Yuri Onça Prestes

The ability of the SWOT (Surface Water and Ocean Topography) satellite-derived significant wave height (SWH) estimates to represent conditions on the continental shelf of the Abrolhos Archipelago was assessed using an AWAC as the reference dataset; WAVEWATCH-III (WW3) was used as an auxiliary numerical field for spatial context. By collocating observations in space and time and applying standard statistical metrics, a high consistency between SWOT and AWAC was revealed (R ≈ 0.90; RMSE ≈ 0.25 m), with a small positive mean bias. Agreement with WW3 was likewise robust (R ≈ 0.88), indicating that the wave patterns observed by SWOT are physically consistent with the broader regional wave field represented by the numerical model. SWOT adequately represented temporal variability (including higher-energy events), although a slight overestimation tendency was detected. Overall, these findings indicate that SWOT-derived SWH reliably represents wave dynamics on the continental shelf when evaluated against in situ observations. The agreement with WW3 further supports the regional coherence of the satellite-derived wave field, reinforcing its applicability to coastal studies.

Lagrangian Coherent Structures (LCSs) in the mesoscale circulation of the Western Equatorial Atlantic (WEA), a region governed by the North Brazil Current (NBC) and its retroflection, are analyzed. Observations from 63 surface drifters deployed between 2018 and 2019 were combined with ocean analysis/forecast fields. The Finite-Time Lyapunov Exponent (FTLE) was computed using 15- and 90-day integrations to identify transport barriers and persistent structures. FTLE ridges showed strong seasonal correspondence with drifter trajectories, with 34–74% of drifter positions lying within 0.25° of attracting or repelling LCSs. Characteristic FTLE magnitudes reached ~0.3 d⁻¹, implying particle separation e-folding times of approximately 3.3 days. Spatial agreement between drifter-derived and model-based FTLE fields exhibited similar variability across seasons, with the highest correspondence during periods of intensified frontal activity. These results indicate that a substantial portion of the observed drifter motion follows or remains close to FTLE-defined pathways, supporting the robustness of the Lagrangian structures identified in the WEA. Overall, the study provides the first quantitative LCS-based characterization of mesoscale transport in this region, revealing recurrent eddies, instability zones, and flow boundaries associated with the NBC system and its interaction with the North Equatorial Countercurrent.

Wave climate variability, including seasonal cycles, long-term trends, and interannual anomalies of wave parameters, was investigated across five latitudinal sectors using ERA5 reanalysis data from 1980 to 2023. Pronounced seasonal cycles were observed in both Northern and Southern Hemisphere sectors, although the variability was more marked in the Northern Hemisphere. In contrast, the tropical region exhibited comparatively stable conditions throughout the year. Long-term trends revealed increases in both significant wave height and peak period across most sectors. The tropical region exhibited a trimodal regime driven by wind waves at low latitudes and remotely generated swells from both hemispheres. Teleconnections associated with the North Atlantic Oscillation (NAO) explained interannual variability in wind-wave direction in the tropics with an r² of 0.74 and wind-wave height variability in the Northern Hemisphere with an r² of 0.81. Additional indices, such as the Arctic Oscillation (AO), the Tropical North Atlantic (TNA) index, and the Northern Annular Mode (NAM), explained 30 to 60 percent of the directional variability. These results underscore the need to account for climate-driven variability in wave modeling frameworks to improve forecast accuracy and representation of directional trends.

The aim of the present study was to quantify the suspended solid concentrations (CSSL) and suspended solid transport (TSSL) in the mixing zone of the Pará River Estuary. This estuary is located at the southeastern extreme of the estuarine complex of the Amazon River, and receives input from Tocantins and Pará rivers and other local tributaries, with a total discharge of approximately 104 m3 s-1. Two field campaigns were conducted to collect samples of Suspended Particulate Matter (SPM) and measure turbidity. Bottom and surface samples were collected hourly throughout a semidiurnal tidal cycle at two points in the estuary (Left Margin [LM]: -0.7287° -48.2408° and Right Margin [RM]: -0.6051° -48.4048°) in both the dry and rainy seasons. The TSSL was determined using a linear correlation between SPM and turbidity. The results indicate that both the RM and LM points were export routes of suspended solids to the adjacent ocean. However, both lateral and seasonal differences were observed in the PRE samples, with the RM point exporting more suspended solids to the adjacent ocean than the LM point. The TSSL was higher in near-bottom layers on the RM, and the lutocline was broader in comparison with the LM. The correlation between the CSSL at the bottom and in the water column was higher on the LM, and indicated that approximately 80% of the CSSL on this margin derives from resuspension. The sum of the evidence indicates that both points export suspended solids to the ocean.

The Pará River estuary is a complex and special system in amazon continental shelf, with micro and mesoscale physical processes generated by forces of different sources (e.g., astronomical tides and river discharge). In this study, the main semidiurnal (M2) and the overtide (M4) components were analyzed by quantifying distortions degrees and identifying tidal asymmetries in the Pará River estuary. Two submersible tidal gauges were moored to measure the water level. One on the right margin (point #RG) and another on the left margin (#LF) recorded measurements 6 months (from September 2014 to March 2015). Furthermore, we used harmonic charts from Marine Studies Foundation (FEMAR, Fundação de Estudos do Mar). Lateral variations were also identified between #RG and #LF points from the amplitude and phase cotidal charts, with about 10 minutes delay and variation of 2 cm in tidal amplitude. We verified that the tidal wave enters in system by the right margin (#RF). The results show distortion degrees higher than 10% and positive asymmetry of the tidal wave in the Pará River, and the tidal attenuation in the estuary may be greater than 400 km upstream along the drainage basin.Keywords: Tidal distortion, Tidal asymmetry, Tidal components, Lateral variations.

Costa, M. S.; Rolnic, M., P.D., Prestes, Y.O., Rosário, R.P., and Borba, T. A.C., 2016. Runoff and Sediment Transport of Portel-Melgaço Water System in an Amazonian Estuarine System. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 18 - 22.CoconutCreek (Florida), ISSN 0749-0208. The Pará River, located in northern Brazil, receives hydrological and sediment contributions from a complex network of basins, such as the Amazon, Portel/Melgaço, and Tocantins river basins. Portel/Melgaço basin, a fluvial-estuarine system situated between the Amazon and Tocantins river basins, is still poorly known. Therefore, the objective of this study is to identify whether there is any hydrological and sediment contribution from Portel/Melgaço river basin to the Pará River. For that purpose, two campaigns were carried out: 1) June, 2013 (transitional season) and 2) March 2014 (wet season). Samplings were carried out over a tidal cycle (13 h) and consisted of a bathymetric surveys; tide measurements; cross sections of streamflows (Acoustic Doppler Current Profiler); and vertical turbidity profiles (Optical Backscatter Sensor) with water sampling (surface and bottom for Suspended Particulate Matter) at three points of the cross section. Our main conclusion is that the inflow from Pará and Amazon Rivers to Portel/Melgaço river basin is higher than the outflow and appears to be highest in the dry season. Thus, the Amazon and Pará Rivers are the main source of suspended sediments to the system, and this characterizes Portel/Melgaço river basin as a retention basin.