bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Path of Diurnal Internal Tide in the Northwestern Pacific Controlled by Refraction and Interference
Authors: Wang Yang , Xu Zhenhua , Hibiya Toshiyuki , Yin Baoshu , Wang Fan
Published: March 2022

The diurnal internal tides contribute nearly a quarter of global baroclinic tidal energy, while their roles in shaping spatiotemporal inhomogeneity of tidal energy field are not well known. Here, based on a combination of observation-supported numerical simulation and theoretical analyses, we clarify the combined and relative contributions of β refraction, subtidal circulation refraction and multi-wave interference to the long-range radiation and dissipation maps of diurnal internal tides in the northwestern Pacific. The diurnal tidal beams are primarily emanated from the Luzon Strait (LS) and Talaud-Halmahera Passage (THP). The β refraction effect, which is more pronounced at higher latitudes, refracts the mean path of LS tidal beam equatorward by ~40° when it arrives at the deep basin, consistent with previous altimeter observations. A second refraction effect by subtidal circulation with seasonal variability deflects the mean beam path by ~10°. Multi-wave interference of tidal beams from the LS and THP further enhances the inhomogeneous pattern, resulting in enhanced and reduced energy flux beam branches with distinct vertical structures in the west Mariana basin. A modified line-source model and theoretical ray-tracing analysis can well explain the effects of refraction and interference. Internal tidal dissipation map in the deep basin coincides well with the inhomogeneous and spreading radiation paths. The mechanism characterization of the world’s most energetic diurnal internal tides in the northwestern Pacific could improve our understanding of global baroclinic tidal energy redistribution and associated tidal mixing parameterization in climate-scale ocean models.
Using deep learning to improve the spatial resolution of the ocean model
Authors: Hromov Ihor , Shapiro Georgy , Ondina Jose , Sharma Sanjay , Bruciaferri Diego
Published: March 2022

For the ocean models, the increase of spatial resolution is a matter of significant importance and thorough research. Computational resources limit our capabilities of the increase in model resolution. This constraint is especially true for the traditional dynamical models, for which an increase of a factor of two in the horizontal resolution results in simulation times increased approximately tenfold. One of the potential methods to relax this limitation is to use Artificial Intelligence methods, such as Neural Networks (NN). In this research, NN is applied to ocean circulation modelling. More specifically, NN is used on data output from the dynamical model to increase the spatial resolution of the model output. The main dataset being used is Sea Surface Temperature data in 0.05- and 0.02-degree horizontal resolutions for Irish Sea. 

Several NN architectures were applied to address the task. Generative Adversarial Networks (GAN), Convolutional Neural Networks (CNN) and Multi-level Wavelet CNN. They are used in other areas of knowledge in problems related to the increase of resolution. The work will contrast and compare the efficiency of and present a provisional assessment of the efficiency of each of the methods. 
Spatial Correlation between Intraplate Volcanism and Thin Lithosphere in the Circum-Mediterranean: New Evidences from Surface Wave Tomography and Thermomechanical Modelling
Authors: El-Sharkawy Amr , Hansteen Thor , Clemente-Gomez Carlos , Fullea Javier , Lebedev Sergei , Meier Thomas
Published: March 2022

During the Cenozoic, the Circum-Mediterranean and its periphery have experienced extensive and widespread anorogenic igneous magmatism that reflects the response of the upper mantle to the geodynamic evolution of this area. The exact origin of the volcanic activities and its relation to the underlying thin lithosphere especially in the continental areas have been long-lasting debated. We investigate the structure of the Mediterranean lithosphere and the sub-lithospheric mantle by surface waves that are mainly sensitive to the 3-D S-wave velocity structure at those depths. A high-resolution tomographic study based on automated broad-band measurements of inter-station Rayleigh wave phase velocities down to about 300 km depth is presented. We identify shallow asthenospheric volumes, characterized by low S-wave velocities between about 70 km and 250 km depth, and distinguish between five major shallow asthenospheric volumes in the Circum-Mediterranean: the Middle East, the Anatolian-Aegean, the Pannonian, the Central European, and the Western Mediterranean Asthenosphere volumes. Remarkably, they form an almost continuous circular belt of asthenospheric areas interrupted only by the thick Permo-Carboniferous oceanic lithosphere in the eastern Mediterranean.

Integrated thermochemical modelling using surface wave phase velocities, topography, and heat flow as constraints indicates a remarkable variability of the lithospheric thickness across the area. Thick lithosphere is found in the Paris Basin, the East European Craton, and the eastern Mediterranean whereas thin lithosphere is found in areas of pronounced negative shear-wave anomalies at depth between 70 km and 200 km. Cenozoic intraplate volcanic fields are located in areas with thin lithosphere underlain by shallow asthenosphere. Thus, anorogenic intraplate volcanism in the Circum-Mediterranean appears to be associated with thin and hot lithospheric regions and low S-wave sublithospheric velocities. The distribution and properties of the shallow asthenosphere volumes in the region are discussed and related to the spatial-temporal occurrence of intraplate as well as subduction related volcanism in the western Mediterranean, central Europe, the Pannonian Basin, the Anatolian region and the Middle East.
Regional landslide susceptibility mapping using tree-based machine learning techniques
Authors: Mitchell Hamish , Brennan James , Burke Claire , Kluza Kamil , Ramsamy Laura , Zeneli Markela
Published: March 2022

The identification of assets susceptible to landslide-related damage is critical for planners, managers, and decision-makers in developing effective mitigation strategies. Recent applications of machine learning and data mining methods have demonstrated their use in geotechnical assessments including the spatial evaluation of landslide susceptibility.

At Climate X, we utilise tree-based machine learning techniques alongside geographic information system and remote sensing data to map landslide susceptibility across Great Britain. We compile several conditioning factors—including topographic, subsurface, land use, and climate-related data—and combine them with over 18,000 landslide instances, recorded in National Landslide Database. We evaluate the capabilities of several techniques including, decision tree, bagged tree, random forest, and balanced random forest (applies random undersampling of the majority, non-landslide class) for landslide susceptibility modelling. Several performance evaluation indices (area under receiver operator characteristic curve (AUC), precision, recall, F1 score) were used to assess and compare the performance of models. We show that the random forest is the most accurate of our models with an AUC of ​94.7%. Our results demonstrate that tree-based algorithms form a robust method to analyse regional landslide susceptibility and provide new insights into locations susceptible to landslide-related damage across Great Britain.
Soil sampling for variable-rate fertilization using spatial clustering
Authors: Minařík Robert , Žížala Daniel , Skála Jan , Kraus Michal , Lukas Vojtěch
Published: March 2022

Clustering is still an active method of soil sampling. The defined clusters not only can direct soil sampling for digital soil mapping, but also can serve as management zones for variable application of inputs based on soil sample analysis.  This study compares a nonspatial and spatial fuzzy clustering approach of management zones delineation enabling sampling design for both site specific and zonal fertilization. An actual yield potential and a bare soil composite computed from Sentinel-2 imagery featuring soil texture serve as covariates for clustering analysis ensuring a high interpretability of results. The minimum area of clusters and the number of sampling locations is defined by a user. The optimum number of constrained clusters is selected for every field based on silhouette index calculation ensuring the variable soil sampling density according to the variability of field conditions. Soil sampling locations were selected using shortest weighted distances to centroids of clusters or randomly. The results showed that nonspatial fuzzy clustering worked only for relatively homogenous fields with low number of clusters. For highly heterogeneous fields, the formed clusters were not spatially compact, because no spatial weight matrix was used. However, setting the minimum cluster size equal or greater than 1ha significantly improved the clusters compactness for heterogeneous fields even using nonspatial approach. The application of spatial approach improved the cluster compactness of heterogenous fields regardless to cluster size which makes this approach more universal.

The research has been supported by the project no. QK21010247 "Management optimization of unbalanced fields by means of digital soil mapping and soil moisture changes monitoring in order to stabilize the achievable yield" funding by Ministry of Agriculture.
Seismic shaking scenarios for city of Dubrovnik, Croatia
Authors: Latečki Helena , Sečanj Marin , Dasović Iva , Stipčević Josip
Published: March 2022

The south-eastern part of Adriatic Sea is seismically highly active region where numerous strong events have occurred in historic times. Among these, the most significant is the infamous Great Dubrovnik earthquake of 1667. This event, whose magnitude was estimated to be in the vicinity of Mw 7.0, caused widespread devastation in the whole region. More recently, a large Mw 7.1 event happening in 1979 in Montenegro caused extensive damage along 100 km of coastline, including the area around Dubrovnik. From this it is obvious that the city of Dubrovnik is seismically highly vulnerable and that there is an acute need to better understand possible consequences if an event of such a magnitude would happen today.  
 
One of the major steps in reducing the seismic risk in any region is to simulate seismic shaking and to evaluate expected ground motion for plausible earthquake scenarios. Therefore, our aim in this work is to create several earthquake scenarios for the city of Dubrovnik and estimate seismically most endangered parts of the region. For that purpose, we first assemble a detailed 3D crustal model which includes information on physical parameters of interest (velocity and density) and which reflects all the important geological features of the studied area. Then, we test whether the model is suitable for simulation by computing and comparing broadband seismograms against the recorded data of several moderate events. We validate the results by assessing the goodness of fit for different metrics describing ground-motion. Next, by combining seismic and geophysical data, we define the geometry of the main active faults and parameters required for the rupture model used in the simulation. We calculate synthetic waveforms on a dense grid and then extract intensity measures to determine the expected ground-motion features of a strong seismic event such was The Great Dubrovnik earthquake.
Global Snow Water Equivalent for continuous groundwater monitoring from space: uncertainties, evaluation, and application
Authors: Kosmale Miriam , Luojus Kari , Ikonen Jaakko , Venäläinen Pinja
Published: March 2022

Sufficient groundwater resources are unarguably essential for human populations all over the world. With a contribution of over 30% to freshwater reserves in the global hydrological cycle, it is important to increase the capacity of the currently sparse groundwater monitoring network. Spatially and temporally continuous monitoring of groundwater as an Essential Climate Variable (ECV) can be realized with remote sensing techniques. Within the “Global Gravity-Based Groundwater Product” G3P-project (www.g3p.eu), gravimetric satellite missions GRACE and GRACE-FO are applied for global groundwater monitoring. Groundwater derived from gravimetric measurements require detailed knowledge of all continental water compartments, which are contributing to the total water storage variations.

Within the G3P project the Finnish Meteorological Institute is producing a global gap-filled Snow Water Equivalent (SWE) product that describes the snow compartment for global groundwater estimation. The product complements remote sensing-based information with model-based data for regions where remote sensing can’t observe SWE on global scale.

The production of SWE from long-term satellite observations covering the full GRACE and GRACE-FO mission period from 2002 to 2021 are investigated. The Finnish Meteorological Institute efforts within the Copernicus Land monitoring service and ESA frameworks ensure operational Near-Real-Time information on SWE for the Northern hemisphere. Microwave and optical remote sensing sensor techniques are the basis for the SWE monitoring services. Validation with in-situ reference data is important in understanding product accuracy. Pixel-level uncertainties provided with the snow product support efforts on groundwater estimation. Model- and remote sensing-based SWE are evaluated on various regional scales.  As part of the new Gravity-Based Groundwater Product G3P, global Snow Water Equivalent products will be presented and discussed.
The effect of drought and temperature extremes on burned area in Southeastern Australia
Authors: Páscoa Patrícia , Gouveia Célia , Russo Ana , Ribeiro Andreia
Published: March 2022

Natural hazards often result from interacting physical processes across a wide range of spatial and temporal scales. Namely, the occurrence of heatwaves and droughts increases the risk of wildfires, with recurrent extensive human, ecological and economic losses being reported throughout the world. In Australia, several extreme bushfires have occurred following severe droughts and heatwaves, namely the Black Saturday bushfires in 2009 and the extreme bushfire season of 2019-2020.

In this work, we analyze the relation between fire occurrence, drought conditions, and temperature extremes in southeastern Australia for the period 1982-2018 and considering the months between December and February. Monthly burned area (BA) was retrieved from the FireCCILT11 dataset, with a spatial resolution of 0.25˚. The drought index SPEI was used to assess the drought conditions and was computed using monthly precipitation and temperature data from the CRU TS 4.05 database. The occurrence of temperature extremes was assessed using the index Number of Hot Days (NHD), which was computed using daily maximum temperature obtained from the ERA5 dataset.

The study area comprises pixels that have burned at least 25 times on these months. A correlation analysis was performed between BA and SPEI at time scales of 1, 3, and 6 months, and between BA and NHD. The influence of current and previous conditions on BA was assessed, by correlating BA with SPEI and NHD at the current month, and in the previous 1 to 3 months. The joint probability of BA, drought, and temperature extremes was also assessed, using copula functions.

The results show a negative correlation between BA and SPEI, and a positive correlation between BA and NHD. For previous months, the correlation is stronger between BA and SPEI, than for BA and NHD, pointing to an effect of the drought conditions on previous months, whereas the effect of temperature on BA is seen instantaneously. The probabilistic analysis shows a clear increase in the probability of BA exceeding the 80th percentile, given drought conditions, compared to non-drought conditions. A similar result was obtained for the case of extreme temperature.

Acknowledgements: This study was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under projects FIRECAST (PCIF/GRF/0204/2017) and Floresta Limpa (PCIF/MOG/0161/2019); and the 2021 FirEUrisk project, funded by the European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890.
Uncertainty and Efficiency in geothermal systems in heterogeneous aquifers
Authors: Zarlenga Antonio , Di Dato Mariaines , D'Angelo Claudia , Casasso Alessandro
Published: March 2022

Shallow geothermal systems represent a unique opportunity for heating and cooling of buildings with green energy and low operational costs.

Efficiency of  geothermal system is strictly related to the local subsurface flow field that moves water and energy; given the great spatial variability of hydrological and thermal properties in the subsurface environment a reliable assessment of the geothermal system efficiency requires a probabilistic approach that takes into account the uncertainty on the predictions. 

Homogeneous domain and purely advective flow are typical hypotheses currently adopted in the design of geothermal systems, the aim of our research is to investigate how the variability of thermo-hydrological and engineering parameters impact the different heat transport dynamics and how they result in the GS efficiency.

The study adopt a Lagrangian description of the heat transport based on the travel time evaluation.

As application example we consider an open loop system made by a well doublet placed into a confined heterogeneous aquifer of constant thickness.

The efficiency of the system is evaluated considering lumped parameters, usually adopted in the GS deign, such as the water recirculation ratio or the first breakthrough time and introducing more effective descriptors such as the total breakthrough time curve or the temperature evolution at the abstraction well.

The analysis suggests that the first breakthrough time, the key parameter adopted in the GS design, decreases with heterogeneity, furthermore, the uncertainty associated with early arrivals increases with heterogeneity. Medium heterogeneity, on the other hand, has a very small impact on the recirculation ratio and on the long-term period, while the pumping rate and other geometrical parameters have a strong impact on its value.

Since well screens usually cross a short depth we perform a detailed analysis on the uncertainty related to the ergodicity issue. Results of a single realization can significantly differ from its ergodic counterpart. As a practical consequence, a thermal feedback occurring in a heterogeneous medium could significantly differ from the expected theoretical one.
Analysis of vegetation modelling uncertainties due to soil moisture stress during droughts
Authors: Gan Wenyao , Nóbrega Rodolfo , Prentice Iain Colin
Published: March 2022

Many model uncertainties results from parameter tuning to compensate for errors in model outputs. A number of studies have focused on the analysis of uncertainties in modelled gross primary production (GPP), particularly with regard to the representation of soil moisture stress. GPP is often overestimated by models during dry periods in water-limited regions, and this bias increases during drought events. Soil moisture stress functions are widely applied to correct this. However, soil moisture stress is not always the direct constraining factor on GPP, and the functions adopted by models do not correspond to accepted mechanisms. We have used eco-evolutionary optimality principles, via the so-called P model, to estimate carbon uptake at sites where leaf area index (LAI) was routinely measured. We used observational networks (including FLUXNET) and Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) data from satellites. By comparing modelled and observed GPP we determined whether there is a significant difference between model performance during the dry and wet seasons, or between energy- and water-limited sites. We found that the soil moisture stress function used in one version of the P models essentially compensates for uncertainties in fAPAR data from satellites, especially in grasslands and other areas subject to seasonal drought. This situation is problematic, since soil moisture is a driver or modulator of other ecosystem processes, including soil evaporation and runoff generation. A possible way forward involves implementing phenological components dependent on soil and atmospheric conditions. The new challenge this poses is to apply eco-evolutionary optimality principles to model the seasonal time course of LAI, which is often poorly simulated by complex ecosystem models.
Ecological flow in southern Europe: implementation in temporary rivers 
Authors: Leone Marianna , Gentile Francesco , Lo Porto Antonio , De Girolamo Anna Maria
Published: March 2022

The European Commission in 2015, as part of the Common Implementation Strategy (CIS), defined the Ecological Flow (EFlow) in natural surface water bodies as “a hydrological regime consistent with the achievement of the environmental objectives of the WFD in natural surface water bodies as mentioned in Article 4”. These environmental objectives refer to (i) non-deterioration of the existing status, (ii) achievement of good ecological status in natural surface water bodies, and (iii) compliance with standards and objectives for protected areas. The Report does not define a standard protocol for setting an EFlow but it provides some recommendations.

The approaches for determining the EFlow, which must be defined in the River Basin Management Plans, are grouped into four classes hydrological, hydraulic, habitat, and holistic method. However, few methods have been specifically defined for temporary rivers. Most of these waterways have been poorly monitored in the past. The lack of historical hydrological and biological data in natural conditions ("reference") further complicates the definition of the EF.

This work analyses the implementation EFlow in the European Member States in Southern Europe under Mediterranean climate with specific reference to temporary rivers, which are the most common waterways in Spain, Portugal, France, Greece, and Italy. Through an examination of the case studies reported in the literature, a critical review of the methodologies adopted in these EU Member States for setting an EFlow has been carried out.

Results of this study showed that although all States have integrated into their legislation the EFlow recommendations by the EC, in several cases its implementation is not enforced sufficiently and several difficulties still exist in setting an EFlow. Case studies where the EFlow implementation was specifically designed for temporary rivers are still very few and most of the applications are based on hydrological methods. The paucity of hydrological and water quality data is the most important limit in setting an EFlow.
Using Raman spectra of isotopically enriched transformation products to trace mineral reactions
Authors: King Helen E. , Živković Aleksandar , Ohl Markus , Plümper Oliver
Published: March 2022

Isotopic doping is a powerful tool to identify newly formed mineral phases during fluid-mediated mineral transformation reactions. In particular, Raman spectroscopy of isotopically doped minerals can reveal incorporation of the isotopes into the structure of the minerals themselves, rather than enrichment of a fluid within a pore (1). In fluid mediated mineral transformations, dissolution of the reactant mineral enables O isotope exchange between water and dissolved oxyanions (e.g., CO3). Incorporation of the isotopically enriched oxyanions can result in crystals with different isotopic enrichments if the rate of the exchange in the fluid occurs on a similar timescale to the duration of the experiment and the crystals form at different times. This means that the amount of isotopic enrichment can be used as an internal stop clock and demonstrates the relative timings of precipitation in ex-situ analysis (2). In this presentation we will use previous examples to explore how fluid-mediated mineral transformation reactions can be followed using isotopic enrichment traced with Raman spectroscopy, including new data after deformation experiments. Using new data obtained from in-situ analysis of 18O exchange into dissolved carbonate species we will also show the importance of the solution chemistry on exchange kinetics in the fluid. In addition, we will use density functional theory calculations to explore how the mineral structure may influence the isotopic signature obtained from the Raman spectra. 

(1) King H.E. & Geisler T. (2018) Minerals, 8. 158.

(2) King H.E., Mattner D.C., Plümper O., Geisler T., Putnis A., (2014) Crystal Growth & Design, 14, 3910.
The latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW in the American and eastern Asia-Australia sectors
Authors: Liu Jing , Zhang Donghe , Hao Yongqiang , Xiao Zuo
Published: March 2022

The ionosphere exhibits enhanced semi-diurnal lunitidal (M2) perturbations during sudden stratospheric warming (SSW) events, of which the manifestation and mechanism are not well documented and understood. We studied the latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW with total electron content (TEC) data in the American and eastern Asia-Australia sectors. Results show that the M2 perturbations in the two sectors all enhanced during the SSW. The largest M2 amplitudes in the Northern and Southern Hemispheres appear at about 15°N and 20°S geomagnetic latitudes, respectively, with stronger magnitude in the Northern Hemisphere. Also, M2 perturbations in the two sectors all extend to middle latitudes only in the Southern Hemisphere and show local maxima around 35~40°S geomagnetic latitudes. The similar latitudinal and interhemispheric variations of the low-latitude M2 perturbtations in the two sectors indicate that such variations may be mainly caused by the meridional wind modulation on the equatorial plasma fountain. Meanwhile, the longitudinal differences are also noticeable. The TEC M2 amplitude in the American sector is obviously larger than that in the eastern Asia-Australia sector, especially in the southern middle latitude. The M2 perturbations in the American southern middle latitude may be influenced by the combined effect of the zonal wind and local positive magnetic declination in the Weddell Sea Anomaly region.
3D Variational Full-Waveform Inversion
Authors: Zhang Xin , Zhou Muhong , Lomas Angus , Zheng York , Curtis Andrew
Published: March 2022

Seismic full-waveform inversion (FWI) produces high resolution images of the subsurface by exploiting information in full seismic waveforms, and has been applied at global, regional and industrial spatial scales. FWI is traditionally solved by using optimization, in which one seeks a best model by minimizing the misfit between observed waveforms and model predicted waveforms. Due to the nonlinearity of the physical relationship between model parameters and waveforms, a good starting model is often required to produce a reasonable model. In addition, the optimization methods cannot produce accurate uncertainty estimates, which are required to better interpret the results.

To estimate uncertainties more accurately, nonlinear Bayesian methods have been deployed to solve the FWI problem. Monte Carlo sampling is one such algorithm but it is computationally expensive, and all Markov chain Monte Carlo-based methods are difficult to parallelise fully. Variational inference provides an efficient, fully parallelisable alternative methodology. This is a class of methods that optimize an approximation to a probability distribution describing post-inversion parameter uncertainties. Both Monte Carlo and variational full waveform inversion (VFWI) have been applied previously to solve 2D FWI problems, but neither of them have been applied to 3D FWI. In this study we apply the VFWI method to a 3D FWI problem. Specifically we use Stein variational gradient descent (SVGD) method to solve the 3D Bayesian FWI problem and to obtain an optimised set of samples of the full posterior probability distribution. The aim of this study is to explore performance of the method in 3D, to assess the computational requirements and to provide useful information for practitioners. Our results demonstrate that the 3D VFWI is practical, at least for small problems, and can be applied to image the subsurface in reality.
The effects of grain size on semi-brittle flow in calcite rich rocks
Authors: Harbord Christopher , Brantut Nicolas
Published: March 2022

Grain size is in an important microstructural parameter affecting both brittle and plastic deformation processes. In the low temperature brittle regime, larger grain size materials typically have lower strength, whereas in the plastic flow regime smaller grain size materials tend to be weaker. It is not clear how grain size impacts at intermediate conditions where deformation of rock is accommodated by coupled brittle and plastic deformation processes.

To investigate the role of grain size in the semi brittle regime we deformed three calcite-rich rocks, spanning 3 orders of magnitude in grainsize (0.006-2 mm). A gas medium triaxial apparatus was used at a range of confining pressures (200-800 MPa) and temperatures (20-400°C), and samples were loaded at a constant axial strain rate (1×10-5 s-1). Axial measurements of P-wave speed were performed during tests in order to infer the in-situ microstructural state of the sample.

Nearly all tests show strain hardening behaviour after yield, typical of semi-brittle deformation, which is quantified using the hardening modulus (h = ∂σ/∂ε). Grain size has a first order control on rock strength, with yield stress and h following a Hall-Petch type relationship at all P-T conditions. For a given temperature, h is low at low pressure (200 MPa) and accompanied by large decreases in wavespeed, and h increases at high pressure (>400 MPa) whereas velocity decreases by a smaller magnitude. This suggests that, at low temperature, strain hardening is relieved by microcracking. At constant pressure, wavespeed decreases significantly at 20°C with progressive deformation, but remains nearly constant at 400°C indicating a transition from dominatly brittle to fully plastic deformation with increasing temperature, in some cases with little change in the macroscopic strength.

Given that both strength and strain hardening behaviour depend on grain size, our data suggests that grain size dynamically impacts the long term rheology of the crust. Larger grain sizes will broaden the depth distribution of the brittle ductile transition and result in a weaker peak crustal strength.
Ionosphere and Thermosphere Observations in the Context of Whole Atmosphere Modelling
Authors: Walach Maria-Theresia , Grocott Adrian , Orr Lauren , Feng Wuhu , Marsh Daniel , Aruliah Anasuya
Published: March 2022

Modelling the whole atmosphere from the surface to the ionosphere allows us to better forecast and understand our weather and climate. It is a scientific and computational challenge to model this complex system numerically with its many drivers and feedback loops. Recent efforts to improve whole atmosphere models include raising the altitude to incorporate improved representations of the ionosphere and thermosphere. The Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) is one of the most comprehensive numerical models, spanning the range of altitude from the Earth’s surface to the upper thermosphere (~700 km). WACCM-X can model the global ionosphere and thermosphere, whilst providing coupling between atmosphere layers through chemical, physical and dynamical processes. Using WACCM-X, we can explore the implications of this coupling for the climate and for the near space environment. 

The high-latitude ionosphere-thermosphere behaves dynamically during geomagnetically active times due to time-varying solar wind driving and internal magnetospheric dynamics. We present high- and mid-latitude observations from the Super Dual Auroral Radar Network, Incoherent Scatter Radars and Fabry-Perot Interferometers which observe the ionosphere-thermosphere system. We investigate observed plasma flows, which respond directly to solar wind driving, alongside WACCM-X model simulations which are nudged to a meteorological reanalysis dataset in the troposphere and stratosphere during a variety of solar storm conditions. We discuss these in the context of time-varying dynamics due to solar wind driving and investigate the expansion of the high-latitude convection to lower latitudes during geomagnetic storms. Our results show that the latitudinal expansion is not yet fully captured in WACCM-X and we discuss how this may be mitigated. We further show that during a geomagnetic storm, the differences between the WACCM-X ionospheric data and the observations by SuperDARN at high- to mid-latitudes may vary by up to ~20 kV for the electrostatic potential during a geomagnetic storm. This translates to an electric field difference of 25 mV/m and differences in the plasma drift velocities in excess of ~800 m/s.
Ice cliff mass-loss of debris-covered Trakarding Glacier, Rolwaling region, eastern Nepal Himalaya
Authors: Sato Yota , Buri Pascal , Miles Evan , Kneib Marin , Sunako Sojiro , Sakai Akiko , Pellicciotti Francesca , Fujita Koji
Published: March 2022

Glaciers in High Mountain Asia have been shrinking in the recent decades. They are a valuable indicator of climate change, and their meltwater plays an important role for regional water resources. Debris-covered glaciers, which are prevalent throughout the Himalayas, exhibit complex melt processes due to their heterogeneous surface.  Previous studies have demonstrated that ice cliffs disproportionally contribute to glacier melt, but their importance at the glacier scale has been quantified for only a few sites. In this study, we exploit measurements taken since 2016 on the lake-terminating Trakarding Glacier (27.9°N, 86.5°E; 2.9 km2 spanning 4,500–5,000 m a.s.l.; ~5% ice cliff cover), eastern Nepal Himalaya, to investigate the importance of cliffs for debris-covered ice melt at the glacier scale from a remote-sensing inversion and energy-balance modeling. We generated super-high-resolution (0.2 m) terrain data from aerial photographs (UAV and helicopter-borne photogrammetry) during 2018-2019 and manually delineated ~500 ice cliffs to derive surface velocity, elevation change, and specific mass balance, providing an observational estimate of ablation across the debris-covered tongue and attributable to ice cliffs. Further we employed a process-based 3D-backwasting model to estimate continuous ice cliff mass-loss over the study period. The model calculates the energy balance of ice cliff surfaces and reproduces their evolutions (cliff expansion, shrinkage, and reburial), based on the characteristics of the glacier surface and location of individual ice cliffs. This method, forced with in-situ meteorological and terrain data and evaluated against the observed changes, provides ice cliff mass-loss from the scale of individual features to the entire Trakarding Glacier.
A clay-based geopolymer in loess stabilization to water and wind soil erosion
Authors: Katra Itzhak
Published: March 2022

Soil erosion has environmental and socioeconomic significances. Most of the loess soils throughout the world are subjected to increased land uses such, which increased soil destruction and dust emission to the atmosphere. There is a distinguish interest in applications for dust control and soil stabilization. This study examines empirically the use of a metakaolin-based geopolymer for dust control and soil stabilization in a semi-arid loess soil that is subjected to land uses and erosional processes. The application of the geopolymer for dust control in comparison with common products (brine, bitumen, PVA) resulted with no soil erosion and dust emission by wind tunnel simulations. As a soil stabilizer, the geopolymer tested in this study provides remarkably good results in the tensile test. The most successful composition of the geopolymer, which is activation solution of sodium silicate and sodium hydroxide (NaOH) together with an addition of 30% metakaolin, obtained soil strength of 23900N after 28 days. The attempt to replace NaOH with lime (CaO) in the activation solution was far inferior to the original composition.
Shoreward Migration of the Shelfbreak Front in the Middle Atlantic Bight
Authors: Ryan Svenja , Gawarkiewicz Glen
Published: March 2022

The Northwest Atlantic continental shelf is home to one of the richest ecosystems in the world, however it is also among the fastest warming regions globally and experienced multiple temperature extreme events, termed marine heatwaves, in the recent decade. These ongoing changes pose a large challenge for the highly valuable fishing industry in the Northeast U.S.. The generally cooler and fresher shelf water is supplied by subpolar waters via the Labrador current, while offshore waters in the Slope Sea, that is the continental slope region bounded by the Gulf Stream and the shelfbreak, are of subtropical origin. Warm core rings shedding of the Gulf Stream transport warm and saline water but also nutrients shoreward and frequently cause cross-shelf intrusions when interacting with bathymetry. The boundary of the two water masses is the Shelfbreak Front and the foot of the front is climatologically found over the 100\,m isobath in the northern Middle Atlantic Bight. While marking a transition of physical properties, the front and its position has also large implications for fisheries as temperate species are found shoreward of the front and more tropical species remain offshore of the front in the warm, saline waters. Monitoring the frontal position is challenging and requires high-resolution sampling, however large and persistent diversions may be detectable in coarser and more sporadic observations. Using data from the Coastal Pioneer Array by the Ocean Observative Initiative along with recent observations obtained during research cruises on the continental shelf and satellite-based sea surface salinity, we assess indicators of the frontal position in recent years. In 2021 the front migrated tens of km inshore for multiple months resulting in irregularities for the regional fishermen. This migration was likely connected to the presence of multiple warm core rings in the Slope Sea, driving record temperatures over the slope and shelf. We address the question whether similar frontal shifts occur more frequently and discuss how these maybe connected to larger scale forcing such as a shifting Gulf Stream, a slowing Atlantic Meridional Overturning Circulation or changes in the supply of subpolar water to the shelf.
Decadal variability of rainfall extreme events in Senegal over the 20th century:observations and modelling
Authors: Badji Aissatou , Mignot Juliette , Mohino Elsa , Diakhaté Moussa , Gaye Amadou Thierno
Published: March 2022

The intraseasonal characteristics of rainfall are crucial in monsoon regions, in particular for
agriculture. Crop yields indeed depend on the rainfall seasonal amount, but also on other
intraseasonal characteristics such as the onset of the rainy season or the distribution of rainy days.
In the Sahel region, while the average amount of seasonal rainfall has been shown to be marked by
strong decadal variability over the 20 th century, the modulations of intraseasonal rainfall
characteristics has received less attention in the literature so far. In this study, we show that the
frequency and intensity of intraseasonal rainfall events in Senegal exhibit a marked decadal
variability over the 1918-2000 period, similar to that of mean seasonal rainfall in the Sahel during
the 20 th century, and in phase with the Atlantic Multidecadal Variability (AMV). The representation
of the decadal modulation of these rainfall indices is further investigated using the atmospheric
component of the IPSL-CM6 model forced by the historically observed SST. Preliminary results
show that the model represents fairly well the observed decadal modulation of these extreme events.
Thus, the model simulations allow an in-depth understanding of the associated mechanism.
How was the Bushveld Complex assembled? A search for cryptic layering in ICDP drillcores from the Main Zone
Authors: Trumbull Robert B. , Veksler Ilya V. , Nikonov Wilhelm , Rammlmair Dieter
Published: March 2022

The Main Zone of the Bushveld Complex in South Africa is the most voluminous but least studied part of the world’s largest igneous intrusion. Modal layering is poorly developed compared with the units above and below (Upper and Critical Zones, resp.), and most of the ca. 3000 meter-thick Main Zone consists of monotonous gabbronorite, occasionally grading into norite and anorthosite. An exception is the ultramafic “Pyroxenite Marker” near the top of the Main Zone, which is present regionally in the complex and represents a major event of magma recharge into the chamber. However, studies of drillcore through the Main Zone in the Bushveld Northern limb (Ashwal et al., 2005; Hayes et al., 2017) found evidence for layering by periodic variations in rock density at vertical length-scales of 40 to 170 m. This implies there were many more episodes of magma recharge than previously thought.

Our study in the Eastern Limb of the complex tests if cryptic layering in the Main Zone is a local phenomenon or is regionally developed like the Pyroxenite Marker. The first step, reported here, was a vertical profile of bulk density data (Archimedes method) for a 1450 m section of the upper Main Zone below the Pyroxenite Marker. Samples were taken at 1 to 5 m intervals and the results show several intervals of density variations at length-scales of 30 to 120 m, comparable to those previously described in the Northern Limb. Periodicity in density changes is not so well developed as in the earlier study, and we identified several 50 to 75 m intervals where density variations are below 0.05 g/cm3. The second step of the study will use multispectral and laser-induced breakdown spectroscopy (LIBS) scanning to provide modal mineralogy profiles of the same drillcore samples used for density measurement. After cryptic modal layering is documented in this way, follow-up petrologic-geochemical studies at the layer boundaries will aim to characterize the composition and temperature of the magmas involved.

For this project the Bushveld Complex Drilling Project (BVDP) provided access to the BH7771 borehole, donated by Impala Platinum’s Marula mine.

References:

Ashwal, L..D., Webb, S.J. and Knoper, M.W. (2005) S. Afr. Jour. Geol., 108, 199-232.

Hayes, B., Ashwal, L.D., Webb, S.J. and Bybee, G.M. (2017) Contrib. Mineral. Petrol., 172, 13.
Shoreline-crossing geomorphology of instable volcanic islands from a quantitative DEM analysis
Authors: Klein Elisa , Urlaub Morelia , Krastel Sebastian
Published: March 2022

Volcanic islands are known to be a source of many natural hazards associated with active volcanism. The processes leading to the instability of their flanks, however are less well understood. The movement of an instable volcanic flank occurs in either or both of two ways; slow sliding of several cm per year (i.e. Etna, Italy) and/or the catastrophic collapse of a large portion of the edifice (i.e. Anak Krakatau, Indonesia). The conditions and precursors leading to such events are often unknown.

The limited availability of high-resolution bathymetry data especially at the coast is often restricting the quantitative geomorphological investigation to the subaerial part of the volcanic island. It is essential, however, to include the entire volcanic edifice as instability affects the volcano from summit to seafloor. In this study, we test whether and in which way, the morphology of the volcanic edifice affects its instability.

We therefore combine openly available high-resolution bathymetric and topographic grids (50-150m grid spacing) to create shoreline-crossing DEMs of more than 25 volcanic islands in four areas (archipelagos of Hawaii, Canaries, Mariana Islands and South Sandwich Islands). Additionally, we define sections of equal angle (flanks) with the summit as the central point. Morphological parameters, such as area, volume, height from seafloor, slope etc. of both the entire volcano and each of the 8 flanks, respectively are derived from the DEM grids and inserted into a database. The statistical analysis of this data combined with the history of flank failure will shed light on the influence the morphology of a volcanic island has on its instability. This will lead to a better understanding of the processes involved in the movement of instable volcanic flanks.
Climate X: Projecting losses due to extreme weather events linked to climate change
Authors: Kluza Kamil ,   Climate X
Published: March 2022

Climate change brings unprecedented risks to the future stability of global financial systems and our society. Central Banks and Governments around the world have joined forces to shape new policy in response to risks driven by climate change. These regulations will require firms to proactively identify, model, quantify and manage climate-related risks for the first time.

Climate X have just completed their first of a kind Integrated Assessment Model evaluating asset-level impacts of climate-related hazards across all 22 million addressed buildings in the UK. Each building has a modelled probability, severity and a simple A-F climate rating as well as a projected loss under given scenario.  

Our geospatial core comprises of UK-specific physical risk models including flooding (pluvial, coastal, fluvial) and geohazards (subsidence and landslides). The models are at 90mx90m resolution feed UKCP18 climate scenarios of RCP8.5 and RCP2.6. Flood models are physics-based and reach a Critical Success Index (CSI) of 75%+. Geohazard models use a combination of DinSAR and machine learning modelling with 90%+ accuracy levels (measured by AUC).

Loss models combine the geospatial hazards with buildings’ exposure (square meterage) and respective vulnerabilities: age, use, material built etc. They then apply insurance-based damage curves to compute structure & content losses against building replacement costs.

 