bluuebunny/crossref_metadata_2025 huggingface dataset:
Agricultural colonization of dynamic riverine islands in a tropical wandering river
Authors: Serrao Livia , Balcázar Terrones Luz Elita , Huamaní Yupanqui Hugo Alfredo , Rengifo Trigozo Juan Pablo , Zolezzi Guido
Published: March 2020

We investigate the interplay between riverine islands dynamics in a large tropical wandering river and their use by local communities for agricultural production. The study focuses on a piedmont reach of the Huallaga river, which drains the Peruvian Amazon. Riverine islands are characterized by a high space-time variability in active wandering river systems like the Huallaga, which results from biophysical interactions among flow, sediment transport and riparian vegetation. Despite the rapid rates of planform changes, islands in the Huallaga are extensively used by local farmers who mainly rely on rainfed, low tech agriculture. Thanks to the high nutrient availability in their soil, dynamic riverine islands are offering a natural solution to the advancing degradation of soils due to the progressive increase of intensive monoculture in nearby floodplain areas. The possibility of using intact fields, rich in organic matter, pushes the local populations to colonize riverine islands, challenging their dynamism and high erosion. Through a combination of participatory surveys, field measurements and remote sensing analysis of the recent (30 years) reach-scale island dynamics we investigate whether the benefits of cropping in a riverine island are more relevant than the damages related to their intense morpho-dynamics. Challenges to such biophysical-social system are posed by planned and ongoing infrastructural development in the catchment, affecting the flow and sediment supply regimes.
Temperature scaling of convective cells in present and future conditions
Authors: Purr Christopher , Brisson Erwan , Ahrens Bodo
Published: March 2020

Convection permitting climate models (CPMs) agree on an increase in short-term, extreme precipitation in the future. However, different studies using CPM simulations found regionally varying temperature scaling rates of hourly extreme precipitation either close to or above the Clausius-Clapeyron-rate (CC-rate) of 7%/K. These variations suggest that the dynamics of convective events strongly regulate the local scaling rates. In order to understand how the characteristics of convective events change in the future, we apply a tracking algorithm to precipitation data with 5-min temporal resolution from a regional climate model (COSMO-CLM) simulation. The model is run over central Europe at a grid size of 0.025° for an evaluation period (1981-2015) driven by ERA-Interim reanalysis data, as well as a present-day (1976-2005) and a future (2071-2100) period driven by the EC-Earth global model. We investigate the temperature scaling of convective cell characteristics like total precipitation per cell, mean area, lifetime and maximum intensity, as well as changes in the diurnal cycle of convective cells which might explain the overall scaling rates. The cell characteristics precipitation sum, mean area and maximum intensity show an exponential increase with temperature across most of the temperature range with a drop-off at high temperatures very similar to fixed location scaling curves. While the maximum intensity and area scale at rates close to the CC-rate, the precipitation sum scales at a rate close to twice the CC-rate. In contrast to this, the lifetime of convective cells does not increase with temperature but stays constant with a drop-off at high temperatures. The future simulation shows a shift of the scaling curves towards higher peak values at higher temperatures. Convective activity is projected to decrease during daytime and increase during nighttime. While the mean intensity of convective cells increases throughout the whole day, the number of cells is reduced during the afternoon peak and increased during nighttime. This leads to a slight reduction of convective precipitation during daytime and almost a doubling of convective precipitation during nighttime.
A process model to predict the faith of clusters in CI-APi-TOF mass spectrometers
Authors: Neefjes Ivo , Zanca Tommaso , Kubecka Jakub , Zapadinsky Evgeni , Passananti Monica , Kurtén Theo , Vehkamäki Hanna
Published: March 2020

Recent technological developments have made it possible to detect the elemental composition of even the smallest airborne clusters at low ambient concentrations through chemical ionization atmospheric pressure interface time-of-flight mass spectrometry (CI-APi-TOF-MS). The charging process and collisions inside the instrument will however affect the molecular composition of the original sample clusters. A process model is therefore needed to connect the mass spectra to the original molecular clusters in the measured sample.

 

Our research has been focused on developing this process model for clusters involving highly oxygenated organic molecules (HOM) with molecular formula C10H16O8. This elemental composition corresponds to one of the most common mass peaks observed in experiments on ozone-initiated autoxidation of α-pinene.

 

For the model, two situations inside the mass spectrometer have to be taken into account: the chemical ionization and collisions with carrier gas inside the atmospheric pressure interface. Recently, a model predicting the fragmentation of clusters as a result of collisions in APi has been developed by Zapadinsky et al. (2018). We used this model to perform numerical simulations of fragmentation in the APi on our selected clusters. The results show that fragmentation is highly unlikely for the considered clusters, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.

 

Current research is focused on developing a model for the charging process inside CI-APi-TOF MS. Configurational sampling is combined with high quality quantum chemistry calculations to derive the binding energies and evaporation rates of the studied clusters. This model should eventually connect the ionized clusters after charging to the original distribution of neutral clusters in the measured sample.
An approach to organize loss data related to geo-hydrological hazards
Authors: Salvati Paola , Marchesini Ivan , Vennari Carmela , Donnini Marco , Bianchi Cinzia , Sarretta Alessandro , Casarano Domenico
Published: March 2020

Most commonly, geo-hydrological hazards (i.e., landslide, flood, sinkhole) occur in response to a single trigger like an intense rainfall event, a prolonged rainfall period, a rapid snowmelt event, an earthquake. Multiple damaging processes (phenomena) occurring in response to a single trigger can cause a cumulative socio-economic impact, which is often difficult to quantify and to attribute to each single damaging processes (landslide, or a group of landslides, or a single inundation). As a consequence, after a geo-hydrological disaster occurs, media, insurance companies and international institutions publish numerous assessments of the cost of the disaster based on different methodologies and approaches, often reaching different results. At European level, EC Directives related to natural hazards prove standards for the collection of data focusing their attention mainly on codifying the processes, their attributes and their spatial extent, leaving out the important issue of rigorously classifying the damaged elements and the loss data. Lack of standards contributes negatively to the paucity of damage information and cost data, fundamental for the successive ex-post analysis aimed at quantitatively risk evaluation. In Italy, despite the frequency of the significant socio-economic impacts due to geo-hydrological hazards, few attempts have been made to estimate the economic cost of geo-hydrological hazards. These loss estimations are mainly based on cost components of the public budget for post-event restorations and reimbursements, hampering the possibility to distinguish between the private and public sector losses. The loss estimates do not distinguish the costs (i) by type of processes (landslides, flash floods, floods and other damaging events) responsible for the damage, and (ii) by expenditure items (restoration actions or mitigation activities). LAND-deFeND, a recently developed database structure, represents an effort to manage all the issues that can arise when storing, organizing and analysing information on losses related to geo-hydrological hazards with different levels of accuracy and at different geographical scales, from the national to the local scale.
Establishing a 3D model for the Rhine-Ruhr region based on the geology and property distribution.
Authors: Gonzalez de Lucio Gabriela de los Angeles , Balcewicz Martin , Saenger Erik H.
Published: March 2020

The Rhine-Ruhr region is located in the state of North Rhine-Westphalia (NRW) in western Germany. Due to the transition from coal to low-carbon heat sources, potential locations in NRW must be explored regarding to their geothermal potential. The Bavarian area has shown for the last 20 years, that deep geothermal energy is both feasible and economical in Germany. Compared to the mentioned Molasse basin in south Germany, the geological setting is much more complex in the Rhine-Ruhr region. Based on a typical geothermal gradient of 30 °C/km, the optimal depth of a reservoir should be between 3000 m to 5000 m. In this depth, carbonate layers from Devonian times were identified in NRW. Due to the lack of accessibility, minor reservoir characterization was done, yet. Therefore, a geological model which reflects local lithological properties is essential for further geothermal projects. The model of the Rhine-Ruhr region is based on field surveys, top formations, geological sections and maps, respectively. The geometrical model is supplemented by rock properties, like density, porosity, and P- respectively S-wave velocities. These properties are derived from well logs, laboratory measurements and literature, transferring the derived properties to the grid require an analysis of upscaling techniques and distribution of such properties in the model. The result is a heterogeneous model representing the geological structure and rock property distribution of the Rhine-Ruhr region. Representative lithological units like Ruhrsandstone or interbedded coal, clay, and sandstone strata are also implemented as dominant fracture orientations. In this work we are considering several parameters to find a balance between the resolution of the model, property scaling and computational efficiency. One key aspect is that geological models are built with irregular grids while for our wave propagation simulations a regular and cartesian grid with equal grid spacing is required. Of course, such regular grids can be used for several modelling techniques and can be used as a basis for different studies. Overall goal is to evaluate local geological models to assess the feasibility of geothermal projects in the area.
Review on the formation and geochemistry of the mega crystals of Naica, México.
Authors: Gutiérrez Gutiérrez Ana Laura , Puy y Alquiza Maria de Jesus , Kshirsagar Pooja
Published: March 2020

In the state of Chihuahua, Mexico, a mine located in Naica is one of the most important Pb and Zn deposits in the world.  The region manifests several caves with varities of gypsum crystals (Ca4 H2O) known as selenite (the largest in the world so far, specimens up to eleven meters in length and one meter in thickness). The present abstract discusses the formation mechanism of these gigantic crystals. The review is based on the interpretations made by early workers (which includes one doctorate thesis and two Bulletins).

The interpretations were made on 19 samples of anhydrites that were collected at a depth of -345 meters. At this depth the early workers also found microscopically alternating dark dolomite and light bands of anhydrite. The dolomite-anhydrite association is generally associated with mineral recrystallization events. With the geological review carried out, two sources of sulfates were identified: one is La Virgen Formation and the second in the stratiform anhydrite of the Aurora Formation. Formation of hydrothermal anhydrite during the last stage of mineralization has been attributed to the formation of selenite mega crystals due to its dissolution. Hydrothermal minerals, such as hydrothermal anhydrite and sulphides. The most common sulfides in mineralization are galena, sphalerite, to a greater extent, pyrite and chalcopyrite. In case of weathering of these, they would generate their oxidation and result in the presence of sulfate.

According to the early workers the anhydrite was available in the late hydrothermal stage after mineralization of the mineral. The temperature during the growth of the crystals was maintained slightly below 58 ° C, the value in the solubility of the anhydrite is equal to that of the plaster. Giant selenite crystals grew from low salinity solutions with isotopic compositions compatible with the crystals formed by dissolving the anhydrite found in the mine. The kinetics of gypsum nucleation implies induction times longer than 1 m.y. for the typical temperature (54 ° C) and ~ 1 k.y. for low temperature episodes (up to 47 ° C). This mechanism provides a super saturation level that is not only small and maintained over time but is also virtually free of fluctuations (even small amplitudes).

Recent contributions have speculated that there are other caves with similar selenite or even with larger crystals exist among the tangle of underground galleries in the area of ​​the Naica mine.
Random Walks through Climate Networks: Sea Ice Prediction with Bayesian Inference
Authors: Gregory William , Tsamados Michel , Stroeve Julienne , Sollich Peter
Published: March 2020

Spatial predictions of the Arctic sea ice cover are becoming of paramount importance for Arctic communities and industry stakeholders. However, with sea ice variability likely to increase under continued anthropogenic warming, increasingly complex tools are required in order to make accurate forecasts. In this study, predictions of both Arctic and Antarctic summer sea ice extents are made using a complex network statistical approach. This method exploits statistical relationships within geo-spatial time series data in order to construct regions of spatio-temporal homogeneity -- nodes, and subsequently derive teleconnection links between them. The nodes and links of the networks here are generated from monthly sea ice concentration fields in June(November), July(December) and August(January) for Arctic(Antarctic) forecasts, hence lead times extend from 1 to 3 months. Network information is then utilised within a linear Gaussian Process Regression forecast model; a Bayesian inference technique. Network teleconnection weights are used to generate priors over functions in the form of a random walk covariance kernel; the hyperparameters of which are determined by the empirical Bayesian approach of type-II maximum likelihood. We also show predictions of all other months in order to ascertain the presence of a spring predictability barrier in observational data, for both hemispheres.
Sharp transition in modes of dynamic crack propagation in dry-snow slab avalanche release
Authors: Trottet Bertil , van Herwijnen Alec , Wang Stephanie , Jiang Chenfanfu , Teran Joseph , Gaume Johan
Published: March 2020

Dry-snow slab avalanche release can be separated in four distinct phases : (i) failure initiation in a weak snow layer buried below a cohesive snow slab, (ii) onset, (iii) dynamics of crack propagation in the weak layer and eventually (iv) slab release. While a lot has been done to study the first two phases, less is known about dynamic crack propagation and slab release, especially at slope scale. 

In this study, we used the Material Point Method and elastoplasticity to simulate the dynamics of 20 m long centered Propagation Saw Tests (PST). We improved the recent constitutive snow model of Gaume et al. (2018) by developing a new softening law based on the total plastic deformation (volumetric and deviatoric parts) to remove artifacts observed in failure modes.

Interestingly, several regimes of propagations are observed depending on slope angle Θ. For slope angles smaller than the friction angle (Θ < Φ), crack propagates faster in the downslope direction than upslope. The propagation speed increases with slope angle and appears closely related to the bending mechanism which sustains the propagation. For slope angles higher than the friction angle (Θ > Φ), a sharp transition is observed once the crack reaches a critical length lf. We interpret this transition as a change from slab bending to slab tension due to the increasing load in the downslope direction. An estimation of lf is proposed using a basic analytical shear model with residual friction similar to the one developped by McClung in 1979. In this case, the crack propagation speed seems to be mostly related to the P-wave speed in the slab. In this study, we explain the gap between propagation speeds based on 2 m PSTs and some observations of avalanche triggering. Finally, our results show the relevance of shear models which appear sufficient to describe slab avalanche release on steep terrain.
Urban sediment: a specific geochemical signature compared to natural sediments?
Authors: Zhan Qiufang , Chatain Vincent , Aubin Jean-Baptiste , Lipeme Kouyi Gislain , Gautier Mathieu , Winiarski Thierry , Delolme Cécile
Published: March 2020

Detention and infiltration basin has been increasingly implemented in France in order to provide additional storage of runoff from impervious surfaces due to rapid urbanization. These sustainable urban drainage systems also ensure quality of stormwater infiltrated into groundwater. In urban areas, these devices accumulate suspended particles eroded from city watershed and represent a geochemical signature of these urban watershed. Urban sediments are known to be polluted by high organic and inorganic substance contents, but their geochemical properties and specificities are insufficiently informed. The objective of this work is to study whether geochemical properties of urban sediment accumulated in detention and infiltration basins is distinguished from other natural sediments (from rivers, lake, marine environment). For this purpose, this study focused on relating watershed characteristics and physico-chemical properties of sediment using multivariate analyses based on rank data values. Data were notably collected from the national programs GESSOL (GEStion du patrimoine SOL, i.e. soil environmental functions - soil heritage management) and EC2CO (Ecosphère Continentale et Côtière, i.e. continental and coastal ecosphere) based on 19 infiltration basins around Lyon (France) and from literature (lake, basin, river etc.). Principal Component Analysis (PCA) was used to identify the most important sources of variation between trace metals and organic matters in different sediments. Cluster analysis was performed to group samples of similar sediment characteristics between major variables and trace metals contents. A significant amount of Fe (from 2.52 to 3.92 wt.%) and organic matters (from 18 to 27 wt.%) was found in the urban sediment. The results of PCA showed the influence of grain size on metal variability. Metals are more associated with the aluminosilicates (<63μm fraction), Fe and organic matters. Cluster analysis shows that Ti, Ni, Zn, Cd and Pb are originated from anthropogenic sources, especially discharged from commercial and industrial watershed. This work highlights the singularity of the urban sediment, as they are highly contaminated compared to natural sediments. Hence, the specific treatments are needed to tackle this problematic contamination.
Determinants of calcite flux in planktonic foraminifera on seasonal and interannual time scales
Authors: Kiss Peter , Jonkers Lukas , Hudáčková Natália , Turid Reuter Runa , Kučera Michal
Published: March 2020

Planktonic foraminifera precipitate calcareous shells, which after the death of the organisms are exported from the sea surface to the sea floor, where they are preserved on geologically relevant timescales. The export flux of planktonic foraminifera shells constitutes globally up to a half, and in the studied region off Cap Blanc (Atlantic Ocean) about one third, of the marine pelagic calcite flux. Given their importance for the marine calcite budget and for the pelagic carbonate counter pump, which counteracts the biological pump in terms of oceanic capacity for intake of CO2, it is crucial to gain an understanding of factors modulating the export flux of planktonic foraminifera calcite. In principle, variability in the export flux of planktonic foraminifera calcite could depend within one species on i) shell flux, ii) shell size and iii) calcification intensity, and where shell size and calcification intensity differ among species also on the species composition of the deposited assemblage. To assess the importance of these aspects in modulating the export flux of planktonic foraminifera calcite, we investigated two annual time series (from 1990-1991 and 2007-2008) from sediment traps moored in the Cap Blanc upwelling area. We assessed the predictability of foraminifera calcite flux variability on seasonal and interannual time scales, by determining the variability in species-specific shell fluxes, shell sizes and weights with bi-weekly resolution. We find a remarkable discrepancy in the contribution of the controlling factors between seasonal and interannual scales. On the seasonal time scale, 80% of the variability of the calcite flux is explained by shell flux. On the inter-annual time scale, on the other hand, variations in shell size and calcification intensity are key to explain the calcite flux, since the time series from 2007-2008 yielded 58% larger and 11% heavier specimens. These results imply that for the global estimate of planktonic foraminifera calcite flux, shell flux is likely the most relevant predictor. However, a prediction of the temporal evolution of the calcite flux will likely require estimates of changes in shell size and calcification intensity of the involved foraminifera species.
Testing a novel technique, geotubes with mycotechnosoil, to mitigate post-fire erosion and enhance ecosystem recovery
Authors: Serpa Dalila , J. Keizer Jan , I. Machado Ana , Santos Martha , R. F. Oliveira Bruna , Gholamahmadi Behrouz , Martins Martinho , González-Pelayo Oscar , Consortium Life-Reforest
Published: March 2020

Recently burnt areas have frequently been documented to produce strong to extreme catchment-scale hydrological and erosion responses to major rainfall events, even if these responses have rarely been quantified. These responses have raised important concerns, both among forest owners and managers on the on-site implications of soil (fertility) loss and among water resources managers for the off-side impacts on downstream values-at-risk such as road and hydraulic infrastructures, flood zones, and surface water quality in reservoirs or at river intake points. State-of-the-art emergency stabilization management, as practiced in the USA and Galicia, aims at reducing the hydrological and erosion response at its main source, i.e. the hillslopes. Based on years and decades of experience and pain-staking field monitoring in both the USA and Galicia, mulching is typically preferred over barrier-based methods, especially for being more effective in the case of high-intensity rainfall storms. Even so, the LIFE-REFOREST consortium (LIFE17 ENV/ES/000248) has developed an innovative barrier-based technique that is designed to be implemented easier and faster than log and shrub barriers and, at the same time, to improve vegetation recovery, using seeds of plant species that establish vegetation strips against runoff and erosion and/or seeds of tree and shrub species for re- or afforestation. The REFOREST barriers consists of geotubes containing, besides seeds, a mycotechnosoil as well as straw. The effectiveness of the LIFE-REFOREST geotubes is current being tested under field conditions in summer-2019 burnt areas in north-central Portugal and Galicia, in contrasting forest types (eucalypt vs. pine) on contrasting parent materials (schist vs. granite). Both field trials involve, besides 3 control plots and 3 plots with geotubes, also 3 plots mulched with either eucalypt logging residues or pine needles. The present poster will show preliminary results of the field trial in north-central Portugal, in a second-rotation eucalypt stand where tree crowns were scorched by the fire and soil burn severity was classified as moderate. These results concern the initial monitoring period till early spring 2020. However, this monitoring period has been quite rainy so far, arguably providing rather ideal conditions for testing the effectiveness of barrier-based solutions such as that of LIFE-REFOREST.
Assessing consistency across climate datasets for the potential detectability of extreme events in seasonal forecasting using agroclimatic indicators
Authors: Costa Saura Jose Maria , Bacciu Valentina , Mereu Valentina , Trabucco Antonio , Spano Donatella
Published: March 2020

Seasonal forecasts are medium-range climate predictions that, used for calculating agroclimatic indicators, might potentially help land managers for best decision making. To assess their reliability seasonal forecasts are commonly contrasted against observed datasets, e.g. gridded data coming from reanalysis, classifying yearly pixel conditions in into/out of the norm events (i.e. using the 33th and 66th percentiles along a time series to define the occurrence of out of the norm events). Potential differences in the shape of the probability distribution across observed climate datasets might influence the results in the validation procedure of seasonal forecasting since the definition of out of the norm events depends on the properties of the statistical distribution. Here, we assess for different agroclimatic indicators related with water availability, vegetation thermal needs and fire risk, the spatial patterns of skewness using a range of climate datasets, i.e. ERA5, E-OBS and WFDEI along a 30 year period. Skewness represents the degree of asymmetry of the probability distribution evidencing locations in which out of the norm events highly differ from mean conditions which might suggest a potentially higher detectability. Common spatial patterns of great skewness (either positive or negative) across observed dataset might suggest areas with high and consistent detectability whereas contrasting patterns might suggest higher uncertainty for the validation procedure.
Results of the IACS Debris-covered Glaciers Working Group melt model intercomparison
Authors: Pellicciotti Francesca , Fontrodona-Bach Adria , Rounce David , Nicholson Lindsey
Published: March 2020

Many mountain ranges across the globe support abundant debris-covered glaciers, and the proportion of glacierised area covered by debris is expected to increase under continuing negative mass balance. Within the activities of a newly established IACS Working Group (WG) on debris-covered glaciers, we have been carrying out an intercomparison of melt models for debris-covered ice, to identify the level of model complexity required to estimate sub-debris melt. This is a first necessary step to advance understanding of how debris impacts glacier response to climate at the local, regional, and global scale and accurately represent debris-covered glaciers in models of regional runoff and sea-level change projections.

We compare ice melt rates simulated by 15 models of different complexity, forced at the point scale using data from nine automatic weather stations in distinct climatic regimes across the globe. We include energy-balance models with a variety of structural choices and model components as well as a range of simplified approaches. Empirical models are run twice: with values from literature and after recalibration at the sites. We then calculate uncertainty bounds for all simulations by prescribing a range of plausible parameters and varying them in a Monte Carlo framework. We restrict the comparison to the melt season and exclude conditions as few current models have the capability to account for them.

Model results vary across sites considerably, with some sites where most models show a consistently good performance (e.g. in the Alps) which is also similar for energy-balance and empirical models, and sites where models diverge widely and the performance is overall poorer (e.g. in New Zealand and the Caucasus). It is also evident that with a few exceptions, most of the simpler, more empirical models have poor performance without recalibration. A few of the energy-balance models consistently give results different to the others, and we investigate structural differences, the impact of temporal resolution on the calculations (hourly versus daily) and the calculation of turbulent fluxes in particular.    

We provide a final assessment of model performance under different climate forcing, and evaluate models strengths and limitations against independent validation data from the same sites. We also provide suggestions for future model improvements and identify missing model components and crucial knowledge gaps and which require further attention by the debris-covered glacier community.
Representativeness of volume investigated by high-resolution X-ray computed tomography in damaged fine-grained rocks
Authors: Saur Hugo , Aubourg Charles , Moonen Peter , Sénéchal Pascale , Boiron Tiphaine , Derluyn Hannelore
Published: March 2020

We focus on calcareous homogenous shales featuring different degrees of damage along a km-long strain gradient, marked by cleavage development. In a previous study, we used high-resolution X-ray computed tomography (µCT) to document the evolution of the 3D fabric of the fine-grained shales along the strain gradient (Saur et al., JSG, 2020). Our conclusions were based on samples of ~ 2.5 mm3 containing over 10’000 quartz and calcite grains. The objective of the current study is to assess the representativeness of analyses on such small rock samples. To that extent, we first repeat the µCT analysis on multiple samples of the same, limited, volume and assess the variability of the results. These results are then compared to both macroscopic field observations and bulk fabric measurements obtained with AMS (Anisotropy of Magnetic Susceptibility) on larger samples (~ 10 cm3). AMS provides a statistical description of the magnetic susceptibility tensor, and particularly the confidence angle of axis orientation. Generally, this confidence angle is the result of matrix organization and rock magnetism. In this study, AMS is only controlled by the presence of illite particles which reflect the matrix organization. Finally, we perform a subvolume analysis on the µCT images to determine the smallest representative volume characterizing the fine-grained fabric. In light of these analyses we discuss the representativeness of investigated volume of fine grained shales, subjected to different degrees of deformation.
The Rance tidal power station: a preliminary study of its impact on tidal patterns and sediments dynamics in the Rance estuary (France) from 1957 to 2018
Authors: Rtimi Rajae , Sottolichio Aldo , Tassi Pablo
Published: March 2020

The Rance tidal power station (located on the Brittany coast of Northern France), was opened in 1966 as the world’s first and largest tidal power station, with peak output capacity of 240 Megawatts. It is currently the second world’s largest tidal power installation after the Sihwa Lake Tidal power station (South Korea). The power plant is located at the mouth of a small steep-sided ria, with a maximum perigean spring tidal range of 13.5 m and an average fluvial discharge of 7 m3/s. The dam is 750 m long and the tidal basin measures 22.5 km2. Despite a well-known effect of the plant on the damping of estuarine water levels, little attention has been given to the consequences of the dam in the estuarine environment in terms of hydrodynamics, for instance, the propagation of the tidal wave and tidal currents along the estuary are still little understood. Moreover, net siltation has been reported by several observations, but there is no specific knowledge on the role of the plant on sedimentation. In this study, we analyze the impact of the tidal power station on tidal wave patterns and sediment dynamics in this particular man-engineered system. To this goal, a numerical model based on a two-dimensional depth-averaged approach is implemented to predict the tide propagation and tidal currents along the estuary accounting for the presence of the tidal power station. Three modelling scenarios were performed: the first considering the bathymetry of 1957 (before the plant’s construction), a second scenario considering the bathymetry of 2018 without the presence of the power station and a third scenario considering the bathymetry of 2018 with the power station. Preliminary results showed that, with and without the tidal power station, the upper estuary exhibits a flood dominant behavior, with longer duration of falling water than rising water, and conversely the lower estuary is ebb dominant with shorter duration of falling water than rising water. This analysis also revealed that the tidal power station might switch the flood dominance in the central estuary to ebb dominance. These findings imply a net seaward transport of both coarse and fine sediments in the lower estuary. Therefore, the tidal power station might have a considerable role in modulating the estuarine turbidity maximum and channels’ morphology. Finally, these results are compared with preliminary numerical simulations of suspended sediment transport to further quantify the impact of the tidal power plant on the dynamics of the estuarine turbidity maximum.
I’ll be dead by the time it happens: Children’s Perceptions of Climate Change in the Mekong Delta, Vietnam
Authors: Halstead Florence , Parsons Dan , Jones Lisa , Hackney Chris
Published: March 2020

The Mekong Delta in Southern Vietnam is one of the most at risk places globally to the effects of climate change and sea level rise, specifically in terms of flooding. It is predicted to change drastically over the next 100 years, with additional human-driven actions (such as sand mining and groundwater extraction) expected to exasperate the speed and severity of said change. Understanding the existing perceptions of those that will face these future challenges, and what contributes to forming those perceptions, is a critical underpinning required for the success of any future resilience and mitigation initiatives. A holistic view that takes account of these varying influences on societal perceptions, resilience and education needs to be taken. 

One of the most vulnerable groups to the consequences of climate change, and indeed the citizens that will go on to tackle the majority of challenges we are predicted to face in the future, is children. For this reason alone, ascertaining their perceptions and understandings, along with the influences and sources that shape their views, is paramount.

This paper will present the findings from a project that explored local children’s perceptions of climate change in the heart of the Mekong Delta. Creative and arts-based methods enabled children’s voices to be heard. Combined with further policy analysis and interviews with parents, teachers and government officials, these voices have been further contextualised within their socio-cultural context and environment. Through developing an understanding of these perceptions and the influencing factors, a more effective and holistic approach to shaping children’s climate change resilience can be executed, which will ultimately enhance a society’s ability to adapt to and mitigate the impacts of climate change into the future. 

 

 
The response of the Brewer Dobson circulation to a quadruple CO2 increase in WACCM
Authors: Calvo Natalia , Marsh Daniel R. , Garcia Rolando R. , Chiodo Gabriel , Polvani Lorenzo
Published: March 2020

The Brewer-Dobson circulation is the mean meridional circulation in the stratosphere. It is important for the chemical distribution of trace gases in the stratosphere and its thermal structure. Chemistry climate models consistently project an acceleration of its shallow branch in response to increasing greenhouse gas concentrations, while changes in the deep branch have been much less explored. Most models agree that enhanced resolved wave forcing is the main driver of the trend in tropical upwelling in the lower stratosphere although the ultimate mechanism is not well understood. Both changes in wave generation and wave dissipation related to climate change can lead to increased wave driving and modeling results are not conclusive.

Here, we revisit this issue based on the timescales of the BDC response to an abrupt quadrupling of CO2 concentrations. We analyze CMIP5 and CMIP6 preindustrial, 4xCO2 and AMIP simulations of the Whole Atmosphere Community Climate Model (WACCM) to compare the fast and slow responses of the BDC to the increase in CO2. While the fast response is associated with the direct radiative forcing of increasing CO2, the slow response of the BDC is related to warmer sea surface temperatures. Our results show that the shallow branch is tightly coupled to the evolution of tropical surface temperature. About half of the response to an abrupt 4xCO2 increase occurs in the first 10 years in WACCM. In the deep branch, about half of the response of the tropical upwelling in the deep branch is due to warmer SSTs, the other half is radiatively-driven. The waves involved in driving these changes are also investigated together with possible mechanisms.
Drivers of Degradation: Linking Large-scale Degradation to Human Influence in the Nigerian Guinea Savannah
Authors: Adenle Ademola. A , Ifejika Speranza Chinwe
Published: March 2020

The Nigerian Guinea Savannah is the largest agro-ecological belt, encompassing about 49% of Nigeria, and is one of the most diverse, fragile and threatened ecosystems in the country.  Land degradation in the zone is a serious challenge driven by deforestation, agriculture and other livelihood needs. Yet the link between land degradation and unsustainable human influence is widely acknowledged but spatially under explored. The study thus examined the spatial relation of human influence with land degradation in order to inform better land use management. We updated the Human Influence Index by combining the following spatial layers, namely: (1) distance to a major city; (2) land use/land cover; (3) human population density; (4) distance to major roads; (5) distance to railways; and (6) navigable waterways. We then overlaid the Human Influence Index with MODIS-derived land degradation status in order to explain the level of human influence on land degradation. In total, 38% of the Nigerian Guinea Savannah land area are becoming more degraded, while 14% and 48% of the remaining area show either improvement or no change, respectively. However, spatial proximity of human activities was observed to influence land degradation, but with more degradation occurring in areas of low population density. This shows that the spatial pattern of Human Influence Index data cannot completely explain land degradation in the zone. We thus present a more holistic approach to identifying human influence on land degradation in the Nigerian Guinea Savannah.  
Impact of earthquakes and its dependence on magnitude: testing the Greek seismicity
Authors: Triantafyllou Ioanna , Papadopoulos Gerassimos , Lekkas Efthimios
Published: March 2020

Strong earthquakes cause significant impact on both the built and natural environment. Impact databases are of fundamental importance for seismic risk assessment in a region. Such data include human and property losses as well as secondary effects including ground failures and tsunamis. The earthquake impact, EI, depends on many factors, one of the most important being the earthquake magnitude, M. To test the dependence of EI on M we selected the Greek seismicity which is the highest in the Mediterranean region with record of earthquakes since the antiquity. Although various descriptive and parametric earthquake catalogues as well as inventories of intensity observation points are available for Greece no database for EI has been organized so far. For a first time we organized a Greek Earthquake Impact Database (GEID) which covers the time interval from 1800 to 2019 and includes earthquake parameters and three main quantitative impact elements: building damage, fatalities and injuries. Data on tsunami impact are also included in the GEID. A long number of sources have been utilized, some of them remaining unknown so far in the seismological community. To select the most appropriate magnitude for each earthquake event occurring in the instrumental period of seismology, i.e. from 1900 onwards, we compared the catalogues produced by the ISC-GEM and by three academic institutions. After completeness testing and examination for magnitude homogeneity we performed magnitude closeness analysis and produced formulas for magnitude conversion from one catalogue to another. For the 19th century earthquakes we again compared various catalogues, collected new data from documentary sources and compiled a new catalogue by re-calculating macroseismic magnitudes equivalent to Mw from intensity/M relations developed for Greek earthquakes of the instrumental period. We found that for single earthquake events the level of impact generally depends on magnitude but this is not valid for offshore events. However, the time distribution of the three impact elements over the period examined showed a relative decrease of the totally collapsed buildings which implied drastic decrease of the fatality rate but not of the injuries rate. This is attributed to the gradual improvement of the building construction particularly after the enforcement of antiseismic building codes in the country. Τhe first author was supported by the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no. 490).
Elastic geothermobarometry on multiple inclusions in a single host
Authors: Gilio Mattia , Alvaro Matteo , Angel Ross , Scambelluri Marco
Published: March 2020

The characterization of the pressure and temperature (P-T) histories of subducted rocks is of key importance to unravel geological processes at all scales. Conventional element-exchange geothermobarometers are challenged in ultra-high-pressure metamorphic terranes as the subduction temperatures may exceed their closure temperature and minerals may undergo re-equilibration along their path. Elastic geobarometry applied to host-inclusion systems is a complementary method to determine P and T conditions of metamorphism that does not rely upon chemical equilibrium. Recent development of elastic geobarometry (Angel et al., 2019; Campomenosi et al., 2018; Murri et al., 2018) allows us to retrieve entrapment pressures for host-inclusion pairs from the residual strains acting on the inclusion. Because only a single measurement, the inclusion strain, is made, only a line in PT space of possible entrapment conditions, the entrapment isomeke, can be determined. Thus, the entrapment pressure along an isomeke can only be determined if the entrapment temperature is known.

An alternative is to calculate entrapment conditions for two types of inclusions that are believed, from petrological evidence, to have been entrapped at the same time. In this study we performed micro-Raman measurements on quartz and zircon inclusions trapped in garnets from a garnet-kyanite gneiss and a quartz-garnet vein from the Fjørtoft UHP terrane, Norway. From the micro-Raman data, using the program stRAinMAN (Angel et al., 2019), we calculated the strains at room conditions (Murri et al., 2018) and thus the entrapment conditions. The intersection between the two sets of isomeke calculated on multiple quartz and zircon inclusions demonstrates that measuring different inclusion phases trapped inside a single host allows unique P-T conditions for the host rock to be determined.

This work was supported by ERC-StG TRUE DEPTHS grant (number 714936) to M. Alvaro

Angel R.J., Murri M., Mihailova B. & Alvaro M. (2019) - Stress, strain and Raman shifts. Zeitschrift für KristallographieCrystalline Materials, 234(2), 129-140.

Campomenosi N., Mazzucchelli M.L., Mihailova B., Scambelluri M., Angel R.J., Nestola, F., Reali A. & Alvaro M. (2018) - How geometry and anisotropy affect residual strain in host-inclusion systems: Coupling experimental and numerical approaches. American Mineralogist, 103(12), 2032-2035.

Murri M., Mazzucchelli M.L., Campomenosi N., Korsakov A.V., Prencipe M., Mihailova B.D., Scambelluri M., Angel R.J. & Alvaro M. (2018) - Raman elastic geobarometry for anisotropic mineral inclusions. American Mineralogist, 103(11), 1869-1872.
Validation activities for the Ice, Cloud, and Land Elevation Satellite - 2 (ICESat-2) Mission
Authors: Neumann Thomas , Brunt Kelly , Marguder Lori , Kurtz Nathan
Published: March 2020

After launching on 15 September 2018, the Ice, Cloud, and Land Elevation Satellite – 2 (ICESat-2) Mission began collecting data on 14 October 2018.  The mission uses green laser light emitted by the Advanced Topographic Laser Altimetry System (ATLAS) to detect individual photons that are reflected by the Earth’s surface and returned to ATLAS.  These photons, when combined with information on the pointing direction, and position of the observatory in space, provide a geolocation and elevation for every measurement that spans the globe from 88 degrees north latitude to 88 degrees south.  The Global Geolocated Photon data product provides a latitude, longitude, elevation, and measurement time for each photon event telemetered to Earth for each of the instrument’s six beams. This product also delineates between high, medium, and low signal confidence levels and those measurements associated with background noise. The higher level, along-track products each use different strategies for photon aggregation to optimize the precision and accuracy of the surface retrievals over specific surface types. These types include land ice, sea ice, vegetation/land, ocean, and inland water. There is a separate channel dedicated to atmospheric returns to measure cloud and aerosols over a vertical window of 15 km. Calibration efforts utilized well designed on-orbit maneuvers to identify both pointing and range biases attributed to orbital variations on the satellite. Once corrected, the science-quality data products were released to the public in May 2019.

 

In this presentation, we will present our ongoing work to evaluate and validate the geolocation and elevation accuracy and precision of measurements provided by the ICESat-2 mission.  The approaches are diverse in both location and methodology to ensure that we have a comprehensive assessment of the ATLAS performance variations throughout the orbital cycles. These strategies include comparisons with ground-based and airborne elevation measurements over the ice sheets, detailed analysis of returns from well-surveyed corner cube retro-reflectors, comparison of sea ice freeboard measured by airborne lidars, evaluation of global-scale ocean elevation through comparison with radar altimeters, and comparison of vegetation canopy height metrics measured by airborne lidar.  Our work to date demonstrates that individual photon elevations are accurate to approximately 30 cm vertically, and 6 m radially.  Aggregating many photons together reduces the elevation uncertainty to less than 5 cm for relatively flat and smooth ice sheet interiors.