Pub Date : 2025-01-02DOI: 10.1016/j.jmarsys.2024.104036
Andréa de Lima Oliveira , Natália Rudorff , Shubha Sathyendranath , Fabio Dall Cortivo , Silvana Vianna Rodrigues , Daniela Sudatti , Milton Kampel
<div><div>Ocean colour remote sensing provides information on phytoplankton biomass at the global scale, indexed as chlorophyll-<em>a</em> concentration (Chl-<em>a</em>). Several models have also been developed to estimate phytoplankton size classes (PSCs) from ocean colour data. Here we evaluate an abundance-based (AB) model that relies on the total Chl-<em>a</em> as input and the spectral-based (SB) model that relies on the spectrally-resolved phytoplankton absorption coefficient (<span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>p</mi><mi>h</mi></mrow></msub></math></span>). The models were regionally adjusted using <em>in situ</em> data from a coastal time-series station in the South Brazil Bight, Southwestern Atlantic Ocean (ANTARES-Ubatuba). The regionally-adjusted models were applied to MODIS/Aqua images from 2002 to 2021, using the Generalized Inherent Optical Properties model (GIOP) to estimate Chl-<em>a</em> and <span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>p</mi><mi>h</mi></mrow></msub></math></span>. The satellite time series was used to analyse the spatio-temporal variability of phytoplankton size classes. A correlation analysis was then performed with annual mean sea surface temperature (SST), Chl-<em>a</em>, and micro and nanophytoplankton size fractions (<span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span>). The Multivariate El Niño-Southern Oscillation Index (MEI) was used to investigate the influence of the El Niño-Southern Oscillation (ENSO) in the study region. Both PSC models performed reasonably well when tested against an independent <em>in-situ</em> dataset collected in the study region, yielding a correlation coefficient <span><math><mrow><mi>ρ</mi><mo>></mo></mrow></math></span>0.6 and a <span><math><mi>p</mi></math></span>-value <span><math><mo><</mo></math></span>0.01. The AB model underestimated the Chl-<em>a</em> associated with the micro- and nano-sized classes (<span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span>) by 20%, while the SB model underestimated it by 48%. The AB model underestimated <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> by 12% and the SB by 6%. The satellite validation for the <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> showed an underestimation of 5% by the AB model and an overestimation of 18% by the SB model. A seasonal pattern was observed, with <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> dominating the inner shelf during the austral summer and spring, and extending to the entire shelf during the autumn and winter. The micro- and nano-sized fractions showed a significant negative correlation with SST, whereas MEI was positively correlated with Chl-<em>a</em> and <span><math><msub><mrow><mi>F</mi>
{"title":"Phytoplankton size structure in a subtropical area from ocean colour and its applications","authors":"Andréa de Lima Oliveira , Natália Rudorff , Shubha Sathyendranath , Fabio Dall Cortivo , Silvana Vianna Rodrigues , Daniela Sudatti , Milton Kampel","doi":"10.1016/j.jmarsys.2024.104036","DOIUrl":"10.1016/j.jmarsys.2024.104036","url":null,"abstract":"<div><div>Ocean colour remote sensing provides information on phytoplankton biomass at the global scale, indexed as chlorophyll-<em>a</em> concentration (Chl-<em>a</em>). Several models have also been developed to estimate phytoplankton size classes (PSCs) from ocean colour data. Here we evaluate an abundance-based (AB) model that relies on the total Chl-<em>a</em> as input and the spectral-based (SB) model that relies on the spectrally-resolved phytoplankton absorption coefficient (<span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>p</mi><mi>h</mi></mrow></msub></math></span>). The models were regionally adjusted using <em>in situ</em> data from a coastal time-series station in the South Brazil Bight, Southwestern Atlantic Ocean (ANTARES-Ubatuba). The regionally-adjusted models were applied to MODIS/Aqua images from 2002 to 2021, using the Generalized Inherent Optical Properties model (GIOP) to estimate Chl-<em>a</em> and <span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>p</mi><mi>h</mi></mrow></msub></math></span>. The satellite time series was used to analyse the spatio-temporal variability of phytoplankton size classes. A correlation analysis was then performed with annual mean sea surface temperature (SST), Chl-<em>a</em>, and micro and nanophytoplankton size fractions (<span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span>). The Multivariate El Niño-Southern Oscillation Index (MEI) was used to investigate the influence of the El Niño-Southern Oscillation (ENSO) in the study region. Both PSC models performed reasonably well when tested against an independent <em>in-situ</em> dataset collected in the study region, yielding a correlation coefficient <span><math><mrow><mi>ρ</mi><mo>></mo></mrow></math></span>0.6 and a <span><math><mi>p</mi></math></span>-value <span><math><mo><</mo></math></span>0.01. The AB model underestimated the Chl-<em>a</em> associated with the micro- and nano-sized classes (<span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span>) by 20%, while the SB model underestimated it by 48%. The AB model underestimated <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> by 12% and the SB by 6%. The satellite validation for the <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> showed an underestimation of 5% by the AB model and an overestimation of 18% by the SB model. A seasonal pattern was observed, with <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi><mo>,</mo><mi>n</mi></mrow></msub></math></span> dominating the inner shelf during the austral summer and spring, and extending to the entire shelf during the autumn and winter. The micro- and nano-sized fractions showed a significant negative correlation with SST, whereas MEI was positively correlated with Chl-<em>a</em> and <span><math><msub><mrow><mi>F</mi>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"248 ","pages":"Article 104036"},"PeriodicalIF":2.7,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143154631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104024
Théo Le Hir , Pierrick Penven , Thierry Huck , Romain Pellen , Maryline Moulin , Marina Rabineau , Daniel Aslanian
Paleobathymetric reconstructions suggest that 35 million years ago, local uplift of the Davie Ridge could have temporarily raised a continental land–bridge between Africa and Madagascar and dramatically affected their connectivity. Numerical simulations of a regional model of the southwest Indian Ocean at mesoscale resolution are performed to investigate the consequences of such a closure of the Mozambique Channel. Compared to a reference simulation of present day circulation, blocking the Mozambique Channel results in a redistribution of the transport around Madagascar dramatically strengthening the East Madagascar Current and eddy variability south of Madagascar, broadening the Agulhas Current, and modifying water mass properties and bottom circulation.
{"title":"Impacts of the closure of the Mozambique Channel on the southwest Indian Ocean circulation: A regional numerical simulation","authors":"Théo Le Hir , Pierrick Penven , Thierry Huck , Romain Pellen , Maryline Moulin , Marina Rabineau , Daniel Aslanian","doi":"10.1016/j.jmarsys.2024.104024","DOIUrl":"10.1016/j.jmarsys.2024.104024","url":null,"abstract":"<div><div>Paleobathymetric reconstructions suggest that 35 million years ago, local uplift of the Davie Ridge could have temporarily raised a continental land–bridge between Africa and Madagascar and dramatically affected their connectivity. Numerical simulations of a regional model of the southwest Indian Ocean at mesoscale resolution are performed to investigate the consequences of such a closure of the Mozambique Channel. Compared to a reference simulation of present day circulation, blocking the Mozambique Channel results in a redistribution of the transport around Madagascar dramatically strengthening the East Madagascar Current and eddy variability south of Madagascar, broadening the Agulhas Current, and modifying water mass properties and bottom circulation.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104024"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104037
Jingjing He , Songlin Yin , Xianyao Chen , Bo Yin , Xianqing Huang
Marine heatwaves (MHWs) are prolonged events of extreme sea surface temperature (SST) that have adverse effects on marine ecosystems and socio-economic aspects. Therefore, accurately and effectively predicting SST and MHW events in advance is crucial for mitigating their adverse effects. However, prediction of extreme events over the long term remains a significant challenge. In this study, we apply a deep-learning technique based on Informer, combined with the Empirical Orthogonal Function (EOF) and Empirical Mode Decomposition (EMD), named EOF-EMD-Informer, to improve the prediction of MHWs' occurrence on spatiotemporal scales. Extensive experiments in the Bohai Sea, based on daily satellite-observed SST, shows that the proposed Informer-based model outperforms recurrent neural networks and their variants in medium-term prediction of SST and MHWs' occurrence. The model performs well in predictions up to 30 days ahead, with a root mean square error of about 0.96 °C and an F1 score of about 0.93. About 51 % of the spatial grids have a root mean square error smaller than 0.55 °C with EOF-EMD-Informer model, representing an improvement of approximately 5 % and 27 % compared to the EMD-Informer and Informer models, respectively. This study serves as a proof of concept, demonstrating the potential applications of Informer-based methods in medium-term (up to at least 30 days) predictions of daily SST and MHWs and highlighting their effectiveness in extensive spatiotemporal predictions.
{"title":"An Informer-based prediction model for extensive spatiotemporal prediction of sea surface temperature and marine heatwave in Bohai Sea","authors":"Jingjing He , Songlin Yin , Xianyao Chen , Bo Yin , Xianqing Huang","doi":"10.1016/j.jmarsys.2024.104037","DOIUrl":"10.1016/j.jmarsys.2024.104037","url":null,"abstract":"<div><div>Marine heatwaves (MHWs) are prolonged events of extreme sea surface temperature (SST) that have adverse effects on marine ecosystems and socio-economic aspects. Therefore, accurately and effectively predicting SST and MHW events in advance is crucial for mitigating their adverse effects. However, prediction of extreme events over the long term remains a significant challenge. In this study, we apply a deep-learning technique based on Informer, combined with the Empirical Orthogonal Function (EOF) and Empirical Mode Decomposition (EMD), named EOF-EMD-Informer, to improve the prediction of MHWs' occurrence on spatiotemporal scales. Extensive experiments in the Bohai Sea, based on daily satellite-observed SST, shows that the proposed Informer-based model outperforms recurrent neural networks and their variants in medium-term prediction of SST and MHWs' occurrence. The model performs well in predictions up to 30 days ahead, with a root mean square error of about 0.96 °C and an F1 score of about 0.93. About 51 % of the spatial grids have a root mean square error smaller than 0.55 °C with EOF-EMD-Informer model, representing an improvement of approximately 5 % and 27 % compared to the EMD-Informer and Informer models, respectively. This study serves as a proof of concept, demonstrating the potential applications of Informer-based methods in medium-term (up to at least 30 days) predictions of daily SST and MHWs and highlighting their effectiveness in extensive spatiotemporal predictions.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104037"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104023
Juan F. Saad , Giuliana M. Burgueño , Gabriela N. Williams , Marianela Gastaldi , Patricio J. Pereyra , Raúl A. Gonzalez , Maite A. Narvarte , Viviana A. Alder
Macrotidal wetlands of temperate areas are highly productive systems where interactions between land and water are particularly dynamic. Typically, these systems display temporal shifts in their water properties not only because of annual fluctuations in the photoperiod and air temperature but also due to strong tidal regimes and climatic events. In contrast with the well-studied microtidal systems, the temporal fluctuations in structure and biomass of microbial communities of semi-desert, enclosed temperate macrotidal wetlands are scarcely known, and thus the coupling between primary producers and the bacterial community occurring within them remains poorly understood. In this study we analyze the fluctuations of unicellular plankton and hydrographic conditions on a fixed station located in San Antonio Bay (SAB, Northern Argentine Patagonia) from spring 2016 to early summer 2018 with the aim of detecting possible associations with the periodicity of some climatological variables and local meteorological events. Density and biomass of microbial size fractions (pico-, nano- and microplankton) along with their nutrition modes (autotrophic, potentially mixotrophic and heterotrophic) were assessed based on bi-weekly samplings. In addition, the study also examines the relationships of autotrophs and bacterioplankton with the frequency, duration, and magnitude of phytoplanktonic blooms, as well as the biomass contribution of dominant diatom species. We found a microbial-dominated planktonic system with increased densities of both autotrophic and heterotrophic picoplankton and flagellated protists. The biomass of potentially mixotrophs dominated over that of autotrophs and heterotrophs along the entire period. Autotrophic biomass showed a single annual maximum in summer, while chlorophyll-a displayed a biannual cycle. Neither chlorophyll-a nor autotrophic biomass reached high values as compared to other coastal systems with no clear dominant phytoplanktonic taxa. The annual phytoplanktonic biomass cycle in SAB appears not to be related to those of other coastal environments from North Patagonia. We infer that the strong macrotidal dynamics limits primary production and turns this system into a high nutrient/low chlorophyll one that exports surplus nutrients in tide-driven pulses to neighboring areas.
{"title":"Seasonal patterns of microbial plankton and periodicity of climatic and hydrographic conditions in a semi-desert macrotidal wetland","authors":"Juan F. Saad , Giuliana M. Burgueño , Gabriela N. Williams , Marianela Gastaldi , Patricio J. Pereyra , Raúl A. Gonzalez , Maite A. Narvarte , Viviana A. Alder","doi":"10.1016/j.jmarsys.2024.104023","DOIUrl":"10.1016/j.jmarsys.2024.104023","url":null,"abstract":"<div><div>Macrotidal wetlands of temperate areas are highly productive systems where interactions between land and water are particularly dynamic. Typically, these systems display temporal shifts in their water properties not only because of annual fluctuations in the photoperiod and air temperature but also due to strong tidal regimes and climatic events. In contrast with the well-studied microtidal systems, the temporal fluctuations in structure and biomass of microbial communities of semi-desert, enclosed temperate macrotidal wetlands are scarcely known, and thus the coupling between primary producers and the bacterial community occurring within them remains poorly understood. In this study we analyze the fluctuations of unicellular plankton and hydrographic conditions on a fixed station located in San Antonio Bay (SAB, Northern Argentine Patagonia) from spring 2016 to early summer 2018 with the aim of detecting possible associations with the periodicity of some climatological variables and local meteorological events. Density and biomass of microbial size fractions (pico-, nano- and microplankton) along with their nutrition modes (autotrophic, potentially mixotrophic and heterotrophic) were assessed based on bi-weekly samplings. In addition, the study also examines the relationships of autotrophs and bacterioplankton with the frequency, duration, and magnitude of phytoplanktonic blooms, as well as the biomass contribution of dominant diatom species. We found a microbial-dominated planktonic system with increased densities of both autotrophic and heterotrophic picoplankton and flagellated protists. The biomass of potentially mixotrophs dominated over that of autotrophs and heterotrophs along the entire period. Autotrophic biomass showed a single annual maximum in summer, while chlorophyll-<em>a</em> displayed a biannual cycle. Neither chlorophyll-<em>a</em> nor autotrophic biomass reached high values as compared to other coastal systems with no clear dominant phytoplanktonic taxa. The annual phytoplanktonic biomass cycle in SAB appears not to be related to those of other coastal environments from North Patagonia. We infer that the strong macrotidal dynamics limits primary production and turns this system into a high nutrient/low chlorophyll one that exports surplus nutrients in tide-driven pulses to neighboring areas.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104023"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hypoxic water (< 2 mL of O2 per L), which can cause mass mortality of demersal fishes, is reported to occur in the enclosed coastal area around the world. Funka Bay, a semi-enclosed and cone-shaped bay with a maximum depth of 107 m, located in the southern part of Hokkaido, Japan, also suffers summertime bottom hypoxic water. Long-term monitoring reveals that the occurrence is greatly variable year by year, yet the controlling factor is still unknown. The present study examined the interannual variability of summertime bottom dissolved oxygen (DO) with the focus on the wintertime heat loss of the water and subsequent convection overturning using year-round moored/ship-board DO observation for the period of 2012–2019. A common feature found in the 8 years was the continuous recovery of bottom DO in winter from the previous summer, which peaked February or March. The first half of the analysis period ceased the DO recovery until February, while one month extension of the DO recovery by March in the second half. The latter tended to show less hypoxia in the following summer as its peak is higher and its DO reduction phase starts later. Wintertime surface heat flux in February created the difference; more heat was lost in the second half because of warmer water temperature under the winter atmosphere. We were successful to predict summertime bottom DO with the accuracy of 0.26 mL/L considering the wintertime heat flux and stratification. This multi-month prediction will be of great help for future fishery activity in Funka Bay.
{"title":"Multi-month prediction of summertime hypoxia occurrence in the bottom of Funka Bay, Japan, with a focus on the wintertime surface heat flux","authors":"Chihiro Miki , Hiroto Abe , Hiroji Onishi , Atsushi Ooki , Tetsuya Takatsu","doi":"10.1016/j.jmarsys.2024.104035","DOIUrl":"10.1016/j.jmarsys.2024.104035","url":null,"abstract":"<div><div>Hypoxic water (< 2 mL of O<sub>2</sub> per L), which can cause mass mortality of demersal fishes, is reported to occur in the enclosed coastal area around the world. Funka Bay, a semi-enclosed and cone-shaped bay with a maximum depth of 107 m, located in the southern part of Hokkaido, Japan, also suffers summertime bottom hypoxic water. Long-term monitoring reveals that the occurrence is greatly variable year by year, yet the controlling factor is still unknown. The present study examined the interannual variability of summertime bottom dissolved oxygen (DO) with the focus on the wintertime heat loss of the water and subsequent convection overturning using year-round moored/ship-board DO observation for the period of 2012–2019. A common feature found in the 8 years was the continuous recovery of bottom DO in winter from the previous summer, which peaked February or March. The first half of the analysis period ceased the DO recovery until February, while one month extension of the DO recovery by March in the second half. The latter tended to show less hypoxia in the following summer as its peak is higher and its DO reduction phase starts later. Wintertime surface heat flux in February created the difference; more heat was lost in the second half because of warmer water temperature under the winter atmosphere. We were successful to predict summertime bottom DO with the accuracy of 0.26 mL/L considering the wintertime heat flux and stratification. This multi-month prediction will be of great help for future fishery activity in Funka Bay.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104035"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104025
Dag Myrhaug
{"title":"Comments on “Distributions, sea-to-air fluxes, and biological consumption of carbon monoxide in the Bohai and Yellow Seas during winter” by Lin Yang et al., J. Mar. Syst. 2024, 245, 103994","authors":"Dag Myrhaug","doi":"10.1016/j.jmarsys.2024.104025","DOIUrl":"10.1016/j.jmarsys.2024.104025","url":null,"abstract":"","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104025"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104022
Xuefeng Wu, Weiming Xie, Naiyu Zhang, Leicheng Guo, Qing He
Cold fronts are expected to exert a significant impact on hydrodynamics and sediment dynamics in estuaries, but the exact influence remains insufficiently understood. In this study, we provided an in-depth examination of cold front impact based on a 13-day in-situ observation in the South Passage of the Changjiang Estuary. We deployed two bottom-mounted tripod systems and several buoy stations to collect current velocities, wave heights, wind speeds, near-bottom suspended sediment concentrations (SSC), and bed level changes. Data analyses indicated that the maximum wind speed reached over 20 m/s, with significant wave heights of 1.38 m and 2.66 m inside and outside the South Passage, respectively. Wave-induced bed shear stress predominantly contributed to the total shear stress, and reached up to 0.81 N/m2 outside the South Passage. Near-bottom SSC increased by 31 % and 20 % inside and outside the South Passage, respectively, during the post-frontal period, compared to the frontal passage period. The cold front event intensified both the longitudinal circulation in the South Passage and the transverse transport intensity outside the South Passage, leading to a shift in sediment transport direction and landward sediment transport towards the South Passage during the post-frontal period. The cold-front-induced bed shear stress resulted in sediment resuspension in the submerged delta, thereby facilitating a more homogeneous vertical distribution of suspended sediment in the bottom boundary layer. These findings provide insights into the impact of episodic events on water-sediment exchanges at the estuary-ocean interface.
{"title":"Different response of hydrodynamics and near-bottom sediment transport to a cold front in the Changjiang Estuary and its submerged delta","authors":"Xuefeng Wu, Weiming Xie, Naiyu Zhang, Leicheng Guo, Qing He","doi":"10.1016/j.jmarsys.2024.104022","DOIUrl":"10.1016/j.jmarsys.2024.104022","url":null,"abstract":"<div><div>Cold fronts are expected to exert a significant impact on hydrodynamics and sediment dynamics in estuaries, but the exact influence remains insufficiently understood. In this study, we provided an in-depth examination of cold front impact based on a 13-day in-situ observation in the South Passage of the Changjiang Estuary. We deployed two bottom-mounted tripod systems and several buoy stations to collect current velocities, wave heights, wind speeds, near-bottom suspended sediment concentrations (SSC), and bed level changes. Data analyses indicated that the maximum wind speed reached over 20 m/s, with significant wave heights of 1.38 m and 2.66 m inside and outside the South Passage, respectively. Wave-induced bed shear stress predominantly contributed to the total shear stress, and reached up to 0.81 N/m<sup>2</sup> outside the South Passage. Near-bottom SSC increased by 31 % and 20 % inside and outside the South Passage, respectively, during the post-frontal period, compared to the frontal passage period. The cold front event intensified both the longitudinal circulation in the South Passage and the transverse transport intensity outside the South Passage, leading to a shift in sediment transport direction and landward sediment transport towards the South Passage during the post-frontal period. The cold-front-induced bed shear stress resulted in sediment resuspension in the submerged delta, thereby facilitating a more homogeneous vertical distribution of suspended sediment in the bottom boundary layer. These findings provide insights into the impact of episodic events on water-sediment exchanges at the estuary-ocean interface.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104022"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jmarsys.2024.104034
Chengyan Liu , Zhaomin Wang , Xi Liang , Xiang Li , Xianxian Han , Wenjin Sun , Yang Wu , Xichen Li , Chen Cheng
The Antarctic Slope Current (ASC), coupled with the Antarctic Slope Front (ASF), encircles Antarctica and is a roughly alongshore flow. Yet, the instabilities of the ASC/ASF can induce cross-slope exchanges. The ASC/ASF instabilities have been studied extensively in previous literature. However, the corresponding responsible mechanisms and influences still need to be further clarified. Based on an idealized eddy-resolving model, this study focuses on the instabilities of the ASC/ASF with constant open boundary forcing. The ASC/ASF is classified into three types: Fresh Shelf, Warm Shelf, and Dense Shelf. Focused on the Fresh Shelf and Dense Shelf cases, two high-resolution process-oriented numerical experiments are conducted to reveal the typical characteristics, the dynamic mechanisms, and the influences of instabilities. In the Fresh Shelf case, the instabilities are characterized by a submesoscale vortex train over the middle-lower slope, associated with the Topographic Rossby waves. In the Dense Shelf case, a mesoscale vortex train is present over the lower slope, and abundant filaments and jets can flow across the shelf break. The baroclinic instability greatly contributes to the generation of instabilities in the two cases, yet the barotropic instability contributes less to the instabilities in the Fresh Shelf case. Coherent eddies have been identified and significantly favor the hydrographic anomalies by the advection of water boluses retaining source water rather than the polarities of coherent eddies. Instabilities only contribute to exchanges across the continental rise in the Fresh Shelf case but effectively result in cross-slope exchanges in the Dense Shelf case.
{"title":"The instabilities of the Antarctic slope current in an idealized model","authors":"Chengyan Liu , Zhaomin Wang , Xi Liang , Xiang Li , Xianxian Han , Wenjin Sun , Yang Wu , Xichen Li , Chen Cheng","doi":"10.1016/j.jmarsys.2024.104034","DOIUrl":"10.1016/j.jmarsys.2024.104034","url":null,"abstract":"<div><div>The Antarctic Slope Current (ASC), coupled with the Antarctic Slope Front (ASF), encircles Antarctica and is a roughly alongshore flow. Yet, the instabilities of the ASC/ASF can induce cross-slope exchanges. The ASC/ASF instabilities have been studied extensively in previous literature. However, the corresponding responsible mechanisms and influences still need to be further clarified. Based on an idealized eddy-resolving model, this study focuses on the instabilities of the ASC/ASF with constant open boundary forcing. The ASC/ASF is classified into three types: Fresh Shelf, Warm Shelf, and Dense Shelf. Focused on the Fresh Shelf and Dense Shelf cases, two high-resolution process-oriented numerical experiments are conducted to reveal the typical characteristics, the dynamic mechanisms, and the influences of instabilities. In the Fresh Shelf case, the instabilities are characterized by a submesoscale vortex train over the middle-lower slope, associated with the Topographic Rossby waves. In the Dense Shelf case, a mesoscale vortex train is present over the lower slope, and abundant filaments and jets can flow across the shelf break. The baroclinic instability greatly contributes to the generation of instabilities in the two cases, yet the barotropic instability contributes less to the instabilities in the Fresh Shelf case. Coherent eddies have been identified and significantly favor the hydrographic anomalies by the advection of water boluses retaining source water rather than the polarities of coherent eddies. Instabilities only contribute to exchanges across the continental rise in the Fresh Shelf case but effectively result in cross-slope exchanges in the Dense Shelf case.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"247 ","pages":"Article 104034"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.jmarsys.2024.104020
Gerry Giliant Salamena , Jacobo Martín , Sem Likumahua , Ferdimon Kainama , Daniel Deonisius Pelasula , Intan Suci Nurhati
Interactions between the deep sea and steep-sloping oceanic islands generate physical processes with potential impacts on sediment resuspension and ocean productivity. While studies have been conducted in the open oceans, those focusing on oceanic islands of the deep Banda Sea in eastern Indonesia are lacking. Here, we present the first observational evidence of vertical mechanisms (i.e. internal tidal reflection, internal hydraulic jumps) at the highly supercritical slope in outer Ambon Bay (OAB) in Ambon Island – an oceanic island in the Banda Sea. A 23-h CTD yoyo experiment combined with ADCP measurements conducted during spring flood and ebb tides demonstrated tidally-varying vertical temperature, salinity and density profiles. During spring flood tide, incoming internal tides were reflected by OAB's highly supercritical slope back to the deep sea with isopycnals and isotherms showing sharp downward plunges (downward vertical velocity = 6.5–8.3 × 10−3 m/s), and the internal tidal amplitude reaching 90–110 m. The reflection during flood tide caused seaward overturning flow at deeper depths despite the prevailing landward flow at the upper layers. During spring ebb tide, internal hydraulic jumps (upward vertical velocity = 6.1–6.48 × 10−3 m/s) occurred to rebound the downward plunges of isopycnals and isotherms as flood tide relaxed with the observed amplitude of internal tides of 90 m. We also observed weakened seaward ebb flow during the isothermal uplifting (when hydraulic jumps occurred), and subsequent intensified landward flow at the end of spring ebb tide indicating strong upslope flow when isotherms reached the maximum shoaling depths. Taken together, the observed vertical mechanisms indicate the conservation of energy at the highly supercritical slope of OAB evident by the comparable vertical velocities. An embedded turbidity-chlorophyll profiler in the CTD reveals that internal tidal activities at the highly supercritical slopes OAB may induce bottom nepheloid layers, and influence ocean productivity by regulating the vertical distribution of phytoplankton biomass.
{"title":"Internal tidal dynamics and associated processes at highly supercritical slopes in Banda Sea: Lessons from the oceanic island of Ambon, eastern Indonesia","authors":"Gerry Giliant Salamena , Jacobo Martín , Sem Likumahua , Ferdimon Kainama , Daniel Deonisius Pelasula , Intan Suci Nurhati","doi":"10.1016/j.jmarsys.2024.104020","DOIUrl":"10.1016/j.jmarsys.2024.104020","url":null,"abstract":"<div><div>Interactions between the deep sea and steep-sloping oceanic islands generate physical processes with potential impacts on sediment resuspension and ocean productivity. While studies have been conducted in the open oceans, those focusing on oceanic islands of the deep Banda Sea in eastern Indonesia are lacking. Here, we present the first observational evidence of vertical mechanisms (i.e. internal tidal reflection, internal hydraulic jumps) at the highly supercritical slope in outer Ambon Bay (OAB) in Ambon Island – an oceanic island in the Banda Sea. A 23-h CTD yoyo experiment combined with ADCP measurements conducted during spring flood and ebb tides demonstrated tidally-varying vertical temperature, salinity and density profiles. During spring flood tide, incoming internal tides were reflected by OAB's highly supercritical slope back to the deep sea with isopycnals and isotherms showing sharp downward plunges (downward vertical velocity = 6.5–8.3 × 10<sup>−3</sup> m/s), and the internal tidal amplitude reaching 90–110 m. The reflection during flood tide caused seaward overturning flow at deeper depths despite the prevailing landward flow at the upper layers. During spring ebb tide, internal hydraulic jumps (upward vertical velocity = 6.1–6.48 × 10<sup>−3</sup> m/s) occurred to rebound the downward plunges of isopycnals and isotherms as flood tide relaxed with the observed amplitude of internal tides of 90 m. We also observed weakened seaward ebb flow during the isothermal uplifting (when hydraulic jumps occurred), and subsequent intensified landward flow at the end of spring ebb tide indicating strong upslope flow when isotherms reached the maximum shoaling depths. Taken together, the observed vertical mechanisms indicate the conservation of energy at the highly supercritical slope of OAB evident by the comparable vertical velocities. An embedded turbidity-chlorophyll profiler in the CTD reveals that internal tidal activities at the highly supercritical slopes OAB may induce bottom nepheloid layers, and influence ocean productivity by regulating the vertical distribution of phytoplankton biomass.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"246 ","pages":"Article 104020"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The vast diversity of marine phytoplankton, shaped by intricate water dynamics, remains poorly understood in the oligotrophic ocean. In situ studies reveal fine-scale dynamics affecting phytoplankton distribution, leading to abrupt shifts in abundance and biomass referred here as “phytoplankton community transitions” (PCTs). Using a simple nutrient–phytoplankton–zooplankton (NPZ) numerical model, our study proposes a theoretical framework to explain PCTs observed during an oceanographic cruise in the Mediterranean Sea. We consider both a homogeneous and a variable environment, respectively corresponding to the waters on both sides of a front and to the frontal area itself. In the model, PCTs between one community of smaller phytoplankton and one community of bigger phytoplankton are controlled by nutrient supply, but not directly: nutrient supply affects all compartments of the model and creates PCTs by combining bottom-up and top-down controls. This mechanism is observed for both constant (i.e., within a water mass) and pulsed (i.e., in the front) nutrient supply. These results are consistent with in situ observations of biomass proportion across a front. This theoretical framework helps to better understand and plan in situ observations in oceanic regions characterized by fine-scale dynamics and oligotrophic conditions.
{"title":"Fine-scale phytoplankton community transitions in the oligotrophic ocean: A Mediterranean Sea case study","authors":"Laurina Oms , Monique Messié , Jean-Christophe Poggiale , Gérald Grégori , Andrea Doglioli","doi":"10.1016/j.jmarsys.2024.104021","DOIUrl":"10.1016/j.jmarsys.2024.104021","url":null,"abstract":"<div><div>The vast diversity of marine phytoplankton, shaped by intricate water dynamics, remains poorly understood in the oligotrophic ocean. <em>In situ</em> studies reveal fine-scale dynamics affecting phytoplankton distribution, leading to abrupt shifts in abundance and biomass referred here as “phytoplankton community transitions” (PCTs). Using a simple nutrient–phytoplankton–zooplankton (NPZ) numerical model, our study proposes a theoretical framework to explain PCTs observed during an oceanographic cruise in the Mediterranean Sea. We consider both a homogeneous and a variable environment, respectively corresponding to the waters on both sides of a front and to the frontal area itself. In the model, PCTs between one community of smaller phytoplankton and one community of bigger phytoplankton are controlled by nutrient supply, but not directly: nutrient supply affects all compartments of the model and creates PCTs by combining bottom-up and top-down controls. This mechanism is observed for both constant (i.e., within a water mass) and pulsed (i.e., in the front) nutrient supply. These results are consistent with <em>in situ</em> observations of biomass proportion across a front. This theoretical framework helps to better understand and plan <em>in situ</em> observations in oceanic regions characterized by fine-scale dynamics and oligotrophic conditions.</div></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":"246 ","pages":"Article 104021"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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