bluuebunny/crossref_metadata_2025 huggingface dataset:
A statistical framework for evaluating EURO-CORDEX simulations and derived drought characteristics
Authors: Peres David J. , Senatore Alfonso , Nanni Paola , Cancelliere Antonino , Mendicino Giuseppe , Bonaccorso Brunella
Published: March 2021

Regional climate models (RCMs) are commonly used for assessing, at proper spatial resolutions, future impacts of climate change on hydrological events. In this study, we propose a statistical methodological framework to assess the quality of the EURO-CORDEX RCMs concerning their ability to simulate historic observed climate (temperature and precipitation). We specifically focus on the models’ performance in reproducing drought characteristics (duration, accumulated deficit, intensity, and return period) determined by the theory of runs at seasonal and annual timescales, by comparison with high-density and high-quality ground-based observational datasets. In particular, the proposed methodology is applied to the Sicily and Calabria regions (Southern Italy), where long historical precipitation and temperature series were recorded by the ground-based monitoring networks operated by the former Regional Hydrographic Offices. The density of the measurements is considerably greater than observational gridded datasets available at the European level, such as E-OBS or CRU-TS. Results show that among the models based on the combination of the HadGEM2 global circulation model (GCM) with the CLM-Community RCMs are the most skillful in reproducing precipitation and temperature variability as well as drought characteristics. Nevertheless, the ranking of the models may slightly change depending on the specific variable analysed, as well as the temporal and spatial scale of interest. From this point of view, the proposed methodology highlights the skills and weaknesses of the different configurations, aiding on the selection of the most suitable climate model for assessing climate change impacts on drought processes and the underlying variables.
Hydraulic characterization of low flow drip irrigation emitters used in intensive horticultural crops in Almeria (Spain)
Authors: Moreno-Pérez María Fátima , Baeza-Cano Rafael , Roldán-Cañas José , Cánovas-Fernández Gema , Reyes-Requena Rafael
Published: March 2021

In the present work, a selection of drip irrigation emitters used in greenhouse horticultural crops in the province of Almeria, Spain, were hydraulically evaluated, studying their hydraulic behavior and whether they meet with quality standards. Since manufacturers are offering lower flow emitters less spaced, all drippers tested are low flow. The hydraulic characterization will indicate the discharge and emission uniformity of the manufactured emitters, which are the fundamental parameters for the study of water use efficiency in drip irrigation. In the province of Almeria, water is a limiting factor due to the existence of a semi-arid climate, and, in addition, these limited water resources are used by intensive agriculture which causes a high consumption of these resources.

In total, 21 emitters have been evaluated, including all possible drippers according to their type of insertion (inline, pinched or online and interlinea), hydraulic behaviour (non-compensating and self-compensating) and, within the compensating ones, (anti-draining and non anti-draining). Its flow rates are between 1 and 2.4 l/h, except for a non-compensating interlina emitter of 3.8 l/h.

To carry out these tests, the criteria of the ISO 9261:2004 standard have been followed, calculating the coefficient of manufacturing variation and the emitter discharge equation on a test bench located in the La Mojonera Centre (Almeria) of the IFAPA (Andalusian Institute of Agricultural and Fishing Research and Training).

The results of this study show very good behavior in most of the emitters, and, as a consequence, a low coefficient of manufacturing variation has been obtained. The discharge equation obtained in the laboratory shows a low emisión exponent in the self-compensating emitters, being, therefore, the compensation of the pressures very high in all cases. No statistically significant differences have been found between self-compensating and non-compensating emitters by analysing their manufacturing variation coefficients. Nor have any significant differences been found between self-compensating emitters according to whether they are anti-draining or non-anti-draining, considering also the coefficient of variation. In anti-draining emitters, all closing pressures are not satisfied according to the standard, and are exceeded with very high values. The opening pressure is met for two of the four emitters, and one of those that does not meet it does so with a very large value.
The Mansurov Effect: Real or a statistical artefact?
Authors: Edvartsen Jone , Maliniemi Ville , Tyssøy Hilde , Asikainen Timo , Hatch Spencer
Published: March 2021

The Mansurov Effect is related to the interplanetary magnetic field (IMF) and its ability to modulate the global electric circuit, which is further hypothesized to impact the polar troposphere through cloud generation processes. In this paper we investigate the connection between IMF By-component and polar surface pressure by using daily ERA5 reanalysis for geopotential height since 1980. Previous studies have shown to produce a significant 27-day cyclic response during solar cycle 23. However, when appropriate statistical tests are applied, the correlation is not significant at the 95% level. Our results also show that data from three other solar cycles, which have not been investigated before, produce similar cyclic responses as during solar cycle 23, but with seemingly random offset in the timing of the signal. We examine the origin of the cyclic pattern occurring in the super epoch/lead lag regression methods commonly used to support the Mansurov hypothesis in all recent papers, as well as other phenomena in this community. By generating random normally distributed noise with different levels of temporal autocorrelation, and using the real IMF By-index as forcing, we show that the methods applied to support the Mansurov hypothesis up to now, are highly susceptible, as cyclic patterns always occurs as artefacts of the methods. This, in addition to the lack of significance, suggests that there is no adequate evidence in support of the Mansurov Effect.
Anisotropy of out-of-phase magnetic susceptibility due to eddy currents in graphite ore and its structural implications
Authors: Hrouda František , Franěk Jan , Chadima Martin , Ježek Josef , Mrázová Štěpánka , Poňavič Michal
Published: March 2021

Magnetostatic susceptibility of single crystals of graphite is negative (the mineral is diamagnetic) and strongly anisotropic. The in-phase component of dynamic susceptibility (measured in alternating magnetic field) is also negative, but an order-of-magnitude stronger than the magnetostatic susceptibility. The out-of-phase component, which is no doubt due to electrical eddy currents, is positive and strong. Consequently, if the graphite crystals in graphite ore are oriented preferentially by crystal lattice (LPO), one would expect strong anisotropy of magnetic susceptibility (AMS) of graphite ore in both in-phase (ipAMS) and out-of-phase (opAMS) components. The ipAMS is controlled not only by the LPO of graphite, but also by the preferred orientation of paramagnetic and ferromagnetic minerals of the barren rock, while the opAMS indicates only the LPO of graphite. In graphite ores occurring in the Moldanubian Unit of Southern Bohemia, the in-phase susceptibility ranges from negative values in the order of 10-5 [SI units] to positive values in the order of 10-4. This probably indicates simultaneous control by graphite and paramagnetic and/or ferromagnetic minerals. On the other hand, the out-of-phase susceptibility is much higher, in the order of 10-4, and no doubt indicates its graphite control. The degree of ipAMS is moderate, that of opAMS is truly high. The ipAMS foliation is roughly parallel to the metamorphic foliation in ores and wall rocks and the ipAMS lineation is parallel to the mesoscopic lineation. The opAMS is inverse to the ipAMS with the opAMS lineation being perpendicular to the metamorphic foliation. All this indicates a conspicuous LPO of graphite in the ore that was probably created during Variscan regional metamorphism and associated ductile deformation. The opAMS has therefore shown an effective tool for the investigation of the LPO of graphite in graphite ore or graphite-bearing rocks provided that the opAMS is strong enough to be determined with sufficient precision and graphite is the only conductive mineral in the samples investigated.
Single and multi-phase inclusions in garnets from the Lešnica alluvion in the Internal Dinarides, Serbia
Authors: Milošević Maja , Kostić Bojan
Published: March 2021

Inclusions in garnets from the river Lešnica alluvion (Cer mountain area, Serbia),  were investigated in an effort to study their distribution within the garnet host and to estimate the mechanism of their origin. Garnets are often occurring in the Lešnica alluvion in a form of loosely separated crystals with preserved crystalline forms and as mildly rounded broken grains [1]. Their mineralogical determination was previously published by Milošević et al, [1]. Crystals, that have been extracted and separated from the sandy fraction, have exhibited the presence of various types of inclusions in their structure. Single and multiphase inclusions in the garnets were examined optically by petrographic methods followed by SEM-EDS method, applied for the chemical analyses of the individual inclusion, and LA-ICP-MS applied to determine distribution and content of trace elements in the host garnet.

Results from SEM-EDS method show that garnets are of the spessartine-almandine type with the incorporation of irregular inclusions determined as rare earth elements (REE) minerals (monazite, xenotime, columbite-tantalite) and accessory minerals that usually incorporate REE (titanite, apatite, and zircon) together with uranium oxide minerals. Other single-phase inclusions are often quartz and rutile. Size of inclusion varieties from grain to grain, between 5 and 40 µm, while their distribution doesn’t follow any pattern, random distribution. It has been noted that zircon and uranium oxide minerals are often found coupled and as multiphase inclusions while monazite, xenotime and columbite-tantalite minerals are observed as separate, single, inclusions. Chondrite normalized REE in the host garnets plotted on spider diagram show extreme depletions of large ion lithophile elements (LILE) and enrichment in high field strength elements (HFSE), with negative Ce, Nd and Eu anomaly. Single-phase and multiphase inclusions that are occurring in the same garnet host with a random distribution are suggesting different genetic relations.

[1] Milošević M., Kostić B., Vulić P., Jelić I. 2019. Garnets from river Lešnica alluvion, mountain Cer. II Kongres Geologa Bosne i Hercegovine sa medjunarodnim učešćem, Pp. 306-311
Topographic Kernels for Gaussian Process Regression in Digital Soil Mapping
Authors: Gläßle Thomas , Rau Kerstin , Scholten Thomas , Hennig Philipp
Published: March 2021

Gaussian Processes provide a theoretically well-understood regression framework that is widely used in the context of Digital Soil Mapping. Among the reasons to use Gaussian Process Regression (GPR) are its interpretability, its builtin support for uncertainty quantification, and its ability to handle unevenly spaced and correlated training samples through a user-specified covariance kernel. The base case of GPR is performed with covariance models that are specified functions of Euclidean distance. In order to incorporate information other than the relative positions, regression-kriging extends GPR by an additive regression model of choice, and co-kriging considers a covariance model between covariates and the target variable. In this work, we use the alternative approach of incorporating topographic information directly into the kernel function by use of a non-Euclidean, non-stationary distance function. In particular, we devise kernels based on a path of least effort, where effort is locally specified as a function constructed from prior knowledge. It can e.g. be derived from local topographic variables. We demonstrate that our candidate models improve prediction accuracy over the base model. This shows that domain knowledge can be integrated into the model by means of handcrafted kernel functions. The approach is not per se restricted to topographic variables, but could be used for any covariate quantity that is available at output resolution.
Climate change will impact the protective effect of forests against rockfall
Authors: Moos Christine , Guisan Antoine , Christophe Randin , Heike Lischke
Published: March 2021

In mountain areas, forests play a crucial role in protecting people and assets from natural hazards, such as rockfall. Their protective effect is strongly influenced by their structure and state, which are expected to be affected by climate change. More frequent drought events, but also changing natural disturbance regimes, may lead to abrupt diebacks of contemporary species followed by a slow reforestation. In this study, we investigated how a changing climate can affect the protective capacity of mountain forests against rockfall. We therefore combined dynamic forest modelling with a detailed rockfall risk analysis at three case study sites in the Western Swiss Alps. Future forest development was simulated for a moderate and an extreme climate scenario for 200 years with the dynamic forest model TreeMig (Lischke et al., 2006). We then calculated rockfall risk for different forest states based on three-dimensional rockfall simulations with RockyFor3D (Dorren 2016). First results indicate that both at high elevation near the tree line (1500-2200 m a.s.l.) as well as at lower elevations (500-1000 m a.s.l.), increasing drought can lead to diebacks of trees and a reduction of tree density and diameters resulting in a substantial loss of the protective function. Depending on the speed of migration of other, more drought tolerant species, this loss can be partially compensated, but a permanent reduction of the protective effect is to be expected at least for an extreme climate scneario due to a reduced basal area of the forest.
Statistical post-processing of ensemble forecasts at the Belgian met service
Authors: Demaeyer Jonathan , Van schaeybroeck Bert , Vannitsem Stéphane
Published: March 2021

Statistical post-processing of ensemble weather forecasts has become an essential step in the forecasting chain as it enables the correction of biases and reliable uncertainty estimates of ensembles (Gneiting, 2014).  One algorithm recently proposed to perform the correction of ensemble weather forecasts is a linear member-by-member (MBM) Model Output Statistics (MOS) system, post-processing each member of the ECMWF ensemble (Van Schaeybroeck & Vannitsem, 2015). This method consists in correcting the mean and variability of the ensemble members in line with the observed climatology. At the same time, it calibrates the ensemble spread such as to match, on average, the mean square error of the ensemble mean. The MBM method calibrates the ensemble forecasts based on the station observations by minimizing the continuous ranked probability score (CRPS).

Using this method, the Royal Meteorological Institute of Belgium has started in 2020 its new postprocessing program by developing an operational application to perform the calibration of the ECMWF ensemble forecasts at the stations points for the minimum and maximum temperature, and for wind gusts. In this report, we will first describe briefly the postprocessing methods being used and the architecture of the application. We will then present the results over the first few months of operation. Finally, we will discuss the future developments of this application and of the program.

Gneiting, T., 2014: Calibration of medium-range weather forecasts. ECMWF Technical Memorandum No. 719

Van Schaeybroeck, B. & Vannitsem, S., 2015: Ensemble post-processing using member-by-member approaches: theoretical aspects. Quarterly Journal of the Royal Meteorological Society, 141, 807–818.
Earth system predictions of the carbon sinks and atmospheric CO2 growth: new insights and lessons from DCPP
Authors: Ilyina Tatiana , Li Hongmei , Müller Wolfgang , Spring Aaron
Published: March 2021

Initialized predictions of near-term future climate have proven successful and predictive power for the global carbon cycle is also emerging. Through extending ESM-based decadal prediction systems, i.e. those contributing to Decadal Climate Prediction Project (DCPP) with the ocean and land carbon cycle components, it becomes possible to establish predictability of the carbon sinks and variations of atmospheric CO2 concentrations. However, such predictions of the global carbon cycle still remain a cutting-edge activity of only a few modeling groups.

On interannual to decadal time-scales, atmospheric CO2 growth rates exhibit pronounced anomalies driven by varying strengths of the land and ocean carbon sinks; these anomalies are linked to climate variability on decadal and interannual time scales. Is it possible to predict if atmospheric CO2 changes slower of faster as expected from changes in emissions? This question is examined in a multi-model framework comprising prediction systems initialized by the observed state of the physical climate. The multi-model framework comprises ESM-based prediction systems that contributed to DCPP within CMIP6, as well as those which run with the CMIP5 forcing.

A predictive skill for the global ocean carbon sink of up to 6 years is found for some models. Longer regional predictability horizons are found across single models. On land, a predictive skill of up to 2 years is primarily maintained in the tropics and extra-tropics enabled by the initialization of the physical climate. Furthermore, anomalies of atmospheric CO2 growth rate inferred from natural variations of the land and ocean carbon sinks are predictable at lead time of 2 years and the skill is limited by the land carbon sink predictability horizon. These predictions of the global carbon cycle and the planet’s breath maintained by variations of atmospheric CO2 are essential to understand where the anthropogenic carbon would go in response to emission reduction efforts addressing global warming mitigation. Such information is useful to verify the effectiveness of fossil fuel emissions reduction measures.
Dual porosity effects in hydrological performance of extensive green roofs
Authors: Skala Vojtech , Dohnal Michal , Votrubova Jana , Snehota Michal , Heckova Petra
Published: March 2021

Artificial substrates for green infrastructure have different composition and properties compared to natural soils. The admixture of light porous minerals such as pumice or expanded clay is often used to decrease the substrate weight and to increase water storage capacity. On the other hand, it could lead to dual porosity character of substrates and may affect their retention properties.

The dual-continuum model S1D is used to asses water flow in extensive green roof test beds with artificial substrate. The model numerically solves dual set of Richards’ equations. The soil hydraulic properties are described using van Genuchten-Mualem approach. Selected model parameters were optimized using Levenberg-Marquardt algorithm.

Two green roof test beds located at the University Centre for Energy Efficient Buildings of the Czech Technical University in Prague are studied. The test beds are filled with 60 mm of extensive green roof substrate, planted with sedum cuttings, respectively 40 mm of substrate, planted with sedum carpet. The substrate is a mixture of spongilit (55 %), crushed expanded clay (30 %) and peat (15 %). The outflow from the test beds is registered by tipping bucket flowmeter and the moisture content within the soil substrate by TDR probes. The test bed with sedum carpet is also weighted. For complete hydrometeorological characterization, data from the nearby meteorological station are available.

Dual-continuum model provides higher flexibility and overall better agreement between measured and simulated variables. Further investigation of hydrological regime of such substrates and possible hysteresis of their soil water retention curve is needed.

The research was supported by the Czech Science Foundation under project number No. 20-00788S. Experimental work has been supported by the Ministry of Education, Youth and Sports within National Sustainability Programme I, project number LO1605.
Verification of climatological ERA5 and WRF convective environments using radiosonde data
Authors: Varga Ákos János , Breuer Hajnalka
Published: March 2021

Atmospheric convection is a major source of hazardous weather in many parts of the world, including the Pannonian Basin in Central Europe. It is therefore indispensable to explore the climatological distribution of convective environments and related phenomena, for which model data provide a spatially and temporally consistent alternative.

Several studies compared convective parameters derived from reanalysis datasets to radiosonde observations, but such evaluation of climate model output is less frequent.

This study uses sounding station measurements to verify convective environmental parameters derived from the ERA5 reanalysis and relatively coarse resolution WRF regional climate simulations for the 1985–2010 period over the wider Pannonian Basin region. Common parcel thermodynamic variables and environmental indices are calculated, such as CAPE, CIN, LI, TPW, lapse rate and wind shear. We carry out pointwise comparison between observed and modeled convective parameters in terms of basic statistical metrics and climatological means on a daily and monthly basis. Both pressure and model level data from ERA5 are included in the analysis.

In line with previous research, the ERA5 model level dataset reasonably represents the climatological distribution of convection-related variables. Preliminary results suggest that the WRF regional climate model is also quite skillful in reproducing convective environments, but large biases exist compared to the observations and reanalysis.

The research was supported by the Hungarian National Research, Development and Innovation Office, Grant No. FK132014.
Unsaturated hydraulic conductivity of vineyard soils with high rock fragment content in the Mosel area, Germany
Authors: Walle Selina , Iserloh Thomas , Seeger Manuel
Published: March 2021

The study deals with the unsaturated hydraulic conductivity of soils within the scope of the Diverfarming-Project, funded by the EU commission (Horizon 2020 grant agreement no 728003). For this reason, the field work took place in the examined vineyard of the Wawerner Jesuitenberg near Kanzem in the Saar-Mosel valley (Rhineland-Palatinate, Germany). The mentioned parameter is one of the most important specific factors of the hydrological cycle to characterize soil hydraulic properties in the unsaturated soil zone. A mini disc infiltrometer was used to measure the conductivity values at different suctions. The purpose of this study is to determine the plausibility of the fundamentals and the analytical expression of the unsaturated conductivity models in a nearly skeletal soil of schist. In this regard, the mathematical expressions of Mualem (1976), van Genuchten (1980) and Zhang (1997) are focused on calculating the unsaturated hydraulic conductivity. The two variables α and n are analysed in order to better compare between literature specifications and the explicit calculated data of the vineyard’s soil. As a result, the various developments of α are similar thus the significant difference is based on the value of n. Nevertheless, in consideration of these frame conditions the models represent a suitable mathematical expression of the unsaturated hydraulic conductivity. Furthermore, a range of parameters affecting this conductivity is analysed, particularly with regard to the applied variable soil and cultivation management under the grapevines in the vineyard. Also, the rock fragment cover and the pore size distribution are taken into account. In this context the soil compaction and modified pore size distribution in the wheel tracks stand out due to salient unsaturated hydraulic conductivities at higher tensions. In particular, the stone cover of the contact surface influence the characteristics of the analysed conductivity. Additionally, the connection of stone cover, management and pore size distribution creates a mixture of affected parameters of the unsaturated hydraulic conductivity.

 

Mualem, Y.: A new model for predicting the hydraulic conductivity of unsaturated porous media, Water Resour. Res, 12, 513–522, https://doi.org/10.1029/WR012i003p00513, 1976.

Van Genuchten, M.T.: A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils, Soil Sci. Soc. Am. J., 44, 892–898, https://doi.org/10.2136/sssaj1980.03615995004400050002x, 1980.

Zhang, R.: Determination of Soil Sorptivity and Hydraulic Conductivity from the Disk Infiltrometer, Soil Sci. Soc. Am. J., 61, 1024–1030, https://doi.org/10.2136/sssaj1997.03615995006100040005x, 1997.
Can plasticity explain microseismic source mechanisms?
Authors: Yarushina Viktoriya , Minakov Alexander
Published: March 2021

The microseismic events can often be characterized by a complex non-double couple source mechanism. Recent laboratory studies recording the acoustic emission during rock deformation help connecting the components of the seismic moment tensor with the failure process. In this complementary contribution, we offer a mathematical model which can clarify these connections. We derive the seismic moment tensor based on classical continuum mechanics and plasticity theory. The moment tensor density can be represented by the product of elastic stiffness tensor and the plastic strain tensor. This representation of seismic sources has several useful properties: i) it accounts for incipient faulting as a microseismicity source mechanism, ii) it does not require a pre-defined fracture geometry, iii) it accounts for both shear and volumetric source mechanisms, iv) it is valid for general heterogeneous and anisotropic rocks, and v) it is consistent with elasto-plastic geomechanical simulators. We illustrate the new approach using 2D numerical examples of seismicity associated with cylindrical openings, analogous to wellbore, tunnel or fluid-rich conduit, and provide a simple analytic expression of the moment density tensor. We compare our simulation results with previously published data from laboratory and field experiments.  We consider three special cases corresponding to "dry" isotropic rocks, "dry" transversely isotropic rocks and "wet" isotropic rocks. The model highlights theoretical links between stress state, geomechanical parameters and conventional representations of the moment tensor such as Hudson source type parameters. 
Optical properties of the Eastern Mediterranean Sea
Authors: Metheniti Vassiliki , Karageorgis Aristomenis P. , Kampanis Nikolaos , Sofianos Sarantis
Published: March 2021

The ocean's turbidity and optical properties are determined by the interaction of sunlight radiation with suspended particles and dissolved matter of the water body's surface layers. Variations in the optical properties can affect the upper ocean's heat content, thus modifying the stratification and the mixed layer dynamics. These variations can be monitored using satellite products, along with in-situ observations, and their impact on ocean circulation can be analyzed through numerical modeling. For the oligotrophic Eastern Mediterranean, there is a gap of in-situ data used to evaluate remote sensing observations. Furthermore, this region receives significant atmospheric deposition of particulate inorganic matter through African dust, as well as from river discharges. These constituents' contribution in optical properties modulation is often considered negligible for oligotrophic regions, where the various parameters have been calculated based on chlorophyll variations. To fill this gap, in situ measurements of beam attenuation coefficient at 660 nm (c, in m-1)(1) provided by the Hellenic Centre for Marine Research (HCMR) were assessed, and a gridded dataset was constructed using Data-Interpolating Variational Analysis (DIVA), for the Aegean Sea, Eastern Mediterranean, for the years 1991-2019. The aim is to validate the accuracy of satellite products for this region using this dataset. Towards this goal, available satellite ocean color products of the ocean's inherent optical properties will be used to estimate c values, which will be compared to the in-situ dataset.

1. A. P. Karageorgis et al., Deep Sea Res. Part I 55, 177–202 (2008).
The effect of Antarctic ice-shelf extent on ice discharge
Authors: Jordan Jim , Gudmundsson HIlmar , Jenkins Adrian , Stokes Chris , Jamiesson Stewart , Miles Bertie
Published: March 2021

The buttressing strength of Antarctic ice shelves directly effects the amount of ice discharge across the grounding line, with buttressing strength affected by both the thickness and extent of an ice shelf. Recent work has shown that a reduction in ice-shelf buttressing due to ocean induced ice-shelf thinning is responsible for a significant portion of increased Antarctic ice discharge (Gudmundsson et al., 2019, but few studies have attempted to show the effect of variability in ice-shelf extent on ice discharge. This variability arises due to ice-shelf calving following a cycle of long periods of slow, continuous calving interposed with calving of large, discrete sections.  These discrete calving events tend to occur on a comparative timeframe to that of the observational record. As such, when determining observed changes in ice discharge it is crucial that this natural variability is separated from any observed trends.  

 

In this work we use the numerical ice-flow model Úa in combination with observations of ice shelf extent to diagnostically calculate Antarctic ice discharge. These observations primarily date back to the 1970s, though for some ice shelves records exist back to the 1940s. We assemble an Antarctic wide model for two scenarios: 1) with ice shelves at their maximum observed extent and 2) with ice shelves at their minimum observed extent. We then compare these two scenarios to differences in the observed changes in Antarctic ice-discharge to determine how much can be attributed to natural variance .

 

Gudmundsson, G. H., Paolo, F. S., Adusumilli, S., & Fricker, H. A. (2019). Instantaneous Antarctic ice‐ sheet mass loss driven by thinning ice shelves. Geophysical Research Letters, 46, 13903– 13909. 
Investigating the relationship between seismic sequences and hydrological loading in the Azores
Authors: Lordi Ana L. , Neves Maria C. , Custódio Susana
Published: March 2021

Hydrological loads can be either surface loads induced by precipitation, changes in water levels at crater volcanic lakes, or subsurface loads created by seasonal changes in groundwater levels. These may contribute to strain and stress transients that trigger small earthquake swarms at faults that are already near failure. This work focusses on how annual and multi-annual stress changes of hydrological origin may affect the generation of seismic sequences on several tectonic settings, such as the New Madrid Seismic Zone and the Azores. The New Madrid seismic Zone is used as a benchmark test study region, while the Azores has been chosen for its intense seismic activity of both tectonic and volcanic origin. The magnitude of the hydrologically derived variations in stress is small compared with the long-term tectonic stresses, so we look for seasonal and inter-annual modulations of the earthquake occurrence rate. This requires the manipulation of seismic catalogues and the use of statistical methods to check if the seasonal and inter-annual variations are statistically significant, and not the result of extreme climatic events. The impact of hydrologic loads on faults is addressed using high-quality time series of seismic sequences, rainfall and other loads produced by variations in water levels, methods of decomposition and reconstruction of geophysical time series (SSA and wavelet transform) to identify modes of oscillation, and correlation analysis to recognize common patterns in seismicity and water loads. The results provide the first assessment of cyclic variations in seismicity and its relationship with atmospheric disturbances and hydrologically-driven load in the Azores region, and contributes to improve our understanding of the physics of earthquake triggering processes. The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL. This is a contribution to the RESTLESS project PTDC/CTA-GEF/6674/2020.
Aragonite is calcite’s best friend at the seafloor
Authors: Sulpis Olivier , Agrawal Priyanka , Wolthers Mariette , Munhoven Guy , Walker Matthew , Middelburg Jack
Published: March 2021

Aragonite is about 50% more soluble than calcite in seawater and its pelagic production is dominated by pteropods. Moreover, it could account for a large fraction of marine CaCO3 export. The aragonite compensation depth (ACD, the depth at which accumulation is balanced by dissolution) is generally very close to the aragonite saturation depth, i.e. within a few hundred metres. Conversely, the calcite compensation depth (CCD) can be 1-2 kilometres deeper than the calcite saturation depth. That aragonite disappears shallower than calcite in marine sediments is coherent with aragonite’s greater solubility, but why is the calcite lysocline, i.e. the distance between its compensation and saturation depths, much thicker than its aragonite equivalent?

Here, we suggest that at the seafloor, the addition of a soluble CaCO3 phase (aragonite) results in the preservation of a predeposited stable CaCO3 phase (calcite), and term this a negative priming action. In soil science, priming action refers to the increase in soil organic matter decomposition rate that follows the addition of fresh organic matter, supposedly resulting from a globally increased microbial activity (Bingeman et al., 1953). Using a new 3D model of CaCO3 dissolution at the grain scale, we show that a conceptually similar phenomenon could occur at the seafloor, in which the dissolution of an aragonite pteropod at the sediment-water interface buffers the porewaters and causes the preservation of surrounding calcite. Since aragonite-producing organisms are particularly vulnerable to ocean acidification, we expect an increasing calcite to aragonite ratio in the CaCO3 flux reaching the seafloor as we go further in the Anthropocene. This could, in turn, hinder the proposed aragonite negative priming action, and favour chemical erosion of calcite sediments.

 

Reference: Bingeman, C.W., Varner, J.E., Martin, W.P., 1953. The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil. Soil Science Society of America Journal 17, 34-38.
Response of Extratropical Cyclones when Crossing a Sea Surface Temperature Front
Authors: Bui Hai , Spengler Thomas
Published: March 2021

Sea surface temperatures (SSTs) can influence the development of extratropical cyclones by providing latent and sensible heat through surface fluxes as well as by modifying the environmental low-level baroclinicity. As surface fluxes as well as low-level baroclinicity maximize along the prominent SST fronts associated with the Gulf Stream and Kuroshio, the influence of these mechanisms on cyclone development is anticipated to be strongest along SST fronts. To map the sensitivity to the structure and position of SST fronts during the development of extratropical cyclones, we examine the response of cyclones when they cross an SST front at different directions and speeds. The results are based on idealized numerical simulations with the WRF model, where we prescribe moving SST fronts and a baroclinically unstable environment with an incipient cyclone. Cyclones moving towards the warmer side of the SST front deepen faster and have a faster crossing speed. The diabatic production of eddy available potential energy through latent heating, mainly associated with convection, plays a dominant role in the deepening. Cyclones that move to the colder side of the SST front weaken due to a reduction of available moisture for diabatic processes. However, before these cyclones weaken, they experience a brief period of faster deepening attributable to the enhanced environmental low-level baroclinicity associated with the SST gradient.
Towards an integrated study of urban CO2 emissions
Authors: Pilz Lukas , Vardag Sanam , Kleinschek Ralph , Hammer Samuel , Butz André
Published: March 2021

High-resolution monitoring is the basis for CO2 emissions tracking and attribution in urban areas. This work is an important step towards an integrated urban CO2 emissions monitoring system. Three middle-cost nondispersive infrared (NDIR) sensors of 500€ to 3000€ are characterised. Furthermore, CO2 emissions of large, regional point sources are simulated to analyse their effect on these sensors’ signals.

The three sensors are Vaisala GMP343, Senseair HPP3 and SmartGas FlowEvo CO2. Their analysis and characterisation is achieved by co-locating them with a Picarro G2401 cavity ringdown spectrometer for 40 days. Co-locating different middle-cost sensors is novel and enables a direct performance comparison. While the HPP3 is the only one to reach a 1 min mean standard deviation under 1 ppm, the GMP343 is the most linear and stable with a drift of 0.03(2) × 10−1 ppm per day and the SmartGas sensor provides the best price-to-performance ratio. For all sensors, precisions (the 1 min mean error’s lower bound) of under 0.8 ppm are determined. In general, temperature stabilisation turns out to be one of the most promising avenues of performance improvement for all sensors.

The sensors’ in-situ measurements are combined with meso-scale meteorological simulations for the Rhine-Neckar region using the Weather Research and Forecasting model (WRF). In two case-studies, simulated excess CO2 due to large, regional point sources and measured CO2 concentration are compared. Both simulations show qualitative agreement with the measurements. The differences between measurements and simulation, however, highlight aspects to be refined. These include increasing the horizontal and vertical resolution of the simulation domain as well improving as the parametrisation of the planetary and urban boundary layer.
A joint soil-vegetation-atmospheric modeling procedure of water isotopologues with WRF-Hydro-iso: Implementation and application to present-day climate in Europe and Southern Africa
Authors: Arnault Joel , Jung Gerlinde , Haese Barbara , Fersch Benjamin , Rummler Thomas , Wei Jianhui , Zhang Zhenyu , Kunstmann Harald
Published: March 2021

Water isotopologues, as natural tracers of the hydrological cycle on Earth, provide a unique way to assess the skill of climate models in representing realistic atmospheric and terrestrial water pathways. In the last decades, many global and regional models have been developed to represent water isotopologues and enable a direct comparison with observed isotopic concentrations. This study presents the recently developed regional model, WRF-Hydro-iso, which is a version of the coupled atmospheric – hydrological modeling system WRF-Hydro enhanced with a joint soil-vegetation-atmospheric description of water isotopologues motions. WRF-Hydro-iso is applied to two regions in Europe and Southern Africa under present climate condition. The setup includes an outer domain with a 10 km grid-spacing, an inner domain with a 5 km grid-spacing, and a subdomain with a 500 m grid spacing that can be coupled with the inner domain in order to represent lateral terrestrial water flow. A 10-year slice is simulated for 2003-2012, using ERA5 reanalyses for the boundary condition. The boundary condition of the isotopic variables is specifically provided with climatological values deduced from a 10-year simulation with the Community Earth System Model Version 1. For both Europe and Southern Africa, WRF-Hydro-iso realistically reproduces the climatological variations of the isotopic concentrations δP18O and δP2H from the Global Network of Isotopes in Precipitation. In a sensitivity analysis, it is found that land surface evaporation fractionation increases the isotopic concentrations in the rootzone soil moisture and slightly decreases the isotopic concentrations in precipitation, an effect that is modulated by the change in evaporation – transpiration partitioning caused by lateral terrestrial water flow. The ability of WRF-Hydro-iso to account for a detailed description of terrestrial water transport makes it as a good candidate for the dynamical downscaling of global paleoclimate simulations and for the comparison to isotopic measurements in proxy data such as plant wax fossils.
Reaction rates in the hyporheic zone explained by the lamellar theory of mixing
Authors: Rousseau Gauthier , Le Borgne Tanguy , Heyman Joris
Published: March 2021

At the interface between aquifers and rivers, hyporheic zones are shallow sediment layers where surface and subsurface waters mix and react. In these zones, the dynamic of solute transport and mixing is a crucial and limiting component for many biogeochemical reactive processes (arsenic and nitrates degradation for instance). In particular, the understanding of the consequence of flow path heterogeneity on solute mixing and reactivity is key to develop physically-based upscaled models of the hyporheic function. By simulating the evolution of reacting fronts under simple 2D and 3D heterogeneous hyporheic flows created by bed superficial pressure gradients, we show that incomplete mixing of reacting solutes systematically precludes the use of macro-dispersion models as upscaled models of the hyporheic function, both in steady and unsteady flow conditions.
Based on these simulations, we propose an alternative theoretical framework, based on the concept of solute lamellae stretched by flow velocity gradients, to correctly upscale local reaction rates at the reach and basin scale. Finally, we compare our numerical and theoretical results to reacting fronts in a laboratory scale hyporheic mixing experiment.
Evidence of acceleration in regional sea-level rise in the North Sea
Authors: Riva Riccardo , Steffelbauer David , Timmermans Jos , Kwakkel Jan , Bakker Mark
Published: March 2021

Tide gauges are the main source of information about sea-level changes in the Industrial Age. When looking at global mean values, century-long reconstructions produce rates between 1-2 mm/yr, while estimates over the last three decades reveal a much faster rise of about 3 mm/yr, as also indicated by satellite altimetry observations. In spite of this evidence for a recent acceleration, its quantification remains a challenging and relevant task, because results are highly dependent on the length of the record and on the reconstruction technique, whereas decision makers require clear proof to legitimise action. While global mean results are very important to understand climate change, regional to local variations are more relevant for the purpose of planning mitigation and adaptation measures. However, mainly due to natural variability, looking at individual tide gauge stations hampers the accurate determination of linear and non-linear trends.
We developed a time series analysis framework to determine whether SLR is accelerating by detecting the presence of a break-point in the long-term trend. We applied the framework to tide gauges in the southern North Sea, where several stations provide high-quality and uninterrupted records spanning more than a century (1890-2018). On average, coastal sea level rise increased from ~1.8 mm/yr over the first century of our study to ~2.8 mm/yr over the last 25 years, albeit with large inter-station differences. We performed several tests to assess the impact of natural variability on the observed trend changes and verified that stable break-points are only detected since the late 1970s, with the exact year depending on the chosen time-window. Therefore, we believe that the high sea-level rates observed over the last few decades are likely representing long-term changes.
Mediterranean Temporary Ponds: using isotope hydrology tools to describe and understand their behaviour
Authors: Mattei Alexandra , Sorba Laurent , Garel Emilie , Santoni Sebastien , Orsini Sophie , Huneau Frédéric
Published: March 2021

Mediterranean temporary ponds are very shallow ponds, isolated from permanent water bodies, which undergo a periodic cycle of flooding and drought, and have a characteristic flora and fauna adapted to this alternation. This habitat is mainly distributed in dry and sub-arid areas. Mediterranean temporary ponds are identified as one of the worldwide biodiversity hotspots and constitutes therefore a priority habitats according to the Natura 2000 network of the European Union (3170*, Council Directive 92/43/CEE). The development of flora and fauna in this type of ecosystem is defined by the natural length of the hydro-period. However, little is known about the hydrological functioning of these very specific hydrosystems. DespiteHS10 this protective conservation status, this habitat has suffered continuous degradation and loss disappearing at a fast rate due anthropogenic impacts and climate pressures. In most cases, temporary wetland disappearance is unintentional and related to a lack of understanding of its hydrological functioning within the watershed.

The aim of this work is, hence, to use the tools of the isotope hydrology to increase our basic understanding of the hydrological functioning of the Mediterranean temporary ponds. Our study focuses on the Musella temporary pond located in Southern Corsica (France) which undergoes important man-induced and climatic pressures. During one full hydrological cycle, surface and groundwater levels, major ions, stable isotopes of the water molecules as well as field parameters (temperature, pH, electrical conductivity, dissolved oxygen) have been measured every month.

Results bring information on the water quality, chemical stability and temporal evolution in terms of surface water level as well as potential connection with the underlying carbonated aquifer. The stable isotopes inform about the origin of water, its mixing processes with groundwater, and its evaporative status through time.

Flooding and drying processes of the Musella temporary pond are now better constrained and documented projections can now be set up towards the resilience of the hydrosystem considering the future consequences of climate change in the Mediterranean region.