Continental Shelf Research最新文献

{"title":"Satellite-based evidence of upwelling separation off NW Iberia","authors":"Pedro R. Nunes ,&nbsp;Vanda Brotas ,&nbsp;Rita Nolasco ,&nbsp;Jesus Dubert ,&nbsp;Paulo B. Oliveira","doi":"10.1016/j.csr.2024.105356","DOIUrl":"10.1016/j.csr.2024.105356","url":null,"abstract":"<div><div>A high-resolution image sequence of sea surface temperature (SST) and Chlorophyll-a (Chl-<em>a</em>), together with numerical model solutions, is used to study the spatio-temporal variability of the two variables under intermittent upwelling-favourable winds. It is shown that the evolution of the cross-shore SST and Chl-<em>a</em> profiles over the shelf is linked to the intensity, duration and temporal separation between the wind events. The model's realistic representation of the cross-shore SST supports the interpretation that the observed variability is governed, in the inner-shelf, by the offshore separation of upwelling divergence and, over the mid-shelf, by offshore Ekman transport and mesoscale circulation. The observation of an alongshore low SST/low Chl-<em>a</em> band, bounded by the 30 m and 50 m isobaths, for the days of maximum wind stress, matching the model's solution for the outcrop of colder subsurface waters, constitute a satellite-based evidence of upwelling separation from the coast. The results are in close agreement with previous works on upwelling in shallow waters, straight coastline and gentle slope, but were not yet reported in the study area off NW Portugal. This evidence prompts for the need to use high-resolution (&lt;1 km) numerical models/imagery to properly assess the inner-shelf circulation in the region, and the effects on the marine ecosystem, namely the offshore transport of marine organisms or pollutants.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"284 ","pages":"Article 105356"},"PeriodicalIF":2.1,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142724144","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":"Assessing the conservation status of Mediterranean coastal ponds: Checklist, ecological and functional diversity of diatom communities","authors":"Davide Taurozzi ,&nbsp;Massimiliano Scalici","doi":"10.1016/j.csr.2024.105359","DOIUrl":"10.1016/j.csr.2024.105359","url":null,"abstract":"<div><div>Coastal ponds are peculiar and threatened habitats, considered biodiversity hotspots. In many ecosystems ponds can be a valuable resource for the conservation of freshwater biodiversity. The Castelporziano Presidential Estate is a Mediterranean protected area hosting numerous ponds which are suffering severe droughts and a general decline in number and hydroperiod length. Hydroperiod changes can be particularly relevant for biodiversity inhabiting ponds, in particular diatom communities. Here, for the first time, we evaluate the conservation status of Mediterranean ponds inside the Castelporziano Reserve. The aims of this research are to i) investigate the influence of environmental variables on diatom communities of ponds; (ii) analyse diatom community structure in function of species richness and competitive interactions; (iii) highlight the potential and effectiveness of diatom ecological guilds in supporting the interpretation of the ecological status of threatened small waterbodies. Overall, 122 diatom taxa in the 29 ponds were described. <em>Nitzschia</em> (18 species) was the most species-rich genus, followed by <em>Gomphonema</em> (14) and <em>Navicula</em> (13). 17 species were included in the Red List of endangered species. Intra-pond distance and anthropogenic impacts didn't influence diatom assemblages. On the contrary, diatom communities were influenced by altitude and the distance from the sea. Furthermore, temporary ponds showed the lowest values for Shannon, evenness and Simpson indexes Considering Beta-diversity, both Bray-Curtis and Jaccard dissimilarity matrices highlighted a large dissimilarity between sampling sites. Inter-variability between sites and intra-variability within the sites resulted both very low. Our results highlight that diatom species are not influenced by hydroperiod length. Moreover, a structured diatom community emerged, where segregation processes predominating over aggregation ones. Finally, the average water quality of the ponds, calculated using the EPI-D index, was described as “good”. This study represents the most complete checklist of diatom communities inside coastal ponds of Castelporziano, providing valuable insights into the effects of natural and anthropogenic influences on ponds conservation and management activities. However, spatial-temporal changes and anthropogenic impacts should be deeply investigated.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"283 ","pages":"Article 105359"},"PeriodicalIF":2.1,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664177","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":"A century of tidal evolution around the Panama Canal","authors":"Haidong Pan ,&nbsp;Min Gan ,&nbsp;Tengfei Xu ,&nbsp;Zexun Wei","doi":"10.1016/j.csr.2024.105357","DOIUrl":"10.1016/j.csr.2024.105357","url":null,"abstract":"<div><div>As one of the most vital passageways worldwide, the Panama Canal plays essential roles in global trade and maritime logistics. Sea levels around the Panama Canal are dominated by ocean tides but local tidal evolution is still unexplored to date, which motivates present study. Two secular tide gauges longer than 110 years (Cristobal and Balboa) around the Panama Canal are analyzed to explore multi-time scale tidal variability. It is found that observed nodal modulations of major constituents are generally consistent with the equilibrium tidal theory. M₄ and Mf nodal modulations notably deviate from the theory possibly due to non-linear processes. Long-term trends exist in main semi-diurnal tides, while main diurnal tides do not have significant secular trends. It is worth mentioning that M₄ and MS₄ amplitudes at Cristobal have halved in the past century. Moreover, tidal parameters of major constituents at Cristobal and Balboa show abnormal mutations in 1908, 1990–1998, and 2013–2018. As a result of changing tides, tidal asymmetries at Cristobal are significantly weakened while the number of high tides per year is notably decreased. Tides at Balboa are almost symmetric. Tidal regimes at Cristobal can periodically shift between mixed diurnal tides and mixed semi-diurnal tides following the 18.61-year nodal cycle. However, such regime shift has disappeared since 1997 due to secular negative trends in M₂ amplitudes. In general, the findings of this study can be helpful for ships navigating in the Panama Canal.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"283 ","pages":"Article 105357"},"PeriodicalIF":2.1,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664260","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":"Flow characterization and turbulence in the eastern section of the Strait of Magellan, Southern Chile","authors":"Leandro Suarez ,&nbsp;Maricarmen Guerra ,&nbsp;Megan E. Williams ,&nbsp;Cristián Escauriaza ,&nbsp;Iossif Lozovatsky ,&nbsp;Ronald Coppersmith ,&nbsp;Harindra Joseph S. Fernando","doi":"10.1016/j.csr.2024.105344","DOIUrl":"10.1016/j.csr.2024.105344","url":null,"abstract":"<div><div>The Strait of Magellan connects the Pacific and Atlantic oceans in South America’s southern region, and it has been recognized for centuries as an important transoceanic navigation route as well as a unique marine environment with a rich ecological diversity. Evaluations of the impact of human activities in the channel and multiple potential future developments require a better understanding of the physical environment to design sustainable strategies aimed at preserving these characteristics. In this investigation, we study the flow near the Atlantic inlet of the Strait where the dynamics is characterized by the interactions of the tide propagation within two narrows, which are the predominant features of the channel morphology. Tides amplified by the Patagonian shelf generate strong currents through these narrows and control the exchange between the Atlantic and central regions of the Strait. We employ bottom-mounted and vessel-mounted Acoustic Doppler Current Profilers (ADCPs) with tide gauges to analyze the mean flow, tidal propagation, and turbulence, complementing the data with previous available measurements. The analysis reveals residual flows directed toward ebb flow at the channel center and flood near the edges, showing a significant spring-neap variation. Turbulence statistics in the second narrows exhibit a significant variability between ebb and flood, with a balance between production and dissipation observed only during ebb phases.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"283 ","pages":"Article 105344"},"PeriodicalIF":2.1,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664259","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":"Machine learning reveals biological activities as the dominant factor in controlling deoxygenation in the South Yellow Sea","authors":"Qingyi Liu ,&nbsp;Chunli Liu ,&nbsp;Qicheng Meng ,&nbsp;Bei Su ,&nbsp;Haijun Ye ,&nbsp;Bingzhang Chen ,&nbsp;Wei Li ,&nbsp;Xinyu Cao ,&nbsp;Wenlong Nie ,&nbsp;Nina Ma","doi":"10.1016/j.csr.2024.105348","DOIUrl":"10.1016/j.csr.2024.105348","url":null,"abstract":"<div><div>Dissolved oxygen (DO) is a crucial element for both biotic and abiotic processes in marine ecosystems, but has declined globally in recent decades. Therefore, there is an urgent need for solid large-scale and continuous estimation of DO concentration in vital ecosystems, such as coastal areas. A random forest (RF) model for DO in South Yellow Sea (SYS) was developed by integrating satellite data and simulation data during 2011–2019. The root mean squared error (RMSE) for the training and test sets were 0.514 mg/L and 0.732 mg/L, respectively. Spatiotemporal distributions of DO of multiple layers in the study area during 2011–2019 were very well reproduced by the RF model and showed a slight decline trend in most SYS areas, while more intense decline occurred in the deep central SYS. The analysis of the mechanisms of DO decline in the South Yellow Sea cold water mass (SYSCWM), located in the deep central SYS, indicates that the deoxygenation here is largely due to biological activities. This finding may have implications for studies on drivers of deoxygenation in coastal areas. Furthermore, integrating satellite data with machine learning models can offer a powerful approach to capturing the continuous spatiotemporal characteristics of ocean parameters over large spatial scales.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"283 ","pages":"Article 105348"},"PeriodicalIF":2.1,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664258","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":"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}