First-principles study of OH defects in zircon

The infrared spectroscopic properties of selected OH defects in zircon are investigated by first-principles calculations. The explicit treatment of the coupled nature of OH motions in the stretching modes, together with the calculation of the intensity and polarization of absorption bands, makes it possible to directly compare theoretical and experimental data. The bands observed at 3,420 cm^?1 (polarization parallel to c axis) and 3,385 cm^?1 (polarization perpendicular to c axis) in natural and synthetic samples correspond to the IR-active vibrational modes of the hydrozircon defect, that is, fully protonated Si vacancy. The broad band observed at 3,515 cm^?1 in the spectrum of zircon crystals grown in F-rich environments is consistent with the occurrence of composite (OH,F) tetrahedral defects. Calculations also show that the band observed at 3,200 cm^?1 in the spectrum of synthetic undoped samples can be ascribed to fully protonated Zr vacancies. The theoretical values of integrated absorption coefficients indicate that general correlations can be reasonably used to determine the concentration of OH groups in zircon.     

Assessing adaptive capacity within regional climate change vulnerability studies—an Alpine example

Adaptive capacity represents a crucial component in the assessment of a region’s vulnerability to climate change. The term adaptive capacity is only fuzzily defined, and determining it is difficult and often neglected in previous studies. In this paper, a newly developed adaptive capacity concept is introduced, with a respective indicator/criteria system and simple aggregation methods. The approach allows for adaptive capacity assessments at 3 levels of specificity (impact specific, sector specific and regional generic). The selection of indicators is tailor-made for Alpine regions, where the approach has been widely tested. The presented approach requires extended stakeholder involvement, namely for the evaluation of the indicators. The overall effort needed for its implementation remains reasonable. The outcome of the assessment exercise does not provide precise objective measurements, but remains an indicative estimation due to the fuzziness and complexity of the underlying concept. The conceptual approach is transferable to other mountain areas and beyond, the selection of indicators however is only valid for the Alpine region. The showcase presents results from the adaptive capacity assessment in the region of South Tyrol, where the method was carried out as part of a climate change vulnerability study. The outcomes indicate a number of issues that future actions could address in order to improve adaptive capacity in the region, namely in the field of prevention measures against meteorological extremes and natural hazards.     

Cost assessment of losses due to recent reactivation of Kaliasaur landslide on National Highway 58 in Garhwal Himalaya

National Highway (NH) 58 is one of the important and the major lifelines, which connects Uttarakhand state with rest of the country and linked with its socioeconomic progress. Uttarakhand, being one of the major tourist and pilgrimage hubs of the country, highways are preferred to be consistently maintained and trafficable. However, due to frequent landslide occurrences, particularly during monsoon months (July to September), the highway is poorly maintained. There are hundreds of landslides along the NH 58 starting from Rishikesh (the foot of the Garhwal Himalaya) to Badrinath, the holy shrine of India covering a distance of 320 km. Many landslides are historic, 4–5 decades old and recurring every year during monsoon. Kaliasaur landslide (147 km), Pakhi landslide (250 km), Tangni landslide (254 km), Patalganga landslide (256 km), and Lambagarh landslide (302 km) are a few among the critical ones. Kaliasaur landslide that is one of the most critical landslides recurring for over 9 decades at 147 km on National Highway 58 (from Haridwar) has been selected for the study. It has reportedly occurred first time in 1920 and since then recurring at regular intervals, causing huge socioeconomic losses involving both direct and indirect costs. Previous records of any attempt to estimate the direct (rehabilitation cost, cost on prevention and control) or indirect cost (expenses due to detouring, cost of productive time loss, loss of tourism, and loss in business) have not been found. As a result, the accurate economical impact of landslide on society is very roughly estimated. Even if the estimates of indirect losses are roughly estimated, added with some direct losses will provide the basis for developing the right strategies for proper mitigation and management of landslides. In this paper, an effort is made, first time, to examine the effects of Kaliasaur landslide on socioeconomics of the region. Since the direct losses on property damaged could not be estimated due to lack of recorded documentation, this study mainly focuses on the indirect losses on detouring during the damage/blockage of the highway and some significant direct losses such as restoration work, loss of lives, and damage of vehicles.     

Co-seismic ruptures and deformations recorded by speleothems in the epicentral zone of the Basel earthquake

Abstract

The study of growth anomalies of speleothems in a karstic environment can provide potential evidence or palaeoearthquakes. These data are used to study the recurrence times of major earthquakes in areas where evidence for historic seismicity is lacking. A study has been carried out in the epicentral area of the 1356 Basel earthquake (epicentral intensity = VII-VIII, macroseismic magnitude = 6.2). The Bättlerloch and Dieboldslöchli caves, situated in the area of greatest damage, show growth anomalies of speleothems possibly related to a seismic event (several breaks of speleothems an offsets of the axis of the regrowths). The first U/Th disequilibrum measurements by alpha spectrometry show recent ages (less than several tens of thousands of years and pro a y historic). ¹⁴C dating by AMS of carbonate laminations taken on both sides of the anomalies confirm the evidence of a seismic event around 1300 AD. More accurate datings by U/Th TIMS are carried out in order to compare the information provided by the two different dating methods. © Elsevier, Paris     

Linking the NE Anatolian and Lesser Caucasus ophiolites: evidence for large-scale obduction of oceanic crust and implications for the formation of the Lesser Caucasus-Pontides Arc

In the Lesser Caucasus and NE Anatolia, three domains are distinguished from south to north: (1) Gondwanian-derived continental terranes represented by the South Armenian Block (SAB) and the Tauride–Anatolide Platform (TAP), (2) scattered outcrops of Mesozoic ophiolites, obducted during the Upper Cretaceous times, marking the northern Neotethys suture, and (3) the Eurasian plate, represented by the Eastern Pontides and the Somkheto-Karabagh Arc. At several locations along the northern Neotethyan suture, slivers of preserved unmetamorphozed relics of now-disappeared Northern Neotethys oceanic domain (ophiolite bodies) are obducted over the northern edge of the passive SAB and TAP margins to the south. There is evidence for thrusting of the suture zone ophiolites towards the north; however, we ascribe this to retro-thrusting and accretion onto the active Eurasian margin during the latter stages of obduction. Geodynamic reconstructions of the Lesser Caucasus feature two north dipping subduction zones: (1) one under the Eurasian margin and (2) farther south, an intra-oceanic subduction leading to ophiolite emplacement above the northern margin of SAB. We extend our model for the Lesser Caucasus to NE Anatolia by proposing that the ophiolites of these zones originate from the same oceanic domain, emplaced during a common obduction event. This would correspond to the obduction of non-metamorphic oceanic domain along a lateral distance of more than 500?km and overthrust up to 80?km of passive continental margin. We infer that the missing volcanic arc, formed above the intra-oceanic subduction, was dragged under the obducting ophiolite through scaling by faulting and tectonic erosion. In this scenario part of the blueschists of Stepanavan, the garnet amphibolites of Amasia and the metamorphic arc complex of Erzincan correspond to this missing volcanic arc. Distal outcrops of this exceptional object were preserved from latter collision, concentrated along the suture zones.     

Effects of multi-annual climate variability on the hydrodynamic evolution (1833 to present) in a shallow aquifer system in northern Belgium

Abstract

Using a groundwater flow model and long historical meteorological time series data, the evolution of the groundwater flow regime in a multi-layered groundwater flow basin in northern Belgium during the last one and a half centuries (since 1833) is reconstructed. Model output parameters such as piezometric levels, depth to water table, seepage fluxes in the valleys and calculated baseflow to the river system are presented and inter-annual and decadal variations are evaluated against seasonal fluctuations. The main time-varying boundary condition in the model is the aquifer recharge which was estimated using the method of Thornthwaite and Mather based on precipitation and temperature data. The model does not take into account changes in boundary conditions due to changes in land use (deforestation, drainage of cultivated land) or groundwater exploitation. Variations in model output parameters are therefore only due to climatological forcing. Only the natural non-exploited state of the aquifer is considered. Although few historical piezometric measurements are available to verify model output, the results give an indication of the natural hydrodynamic variations on a time scale of decades.

Citation Van Camp, M., Coetsiers, M., Martens, K. & Walraevens, K. (2010) Effects of multi-annual climate variability on the hydrodynamic evolution (1833 to present) in a shallow aquifer system in northern Belgium. Hydrol. Sci. J. 55(5), 763–779.     

Evaluating model performance: towards a non-parametric variant of the Kling-Gupta efficiency

ABSTRACT

Goodness-of-fit measures are important for an objective evaluation of runoff model performance. The Kling-Gupta efficiency (R_KG), which has been introduced as an improvement of the widely used Nash-Sutcliffe efficiency, considers different types of model errors, namely the error in the mean, the variability, and the dynamics. The calculation of R_KG is implicitly based on the assumptions of data linearity, data normality, and the absence of outliers. In this study, we propose a modification of R_KG as an efficiency measure comprising non-parametric components, i.e. the Spearman rank correlation and the normalized flow–duration curve. The performances of model simulations for 100 catchments using the new measure were compared to those obtained using R_KG based on a number of statistical metrics and hydrological signatures. The new measure resulted overall in better or comparable model performances, and thus it was concluded that efficiency measures with non-parametric components provide a suitable alternative to commonly used measures.     

A strategy for producing refined currents in the Equatorial Atlantic in the context of the search of the AF447 wreckage

On the night of 1st June 2009, a Rio-Paris Air France flight (AF447) disappeared in a highly variable and poorly observed part of the western tropical Atlantic Ocean. The first debris was located 5 days after the accident. Several reverse drift computations were conducted in order to define the likely position of the wreckage. Unfortunately, the performance of the operational ocean analyses available in the region of interest ranges from 80 to 100 km of positioning error after 5 days of inverse drift computation. In preparation of the third phase of research of the wreckage at sea, a series of numerical experiments was performed at Météo-France and Mercator Océan in an attempt to better compute the surface currents in the region and for the period of the accident of the AF447 (May and June 2009). Tailored high-resolution atmosphere and ocean reanalyses were first produced respectively at Météo-France and Mercator Océan. Several nested experiments were then performed with a small and flexible ocean model limited to the region of interest. The date of the initial conditions and the type of atmospheric forcing fields were varied in order to produce a small ensemble from which information on the sensitivity to these changes could be derived. Probabilistic and statistical combinations between model and observations were tested and a solution was finally selected by means of a comparison of drift computations with independent surface drift observations.     

SMOS reveals the signature of Indian Ocean Dipole events

The tropical Indian Ocean experiences an interannual mode of climatic variability, known as the Indian Ocean Dipole (IOD). The signature of this variability in ocean salinity is hypothesized based on modeling and assimilation studies, on account of scanty observations. Soil Moisture and Ocean Salinity (SMOS) satellite has been designed to take up the challenge of sea surface salinity remote sensing. We show that SMOS data can be used to infer the pattern of salinity variability linked with the IOD events. The core of maximum variability is located in the central tropical basin, south of the equator. This region is anomalously salty during the 2010 negative IOD event, and anomalously fresh during the 2011 positive IOD event. The peak-to-peak anomaly exceeds one salinity unit, between late 2010 and late 2011. In conjunction with other observational datasets, SMOS data allow us to draw the salt budget of the area. It turns out that the horizontal advection is the main driver of salinity anomalies. This finding is confirmed by the analysis of the outputs of a numerical model. This study shows that the advent of SMOS makes it feasible the quantitative assessment of the mechanisms of ocean surface salinity variability in the tropical basins, at interannual timescales.     

Doppler weather radar as a meteorite recovery tool

Abstract– We report the use of Doppler weather radar as a tool for locating meteorites, both at the time of a fall and from archived radar data. This asset is especially useful for meteorite recovery as it can provide information on the whereabouts of falling meteorites in “dark flight” portion of their descent where information on their flight paths cannot be discerned from more traditional meteorite location techniques such as eyewitness accounts. Weather radar data can provide information from detection in three distinct regimes: (A) direct detection of the rapidly moving, optically bright fireball by distant radars, (B) detection of falling debris to include hand‐sample sized rocks, and (C) detection of dust produced by detonation events that can occur tens of minutes and many kilometers laterally removed from the actual fireball locality. We present examples of each, as well as comparisons against man‐made debris from a re‐entering Soyuz rocket and the Stardust Sample Return Capsule. The use of Doppler weather radar as a supplement to traditional meteorite recovery methods holds the promise of improving both the speed and total number of meteorite recoveries, thereby increasing the number of freshly fallen meteorites for scientific study.