Pluri-decadal evolution of rock glaciers surface velocity and its impact on sediment export rates towards high alpine torrents

The acceleration of surface velocities observed over the last two decades on monitored rock glaciers worldwide is a widespread signal of the probable control of warming air temperatures on long-term permafrost creep. Yet, the actual consequences of this acceleration on sediment availability in high mountain catchments have never been properly estimated at the pluri-decadal scale. The present study evaluates the sediment transfer activity between five rock glaciers located in the western European Alps and the headwaters of the torrential channels they are respectively connected to. It reposes on the orthorectification of aerial images available generally from the 1960s to the mid-2010, to reconstruct time-series of (i) horizontal surface velocities and (ii) frontal erosion rates. Values of horizontal velocity are retrieved by tracking the displacement of boulders on the surface of rock glaciers between consecutive images while erosion rates affecting the fronts are calculated by combining these values of displacement with the geometry of the front (mean width and rock glacier thickness) derived from recent high-resolution digital elevation models. Results confirm the general acceleration of rock glaciers surface velocities since the 1970s and indicate that this accelerating trend is causing an increase in the erosion rates calculated at the front of most studied rock glaciers. In some cases and over specific periods however, the acceleration resulted in the advance of the whole landforms over their own sediments, leading to a comparatively low sediment export towards the torrents.     

Combining physical-based models and satellite images for the spatio-temporal assessment of soil infiltration capacity

The performance of managed artificial recharge (MAR) facilities by means of surface ponds (SP) is controlled by the temporal evolution of the global infiltration capacity I _c of topsoils. Cost-effective maintenance operations that aim to maintain controlled infiltration values during the activity of the SP require the full knowledge of the spatio-temporal variability of I _c . This task is deemed uncertain. The natural reduction in time of I _c depends on complex physical, biological and chemical reactions that clog the soil pores and has been observed to decay exponentially to an asymptotic non-zero value. Moreover, the relative influence of single clogging processes depend on some initial parameters of the soil, such as the initial infiltration capacity (I _c,0). This property is also uncertain, as aquifers are typically heterogeneous and scarcely characterized in practical situations. We suggest a method to obtain maps of I _c using a geostatistical approach, which is suitable to be extended to engineering risk assessment concerning management of SP facilities. We propose to combine geostatistical inference and a temporally-lumped physical model to reproduce non-uniform clogging in topsoils of a SP, using field campaigns of local and large scale tests and additionally by means of satellite images as secondary information. We then postulate a power-law relationship between the parameter of the exponential law, λ, and I _c,0. It is found that calibrating the two parameters of the power law model it is possible to fit the temporal evolution of total infiltration rate at the pond scale in a MAR test facility. The results can be used to design appropriate measures to selectively limit clogging during operation, extending the life of the infiltration pond.     

Diverse stigmaphronid wasps in Early Cretaceous amber from Spain (Hymenoptera: Ceraphronoidea: Stigmaphronidae)

A diverse fauna of wasps of the extinct parasitoid family Stigmaphronidae (Ceraphronoidea) are recorded in Early Cretaceous (Lower Albian) amber from Spain. Seven new species in five genera are described and figured based on 51 specimens, representing more material than in all the world’s other amber deposits combined. New species include: Elasmophron mari sp. nov., Libanophron sugaar sp. nov., Hippocoon basajauni sp. nov., Burmaphron jentilak sp. nov., B. sorginak sp. nov., B. iratxoak sp. nov., and Tagsmiphron olentzero sp. nov. The significance of the fauna is discussed and compared with that of other Cretaceous amber deposits, in particular the tremendous richness of the Spanish fauna is contrasted with the complete absence of stigmaphronids in the slightly younger and nearby French amber. Whether this stark difference represents particularly favorable conditions for these parasitoids, or their hosts, in the Cretaceous Spanish archipelago, or whether it is owing to taphonomic factors is discussed.     

Tectonique superposée de la zone de faille d’Arakapas (Massif de Troodos,Chypre)

Résumén

Une analyse tectonique du couloir faillé d’Arakapas est menée à partir de la mesure de plus de 3 000 plans striés relevés dans les formations ophiolitiques du Troodos et du Kellaki. Des mesures ont également été effectuées dans les formations du Crétacé terminal — Paléogène et du Néogène, afin de préciser l’âge des différents stades de la déformation. Elles ont été traitées par les méthodes des dièdres droits et du calcul du tenseur des contraintes. Il est montré que le couloir d’Arakapas a été le siège de plusieurs déformations successives. Au Néogène règne un régime en extension qui succède à un jeu décrochant dextre contemporain des compressions d’âge Crétacé terminal à Miocène. Un jeu décrochant antérieur peut-être mis en évidence. Il serait compatible avec le fonctionnement en faille transformante océanique proposé par divers auteurs.     

Fighting for a future: an actor-oriented planning approach to landscape preservation in Galicia

Modification and channelization of streams and rivers have been conducted extensively throughout the world during the past century. Subsequently, much effort has been directed at re-creating the lost habitats and thereby improving living conditions for aquatic organisms. However, as restoration methods are plentiful, it is difficult to determine which one to use to get the anticipated result. The aim of this study was to compare two commonly used methods in small Danish streams to improve the physical condition: re-meandering and passive restoration through cease of maintenance. Our investigation included measurement of the physical conditions in 29 stream reaches covering four different groups: (1) re-meandered streams, (2) LDC streams (the least disturbed streams available), (3) passively restored streams (>10?years stop of maintenance) and (4) channelized and non-restored streams. The in-stream habitats were compared through analysis of the measured physical parameters and by applying a habitat model. We found that re-meandering is a more effective way of re-creating near-natural physical conditions in small streams compared to passive restoration. This is probably due to the limited energy in small streams which restricts re-shaping of the stream channel. However, based on habitat suitability modelling, the change to the physical condition did not translate into improved habitat suitability for young of the year brown trout highlighting the value of using several methods when evaluating restoration success.     

Alternative closed‐form solutions for the mean rate of exceedance of structural limit states

Two new closed‐form expressions representing the mean rate of exceedance of a given limit state are presented herein. These proposals overcome limitations that were identified with the original formulation of the well‐known SAC/FEMA approach. The new expressions involve new parametric functions for the modeling of the seismic hazard data and for the demand evolution for increasing values of the earthquake intensity measure. Given the carefully selected parametric form of these functions, mathematical tractability is able to be maintained to establish two new closed‐form solutions representing the mean rate of exceedance of a given limit state. The function proposed for the hazard exhibits nonlinear behavior in log‐log space and is able to represent the actual hazard data over a wider range of earthquake intensity levels. The function proposed for the demand evolution addresses issues related to the inadequate performance of the SAC/FEMA approach when force‐based demand parameters such as the shear force are considered. To illustrate the applicability of the new closed‐form solutions, the probability of occurrence of several limit states is determined for a reinforced concrete structure. Copyright © 2013 John Wiley & Sons, Ltd.     

Discrimination of Nuclear Explosions against Civilian Sources Based on Atmospheric Xenon Isotopic Activity Ratios

A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of ¹³⁵Xe, ^133mXe, ¹³³Xe and ^131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination.     

Sensitivity analysis of a morphodynamic modelling system applied to a coastal lagoon inlet

This work investigates the recent morphological changes at the inlet of a complex coastal system (Ria de Aveiro lagoon, Portugal). This study was carried out using bathymetric data analysis and numerical simulations obtained with the 2DH morphodynamic modelling system MORSYS2D. The present simulations considered only tidal forcing, and a sensitivity analysis was performed by tuning the formula used to compute the sediment transports. A non-uniform sediment grain size distribution for the Ria de Aveiro inlet is considered in the numerical simulations, based on surveys performed in this area. The model results are analysed to assess if they resemble the observed trends of erosion and deposition, as calculated from bathymetric data. A quantitative analysis of the differences between the bathymetric changes obtained through surveys and the numerical results over a period of 3 years considering different sediment transport formulations shows that the formulations of Ackers and White (1973) and Engelund and Hansen (1967) are the ones that best describe the morphodynamic changes driven by tides in the Ria de Aveiro inlet.     

Fate and tidal transport of butyltin and mercury compounds in the waters of the tropical Bach Dang Estuary (Haiphong, Vietnam)

In this work, two field campaigns were performed in July 2008 (wet season) and March 2009 (dry season) to produce original data on the concentration, partition and distribution of mercury and butyltin compounds along the tropical Bach Dang Estuary located in North Vietnam (Haiphong, Red River Delta). The results demonstrate that mercury and butyltin speciation in the surface waters of this type of tropical estuary is greatly affected by the drastic changes in the seasonal conditions. During high river discharge in the wet season, there was a large estuarine input of total Hg and tributyltin, while the longer residence time of the waters during the dry season promotes increasing MMHg formation and TBT degradation. Although most of the Hg and TBT is transported into the estuary from upstream sources, tidal cycle measurements demonstrate that this estuary is a significant source of TBT and MMHg during the wet (～3kgTBT/day) and dry (～3gMMHg/day) seasons.