bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerobic methanotrophic activity stimulates iron reduction in lake sediments 
Authors: Vigderovich Hanni , Eckert Werner , Elvert Marcus , Sivan Orit
Published: March 2022

Recent observations from shallow anoxic lacustrine sediments around the world show an unexpected presence of bacterial methanotrophs, usually typified to be aerobic, together with anaerobic microorganisms, such as methanogens and iron reducers, which may result from undetectable traces of oxygen or a yet to be understood biochemical process producing oxygen. Both mcr gene-bearing archaea and pmoA gene-bearing bacterial methanotrophs were suggested to mediate methane oxidation in Lake Kinneret sediments. In these sediments, iron reduction was shown to be coupled to methane oxidation; however, with an unclear mechanism linked to methanotrophy. Here we show a new set of geochemical and microbial data from slurry experiments that tested the effect of exposure of oxygen on this aerobic and anaerobic activity. Surprisingly, exposure of oxygen levels up to 1% promoted aerobic methanotrophy and increased net iron reduction in anoxic lake sediments. The iron reduction was microbially mediated and performed by either Desulfuromonas or Geobacter or Methylomonas. The experiments provide insight into the complex life and biogeochemical cycles in anoxic lake sediments. 
Water Vapour assessment using GNSS and Radiosondes and long-term trends estimation over Polar Regions
Authors: Negusini Monia , Petkov Boyan , Tornatore Vincenza , Barindelli Stefano , Martelli Leonardo , Sarti Pierguido , Tomasi Claudio
Published: March 2022

The atmospheric humidity in the Polar Regions is an important factor for the global budget of water vapour, which is a significant indicator of Earth’s climate state and evolution. The Global Navigation Satellite System (GNSS) can make a valuable contribution in the calculation of the amount of Precipitable Water Vapour (PW). We focus on Polar Regions, especially Antarctica. 20-year GPS observations, acquired by more than 40 GNSS geodetic stations, were processed with the purpose of ensuring the utmost accuracy of the PW retrieval, adopting homogeneous, consistent, and up-to-date processing strategies. We also estimated PW from radio-sounding stations (RS), which operate Vaisala radiosondes, co-located with GNSS stations. The PW values from global atmospheric reanalysis model were used for validation and comparison, very high correlation coefficients between times series, have been highlighted both in the Arctic and Antarctica. A small dry bias of RS vs. GPS values was found in the Arctic, while no clear behaviour is present in Antarctica. The PWGPS and PWRS seasonal variations are consistent, as also confirmed by scatter plots.

After validation, long-term trends, both for Arctic and Antarctic regions, were estimated using Hector scientific software, which allows the estimation of trends from time series with temporal correlated noise. We applied a function to estimate the linear trend plus the annual/semiannual signals, and autoregressive noise model AR(1) which best fits the residuals of all investigated PW time series. We investigated also on the choice of the most suitable noise model, this study was useful in determining the residuals of the time series, once the trend and seasonal signals were subtracted. Positive PWGPS trends dominate at Arctic sites near the borders of the Atlantic Ocean. Sites located at higher latitudes show no significant values. Negative PWGPS trends were observed in the Arctic region of Greenland and North America. A similar behaviour was found in the Arctic for PWRS trends. The stations in the West Antarctic sector show a general positive PWGPS trend, while the sites on the coastal area of East Antarctica exhibit some significant negative PWGPS trends, while in most cases, no significant PWRS trends were found. The present work confirms also that GPS is also able to provide reliable estimates of water vapour content in regions where data are sparse and not easy to collect as the Arctic and Antarctic regions are.
Lessons learnt from the landslides triggered during and after the 2018 Mw 7.5 Papua New Guinea earthquake
Authors: Tanyas Hakan , Kevin Hill , Luke Mahoney , Islam Fadel , Luigi Lombardo
Published: March 2022

This study presents an event inventory for the co-seismic landslides induced by the February 25, 2018 Mw 7.5 Papua New Guinea earthquake as well as its post-seismic counterparts including the landslides triggered by either aftershocks or succeeding rainfall events that occurred between February 26 and March 19. We mapped approximately 11,600 landslides of which more than 10,000 were triggered by the mainshock with a total failed planimetric area of about 145 km2. Such a large area makes this inventory the world’s second-largest recorded landslide event after the 2008 Wenchuan earthquake. Large landslides are abundant throughout the study area located within the remote Papua New Guinea Highlands. Specifically, more than half of the landslide population is larger than 50,000 m2 and overall, post-seismic landslides are even larger than their co-seismic counterparts. Our analyses indicate that large and widespread landslides were triggered as a result of the compound effects of the strong seismicity, complex geology, steep topography and high rainfall. We statistically show that the 15-day antecedent precipitation, as a predisposing factor, contributes to the spatial distribution of co-seismic landslides. Also, we statistically demonstrate that the cumulative effect of aftershocks is the main factor disturbing steep hillslopes and causing the initiation of very large landslides up to the size of ~5 km2. Taking aside the role of the intense seismic swarm and antecedent precipitation, these inventories also provide evidence for landslide events where the active tectonics contribute to weaken hillslopes and the fatigue damage. Overall, the dataset and the findings provided by this paper is a step forward in seismic landslide hazard assessment of the entire Papua New Guinea mainland.
Residence time of groundwater in porous aquifers by estimating Ra retardation factor
Authors: Briganti Alessandra , Voltaggio Mario , Tuccimei Paola , Soligo Michele
Published: March 2022

Groundwater age can differ when determined by radioactive tracers due to different retardation factors. According to Krishnawami et al. 1982, Radon isotopes supply to groundwater is considered as a measure of the supply of Radium isotopes. This assumption considerably affects the estimation of the Ra retardation factor. Briganti et al. 2020 reports how the different groundwater supply mechanisms of Ra and Rn should be considered in order to avoid a relevant variation between the real water residence time and the age calculated. In the same work an alternative method for estimating Ra retardation factor is proposed without using Rn data as a comparison term. A synthesis of the main results of laboratory tests is presented in order to describe possible applications of the method.

References

Briganti A., Voltaggio M., Tuccimei P. & Soligo M. 2020. Radium in groundwater hosted in porous aquifers: estimation of retardation factor and recoil rate constant by using NAPLs. SN Appl. Sci. 2, 1934 (2020). https://doi.org/10.1007/s42452-020-03610-4

Krishnaswami S., Graustein W.S., Turekian K.K., Dowd J.F. 1982. Radium, thorium and radioactive lead isotopes in groundwaters: application to the in situ determination of adsorption-desorption rate constants and retardation factors. Water Resour. Res. 18:1633–1675.
Evapotranspiration components of pine (Pinus brutia) trees in a Mediterranean ecosystem
Authors: Amini Mohsen , Djuma Hakan , Sofokleous Ioannis , Eliades Marinos , Bruggeman Adriana
Published: March 2022

One of the most deterministic aspects of water consumption in Mediterranean ecosystems is
evapotranspiration, which accounts for returning a large fraction of precipitation into the atmosphere.
Pine trees as an indigenous species play an important role in the soil water balance in these ecosystems.
The main objective of this study is to simulate the contribution of evapotranspiration components of pine
(Pinus brutia) in the water balance. The research includes a comprehensive sensitivity analysis and model
calibration. The field study is located in Athalassa Forest Park in Cyprus. The 10-ha field is covered by a
combination of seasonal vegetation and indigenous trees and shrubs, with a 5 to 6-m planting distance.
The site is relatively flat with a mean slope of 4% and an average annual rainfall of 315 mm.
Pine tree evapotranspiration components were modeled using a one-dimensional NOAH-MP land surface
model (one grid cell). Due to incomplete knowledge about the extent of the tree roots (root zone area),
we modeled the grid cell in three different scenarios according to tree density (the distance between
trunks, 5-6 m), tree canopy area (7.5 m2 on average), and leaf area index (LAI = 2.5 on average) to
represent our field study in the model. We analyzed the sensitivity of all modeled water balance
components, namely, evapotranspiration (evaporation from bare soil, transpiration, and evaporation
from the canopy), runoff (surface and subsurface runoff), soil moisture change of the soil column to all
related soil and vegetation input parameters, using a local sensitivity analysis. We also examined the
impact of the number of soil layers with roots, different soil layers thicknesses, and the slope of the area
on the model outputs (water balance components). The results showed that NOAH-MP is capable of 
representing a semi-arid Mediterranean ecosystem.

This research has received financial support from the PRIMA MED (2018 Call) SWATCH Project and the
Water JPI (Joint Call 2018) FLUXMED Project, both funded through the Cyprus Research and Innovation
Foundation.
Seasonal forecasts of the Saharan heat low characteristics: a multi-model assessment
Authors: Ngoungue Langue Cedric Gacial , Lavaysse Christophe , Vrac Mathieu , Peyrillé Philippe , Flamant Cyrille
Published: March 2022

The Saharan heat low (SHL) is a key component of the West African Monsoon system at the synoptic scale and a driver of summertime precipitation over the Sahel region. Therefore, accurate seasonal precipitation forecasts rely in part on a proper representation of the SHL characteristics in seasonal forecast models. This is investigated using the latest versions of two seasonal forecast systems namely the SEAS5 and MF7 systems from the European Center of Medium-Range Weather Forecasts (ECMWF) and Météo-France respectively. The SHL characteristics in the seasonal forecast models are assessed based on a comparison with the fifth ECMWF Reanalysis (ERA5) for the period 1993–2016. The analysis of the modes of variability shows that the seasonal forecast models have issues with the timing and the intensity of the SHL pulsations when compared to ERA5. SEAS5 and MF7 show a cool bias centered on the Sahara and a warm bias located in the eastern part of the Sahara respectively. Both models tend to underestimate the interannual variability in the SHL. Large discrepancies are found in the representation of extreme SHL events in the seasonal forecast models. These results are not linked to our choice of ERA5 as a reference, for we show robust coherence and high correlation between ERA5 and the Modern-Era Retrospective analysis for Research and Applications (MERRA). The use of statistical bias correction methods significantly reduces the bias in the seasonal forecast models and improves the yearly distribution of the SHL and the forecast scores. The results highlight the capacity of the models to represent the intraseasonal pulsations (the so-called east–west phases) of the SHL. We notice an overestimation of the occurrence of the SHL east phases in the models (SEAS5, MF7), while the SHL west phases are much better represented in MF7. In spite of an improvement in prediction score, the SHL-related forecast skills of the seasonal forecast models remain weak for specific variations for lead times beyond 1 month, requiring some adaptations. Moreover, the models show predictive skills at an intraseasonal timescale for shorter lead times.
Conceptualizing World-Earth System resilience: Exploring transformation pathways towards a safe and just operating space for humanity
Authors: Anderies John M. , Barfuss Wolfram , Donges Jonathan F. , Fetzer Ingo , Heitzig Jobst , Rockström Johan
Published: March 2022

We develop a framework within which to conceptualize World-Earth System resilience.  Our notion of World-Earth System resilience emphasizes the need to move beyond the basin of attraction notion of resilience as we are not in a basin we can stay in. We are on a trajectory to a new basin and we have to avoid falling into undesirable basins.  We thus focus on `pathway resilience', i.e. the relative number of paths that allow us to move from the transitional operating space we occupy now as we leave the Holocene basin  to a safe and just operating space in the Anthropocene. We develop a mathematical model to formalize this conceptualization and demonstrate how interactions between earth system resilience  (biophysical processes) and world system resilience (social processes) impact pathway resilience.  Our findings show that building earth system resilience is probably our only chance to reach a safe and just operating space.  We also illustrate the importance of world system dynamics by showing how the notion of fairness coupled with regional inequality affects pathway resilience. 
Carbon assimilation and water use efficiency increases in undisturbed core forest areas may not compensate carbon losses
Authors: Montibeller Bruno , Marshall Michael , Mander Ülo , Uuemaa Evelyn
Published: March 2022

Global heating is affecting the gross primary production (GPP; i.e., amount of CO2 assimilated by plants) and evapotranspiration (ET; i.e., water loss from surface evaporation and transpiration) across forests in the northern hemisphere. Increasing temperatures have induced a prolonged growing season that has enhanced GPP during the spring and autumn seasons. In the summer season, it has resulted in higher ET. Although these findings are reported in multiple studies, we lack investigations that specifically analysed long-term regional scale changes in GPP and ET in undisturbed core forest areas, which play an important role in the carbon and water fluxes. Analyses of GPP and ET changes across undisturbed forest areas are essential to understand how these areas are adapting to new climate conditions and contribute to the mitigation of human greenhouse gas emissions. In our study, we used Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to investigate the trends and changing rates of GPP, ET and water-use-efficiency (i.e., quantity of carbon assimilated by litre of water; WUE=GPP/ET) across undisturbed forest areas in Europe from 2000 to 2020 at monthly basis. We used the Mann-Kendal test to identify the significance of trends and the Theil–Sen estimator to quantify the monthly rate of change. The results indicated that during early spring and late autumn, approximately half of the total undisturbed core forest areas (3601.5 km2), mostly located in eastern Europe, showed an increase in GPP and ET. These areas also showed an increase in WUE because the increase in GPP was greater than the ET. However, most forest areas showed a decrease in GPP during summer, which was not compensated by the GPP increase during spring and autumn. These uncompensated forest core areas were spatially scattered across different forest types in Europe and were responsible for offsetting 20% of the total GPP increase in all European forest core areas. Our results provided evidence that certain forest core areas have limitations to act as carbon sinks, therefore, reducing the capacity to mitigate human carbon emissions. Moreover, by identifying the location of these forests, our results can support the application of management strategies that enhance carbon assimilation. 

 
Seismological characterization of dynamics parameter of the Hunga Tonga explosion from teleseismic waves
Authors: Poli Piero , Shapiro Nikolai
Published: March 2022

Most of the largest volcanic activity in the world occurs in remote places as deep oceans or poorly monitored oceanic islands. Thus, our capacity of monitoring volcanoes is limited to remote sensing and global geophysical observations. However, the rapid estimation of volcanic eruption parameters is needed for scientific understanding of the eruptive process and rapid hazard estimation. We first a method to rapidly identify large volcanic explosions, based on analysis of seismic data. The method automatically detects and locate long period (0.01-0.03Hz) signals associated with physical processes close to the Earth surface, by analyzing surface waves recorded at global seismic stations. With this methodology, we promptly detect the January 15, 2022 Hunga Tonga eruption, among many other signals associated with known and unknown processes. We further use the waves generate by the Hunga Tonga volcanic explosion and estimate important first-order parameters of the eruption (Force spectrum, impulse). We then relate the estimated parameters with the volcanic explosivity index (VEI). Our estimate of VEI~6, indicate how the Hunga Tonga eruption is among the largest volcanic activity ever recorded with modern geophysical instrumentation, and can provide new insights about the physics of large volcanoes.
Global ionospheric signature of the tsunami triggered by the 2022 Hunga Tonga volcanic eruption
Authors: Munaibari Edhah , Rolland Lucie , Sladen Anthony , Delouis Bertrand
Published: March 2022

The Hunga Tonga volcanic eruption on Jan. 15, 2022 released a highly energetic atmospheric pressure wave that was observed all around the globe in different types of measurements (e.g., barometers and infrasound sensors, satellites images, ionospheric measurements, etc.). In addition, the eruption triggered a meteo-tsunami followed by a series of tsunami waves. Tide gauges across the Pacific Ocean, the Atlantic and the Indian oceans recorded significant sea-level changes related to the primary eruption.

We focus our presentation on the imprint of tsunami waves on the ionosphere. We make use of an extensive collection of Global Navigation Satellites Systems (GNSS) data recorded by multi-constellation GNSS receivers across the Pacific Ocean and beyond. The observation of tsunami-induced ionospheric signatures is made possible by the efficient coupling of tsunami waves with the surrounding atmosphere and the generation of internal gravity waves (IGWs). With the help of GNSS systems (Beidou, GPS, Galileo, GLONASS, QZSS), ionospheric disturbances can be monitored and observed by utilizing the Total Electron Content (TEC) derived from the delay that the ionosphere imposes in the electromagnetic signals transmitted by the GNSS satellites. We identify and characterize the ionospheric TEC signatures following the passage of the Tonga tsunami. We investigate the influence of known key ambient parameters such as the local geomagnetic field, the tsunami propagation direction, and the distance to the tsunami source on the amplitude of the observed signatures. Moreover, we correlate the detected tsunami-induced TEC signatures with sea level measurements to assess their tsunami origins. And we contrast the identified TEC signatures in the Pacific Ocean with their analogs induced by the tsunami triggered by the Mar. 4, 2021 8.1 Mw Kermadec Islands earthquake. Both events took place relatively in the same geographical region, with the former being less complex (no meteo-tsunami, shorter duration, and about one order of magnitude smaller in amplitude). Finally, we provide estimations of the tsunami amplitude at the ocean level in the areas crossed by GNSS radio signals, some of them not covered by open ocean sea-level sensors (DART buoys).
World-wide gravity and pressure signals detected during the eruption at Hunga-Tonga.
Authors: Jousset Philippe , Hinderer Jacques , van Camp Michel , Güntner Andreas , Wziontek Harmut , Carbone Daniele , Krawczyk Lotte
Published: March 2022

The excitation of long-period signals has been reported for large eruptions such as El Chichon (1982) and Mount Pinatubo (1991).

We report on series of pressure and gravity signals associated with the series of violent explosions at the Hunga-Tunga eruption, on 14-15th January 2022 at different locations and set-up configurations.

We present records from various stations all over the world. Those stations have different set up and local configurations.

At most stations, gravity signals records reveal clearly surface waves associated to the main eruption at ~4:30, 15th January and pressure wave up to Iceland.

We analyze similarity and difference in the signals in association with the location and the station configurations
A reappraisal of explosive-effusive silicic eruption dynamics
Authors: Wadsworth Fabian B. , Llewellin Edward W. , Vasseur Jérémie , Gardner James E. , Tuffen Hugh
Published: March 2022

The controls on the style of silicic eruptions – hazardously explosive, more gently effusive, or hybrid explosive-effusive – are poorly constrained. Current models invoke escape of gas through a connected foam, or through fractures, as the primary mechanism for the transition from explosive to effusive eruption. We propose a new model, in which hybrid and effusive silicic eruptions are typically explosive at depth, but the clastic products of this 'cryptic fragmentation' sinter and weld in the conduit to produce coherent lava at the surface. Drawing on numerous case studies of natural textures within eruptive products and dissected conduits, we show that effusive silicic eruptions are best interpreted as being the welded, squeezed-out remnant of ongoing or recent subsurface explosive behaviour. We demonstrate that effusively erupted lavas have microtextures diagnostic of a welding/sintering genesis and are comparable with those found in rheomorphic and welded ignimbrites. All eruptive products share pore network geometries and associated mechanical and hydraulic property-porosity relationships that are consistent with models for sintered materials. We conclude that silicic lava is generally clastogenic, and that, after it is sinter-assembled, it may undergo gas-driven fracturing that produces lava plug-cutting tuffisites (closed fractures filled with sintered particles), and sintered pyroclasts (from ash- to bomb-sized). At some sites (e.g. Volcán Chaitén 2008), the first material to be extruded from the vent is a pyroclastic rubble similar texturally to the volcanic bombs from the same site. We propose therefore that the shallow conduit is filled with pyroclastic and lithic rubble; a volume that variably compacts over time to produce a plug of densified lava. Envisaging the shallow conduit as a compacting rubble pile instead of a coherent magma-filled pipe or crack leads us to posit that the explosive-effusive transition is a blurred behavioural switch controlled by the competition between material supply at the underlying fragmentation front, and shallow particle capture, welding and lava production above. This framework has broad top-down implications for geochemical and geophysical predictions of shallow silicic volcanism, which we will explore in this presentation.
Systemic Design Approach: A Framework for a resilient urban transition
Authors: Boskovic Stanislava , Puchol-Salort Pepe , Krivtsov Vladimir , Mijic Ana
Published: March 2022

Cities are open living systems, which rely on the confluence of multiple layers of infrastructure and corresponding services. The interaction among these components is made even more complex by the demands of businesses and governments, together with constraints arising from ecological and environmental considerations. Climate change-related phenomena are putting an enormous strain on cities’ infrastructure, basic services, human livelihoods, public health and well-being. In many parts of the world concerns mount in regard to the scarcity of resources and growing risk of natural disasters (heat waves, urban flooding, droughts).  The converse also holds true, cities are major contributors to climate change through greenhouse gas emissions, notwithstanding other sources of pollution. This, together with the increase in urban growth and urbanization, results in an expansion of urban hazards - including water pollution, disease spread and issues with food security. Despite these pressing issues, we are witnessing an almost paradoxical mismatch between the needs of future cities and the practices currently used in numerous urban projects. A wholesale re-thinking of existing urban design methods at systems level (Systemic Design), is therefore not only necessary, but also provides significant opportunities to explore critical aspects of Blue-Green Infrastructure (BGI) and systematic assessment of possible future scenarios of different scales (local, urban, regional…). Nature-based solutions (NBS) are at the very core of the conception and development of BGI and provide a range of ecosystem services including alleviation of flood risk, mitigation of climatic effects, increase in biodiversity and amenity values, improvements in water quality, and further, rather more intangible benefits related to the residents’ health and wellbeing.

In this work we provide a systemic design as an innovative and integrated approach, based on ecology and ecological design, which introduces the systematic context analysis (environmental, climatic, historic…).  A GIS-based mapping of the context, produced in relation to the functional purpose, can give us synthetic prospects to better understand the potential effectiveness of BGI solutions (design options) in relation to their wider ecosystem. The systemic design approach allows an examination of possible steps to reduce actual cities vulnerability and to explore the main drivers of urban development, climate change mitigation and urban resilience. In this way, the systemic design approach also supports decisions for further planning and anticipates actions for the management of the multifaceted hazards of the entire urban system.
Practical measurements of water stable isotopes in tree stems and soils using conservative water vapor storage
Authors: Magh Ruth , Gralher Benjamin , Herbstritt Barbara , Kübert Angelika , Lim Hyungwoo , Lundmark Tomas , Marshall John
Published: March 2022

The interest of inferring plant water uptake depths/patterns and water movements through the soil matrix grew tremendously in recent years and, studies have shown the use of in-situ measurement systems based on laser absorption spectroscopy making e.g. plant or soil water stable isotope datasets available on-site and in real-time. However useful, in-situ systems are limited to sites with power supply and require constant care.

We tested, first in the lab and then in the field, a method for equilibrating, collecting, storing, and finally analysing water vapour for its isotopic composition. We used a vapour storage vial system (VSVS) that relies on in-situ sampling, using a pump and a flow meter powered through a small battery into crimp neck vials with a double coated lid, and measuring the samples in a laboratory. We tested the utility of the sampling method and the reliability of the VSVS to faithfully store the isotopic composition of its content by sampling a range of water vapour of known isotopic compositions (from -95 to 1700‰ for δ2H) and measuring the isotopic signature after the storage period. Samples for the field trial were taken in a tracer pulse chase experiment in a boreal forest in Northern Sweden.

We were able to prove the utility of the sampling method within defined uncertainties (0.6 to 4.4‰ for δ2H and 0.6 to 0.8‰ for δ18O) for natural abundance. For in 2H-enriched samples the range was adapted to higher uncertainty. We detected a small change in the isotopic composition of the sample after a longer storage period, which was consistently greater for oxygen but correctable by linear models.

Our method has the potential to combine the best of two worlds: sampling in-situ in high spatial or temporal resolution while measuring in the laboratory, could solve problems with location biases and give the community a tool that is not only cost-efficient but also easy to use while all components are commercially available.  
Revisiting the closure of the Mediterranean sea level budget
Authors: Moreira Lorena , Cazenave Anny , Marcos Marta
Published: March 2022

Over the 20th century, the global mean sea level has risen by about 20 cm, with about half of this amount since the early 1990s, as evidenced by satellite altimetry-based sea level records. Moreover, the rising of the oceans is not uniform and varies regionally. In some areas, the rate of sea level rise is up to 3 times the global mean, as a result of regional changes in steric sea level, ocean circulation-related mass redistribution and regional sea-level patterns caused by past and present-day land ice melt and terrestrial water storage change. The understanding of regional sea level changes is crucial for local sea level projections and coastal management strategies. In this study we focus in the Mediterranean Sea, as its coasts are home to large population centres and important infrastructures in low-lying areas. We estimate the contributions of the level budget components using altimetry-based sea level, Argo-based steric sea level and GRACE-based ocean mass for the period 2003 to 2020. In addition, we investigate the influence of some climate indices as potential drivers of the sea level variability in the Mediterranean Sea.
The challenge of measuring rock moisture: A laboratory experiment using eight types of sensors
Authors: Weiss Tomáš , Sass Oliver
Published: March 2022

Weathering is a key component of the geomorphological process system and poses a major threat to cultural heritage, such as building structures and rock art sites. Since almost all rock decay is enhanced by the presence of water, research on moisture content and flow is crucial to understanding weathering processes. Nevertheless, measuring rock moisture and its fluctuations is difficult as there is no universally used sensor that meets the requirements of non-destructiveness, reliability, repeatability, and applicability at field sites. Therefore, this work aims to evaluate several moisture measurement techniques under different natural conditions and to provide recommendations for their use. We tested seven types of methods (1D resistivity, 2D resistivity, TDR, borehole humidity, microwave reflectance, IR thermography, and uranine probes) under controlled conditions in a sandstone block that was subject to a slow wetting and drying cycle and to a series of freeze-thaw cycles.

Overall, the methods measuring dielectric properties of the rock (TDR, microwave) can be generally recommended for their reliability, repeatability, and applicability at field sites. Precise observation of moisture dynamics in deeper subsurface however remains a challenge, especially when moisture contents are close to drier states. Therefore, to get reliable water content data, it is vital to drill inside the rock rather than to use surface sensors, which are particularly sensitive to surface moisture and surface roughness. Nonetheless, out of the non-destructive surface methods, dielectric sensors using the microwave spectrum with a greater penetration depth (>10 cm) should be considered as they have the advantage of interacting the transmitted signal into a larger volume of material, therefore making the influence of surface less pronounced. Furthermore, the use of electrical resistance methods is less recommended because of mainly two factors: they need to be calibrated for each sensor pair, and they are prone to erroneous measurements in the presence of salts. Concerning the other methods, probes using a reactive dye, and borehole humidity sensors can be used to determine the location of the subsurface evaporation front where salt crystallisation takes place, and the IR imaging for studying evaporation dynamics needs either highly controlled environment or continuous measurement. In conclusion, this work provides new insights into rock moisture measurements and further research should focus on subsurface moisture measurements and the improvement and calibration of available techniques.
Mass-Conserving Thermal Structure for Slabs in Instantaneous Models of Subduction
Authors: Billen Magali , Fraters Menno , Babin Magalie
Published: March 2022

Subduction is driven by difference in mass between the sinking plate and the surrounding mantle. The deformation calculated in numerical models of subduction is strongly dependent on the magnitude of the mass difference. The mass difference depends on the temperature of the slab. As the tectonic plate sinks it heats up, but it also cools down the surrounding mantle. The amount of heating and cooling is determined by conservation of thermal energy. Because the temperature also determines the thermal mass, conversing thermal energy also leads to conserving mass. For some studies, models of subduction are made to match the present day structure of a sinking plate. In this case, the temperature is defined to follow the observed geometry. In some previous studies, the temperature structure did not explicitly enforce conservation of energy or mass, and thus the density of the slab was not physically consistent, which is added source of uncertainty when analyzing the resulting flow and sensitivity of model results to mantle and slab rheology. Here we present a mass-conserving thermal structure for slabs that also creates a smoothly varying temperature structure. The thermal structure is based on a 1-D half-space cooling model (bottom) and an infinite space cooling model (top). It uses the age of the plate at the trench to determine the initial mass anomaly of the slab. The sinking velocity modifies the rate of heating and migration of the minimum temperature into the slab interior. The thermal model is calibrated against simple 2D subduction models in which the age and subduction velocity are held fixed. The new thermal structure has been implemented in the Geodynamic WorldBuilder (1), which can be used with different mantle convection software and is distributed as a plugin for ASPECT (2). Comparison of model results with the mass conserving slab thermal structure to the "plate" model from McKenzie (1970) is used to illustrate the differences in modeled results. References: 1. Fraters, M. R. T. et al., Solid earth, 2019. 2. Bangerth, W. et al., https://doi.org/10.5281/ZENODO.5131909, 2021.
What is triggering ice in mixed-phase clouds: A process analysison the importance of ice nucleation and sedimentation with ECHAM-HAM
Authors: Ickes Luisa , Neubauer David , Lohmann Ulrike
Published: March 2022

Mixed-phase clouds can be found at temperatures between 0 and -40°C and consist of supercooled cloud droplets and ice crystals. Their formation is triggered by different processes forming or introducing ice crystals in a supercooled cloud. Once ice crystals are present they grow at the expense of the cloud droplets due to the Wegener-Bergeron-Findeisen process, which causes a partial or complete glaciation of the cloud. Secondary ice processes can accelerate the glaciation.

In the global climate model ECHAM-HAM there are three different trigger processes, which introduce initial ice crystals into a supercooled cloud: heterogeneous ice nucleation, sedimentation of ice crystals from upper cloud layers, e.g. cirrus clouds, and vertical transport (vertical diffusion) of ice crystals. The aim of our study is to analyze the importance of each process in ECHAM-HAM. We investigated the role of all processes by conducting an ensemble of simulations where individual or combinations of processes are turned on or off. The outcome was analyzed with the factorial method using the supercooled liquid fraction of a mixed-phase cloud as a tracer for the microphysical structure. The analysis shows that sedimentation of ice crystals is crucial for mixed-phase clouds in ECHAM-HAM. Ice nucleation seems only to be an important trigger process if there are no ice crystals sedimented from above. However, even then sedimentation is important to distribute the freshly nucleated ice crystals within the supercooled cloud.
Evaluating uncertainties in modelled surface mass balance components of a mountain glacier
Authors: Rybak Oleg , Rybak Elena
Published: March 2022

The purpose of the research is to assess the influence of the random weather fluctuations on the estimates of the model-based surface mass balance (SMB) components of the mountain glacier. The common approach in the modeling studies is to use meteorological records (measured or modelled) – surface air temperature and precipitation rate – as weather forcing in numerical experiments. The results of the calculations are normally very sensitive to the parameter choice and the model should be carefully calibrated against measured SMB to obtain correct results. What is usually ignored within the frameworks of this approach is that forcing records at e.g. daily resolution contain internal weather variability which after being integrated by the model can yield in a random walk type trend of SMB.   

To evaluate uncertainty in SMB calculations we force an energy balance model of Djankuat glacier in the Central Caucasus with surrogate series of surface air temperature and precipitation rate. The surrogate series of several model decades duration each are produced by a stochastic weather generator WGEN basing on the observed meteorological series at the weather stations located nearby. In WGEN, precipitation events are simulated by a first-order Markov chain, and the intensity of precipitation is represented using independent gamma distribution. Air temperature is calculated by fitting the appropriate distributions and harmonic functions separately for wet and dry days. Seasonality is reproduced by an estimate of individual sets of model parameters for different periods of the year.

Statistical analysis of the generated ensemble of SMB components revealed that relative standard deviation (RSD) of SMB components (accumulation rate, melting, evaporation, melt water retention) vary within the limits 3-6%, but RSD of the specific mass balance is several times higher.

Our approach enables to filter out reaction of the modeled glaciers induced by the weather noise from systematic reply on climate change.

The reported study was funded by the RFBR and RS grant 21-55-10003.
Reconstructing upper ocean carbon variability using ARGO profiles and CMIP6 models
Authors: Turner Katherine , Williams Richard G. , Katavouta Anna , Smith Doug M.
Published: March 2022

Historically, ocean carbon content has been poorly sampled due to the logistical difficulties inherent in carbonate chemistry measurements.  As a result, global products of ocean carbon content observations have been restricted to calculate climatologies or long-term trends. Recent innovations with machine learning have provided for observational reconstructions of multidecadal and interannual carbon variability. In this work, we create a complementary method for reconstructing historical carbon variability by drawing upon the Ensemble Optimal Interpolation method used for reconstructing historical ocean heat and salinity [1-3]. Ensemble Optimal Interpolation draws upon first-order relationships between variables and use covariances from model ensembles to propagate information from data-rich to data-sparse regions.

We test our method by conducting synthetic reconstructions of upper ocean carbon content using ARGO-style sampling distributions with CMIP6 ensemble covariance fields. Sensitivity tests of local carbon reconstructions suggest that around 50% of ocean carbon variability can be reconstructed using temperature and salinity measurements. Expanding the synthetic reconstructions to include irregular sampling consistent with ARGO profile locations results in a similar capacity to reconstruct ocean carbon variability, as the increased information provided from multiple sampling locations compensates for the propagation of errors within the CMIP6 covariance fields.  Our initial results indicate that the first-order relationships between temperature, salinity, and carbon can be used to describe a substantial proportion of historical carbon variability. In addition to showing promise for a new historical reconstruction complementary to current products, our work emphasises the important links between hydrographic and carbon variability for much of the global ocean.

 

References

[1] D. M. Smith and J. M. Murphy, 2007. "An objective ocean temperature and salinity analysis using covariances from a global climate model," JGR Oceans.

[2] L. Cheng, K. E. Trenberth, J. T. Fasullo, T. Boyer, J. T. Abraham and J. Zhu, 2017. "Improved estimates of ocean heat content from 1960 to 2015," Science Advances.

[3] L. Cheng, K. E. Trenberth, N. Gruber, J. P. Abraham, J. T. Fasullo, G. Li, M. E. Mann, X. Zhao and J. Zhu, 2020. "Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle," Journal of Climate.
Qualification of the efficiency of a dam dredging by mapping the sediment plume with adcp acoustic backscatter
Authors: Hauet Alexandre , Scheepers Hélène , Lepa Dominique , Capon Bruno
Published: March 2022

EDF is the largest producer of hydroelectricity in Europe and France, with about 640 dams and an installed capacity of about 20GW. Sedimentation in dam reservoirs is a paramount issue for EDF, including impacts on electricity generation, on dam stability, on spillway discharge capabilities and operation of bottom gates, and on the sediment starvation downstream.

This study focusses on EDF’s dam of Chambon, in the French Alps. In order to guarantee the proper operation of the Chambon dam's outlet bottom gate (the main safety device) between 45 and 55,000   m3 of fine sediments upstream of this gate have to be cleaned out and thus create a stable release zone.  The dredging was conducted by a dilution-pumping method that consists in pumping the sediment deposited in the area upstream the bottom gate, and released them upstream the power-plant intake so that they can transit through the turbines and return to the river downstream to be diluted. The outlet of the pipe dredge was stalled several meters in front of the water intake in order to entrain the fine sediment plume while allowing sand and gravel (which can create serious damage to the turbine) to settle before the intake.

To verify the efficiency of this method, and to ensure that the fine sediments were well entrained in the power-plant intake, adcp measurements were conducted to map the acoustic backscatter intensity that reflects the sediment concentration. A TRDI RioGrande 600 kHz was used, tilted by 20° in order to point the Beam 1 to the Nadir and avoiding side-lobe perturbation close to the bottom. The acoustic backscatter from Beam 1 is used as a proxy of sediment concentration, in a qualitative approach (without estimating the sediment concentration in g/L), in order to map areas of no-, low- or high- sediment concentration.

The measurements show that the release of sediment from the dredging nozzle is highly variable over time, and causes sediment puffs which are diffused towards the free surface and laterally downstream. The sediment plume is homogenized in the body of water, then plunges towards the power-plant intake where it is entrained. 
Causal drivers of eastern Mediterranean tropospheric circulation during boreal summer
Authors: Tyrlis Evangelos , Di Capua Giorgia , Matei Daniela , Coumou Dim , Donner Reik
Published: March 2022

During boreal summer, large scale subsidence and a persistent northerly flow, known as the Etesians, characterize the tropospheric circulation over the eastern Mediterranean, respectively bringing clear skies and mitigating the emergence of heat waves. Atmospheric drivers over both South Asia and the North Atlantic have been proposed to influence the intraseasonal variability of subsidence and Etesians over the eastern Mediterranean. Here, we employ Causal Effect Networks, obtained by applying the Peter and Clark Momentary Conditional Independence (PCMCI) causal discovery algorithm, to identify causal precursors of subsidence and Etesians in a set of atmospheric fields. We find that both wave train activity over the North Atlantic/North American region and convective activity over the northern Indian Ocean are causally related to the 3-day average 850 hPa meridional wind variations over the eastern Mediterranean at a lag of 3-to-6 days. For 3-day average 500 hPa vertical wind velocity, causal precursors over the Middle East and Arabian Sea similar to those identified for the Etesian are found. We further explore in detail the different nature of the causal precursors to the Etesians and subsidence over the eastern Mediterranean by applying varying averaging in the variables representing the involved phenomena.
‘SaltGiant’ drilling in the Sorbas Basin: Structural, Petrophysical and Geochemical characterization of the Messinian Salinity Crisis deposits
Authors: Raad Fadl , Pezard Philippe , Viseras Cesar , Sierro Francisco J. , Yeste Luis M. , Aguila Javier J. , Jerez Paula , Schleifer Andrea , Meneghini Fabio , Bellezza Cinzia , Lofi Johanna , Camerlenghi Angelo , Aloisi Giovanni
Published: March 2022

The Late Miocene deposits in the Sorbas Basin (Spain) have been of an extreme importance in the understanding of the Messinian Salinity Crisis (MSC) events (5.97-5.33 Ma). They consist of four formations. The pre-crisis Abad marls topped by the evaporitic Yesares gypsum member, followed by two non-evaporitic units known as the Sorbas and Zorreras members. Those deposits have been widely explored and studied thanks to the numerous outcropping sections in the basin.

The ‘SaltGiant’ European Training Network held a training school in October 2021 in the Sorbas Basin, where four boreholes (named SG0, 1, 2 and 3) covering most of the Messinian Salinity Crisis sequence, were drilled, cored and logged in this context along an overall thickness of about 175 m. The drillings took place inside and in the vicinity of the Torralba gypsum mine. It allowed for the first time in the scientific non-industrial domain, access to a continuous and non-outcropping succession of the Messinian deposits in the Sorbas basin. In addition to the recovered cores, borehole geophysical data were obtained from the four holes and digital images of the area were collected with a drone. Prior to the drilling, an OBO (Outcrop / Behind Outcrop) workflow was followed, which will allow integrating the outcrop and subsurface data by combining the 3D geometry of geobodies with geophysical information.

Optical borehole wall images provide mm-scale images of the borehole walls, highlighting the sedimentological and structural characteristics of the deposits. Downhole geophysical measurements included acoustic velocity, electrical resistivity and natural spectral gamma ray, which allowed determining the petrophysical characteristics of the penetrated lithologies. In addition to the petrophysical logs, a Vertical Seismic Profiling was performed in holes SG2 and SG3, including a multi-offset VSP survey in hole SG3.

The petrophysical characterization of the Messinian deposits will provide a reference case study for the lithologic characterization of MSC deposits in the subsurface elsewhere. VSP analysis provided an in-field preliminary seismic velocity evaluation in the encountered formations. Preliminary results confirm the astronomical precession-driven cyclicity observed elsewhere in the Messinian gypsum. Further processing and analyses of the large amount of acquired data will lead to identifying the astronomical and possibly higher-frequency cyclicity in the post-evaporitic deposits in the Sorbas member.