{"id":{"repo_id":"cadiz","oai_identifier":"oai:rodin.uca.es:10498/39781"},"canonical_url":"https://search.dev.ndltd.org/etd/cadiz/oai:rodin.uca.es:10498/39781","repository":{"repo_id":"cadiz","name":"Universidad de Cadiz","base_url":"https://rodin.uca.es/oai/request"},"display":{"title":"Internal wave generation and its impact at the island Shelf","abstract":"This doctoral dissertation provides an integrated analysis of island-shelf circulation and the generation of nonlinear internal waves (NIWs) in the Madeira Archipelago, a region characterized by steep bathymetry, a narrow insular shelf, and strong atmosphere–ocean interactions. Although Madeira has been widely studied in terms of wake dynamics, mesoscale variability, and wind–island interactions, no systematic assessment of internal wave generation had been conducted in this area of the northeastern Atlantic. This thesis addresses this major gap by combining in-situ observations, satellite imagery, and high-resolution numerical modeling. The first component examines island-shelf circulation under different forcing regimes, including tides, local winds, and large-scale background flow. A high-resolution (1 km) COAWST configuration is used together with ADCP measurements, meteorological stations, Sentinel imagery, and surface drifters. Results show that Madeira’s coastal circulation is governed by the superposition of these forcings, producing alternating patterns of retention, recirculation, and coastal transport. The spatial heterogeneity of these patterns is strongly controlled by the steep and irregular island topography. The second component presents the first direct observational evidence of NIW generation along the ridge connecting Madeira and the Desertas Islands. Using long-term mooring data, a Wirewalker profiler, a thermistor chain, and hydrographic observations, the analysis documents isopycnal displacements, internal bores, and phase-dependent variations of the Froude number associated with the barotropic tidal cycle. Both Sentinel-1 SAR and Sentinel-2 optical imagery reveal surface signatures consistent with internal wave fronts aligned with the ridge. Based on these observations, a new conceptual model is proposed linking tidal-phase transitions, subcritical–supercritical flow regimes, and the periodic release of nonlinear internal waves. The third component evaluates the ability of a hydrostatic numerical framework (ROMS/COAWST) to reproduce these processes. Three vertical mixing schemes—GLS, MY25, and LMD—are tested. The MY25 configuration shows the highest skill in reproducing observed density structure, isopycnal displacement, Richardson-number variability, and the timing of NIW generation and propagation. Using this optimal configuration, the analysis is extended along the entire Madeira–Desertas Ridge, revealing pronounced spatial heterogeneity in the intensity, location, and extent of NIW activity. Overall, this dissertation establishes a comprehensive dynamical framework for understanding stratified flow–topography interactions in Madeira. It provides the first observational characterization of NIWs in the region, demonstrates their tidal-phase dependence, and identifies the physical mechanisms underpinning their release. It further shows that, when properly configured, high-resolution hydrostatic models can be effective tools for investigating nonlinear internal waves in steep and complex insular environments. The findings offer new insights applicable to other deep-ocean island systems and contribute to improving the representation of internal wave processes in coastal and regional ocean models.","abstract_html":"This doctoral dissertation provides an integrated analysis of island-shelf circulation and the generation of nonlinear internal waves (NIWs) in the Madeira Archipelago, a region characterized by steep bathymetry, a narrow insular shelf, and strong atmosphere–ocean interactions. Although Madeira has been widely studied in terms of wake dynamics, mesoscale variability, and wind–island interactions, no systematic assessment of internal wave generation had been conducted in this area of the northeastern Atlantic. This thesis addresses this major gap by combining in-situ observations, satellite imagery, and high-resolution numerical modeling. The first component examines island-shelf circulation under different forcing regimes, including tides, local winds, and large-scale background flow. A high-resolution (1 km) COAWST configuration is used together with ADCP measurements, meteorological stations, Sentinel imagery, and surface drifters. Results show that Madeira’s coastal circulation is governed by the superposition of these forcings, producing alternating patterns of retention, recirculation, and coastal transport. The spatial heterogeneity of these patterns is strongly controlled by the steep and irregular island topography. The second component presents the first direct observational evidence of NIW generation along the ridge connecting Madeira and the Desertas Islands. Using long-term mooring data, a Wirewalker profiler, a thermistor chain, and hydrographic observations, the analysis documents isopycnal displacements, internal bores, and phase-dependent variations of the Froude number associated with the barotropic tidal cycle. Both Sentinel-1 SAR and Sentinel-2 optical imagery reveal surface signatures consistent with internal wave fronts aligned with the ridge. Based on these observations, a new conceptual model is proposed linking tidal-phase transitions, subcritical–supercritical flow regimes, and the periodic release of nonlinear internal waves. The third component evaluates the ability of a hydrostatic numerical framework (ROMS/COAWST) to reproduce these processes. Three vertical mixing schemes—GLS, MY25, and LMD—are tested. The MY25 configuration shows the highest skill in reproducing observed density structure, isopycnal displacement, Richardson-number variability, and the timing of NIW generation and propagation. Using this optimal configuration, the analysis is extended along the entire Madeira–Desertas Ridge, revealing pronounced spatial heterogeneity in the intensity, location, and extent of NIW activity. Overall, this dissertation establishes a comprehensive dynamical framework for understanding stratified flow–topography interactions in Madeira. It provides the first observational characterization of NIWs in the region, demonstrates their tidal-phase dependence, and identifies the physical mechanisms underpinning their release. It further shows that, when properly configured, high-resolution hydrostatic models can be effective tools for investigating nonlinear internal waves in steep and complex insular environments. The findings offer new insights applicable to other deep-ocean island systems and contribute to improving the representation of internal wave processes in coastal and regional ocean models.","abstract_has_math":false,"creators":["Da Costa Dos Reis, Jesús Leonel"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Bruno Mejías, Miguel","Andrade Caldeira, Rui Miguel"],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026","date_published":"2026","updated_at":"2026-07-24T01:29:34Z","subjects":["circulación insular","ondas internas no lineales","COAWST","Madeira–Desertas Ridge","estratificación","mezcla vertical","nonlinear internal waves","island-shelf circulation","stratification","vertical mixing"],"languages":["eng"],"rights":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"],"rights_urls":["http://creativecommons.org/licenses/by-nc-nd/4.0/"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10498/39781","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Bruno Mejías, Miguel","Andrade Caldeira, Rui Miguel"]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Física Aplicada"]},{"key":"dc:creator","label":"Author","values":["Da Costa Dos Reis, Jesús Leonel"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-06-17T09:06:03Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-06-17T09:06:03Z"]},{"key":"dc:date.issued","label":"Date","values":["2026"]},{"key":"dc:type","label":"Dc Type","values":["doctoral thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["circulación insular","ondas internas no lineales","COAWST","Madeira–Desertas Ridge","estratificación","mezcla vertical","nonlinear internal waves","island-shelf circulation","stratification","vertical mixing"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://creativecommons.org/licenses/by-nc-nd/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10498/39781"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This doctoral dissertation provides an integrated analysis of island-shelf circulation and the generation of nonlinear internal waves (NIWs) in the Madeira Archipelago, a region characterized by steep bathymetry, a narrow insular shelf, and strong atmosphere–ocean interactions. Although Madeira has been widely studied in terms of wake dynamics, mesoscale variability, and wind–island interactions, no systematic assessment of internal wave generation had been conducted in this area of the northeastern Atlantic. This thesis addresses this major gap by combining in-situ observations, satellite imagery, and high-resolution numerical modeling. The first component examines island-shelf circulation under different forcing regimes, including tides, local winds, and large-scale background flow. A high-resolution (1 km) COAWST configuration is used together with ADCP measurements, meteorological stations, Sentinel imagery, and surface drifters. Results show that Madeira’s coastal circulation is governed by the superposition of these forcings, producing alternating patterns of retention, recirculation, and coastal transport. The spatial heterogeneity of these patterns is strongly controlled by the steep and irregular island topography. The second component presents the first direct observational evidence of NIW generation along the ridge connecting Madeira and the Desertas Islands. Using long-term mooring data, a Wirewalker profiler, a thermistor chain, and hydrographic observations, the analysis documents isopycnal displacements, internal bores, and phase-dependent variations of the Froude number associated with the barotropic tidal cycle. Both Sentinel-1 SAR and Sentinel-2 optical imagery reveal surface signatures consistent with internal wave fronts aligned with the ridge. Based on these observations, a new conceptual model is proposed linking tidal-phase transitions, subcritical–supercritical flow regimes, and the periodic release of nonlinear internal waves. The third component evaluates the ability of a hydrostatic numerical framework (ROMS/COAWST) to reproduce these processes. Three vertical mixing schemes—GLS, MY25, and LMD—are tested. The MY25 configuration shows the highest skill in reproducing observed density structure, isopycnal displacement, Richardson-number variability, and the timing of NIW generation and propagation. Using this optimal configuration, the analysis is extended along the entire Madeira–Desertas Ridge, revealing pronounced spatial heterogeneity in the intensity, location, and extent of NIW activity. Overall, this dissertation establishes a comprehensive dynamical framework for understanding stratified flow–topography interactions in Madeira. It provides the first observational characterization of NIWs in the region, demonstrates their tidal-phase dependence, and identifies the physical mechanisms underpinning their release. It further shows that, when properly configured, high-resolution hydrostatic models can be effective tools for investigating nonlinear internal waves in steep and complex insular environments. The findings offer new insights applicable to other deep-ocean island systems and contribute to improving the representation of internal wave processes in coastal and regional ocean models.","Este trabajo doctoral ofrece un análisis integrado de la circulación insular y la generación de ondas internas no lineales (NIWs) en el archipiélago de Madeira, una región oceánica caracterizada por una plataforma estrecha, taludes pronunciados y una interacción intensa entre procesos atmosféricos y oceánicos. A pesar de la extensa literatura sobre dinámica de estelas, mesoescala y interacción viento-isla en Madeira, hasta ahora no existía una caracterización sistemática de la generación de ondas internas ni un marco conceptual que explicase sus mecanismos en esta zona del Atlántico nororiental. Esta tesis cubre dicha laguna combinando observaciones in situ, datos de satélite y modelación numérica de alta resolución. En la primera parte, se examina la circulación de la plataforma insular bajo distintos regímenes de forzamiento (mareas, vientos locales y circulación oceánica de gran escala). Para ello se emplea el sistema acoplado COAWST, con resolución horizontal de 1 km, complementado con datos de ADCP, estaciones meteorológicas, imágenes Centinela y trayectorias de derivadores. Los resultados muestran que la circulación costera de Madeira está controlada por la superposición de estos forzamientos, generando patrones alternantes de retención, recirculación y transporte costero, modulados por la abrupta batimetría insular. La segunda parte presenta la primera evidencia observacional directa de NIWs generadas en la dorsal que conecta Madeira con las Islas Desertas. A partir de un fondeo de larga duración, un Wirewalker, una cadena de termistores y datos hidrográficos, se documentan desplazamientos isopicnales, bores internos y variaciones del número de Froude asociados a fases concretas del ciclo mareal. Imágenes de radar y ´ópticas (Sentinel-1 y Sentinel-2) muestran frentes internos coherentes con la orientación de la dorsal. A partir de estas observaciones, se propone un modelo conceptual que relaciona la fase de la corriente baritrópica, la transición subcrítica-supercrítica y la liberación periódica de ondas internas no lineales. La tercera parte evalúa la capacidad de un modelo hidrostático (ROMS/COAWST) para reproducir estos procesos. Se prueban tres esquemas de mezcla vertical —GLS, MY25 y LMD— observándose que la configuración MY25 reproduce con mayor fidelidad la estructura de densidad, el desplazamiento isopicnal, la variabilidad del número de Richardson y las fases de generación y propagación de NIWs. Utilizando esta configuración, se extiende el análisis a lo largo de toda la dorsal, identificando diferencias espaciales significativas en la intensidad, localización y extensión de las ondas internas. En conjunto, esta tesis establece un marco dinámico detallado para comprender la interacción flujo-topografía en Madeira, aportando evidencia inédita sobre la generación de NIWs en la región y demostrando que, bajo configuraciones adecuadas, modelos hidrostáticos de alta resolución pueden ser herramientas robustas en el estudio de ondas internas en entornos insulares complejos."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Internal wave generation and its impact at the island Shelf"]}]}],"canonical_facts":{"dc:contributor.advisor":["Bruno Mejías, Miguel","Andrade Caldeira, Rui Miguel"],"dc:contributor.other":["Física Aplicada"],"dc:creator":["Da Costa Dos Reis, Jesús Leonel"],"dc:date.accessioned":["2026-06-17T09:06:03Z"],"dc:date.available":["2026-06-17T09:06:03Z"],"dc:date.issued":["2026"],"dc:description.abstract":["This doctoral dissertation provides an integrated analysis of island-shelf circulation and the generation of nonlinear internal waves (NIWs) in the Madeira Archipelago, a region characterized by steep bathymetry, a narrow insular shelf, and strong atmosphere–ocean interactions. Although Madeira has been widely studied in terms of wake dynamics, mesoscale variability, and wind–island interactions, no systematic assessment of internal wave generation had been conducted in this area of the northeastern Atlantic. This thesis addresses this major gap by combining in-situ observations, satellite imagery, and high-resolution numerical modeling. The first component examines island-shelf circulation under different forcing regimes, including tides, local winds, and large-scale background flow. A high-resolution (1 km) COAWST configuration is used together with ADCP measurements, meteorological stations, Sentinel imagery, and surface drifters. Results show that Madeira’s coastal circulation is governed by the superposition of these forcings, producing alternating patterns of retention, recirculation, and coastal transport. The spatial heterogeneity of these patterns is strongly controlled by the steep and irregular island topography. The second component presents the first direct observational evidence of NIW generation along the ridge connecting Madeira and the Desertas Islands. Using long-term mooring data, a Wirewalker profiler, a thermistor chain, and hydrographic observations, the analysis documents isopycnal displacements, internal bores, and phase-dependent variations of the Froude number associated with the barotropic tidal cycle. Both Sentinel-1 SAR and Sentinel-2 optical imagery reveal surface signatures consistent with internal wave fronts aligned with the ridge. Based on these observations, a new conceptual model is proposed linking tidal-phase transitions, subcritical–supercritical flow regimes, and the periodic release of nonlinear internal waves. The third component evaluates the ability of a hydrostatic numerical framework (ROMS/COAWST) to reproduce these processes. Three vertical mixing schemes—GLS, MY25, and LMD—are tested. The MY25 configuration shows the highest skill in reproducing observed density structure, isopycnal displacement, Richardson-number variability, and the timing of NIW generation and propagation. Using this optimal configuration, the analysis is extended along the entire Madeira–Desertas Ridge, revealing pronounced spatial heterogeneity in the intensity, location, and extent of NIW activity. Overall, this dissertation establishes a comprehensive dynamical framework for understanding stratified flow–topography interactions in Madeira. It provides the first observational characterization of NIWs in the region, demonstrates their tidal-phase dependence, and identifies the physical mechanisms underpinning their release. It further shows that, when properly configured, high-resolution hydrostatic models can be effective tools for investigating nonlinear internal waves in steep and complex insular environments. The findings offer new insights applicable to other deep-ocean island systems and contribute to improving the representation of internal wave processes in coastal and regional ocean models.","Este trabajo doctoral ofrece un análisis integrado de la circulación insular y la generación de ondas internas no lineales (NIWs) en el archipiélago de Madeira, una región oceánica caracterizada por una plataforma estrecha, taludes pronunciados y una interacción intensa entre procesos atmosféricos y oceánicos. A pesar de la extensa literatura sobre dinámica de estelas, mesoescala y interacción viento-isla en Madeira, hasta ahora no existía una caracterización sistemática de la generación de ondas internas ni un marco conceptual que explicase sus mecanismos en esta zona del Atlántico nororiental. Esta tesis cubre dicha laguna combinando observaciones in situ, datos de satélite y modelación numérica de alta resolución. En la primera parte, se examina la circulación de la plataforma insular bajo distintos regímenes de forzamiento (mareas, vientos locales y circulación oceánica de gran escala). Para ello se emplea el sistema acoplado COAWST, con resolución horizontal de 1 km, complementado con datos de ADCP, estaciones meteorológicas, imágenes Centinela y trayectorias de derivadores. Los resultados muestran que la circulación costera de Madeira está controlada por la superposición de estos forzamientos, generando patrones alternantes de retención, recirculación y transporte costero, modulados por la abrupta batimetría insular. La segunda parte presenta la primera evidencia observacional directa de NIWs generadas en la dorsal que conecta Madeira con las Islas Desertas. A partir de un fondeo de larga duración, un Wirewalker, una cadena de termistores y datos hidrográficos, se documentan desplazamientos isopicnales, bores internos y variaciones del número de Froude asociados a fases concretas del ciclo mareal. Imágenes de radar y ´ópticas (Sentinel-1 y Sentinel-2) muestran frentes internos coherentes con la orientación de la dorsal. A partir de estas observaciones, se propone un modelo conceptual que relaciona la fase de la corriente baritrópica, la transición subcrítica-supercrítica y la liberación periódica de ondas internas no lineales. La tercera parte evalúa la capacidad de un modelo hidrostático (ROMS/COAWST) para reproducir estos procesos. Se prueban tres esquemas de mezcla vertical —GLS, MY25 y LMD— observándose que la configuración MY25 reproduce con mayor fidelidad la estructura de densidad, el desplazamiento isopicnal, la variabilidad del número de Richardson y las fases de generación y propagación de NIWs. Utilizando esta configuración, se extiende el análisis a lo largo de toda la dorsal, identificando diferencias espaciales significativas en la intensidad, localización y extensión de las ondas internas. En conjunto, esta tesis establece un marco dinámico detallado para comprender la interacción flujo-topografía en Madeira, aportando evidencia inédita sobre la generación de NIWs en la región y demostrando que, bajo configuraciones adecuadas, modelos hidrostáticos de alta resolución pueden ser herramientas robustas en el estudio de ondas internas en entornos insulares complejos."],"dc:format":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/10498/39781"],"dc:language.iso":["eng"],"dc:rights":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"],"dc:rights.uri":["http://creativecommons.org/licenses/by-nc-nd/4.0/"],"dc:subject":["circulación insular","ondas internas no lineales","COAWST","Madeira–Desertas Ridge","estratificación","mezcla vertical","nonlinear internal waves","island-shelf circulation","stratification","vertical mixing"],"dc:title":["Internal wave generation and its impact at the island Shelf"],"dc:type":["doctoral thesis"]},"updated_at":"2026-07-24T01:29:34Z"}