European dry spell length distributions, years 1951–2000

Daily precipitation records of 267 European rain gauges are considered to obtain dry spell length (DSL) series along the second half of the twentieth century. A dry spell consists of consecutive days with daily rain amount below a given threshold, R ₀. Four DSL series are obtained for R ₀ values equal to 0.1, 1.0, 5.0, and 10.0 mm/day, and their empirical distributions are properly fitted to different statistical models: Pearson type III (PE3), Weibull (WEI), generalised Pareto, (GPA) and lognormal distributions. The parameters of every model are estimated by L-moments, and the goodness of fit is assessed by quantifying discrepancies between empirical and theoretical distributions in the L-skewness–kurtosis diagrams. The most common best-fitting model is PE3, especially for 0.1 and 1.0 mm/day. Nevertheless, a few stations in southern Europe are better modelled by the WEI distribution. For 5.0 and 10.0 mm/day, the spatial distribution of the best-fitting model is more heterogeneous than for the lowest thresholds. While PE3 is still the preferred model for Western Europe, some DSL series are better fitted to WEI or GPA models. Maps of DSL average and standard deviation and expected lengths for return periods of 2, 5, 10, 25, and 50 years show some common features. Whereas for thresholds of 0.1 and 1.0 mm/day, a N–S gradient is detected, especially in Mediterranean areas; for 5.0 and 10.0 mm/day, a NW–SE gradient is observed in the Iberian Peninsula and a SW–NE gradient in the Scandinavian Peninsula. Then, the vicinity to Atlantic and Arctic Oceans and the Mediterranean Sea, as well as orographic features, are more determining factors than the latitude in patterns associated with the highest R ₀ thresholds. Finally, a regional frequency analysis based on a clustering algorithm is attempted for the four thresholds R ₀, with the PE3 model as the parent distribution for the largest clusters.     

Declining Oxygen on the British Columbia Continental Shelf

The first thorough examination of oxygen concentrations in Canadian waters of the Pacific Ocean reveals several patterns in space and time. Sub-surface concentrations of oxygen tend to be lower in shelf waters than in deep-sea waters on the same isopycnal and lower in southern waters of the continental shelf than farther north. The lowest near-bottom concentration was 0.7 ml L^?1 (31 μmol kg^?1) in mid-shelf waters in summer off southwest Vancouver Island in the Juan de Fuca Eddy region. Oxygen concentration there declined at a rate of 0.019 ml L^?1 y^?1 (0.83 μmol kg^?1 y^?1) from 1979 to 2011. This decline is attributed mainly to changes in oxygen concentrations on the same density surfaces, rather than to changes in the depth of constant-density surfaces. A numerical simulation of ocean currents and nutrient concentrations in and surrounding the Juan de Fuca Eddy in summer reveals persistent upwelling into the centre of this eddy and slow bottom currents within the eddy. Upwelled water at bottom of the Juan de Fuca Eddy has water properties associated with the California Undercurrent on the 26.6 sigma-t surface at 200 m depth, where oxygen concentration is typically 2.0 ml L^?1 (87 μmol kg^?1) and declined at a rate of 0.025 ml L^?1 y^?1 (1.1 μmol kg^?1 y^?1) from 1981 to 2011, mainly as a result of changes on constant-density surfaces rather than to uplifting isopycnals. We propose that upwelling advects deep, oxygen-poor water onto the continental shelf bottom, and the slow bottom currents allow time for oxidation of organic material in bottom waters to further reduce the oxygen concentration.

RÉSUMÉ?[Traduit par la rédaction] Le premier examen approfondi des concentrations d'oxygène dans les eaux canadiennes de l'océan Pacifique révèle plusieurs configurations dans le temps et dans l'espace. Les concentrations d'oxygène sous la surface ont tendance à être plus faibles dans les eaux de la plate-forme continentale que dans les eaux de l'océan profond sur la même isopycne et plus faibles dans les eaux du sud de la plate-forme que plus loin au nord. La concentration la plus faible près du fond était de 0.7 ml L^?1 (31 μmol kg^?1) dans les eaux du milieu de la plate-forme en été au large du sud-ouest de l’île de Vancouver dans la région du remous de Juan de Fuca. Les concentrations en oxygène à cet endroit ont diminué au rythme de 0.019 ml L^?1 a^?1 (0.83 μmol kg^?1 a^?1) entre 1979 et 2011. Cette diminution est principalement attribuée aux changements dans les concentrations d'oxygène sur les surfaces d’égale densité plutôt qu'aux changements dans la profondeur des surfaces de densité constante. Une simulation numérique des courants océaniques et des concentrations de nutrients dans le remous de Juan de Fuca et dans les régions avoisinantes en été révèle des remontées d'eau froide persistantes vers le centre de ce remous et des courants de fond lents à l'intérieur du remous. L'eau qui a remonté au fond du remous de Juan de Fuca a des propriétés liées au sous-courant de Californie sur la surface sigma–t 26.6 à une profondeur de 200 m, où la concentration en oxygène est normalement de 2.0 ml L^?1 (87 μmol kg^?1), et a diminué au taux de 0.025 ml L^?1 a^?1 (1.1 μmol kg^?1 a^?1) de 1981 à 2011, principalement à cause des changements sur les surfaces de densité constante plutôt que du soulèvement des isopycnes. Nous pausons l'hypothèse que les remontées d'eau advectent des eaux profondes pauvres en oxygène au bas de la plate-forme continentale et que les lents courants de fond donnent le temps à l'oxydation de la matière organique dans les eaux de fond, ce qui réduit davantage la concentration de l'oxygène.     

Spatio-temporal climate regionalization using a self-organized clustering approach

The authors present a novel self-organized climate regionalization (CR) method that obtains a spatial clustering of regions, based on the explained variance of physical measurements in their coverage. This method enables a microscopic characterization of the probabilistic spatial extent of climate regions, using the statistics of the obtained clusters. It also allows for the study of the macroscopic behaviour of climate regions through time by using the dissimilarity among different cluster size probability histograms. The main advantages of the presented method, based on the Second-Order Data-Coupled Clustering (SODCC) algorithm, are that SODCC is robust to the selection of tunable parameters and that it does not require a regular or homogeneous grid to be applied. Moreover, the SODCC method has higher spatial resolution, lower computational complexity, and allows for a more direct physical interpretation of the outputs than other existing CR methods, such as Empirical Orthogonal Function (EOF) or Rotated Empirical Orthogonal Function (REOF). These facts are illustrated with an example of winter wind speed regionalization in the Iberian Peninsula through the period (1979 − 2014). This study also reveals that the North Atlantic Oscillation (NAO) has a high influence over the wind distribution in the Iberian Peninsula in a subset of years in the considered period.     

Straw Blankets Sewn With Recycled Plastic Threads for Erosion and Urban Sediments Control

Soil erosion, transport and deposition of sediments represent invisible threats that along time can affect negatively the existing infrastructure of roads and dams, and the quality of air and water resources. In the last decades, a great number of researches were devoted to study erosion and sediments transportation processes. However, they addressed mostly areas of agriculture, water impoundments for dams, and land conservation. A lack of studies for erosion processes in urban areas is evident, in special those aiming to diminish the deposition of sediments originated from urban areas into the rivers and air, in special as airborne particulate. Traditionally, the costs associated in controlling erosion and sediments in urban areas are high and in some case, out of the range for most developing countries. Factors responsible for those high prices are the use of heavy equipments for soil grading and transportation, the use of costly building materials, and the need for employing more specialized personnel. In the case of gullies in urban areas, another concern is to ensure proper equipment access to the area for remediation operations. Hereby, it is presented a cost-effective method to recover an extensive gully erosion area of about 11,000 m² located in urban area. Estimated sediments released from this area to the water resources and air were estimated on about 66,000,000 tons. In this study area, bioengineering works were performed in 60 days, with hardly any sediment generated outside the work area resulting from bioengineering operations. A combination of bioengineering techniques were chosen for this study area, which was a mixture of rigid and biological products including biologs, silt fence, biodegradable straw blankets sewn with plastic threads derived from recycled PET bottles, among others. An efficient drainage system was implemented for preventing upland flow, sub-seepage and seepage. Biologs were used aiming to fulfill a double role, the first as barrier to soil sediments flow, and the second as filler for empty spaces, avoiding expensive grading operations. All engineering works were concluded in about 60 days at a cost of US0.89/m < sup > 2 < /sup > . This price is cost-effective if compared with the traditional engineering cost of approximately US 0.89/m². This price is cost-effective if compared with the traditional engineering cost of approximately US 2.92/m² because it includes extensive use of grading and soil transportation. An environmental advantage of the bioengineering method is the immediate reduction of airborne particulates. Furthermore, the overall visual aesthetics improved shortly after the implementation of the works because the bare ground was substituted by native vegetation. After 6 months the vegetation in the gully erosion area was totally established. Monitoring was performed after 12 months and no erosion and sediment transport was visually noticed. The ease implementation of this technique without the need for specialized workers in combination with low prices makes this method a model for developing countries.     

Large dam-reservoir systems: guidelines and tools to estimate loads resulting from natural hazards

This paper examines hydrodynamic pressure diagrams due to earthquakes acting on distinct configurations of the upstream face of a dam, considering the reservoir length and different bathymetries of the reservoir bottom. Two suitable mathematical models are used to obtain the dynamic pressure on the dam, and the reservoir free surface oscillation. Conceptual mathematical models are proposed to study the impact of a landslide triggered by an earthquake, and its progress into the reservoir. The waves formed when a landslide advances into the reservoir are tested with the help of laboratory results. These waves and their propagation in the reservoir are studied using experimental data and numerical results, including wave-type analyses based on dimensionless parameters. Two distinct 1DH and 2DV numerical models based on different mathematical formulations are tested. A discussion of physical and numerical results is detailed in a general risk context and uncertainty associated with the input data in a deterministic model. Numerical simulations are performed for the upper and lower limits of the sliding mass velocity diagram which is obtained as a result of the intrinsic uncertainty of the stochastic nature of the friction angle. Finally, the findings are discussed and some conclusions drawn.     

Plastic Pollution at a Sea Turtle Conservation Area in NE Brazil: Contrasting Developed and Undeveloped Beaches

Sea turtles are highly susceptible to plastic ingestion and entanglement. Beach debris were surveyed along the most important sea turtle nesting beaches in Brazil (Costa dos Coqueiros, Bahia State). No significant differences among developed and undeveloped beaches were observed in terms of total number of items. Local sources (tourism activities) represented 70% of debris on developed beaches, where cigarette butts, straws, paper fragments, soft plastic fragments, and food packaging were the most abundant items. Non-local sources (domestic and fishing activities) accounted for about 70% of debris on undeveloped beaches, where the most abundant items were rigid plastic fragments, ropes, soft plastic fragments, caps, and polystyrene. The projected surface area of beach debris did not vary among developed and undeveloped beaches. Overseas containers accounted for about 25% of regional plastic pollution, implying that international pollution prevention agreements are not being respected off the Brazilian coast.     

Mineralogical and chemical characterization of historical mortars from military fortifications in Lisbon harbour (Portugal)

Historical mortars from sixteenth to seventeenth century military forts located at the mouth of the Tagus River in Lisbon have been characterized by polarized light microscopy (PLM), thermal analysis (TG/DTA), X-ray diffractometry (XRD) and scanning electron microscopy + energy dispersive spectroscopy (SEM + EDS). The results indicate that the mortars used were all hydraulic lime-based. The presence of well-rounded lime lumps indicates a limited use of water during the lime hydration process. The detection of hydrated calcium chloroaluminate and carboaluminate compounds mostly at binder-aggregate interfaces provides evidence for the onset of pozzolanic reactions during mortar production as further confirmed by the presence of ceramic fragments in the aggregate fractions intentionally added by the fort builders to increase the hydraulic properties of the mortars. The higher mechanical strength and greater resistance to degradation processes imparted by these pozzolanic compounds could explain why, despite the extreme proximity of the investigated sites to the sea, salt weathering processes do not appear to have significantly affected the studied mortars.     

Hydrothermal faunal assemblages and habitat characterisation at the Eiffel Tower edifice (Lucky Strike,Mid‐Atlantic Ridge)

The Eiffel Tower edifice is situated in the Lucky Strike hydrothermal vent field at a mean depth of 1690 m on the Mid‐Atlantic Ridge (MAR). At this 11‐m‐high hydrothermal structure, different faunal assemblages, varying in visibly dominant species (mussels and shrimp), in mussel size and in density of mussel coverage, were sampled biologically and chemically. Temperature and sulphide (∑S) were measured on the different types of mussel‐based assemblages and on a shrimp‐dominated assemblage. Temperature was used as a proxy for calculating total concentrations of CH₄. Based on the physico‐chemical measurements, two microhabitats were identified, corresponding to (i) a more variable habitat featuring the greatest fluctuations in environmental variables and (ii) a second, more stable, habitat. The highest temperature variability and the highest maximum recorded temperatures were found in the assemblages visibly inhabited by alvinocaridid shrimp and dense mussel beds of large Bathymodiolus azoricus, whereas the less variable habitats were inhabited by smaller‐sized mussels with increasing bare surface in between. Larger mussels appeared to consume more ∑S compared with smaller‐sized (<1 cm) individuals and thus had a greater influence on the local chemistry. In addition, the mussel size was shown to be significantly positively correlated to temperature and negatively to the richness of the associated macrofauna. The presence of microbial mats was not linked to specific environmental conditions, but had a negative effect on the presence and abundance of macro‐fauna, notably gastropods. Whereas some taxa or species are found in only one of the two microhabitats, others, such as polychaetes and Mirocaris shrimp, cross the different microhabitats. Temperature was proposed to be a more limiting factor in species distribution than ∑S.     

Transition from common to private coasts: Consequences of privatization of the coastal commons

Privatization is often viewed to provide positive stimulus for the economy that can lead to the betterment of society. But when the appropriate governance systems are not functionally in place, the unwanted effects of privatization can have deleterious consequences. This paper highlights the consequences of undesirable privatization and the emergent unwanted privatization tendencies of the coastal commons, particularly in the developing countries such as the Philippines. The lack of coherent policies, standards, and weak enforcement of policies in leasing the coastal commons (e.g. various unregulated aquaculture) in the Philippines in particular, have resulted to alarming displacement, deprivation and marginalization of fishing and farming communities and have degraded many coastal zone areas. In addition, poorly planned coastal tourism and housing development projects in the foreshore areas, inappropriate reclamation of coastal areas, illegal usurpation of indigenous people’s rights over ancestral domain areas, and conversion of fishing and fish farming zones into ecotourism zones further aggravated this scenario. Equitable access to resources is of paramount importance to afford concerned stakeholders greater participation in terms of developing greater capacity for coastal communities to engage and demand for improved coastal governance - an important facet of public administration often identified as one of the challenges in managing the commons. Co-management with an Ecosystem-Based Management approach as core operational mechanism provides opportunities to enhance policy formulation and implementation, secure community safety nets, and facilitate the creation of a level-playing environment that help to prevent the unwanted effects of privatization.