The role of pre-existing faults in the structural evolution of thrust systems: Insights from the Ligurian Alps (Italy)

New structural and stratigraphic data for a selected area of the Ligurian Alps are combined in order to assess and discuss the role played by extensional structures in the southernmost segment of the Western Alps during thrusting. Restored cross-sections and field data suggest that the structural style in the external sector of the chain may depend upon the presence of pre-orogenic normal faults ascribed to three extensional events linked to different geodynamic contexts: (i) Permian post-Variscan plate reorganisation, (ii) Mesozoic rifting–drifting phases leading to the opening of the Alpine Tethys, and (iii) Eocenic development of the European foreland basins. During positive inversion in Eocene times, a thin-skinned thrust system developed in this area, followed by a thick-skinned phase. In both situations the inherited extensional structures played fundamental roles: during the thin-skinned phase they conditioned the thrusting sequence, also producing large-scale buckle folds and partial reactivations; during the thick-skinned phase the strain was compartmentalized and partitioned by pre-existing faults.The kinematic model of the external sectors of the Ligurian chain also allows the re-assessment of the Alpine evolution of the front-foreland transition, including: (i) indirect confirmation that in the Eocene the Ligurian Briançonnais and Dauphinois domains were not separated by the Valais-Pyrenean oceanic basin; (ii) that the thin-skinned phase progressively changed into thick-skinned; (iii) the assertion that there were no significant deformations from the Oligocene to the present-day, and the Corsica–Sardinia block rotation only produced a change in orientation of previously formed structures and normal fault system development.     

Simulations of the Madden–Julian oscillation in four pairs of coupled and uncoupled global models

The status of the numerical reproduction of the Madden–Julian Oscillation (MJO) by current global models was assessed through diagnoses of four pairs of coupled and uncoupled simulations. Slow eastward propagation of the MJO, especially in low-level zonal wind, is realistic in all these simulations. However, the simulated MJO suffers from several common problems. The MJO signal in precipitation is generally too weak and often eroded by an unrealistic split of an equatorial maximum of precipitation into a double ITCZ structure over the western Pacific. The MJO signal in low-level zonal wind, on the other hand, is sometimes too strong over the eastern Pacific but too weak over the Indian Ocean. The observed phase relationship between precipitation and low-level zonal wind associated with the MJO in the western Pacific and their coherence in general are not reproduced by the models. The seasonal migration in latitude of MJO activity is missing in most simulations. Air–sea coupling generally strengthens the simulated eastward propagating signal, but its effects on the phase relationship and coherence between precipitation and low-level zonal wind, and on their geographic distributions, seasonal cycles, and interannual variability are inconsistent among the simulations. Such inconsistency cautions generalization of results from MJO simulations using a single model. In comparison to observations, biases in the simulated MJO appear to be related to biases in the background state of mean precipitation, low-level zonal wind, and boundary-layer moisture convergence. This study concludes that, while the realistic simulations of the eastward propagation of the MJO are encouraging, reproducing other fundamental features of the MJO by current global models remains an unmet challenge.

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The effects of climate change on potential groundwater recharge in Great Britain

The predicted increase in mean global temperature due to climate change is expected to affect water availability and, in turn, cause both environmental and societal impacts. To understand the potential impact of climate change on future sustainable water resources, this paper outlines a methodology to quantify the effects of climate change on potential groundwater recharge (or hydrological excess water) for three locations in the north and south of Great Britain. Using results from a stochastic weather generator, actual evapotranspiration and potential groundwater recharge time‐series for the historic baseline 1961–1990 and for a future ‘high’ greenhouse gas emissions scenario for the 2020s, 2050s and 2080s time periods were simulated for Coltishall in East Anglia, Gatwick in southeast England and Paisley in west Scotland. Under the ‘high’ gas emissions scenario, results showed a decrease of 20% in potential groundwater recharge for Coltishall, 40% for Gatwick and 7% for Paisley by the end of this century. The persistence of dry periods is shown to increase for the three sites during the 2050s and 2080s. Gatwick presents the driest conditions, Coltishall the largest variability of wet and dry periods and Paisley little variability. For Paisley, the main effect of climate change is evident during the dry season (April–September), when the potential amount of hydrological excess water decreases by 88% during the 2080s. Overall, it is concluded that future climate may present a decrease in potential groundwater recharge that will increase stress on local and regional groundwater resources that are already under ecosystem and water supply pressures. Copyright © 2007 John Wiley & Sons, Ltd.     

Methane in shallow cold seeps at Mocha Island off central Chile

We studied for the first time the intertidal and subtidal gas seepage system in Mocha Island off Central Chile. Four main seepage sites were investigated (of which one site included about 150 bubbling points) that release from 150 to 240 tonnes CH₄ into the atmosphere per year. The total amount of methane emitted into the atmosphere is estimated in the order of 800 tonnes per year. The gases emanated from the seeps contain 70% methane, and the stable carbon isotopic composition of methane, δ¹³C-CH₄ averaged −44.4±1.4‰ which indicates a major contribution of thermogenic gas. Adjacent to one of the subtidal seeps, rocky substrates support a diverse community of microbial filaments, macroalgae, and benthic organisms. While stable carbon isotopic compositions of marine benthic organisms indicate a dominant photosynthesis-based food web, those of some hard-substrate invertebrates were in the range −48.8‰ to −36.8‰, suggesting assimilation of methane-derived carbon by some selected taxa. This work highlights the potential subsidy of the trophic web by CH₄-C, and that its emission to the atmosphere justifies the need of evaluating the use of methane to support the energy requirements of the local community.     

VST OmegaCAM difference image analysis

We present a modified version of the difference image analysis software developed by the OGLE collaboration (DIAPL) and its implementation within AstroWISE environment. Python interface and parallel execution are described. Examples of graphical output on simulated data set are presented. The tool will be used in VST surveys for photometric variability search.     

Teleconnection–extreme precipitation relationships over the Mediterranean region

The relationship between five teleconnection patterns (North Atlantic Oscillation (NAO), Arctic Oscillation (AO), East Atlantic/Western Russian (EAWR) pattern, Scandinavian (SCAND) pattern, and El Niño Southern Oscillation (ENSO)) and the frequency of occurrence of days (per month) with extreme precipitation in the Euro-Mediterranean region is investigated with National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis data. To quantify the teleconnection–precipitation relationships over the Euro-Mediterranean region, linear correlations are calculated between the monthly teleconnection indices for the five patterns and time series at each grid point of the monthly frequency of days with extreme precipitation, focusing on daily precipitation amounts that exceed a particular threshold value (a 90 % threshold is used). To evaluate dynamical processes, the teleconnection indices are also correlated with the frequencies of days with extreme values of dynamic tropopause pressure and precipitable water. The former quantity is used as a proxy for potential vorticity intrusions and the latter to identify regions of enhanced moisture. The results of this analysis indicates positive, statistically significant correlations between the NAO, AO, and SCAND indices and the frequency of extreme precipitation in the western Mediterranean; positive (negative) correlations between the EAWR index and the extreme precipitation frequency in the eastern (western) Mediterranean; and a positive correlation between the Niño3.4 index and the extreme precipitation frequency over the Iberian Peninsula and the Middle East. For all of the teleconnection patterns other than ENSO, the dynamic tropopause pressure correlation patterns resemble those for the precipitation. In contrast, similar precipitation and precipitable water correlation patterns are observed only for ENSO. These findings suggest that the teleconnections affect the interannual variation of the frequency of days with extreme precipitation over a large part of the Euro-Mediterranean region through their impact on the spatial distribution of regions with enhanced potential vorticity and air moisture.     

How do management alternatives of fast-growing forests affect water quantity and quality in southeastern Brazil? Insights from a paired catchment experiment

Fast-growing forest plantations have been expanding in Brazil in the last 50 years, which reach productivities by over 40 m³ ha⁻¹ year⁻¹ in reduced rotation between 5 and 15 years. In the 1990s, environmental warnings about these plantations guided research projects seeking to understand their effects on water and propose forest management actions to minimize them. The assessment of forest management effects on water resources is conducted by long-term experiments in paired catchments. In this paper we present results of some studies conducted at the hydrological monitoring centre of Itatinga Experimental Forest Station, of the University of São Paulo, where hydrological monitoring began in 1987, and currently include three catchments (83–98 ha) under different forest management regimes: short-rotation Eucalyptus plantation, long-term forest plantation mosaic and native forest restoration. Results show that at similar conditions observed at study area including deep soils and good natural water regulation, hydrological effects vary according to the forest management regime adopted, increasing water consumption and making the flow regime vulnerable to intra- and inter-annual seasonality. Regarding water quality, weekly sampling results showed suspended sediments and nitrate concentrations below water quality thresholds criteria by silvicultural operations, and the effects were transient but higher concentrations of nutrients were observed in intensive management regime. In the study area, reducing the management intensity of forest plantation by increasing the rotation time, adopting forest age mosaic and avoiding the coppice technique are alternative choices that reduced water use and increased flow regulation. Different adopted forest management schemes directly affected water use, showing that in water-deficit tropical regions, management regime of fast-growing forest plantations controls water availability.     

Assessment of meteorological climate models as inputs for coastal studies

Modeling studies of future changes in coastal hydrodynamics, in terms of storm surges and wave climate, need appropriate wind and atmospheric forcings, a necessary requirement for the realistic reproduction of the statistics and the resolution of small scale features. This work compares meteorological results from different climate models in the Mediterranean area, with a focus on the Adriatic Sea, in order to assess their capability to reproduce coastal meteorological features and their possibility to be used as forcings for hydrodynamic simulations. Five meteorological datasets are considered. They are obtained from two regional climate models, implemented with different spatial resolutions and setups and are downscaled from two different global climate models. Wind and atmospheric pressure fields are compared with measurements at four stations along the Italian Adriatic coast. The analysis is carried out both on simulations of the control period 1960–1990 and on the A1B Intergovernmental Panel for Climate Change scenario projections (2070–2100), highlighting the ability of each model in reproducing the statistical coastal meteorological behavior and possible changes. The importance of simulated global- and regional-scale meteorological processes, in terms of correct spatial resolution of the phenomena, is also discussed. Within the Adriatic Sea, the meteorological climate is influenced by the local orography that controls the strengthening of north-eastern katabatic winds like Bora. Results show indeed that the increase in spatial resolution provides a more realistic wind forcing for the hydrodynamic simulations. Moreover, the chosen setup and the global climate models that drive the regional downscalings appear to play an important role in reproducing correct atmospheric pressure fields. The comparison between scenario and control simulations shows a small increase in the mean atmospheric pressure values, while a decrease in mean wind speed and in extreme wind events is observed, particularly for the datasets with higher spatial resolution. Finally, results suggest that an ensemble of downscaled climate models is likely to provide the most suitable climatic forcings (wind and atmospheric pressure fields) for coastal hydrodynamic modeling.     

The Twannberg (Switzerland) IIG iron meteorites: Mineralogy,chemistry, and CRE ages

Abstract— The original mass (15915 g) of the Twannberg IIG (low Ni‐, high P) iron was found in 1984. Five additional masses (12 to 2488 g) were recovered between 2000 and 2007 in the area. The different masses show identical mineralogy consisting of kamacite single crystals with inclusions of three types of schreibersite crystals: cm‐sized skeletal (10.5% Ni), lamellar (17.2% Ni), and 1–3 × 10 μm‐sized microprismatic (23.9% Ni). Masses I and II were compared in detail and have virtually identical microstructure, hardness, chemical composition, cosmic‐ray exposure (CRE) ages, and ¹⁰Be and ²⁶Al activities. Bulk concentrations of 5.2% Ni and 2.0% P were calculated. The preatmospheric mass is estimated to have been at least 11,000 kg. The average CRE age for the different Twannberg samples is 230 ± 50 Ma. Detrital terrestrial mineral grains in the oxide rinds of the three larger masses indicate that they oxidized while they were incorporated in a glacial till deposited by the Rhône glacier during the last glaciation (Würm). The find location of mass I is located at the limit of glaciation where the meteorite may have deposited after transport by the glacier over considerable distance. All evidence indicates pairing of the six masses, which may be part of a larger shower as is indicated by the large inferred pre‐atmospheric mass.     

EXOTIME: searching for planets around pulsating subdwarf B stars

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time scales of several years with two immediate observational goals:

1. determine $\dot{P}$ of the pulsational periods P
2. search for signatures of substellar companions in O–C residuals due to periodic light travel time variations, which would be tracking the central star’s companion-induced wobble around the centre of mass

These sets of data should therefore, at the same time, on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the $\dot{P}$ (comparison with “local” evolutionary models), and on the other hand allow one to investigate the preceding evolution of a target in terms of possible “binary” evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally expensive method to search for companions, it samples a different range of orbital parameters, inaccessible through orbital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive toward wider separations. In this paper we report on the status of the on-going observations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational characteristics in HS?0444+0458, while showing HS?0702+6043 to be more complex than previously thought.