Renato Mendes

University of Porto | UP · +Atlantic CoLAB

Coastal municipalities and industries often discharge poorly treated wastewater into proximate marine and estuarine environments. The urban and/or effluent input can lead to eutrophication and lower water quality, as it holds high concentrations of nutrients and pollutants. One widely applied tool to increase effluent dispersion and direct it away...

Internal waves occur within the water column, where stratification is needed for its generation and propagation. Their range and scale is much larger than typical surface waves, and have the potential to propagate along great distances throughout the depths of the ocean. They can have an impact on several aspects and processes, mainly in the vertic...

The study of dynamic features of the ocean, in which complex physical, chemical, and biological interactions evolve on multiple time scales, poses significant sampling challenges because the required spatial and temporal resolutions are not possible by ship or satellite studies alone. Satellite remote sensing captures only surface effects while exp...

Marine pollution incidents can have a huge impact on different ecosystems, with unpredictable short- and long-term consequences. Once the pollutant is detected, it is critical to quickly understand its characteristics so that authorities can lay out an adequate response. In parallel to the time- and cost-constrained traditional operational means, t...

The precise evaluation of the conservation status of salt marshes, the understanding of the mechanisms behind loss and degradation, and the anticipation of future threats are fundamental to assist management solutions able to reverse the declining trend observed in these environments. Previous methods combining remote sensing and hydrodynamic model...

The Minho and Lima estuaries comprise important and sensitive protected areas valuable for species and habitats conservation, constituting a reference for ecotoxicological and water quality studies. These estuaries, separated only by 20 km, are very productive systems with high metabolic rates that strongly influence the cycle of nutrients and the...

Study of ocean processes is important to understanding climatic variability especially on the productive upper water-column. Ocean currents regulate the climate, it captures CO\(_2\) from the atmosphere and oxygen is generated by its plankton communities, all of which are part of the global environmental cycle which are being impacted by anthropoge...

Internal waves (IWs) in the ocean span across a wide range of time and spatial scales and are now acknowledged as important sources of turbulence and mixing, with the largest observations having 200 m in amplitude and vertical velocities close to 0.5 m s−1. Their origin is mostly tidal, but an increasing number of non-tidal generation mechanisms ha...

Study of ocean processes is important to understanding climatic variability especially on the productive upper water-column. Ocean currents regulate the climate, it captures CO2 from the atmosphere and oxygen is generated by its plankton communities, all of which are part of the global environmental cycle which are being impacted by anthropogenic c...

Reliable information on salt marsh extent and condition is crucial to promote effective management strategies towards their maintenance and recovery. Most of previous studies on salt marsh extent assessment used Landsat-derived Normalized Difference Vegetation Index (NDVI), being limited the current knowledge about the performance of other Vegetati...

General problems of optimal trajectory generation and of optimal space-time rendezvous for autonomous underwater vehicles affected by time-varying fluid flows are formulated and solved in the framework of dynamic programming. The optimal solutions include optimal trajectories, as well as departure times and positions. The approach consists in using...

Previous front-tracking (front-following) algorithms for marine robots have been developed for-and applied to-coastal fronts such as wind-driven coastal upwelling fronts or river plume fronts. During the R/V Falkor cruise FK180528 in May-June 2018 we developed a new, universal front-following algorithm based on a novel concept of tracking front's a...

Ocean fronts are dynamic three-dimensional (3D) structures that can be effectively and efficiently sampled with robots, particularly with autonomous underwater vehicles (AUVs). Search, mapping and tracking of large-scale open ocean fronts require a mix of different types of robots, each with certain advantages and constraints. The limited endurance...

The Douro is one of the largest rivers of the Iberian Peninsula, representing the most important buoyancy source into the Atlantic Ocean on the northwestern Portuguese coast. The main goal of this study is to contribute to the knowledge of physical processes associated with the propagation of the Douro River plume. The general patterns of dispersio...

In the last few years, the technological development of underwater robotics has been a key factor to improve oceanographic research. Autonomous underwater vehicles (AUVs) are especially well suited for coastal studies because they can provide near-synoptic spatial observations. Their high spatial and temporal resolutions combined with exceptional m...

We consider the problem of generating optimal planar trajectories for marine vehicles taking into account the effect of time-varying ocean currents. This is motivated by the need for economic trajectory generation in long-duration operations, and it becomes even more important in scenarios where the magnitude of the ocean current speed is comparabl...

This paper presents a report from a cruise onboard the R/V Falkor oceanographic vessel from the Schmidt Ocean Institute. The goal of this cruise was to demonstrate a novel approach to observe the ocean with multiple underwater, surface, and aerial vehicles, as well with the R/V Falkor also used as the base and control center for all assets. We desc...

We describe the 2018 edition of the Recognised Environmental Picture exercise (REP18). Every year, the Portuguese Navy hosts an international exercise where challenging and novel operational scenarios are tested in a controlled environment. This is done to achieve a readiness level that allows the use of those developments in future real-world scen...

Currents, wind, bathymetry, and freshwater runoff are some of the factors that make coastal waters heterogeneous, patchy, and scientifically interesting—where it is challenging to resolve the spatiotemporal variation within the water column. We present methods and results from field experiments using an autonomous underwater vehicle (AUV) with embe...

Salt marshes support estuarine biodiversity and provide ecosystem services; however, their general decay is being observed worldwide, in large part due to land reclamation. Accordingly, there is a growing concern about salt marsh preservation status having in mind the promotion of effective management decisions towards their conservation and restor...

Efficient sampling of coastal ocean processes, especially mechanisms such as upwelling and internal waves and their influence on primary production, is critical for understanding our changing oceans. Coupling robotic sampling with ocean models provides an effective approach to adaptively sample such features. We present methods that capitalize on i...

Propagation of river plumes along coast strongly depends on several physical processes, which determine the plume fate over shelf. Traditional methods of in situ is often very difficult and expensive due to great spatial and temporal variability of its dominant drivers. Here we report a method and preliminary results of using autonomous underwater...

The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixe...

Tidal constituents list used to reconstruct the tidal series. (DOCX)

The Douro River represents the major freshwater input into the coastal ocean of the northwestern Iberian Peninsula. The seasonal and interannual variability of its turbid plume is investigated using ocean color composites from MODIS (Moderate Resolution Imaging Spectroradiometer) sensor aboard the Aqua and Terra satellites (2000-2014) and long-term...

Internal waves (IWs) are typically the most energetic high-frequency events in the coastal ocean. These large-wavelength waves are difficult to measure with in-situ or shipboard instruments. Therefore, remote sensing has been the main tool for IW observations. Although IWs have been observed in the Portuguese offshore region using from satellite-ba...

Ocean color imagery from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the Aqua platform is used to characterize the interannual variability of turbid river plumes off central-southern Chile. Emphasis is placed on the influence of climate fluctuations, namely El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO)...

The Douro and Minho Rivers are the most important freshwater contributors on the northwestern coast of the Iberian Peninsula. Although their interaction is poorly understood, it is well known that they generate the Western Iberian Buoyant Plume (WIBP). This study aims to research the interaction of the Douro and Minho estuarine plumes under winter...

The central coastal region of Portugal presents high hydrographic variability induced by seasonal variations of wind stress, estuarine discharge and topographic features as canyons and capes. The use of sophisticated circulation and transport models to study coastal oceanography is a challenging and actual issue worldwide. This work presents a new...

The Minho River, situated 30 km south of the Rias Baixas, is the most important freshwater source flowing into the Western Galician coast (NW of the Iberian Peninsula). The buoyancy generated by the Minho estuarine plume can reverse the normal circulation pattern inside the Rias Baixas affecting the exchange between the Rias and the ocean, changing...

Rivers discharges cause the formation of buoyant plumes in the adjacent coastal area at their mouths, which are characterized by low-salinity water and controlled by outflow inertia, rotation (Coriolis) effects, buoyancy, wind, and tide forcing. The turbid plumes influence the adjacent coastal area, since they control the patterns of nutrients, se...

Storm surges are a hazardous phenomenon, since they may flood large coastal areas, causing socio-economical and habitation losses. Thus, the study of their characteristics and effects in coastal regions is crucial to prevent their negative consequences. This work aims at assessing the storm surges impact in the hydrodynamics of a tidal lagoon locat...

Numerous studies based on tide gauge records demonstrated the sea level rise on the Portuguese coast during the last century. Different climatic models predict a mean sea level rise for this coast ranging between 0.28 m and 0.42 m, for the period 2091-2100 relative to 1980-1999. Thus, the potential evaluation of the sea level rise impact on the Por...

Over the last years several studies have been performed about the hydrodynamic and the water properties transport in the Ria de Aveiro lagoon, but none of them had the focus on the dispersal of the lagoon plume into the adjacent Atlantic Ocean. This buoyant plume injects less dense water in to the ocean during the ebbing, which penetrates onto the...

The mean sea level rising is an important consequence of climate change because of its impact on society and coastal ecosystems. Tide gauge information evidences that global mean sea level has increased in the 20th century, and it is expected that its rise will continue during the 21th century. However, the sea levels are not changing uniformly aro...

The Ria de Aveiro lagoon is one of the largest shallow water estuarine systems in Portugal. It is characterized by a large number of narrow channels and intertidal areas. Despite several previous hydrodynamic studies about this system, their surrounding low lying lands were never included in the numerical bathymetries developed. The objective of th...

In recent years, oil spill pollution resulting from maritime accidents has affected several points around the globe. After the sinking of the Prestige oil tanker off Galicia, this problem acquired high relevance in Portugal. The portuguese coast and its EEZ are located in an area of intense maritime traffic, and therefore are under the dangerous th...