intra-island coastal connectivity, and the connectivity between the Curaçao coast and the neighbouring Aruba, Bonaire, Venezuelan islands, and the Venezuelan mainland. The authors should be commended for the Figures, especially those relating to the Lagrangian analysis, which convey the central findings both clearly and creatively. The manuscript is generally well written, although a more comprehensive description of the numerical modelling approach (including validation), further exploration of the role of mesoscale eddies in driving surface connectivity, and an improved discussion on the limitations and wider relevance of the findings are needed. I would recommend the manuscript for publication subject to major revisions addressing the comments attached below and the excellent suggestions made by Reviewer #1.

Citation: https://doi.org/10.5194/egusphere-2024-3112-RC2
- AC2: 'Reply on RC2', Vesna Bertoncelj, 23 Jan 2025
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3112/egusphere-2024-3112-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-3112-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Vesna Bertoncelj on behalf of the Authors (23 Jan 2025) Author's response

ED: Referee Nomination & Report Request started (24 Jan 2025) by Julian Mak

RR by Anonymous Referee #1 (30 Jan 2025)

Suggestions for revision or reasons for rejection

L65: I’d suggest changing “community model” to “ocean model” or “regional ocean model”.
L123: The precision for the grid dimensions (5 significant figures) feels excessive – the exact dimensions are in the model configuration file anyway. I would consider just writing 1.1 km.
L127: The EKE plot in the reviewers’ response was useful, and I think this is an important justification for the spin-up duration of 4 months. This figure (integrated EKE vs time) would ideally be included in the supplementary materials but, otherwise, I would at least mention this in the main text (i.e. that the 4 month duration allowed EKE to stabilise across the model domain).
L178-180: I don’t think this explanation for the difference between SCARIBOS and GlobCurrent is correct. GlobCurrent is based on observed SSH, so the effects of islands are included (since they exist in reality and therefore affect the observations) even if they are not resolved in the gridded GlobCurrent product. GlobCurrent can only capture the geostrophic and Ekman components of the surface flow, so it would not capture any ageostrophic effects of the islands on the flow. However, the differences between SCARIBOS and GlobCurrent are not just immediately around/downstream of the islands. SCARIBOS does not include data assimilation, so some differences will just be due to turbulence. There are some consistent differences though, e.g. most of the westward surface transport in GlobCurrent is north of the islands, whereas SCARIBOS simulates strong flow south of the islands as well. These differences are notable as they could affect the results of the manuscript.
L260: “when particle” -> “when a particle”, and “a grid” -> “a grid cell”
L310: I’m still not convinced by this mention of El Niño. The authors wrote in their response that they “believe it is possible that El Niño played a role in the different hydrodynamics in 2023 [because] there are notably more low-energy/eddy-dominated months”, but a 4-year simulation is nowhere near enough time to confidently attribute something to El Niño (as opposed to some other mode of variability or random chance). If there are other studies that investigate the impacts of El Niño on eddy activity in the region then please cite them and explain the connection, otherwise I do not think it is appropriate to mention El Niño.
L350: “origin” -> “origins” or “source regions”, and “Contrary” -> “Conversely” or “On the contrary”
Fig. 9: I preferred the old version of the figure where source=destination cells were filled, although I understand why the authors chose to block them out. However, I would at least suggest exporting sub-panels 9(b) and (c) as vectors, because the rasterised crosses don’t look great at low resolution.
L438: I’m struggling to see how the results of this study are being attributed to the Island Mass Effect. In the original figures, it looked like there was particle accumulation immediately downstream of the island, but this is no longer the case in the revised figure 8. There’s certainly perturbation of the flow, but the IME is more than just perturbation of the flow – it specifically relates to vertical movement. The authors wrote that they have further evidence for this which will be part of a future manuscript, but I am not reviewing that manuscript, and I can’t see convincing evidence for the IME in this manuscript.
L449-452: Similarly, I am still unconvinced about this comparison with the Sticky Water Effect. The authors have now clarified that the effect observed in this study is not the Sticky Water Effect… in which case, why mention it at all? Just describe the observations.
L466-471: I would remove this discussion of Lagrangian Coherent Structures from the manuscript. I can intuitively see why regions of higher normalized unique particle count might correspond with attracting LCS, but is this a physically rigorous way of identifying LCS? I am not familiar enough with LCS theory to answer that, but I suspect it is not. This would be an interesting future study, but this discussion feels out of place in the present manuscript given the lack of evidence provided. I certainly think the claim “This highlights the critical role that LCS play in shaping surface substance transport around Curaçao” should be removed, as should the Gomez-Navarro et al. 2024 reference (it does not use the same region or same method, so don’t see how it is relevant apart from the fact that it deals with LCS). The Haller (2015) reference is also missing from the reference list.
L509: I cannot see any evidence for the claim that “particles do not spread as far before leaving the area” – no particle dispersion metrics (e.g. Lyapunov exponents) were computed in this study.
L553-554: The mention of machine learning is a bit random. If the authors really want to include this then OK, but particle tracking is not particularly expensive in the first place, so I don’t see why this application is specifically notable.
Data availability: Is there a plan for how readers can access the full dataset if the two contacts were to leave their institution and no longer had access to these email addresses? Is there not a more sustainable solution for making this dataset available?

Hide

RR by Oliver Tooth (16 Feb 2025)

EF by Anna Mirena Feist-Polner (29 Jan 2025) Manuscript Author's tracked changes

ED: Publish subject to minor revisions (review by editor) (17 Feb 2025) by Julian Mak

AR by Vesna Bertoncelj on behalf of the Authors (11 Mar 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (12 Mar 2025) by Julian Mak

AR by Vesna Bertoncelj on behalf of the Authors (12 Mar 2025) Manuscript

Journal article(s) based on this preprint

27 May 2025

Flow patterns, hotspots, and connectivity of land-derived substances at the sea surface of Curaçao in the southern Caribbean

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

Ocean Sci., 21, 945–964, https://doi.org/10.5194/os-21-945-2025,https://doi.org/10.5194/os-21-945-2025, 2025

Short summary

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

Data sets

ADCP data for model validation Vesna Bertoncelj https://doi.org/10.25850/nioz/7b.b.xh

Detailed bathymetry around Curacao Data portal: EMODnet; Data collected during research expedition 64PE500 https://doi.org/10.12770/ff3aff8a-cff1-44a3-a2c8-1910bf109f85

Model code and software

SCARIBOS configuration scripts and analysis Vesna Bertoncelj https://github.com/OceanParcels/SCARIBOS_ConnectivityCuracao/

OceanParcels simulation scripts and analysis Vesna Bertoncelj https://github.com/OceanParcels/SCARIBOS_ConnectivityCuracao/

Vesna Bertoncelj, Furu Mienis, Paolo Stocchi, and Erik van Sebille

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Short summary

This study explores ocean currents around Curaçao and how land-derived substances like pollutants and nutrients travel in the water. Most substances move northwest, following the main current, but at times, ocean eddies spread them in other directions. This movement may link polluted areas to pristine coral reefs, impacting marine ecosystems. Understanding these patterns helps inform conservation and pollution management around Curaçao.


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