Physical-biological interactions in coastal and oceanic fronts off Southeastern Brazil

• Grant number: 17/15026-6
• Support type: Scholarships in Brazil - Doctorate (Direct)
• Effective date (Start): January 01, 2018
• Status: Discontinued
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Physical Oceanography
• Principal researcher: Ilson Carlos Almeida da SIlveira
• Grantee: Filipe Pereira dos Santos
• Home Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 14/50820-7 - Marine ferromanganese deposits: a major resource of E-tech elements, AP.TEM
• Associated scholarship(s): 21/08572-0 - Dynamics of the Cape Frio upwelling front, BE.EP.DD

Abstract

One of the components which represent an intermittent mechanism of high biological productivity are the cyclonic eddies shed off Cape Frio (CF) by the Brazil Current (BC). They detach from BC and propagate southward, reaching and, certainly, impacting the Rio Grande Rise region. The region off CF is characterized by the occurrence of coastal upwelling during most of the year. The temperature of the upwelled waters is around 10°C lower than the ones of the intermediate and external shelves, occupied by the BC in the surface layers. Regions with intense horizontal gradients (fronts), such as CF, have high primary productivity and biomass. Such places are also characterized by a-geostrophic features (Rossby number is O(1)) with a length of 1 to 10 km, that is, submesoscale features. These features may modulate the exchanges between the continental shelf and the open ocean since they act like conduits of offshore transport of recently upwelled waters. Submesoscale features are also non-hydrostatic and therefore have vertical velocities of the order of the horizontal ones. That way, they may play an important role in the upper ocean ecology. The formation of such features has been associated with the meandering activity of adjacent boundary currents. In this way, CF is ideal for the study of the formation and dynamics of submesoscales features, since, within a small geographic area, interactions between the upwelling front and the BC occur. The effects of the submesoscale and the ascending mesoscale velocities in the sedimentation rates were not yet investigated. Forasmuch as the sedimentary deposition rates are essential for the formation of polymetallic nodules and crusts, the comprehension of the biological processes which affect the export of particulate organic material to the deep ocean is essential for the investigation of the formation mechanisms of polymetallic nodules and crusts, study object of the Marine E-tech thematic project, approved by the NERC-FAPESP edict in 2015. Therefore, the main objective of this project is to study how the submesoscale dynamics affect the distribution patterns of planktonic organisms in the CF upwelling front and consequently the export of particulate organic material. (AU)