bluuebunny/crossref_metadata_2025 huggingface dataset:
Detecting earthquakes in GNSS station coordinate time series using machine learning algorithms
Authors: Crocetti Laura , Schartner Matthias , Soja Benedikt
Published: March 2021

Earthquakes are natural hazards that occur suddenly and without much notice. The most established method of detecting earthquakes is to use a network of seismometers. Nowadays, station positions of the global navigation satellite system (GNSS) can be determined with a high accuracy of a few centimetres or even millimetres. This high accuracy, together with the dense global coverage, makes it possible to also use GNSS station networks to investigate geophysical phenomena such as earthquakes. Absolute ground movements caused by earthquakes are reflected in the GNSS station coordinate time series and can be characterised using statistical methods or machine learning techniques.

In this work, we have used thousands of time series of GNSS station positions distributed all over the world to detect and classify earthquakes. We apply a variety of machine learning algorithms that enable large-scale processing of the time series in order to identify spatio-temporal patterns. Several machine learning algorithms, including Random Forest, Nearest Neighbours, and Multi-Layer Perceptron, are compared against each other, as well as against classical statistical methods, based on their performance on detecting earthquakes from the station coordinate time series.
Integrating landslide susceptibility maps into warning models at regional scale in Italy
Authors: Pecoraro Gaetano , Calvello Michele
Published: March 2021

The importance of susceptibility maps in the initial phase of landslide hazard and risk assessment is widely recognized in the literature, since they provide to stakeholders a general overview of the location of landslide prone areas. Usually, the use of these maps is limited to support land use planning. However, many researchers have recently recognized that susceptibility maps may also be used to improve the performance and spatial resolution of landslide warning at regional scale and provide a better updating of hazard assessment over time. Indeed, landslides prediction may be difficult at regional scale only considering rainfall condition, due to the difference of the spatial and temporal distribution of rainfall and the complex diversity of the disaster-prone environment (topography, geology, and lithology). As a result, a critical issue of models solely based on rainfall thresholds may be the issuing of warnings in areas that are not prone to landslide occurrence, resulting in an excessive number of false positives. In this work, we propose a methodology aimed at combining a susceptibility map and a set of rainfall thresholds by using a matrix approach to refine the performance of an early warning model at regional scale. The main aim is the combination of rainfall thresholds (typically used to accomplish a dynamic temporal forecasting with good temporal resolution but very coarse spatial resolution), with landslide susceptibility maps (providing static spatial information about the probability of landslide occurrence with a finer resolution). The methodology presented herein could allow a better prediction of “where” and “when” landslides may occur, thus: i) allowing to define a time-dependent level of hazard associated to their possible occurrence, and ii) markedly refining the spatial resolution of warning models employed at regional scale, given that areas susceptible to landslides typically represent only a fraction of territorial warning zones.
Ocean Surface Connectivity in the Arctic: Capabilities and Caveats of Community Detection in Lagrangian Flow Networks
Authors: Reijnders Daan , van Leeuwen Erik Jan , van Sebille Erik
Published: March 2021

To identify barriers to transport in a fluid domain, community detection algorithms from network science have been used to divide the domain into clusters that are sparsely connected with each other. In a previous application to the closed domain of the Mediterranean Sea, communities detected by the Infomap algorithm have barriers that often coincide with well-known oceanographic features. We apply this clustering method to the surface of the Arctic and subarctic oceans and thereby show that it can also be applied to open domains. First, we construct a Lagrangian flow network by simulating the exchange of Lagrangian particles between different bins in an icosahedral-hexagonal grid. Then, Infomap is applied to identify groups of well-connected bins. The resolved transport barriers include naturally occurring structures, such as the major currents. As expected, clusters in the Arctic are affected by seasonal and annual variations in sea-ice concentration. An important caveat of community detection algorithms is that many different divisions into clusters may qualify as good solutions. Moreover, while certain cluster boundaries lie consistently at the same location between different good solutions, other boundary locations vary significantly, making it difficult to assess the physical meaning of a single solution. We therefore consider an ensemble of solutions to find persistent boundaries, trends and correlations with surface velocities and sea-ice cover.
Plate tectonics and volatiles: the nanorock connexion
Authors: Nicoli Gautier , Ferrero Silvio
Published: March 2021

The global geological volatile cycle (H, C, N) plays an important role in the long term self-regulation of the Earth system. However, the complex interaction between its deep, solid Earth component (i.e. crust and mantle), Earth’s fluid envelope (i.e. atmosphere and hydrosphere) and plate tectonic processes is a subject of ongoing debate. Here, we want to draw attention to how the presence of primary, pristine melt (MI) and fluid (FI) inclusions in high grade metamorphic minerals could help constrain the crustal component of the volatile cycle. We review the distribution of pristine MI and FI throughout Earth’s history, from the onset of plate tectonics at ca. 3.0 Ga to the present day. Combined with thermodynamic modelling, our compilation indicates that periods of well-established plate tectonics regimes at 0-1.2 Ga and 1.8-2.0 Ga, might be more prone to the reworking of supracrustal lithologies and the storage of volatiles at lower crustal depths. We then argue that the lower crust might constitute an important, although temporary, volatile storage unit, capable to influence the composition of the surface envelopes through the mean of weathering, crustal thickening, partial melting and crustal assimilation during volcanic activity.

Such hypothesis has implication beyond the scope of metamorphic petrology as it potentially links geodynamic mechanisms to habitable surface conditions. MI and FI in metamorphic rocks is a rich but still relatively uncharted realm. In the near future, a concerted research effort should aim to find and characterize new instances of pristine inclusions in periods of the Earth’s history currently underrepresented in the inclusion database, e.g. the Boring Billion. The merging of the messages of thousands of minuscule droplets of fluids trapped in the deepest roots of the continental plates will then eventually provide a truly comprehensive portrait of how the Earth’s evolution proceeds through the geological timescale.

 
The Video Globe Challenge 2020, a video streamgauging race during the Covid-19 lockdown
Authors: Le Coz Jérôme , Hauet Alexandre , Despax Aurélien
Published: March 2021

The strict lockdown imposed by the Covid-19 health crisis motivated the French-speaking hydrometry network Groupe Doppler Hydrométrie (GDH) to organise a new type of hydrometric intercomparison, based on video gauging. Between 15 April and 10 May 2020, the Video Globe Challenge 2020 was run in 8 stages corresponding to 8 videos taken from the ground (5 cases) or from a drone (3 cases), each coming with a reference discharge measurement (6 ADCP gauging, 1 dilution gauging, 1 calibration curve). These eight cases present various flows, measurement conditions and operating difficulties. The data were provided by EDF, DREAL Auvergne-Rhône-Alpes, NVE (Norway) and DNRME Queensland (Mark Randall, Australia).

For each stage, around 25 competitors participated by submitting their discharge result, their surface velocity coefficient (a.k.a alpha) estimate and their parameters, with the hope of getting as close as possible to the reference discharge. Several velocimetry techniques and software tools were used: from visual spotting and manual processing, in Flowsnap (Tenevia), Excel or Barème, to specialised software, mainly Fudaa-LSPIV (EDF/INRAE) but also SSIVSuite (Photrack), PIVlab, and Opyf (EPFL/INRIA, local optical flow). The general classification (smaller sum of percentage deviations to discharge references), points classification (smaller sum of ranks), sniper classification (best visual velocimetry) and young rider classification (for students) awarded the yellow, green, polka dot and white jerseys, respectively.

The Challenge 2020 has been rich in lessons, notably by illustrating several important sources of error for video gauging and the possible parries that the user can deploy (or not...). The exercise was as useful for training and coaching the participants (often beginners) as it was for identifying the improvements to be expected in procedures and software. The results highlight some operator-related error sources which need to be minimized by developing more guided or automated parameter settings, and more robust velocimetry algorithms. They also illustrate the typical uncertainty levels of such measurements.

The cultural aspects were not left out, revealing historical facts and hydrometry-related feats about the rivers visited, e.g. Julius Caesar wading the river to join the druids in the sanctuary of Seranos, Viking Stør Åne the Blue breaking the ice cover to prevent rating shift, or Sir Herbert inventor of the anti-crocodile waders. The official history of hydrometry conceals many unsuspected mysteries that have yet to be revealed...
Analysis of EURO-CORDEX sub-daily rainfall simulations and derived event characteristics
Authors: Nanni Paola , Peres David J. , Musumeci Rosaria E. , Cancelliere Antonino
Published: March 2021

Climate change is a phenomenon that is claimed to be responsible for a significant alteration of the precipitation regime in different regions worldwide and for the induced potential changes on related hydrological hazards. In particular, some consensus has raised about the fact that climate changes can induce a shift to shorter but more intense rainfall events, causing an intensification of urban and flash flooding hazards.  Regional climate models (RCMs) are a useful tool for trying to predict the impacts of climate change on hydrological events, although their application may lead to significant differences when different models are adopted. For this reason, it is of key importance to ascertain the quality of regional climate models (RCMs), especially with reference to their ability to reproduce the main climatological regimes with respect to an historical period. To this end, several studies have focused on the analysis of annual or monthly data, while few studies do exist that analyze the sub-daily data that are made available by the regional climate projection initiatives. In this study, with reference to specific locations in eastern Sicily (Italy), we first evaluate historical simulations of precipitation data from selected RCMs belonging to the Euro-CORDEX (Coordinated Regional Climate Downscaling Experiment for the Euro-Mediterranean area) with high temporal resolution (three-hourly), in order to understand how they compare to fine-resolution observations. In particular, we investigate the ability to reproduce rainfall event characteristics, as well as annual maxima precipitation at different durations. With reference to rainfall event characteristics, we specifically focus on duration, intensity, and inter-arrival time between events. Annual maxima are analyzed at sub-daily durations. We then analyze the future simulations according to different Representative concentration scenarios. The proposed analysis highlights the differences between the different RCMs, supporting the selection of the most suitable climate model for assessing the impacts in the considered locations, and to understand what trends for intense precipitation are to be expected in the future.
Modeling fisheries as multiscalar human-natural systems
Authors: Carlson Andrew K. , Rubenstein Daniel I. , Levin Simon A.
Published: March 2021

Marine fisheries are social-ecological systems important for human health and livelihoods. However, research approaches that consider human–nature interactions within as well as between adjacent and distant fisheries are scarce. As such, we measured and modeled marine fisheries catches at local and regional scales over 65 years (1950–2014), assessed cross-scalar interactions among fishing types (artisanal, subsistence, industrial, recreational), and predicted future catches using the metacoupling framework, a new approach for evaluating human-nature interactions within and across adjacent and distant fisheries (metacouplings). Across taxa examined (mahi-mahi [Coryphaena hippurus], Atlantic bluefin tuna [Thunnus thynnus], cods [Gadidae]), 75% of catches (8.5 million metric tons [MMT]) were made by nations in their own exclusive economic zones (EEZs; Type 1 fishing). However, catches in adjacent EEZs (Type 2 fishing, 1.0 MMT) and distant EEZs and the high seas (Type 3 fishing, 1.9 MMT) increased substantially for all taxa at certain times, becoming consistently important for tuna and cods after 1980. Moreover, Types 1–3 fishing interacted in ways that affect humans differentially across fisheries. For instance, tuna artisanal and subsistence catches (Type 1) decreased with increasing Type 2 and Type 3 industrial fishing, respectively. Cod subsistence catches declined with increasing Type 2/3 industrial fishing and Type 1 artisanal fishing, whereas fishing-type interactions were largely positive for mahi-mahi, causing catches to increase across sectors. Overall, metacouplings affect humans in positive and negative ways that vary across scales and fisheries systems, galvanizing the need for metacoupling-informed fisheries research, policy, and management programs. We’ve since extended this research approach to include Atlantic herring (Clupea harengus), the subject of a journal article in press.
Frozen soils characterization by the use of ERT and EMI methods: cases in the Dolomites (Italy)
Authors: Pavoni Mirko , Boaga Jacopo
Published: March 2021

Nowadays, tourism and sport activities make the Alps high mountain environment widely populated. As example, the Dolomites (UNCESCO site, North-East Italy) host millions of tourists every year. Consequently, many infrastructures (e.g. roads, cable cars and hotels) have been built in these areas, and are subject to instabilities hazards as landslide, avalanches or frozen soils problems.  Mountain permafrost is in fact one of the many aspects to be considered for the natural hazards and risk management in high mountains environment. Due to the atmospheric warming trend, mountain permafrost is thawing and its degradation is influencing the triggering and the evolvement of natural hazards processes such as rockfalls, landslides, debris flows and floods. We have nearly 5000 rock glaciers in the alps, as highlighted in the inventory of the PermaNET project (2011), therefore the study and monitoring of these periglacial forms has both a scientific and economic importance. Geophysical surveys have been historically applied in this kind of environment, in particular the Electrical Resistivity Tomography (ERT) for the characterization of the active layer thickness (ALT). The technique exploits the high electrical resistivity contrast between frozen and non-frozen debris, and, over the last years, has allowed the researchers to achieve very relevant results. However, performing these measurements is expensive both in terms of time and equipment, particularly considering that the rock glaciers are often very difficult to reach. Thus, usually we are not able to perform many investigation lines and, as the results are 2D resistivity sections, it is very difficult to obtain enough information to completely characterize a heterogeneous environment such as a rock glacier. For this reason, we tried to apply the EMI method (in the frequency domain) for the characterization of the ALT. EMI method, in fact,  theoretically allows us to define the distribution of electrical resistivity in the first subsoil in a very quick way, simply by transporting the device over the interested area. Compared to ERT, it is potentially able to characterize much larger areas of a rock glacier, albeit with a lower resolution and penetration. On the other hand, because the high resistivities of the frozen ground, EMI do not guarantee an optimal working and rigorous acquisition protocol must be adopted. We tested ERT and EMI measurements along the same investigation lines, in two different sites of the Dolomites area (the Murfreit and Biz Boè rock glaciers). Finally, we discussed the advantages and disadvantages of both the techniques.
Using ground-penetrating radar to determine the representativeness of ice core surface mass balance records at ice rises along the Princess Ragnhild Coast, East Antarctica
Authors: Cavitte Marie G. P. , Goosse Hugues , Wauthy Sarah , Tison Jean-Louis , Kausch Thore , Sun Sainan , Inoue Mana , Dalaiden Quentin , Lenaerts Jan T.M. , Lhermitte Stef , Pattyn Frank
Published: March 2021

Several studies have shown that there is often a poor match between surface mass balance (SMB, mass gain at the surface of the ice sheet) simulated by regional climate models and the one locally measured from ice cores in Antarctica. Models’ representation of the physical processes that affect SMB is known to be imperfect, while ice core records may be strongly influenced by local processes such as post-depositional wind redistribution and precipitation intermittency. These two sources of uncertainty likely both have a role to play in the discrepancy identified between modeled and observed ice core SMB estimates over the past centuries.

The goal here is to estimate the uncertainties associated with the difference between a point-wise measurement of SMB as provided by the ice core and the SMB averages over a grid of several square kilometers of the models. To do so, we use ground-penetrating radar (GPR) data, collected over several ice rises, located along the high accumulation Princess Ragnhild Coast (East Antarctica), to obtain a multi-year resolution record that goes back ∼30-40 years, representing SMB spatial and temporal variability at the scale of a few km2 for each ice rise. Ice cores were collected during each radar field campaign, which allows us to place age constraints on the radar stratigraphy obtained and compare the GPR SMB estimates with the ice core SMB estimate.

Therefore, we are able to calculate an error of representativeness for each ice core SMB, estimated as the difference between the average GPR SMB over a few km2 and the ice core SMB. This representativeness error can be split into two components: a systematic error (on the order of ∼0.1 m w.e. yr-1) and a random error (on the order of ±1 cm w.e. yr-1). Finally, we then compare our corrected ice core SMB records to regional SMB derived from a state-of-the-art polar-oriented regional climate model to quantify the impact of ice core uncertainties on the modeled-observed SMB discrepancy.
Permafrost vulnerability to contemporary climate changes in Eastern Chukotka coastal plains (NE Russia)
Authors: Maslakov Alexey , Komova Nina , Egorov Evgeny , Mikhaylyukova Polina , Grishchenko Mikhail , Zotova Larisa
Published: March 2021

Recent permafrost degradation is detected in many cold regions of the world. This process is due to surface lowering caused by ice-rich sediments thaw and massive ice beds melt. Eastern Chukotka coastal plains polygon is one of the key sites for studying climate change's impact on permafrost conditions and human activity. This region is the habitat of indigenous people, concentrated in the coastal villages. The study site is approximately 400 km2 in area and characterized by a variety of landscape, geomorphological, and permafrost conditions. Using remote sensing data, field observations, and shallow drilling results, we ranked and delineated the areas on their susceptibility to thermokarst, thermal erosion, and solifluction activation due to the further air temperature increasing and potential human disturbances. Spatial analysis on current thaw settlement rates combined with drilling data allowed us to map the areas with a high concentration of surficial massive ice beds. These studies provide a better understanding of permafrost conditions in Eastern Chukotka and its response to human impact and climate change.
Building Climate Change into Weather and Climate Teaching
Authors: Knight Sylvia
Published: March 2021

The Royal Meteorological Society believes that every student should leave school with the basic climate literacy that would enable them to engage with the messages put forward by the media or politicians, or to make informed decisions about their own opportunities and responsibilities.

Through 2019/ 2020, students, the media and academics became increasingly vocal in demanding that more climate change be taught in UK schools. With a rigid National Curriculum and exam specifications, part of the problem lies in students (and teachers) not realising the relevance of concepts and processes they have actually been taught in school to understanding climate change and the broad spectrum of impacts, mitigation and adaptation issues associated with it. In addition, weather and climate are commonly perceived as being amongst the harder topics in geography and so, even when they are taught at all, geography teachers are used to teaching weather, climate and climate change separately, not highlighting the close ties and links between the topics.

With this in mind, the Royal Meteorological Society has developed a full scheme of work for 11-14 year old students which integrates climate change thinking into weather and climate lessons. Hard copy teacher’s guides have been distributed to schools throughout the UK, free of charge, with associated teaching resources being made available online. Recognising the importance of teacher understanding, the resources are accompanied by CPD materials for teachers.

In 2021, we hope to build on this work by developing resources and teacher training materials for science teachers and students.
A satellite-based Lagrangian view on the origin of water-masses in the northern European shelf seas
Authors: Eisbrenner Ezra , Chafik Léon
Published: March 2021

Knowledge about water-mass properties is critical to understanding how ocean climate variability impacts the shelf seas. Disentangling the origin of shelf sea water-masses and associated driving mechanisms is, therefore, a significant step towards improving the predictive skill related to water-mass evolution. Especially more conservative water-mass properties, even of surface waters, have the potential to reveal links between the shelf seas and large-scale ocean circulation regimes when traced back to their origin. The northern North Sea for example as the main gateway for water-masses to one of Europe's largest shelf sea areas is largely supplied by water-masses from the open North Atlantic, a connection which can be seen from, e.g., sea surface salinity.

The aim of this study is to identify the origin of northern North Sea water-masses and distinguish pathway variability relative to the subpolar gyre regimes. This is done using Lagrangian trajectories, calculated using satellite-derived velocity fields. The results of the Lagrangian statistics mainly indicate that on inter-annual time-scales the North Atlantic subpolar gyre strength largely influences the water-masses found in the North Sea. The relation is found to originate from varying pathways and therefore origin. We conclude that on inter-annual time scales the subpolar gyre strength is a good proxy and skillful predictor of water-mass variability in the North Sea.
Numerical simulation of structural growth in the Lebanese restraining bends, Dead Sea fault system
Authors: Fedorik Jakub , E. Maesano Francesco , M. Alafifi Abdulkader
Published: March 2021

Strike-slip structures are rarely validated because commonly used 2D restoration techniques are not applicable. Here we present the results of 3D numerical simulation of the restraining bends in Lebanon using boundary element methods of fault deformation implemented in MOVE™. The Lebanon restraining bend is the largest transpressional feature along the Dead Sea Transform (DST), and consists of two mountain ranges: Mount Lebanon on the west, dominated by the active Yammouneh fault, and the Anti-Lebanon Range to the east, influenced by the Serghaya and other faults. We built a new 3D geometrical model of the fault surfaces based on previous mapping of faults onshore and offshore Lebanon, complemented by interpretation of satellite images and DEM, and analogy with experimental models of restraining bend or transpressional structures. The model was simulated in response to the regional stress produced by the left-lateral displacement of the Arabian plate. The simulation accurately predicted the shape and magnitude of positive and negative topographic changes and faults slip directions throughout Lebanon. Furthermore, this simulation supports the hypothesis that the formation of the Anti-Lebanon Range was influenced by the intersection of the DST with the older Palmyrides belt, resulting in failed restraining bend. In contrast, the structure of Mt. Lebanon is similar to laboratory experiments of a restraining bend without inheritance. In addition, our simulation presents an approach of how strike-slip structural models may be validated in areas where subsurface data are limited.
Improving the treatment of subgrid cloud variability in warm rain simulation in CESM2
Authors: Wang Hao , Wang Minghuai , Rosenfeld Daniel , Zhu Yannian , Zhang Zhibo
Published: March 2021

Representing subgrid variability of cloud properties has always been a challenge in global climate models (GCMs). In microphysics schemes, the effects of subgrid cloud variability on warm rain process rates calculated based on mean cloud properties are usually accounted for by scaling process rates by an enhancement factor (EF) that is derived from the subgrid variance of cloud water. In our study, we find that the EF derived from Cloud Layers Unified by Binormals (CLUBB) in Community Earth System Model Version 2 (CESM2) is severely overestimated in most of the oceanic areas, which leads to the strong overestimation in the autoconversion rate. Through an EF formula based on empirical fitting of MODIS, we improve the EF in the liquid phase clouds. Results show that the model has a more reasonable relationship between autoconversion rate, cloud liquid water content (LWC), and droplet number concentration (CDNC) in warm rain simulation. The annual mean liquid cloud fraction (LCF), liquid water path (LWP), and CDNC show obvious increases for marine stratocumulus, where the probability of precipitation (POP) shows an obvious decrease. The annual mean LCF, cloud optical thickness (COT), and shortwave cloud forcing (SWCF) match better with observation. The sensitivity of LWP to aerosol decreases obviously. The sensitivities of LCF, LWP, cloud top droplet effective radius (CER), and COT to aerosol are in better agreement with MODIS, but the model still underestimates the response of cloud albedo to aerosol. These results indicate the importance of representing reasonable subgrid cloud variabilities in the simulation of cloud properties and aerosol-cloud interaction in climate models.
Ice cloud retrieval from high spectral resolution measurements in the thermal infrared : Application to IASI and IASI-NG
Authors: Leonarski Lucie , C.-Labonnote Laurent , Compiègne Mathieu , Vidot Jérôme , Baran Anthony J. , Dubuisson Philippe
Published: March 2021

Besides their strong contribution to weather forecast improvement through data assimilation in clear-sky conditions, thermal infrared sounders on board polar orbiting platforms are now playing a key role in monitoring changes in atmospheric composition. However, it is known that clear sky observations are only a small part of the entire set of measurements, the remaining part is only slightly used as they are contaminated by either aerosols and/or clouds. Moreover, ice or liquid cloud retrieval of column and profile properties from passive and active measurements respectively help us in reaching a better understanding of climate processes. If the information provided by the latter has allowed a significant advance in our knowledge of the vertical distribution of condensed water, it suffers from spatial coverage compared to passive measurements. It is therefore fundamental to better characterize cloud properties from passive measurements by using, for example, high spectral resolution instruments such as IASI and the future IASI-NG.

An information content analysis based on Shannon's formalism has been used to determine the level and the spectral repartition of the information about the ice cloud properties in the IASI and IASI-NG spectra. Based on this analysis, we have developped and tested an algorithm which allows to retrieve from an optimal estimation approach the cloud integrated ice water content together with the cloud layer altitude. We have taken into account the Signal-to-Noise ratio of each specific instrument and the uncertainties due to the non-retrieved atmospheric and surface parameters. The forward model is the fast radiative transfer model RTTOV which has been developped for satellite data assimilation in Numerical Weather Prediction (NWP) models. The ice cloud microphysical model is based on the ensemble model of Baran and Labonnote (2007), where the bulk ice optical properties have been parametrized as a function of the ice water content (expressed in g/m³) and in cloud temperature.

The present study aims to quantify the potential and limits of thermal infrared sounders such as IASI or IASI-NG to retrieve ice cloud properties by using a representative dataset from the global operational short range forecast of the european center of medium-range weather forecast.
A Bayesian hierarchical model for assessing the eutrophication status of inland freshwater systems in the contiguous United States from Landsat time series: the promise of a universal transferable model
Authors: Abbas Mohamad , Alameddine Ibrahim
Published: March 2021

Inland water bodies are variable and complex environments, which are indispensable for maintaining biodiversity and providing ecosystem services. The ecological functions of these environments are increasingly threatened by several stressors such as climate change, human activities and other natural stressors. Anthropogenic eutrophication has become one of the most pressing causes of water quality degradation of freshwater ecosystems worldwide. The eutrophication process accelerates the occurrence of algal blooms, with the dominance of potentially toxic cyanobacterial species. As a result, the assessment and monitoring of change in the eutrophic status of these systems is deemed necessary for adopting efficient and adaptive water quality management plans. While conventional monitoring methods provide accurate snapshots of eutrophication metrics at discrete points, they do not provide a synoptic coverage of the status of a water body in space and time. Compared with in situ monitoring, remote sensing provides an effective method to assess the water quality dynamics of water bodies globally at a relatively high spatio-temporal resolution. Yet, the full potential of remote sensing towards assessing eutrophication in inland freshwater systems has so far remained limited by the need to develop site specific models that need extensive local calibration and validation. This constraint is associated with the poor transferability of these models between systems. In this work, we develop a Bayesian hierarchical modelling (BHM) framework that provides a comprehensive models that can be used to predict chlorophyll-a levels, Secchi disk depth (SDD), and total suspended solids across the continental United States (US) based on Landsat 5, 7 and 8 surface reflectance data. The proposed BHM is able to assess, account, and quantify the lake, ecoregion, and trophic status variabilities. The model is developed based on the AquaSat database that contains more than 600,000 observations collected between 1984 and 2019 from lakes and reservoirs across the contiguous US. The model improved the predictions of SDD and Chlorophyll-a the most as compared to the pooled model; yet no such improvements were observed for TSS. Meanwhile, making use of the ecoregion categorization to develop the BHM structure proved to be the most advantageous.
An open-source integrated solution for flow and transport in random heterogeneous porous media
Authors: Pescimoro Eugenio , Icardi Matteo , Municchi Federico , Bianchi Marco
Published: March 2021

Due to the increasing challenges to preserve water quality and supply at global scale, groundwater flow modeling has become a tool of pivotal relevance for remediation, implementation of policies, and design of applications for recharge management. The strain towards faster and more reliable hydrogeological simulations triggered the development of upscaled and multi-scale approaches employing different diffusion and dispersion models that are still the object of much debate in the community. Our ongoing study focuses on the up scaling of solute transport through heterogeneous geological domains by means of an extensive three-dimensional simulation study, based on a new open-source C++ library, built on top of the well-know finite-volume library OpenFOAM®. We integrate the whole workflow, from geostatistical random field generators to flow and transport solvers with integrated post-processing capabilities. The robustness, scalability and flexibility of the library makes it suitable framework for the development, testing, and application of upscaling techniques.  

Being the subsurface inaccessible by nature, the appeal to geostatistical techniques is a well-established approach to construct a realistic domain for flow and transport simulations. However,  additional challenges are posed by the numerical simulation of highly heterogeneous materials. Indeed, the problem is twofold: on one side it is not always possible to characterize the heterogeneity in a deterministic way, while on the other side numerical methods which are effective for elliptic and parabolic equations solved over homogeneous domains might suffer in heterogeneous media. Both challenges were effectively tackled using the open-soruce library OpenFOAM whose implementation and capabilities will be illustrated. Preliminary results on flow and transport simulations performed on truncated pluri-Gaussian permeability fields will be shown and the influence of geostatistical metrics (e.g. correlation lengths, variance, geological entropy) on the flow and transport results (e.g. average velocity and breakthrough curves) analysed.

Extensions to variable-density, mobile-immobile, and multi-rate mass transfer formulations are also presented in the context of the EU project “SECURe”.
Ashfall hazard: modelling volcanic ash roof loading and revisions to European Building Codes 
Authors: Petford Nick , Quainoo Philip , Kaczmarczyk Stefan
Published: March 2021

This paper presents a numerical procedure for testing the effects of both static and dynamic loading of volcanic ash deposition on concrete roofs. The study aims to propose, a revision to the building regulations to make existing and future European buildings more resilient. The investigation uses a multi-physics simulation approach. Mathematical modelling is developed to investigate the volcanic ash effects in the context of the EN1991 code. A numerical modelling tool (EDEM software) for the Discrete Element Method (DEM) and structural analysis tool (ANSYS) for the Finite Element Method (FEM) is used to investigate 1 m x 1 m x 0.0154 m concrete slab plate subjected to pressure load considering the wind and no-wind effects. The modelled wind velocity was held constant at 0. 2 m/s. The density of the volcanic ash is low compared to natural systems but can be changed to reflect a range of relevant (measured) eruptive products. The key parameters and the results are illustrated as follows. With the initial results only, it is clear that our modelling technique has the potential to explore the loading effects of ash over a range of geological and environmental conditions during deposition.

The number of simulated volcanic particle loads is 80000, Volcanic ash particle density of 1000 (kg/m3). The simulated particle variables results for wind effects in the horizontal direction of (0.2 m/s) are as follows: The maximum pressures as 220042(Pa), the maximum deformation as 0.177 (mm) and the maximum was stress as 10.3 (MPa). The no wind effect (controlled condition) simulations particle variable results are as follows: the maximum pressures as 6411.3 (Pa), the maximum deformation as 0.061 (mm) and the maximum stress as 3.44 (MPa). 

As expected, the wind effect resulted in an uneven distribution of the ash on the roof surface, which in turn produced areas of high-pressure load and stress levels. These results will have a possible impact on the designs of buildings on flat roof considerations. We aim to continue with further investigations to determine the stress impact and collapse failure due to loading over a wide range of relevant volcanic ash particle size compositions.
ULYSSES: a system for global multi-model hydrological seasonal predictions
Authors: Samaniego Luis , Thober Stephan , Kelbling Matthias , Schweppe Robert , Rakovec Oldrich , Shrestha Pallav , Martinez-de la Torre Alberto , Blyth Eleanor M. , Smith Katie A. , Rees Gwyn , Fry Matthew , Sutanudjaja Edwin , Wanders Niko , Bierkens Marc FP , van Beek Rens
Published: March 2021

The Copernicus Climate Change Service aims at facilitating the emergence of a downstream market of climate services with the ultimate goal of supporting the development of a climate-smart society. Central to this vision is the free and unrestricted distribution of high-quality climate data through the Climate Data Store [1], with seasonal meteorological predictions among them. Within this unique and challenging framework, ULYSSES [2] will provide the first "seamless'' multi-model hydrological seasonal prediction system, with a global coverage at a spatial resolution of 0.1° The ULYSSES modeling chain is based on the successfully tested EDgE proof of concept [3] using four state-of-the-art hydrological models (Jules, HTESSEL, mHM, and PCR-GLOBWB). A unique feature of this production chain consists of using the same land surface datasets (e.g. DEM, soil properties) with identical spatio-temporal resolutions and forecast inputs for all HMs, and the same river routing scheme (i.e., the multi-scale routing model mRM).

The initial conditions of the production chain will be based on ERA5-Land dataset and the seasonal forecasts will be driven by a 25-member ensemble generated by the ECMWF-SEAS5 model. ULYSSES aims at generating six essential hydrological variables: snow-water equivalent, snowmelt, evapotranspiration, soil moisture, total runoff, and streamflow with a lead-time of up to six months.  The seasonal forecast was verified at 250+ gauges distributred in all continents during the hind-casting period from 1993 to 2019. The operational forecasting period —in testing phase— started in January 2021 and be extended through until July 2021.  The first operational ULYSSES forecast will be made available by the 10th of each month starting in January 2021.

All input data sets (ERA5-Land), seasonal forecasts (SEAS5) and ULYSSES outputs will be made available in the Copernicus Climate Data Store [1] and will be open access. We aim to engage institutions and researchers around the world that are willing to evaluate the forecasts model performance, with the aim of improving the system in the future. In this talk, the modelling chain concept, model setup and verification of initial results will be presented.

[1] https://cds.climate.copernicus.eu

[2] https://www.ufz.de/ulysses

[3] https://doi.org/10.1175/BAMS-D-17-0274.1
Sea-Level Reconstructions and Archaeological Indicators: A Case Study from the Submerged Hellenistic Harbor at Akko, Israel
Authors: Pietraszek Alyssa Victoria , Katz Oded , Sharvit Jacob , Goodman-Tchernov Beverly
Published: March 2021

With the impending threat of continued sea-level rise and coastal inundation, it is important to understand the short- and long-term factors affecting sea-level in a particular region. Such a feat can be accomplished by turning to indicators of past sea-levels. This study aims to highlight the utility of archaeological indicators in sea-level reconstructions, using Akko on Israel’s northern Mediterranean micro-tidal coast as a case study. Here, installations belonging to the maritime metropolis’ Hellenistic Period (3rd to 1st centuries BCE) harbor, which have well-constrained chronological and elevational limitations, were identified at depths averaging 1.1 to 1.2 meters below present sea-level (mbpsl). These features would have been located sub-aerially during the time of their construction and use, indicating a change in relative sea-level in the area since this time. Utilizing a multiple proxy approach incorporating marine sedimentological and geoarchaeological methodologies with previously recorded regional data, three possible explanations for this apparent sea-level change were assessed: structural deterioration, sea-level rise, and vertical tectonic movements. This study revealed that, although signs of structural deterioration are apparent in some parts of the quay, this particular harbor installation is well-established as in situ as it has a continuous upper surface and its southern edge is built directly on the underlying bedrock. Consequently, the harbor’s current submarine position can instead be attributed to sea-level change and/or vertical tectonic displacements. While this amount of sea-level rise (over 1 m) is in agreement with glacio-hydro-eustatic values suggested for other areas of the Mediterranean, it falls below those previously reported locally. In addition, most studies suggest that the tectonic movement along this stretch of coastline is negligible. These new data provide a reliable relative sea-level marker with very little error with regard to maximum sea-level, thereby renewing the overall consideration of the tectonic and sea-level processes that have been active along this stretch of coastline during the last 2,500 years.
Asymmetric dynamics at subduction zones: from plate kinematic constraints to global mantle convection
Authors: Ficini Eleonora , Cuffaro Marco , Doglioni Carlo
Published: March 2021

The lithospheric sinking along subduction zones is part of the mantle convection. Therefore, computing the volume of lithosphere recycled within the mantle by subducting slabs quantifies the equivalent amount of mantle that should be displaced, for the mass conservation criterion. Starting from the analysis of the subduction hinge kinematics, that could either move towards (H-convergent) or away (H-divergent) with respect to the fixed upper plate, we compute the amount of lithosphere currently subducting below 31 subduction zones worldwide. Our results show that ~190 km3/yr and ~88 km3/yr of lithosphere are currently subducting below H-divergent and H-convergent subduction zones, respectively. This volume discrepancy is principally due to the difference in the two end-members subduction rate, that takes into account the hinge kinematics. We also propose supporting numerical models providing asymmetric volumes of subducted lithosphere, using the subduction rate, instead of plate convergence, as boundary condition. Subduction zones show a worldwide asymmetry from geological and geophysical observations, such as slab dip, structural elevation, gravity anomalies, heat flow, metamorphic evolution, subsidence and uplift rates or depth of the décollement planes. This asymmetry is expressed also in the behaviour of the subduction hinge, so that H-divergent subduction zones appears to be coincident with subduction zones having “westward”-directed slabs, whereas H-convergent are compatible with those that have “eastward-to-northeastward”-directed slabs. On the basis of this geographical polarity of subducting slabs, the obtained lithospheric volume estimation gives ~214 km3/yr and ~88 km3/yr of subducting lithosphere for subduction zones with W-directed and E-to-NE-directed slabs, respectively. This imply that W-directed subduction zones contribute more than twice in lithospheric sinking into the mantle with respect to E-to-NE-directed ones. In accordance with the conservation of mass principle, this volumetric asymmetry in the mantle suggests a displacement of ~120 km3/yr of mantle material from the west to the east, providing a constrain for a global asymmetric mantle convection.
Tipping points induced by parameter drift in an excitable low-order model of the wind-driven ocean circulation
Authors: Pierini Stefano , Ghil Michael
Published: March 2021

A quasi-geostrophic, low-order model of the wind-driven ocean circulation is used to illustrate tipping points induced by time-dependent forcing in excitable chaotic systems. When the wind stress amplitude G is constant in time, our model has a bifurcation from low-amplitude oscillations to high-amplitude relaxation oscillations (ROs) at a wind intensity value Gc. In the presence of time-dependent wind stress, the corresponding tipping point time ttp is defined as the time at which ROs arise. Numerical experiments are carried out using ensemble simulations in the presence of different drift rates of monotonically increasing forcing. Additional experiments include small periodic perturbations of such forcing. The results indicate substantial sensitivity of ttp and G(ttp) Rate-induced tipping, coexisting pullback attractors and total independence from initial states are found for subsets of parameter space. Besides, nonlinear resonance occurs in the presence of periodic perturbations for periods comparable to the RO time scale. The small periodic perturbation can be thought of as the seasonal-to-interannual variability in the wind stress, while the monotonically increasing component stands for the effect of amplification in the midlatitude winds due to anthropogenic warming.