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Browsing by Author "Gareau, Jonathan"

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  • A numerical study of submesoscale processes in the coastal circulation of Madeira
    Publication . Gareau, Jonathan; Martins, Flávio Augusto Bastos da Cruz; Janeiro, João; Caldeira, Rui
    Submesoscale processes are defined geometrically by a lower length scale than the first baroclinic radius of deformation and dynamically by a Rossby number (Ro) of O(1), thus virtually unaffected by planetary forces. They have been widely studied in various environments using in-situ measurements, remote sensing, and numerical modelling. However, due to their unpredictable nature and relatively short spatial and temporal scales, identifying submesoscale patterns is a difficult task. Therefore, abundant ongoing research is continuously seeking new insight on their irregular behavior in the ocean. Recent observations of submesocale structures have shown their efficiency in transporting particles horizontally and vertically in both the open ocean and coastal waters. Oceanographic studies concerning the deep-sea island of Madeira have mainly focused on mesoscale processes but have yet to describe features found at the submesoscale. Based on the recent discovery of a coastal current over Madeira’s insular shelf, this study attempts to assess the role of submesoscale processes on the island’s coastal circulation and the main physical forcings responsible for their generation. A coupled ocean-atmosphere model (COAWST) was used to simulate oceanic outputs within 1-km resolution grids, from which Eulerian properties of the flow field were calculated to detect submesoscale activity in the area. In addition, 4 simulations were run according to different forcing scenarios: (A) all forcings (wind, tides, geostrophic); (B) wind forcing; (C) tidal forcing; (D) geostrophic far-field forcing. Results show that submesoscale activity was generally concentrated near the coast and mostly attributed to wind and geostrophic forcings. Eddies with Ro larger than 1 were found in Madeira’s wake and/or on the fringes of mesoscale eddies interacting with the island’s shallow bathymetry, which is in line with the literature. These small-scale eddies were the dominant feature within the coastal circulation, suggesting their important contribution to the material transport along the shelf.
    2022-12-12Master thesis Open access Show more