A statistically significant signature of multi-decadal solar activity changes in atmospheric temperatures at three European stations

We study the effect of solar variability on temperatures recorded in three European stations with the longest gapless series available (Prague, Bologna and Uccle). Following a pattern recognition approach, we partition daily temperature “indices” (minimum, maximum and range) in two separate classes with respect to the level of solar activity (high H vs low L 11 year cycles). Using the two-sample Kolmogorov–Smirnov statistics, multiple shuffles of data, and other partitions, we demonstrate that the separation between the probability distribution functions of H and L temperatures is statistically significant and robust. We find that average annual variations for the H and L classes display common and site-specific patterns. For practically all series considered, differences between graphs of annual change for the two classes H and L are large (～1 °C). Solar activity accounts, at least in part, for the multi-decadal variations in temperature observed at these European sites in the past two centuries.     

March 1986 eruptive episodes at Piton de la Fournaise volcano (Reunion Island)

From May 1985 to April 1986 five discrete eruptions have occurred at Piton de la Fournaise volcano. On March the 17th, a sixth episode began with four distinct stages. They took place along the southeast rift zone of the volcano, from the summit to the sea coast. It was the first rift zone eruption in the south since 1800 A.D. and the first ever monitored at Piton de la Fournaise volcano.Three fissural vents opened at decreasing altitude emitting about 12 to 15 × 10⁶ m³ of olivine basalts between 19th March and 1st April. Strong seismic activity was accompanied by deformation of the summit area, and large-scale variations of the magnetic field. A summital event characterized the end of the flank activity with collapse of a new pit-crater and outflow of small amounts of degassed aphyric basalt.     

Sources and history of heavy metal contamination and sediment deposition in Tivoli South Bay, Hudson River, New York

Persistent inorganic constitutents preserved in sediments of aquatic ecosystems record temporal variability of biogeochemical functioning and anthropogenic impacts.²¹⁰Pb and¹³⁷Cs dating techniques were used to study the past variations of heavy metals (Pb, Cu, and Zn) and accumulation rates of sediments for Tivoli South Bay, in the Hudson River National Estuarine Research Reserve ecosystem. South Bay, a tidal freshwater embayment of the Hudson, may play an important role in the sediment dynamics of this important river. The measured sedimentation rate range of 0.59 to 2.92 cm yr⁻¹ suggests that rapid accumulation occurred during the time period represented by the length of the cores (approximately the past 50 yr). Direct measurements of sediment exchange with the Hudson River reveal high variability in the sediment flux from one tidal cycle to the next. Net exchange does not seem to be adequate to explain sediment accumulation rates in the bay as measured by²¹⁰Pb and¹³⁷Cs. The difference may be supplied from upland streams or the Hudson River during storm events. Concentrations of the metals Pb, Cu and Zn were found to be well correlated with each other within individual cores at five of six sites tested. This suggests a common proximate source for the three metals at a specific site. The evidence is consistent with mixing in some environmental compartment before delivery to the bay. While metals self-correlate within individual cores, absolute concentrations, depth distribution patterns, and ratios of the metals to each other vary among the cores collected at different locations within the bay. Organic matter, Fe content, and particle size distribution of sediments do not account for the intercore variations in metal concentration. It is likely that cores collected from different sites may have derived metals from different sources, such as watershed streams and tidal exchange with the Hudson River.     

Coupling between progressive damage and permeability of concrete: analysis with a discrete model

A significant increase of the permeability of concrete upon micro‐cracking and a good correlation between the evolution of damage (material stiffness) and permeability are observed experimentally. The present contribution investigates this correlation theoretically, with the help of lattice analyses. Scaling analysis of lattices which contain elastic brittle bonds has shown that the material degradation should be described by the evolution of the material stiffness, or compliance, in a continuum setting (damage models). This result is reviewed and further documented in the first part of the paper. In the second part, hydro‐mechanical problems are considered with the construction of a hydraulic lattice, dual to the mechanical one. We observe that the average permeability upon micro‐cracking is the lattice scale‐independent controlling variable in the hydraulic problem. Additionally, results show that in a continuum poro‐mechanical approach, the evolution of the material permeability ought to be related to the elastic unloading stiffness, described e.g. with the help of continuum damage variables. Copyright © 2005 John Wiley & Sons, Ltd.     

Atlantic remote sensing land ocean experiment (ARSLOE): Overview

ARSLOE was a multiorganization experiment held October 6-November 30, 1980, near Duck, North Carolina. It provided a large number of wind-wave and related measurements to intercompare and develop wave measurement systems, to evaluate and improve wave models, and to provide basic information on wave mechanics in shallow water. This paper provides an overview of the experiment.     

Equilibrium state of diopside-bearing harzburgites from ophiolites: Geobarometric and geodynamic implications

The bulk compositions of coexisting enstatite and diopside in basal lherzolites and clinopyroxene-bearing harzburgites from ophiolitic complexes are typical of solidus/subsolidus equilibria, but for a few texturally distinct magmatic diopsides. They would presumably reflect the state of equilibrium at the time they last coexisted with liquid as the rocks reentered subsolidus conditions. The total lack of correlation between Al and Ca concentrations shows that the compositional scatter observed for any given massif, results from analytical errors related to extensive exsolution and serpentinization, rather than from differences in equilibrium conditions. However, significant differences are found between the residual ophiolitic lherzolites from Hare Bay, Newfoundland, and from Xigaze, Tibet, two massifs selected for their distinct structural and textural features. As for thermobarometry techniques relevant to these rocks, the best barometer found is an empirical relation for the expression of pressure as a virtually temperature-independent function of the ratioK _f=(X _Di ^opx )/(1 –X _Di ^cpx ), in agreement with semi-quantitative models based on natural solid solutions. Temperatures are then simply derived from a surface-fitting expression relating pressure, temperature and diopside-solvus compositions, according to a regularX _En ^cpx solution model (CMS) corrected for the effect of Al in the spinel facies. Application of these techniques yield pressures of 0.4 and 1.4 GPa, i.e. depths from sea-bottom of about 13 and 43 km, for temperatures of 1,170 and 1,300° C for the ophiolitic lherzolites of Tibet and New-foundland, respectively, in good agreement with dry-solidus data by radioactive tracing and with geothermal-model estimates for ridges.     

Multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system

The study of groundwater hydrogeochemistry of the Paleozoic Basses-Laurentides sedimentary rock aquifer system in Québec produced a large geochemical dataset. Groundwater samples were collected at 153 sites over a 1500 km² study area and analyzed for major and minor ions. The large number of data can lead to difficulties in the integration, interpretation and representation of the results. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples, and to identify geochemical processes controlling groundwater geochemistry. This subgroup consisted of 144 samples and 14 parameters (Ca²⁺, Mg²⁺, Na⁺, K⁺, , Cl⁻, , Fe²⁺, Mn²⁺, Br⁻, Sr²⁺, F⁻, Ba²⁺, HS⁻). Seven geochemically distinct clusters, C1–C7, resulted from the HCA. Samples from clusters C3, C4, C6 and C7 are mostly located in preferential recharge areas. The majority of these samples have Ca–Mg–HCO₃ recharge groundwater (C3, C6, C7) and Na–HCO₃ evolved groundwater (C4). Samples from the other three clusters (C1, C2, C5) are characteristic of an aquifer system under confined conditions. The majority of these samples have Na–HCO₃ evolved groundwater (C1, C5) and Na–Cl ancient groundwater that exhibits elevated concentrations in Br⁻ (C2). In addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry, the distribution of clusters also showed the importance of the geological formations on minor and trace elements, such as Fe²⁺, Mn²⁺, Sr²⁺, F⁻ and Ba²⁺. The first five components of the PCA account for 78.3% of the total variance in the dataset. Component 1 is defined by highly positive loadings in Na⁺, Cl⁻ and Br⁻ and is related to groundwater mixing with Champlain Sea water and solute diffusion from the marine clay aquitard. The high positive loadings in Ca²⁺ and Mg²⁺ of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system. From their characteristic loadings, the first two components are defined as the “salinity” and “hardness” components, respectively. Components 3–5 are related to more local and geological effects. The integration of the HCA and the PCA, with conventional classification of groundwater types, as well as with the hydrogeological and geological contexts, allowed the division of the region into four main geochemical areas, providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater. The following factors were recognized as influencing the evolution of groundwater identified in every geochemical area: (1) geological characteristics including sedimentary rock type and till mineralogy; (2) hydrogeological characteristics represented by the level of confinement and the hydraulic gradient; and (3) the geological history including the latest glaciation and the Champlain Sea invasion. With its integrated approach, this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems, and provides an example of the long-term geochemical evolution of hydrogeological systems after a major perturbation, in this case seawater invasion.     

An Effective Approach to Rehabilitate Damaged Barrier System Against Piping and Contaminant Flow

The monitoring operation of an older impoundment (such as dams and waste barrier materials) during the service life of the structure cannot be overemphasized. Since older infrastructures seem to be more susceptible to piping and seepage failure, their construction design should be analyzed and monitored at places where a potential problem could occur. Once an impoundment is constructed without adequate filters layers and foundation treatments, then the prevention of piping or seepage may require an effective approach to constructing a cut-off wall to prevent eventual failure. In order to identify and understand theses failure modes, it is important to identify the physical parameters of the impoundment system, such as the zones of various soil gradations, the compaction of these zones, the hydraulic conductivity, the compatibility of the soil formations within and beneath the core or liner, as well as the cohesive and dispersive properties of soils at various location within the structure. Once these parameters are known and quantified, an adequate assessment of the structure’s susceptibility to piping or contaminant transport can be established. This type of an analysis will enable the proper design of a cut-off wall and predetermine the effectiveness of its long-term performance. The Vermont Waterbury Dam (built in 1938) is example of seepage related problem that implemented a cut-off wall design to prevent piping paths from undermining the structure. In this case, some forensic sampling had to be performed and the parameters of the soils as just mentioned were key factors in determining the wall design. In this paper, the Waterbury dam rehabilitation is investigated as case studies, in order to better understand how older designs and poor construction of impoundments can lead to piping condition in dams as well as failures in waste barrier systems. The Secant Cut-off wall (constructed at Waterbury Dam) is mentioned as a corrective measure taken for this dam and there is a brief discussion as to how this construction rehabilitation technique can be applied to waste barrier impoundments.     

Roughness length in the turbulent Ekman layer above the sea bed

Roughness lengths were determined from average current profiles in the logarithmic boundary layer at a site in the southern North Sea. Grab samples indicated that the bed configuration controlling the bed roughness was unlikely to change even at maximum spring tides, but the measured roughness lengths were found to decrease as the speed of the flow 10 m above the bed increased. This has been qualitatively interpreted in terms of the size of the turbulent eddies within the flow and their effectiveness at “feeling” the size of the elements forming the bed roughness. It is also shown that the dependence of the observed drag coefficient on the Rossby number follows closely the theoretical form when the roughness length decreases with increasing flow speed.     

Electromagnetic 2.5-dimensional forward modelling with a boundary integral formulation

An effective and accurate technique for the numerical solution of 2-D electromagnetic scattering problems with 3-D sources is presented. This solution introduces a set of the usual boundary integral equations and uses a scalar Green's function. In this scalar version, the unknowns of the problem are the boundary values of the longitudinal fields and their normal derivatives in the Fourier domain. A generalization of the usual boundary integral formulation enables us to handle a large class of models composed of piecewise homogeneous domains, including contiguous domains, multiply-connected domains and unbounded domains. This formulation involves the solution of a system of linear equations, and results in a significant saving in computation time in comparison with other rigorous methods.
  The requirements for the numerical implementation of this solution are described in detail. Numerical tests were carried out using the important example of electromagnetic tomography. The specific symmetry properties of the response function in this case are illustrated. Numerical accuracy is verified over a large frequency range, up to 1  MHz.