Pub Date : 2024-10-18DOI: 10.1016/j.csr.2024.105341
Fumio Maruyama
We predicted the extreme value of the annual number of typhoons, tropical cyclones over the western North Pacific, approaching typhoons, and landing typhoons for 1951–2019 over Japan and the minimum central pressure for 1987–2020 using the extreme value theory. The generalized extreme value (GEV) distribution was used to fit the extreme indices. Various diagnostic plots for assessing the accuracy of the GEV model fitted to the annual number of typhoons, approaching typhoons, and landing typhoons are shown, and all four diagnostic plots support the fitted GEV model. The shape parameter ξ for the annual number of typhoons and approaching typhoons is negative, and the number of typhoons has a finite upper limit. The calculated upper limits were 44.5 and 23.2 for the annual number of typhoons and approaching typhoons, respectively. However, ξ in the number of landing typhoons was zero; therefore, the number of landing typhoons did not have a finite upper limit, and there was a possibility that a significant risk would occur. The number of typhoons increased for 1951–2019. The minimum central pressure of typhoons estimated using geostationary satellite images decreased for 1987–2020, and the number of strong typhoons increased. The annual number of violent typhoons ( 54 m/s) increased in the 2010s. The calculated limit of the minimum central pressure of the typhoon is 877 hPa. When the Pacific Decadal Oscillation (PDO) index is positive, more violent typhoons tend to occur.
{"title":"Analysis of the annual number of tropical cyclones over Japan using the extreme value theory","authors":"Fumio Maruyama","doi":"10.1016/j.csr.2024.105341","DOIUrl":"10.1016/j.csr.2024.105341","url":null,"abstract":"<div><div>We predicted the extreme value of the annual number of typhoons, tropical cyclones over the western North Pacific, approaching typhoons, and landing typhoons for 1951–2019 over Japan and the minimum central pressure for 1987–2020 using the extreme value theory. The generalized extreme value (GEV) distribution was used to fit the extreme indices. Various diagnostic plots for assessing the accuracy of the GEV model fitted to the annual number of typhoons, approaching typhoons, and landing typhoons are shown, and all four diagnostic plots support the fitted GEV model. The shape parameter ξ for the annual number of typhoons and approaching typhoons is negative, and the number of typhoons has a finite upper limit. The calculated upper limits were 44.5 and 23.2 for the annual number of typhoons and approaching typhoons, respectively. However, ξ in the number of landing typhoons was zero; therefore, the number of landing typhoons did not have a finite upper limit, and there was a possibility that a significant risk would occur. The number of typhoons increased for 1951–2019. The minimum central pressure of typhoons estimated using geostationary satellite images decreased for 1987–2020, and the number of strong typhoons increased. The annual number of violent typhoons (<span><math><mrow><mo>≥</mo></mrow></math></span> 54 m/s) increased in the 2010s. The calculated limit of the minimum central pressure of the typhoon is 877 hPa. When the Pacific Decadal Oscillation (PDO) index is positive, more violent typhoons tend to occur.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105341"},"PeriodicalIF":2.1,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528860","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 : 2024-10-09DOI: 10.1016/j.csr.2024.105340
Markus Ausmeel , Martin Liira , Päärn Paiste , Aivo Lepland , Sten Suuroja
Phosphorus fractions and their vertical distribution in seabed sediments were studied in short cores from four coastal sites of western Estonia (Western Gulf of Finland, Väinameri Sea, Suur Strait, and Gulf of Riga) representing accumulation and erosion/transport settings. As a result of recent large-scale discharges of nutrients into the marine environment, abundant phosphorus has accumulated in the seabed sediments, from where it can, under the expansion of hypoxic or anoxic conditions, be remobilized and released back into the water column. A sequential extraction method with a neutral, a reducing, a basis, and an acidic solution was used to evaluate the distribution of phosphorous in pools of five different carrier fractions. Potentially mobile phosphorus is mostly associated with redox-sensitive iron- and manganese oxyhydroxides, and this fraction is significant in the Western Gulf of Finland and the Gulf of Riga. As oxygen conditions gradually deteriorate, the remobilization of a considerable amount of potentially mobile phosphorus from sediments can affect the entire Baltic Sea ecosystem.
{"title":"Phosphorus fractions and their vertical distribution in seabed sediments of the eastern Baltic Sea","authors":"Markus Ausmeel , Martin Liira , Päärn Paiste , Aivo Lepland , Sten Suuroja","doi":"10.1016/j.csr.2024.105340","DOIUrl":"10.1016/j.csr.2024.105340","url":null,"abstract":"<div><div>Phosphorus fractions and their vertical distribution in seabed sediments were studied in short cores from four coastal sites of western Estonia (Western Gulf of Finland, Väinameri Sea, Suur Strait, and Gulf of Riga) representing accumulation and erosion/transport settings. As a result of recent large-scale discharges of nutrients into the marine environment, abundant phosphorus has accumulated in the seabed sediments, from where it can, under the expansion of hypoxic or anoxic conditions, be remobilized and released back into the water column. A sequential extraction method with a neutral, a reducing, a basis, and an acidic solution was used to evaluate the distribution of phosphorous in pools of five different carrier fractions. Potentially mobile phosphorus is mostly associated with redox-sensitive iron- and manganese oxyhydroxides, and this fraction is significant in the Western Gulf of Finland and the Gulf of Riga. As oxygen conditions gradually deteriorate, the remobilization of a considerable amount of potentially mobile phosphorus from sediments can affect the entire Baltic Sea ecosystem.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105340"},"PeriodicalIF":2.1,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440965","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 : 2024-10-05DOI: 10.1016/j.csr.2024.105337
Nai-Chen Chen , Matt O'Regan , Wei-Li Hong , Thomas Andrén , Valentí Rodellas , Florian Roth , Carl-Magnus Mörth , Carl Regnéll , Hanna Sofia Marxen , Sophie ten Hietbrink , Tzu-Hao Huang , Richard Gyllencreautz , Christian Stranne , Anna Linderholm , Jordi Garcia-Orellana , Christoph Humborg , Martin Jakobsson
Submarine groundwater discharge (SGD) is an important process responsible for transporting terrestrial dissolved chemical substances into the coastal ocean, thereby impacting the marine ecosystem. Despites its significance, there are few studies addressing SGD in the northern Baltic Sea. Here we investigate the potential occurrence of SGD in an area characterized by seafloor terraces formed in varved glacial clay located around Fifång Island, Southern Stockholm Archipelago. We analyzed 222Rn activity and porewater geochemistry in both marine and terrestrial sediment cores retrieved from Fifång Island and its surrounding offshore areas. Results from 222Rn mass-balance calculations, water isotopes, salinity, chloride concentration, and dating (including 14C and helium-tritium dating) indicate that modern groundwater flows through varved glacial clay layers and fractured rocks on Fifång Island and discharges into Fifång Bay. Additionally, the offshore cores reveal a saline groundwater source that, dating of the dissolved inorganic carbon, appears systematically younger than the hosting clay varves dated using the Swedish clay varve chronology. Acoustic blanking in our acquired sub-bottom profiles may be related to this fluid migration. The occurrence of this saline groundwater seems to be independent from the distance to the submarine terraces. Collectively, our study confirms the occurrence of submarine groundwater in the varved glacial clay close to Fifång Island and further offshore. Our findings help establish the significance of submarine groundwater discharge in influencing the past and present coastal environment in the Baltic Sea region.
{"title":"Investigation of submarine groundwater discharge into the Baltic Sea through varved glacial clays","authors":"Nai-Chen Chen , Matt O'Regan , Wei-Li Hong , Thomas Andrén , Valentí Rodellas , Florian Roth , Carl-Magnus Mörth , Carl Regnéll , Hanna Sofia Marxen , Sophie ten Hietbrink , Tzu-Hao Huang , Richard Gyllencreautz , Christian Stranne , Anna Linderholm , Jordi Garcia-Orellana , Christoph Humborg , Martin Jakobsson","doi":"10.1016/j.csr.2024.105337","DOIUrl":"10.1016/j.csr.2024.105337","url":null,"abstract":"<div><div>Submarine groundwater discharge (SGD) is an important process responsible for transporting terrestrial dissolved chemical substances into the coastal ocean, thereby impacting the marine ecosystem. Despites its significance, there are few studies addressing SGD in the northern Baltic Sea. Here we investigate the potential occurrence of SGD in an area characterized by seafloor terraces formed in varved glacial clay located around Fifång Island, Southern Stockholm Archipelago. We analyzed <sup>222</sup>Rn activity and porewater geochemistry in both marine and terrestrial sediment cores retrieved from Fifång Island and its surrounding offshore areas. Results from <sup>222</sup>Rn mass-balance calculations, water isotopes, salinity, chloride concentration, and dating (including <sup>14</sup>C and helium-tritium dating) indicate that modern groundwater flows through varved glacial clay layers and fractured rocks on Fifång Island and discharges into Fifång Bay. Additionally, the offshore cores reveal a saline groundwater source that, dating of the dissolved inorganic carbon, appears systematically younger than the hosting clay varves dated using the Swedish clay varve chronology. Acoustic blanking in our acquired sub-bottom profiles may be related to this fluid migration. The occurrence of this saline groundwater seems to be independent from the distance to the submarine terraces. Collectively, our study confirms the occurrence of submarine groundwater in the varved glacial clay close to Fifång Island and further offshore. Our findings help establish the significance of submarine groundwater discharge in influencing the past and present coastal environment in the Baltic Sea region.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105337"},"PeriodicalIF":2.1,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418250","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 : 2024-10-05DOI: 10.1016/j.csr.2024.105339
Paul G. Harnik , Anne Chao , Katie S. Collins , Marina C. Rillo
Coastal eutrophication and hypoxia are growing challenges globally, yet their impacts can be difficult to evaluate because of limited biomonitoring that typically postdates the onset of these stressors. We address this limitation by investigating how the taxonomic and functional diversity of marine bivalve communities vary with primary productivity, dissolved oxygen, temperature, and seafloor sediment properties across the northern Gulf of Mexico, a region that includes one of the world's largest dead zones. We hypothesized that taxonomic and functional richness would decline in eutrophic and hypoxic coastal environments. Live bivalve mollusks were sampled at 15 stations, spanning more than 600 km of continental shelf habitat. Individuals were identified to species and characterized based on feeding, mobility, fixation, life position relative to the sediment-water interface, and body size. Alpha and beta taxonomic and functional diversity were computed using Hill numbers and linear models used to assess their covariation with regional environmental conditions. Taxonomic and functional diversity were highest in less eutrophic environments characterized by normoxic conditions, and lowest in more eutrophic environments where oxygen was more limited. Community-level differences were underlain by functional shifts, with abundant shallow-infaunal, deposit and mixed feeders in more eutrophic settings, in contrast with less eutrophic settings where suspension feeders were more abundant. Median body size increased with eutrophication, possibly as a result of hypoxia-induced declines in predator and competitor populations. These results suggest that intensifying nutrient loading and deoxygenation in the coastal zone will cause declines in multiple dimensions of benthic biodiversity with implications for ecosystem function.
{"title":"Declining bivalve species and functional diversity along a coastal eutrophication-deoxygenation gradient in the northern Gulf of Mexico","authors":"Paul G. Harnik , Anne Chao , Katie S. Collins , Marina C. Rillo","doi":"10.1016/j.csr.2024.105339","DOIUrl":"10.1016/j.csr.2024.105339","url":null,"abstract":"<div><div>Coastal eutrophication and hypoxia are growing challenges globally, yet their impacts can be difficult to evaluate because of limited biomonitoring that typically postdates the onset of these stressors. We address this limitation by investigating how the taxonomic and functional diversity of marine bivalve communities vary with primary productivity, dissolved oxygen, temperature, and seafloor sediment properties across the northern Gulf of Mexico, a region that includes one of the world's largest dead zones. We hypothesized that taxonomic and functional richness would decline in eutrophic and hypoxic coastal environments. Live bivalve mollusks were sampled at 15 stations, spanning more than 600 km of continental shelf habitat. Individuals were identified to species and characterized based on feeding, mobility, fixation, life position relative to the sediment-water interface, and body size. Alpha and beta taxonomic and functional diversity were computed using Hill numbers and linear models used to assess their covariation with regional environmental conditions. Taxonomic and functional diversity were highest in less eutrophic environments characterized by normoxic conditions, and lowest in more eutrophic environments where oxygen was more limited. Community-level differences were underlain by functional shifts, with abundant shallow-infaunal, deposit and mixed feeders in more eutrophic settings, in contrast with less eutrophic settings where suspension feeders were more abundant. Median body size increased with eutrophication, possibly as a result of hypoxia-induced declines in predator and competitor populations. These results suggest that intensifying nutrient loading and deoxygenation in the coastal zone will cause declines in multiple dimensions of benthic biodiversity with implications for ecosystem function.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105339"},"PeriodicalIF":2.1,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418219","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 : 2024-10-02DOI: 10.1016/j.csr.2024.105338
Vladimir Yakovenko, Nickolai Shadrin, Elena Anufriieva
Ecosystems in the shallow marine hypersaline environment, such as marine lakes, are among the most changeable and have significantly lower species richness than freshwater and marine. It could be assumed that the intricate interconnections in hypersaline water ecosystems are easier to understand than in other aquatic ecosystems. Interannual differences vs small-scale spatiotemporal variabilities were studied in the spring zooplankton of hypersaline Lake Moynaki from 2019 to 2023. Salinity, water temperature, wind speed and direction were measured along with zooplankton sampling. The average spring wind speed and water temperature varied significantly from year to year, seemingly with a certain cyclicity. In total, 17 species were noted in zooplankton. The copepods Acanthocyclops vernalis and Arctodiaptomus salinus were not previously recorded in the lake. Bottom species were found in the plankton, among which the oligochaete Nais pseudobtusa, the gastropod Bittium reticulatum, and dragonfly larvae Gomphus sp. had not previously been found in the lake. Only four species, Gammarus aequicauda, Eucypris mareotica, Moina salina, and Cletocamptus retrogressus were regularly observed en masse. On average, the total zooplankton abundance near the windward shore was 2 times higher than that near the leeward shore and the abundance of individual species was from 2 to 5 times higher. If the values near only one coast were used, then the range of interannual differences would be underestimated or overestimated by approximately 2–4 times. Based on the zooplankton similarity in different years, all years except 2019, are grouped into a single cluster. Various changes are occurring in the lake, which are difficult to present as a complete picture of the cause-and-effect relationships that determine them.
{"title":"Interannual differences vs small-scale spatiotemporal variability of spring zooplankton in the Crimean marine hypersaline lake","authors":"Vladimir Yakovenko, Nickolai Shadrin, Elena Anufriieva","doi":"10.1016/j.csr.2024.105338","DOIUrl":"10.1016/j.csr.2024.105338","url":null,"abstract":"<div><div>Ecosystems in the shallow marine hypersaline environment, such as marine lakes, are among the most changeable and have significantly lower species richness than freshwater and marine. It could be assumed that the intricate interconnections in hypersaline water ecosystems are easier to understand than in other aquatic ecosystems. Interannual differences <em>vs</em> small-scale spatiotemporal variabilities were studied in the spring zooplankton of hypersaline Lake Moynaki from 2019 to 2023. Salinity, water temperature, wind speed and direction were measured along with zooplankton sampling. The average spring wind speed and water temperature varied significantly from year to year, seemingly with a certain cyclicity. In total, 17 species were noted in zooplankton. The copepods <em>Acanthocyclops vernalis</em> and <em>Arctodiaptomus salinus</em> were not previously recorded in the lake. Bottom species were found in the plankton, among which the oligochaete <em>Nais pseudobtusa</em>, the gastropod <em>Bittium reticulatum</em>, and dragonfly larvae <em>Gomphus</em> sp. had not previously been found in the lake. Only four species, <em>Gammarus aequicauda</em>, <em>Eucypris mareotica</em>, <em>Moina salina</em>, and <em>Cletocamptus retrogressus</em> were regularly observed en masse. On average, the total zooplankton abundance near the windward shore was 2 times higher than that near the leeward shore and the abundance of individual species was from 2 to 5 times higher. If the values near only one coast were used, then the range of interannual differences would be underestimated or overestimated by approximately 2–4 times. Based on the zooplankton similarity in different years, all years except 2019, are grouped into a single cluster. Various changes are occurring in the lake, which are difficult to present as a complete picture of the cause-and-effect relationships that determine them.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105338"},"PeriodicalIF":2.1,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418249","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 : 2024-09-28DOI: 10.1016/j.csr.2024.105335
Odette A. Vergara , Pedro A. Figueroa , Cristian Salas , Sebastián I. Vásquez , Richard Muñoz , Gonzalo S. Saldías
The influence of Biobio Canyon on the circulation and coastal upwelling and downwelling was evaluated by using high-resolution hydrodynamic simulations of the coastal ocean off central Chile, a highly productive zone of the Southern Humboldt Current System that supports important coastal ecosystem services. The model bathymetry was GEBCO 2020 with a spatial resolution of 500 m, which allows a relatively fine representation of the complex topography of the region. To understand the role of the Biobio Canyon, contrasting experiments were run. A Reference Simulation (RS) considering the canyon bathymetry and the Biobio River discharge, a Simulation Experiment 1 (SE1) considering only the canyon bathymetry without the Biobio River discharge, and a Simulation Experiment 2 (SE2) only with the Biobio River discharge (without the canyon). During upwelling conditions, the characteristic asymmetry in the along-canyon circulation was observed, with onshore flow over the northern side of the canyon and most of the upper water column, and offshore flow over the upstream canyon wall. In contrast, the cross-shore flow was limited to a narrow band over the northern wall of the canyon in RS and SE1 during downwelling conditions. Not many differences were detected between the RS and SE1 during both upwelling and downwelling conditions, which suggest that the canyon imposes a major effect on the circulation in comparison to the river discharge. Our results exhibit a net onshore transport onto the continental shelf during coastal upwelling and, net offshore transport restricted to the area south of the canyon during downwelling conditions. Finally, the advection of high-density waters on the northern shelf dominates during upwelling conditions in RS and SE1. Similarly, presence of the canyon promotes higher bottom density over the shelf even during downwelling conditions, as compared to the no-canyon experiment.
{"title":"The influence of the Biobio Canyon on the circulation and coastal upwelling/downwelling off central Chile","authors":"Odette A. Vergara , Pedro A. Figueroa , Cristian Salas , Sebastián I. Vásquez , Richard Muñoz , Gonzalo S. Saldías","doi":"10.1016/j.csr.2024.105335","DOIUrl":"10.1016/j.csr.2024.105335","url":null,"abstract":"<div><div>The influence of Biobio Canyon on the circulation and coastal upwelling and downwelling was evaluated by using high-resolution hydrodynamic simulations of the coastal ocean off central Chile, a highly productive zone of the Southern Humboldt Current System that supports important coastal ecosystem services. The model bathymetry was GEBCO 2020 with a spatial resolution of 500 m, which allows a relatively fine representation of the complex topography of the region. To understand the role of the Biobio Canyon, contrasting experiments were run. A Reference Simulation (RS) considering the canyon bathymetry and the Biobio River discharge, a Simulation Experiment 1 (SE1) considering only the canyon bathymetry without the Biobio River discharge, and a Simulation Experiment 2 (SE2) only with the Biobio River discharge (without the canyon). During upwelling conditions, the characteristic asymmetry in the along-canyon circulation was observed, with onshore flow over the northern side of the canyon and most of the upper water column, and offshore flow over the upstream canyon wall. In contrast, the cross-shore flow was limited to a narrow band over the northern wall of the canyon in RS and SE1 during downwelling conditions. Not many differences were detected between the RS and SE1 during both upwelling and downwelling conditions, which suggest that the canyon imposes a major effect on the circulation in comparison to the river discharge. Our results exhibit a net onshore transport onto the continental shelf during coastal upwelling and, net offshore transport restricted to the area south of the canyon during downwelling conditions. Finally, the advection of high-density waters on the northern shelf dominates during upwelling conditions in RS and SE1. Similarly, presence of the canyon promotes higher bottom density over the shelf even during downwelling conditions, as compared to the no-canyon experiment.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105335"},"PeriodicalIF":2.1,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418765","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 : 2024-09-27DOI: 10.1016/j.csr.2024.105334
Mélanie Diaz , Florent Grasso , Aldo Sottolichio , Pierre Le Hir , Matthieu Caillaud
Shelf mud patches represent major sinks for fine-grained particles on continental shelves, as well as for carbon and contaminants of continental origin. The West Gironde Mud Patch (WGMP) is an interesting example of such offshore marine systems as it is an active mud deposition area located offshore the Gironde estuarine mouth (France) at depths between 30 and 70 m. It is known to be the trap of fine particles coming from the estuary, but the contribution of this material to the total mass of the depocenter is poorly quantified. In addition, despite the economic and ecological issues at stake, the response of such subtidal sedimentary structure to the combination of tidal currents, waves, and river supply remain poorly understood. Thus, using a realistic 3-D hydrodynamic and mixed (mud/sand) sediment transport model, this study aims at investigating the sediment dynamics of the WGMP under different hydrometeorological conditions. The analysis of the residual fluxes at the estuarine mouth exhibited large discrepancies between the different sediment classes as well as for contrasted hydro-and meteorological conditions induced by different dominant transport mechanisms. During winter, the reinforced density gradients drive strong up-estuary baroclinic circulation at the bottom that dominates the sediment dynamics over the barotropic export of mud particles. The model also reproduced the signature of a subtidal mud accumulation area over the continental shelf around 30–40 m water depth, on the proximal side of the observed WGMP. On average over two years, 26% of the mud mass accumulating on the simulated subtidal mudflat comes from the estuary. The trapping efficiency of this mud patch is negatively correlated with the significant wave height. Moreover, due to the estuarine turbid plume being more concentrated and developed at the surface during high river discharge, the trapping efficiency of the mud body is enhanced compared to lower discharge. This study highlights the sensitivity of mud and sand fluxes to vertical and horizontal residual circulation, and points out the uncertainties associated with the simulation of short-term (i.e., years) fine particle deposits compared to long-term (i.e., centuries) sediment accumulation trends. In addition, these results show the primordial effects of both wave action and riverine sediment supply on the dynamics of such subtidal muddy structures, which raises concern about their fate facing climate change and human activities in the future.
{"title":"Investigating sediment dynamics on a continental shelf mud patch under the influence of a macrotidal estuary: A numerical modeling analysis","authors":"Mélanie Diaz , Florent Grasso , Aldo Sottolichio , Pierre Le Hir , Matthieu Caillaud","doi":"10.1016/j.csr.2024.105334","DOIUrl":"10.1016/j.csr.2024.105334","url":null,"abstract":"<div><div>Shelf mud patches represent major sinks for fine-grained particles on continental shelves, as well as for carbon and contaminants of continental origin. The West Gironde Mud Patch (WGMP) is an interesting example of such offshore marine systems as it is an active mud deposition area located offshore the Gironde estuarine mouth (France) at depths between 30 and 70 m. It is known to be the trap of fine particles coming from the estuary, but the contribution of this material to the total mass of the depocenter is poorly quantified. In addition, despite the economic and ecological issues at stake, the response of such subtidal sedimentary structure to the combination of tidal currents, waves, and river supply remain poorly understood. Thus, using a realistic 3-D hydrodynamic and mixed (mud/sand) sediment transport model, this study aims at investigating the sediment dynamics of the WGMP under different hydrometeorological conditions. The analysis of the residual fluxes at the estuarine mouth exhibited large discrepancies between the different sediment classes as well as for contrasted hydro-and meteorological conditions induced by different dominant transport mechanisms. During winter, the reinforced density gradients drive strong up-estuary baroclinic circulation at the bottom that dominates the sediment dynamics over the barotropic export of mud particles. The model also reproduced the signature of a subtidal mud accumulation area over the continental shelf around 30–40 m water depth, on the proximal side of the observed WGMP. On average over two years, 26% of the mud mass accumulating on the simulated subtidal mudflat comes from the estuary. The trapping efficiency of this mud patch is negatively correlated with the significant wave height. Moreover, due to the estuarine turbid plume being more concentrated and developed at the surface during high river discharge, the trapping efficiency of the mud body is enhanced compared to lower discharge. This study highlights the sensitivity of mud and sand fluxes to vertical and horizontal residual circulation, and points out the uncertainties associated with the simulation of short-term (<em>i.e.,</em> years) fine particle deposits compared to long-term (<em>i.e.,</em> centuries) sediment accumulation trends. In addition, these results show the primordial effects of both wave action and riverine sediment supply on the dynamics of such subtidal muddy structures, which raises concern about their fate facing climate change and human activities in the future.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105334"},"PeriodicalIF":2.1,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418358","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 : 2024-09-26DOI: 10.1016/j.csr.2024.105336
S.A. Seregin, E.V. Popova, S.B. Krasheninnikova
Based on continuous 12-year (2010–2021) monitoring of the average summer abundance of small metazooplankton (SMZ) in the coastal zone of the Southwestern Crimea, the patterns of its interannual fluctuations were investigated. The total SMZ abundance during the study period varied from 37.8 to 176.0 thousand·m−3 in the open coastal area (on average, 104.0 ± 49.2 thousand·m−3) and from 90.3 to 556.8 thousand·m−3 at the bay mouth (on average, 264.5 ± 121.0 thousand·m−3). The crustacean fraction accounted for 85–91% of the total SMZ abundance. Principal component analysis (PCA) showed a noticeable contribution of 48 % of total temperatures and wind speed and different direction repeatability to the SMZ abundance variability. For native data, significant relationships were revealed between the abundance of individual SMZ fractions and hydrometeorological parameters: total temperatures of the warm period of the year (May–October), periodicity of the southern and southwestern, northern winds, calm conditions (events of the absence of wind), and the summer index of the North Atlantic Oscillation (NAO) with a 1-year lag. The application of fast Fourier transform (FFT) with a Hamming filter to the original series and periodograms analysis allowed revealing typical periods of variability in SMZ abundance and hydrometeorological parameters of the environment: 2–4-year and 5–6-year ones. At these scales, a higher number of significant relationships was established with the indicated hydrometeorological parameters, inter alia winter and summer NAO indices, than during the analysis of the original series. The total contribution of hydrometeorological and climatic factors to the variation in the abundance of SMZ increased to 78–79 %. This confirms the assumption that the relationship between SMZ and environmental parameters is characterized by its own features at different scales. Analysis of long-term SMZ different fractions tendencies for Summer 2010–2021, according to the Mann-Kendall criterion, did not show significant results.
{"title":"Dynamics of small metazooplankton in relation with environmental factors: A 12-year study in the coastal zone of the Southwestern Crimea (the Black Sea)","authors":"S.A. Seregin, E.V. Popova, S.B. Krasheninnikova","doi":"10.1016/j.csr.2024.105336","DOIUrl":"10.1016/j.csr.2024.105336","url":null,"abstract":"<div><div>Based on continuous 12-year (2010–2021) monitoring of the average summer abundance of small metazooplankton (SMZ) in the coastal zone of the Southwestern Crimea, the patterns of its interannual fluctuations were investigated. The total SMZ abundance during the study period varied from 37.8 to 176.0 thousand·m<sup>−3</sup> in the open coastal area (on average, 104.0 ± 49.2 thousand·m<sup>−3</sup>) and from 90.3 to 556.8 thousand·m<sup>−3</sup> at the bay mouth (on average, 264.5 ± 121.0 thousand·m<sup>−3</sup>). The crustacean fraction accounted for 85–91% of the total SMZ abundance. Principal component analysis (PCA) showed a noticeable contribution of 48 % of total temperatures and wind speed and different direction repeatability to the SMZ abundance variability. For native data, significant relationships were revealed between the abundance of individual SMZ fractions and hydrometeorological parameters: total temperatures of the warm period of the year (May–October), periodicity of the southern and southwestern, northern winds, calm conditions (events of the absence of wind), and the summer index of the North Atlantic Oscillation (NAO) with a 1-year lag. The application of fast Fourier transform (FFT) with a Hamming filter to the original series and periodograms analysis allowed revealing typical periods of variability in SMZ abundance and hydrometeorological parameters of the environment: 2–4-year and 5–6-year ones. At these scales, a higher number of significant relationships was established with the indicated hydrometeorological parameters, <em>inter alia</em> winter and summer NAO indices, than during the analysis of the original series. The total contribution of hydrometeorological and climatic factors to the variation in the abundance of SMZ increased to 78–79 %. This confirms the assumption that the relationship between SMZ and environmental parameters is characterized by its own features at different scales. Analysis of long-term SMZ different fractions tendencies for Summer 2010–2021, according to the Mann-Kendall criterion, did not show significant results.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105336"},"PeriodicalIF":2.1,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418766","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 : 2024-09-19DOI: 10.1016/j.csr.2024.105333
Bingjie Sun , Shengfa Liu , Ashraf Ali Seddique , Kaikai Wu , Wenjing Qi , Hui Zhang , Peng Cao , Jianguo Liu , Xuefa Shi
The Ganges Submarine Delta is a key land-sea transitional area in the northeastern Indian Ocean. An understanding of sediment distribution, provenance, and transportation in this area is of great importance for understanding its sedimentary environment and the sediment “source-sink” system of the northeastern Indian Ocean. This study aimed to identify the provenances and transport patterns of fine-grained sediments in the Ganges Submarine Delta through analysis of the grain size and clay mineral content of 84 surface sediment samples. Sediment illite, chlorite, kaolinite, and smectite contents were ∼66%, 18%, 11%, and 5%, respectively. Sediment illite content decreased from north to south; smectite and chlorite decreased and increased from northwest to southeast, respectively; kaolinite content was highest in the south. Spatial cluster analysis of the four clay minerals grouped the study area into two provinces: province I in the north is characterized by a clay mineral assemblage similar to that of the Ganges-Brahmaputra rivers; province II in the south is characterized by deep water and changes to clay mineral characteristics due to the mixing of material originating from the Indian Peninsula. This study used the illite/(smectite + chlorite + kaolinite) and kaolinite/illite ratios to discuss sediment transport paths in the two provinces. Himalayan material is widely distributed throughout the study area, and mainly transported from the estuary to the southwestern area by the tides, plume, and monsoons; sediments of the Mahanadi river are transported from southwest to northeast by the southwest monsoon, thereby affecting the sediment composition of province II.
恒河海底三角洲是印度洋东北部一个重要的陆海过渡区。了解该地区沉积物的分布、来源和迁移情况，对于了解其沉积环境和印度洋东北部的沉积物 "源-汇 "系统具有重要意义。本研究旨在通过分析 84 个表层沉积物样本的粒度和粘土矿物含量，确定恒河海底三角洲细粒沉积物的来源和迁移模式。沉积物中伊利石、绿泥石、高岭石和直闪石的含量分别为 66%、18%、11% 和 5%。沉积物伊利石含量由北向南递减；叶腊石和绿泥石含量分别由西北向东南递减和递增；高岭石含量以南部最高。通过对四种粘土矿物的空间聚类分析，将研究区域划分为两个区域：北部的 I 区具有与恒河-布拉马普特拉河粘土矿物组合相似的特征；南部的 II 区具有深水特征，由于来自印度半岛的物质混合，粘土矿物特征发生了变化。本研究采用伊利石/（直闪石+绿泥石+高岭石）和高岭石/伊利石比率来讨论这两个省份的沉积物运移路径。喜马拉雅物质广泛分布于整个研究区域，主要受潮汐、羽流和季风的影响从河口向西南地区迁移；马哈纳迪河的沉积物受西南季风的影响从西南向东北迁移，从而影响了第二省的沉积物组成。
{"title":"Clay mineral composition and transport pattern of surface sediments in the Ganges Submarine Delta","authors":"Bingjie Sun , Shengfa Liu , Ashraf Ali Seddique , Kaikai Wu , Wenjing Qi , Hui Zhang , Peng Cao , Jianguo Liu , Xuefa Shi","doi":"10.1016/j.csr.2024.105333","DOIUrl":"10.1016/j.csr.2024.105333","url":null,"abstract":"<div><div>The Ganges Submarine Delta is a key land-sea transitional area in the northeastern Indian Ocean. An understanding of sediment distribution, provenance, and transportation in this area is of great importance for understanding its sedimentary environment and the sediment “source-sink” system of the northeastern Indian Ocean. This study aimed to identify the provenances and transport patterns of fine-grained sediments in the Ganges Submarine Delta through analysis of the grain size and clay mineral content of 84 surface sediment samples. Sediment illite, chlorite, kaolinite, and smectite contents were ∼66%, 18%, 11%, and 5%, respectively. Sediment illite content decreased from north to south; smectite and chlorite decreased and increased from northwest to southeast, respectively; kaolinite content was highest in the south. Spatial cluster analysis of the four clay minerals grouped the study area into two provinces: province I in the north is characterized by a clay mineral assemblage similar to that of the Ganges-Brahmaputra rivers; province II in the south is characterized by deep water and changes to clay mineral characteristics due to the mixing of material originating from the Indian Peninsula. This study used the illite/(smectite + chlorite + kaolinite) and kaolinite/illite ratios to discuss sediment transport paths in the two provinces. Himalayan material is widely distributed throughout the study area, and mainly transported from the estuary to the southwestern area by the tides, plume, and monsoons; sediments of the Mahanadi river are transported from southwest to northeast by the southwest monsoon, thereby affecting the sediment composition of province II.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105333"},"PeriodicalIF":2.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312655","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 : 2024-09-15DOI: 10.1016/j.csr.2024.105331
Herbert L. Windom, William B. Savidge
Trace metal concentrations in otoliths of spotted moray eels (Gymnothorax moringa), non-migratory residents of hard bottom reefs at depths of ∼30–70m along the outer shelf adjacent to South Carolina and Georgia, were analyzed to determine if results provide insights into trace metal sources and transport processes in this dynamic region of the shelf. Li and Mg appear to reflect exposure to local sea water circulated through adjacent porous rock outcrops where the eels reside. Concentrations of Mn, V, Cu, and Zn in otoliths appear to be associated with deep water upwelled along the shelf break. Based on 30 years of water temperature data from fishery surveys, Scamp Ridge, located at 32.30 N at a depth of ∼50m, has significantly lower summertime bottom temperature than elsewhere along the shelf edge, indicating locally enhanced upwelling at that location. The highest levels of Cu and Zn and the lowest of Mn and V were also found in otoliths of eels collected in the vicinity of Scamp Ridge. These results indicate that otolith chemistry in eels can reveal fine-scale structure of water mass inputs to the outer shelf of the southeastern US coast.
{"title":"Sources and transport pathways of trace metals to the outer continental shelf off South Carolina and Georgia, USA revealed from the otoliths of moray eels","authors":"Herbert L. Windom, William B. Savidge","doi":"10.1016/j.csr.2024.105331","DOIUrl":"10.1016/j.csr.2024.105331","url":null,"abstract":"<div><div>Trace metal concentrations in otoliths of spotted moray eels (Gymnothorax moringa), non-migratory residents of hard bottom reefs at depths of ∼30–70m along the outer shelf adjacent to South Carolina and Georgia, were analyzed to determine if results provide insights into trace metal sources and transport processes in this dynamic region of the shelf. Li and Mg appear to reflect exposure to local sea water circulated through adjacent porous rock outcrops where the eels reside. Concentrations of Mn, V, Cu, and Zn in otoliths appear to be associated with deep water upwelled along the shelf break. Based on 30 years of water temperature data from fishery surveys, Scamp Ridge, located at 32.3<sup>0</sup> N at a depth of ∼50m, has significantly lower summertime bottom temperature than elsewhere along the shelf edge, indicating locally enhanced upwelling at that location. The highest levels of Cu and Zn and the lowest of Mn and V were also found in otoliths of eels collected in the vicinity of Scamp Ridge. These results indicate that otolith chemistry in eels can reveal fine-scale structure of water mass inputs to the outer shelf of the southeastern US coast.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105331"},"PeriodicalIF":2.1,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528862","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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