{"title":"On the retroflection of upwelling jets near coastal bends","authors":"Jochen Kämpf","doi":"10.1016/j.csr.2024.105276","DOIUrl":null,"url":null,"abstract":"<div><p>Bays in coastal upwelling regions often serve as larvae retention zones underpinning functioning of marine ecosystems. Using a three-dimensional hydrodynamic model, this process-oriented study explores the ocean dynamics that follow from the relaxation of a spatially-uniform, upwelling-favourable wind field behind a headland. Findings reveal that wind relaxation leads to the appearance of a swift coastal countercurrent (CCC) as the inshore retroflection of the coastal upwelling jet. The analysis reveals that the CCC starts to form along the downwind coast of the headland where the upwelling-induced onshore barotropic pressure gradient opposes the wind stress. Here, wind relaxation indirectly induces a flow convergence that reverses the barotropic pressure gradient within ∼5 km from the coast which geostrophically drives the CCC. Once generated, this inshore barotropic pressure anomaly propagates along the coast as a coastal Kelvin wave to form an inshore retroflection of the upwelling jet. On the other hand, the upwelling creates a plume of denser water on the shelf behind the headland. After wind relaxation, the rotational-gravitational adjustment of this dense-water plume marks the front of the retroflection zone as a cyclonic baroclinic feature with a diameter of the baroclinic deformation radius (∼10 km). Findings show that this rotational-gravitational adjustment intensifies the pressure-gradient forcing of the CCC. Overall, the findings demonstrate that the retroflecting coastal current can traps both upwelled water and particles in vicinity of the headland, which is clearly of relevance to marine productivity.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"279 ","pages":"Article 105276"},"PeriodicalIF":2.1000,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0278434324001067/pdfft?md5=0eca1a7e288e3d751a5a07e8bc1c05a3&pid=1-s2.0-S0278434324001067-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Continental Shelf Research","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0278434324001067","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"OCEANOGRAPHY","Score":null,"Total":0}
引用次数: 0
Abstract
Bays in coastal upwelling regions often serve as larvae retention zones underpinning functioning of marine ecosystems. Using a three-dimensional hydrodynamic model, this process-oriented study explores the ocean dynamics that follow from the relaxation of a spatially-uniform, upwelling-favourable wind field behind a headland. Findings reveal that wind relaxation leads to the appearance of a swift coastal countercurrent (CCC) as the inshore retroflection of the coastal upwelling jet. The analysis reveals that the CCC starts to form along the downwind coast of the headland where the upwelling-induced onshore barotropic pressure gradient opposes the wind stress. Here, wind relaxation indirectly induces a flow convergence that reverses the barotropic pressure gradient within ∼5 km from the coast which geostrophically drives the CCC. Once generated, this inshore barotropic pressure anomaly propagates along the coast as a coastal Kelvin wave to form an inshore retroflection of the upwelling jet. On the other hand, the upwelling creates a plume of denser water on the shelf behind the headland. After wind relaxation, the rotational-gravitational adjustment of this dense-water plume marks the front of the retroflection zone as a cyclonic baroclinic feature with a diameter of the baroclinic deformation radius (∼10 km). Findings show that this rotational-gravitational adjustment intensifies the pressure-gradient forcing of the CCC. Overall, the findings demonstrate that the retroflecting coastal current can traps both upwelled water and particles in vicinity of the headland, which is clearly of relevance to marine productivity.
期刊介绍:
Continental Shelf Research publishes articles dealing with the biological, chemical, geological and physical oceanography of the shallow marine environment, from coastal and estuarine waters out to the shelf break. The continental shelf is a critical environment within the land-ocean continuum, and many processes, functions and problems in the continental shelf are driven by terrestrial inputs transported through the rivers and estuaries to the coastal and continental shelf areas. Manuscripts that deal with these topics must make a clear link to the continental shelf. Examples of research areas include:
Physical sedimentology and geomorphology
Geochemistry of the coastal ocean (inorganic and organic)
Marine environment and anthropogenic effects
Interaction of physical dynamics with natural and manmade shoreline features
Benthic, phytoplankton and zooplankton ecology
Coastal water and sediment quality, and ecosystem health
Benthic-pelagic coupling (physical and biogeochemical)
Interactions between physical dynamics (waves, currents, mixing, etc.) and biogeochemical cycles
Estuarine, coastal and shelf sea modelling and process studies.