Surface Circulation and Vertical Structure of Upper Ocean Variability Around Fernando de Noronha Archipelago and Rocas Atoll During Spring 2015 and Fall 2017

Using current, hydrographic and satellite observations collected off Northeast Brazil around the Fernando de Noronha Archipelago Rocas Atoll during two oceanographic cruises (spring 2015 fall 2017), we investigated general oceanic circulation its modifications induced by islands. In spring 2015, area was characterized lower SST (26.6°C) deep mixed-layer (∼90 m). At this depth, a strong current shear observed between central branch of eastward flowing near-surface South Equatorial Current westward Undercurrent. contrast, in 2017, higher (∼28.8°C) shallower (∼50 The Undercurrent weaker period. Interestingly, no oxygen-rich water from south (retroflection North undercurrent) region 2017. revealed presence an entrained reaching 2015. Beside these global patterns, island wake effects were noted. islands, particular Noronha, strongly perturbs features, with upstream core splitting reorganization single structures downstream Near flow disturbances impact thermohaline structure biogeochemistry, negative anomaly temperature (−1.3°C) salinity (−0.15) 200 400 m depth southeast side (station 5), where fluorescence peak (>1.0 mg –3 ) than at other stations located reinforcing influence flow-topography. Satellite maps sea-surface chlorophyll-a confirmed several submesoscale features study region. Altimetry data suggested cyclonic mesoscale eddy A vortex (radius 28 km) actually subsurface (150–350 depth) Atoll. This associated topographically separation. These are likely key processes providing enrichment to euphotic layer near supplying local productivity.