Process oriented use of geostatistics to analyse creeping para‐glacial features

Complex para‐glacial systems may show signs of destabilization leading to frequent and potentially hazardous debris‐flows. Understanding creeping permafrost displacement over a period of time is therefore crucial for hazard management and risks assessment. This paper presents our methodology for estimating creeping permafrost displacement based upon data derived from various survey methods and demonstrates its relevance on the Glacier Bonnard system in southern Switzerland. Geostatistical processing allowed estimation of the displacement intensity over the area of interest, as well as assessment of the interpolation quality. Although the local measurement network needs to be refined, the results largely improve the understanding of the Bonnard para‐glacial system, though highlighting the need to locally refine the measurement network. In the present case, the destabilized front advances at ~1 m/a and the upstream creeping part at ~0.4 m/a. Variance analysis also provide objective thresholds that could be used to distinguish underlying physical processes. Copyright © 2015 John Wiley & Sons, Ltd.     

Where do fishmeal and fish oil products come from? An analysis of the conversion ratios in the global fishmeal industry

As a result of the stagnation of commercial fishery landings, aquaculture activities are expected to increase over the next decades to match the growing demand for marine protein. Overall, it is expected that the aquaculture sector could reduce some of the fishing pressure applied to wild stocks. However, this development is likely to be limited by the availability of key aquaculture inputs, specifically fishmeal and fish oil products (FMFOP). Aquaculture provided 60 % (fish meal) and 80 % (fish oil) of the world total consumption of these products in 2007. FMFOP are generally derived from small pelagic fish species, but can also be derived from other sources. Identifying the origin of FMFOP is crucial to understanding the effects of this new pressure on marine social-ecological systems. Two factors are of particular importance in the reduction sector transforming wild fish into fishmeal or fish oil: the two “conversion ratios” (i.e. the ratio between the quantity of wild fish harvested and the resulting quantity of FMFOP, and the ratio between the quantity of FMFOP and aquaculture production), and the type of raw material used by the reduction sector. Based on trade and production databases from FAO and the International Fishmeal and Fish oil Organisation (IFFO), this paper proposes an approach to identify the origin of FMFOP. It shows that whereas different countries use different pelagic resources to produce FMFOP, other countries use non-pelagic sources, and some countries use pelagic resources for human consumption.     

Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel,West Africa

Rapid population growth in sub-Saharan West Africa and related cropland expansion were shown in some places to have increased focused recharge through ponds, raising the water table. To estimate changes in diffuse recharge, the water content and matric potential were monitored during 2009 and 2010, and modeling was performed using the Hydrus-1D code for two field sites in southwest Niger: (1) fallow land and (2) rainfed millet cropland. Monitoring results of the upper 10 m showed increased water content and matric potential to greater depth under rainfed cropland (>2.5 m) than under fallow land (≤1.0 m). Model simulations indicate that conversion from fallow land to rainfed cropland (1) increases vadose-zone water storage and (2) should increase drainage flux (～25 mm year^?1) at 10-m depth after a 30–60 year lag. Therefore, observed regional increases in groundwater storage may increasingly result from diffuse recharge, which could compensate, at least in part, groundwater withdrawal due to observed expansion in irrigated surfaces; and hence, contribute to mitigate food crises in the Sahel.     

Further developments of a transient Poisson-cluster model for rainfall

Stochastic point processes for rainfall are known to be able to preserve the temporal variability of rainfall on several levels of aggregation (e.g. hourly, daily), especially when the cluster approach is used. One major assumption in most of the applications todate is the stationarity of the rainfall properties in time, which must be reconsidered under a climate change hypothesis. Here, we propose new theoretical developments of a Poisson-based model with cluster, namely the Neyman–Scott Rectangular Pulses Model, which treats storm frequency as a nonstationary function. In this paper, storm frequency is modelled as a linear function of time in order to reproduce an increase (or decrease) of the mean annual precipitation. The basic theory is reconsidered and the moments are derived up to the third order. Then, a calibration method based on the generalized method of moments is proposed and discussed. An application to a rainfall time series from Uccle illustrates how this model can reproduce a trend for the average rainfall. This work opens new avenues for future developments on transient stochastic rainfall models and highlights the major challenges linked to this approach.     

Preferred orientation distribution of shock‐induced planar microstructures in quartz and feldspar

Shocked quartz and feldspar grains commonly exhibit planar microstructures, such as planar fractures, planar deformation features, and possibly microtwins, which are considered to have formed by shock metamorphism. Their orientation and frequency are typically reported to be randomly distributed across a sample. The goal of this study is to investigate whether such microstructures are completely random within a given sample, or whether their orientation might also retain information on the direction of the local shock wave propagation. For this work, we selected samples of shatter cones, which were cut normal to the striated surface and the striation direction, from three impact structures (Keurusselkä, Finland, and Charlevoix and Manicouagan, Canada). These samples show different stages of pre‐impact tectonic deformation. Additionally, we investigated several shocked granite samples, selected at different depths along the drill core recovered during the joint IODP‐ICDP Chicxulub Expedition 364 (Mexico). In this case, thin sections were cut along two orthogonal directions, one parallel and one normal to the drill core axis. All the results refer to optical microscopy and universal‐stage analyses performed on petrographic thin sections. Our results show that such shock‐related microstructures do have a preferred orientation, but also that relating their orientation with the possible shock wave propagation is quite challenging and potentially impossible. This is largely due to the lack of dedicated experiments to provide a key to interpret the observed preferred orientation and to the lack of information on postimpact orientation modifications, especially in the case of the drill core samples.     

Plio-Quaternary extension in the Venezuelan Andes: Mapping from SAR JERS imagery

The geometry of extensional structures is described for the first time in the active setting of the Venezuelan Andes using remote sensing imagery. We favored the use of a mosaic of Synthetic Aperture Radar (SAR) scenes of the Japanese Earth Resources Satellite-1 (JERS-1) assisted by complementary remote sensing devices (Landsat TM, digital elevation models) and field observations to make a structural analysis at regional scale. Radar images are particularly efficient in the Venezuelan Andes where dense vegetation and frequent cloud covering earlier lent difficulties to remote sensing studies. We focused our analysis in the Valera–Rio Momboy and Bocono faults corner and in the Mucujun area. We show that, in an area where ongoing compression and strike–slip deformations occur, brittle extension can be detected independently from previous knowledge. Extensional structures correspond to elongated tilted blocks with dimension less than 10 km in width. Blocks are bounded by curved faults in plan view, the concavity being turned towards the axial part of the belt. The geometry and kinematics of such structures suggest that syn-orogenic extension started together with initiation of right-lateral strike–slip motion along the Bocono Fault in the Plio-Quaternary.     

Stochastic tracking of mesoscale convective systems: evaluation in the West African Sahel

In this work we apply a recently proposed Bayesian multiple target tracking model to mesoscale convective systems tracking. This stochastic model follows the multiple hypothesis tracking paradigm and can handle a varying number of targets while detecting the target birth, death, split, and merge events. The model is tested experimentally with real MCS targets detected from meteosat IR data over the Sahelian region. The performance of the stochastic tracking is evaluated by comparing it qualitatively and quantitatively with well established deterministic methods.     

Contribution of {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} and 13CTDIC Evaluation to the Identification of CO2 Sources in Volcanic Groundwater Systems: Influence of Hydrometeorological Conditions and Lava Flow Morphologies—Application to the Argnat Basin (Chaîne des Puys, Massif Central, France)

Mineralization of groundwater in volcanic aquifers is partly acquired through silicates weathering. This alteration depends on the dissolution of atmospheric, biogenic, or mantellic gaseous CO₂ whose contributions may depend on substratum geology, surface features, and lava flow hydrological functionings. Investigations of $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ¹³C_TDIC (total dissolved inorganic carbon) on various spatiotemporal scales in the unsaturated and saturated zones of volcanic flows of the Argnat basin (French Massif Central) have been carried out to identify the carbon sources in the system. Mantellic sources are related to faults promoting CO₂ uplift from the mantle to the saturated zone. The contribution of this source is counterbalanced by infiltration of water through the unsaturated zone, accompanied by dissolution of soil CO₂ or even atmospheric CO₂ during cold periods. Monitoring and modeling of δ¹³C_TDIC in the unsaturated zone shows that both $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ¹³C_TDIC are controlled by air temperature which influences soil respiration and soil-atmosphere CO₂ exchanges. The internal geometry of volcanic lava flows controls water patterns from the unsaturated zone to saturated zone and thus may explain δ¹³C heterogeneity in the saturated zone at the basin scale.