bluuebunny/crossref_metadata_2025 huggingface dataset:
Geomagnetic paleointensity and paleoinclination between 1200 and 1700 AD derived from brick buildings in northern and south-eastern Poland.
Authors: Nawrocki Jerzy , Standzikowski Karol , Rosowiecka Olga , Wójcik Krystian , Werner Tomasz , Łanczont Maria , Gancarski Jan , Wiewióra Marcin
Published: March 2020

The bricks are one of the best material for archeomagnetic studies. They usually contain a very stable and intense remanent magnetization and their backing technique (i.e. horizontal location in the furnace) allow to determine the value of inclination of geomagnetic field.  The technique were not changing since the middle ages up to the half of the XIX century, when a machine production have started. Preliminary archeomagnetic studies of the brick samples from Poland that providing a general information about paleoinclination changes in Gdańsk since 1080 AD indicated that this material is suitable for determination of ancient geomagnetic field parameters. However, in spite of the presence of many brick objects, as well as early and great tradition of brick building in Poland, this region of Europe is still “Tabula Rasa”  on the map of current archeomagnetic investigations. The archeomagnetic curves for this part of  Central Europe will be constructed almost from foundations. Well defined curves with secular variations of geomagnetic field during last 2500 year were constructed for example in neighboring Germany. The bricks for our archeomagnetic study were selected from churches, castles and palaces of well-known age. The age uncertainty in each case was less than 25 years. In order to check historical ages, a comparative TL dating of selected bricks was also conducted. The paleointensity of geomagnetic field  was determined using the IZZI-Thellier-Thellier protocol. About 300 cylindrical  specimens from the bricks located in more than 50 historical objects were examined. Studies of magnetic carriers and studies of anisotropy of magnetic susceptibility and anisotropy of isothermal remanent magnetization were also performed. The obtained paleosecular curves were compared with the coeval data from other regions of Europe.
A comprehensive global sensitivity analysis using generic sampling designs by means of a combination of variance- and distribution-based approaches.
Authors: Baroni Gabriele , Francke Till
Published: March 2020

Global sensitivity analysis has been recognized as a fundamental tool to assess the input-output model response and evaluate the role of different sources of uncertainty. Among the different methods, variance- and distribution-based (or also called moment-independent) methods have mostly been applied. The first method relies on variance decomposition while the second method compares the entire distributions. The combination of both methods has also been recognized to provide possibly a better assessment. However, the methods rely on different assumptions and the comparison of indices is not straightforward. For these reasons, the methods are commonly not integrated or even considered as alternative solutions. 

In the present contribution, we show a new strategy to combine the two methods in an effective way to perform a comprehensive global sensitivity analysis based on a generic sampling design. The strategy is tested on three commonly-used analytic functions and one hydrological model. The strategy is compared to the state-of-the-art Jansen/Saltelli approach.

The results show that the new strategy quantifies main effect and interactions consistently. It also outperforms current best practices by converging with a lower number of model runs. For these reasons, the new strategy can be considered as a new and simple approach to perform global sensitivity analysis that can be easily integrated in any environmental models.
Global reconstruction of surface temperature fields for past equilibrium climates
Authors: Hargreaves Julia , Annan James
Published: March 2020

Paleoclimate simulations are widely used as a test of the ability of climate models to simulate climate states that are substantially different to the present day, and quantitative reconstructions of these climate states is an essential component of model evaluation.  With there being no large network of instrumental observations from these periods, we must rely on inferences from a relatively modest number of unevenly distributed proxy records which are believed to be quantitatively indicative of the climate state.  In order to robustly establish climatic conditions over global scales, we require methods for smoothing and interpolating between these sparse and imperfect estimates.  In recent years, we have worked on this problem and created a global reconstruction of the Last Glacial Maximum [Annan and Hargreaves, 2013, Climate of the Past] using the data and models which were available at that time.  The method uses scaled patterns from the PMIP ensemble of structurally diverse climate simulations, combined with sparse sets of proxy data, to produce spatially coherent and complete  data  fields  for  surface  air  and  sea  temperatures  (potentially  including  the  seasonal cycle)  along  with  uncertainty  estimates  over  the  whole  field.   This  approach  is  more  robust than alternative methods, which either perform a purely statistical interpolation of the data or at best combine the data with a single climate model. Here, we aim to improve the method, update the inputs, and apply the same technique to both Last Glacial Maximum and mid Pliocene climate intervals. As well as generating spatially complete and coherent maps of climate variables, our approach also generates well-calibrated uncertainty estimates.
Spatial variability in terrestrial and aquatic carbon stocks and fluxes in boreal forested catchments
Authors: Casson Nora , Ducharme Adrienne , Amarawansha Geethani , Gunn Geoff , Higgins Scott , Kumaragamage Darshani , Vitharana Udayakantha
Published: March 2020

Canada’s boreal zone is a complex mosaic of forests, wetlands, streams and lakes.  The pool of carbon (C) stored in each of these ecosystem components is vast, and significant to the global C balance.  However, C pools and fluxes are heterogeneous in time and space, which contributes to uncertainty in predicting how a changing climate will affect the fate of C in these sensitive ecosystems. The objective of this study was to investigate factors controlling spatial variability in soil C stocks and stream C export and assess the sensitivity of these stocks and fluxes to climatic factors. We conducted a detailed examination of soil C stocks and stream dissolved organic C (DOC) export from a 320 ha boreal forested catchment located in northwestern Ontario, Canada. High-frequency stream chemistry and discharge samples were collected from three inflow streams during snowmelt and rain events from 2016-2017. An intensive soil C sampling campaign resulting in 47 surface (0 – 30 cm) samples were collected during the summer of 2019. Stream hysteresis analysis revealed marked differences in flowpaths among sub-catchments during snowmelt and rain events. In the wetland-dominated catchment, near-stream sources contributed most of the DOC export during both rainstorms and snowmelt events, but in upland-dominated catchments, the sources of DOC depended on antecedent moisture conditions. Rainstorms in these catchments following prolonged droughts resulted in DOC flushing from distal regions of the catchment. Soil C stocks were also highly spatially variable, with much of the variability being explained by local-scale factors (e.g. gravel content, soil depth, distance to the nearest ridge). Taken together, these two findings emphasize the need to consider sub-catchment scale variability when calculating C pools and fluxes in boreal catchments. This is also important when predicting how C dynamics will shift in the future as a result of shorter winters, longer droughts and more intense rainstorms.
Observation and Numerical Simulation of Propagation of ULF Waves From the Ion Foreshock Into the Magnetosphere
Authors: Takahashi Kazue , Turc Turc , Kilpua Emilia , Takahashi Naoko , Dimmock Andrew , Kajdic Primoz , Palmroth Minna , Pfau-Kempf Yann , Soucek Jan , Singer Howard , Motoba Tetsuo , Kletzing Craig
Published: March 2020

Observational studies have demonstrated that ULF waves excited in the ion foreshock are a main source of Pc3-4 ULF waves detected in the magnetosphere. However, quantitative understanding of the propagation of the waves is not easy, because the waves are generated through a kinetic process in the foreshock, pass through the turbulent magnetosheath, and propagate as fast mode waves and couple to shear Alfven waves within the magnetosphere.  Recent advancement of hybrid numerical simulations of foreshock dynamics motivated us to analyze observational data from multiple sources and compare the results with simulation results. We have selected the time interval 1000-1200 UT on 20 July 2016, when the THEMIS, GOES, and Van Allen Probe spacecraft covered the solar wind, foreshock, magnetosheath, and magnetosphere. The EMMA magnetometers (L=1.6-6.5) were located near noon. We found that the spectrum of the magnetic field magnitude (Bt) in the foreshock exhibits a peak near 90 mHz, which agrees with the theoretical prediction assuming an ion beam instability in the foreshock.  A similar Bt spectrum is found in the dayside outer magnetosphere but not in the magnetosheath or in the nightside magnetosphere.  On the ground, a 90 mHz spectral peak was detected in the H component only at L=2-3. The numerical simulation using the VLASIATOR code shows that the foreshock is formed on the prenoon sector but that the effect of the upstream waves in the magnetosphere is most pronounced at noon. The Bt spectrum of the simulated waves in the outer magnetosphere exhibits a peak at 90 mHz, which is consistent with the observation.
A multi-scale investigation of geometrically derived z0 from Hintereisferner, Austrian Alps
Authors: Chambers Joshua , Smith Mark , Smith Thomas , Quincey Duncan , Carrivick Jonathan , Nicholson Lindsey , Mertes Jordan , Sailer Rudolf , Stiperski Ivana
Published: March 2020

Spatially and temporally distributed values of glacier aerodynamic roughness (z0) are required to improve estimates of glacier melt. z0, representing the topographically-controlled height above the surface where wind speed reaches zero, is shown by empirical studies to be spatially and temporally dynamic, yet, z0 is commonly overlooked as a tuning parameter in models or generalised between surfaces and over time. Indirect estimates of z0 made from microtopographic measurements allow for rapid data collection over large areas but are sensitive to measurement scale, data resolution and detrending technique. The recent proliferation of remotely sensed topographic data from airborne and satellite sources has created a wealth of resources, as yet untapped in this particular field. We present a multi-scale analysis using data collected from Hintereisferner, Austria, with a view to upscaling current methods for estimating 3D microtopographic z0 so that coarser resolution, broader scale data can be used to estimate z0 at the glacier scale. Our extensive dataset covers a spectrum of scales from 5 x 5 m plots (at sub-cm resolution) to scans of almost the whole glacier surface from an in-situ terrestrial laser scanner.
Uncertainty analysis of greenhouse gases emission: application to the EDGAR inventory
Authors: Solazzo Efisio , Bergamaschi Peter , Choulga margarita , Oreggioni Gabriel , Muntean Marilena , Crippa Monica , Janssens-Maenhout Greet
Published: March 2020

Emission inventories of greenhouse gases built up from international statistics of human-related activities and emission factors (often referred to as ‘bottom-up’ inventories) are at the core of emission trend analysis to inform policy actions and scientific applications, to support climate negotiation and pledges for mitigation options.

Increasingly gaining importance is the quantification of the inherent uncertainty of these inventories that could allow moving towards a verification system in support of the enhanced transparency framework of the Paris Agreement, in particular the global stocktakes. Recently, two H2020 projects – CHE (CO2 Human Emissions) and VERIFY – are focusing on this sensible aspect. This paper produces an unprecedented propagation of uncertainty applied to emissions of CO2, CH4 and N2O, impinging in both projects. Starting from the human emission estimates of the Emission Database for Global Atmospheric Research (EDGAR), which encompasses historic and sectoral emissions from all world countries and using the error propagation method, uncertainties of the CO2, CH4 and N2O emissions were computed per sector and country.

The devised methodology applies uncertainty stemming from statistics of human activity and emission factors using the guidelines of Intergovernmental Panel on Climate Change (IPCC 2006). The analysis takes into consideration the accuracy of emission estimates for developed versus developing countries, correlation arising from sector aggregation, and includes an ad-hoc treatment for specific sources and country specific emission factors. The results of emissions and their uncertainties are available for all world countries and all IPCC/EDGAR sectors, and for each country, the share of the total uncertainty each sector is responsible for, is identified.

Our results show that world-wide CO2, CH4 and N2O emissions lies in a confidence range of 5%, 33% and in excess of 100%, respectively. The sectors most responsible for such uncertainty depend strongly on the statistical infrastructure of the country but we observe in general that few sectors with smaller emission total are contributing to a large proportion of the total uncertainty.

This global uncertainty assessment aims at contributing to the European initiative of the CO2 Monitoring Task Force, building up an operational greenhouse gas monitoring and verification support capacity.
Recent atmospheric circulation trends: two major flaws in reanalyses and in climate models
Authors: Chemke Rei , Polvani Lorenzo
Published: March 2020

The weakening of the Hadley cell and of the midlatitude eddy heat fluxes are two of the most robust responses of the atmospheric circulation to increasing concentrations of greenhouse gases.  These changes have important global climatic impacts, as the large-scale circulation acts to transfer heat and moisture from the tropics to polar regions.  Here, we examine Hadley cell and eddy heat flux trends in recent decades: contrasting model simulations with reanalyses, we uncover two important flaws -- one in the reanalyses and other in the model simulations -- that have, to date, gone largely unnoticed.

First, we find that while climate models simulate a weakening of the Hadley cell over the past four decades, most atmospheric reanalyses indicate a considerable strengthening.  Interestingly, that discrepancy does not stem from biases in climate models, but appears to be related to artifacts in the representation of latent heating in the reanalyses.  This suggests that when dealing with the divergent part of the large-scale circulation, reanalyses may be fundamentally unreliable for the calculation of trends, even for trends spanning several decades.

Second, we examine recent trends in eddy heat fluxes at midlatitudes, which are directly linked the equator-to-pole temperature gradient.  In the Northern Hemisphere models and reanalyses are in good agreement. In the Southern Hemisphere, however, models show a weakening while reanalyses indicate a robust strengthening.  In this case, the flaw is found to be with the climate models, which are unable to simulate the observed multidecadal cooling of the Southern Ocean at high-latitudes, and the accompanying increase in sea-ice.  While the biases in modeled Antarctic sea ice trends have been widely reported, our results demonstrates that such biases have important implications well beyond the high Southern latitudes, as they impact the equator-to-pole temperature and, as a consequence, the midlatitude atmospheric circulation.
From small whirls to the global ocean: how eddies affect the Atlantic Meridional Overturning Circulation
Authors: Katsman Caroline , Brüggemann Nils , Georgiou Sotiria , Sayol Espana Juan-Manuel , Ypma Stefanie , van der Boog Carine , Pietrzak Julie
Published: March 2020

In the North Atlantic Ocean, intense downward motions connect the upper and lower limbs of the Atlantic Meridional Overturning Circulation (AMOC). In addition, the AMOC also displays a pronounced signature in density space, with lighter waters moving northward and denser waters returning southward.

While at first glance it is appealing to associate this sinking of water masses in the North Atlantic Ocean with the occurrence of the formation of dense water masses by deep convection, this is not correct: the net vertical motion over convection areas is small. The downward flow required to connect the upper and lower branches of the AMOC thus has to occur outside the deep convection areas. Indeed, earlier studies have pointed out theoretically that strong sinking can only occur close to continental boundaries, where ageostrophic processes play a role. However, observations clearly indicate that convected water masses formed in marginals seas constitute an important component of the lower limb of the AMOC.

This apparent contradiction is explored in this presentation, by studying the overturning in the AMOC from a perspective in depth space (Eulerian downwelling) and density space (downwelling across isopycnals). Based on analyses of both a high-resolution global ocean model and dedicated process studies using idealized models we analyze the characteristics of the sinking, of diapycnal mixing, and investigate how these are linked. 

It appears that eddies play a crucial role for the overturning, both in depth space and density space. They control the characteristics of the yearly cycle of convection and restratification, the magnitude of the Eulerian sinking near continental boundaries, and steer the export of dense waters formed in the interior of the marginal seas via the boundary current system.

These studies thus reveal a complex three-dimensional view on sinking, diapycnal water mass transformation and overturning in the North Atlantic Ocean, involving the boundary current, the interior and interactions with the eddy field.  This implies that it is essential to resolve these eddies to be able to properly represent the overturning in depth and density space in the North Atlantic Ocean and its response to changing conditions in a future climate.
Patterns in CO2 exchange to the atmosphere from a borehole located in a Mediterranean karst system (Málaga, southern Spain)
Authors: Sanchez-Cañete Enrique P. , Benavente José , Liñan Cristina , Ojeda Lucía , Vadillo Iñaki
Published: March 2020

The vadose zone (VZ), found between the surface and groundwater level, can store massive amounts of CO2, recording values greater than 60,000 ppm to depths of a few tens of meters. The CO2 is produced mostly in the first meters of soil due to root respiration and microorganisms and, to a lesser extent, to geochemical reactions. Although commonly CO2 is produced mostly near the surface, the concentration increases with depth, due mainly to transport in two phases: 1) infiltration of CO2-enriched water followed by precipitation and CO2 release in deeper layers, and 2) percolation of CO2-rich air due to its high density. These transport process contribute to natural CO2 accumulation in the VZ, whose storage capacity depends on its thickness and porosity. All this CO2 storage can be exchange with the atmosphere mainly determined by differences in the temperature between the internal and external atmosphere.

Here we study a borehole located next to Nerja Cave (Málaga, Spain) developed within fissured and karstified Triassic dolomitic marbles. Our objective is to determine the main drivers involved in subterranean CO2 exchange with the atmosphere. To do that, CO2 molar fraction, air temperature, relative humidity, wind speed and direction were monitored in the top of the borehole, and were correlated with external variables as air temperature, relative humidity, atmospheric pressure, rain and sea tides. Results shown that within a few hours, the CO2 molar fraction can increase ten times more, showing a pattern with two cycles per day. In periods with low CO2 molar fraction the air penetrates into the borehole, on the other hand, periods with high CO2 values are due to the borehole CO2-rich air is moving toward the external atmosphere. We found that the CO2 emitted to the atmosphere by this borehole is several orders of magnitude than the soil CO2 fluxes in this area. Therefore, we need to produce accurate long-term estimates of borehole CO2 fluxes to improve our understanding of its contribution to local carbon balance.
Kinetic Energy Conversion in A Wind-forced Submesoscale Flow
Authors: Li Song , Serra Nuno , Stammer Detlef
Published: March 2020

Despite recent progress in measuring the ocean eddy field with satellite missions at the mesoscale (order of 100 km), containing the major fraction of ocean kinetic energy, many questions still remain regarding the generation, conversion and dissipation mechanisms of eddy kinetic energy (Ke). In this work, we use the output from an idealized 500-m resolution ocean numerical simulation to study the conversion of Ke in the absence and presence of wind stress forcing. In contrast to the result of the unforced run, Ke increased approximately nine times in the mixed layer and considerably in the pycnocline in the forced run. Eddies and filaments were seen to re-stratify the mixed layer and wind-induced turbulence at the base of the mixed layer promoted its deepening and therefore dramatically enhanced the exchange between Ke and eddy available potential energy (Pe). The wind stress forcing additionally affected the conversion processes between Pe and mean kinetic energy (Km). The wind also excited inertial and superinertial motions throughout almost the whole water column. Although those motions played a major role in the conversion between Pe and Ke, the net effect by inertial and superinertial flows was almost null. In addition, we found an asymmetric character in kinetic energy conversion in eddies. Cyclonic and anti-cyclonic eddies showed different behaviour regarding conversion from Pe and Ke, which was positive on the high Ke part in the anti-cyclonic eddy but negative in the cyclonic eddy.
First observation of multi-groundwater level responses to the strongest worldwide seismicity in Central Apennines (Central Italy).
Authors: Barberio Marino Domenico , Gori Francesca , Barbieri Maurizio , Billi Andrea , Franchini Stefania , Petitta Marco , Doglioni Carlo
Published: March 2020

Earthquakes are the main natural processes which are able to cause the strongest crustal perturbations in the world. Seismic events change crustal stress, both static and dynamic, in the co-seismic and post-seismic phases. In particular, hydrogeological and hydrogeochemical responses include: changes in water level, temperature, chemical composition, stream flow, and gas geochemistry. Among these parameters water level changes is the most recorded signal because of its fast acquisition and easy instrumentation. Depending on the involved mechanism, groundwater level variation is different. In particular, previous studies have highlighted permanent and transient signals which are characterized by step and spike changes both upward and/or downward. Only few studies have reported groundwater level variations induced by earthquakes that are very far away from the observation point and they are known as “teleseism”. In order to investigate relationship between groundwater properties and seismic cycle, since July 2014 we installed a multiparameter probe in a 100 m deep groundwater well (PF60.3) in Central Apennines (Central Italy). This monitoring well is part of a more complex monitored test site developed for this aim and it has recorded already hydrogeochemical anomalies related to Amatrice-Norcia 2016-2017 seismic sequence. The occurrence of the strongest earthquakes in the world (≈Mw>7.5), from the well probe installation (July 2014) until January 2020, has caused significant changes in groundwater level data. We analysed groundwater level behaviour in relationship to the occurrence of all 218 seismic events with Mw>6.5. We identified 16 interactions, where groundwater level is characterized by an anomalous spike change both upward and/or downward. In particular, we observed a significant interaction between signals for all the strongest seismic events with a Mw≥7.6, except for those happened in Papua Nuova Guinea and for those with ipocenter depth greater than 150 kilometers. We also found some interactions for less strong seismic events (6.5<Mw<7.5) but closer to the monitoring site. Among the observed correlations, 5 are characterized by a Mw between 8 and 8.2 meanwhile the others have a Mw between 6.5 and 7.9. The ipocenter depths of the considered 16 events are within 100 km, except two events that are deeper. We calculated the maximum amplitude of the perturbation and its duration. In this study we present our results with the main aim of expanding our understanding about perturbations due to distant earthquakes in the upper crust and in particular the relative fluid migration.
Improving reference evapotranspiration (ETo) calculation under limited data conditions in the Tropical Andes
Authors: Vásquez Cristina , Córdova Mario , Carrillo Galo , Célleri Rolando
Published: March 2020

The correct determination of reference evapotranspiration (ETo) is fundamental for countless scientific and management applications such as closing the catchment water balance, the planning of irrigation schemes, and for simulation models. Nevertheless, the records of weather variables are often not available or incomplete. This usually happens when a sensor breaks or malfunctions due to severe weather conditions, lack of maintenance or electronic failure, which leads to data loss and consequently makes it hard to estimate ETo. Frequently, that is the case in mountain regions where meteorological sensors are subject to harsh environmental conditions as in the Andes. In case of missing data, the only solution is to estimate the required variable using a given equation. Therefore, these equations need to be calibrated to specific local conditions. The aim of this study was to calibrate and validate equations to estimate Solar Radiation (Rs) on daily and monthly scales and to evaluate the impact of using these estimations for the calculation of ETo through the Penman Monteith (PM) equation in an Andean altitudinal gradient in the páramo ecosystem. The páramo occupies the upper portion of the northern Andes, where the tussock grasslands are the dominant vegetation. In addition, this ecosystem provides essential environmental services for inter-Andean cities. We used six years of observations (2013–2019) from the Quinoas Ecohydrological Observatory. This Observatory has four meteorological stations: Toreadora (3955 m a.s.l), Virgen Cajas (3626 m a.s.l), Chirimachay (3298 m a.s.l) and Balzay (2610 m a.s.l). We evaluated five models to estimate Rs based on the maximum and minimum daily air temperature. A calibration was performed for each weather station and a simultaneous calibration for the entire gradient. We used four years of data for calibration and validation of the Rs model, and two years to evaluate the impact on ETo calculations. We found that all models yielded estimations that are highly correlated with the observed data. However, no model was able to capture high Rs values, greater than 185.4 W m-2 (16 MJ m-2 d-1), found in cloud-free days. The best model to estimate Rs was the locally calibrated Chen model, which showed a mean error of 2.9 W m-2 (0.25 MJ m-2 d-1).  Estimated Rs values reduced the estimation error of PM-ETo and, thus, allows its application for further studies.
Climate Change risks and adaptation for Mediterranean grapevine production
Authors: Santillan David , Garrote Luis , Iglesias Ana , Sotes Vicente
Published: March 2020

Traditional Mediterranean crops, such as grapevine, a permanent wood crop, are well adapted to the lack of water and recurrent drought in the Mediterranean region. This study uses grapevine production indicators that are widely used by practitioners, linking science to the tools used by practitioners and therefore encouraging action and innovation among all stakeholders. The study evaluates potential adaptation choices that may contribute to real-time policy analysis and development as national and international policies and agreements in the grapevine production sector. The climate changes scenarios are derived from global datasets. Adaptation efforts are estimated proportionally to the change of the climatic indices and are categorized into low, medium or high, as a function of the excepted changes in climatic indices. The study emphasizes that non-informed adaptation limits future choices in areas severely impacted. The content of the study is based on the results of the iSQAPER (http://www.isqaper-project.eu/) H2020 project and the UPM Adapt project.
Constraining the geometry at depth of La Maladeta and Andorra-Mont Louis granites (Central Pyrenees) through gravity modelling
Authors: Ayala Conxi , Clariana Pilar , Soto Ruth , Martí Joan , Margalef Aina , Pueyo Emilio , Rubio Félix , Rey-Moral Carmen , Bach Nuria , Schamuells Stefania , Cirés Jordi
Published: March 2020

In the Central Pyrenees, where density contrast between the Paleozoic rocks and the intruded granitic bodies is measurable, geological cross-sections constrained with gravity data help to unravel the subsurface geometry of the granites.

With this goal in mind, during 2018 and 2019 several gravimetric surveys were carried out in the Central Pyrenees to improve the existent spatial resolution of the gravity data from the databases of the Spanish and Catalan Geological Surveys, especially in La Maladeta and Andorra Mont-Louis granites’ area. After the gravity reductions, we obtained the Bouguer gravity anomaly from which we calculated the residual gravity anomaly by subtracting a third degree polynomial which represents the regional anomaly in agreement with the geometry of the crust in this region.

The gravimetric response over La Maladeta and Andorra Mont-Louis granites is markedly dissimilar pointing out differences in the composition and geometry at depth of the two granites. La Maladeta granite shows a gravimetric zonation with small variations in its amplitude from one zone to the next, consistent with small lateral changes in its composition, predominantly granodioritic. By contrast, the Andorra Mont-Louis pluton is characterized by a relative minimum suggesting a more granitic composition.

With respect to the inferred geometry at depth, the results obtained from gravity modelling show that the La Maladeta granite displays a laccolithic shape with its basal contact deeping to the North whereas the Andorra Mont-Louis granite has a more batholitic shape. Although the emplacement age of both granites is similar (Late Carboniferous – Early Permian), their different geometry at depth suggests that either (1) their emplacement mechanisms were different or (2) the subsequent Alpine orogeny affected both granites in different ways better preserving the original geometry of the Andorra Mont-Louis granite.
Exploring the limits of conventional hydrograph separation
Authors: Benettin Paolo
Published: March 2020

The separation of runoff into different components, typically some “event” (or “new”) water as opposed to some “baseflow” (or “old”) water, is a task that has been attracting hydrologists for decades. The ability to separate runoff sources has implications for our understanding of hydrological processes and to predict changes due to e.g. deforestation or urbanization. Although the methodology has notably evolved during the years, the most conventional and widespread application involves a two-component separation achieved through stable isotopes or electrical conductivity measurements. Use of this approach is based on a strong assumption that is difficult to test in the field: the signatures of the two end-members either do not change during the event or their variations can be taken into account. By using extensive numerical tests, this contribution explores the limits of this assumption. Results highlight the importance of considering the time-varying contribution of soil water, which is not event-water nor baseflow, and show that the method can easily lead to incorrect estimates when the above assumption is not met.
From aquifers’ and rivers’ memory to a better low-flow forecasting model
Authors: Pelletier Antoine , Andréassian Vazken
Published: March 2020

The 2019 major drought in northern France highlighted the necessity to design an efficient and reliable low-flow forecasting system. Most forecasting tools, based on rainfall-runoff surface models, could benefit from an utilization of piezometric data, broadly available over the French metropolitan territory: obviously, surface water/groundwater interaction are a key process to explain low-flow dynamics.

Indeed, aquifers carry most of the hydroclimatic memory of a catchment, which determines the intensity and duration of droughts: a catchment beginning summer with empty aquifers will not have the same trajectory as the same catchment with higher than average piezometric levels. However, the piezometric data itself is not straightforward to use in a hydrological model, since aquifer-river connexions are often equivocal. Thus, a prior analysis of available data is necessary.

In this work, using 100 catchments of the national French hydroclimatic database and available piezometric data from the national aquifer monitoring network, we performed a comparative memory analysis of piezometry and streamflow, through a simple convolution function. The results were then compared to the behaviour of GR6J, a conceptual lumped rainfall-runoff model. For each catchment of the dataset, a selection of relevant piezometers was made, in the perspective of developing a model incorporating their levels as input data.
The role of permafrost soils in Arctic mercury cycling: source tracing with Hg stable isotopes and revised soil pool estimate
Authors: Jiskra Martin , Sonke Jeroen E. , Lim Artem G. , Loiko Sergey V. , Kosykh Natalia , Pokrovsky Oleg , Agnan Yannick , Helmig Detlev , Obrist Daniel
Published: March 2020

Mercury (Hg) is a pollutant of great concern for indigenous populations in the Arctic, which are exposed to high dietary Hg from fish and marine mammal consumption. Hg in marine biota can be derived from direct atmospheric deposition to the Arctic Ocean or from terrestrial sources by river runoff. Permafrost soils thereby play a pivotal role in the Arctic Hg cycle by storing atmospheric Hg deposition and providing a reservoir for later mobilization to the Arctic Ocean. The stability of Hg in permafrost soils depends on the pathway of atmospheric Hg deposition and Hg release processes, i.e. reduction and re-emission to the atmosphere and transfer to river runoff. We combined Hg stable isotope with Hg flux measurements in a field study on the Arctic Coastal Plain in northern Alaska. We could show that gaseous elemental Hg uptake by vegetation represents 70% of total atmospheric Hg deposition. Atmospheric Hg uptake by vegetation results in a characteristic Hg isotope fingerprint. This fingerprint dominates Hg signatures in permafrost soils measured across the Arctic coastal plain and is also imprinted in marine mammals and Ocean sediments, suggesting that Hg from Arctic permafrost soils represent a major source to the Arctic Ocean. Knowing the pool and spatial distribution of Hg in permafrost soils is therefore essential to assess current Hg mobilization to aquatic ecosystems and potential future changes due to permafrost thaw and climate change. Two recent studies have used Hg to carbon (C) ratios, RHgC, measured in Alaskan permafrost mineral and peat soils, together with a northern soil carbon inventory, to estimate that these soils contain large amounts, 184 to 755 Gg of Hg in the upper 1 m. In a second part, we present new Hg and C data for six peat cores, down to mineral horizons, across a latitudinal permafrost gradient in the Western Siberian lowlands. Hg concentrations increase from south to north in all soil horizons, reflecting enhanced net accumulation of atmospheric gaseous elemental Hg by the vegetation Hg pump. We reviewed and estimate pan-arctic organic and mineral soil RHgC to be 0.19 and 0.77 Gg Pg-1, and use a soil C budget to revise the northern soil Hg pool to be 67 Gg (37-88 Gg, interquartile range (IQR)) in the upper 30 cm and 225 Gg (102-320 Gg, IQR) in the upper 1 m. Finally, we discuss how climate change may affect the mobilization of Hg from permafrost soils to the atmosphere and the Arctic Ocean.
Gathering knowledge on mesopelagic ecosystems: insights from a parsimonious modelling approach
Authors: Conchon Anna , Titaud Olivier , Senina Inna , Calmettes Beatriz , Delpech Audrey , Lehodey Patrick
Published: March 2020

SEAPODYM-LMTL is the Lower (zooplankton) and Mid (micronekton) Trophic levels model of the Spatial Ecosystem And POpulation DYnamic Modeling framework. Currently, there is one zooplankton and 6 micronekton functional groups defined according to their vertical behavior and development times. The model is global and spatially explicit with transport described through a system of advection-diffusion equations. The vertical dimension is simplified into three layers -- epipelagic, upper and lower mesopelagic -- defined relatively to the euphotic depth. There are three vertically migrant and three non-migrant functional groups. The model is parsimonious with only a few parameters (6 for the zooplankton and 11 for the micronekton) that control the energy transfer efficiency from the primary production and the mortality and time of development that are linked to the water temperature. A data assimilation framework has been implemented to estimate those parameters.  We present briefly the latest results and future challenges of this model. They include the validation of vertical layer boundaries, the first zooplankton and micronekton parameters estimation using existing biomass observations, and the developments needed to use large global datasets of acoustic data. 
River incision, climate and vertical motions since the LGM in south-western Alps (France)
Authors: Petit Carole , Yann Rolland , Régis Braucher , Didier Bourlès , Thibaut Cardinal , Apolline Mariotti , Laurence Audin
Published: March 2020

In South-Western European Alps, although scarce, evidences of recent vertical motions suggest a slow (~0.1 mm/yr) uplift of the northern Ligurian margin, which increases towards to East from the Var river mouth to the gulf of Genova. Whether this uplift is due to active compressional tectonics, to isostatic rebound or to a combination of both is still unclear. In addition, because of the large topographic gradient, rivers have carved deep gorges in the bedrock of the SW subalpine chains. However, neither the role of vertical motion nor that of climatic changes since the LGM on river incision rates is well established.

Over the last 10 years, a dataset of 10Be and 36Cl based cosmic ray exposure (CRE) ages obtained on river and glacier polished surfaces in the SW French Alps has been gathered. This dataset covers several areas located in the Argentera crystalline massif, in the Nice and Castellane subalpine chains, and in the Provence domain.

We will present a compilation of these data in an attempt to answer the following questions: - what is the influence of the last glaciation on river incision rates? - Is there any evidence of a W-E gradient in incision rates that could reflect increasing uplift rates of the SW Alps and North Ligurian margin? First results tend to indicate that all river incision rates are remarkably similar since the Holocene glacial optimum, whereas two different tendencies arise before that time: catchments within the influence of Alpine glaciers tend to have larger incision rates during the last deglaciation, while at the same time catchments out of any glacial influence have slightly lower incision rates. This suggests that, at first order, the release of glacier meltwaters enhanced river incision rates downstream during the ~20-12 ka period.
Towards soil micro-zymography: comparison of staining and impregnation strategies
Authors: Ghaderi Negar , Guber Andrey , Schmidt Hannes , Blagodatskaya Evgenia
Published: March 2020

Enzymes are produced by microorganisms either intracellularly in cell’s cytoplasm and periplasm or extracellularly either as attached to outer surface of cell membranes or released to the soil microhabitats. The distribution of microhabitats in soil is highly heterogeneous with high abundance of microorganisms in the small volume of soil hotspots, e.g., in the rhizosphere - the most important plant-soil interface with very dynamic interactions between roots and microorganisms. Soil zymography is one of the most realistic methods developed to visualize enzyme activity in undisturbed soil at the mesoscale (mm-cm) level using substrate-saturated membranes. However, visualization of enzymatic processes at the micro-scale level remains a challenge. We tested several impregnation strategies of soil sample (e.g., by agarose gel, silicon spray and super transparent silicon mixture) for their suitability for micro-zymography, i.e., for visualization of enzyme activity in undisturbed soil particles at the microscopic level combining fluorogenic substrates with epifluorescence microscopy. The pros- and cons- of various combinations of impregnation and staining of micro-sized soil samples will be discussed.

Keywords: enzyme activity, zymography, fluorogenic substrates
New solution to an old problem: improved parameter estimation of soil hydraulic functions
Authors: Papritz Andreas , Lehmann Peter , Gupta Surya , Sara Bonetti , Or Dani
Published: March 2020

The representation of land surface properties in hydrologic and climatic models critically depends on soil hydraulic functions (SHF). Parameters of SHF are routinely identified from soil water retention (SWR) and hydraulic conductivity (HC) data by nonlinear least squares. This is a notoriously difficult task because typically only few measurements are available per sample or plot for estimating the many SHF parameters (up to seven for the van Genuchten-Mualem model). As a consequence, the estimated parameters are often highly uncertain and could yield unrealistic predictions of related physical quantities such as the characteristic length Lc for stage‑1 evaporation (Lehmann et al., 2008). We address these limitations by capitalizing on the conditional linearity of some of the SHF parameters. Conditional linear parameters, say μ, can be substituted in the least squares objective by an explicit estimate (Bates & Watts, 1988), leading to an objective that depends only on the remaining nonlinear parameters ν. This step substantially reduces the dimensionality of the SHF estimation and improves the quality of estimated parameters. Additionally, instead of minimizing the least squares objective only with box constraints for ν, we minimize it by nonlinear programming algorithms that allow to physically constrain estimates of ν by Lc. We have implemented this estimation approach in an R software package capable of processing global SWR and HC data. Using ensemble machine learning algorithms, the novel parameter estimation results will be coupled with auxiliary covariates (vegetation, climate) to create improved global maps of SHF parameters.

References:

Bates, D. M. Watts, D. G. 1988. Nonlinear Regression Analysis and Its Applications. John Wiley & Sons, New York.

Lehmann, P., Assouline, S., Or, D. 2008. Characteristic lengths affecting evaporative drying of porous media. Physical Review E, 77, 056309, DOI 10.1103/PhysRevE.77.056309.
Seismic scattering and absorption of oceanic lithospheric S waves in the Eastern North Atlantic
Authors: Hannemann Katrin , Eulenfeld Tom , Krüger Frank , Dahm Torsten
Published: March 2020

Seismic scattering and absorption parameters provide valuable information about the propagation of seismic waves within the lithosphere. For the analysis of the seismic scattering and absorption parameters in the oceanic lithosphere of the Eastern North Atlantic, we use a seismological array which was installed in 5000 m water depth about 100 km North of the Gloria fault, defining the plate boundary between the Eurasian and African plate at this location. During our seismological experiment, more than 350 local and regional earthquakes were identified within 10 month for epicentral distances up to 900 km. The acquired regional earthquake recordings show up to 30 Hz P and S wave arrivals with long codas lasting tens to hundreds of seconds. Modelling results suggest that these long codas originate from scattering in the oceanic lithosphere. The waves travel with upper mantle apparent velocities and are therefore referred to as oceanic Pn (Po) and Sn (So) waves. We use direct So waves and their coda of pre-selected earthquakes to estimate frequency-dependent seismic scattering and intrinsic attenuation parameters. The results for the analysed events show that intrinsic attenuation is stronger than scattering attenuation and the estimated transport mean free path lengths between 30-800 km indicate that the So wave coda is weakly influenced by the oceanic crust. Furthermore, the calculated parameters show higher attenuation for western to northern event azimuths than for eastern to southern ones which might be related to differences in lithospheric ages for example of the Eurasian and African plates, or the influence of the Gloria fault itself.