Continental Shelf Research最新文献

{"title":"Observations and generation of internal waves in the Strait of Sicily","authors":"Francesco Bignami ,&nbsp;Werner Alpers ,&nbsp;Davide Cavaliere ,&nbsp;Giovanni La Forgia ,&nbsp;Gianmaria Sannino","doi":"10.1016/j.csr.2024.105349","DOIUrl":"10.1016/j.csr.2024.105349","url":null,"abstract":"<div><div>Oceanic internal solitary waves (ISWs) can be generated by several mechanisms, among which by tidal flow over shallow bathymetry, atmospheric forcing, unbalanced sub-mesoscale flow without external forcing and rapid displacements of the sharp fronts separating e.g. cold ocean water masses or river plumes from the ambient seawater. In this paper, we analyze synthetic aperture radar (SAR) images acquired by the Sentinel-1 satellites over the Adventure Bank area, located on the western side of the Strait of Sicily in the years 2018–2021 showing numerous radar signatures of ISWs. This is the first time that massive presence of ISWs is reported in this area of the Mediterranean Sea. The internal wave field, observed primarily in the months from May to September, is very heterogeneous, with wavelengths ranging from a few hundred meters to a few kilometers, wave front lengths from a few km to about 40 km, and propagating in almost any direction. This suggests that the internal waves detected in the SAR images are generated by a variety of mechanisms and not by a specific one. Although in general tidal currents are weak in the Mediterranean Sea, the sum of the tidal flow and the Atlantic-Ionian Stream current can attain values up to 0.3 m s⁻¹ such that ISW generation by interaction with shallow underwater bottom topography becomes possible. Furthermore, cold filaments and sub-mesoscale cyclonic eddies generated by upwelling at the south coast of Sicily, feature sharp and rapidly moving fronts, from which ISWs may originate. Theoretical evidence for these two types of ISW generation mechanisms is provided by model results obtained from the 1/48° resolution ENEA model and the 100 m resolution Delft3D model.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"284 ","pages":"Article 105349"},"PeriodicalIF":2.1,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142724143","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}

{"title":"Echoes of a Cold War","authors":"Valeriy Y. Rusakov ,&nbsp;Ruslan A. Lukmanov ,&nbsp;Bulat R. Soktoev ,&nbsp;Andrey Y. Mishan'kin","doi":"10.1016/j.csr.2024.105347","DOIUrl":"10.1016/j.csr.2024.105347","url":null,"abstract":"<div><div>The Kara Sea was an area of radionuclide contamination as a result of nuclear weapons testing, since it is located in close proximity to the nuclear test site on the Novaya Zemlya archipelago. The vertical distribution of ¹³⁷Cs and ²¹⁰Pb in 15 sediment cores from the sea made it possible to reconstruct the chronology of ¹³⁷Cs entry into marine sediments. The reconstruction was based on the age-depth model RUS2023 (Rusakov et al., 2024) for ²¹⁰Pb_ex, taking into account the grain-size composition and sorption capacity of sediments. Our study showed that higher ¹³⁷Cs concentrations in sediments of the Novaya Zemlya Trough correspond to the time of active nuclear weapons testing in 1961–63 (about 9.0 ± 1.6 Bq kg^‒1), as well as in estuarine sediments of the Yenisei Bay in 1986 (85.2 ± 3.2 Bq kg^‒1). The abnormally high flux in 1980s represents the superposition of ¹³⁷Cs fluxes as a result of global fallout (Chernobyl trace) and as a result of the release of radionuclide from regional source located in the Yenisei River catchment. Both of these events are associated with increased the sedimentation and mass accumulation rates of marine sediments. In 1961‒63, this was a consequence of the release of sediment into the atmosphere due to nuclear explosions, and in the 1980s, as a result of an increase in sediment supply with river runoff. Currently, against the backdrop of a decrease in sediment fluxes into the sea, Novaya Zemlya and Yenisei River remain the main sources of ¹³⁷Cs supply to marine sediments. Background values for recent sediments in the Kara Sea are &lt;2.0 Bq kg^‒1.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"283 ","pages":"Article 105347"},"PeriodicalIF":2.1,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664257","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}

{"title":"Determining the cross-shelf and vertical scales of coastal upwelling","authors":"K.H. Brink","doi":"10.1016/j.csr.2024.105346","DOIUrl":"10.1016/j.csr.2024.105346","url":null,"abstract":"<div><div>Idealized primitive equation numerical model experiments are used to investigate the source waters (as defined by a passive tracer of initial depth) for coastal upwelling over a uniformly sloping bottom and allowing for alongshore variability in the wind stress. Under steady conditions, the volume of upwelled water is essentially balanced by alongshore transport from the direction (“downwave”) toward which long coastal-trapped waves propagate. For weak stratification (<em>s = αN/f ≪</em> 0.1 where <em>α</em> is the bottom slope, <em>N</em> the initial buoyancy frequency and <em>f</em> the Coriolis parameter) this alongshore transport involves a balance of bottom Ekman pumping and topographic vortex stretching: the “arrested topographic wave”. For larger <em>s</em>, some of this alongshore transport occurs in a frontal jet. When time dependence is included, a third offshore scale, determined by frontal motion balancing local Ekman transport, enters initially, while the frontal equilibrium scale dominates after longer times. The offshore scale translates readily into a maximum depth from which upwelled waters can reach the surface. Scalings are provided for the source water depth in both the steady and unsteady cases. Broadly speaking, the source depth is greater when alongshore winds or bottom slope are stronger, or when the alongshore extent of wind forcing is greater. Some variants, including the effects of a more realistic shelf-slope topography, are also examined.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"284 ","pages":"Article 105346"},"PeriodicalIF":2.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142724142","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}

{"title":"Storms can increase beach resilience on a low-energy coast in the proximity of a harbor","authors":"Gabriela Medellín ,&nbsp;Gemma L. Franklin ,&nbsp;Alec Torres-Freyermuth","doi":"10.1016/j.csr.2024.105343","DOIUrl":"10.1016/j.csr.2024.105343","url":null,"abstract":"<div><div>Storms drive energetic waves and induce high water levels on the nearshore. Hence, they are commonly associated with negative effects on the coast (i.e., beach erosion and coastal flooding). Beach resilience, the capability to resist and recover from storms, relies on the beach width and elevation. This study investigates the subaerial beach morphological response to storms on a micro-tidal, low-energy tropical beach located in the proximity of a harbor. The study area, situated on a barrier island on the northwestern coast of the Yucatan Peninsula, is prone to winter, tropical, and local storms. Beach surveys were carried out over the 2015–2023 period, with a high spatial and temporal resolution, along a 4-km stretch of coast, comprising beach transects located downstream (erosive beach) and upstream (accretive and stable beach) of the harbor jetties. Moreover, offshore wave conditions and water levels were measured to identify storm events. Pre- and post-storm beach surveys are employed to estimate beach geoindicators to assess the impact of 66 storms. Consistent with prior studies, field observations suggest that the beach response (accretive or erosive) is dependent on the water level and pre-storm beach morphology. Furthermore, a net subaerial sediment volume gain, correlated with seasonal changes on the dimensionless fall velocity parameter and water level, occurs during the winter storm season on the prograding/stable beach section. On the other hand, storms induced subaerial sand volume losses on the receding beach section exposed to the same forcing conditions. Thus, our observations suggest that moderate winter and tropical storms can contribute to increasing beach resilience in this region.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105343"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578654","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}

{"title":"The Dnipro-Buh plume: A tale of high-volume freshwater discharge in a non-tidal sea","authors":"Alexander E. Yankovsky ,&nbsp;Yuriy P. Ilyin","doi":"10.1016/j.csr.2024.105345","DOIUrl":"10.1016/j.csr.2024.105345","url":null,"abstract":"<div><div>The Dnipro River has the second-largest annually-averaged discharge among European rivers and together with the Pivdennyi Buh River runs off on the Black Sea northwestern shelf, forming the Dnipro-Buh coastal buoyant plume. This study presents shipboard observations of the Dnipro-Buh plume in May of 1992 and 1994, when the freshwater discharge was lower and higher, respectively, than its climatological value for May, while the wind forcing was light and variable. In-situ data are complemented with satellite images obtained under similar forcing conditions at later times. Weak mixing in the Dnipro-Buh estuary leads to the formation of a thin, 1.5–3 m deep surface-advected plume. The estuarine outflow runs off parallel with the coastline, but with downstream distance it rapidly expands offshore over multiple baroclinic Rossby radii. On synoptic to monthly time scales, the Dnipro-Buh plume spreads in bimodal fashion, both upstream and downstream from the estuarine mouth. The downstream geostrophic transport of freshwater in the plume is a small fraction of the freshwater discharge feeding the plume. Also, as salinity anomaly decreases offshore, the freshwater content remains near-constant or even increases. This implies that the freshwater spreading is sustained by cross-frontal “diffusion” to a greater extent than through the advection by geostrophic circulation associated with the plume. Meso- and submesoscale instabilities are likely to play a major role in mixing and offshore spreading of the Dnipro-Buh plume.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105345"},"PeriodicalIF":2.1,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537505","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}

{"title":"Sedimentation characteristics of surficial sediments in Baiyun Canyon area, Northern South China Sea","authors":"Qingjie Zhou ,&nbsp;Youkou Dong ,&nbsp;Lejun Liu ,&nbsp;Xishuang Li","doi":"10.1016/j.csr.2024.105342","DOIUrl":"10.1016/j.csr.2024.105342","url":null,"abstract":"<div><div>The Baiyun Canyon area on the Northern Slope of the South China Sea is a potential hotspot for oil and gas resource development, but the sediment characteristics and sedimentary environment in this region present challenges for offshore engineering. This study comprehensively analyzed the physical, and mechanical properties of sediments in the area using geophysical exploration, engineering geological investigation, fixed-point sampling and hydrological observation. The engineering geological characteristics and sedimentary environment of surface sediments in the Baiyun Canyon area were studied, and the relationship between physical and mechanical properties and sedimentary environment was explored. The study revealed that the sediments in this area consist mainly of organic soft clay with high water content, low density, high pore ratio, high liquid limit, high plasticity and low strength. The physical and mechanical properties of the sediments vary, with the mechanical properties exhibiting higher variability than the physical properties. The research findings offer a scientific basis for understanding the seabed soil properties for designing submarine engineering structures in the deep waters of the northern South China Sea. This study holds significant theoretical and practical implications for oil and gas exploration and offshore engineering construction.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"282 ","pages":"Article 105342"},"PeriodicalIF":2.1,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528861","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}

{"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}

{"title":"Phosphorus fractions and their vertical distribution in seabed sediments of the eastern Baltic Sea","authors":"Markus Ausmeel ,&nbsp;Martin Liira ,&nbsp;Päärn Paiste ,&nbsp;Aivo Lepland ,&nbsp;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}

{"title":"Investigation of submarine groundwater discharge into the Baltic Sea through varved glacial clays","authors":"Nai-Chen Chen ,&nbsp;Matt O'Regan ,&nbsp;Wei-Li Hong ,&nbsp;Thomas Andrén ,&nbsp;Valentí Rodellas ,&nbsp;Florian Roth ,&nbsp;Carl-Magnus Mörth ,&nbsp;Carl Regnéll ,&nbsp;Hanna Sofia Marxen ,&nbsp;Sophie ten Hietbrink ,&nbsp;Tzu-Hao Huang ,&nbsp;Richard Gyllencreautz ,&nbsp;Christian Stranne ,&nbsp;Anna Linderholm ,&nbsp;Jordi Garcia-Orellana ,&nbsp;Christoph Humborg ,&nbsp;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 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.</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}

{"title":"Declining bivalve species and functional diversity along a coastal eutrophication-deoxygenation gradient in the northern Gulf of Mexico","authors":"Paul G. Harnik ,&nbsp;Anne Chao ,&nbsp;Katie S. Collins ,&nbsp;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}