Predicting significant wave height with artificial neural networks in the South Atlantic Ocean: a hybrid approach

Ocean Dynamics - Accurate simulations of significant wave height (Hs) are extremely important for the safety of navigation, port operations, and oil and gas exploration. Thus, accurate forecasts of...     

Preliminary Investigation of the Molise (Italy) Earthquakes of 31 October and 1 November 2002

On 31 October and 1 November 2002, two earthquakes took place in the Italian region of Molise. 29 deaths were reported, while many buildings collapsed or suffered major damage. The tectonics of the earthquakes and historic seismicity of the area are briefly described. The distribution of damage and macroseismic intensity are confronted with the current seismic zonation of the region. In particular, the paper deals with the damage suffered by different types of structures, namely masonry and RC buildings and historical churches. The observed damage is mainly attributed to the poor quality of the materials and execution of construction, lack of maintenance and protective devices (e.g., steel ties), as well as to structural interventions. Reference is made to the management of the post-earthquake emergency. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fog measurements at the site “Falda Verde” north of Chañaral compared with other fog stations of Chile

Fog collection data registered through a Standard Fog Collector (SFC) installed by a local fishermen's association at a height of 600 m at the “Falda Verde” site, north of the Chilean harbor Chañaral (26°17′S/70°36′W), from November 1998 to November 2000, are analyzed. Trying to give new lights on the dynamics of fog along the Chilean northern coast, this article compares, for the first time, the data obtained at Falda Verde with those obtained at five other Chilean fog stations. The total time period runs from 1987 to 2001. A mean of 1.46 l/m²/day was registered at the Falda Verde site after 2 years of measurements, one of the lowest yields along the north Chilean coast. After a brief historical recapitulation of fog researches in the study area, geographical explanations of the water yields obtained in different sites are discussed. The annual mean collection from Cerro Moreno and Paposo shows a clearly different behavior from all other sites, showing a greater stability throughout the year. Other stations have a marked difference between extreme seasons. Alto Patache yields, if not the best in Chile, are very high and offer unexpected possibilities for future applications in the coast. Stations located away from the seashore (Cerro Guatalaya) are clearly less productive. Ocean proximity, altitude, south and southwest orientations of the coastal ranges and local relief explain some of the differences noted.     

Assessing aquifer vulnerability to pollutants by electrical resistivity tomography (ERT) at a nitrate vulnerable zone in NE Spain

There is an increasing demand for groundwater vulnerability maps which illustrate the exposure of aquifers against pollution. These maps show areas of greatest potential for groundwater contamination on the basis of local subsurface conditions. Parameters affecting vulnerability are mainly permeability and thickness of each protective layer. For unconsolidated sediments, the permeability is strongly related to the clay content, which can be deduced from indirect resistivity methods, like electrical-imaging. Such geophysical methods can be of great help in groundwater vulnerability studies because they disturb neither the structure nor the dynamics of the soil. Sensibility analysis was performed of the electrical resistivity tomography method for accurately mapping soil media. Managers and public administrators may effectively use this method for assessing the potential risk of groundwater contamination. In the studied zone, electrical resistivity exhibits a wide range of variability that can be easily correlated to soil parameters, such as clay content and hydraulic conductivity. A numerical index of protection has been assessed from the geophysical information derived from 2D electrical resistivity tomography. This work represents a preliminary approach on the natural vulnerability evaluation of shallow aquifers at the Empordà basin (NE Spain) that is highly affected by diffuse pollution by nitrates.     

Multidimensional scaling visualization of earthquake phenomena

Earthquakes are associated with negative events, such as large number of casualties, destruction of buildings and infrastructures, or emergence of tsunamis. In this paper, we apply the Multidimensional Scaling (MDS) analysis to earthquake data. MDS is a set of techniques that produce spatial or geometric representations of complex objects, such that, objects perceived to be similar/distinct in some sense are placed nearby/distant on the MDS maps. The interpretation of the charts is based on the resulting clusters since MDS produces a different locus for each similarity measure. In this study, over three million seismic occurrences, covering the period from January 1, 1904 up to March 14, 2012 are analyzed. The events, characterized by their magnitude and spatiotemporal distributions, are divided into groups, either according to the Flinn–Engdahl seismic regions of Earth or using a rectangular grid based in latitude and longitude coordinates. Space-time and Space-frequency correlation indices are proposed to quantify the similarities among events. MDS has the advantage of avoiding sensitivity to the non-uniform spatial distribution of seismic data, resulting from poorly instrumented areas, and is well suited for accessing dynamics of complex systems. MDS maps are proven as an intuitive and useful visual representation of the complex relationships that are present among seismic events, which may not be perceived on traditional geographic maps. Therefore, MDS constitutes a valid alternative to classic visualization tools, for understanding the global behavior of earthquakes.     

Water column characterisation on the Azores platform and at the sea mounts south of the archipelago

This study provides data concerning the hydrography and water chemistry of the Atlantic region between 29-38° N and 27-31° W, and establishes background values for dissolved Cu, Cd, Pb and As. Three water masses were identified: the Eastern North Atlantic Central Water (ENACW), the Mediterranean Water (MW) and the North Atlantic Deep Water (NADW). The ENACW exhibits a clear meridional gradient of temperature and salinity, with comparatively high values at the southern sites and lower values on the Azores platform. The ENACW, which includes the euphotic zone, also had comparatively high concentrations of oxygen and lower concentrations of nutrients and metals. The Cu, Cd and Pb results suggest that new background concentrations for OSPAR Region V (the Wider Atlantic) should be established as follows: 0.15-13nM for Cu, 0.05-1.4nM for Cd and 0.03-5nM for Pb. The background concentrations of As for OSPAR Region V should be 7-28nM.     

Principal component analysis (PCA) and mineral associations of litoraneous facies of continental shelf carbonates from northeastern Brazil

The distribution of mineral phases according to the provenance of carbonate and terrigenous facies of carbonate sediments from a large area of the continental shelf of northeast Brazil was investigated using a major element multivariate analysis approach. Heavy minerals such as ilmenite are restricted to the litoraneous facies of the continental shelf of the states of Paraíba and Pernambuco, and clay minerals are found in distal facies of the continental shelf of the State of Ceará. In the carbonate fraction, composed essentially by Mg-calcite and aragonite, there is co-variation between CaO/MgO and bathimetry in part of the studied continental shelf from depths between 15 and 20 m, apparently due to influence of the seawater temperature, degree of oxygenation and luminosity. The terrigenous facies are mainly composed of quartz, clay minerals, K-feldspars and micro-micaceous minerals, having Fe and Ti oxide and hydroxide minerals as major accessory phases. Major element behavior attests to the presence of arenaceous quartz-rich relict sediments in the 35, 60 and 80 m isobaths of the continental shelf of the state of Ceará which is here interpreted as a proxy of ancient coast lines during the Flandrian transgression.     

Quality assessment of benthic macroinvertebrates under the scope of WFD using BAT, the Benthic Assessment Tool

Assessing the health of ecosystems has become a focal point among researchers worldwide. Recently, the European Water Framework Directive intensified the development of approaches to assess ecosystems’ ecological quality. The Benthic Assessment Tool (BAT) is a multimetric approach to evaluate condition of subtidal soft bottom macroinvertebrates of coastal and transitional waters. The effects of anthropogenic disturbances on benthic macroinvertebrate communities, from 1990 to 2006, allowed testing BAT performance in Mondego estuary (Portugal). The method was able to detect decrease on ecological quality, induced essentially by eutrophication and physical disturbances, and follow communities’ subsequent recovery. It evidenced, nevertheless, some limitations associated with the unstable nature of estuaries. The ecological classification of key species in the community and the balance expected between ecological groups of estuarine communities had great influence in the final ecological assessment. Shortcomings of the method were discussed in the light of its suitability for assessing transitional waters’ condition.     

Relationship between geoacoustic properties and chemical content of submarine polymetallic crusts from offshore Brazil

Abstract

Marine mining is the ocean’s new exploration frontier, and polymetallic crusts (PMCs) and ferromanganese nodules are considered a strategic resource for the future. Acoustic geophysical methods are a valuable tool for oceanic research and have been employed for several decades in the exploration of marine resources and environmental evaluations. The main objective of this work was to investigate the correlation between the chemical composition of PMCs from three different areas along the Brazilian continental margin and their physico-acoustic attributes (P-wave velocity, density and acoustic impedance). The results show that the geoacoustic properties of PMCs are correlated to their chemical composition. Measurements showed positive and negative trends between acoustic impedance and studied elements (Fe, Mn, Co, Cu, Zn, W and Ni) according to the direction of measurement, indicting high anisotropy levels. Our study sheds initial light on the correlation between acoustic properties and metal content of PMCs. The study facilitates assessments of the acoustic responses of PMCs allowing more efficient prospection and exploitation compared to ship-board geophysical techniques that are too qualitative to identify PMCs. The results can contribute to determining the best procedures and techniques for more efficient future exploration of this resource.     

Occurrence of estrogen-like substances in the marine environment of the Northern Mediterranean Sea

Evidence has been presented that a number of environmental agents perturbs the function of the sex hormone signalling pathways in marine animals.

In this work the estrogenic/antiestrogenic activity of coastal marine water samples from five sites of the Northern Mediterranean Sea was assayed using a recombinant Saccharomyces cerevisiae yeast strain (RMY326 ER-ERE) transfected with the human estrogen receptor . Extraction of potential EDCs from seawater was performed in columns packed with XAD-2 resins.

The estrogenic activity was calculated as percentage of the activity of 17β-estradiol (10 nM) and it ranged from 4.8% and 59.03%, significantly depending on sampling site (p = 0.0013) and season (p < 0.05). Antagonistic activity of extracts was also detected and the percentage of inhibition of estradiol-dependent β-galactosidase induction ranged to 52.8%. These results point the reliability of the yeast assay as a first level screening test to assess the quality of aquatic environments.