bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient inversion with complex geostatistical priors using normalizing flows and variational inference
Authors: Levy Shiran , Laloy Eric , Linde Niklas
Published: March 2022

We propose an approach for solving geophysical inverse problems which significantly reduces computational costs as compared to Markov chain Monte Carlo (MCMC) methods while providing enhanced uncertainty quantification as compared to efficient gradient-based deterministic methods. The proposed approach relies on variational inference (VI), which seeks to approximate the unnormalized posterior distribution parametrically for a given family of distributions by solving an optimization problem. Although prone to bias if the family of distributions is too limited, VI provides a computationally-efficient approach that scales well to high-dimensional problems. To enhance the expressiveness of the parameterized posterior in the context of geophysical inverse problems, we use a combination of VI and inverse autoregressive flows (IAF), a type of normalizing flows that has been shown to be efficient for machine learning tasks. The IAF consists of invertible neural transport maps transforming an initial density of random variables into a target density, in which the mapping of each instance is conditioned on previous ones. In the combined VI-IAF routine, the approximate distribution is parameterized by the IAF, therefore, the potential expressiveness of the unnormalized posterior is determined by the architecture of the network. The parameters of the IAF are learned by minimizing the Kullback-Leibler divergence between the approximated posterior, which is obtained from samples drawn from a standard normal distribution that are pushed forward through the IAF, and the target posterior distribution. We test this approach on problems in which complex geostatistical priors are described by latent variables within a deep generative model (DGM) of the adversarial type. Previous results have concluded that inversion based on gradient-based optimization techniques perform poorly in this setting because of the high nonlinearity of the generator. Preliminary results involving linear physics suggest that the VI-IAF routine can recover the true model and provides high-quality uncertainty quantification at a low computational cost. As a next step, we will consider cases where the forward model is nonlinear and include comparison against standard MCMC sampling. As most of the inverse problem nonlinearity arises from the DGM generator, we do not expect significant differences in the quality of the approximations with respect to the linear physics case.
Catchment-scale patterns of biogeomorphic interaction in an alpine glacier foreland
Authors: Haselberger Stefan , Scheper Simon , Zangerl Ulrich , Ohler Lisa-Maria , Otto Jan-Christoph , Junker Robert R. , Kraushaar Sabine
Published: March 2022

The interaction between abiotic and biotic development in glacier forelands depends on species traits and the frequency and magnitude of geomorphic events as shown on plot-scale studies. However, upscaling of biogeomorphic interactions is still scarce and it remains unclear how these interactions form and shape dynamic patches.

In this study, we combined traditional field based methods of geomorphology and ecology with remote sensing and soil erosion modelling. Geomorphic mapping allows the delineation of process domains for further methods specification. Field based plot sampling along a chronosequences provides insight into distribution of species composition. Catchment wide patterns of functional groups of vegetation (graminoids, forbs, woody) were analyzed with a random forest algorithm using UAV-based multispectral imagery recorded. Small scale geomorphic events are described through simulated annual sediment transport rates derived from the revised universal soil loss equation model (RUSLE).

The dataset will show temporal and spatial distribution of the stabilizing effect of plant functional types. Analyses of potential erosion rates will show the relationship of small scale sediment transport with species distribution. Results of this study will contribute to our understanding of processes that form biogeomorphic landscape patterns in glacier forelands at different scales.
The role of heatwave events on the occurrence and persistence of thermal stratification in the southern North Sea
Authors: Chen Wei , Staneva Joanna , Grayek Sebastian , Schulz-Stellenfleth Johannes , Greinert Jens
Published: March 2022

Extremes in temperatures not only directly affect the marine environment and ecosystems but also have indirect impacts on hydrodynamics and marine life. The role of heatwave events responsible for the occurrence and persistence of thermal stratification was analysed using a fully coupled hydrodynamic and wave model within the framework of the Geesthacht Coupled cOAstal model SysTem (GCOAST) for the North Sea. The model results were assessed against satellite reprocessed data and in situ observations from field campaigns and fixed MARNET stations. To quantify the degree of stratification, a potential energy anomaly over the water column was calculated. A linear correlation existed between the air temperatures and the potential energy anomaly in the North Sea excluding the Norwegian Trench and the area south of 54◦N latitude. Contrary to the northern part of the North Sea, where the water column is stratified in the warming season each year, the southern North Sea is seasonally stratified in years when a heatwave occurs. The influences of heatwaves on the occurrence of summer stratification in the southern North Sea are mainly in the form of two aspects, i.e., a rapid rise in sea surface temperature at the early stage of the heatwave period and a relatively higher water temperature during summer than the multiyear mean. Another factor that enhances the thermal stratification in summer is the memory of the water column to cold spells earlier in the year. Differences between the seasonally stratified northern North Sea and the heatwave-induced stratified southern North Sea were attributed to changes in water depth.
Lab and modelling tests to develop a geoelectric monitoring system for municipal solid waste landfills
Authors: Panzeri Lorenzo , Papini Monica , Formaggia Luca , Scotti Anna , Fumagalli Alessio , Arosio Diego , Longoni Laura
Published: March 2022

Although the indications contained in the European New Green Deal aim to inhibit the opening of new waste disposal sites through a circular economy of waste materials, the management of an extremely large number of municipal solid waste landfills (MSWLF) at different stages of their life cycle is a highly topical issue. Recent national regulations in Italy require the operators to monitor subsoil conditions for 30 years, but do not define clear and unambiguous guidelines.

According to analyses carried out at various landfill sites in northern Italy, monitoring activities were often found to be set up with wells equipped with piezometers. This approach is not optimal because when any contaminants are intercepted by the wells, the conditions of the subsoil may already be compromised. Therefore, the goal of our work is to develop methodologies to test and define an effective monitoring protocol that allows to mitigate the environmental and ecological risks associated with the subsurface propagation of pollutants at MSWLF sites.

The analysis of the subsoil conditions involves the design of monitoring methodologies and the interpretation of the obtained results, exploiting geological, hydrogeological and geophysical knowledge and skills. Accordingly, we rely on a research methodology based on the mutual and continuous exchange between the involved disciplines, starting from the initial geological assumptions that will be used to define a physical model of the subsurface. We mainly resort to indirect non-invasive techniques, in particular to the direct current (DC) electrical resistivity tomography (ERT) that on the one hand is indicated for identifying conductive anomalies associated with the propagation of pollutants, but on the other hand constitutes a complex ill-posed numerical problem. The major issues are related to the spatial resolution and the penetration depth of the technique that in turn control the capability to detect presence and the conditions of the extremely thin high-density polyethylene (HDPE) membrane used to isolate the landfill waste from the surroundings.

To tackle the abovementioned issues, we decided to perform properly downscaled laboratory experiments in order to test the effectiveness of DC methodology in controlled and well-known settings. Processing and interpretation of the collected geoelectrical data are supported by a new modelling code in Python programming language that is being developed.

We deem that the integration of lab and modelling tests is necessary to propose a sound standard approach to address complex and multidisciplinary problems related to landfill risk management.
Evaluating quantitative precipitation estimates and hydrological models for simulating the 2021 extreme events in Germany
Authors: Saadi Mohamed , Furusho-Percot Carina , Belleflamme Alexandre , Chen Ju-Yu , Reinoso-Rondinel Ricardo , Troemel Silke , Kollet Stefan
Published: March 2022

Implementing an effective nationwide, extreme-flood forecasting system requires improving both the estimation of quantitative precipitation and the hydrological modelling tools. We investigated the ability of state-of-the-art radar-based precipitation products and two contrasting hydrological models in providing reliable flood hindcasts and nowcasts for the July 2021 catastrophic floods. Among others, rainfall retrievals based on specific attenuation, a polarimetric radar variable, were used to improve the accuracy of the rain rates, and different radar-based nowcasting methods (deterministic and stochastic) were tested to quantify their added value in improving the forecast lead time. Hydrological models consisted of a lumped, conceptual model (GR4H) and a distributed physically-based model (ParFlow-CLM) that couples 3D surface and sub-surface flows. The parameters of the lumped model were calibrated on historical data, whereas the parameters of the distributed model were estimated based on landscape and soil properties. Preliminary results indicate that differences in simulated peakflows were predominantly due to differences in the rainfall retrievals rather than hydrological models. Warm rain processes near the surface led to underestimated precipitation sums compared to ground-based estimations. The precipitation estimates largely impacted the ability of models in detecting the exceedance of the 100-year flood, which highlights the need for reliable precipitation estimates to forecast such extreme events.
The 3D Polarization of Recoil Leaders
Authors: Hare Brian , Scholten Olaf , Dwyer Joseph , Liu Ningyu , Strepka Chris , Buitink Stijn , ter Veen Sander
Published: March 2022

We have recently developed a new 3D beamforming algorithm, using data from the LOw Frequency ARray (LOFAR) radio telescope (in the 30-80 MHz band), that is capable of resolving even the most complex lightning phenomena with meter and nanosecond scale accuracy. Because it operates in full 3D, this algorithm inherently extracts and accounts for the 3D polarization of the VHF sources. Here we demonstrate the full power of this technique by extracting the full 3D polarization of multiple sections of recoil leaders. We confirm previous work that showed that recoil leaders have significant polarization perpendicular to the lightning channel, likely due to charge flow between the lightning channel core and corona sheath. However, we also show that recoil leaders can also have significant polarization parallel to the channel as well. In addition, we show that the ratio of parallel-to-perpendicular polarization is strongly correlated with faster and more intensely emitting recoil leaders. We will argue that this could be due to faster recoils causing the electric field parallel to the channel to change more rapidly, and if the electric field changes rapidly enough than the recoil leader can create streamers parallel to the lightning channel which are much more strongly emitting than streamers perpendicular to the lightning channel.

 
The site selection procedure for a high-level radioactive waste repository in Germany: an overview of the process and upcoming exploration activities
Authors: Bairlein Katharina , Perner Melissa , Meier Frank , Schamp Jürgen
Published: March 2022

According to the 'Repository Site Selection Act' (a governmental law, called in German the Standortauswahlgesetz – StandAG), the German National Waste Management Organisation (BGE) has been assigned to be the implementer for the German site selection procedure. As such, the BGE is responsible to identify a site for a high-level radioactive waste repository in a deep geological formation with best possible safety conditions for a period of at least one million years.

The German site selection procedure is an iterative process and consists of three phases with an increasing level of detail while the survey area becomes smaller during the process. An immanent part is the repetitive application of exclusion criteria, minimum requirements and the geoscientific weighting criteria (Sections 22 – 24 StandAG) during each phase. Starting with an empty, so-called white map of Germany, the BGE completed Step 1 of Phase I in September 2020 with the submission of the sub-areas interim report. Therein, 90 individual sub-areas were identified, where a favourable geological condition for the safe disposal of radioactive waste is possible. According to the site selection act the host rocks claystone, rock salt and crystalline rock are considered. In the current Step 2 of Phase I, both the representative preliminary safety assessments (Section 27 StandAG) and the repeated application of the above-mentioned criteria and requirements as well as the planning-scientific weighing criteria according to Section 25 StandAG are applied to localise siting regions within the 90 sub-areas.

Surface exploration, including geophysical surveys, geological mapping, hydrogeological investigation and drilling of boreholes, will take place within these siting regions in the scope of Phase II. Currently, exploration targets are defined, which arise from the safety assessments and the mentioned requirements and criteria. Existing data from former exploration activities such as seismic and borehole data, but also other geoscientific data are considered. These data have to be selected, procured and possibly reprocessed with a new focus on a high-level radioactive waste repository. After comparison of the principal demand of information as mentioned above and the already existing data, the exploration demand for every siting region will be derived by a thorough gap analysis. Based on that, the surface exploration programs will be developed.

Phase III is characterized by higher-grade, more detailed subsurface exploration activities, which again provide the base for preliminary safety assessments. Phase III ends with a proposal for a site for a high-level radioactive waste repository.
Detection of Volcanic Deformations in InSAR Velocity Maps - a contribution to TecVolSA project
Authors: Beker Teo , Ansari Homa , Montazeri Sina , Song Qian
Published: March 2022

TecVolSA (Tectonics and Volcanoes in South America) is a project with a goal of developing intelligent Earth Observation (EO) data processing and exploitation for monitoring various geophysical processes in central south American Andes. Large amount of Sentinel-1 data over the period of about 5 years has been processed using mixed Permanent Scatterer and Distributed Scatterer (PS/DS) approaches. The received products are velocity maps with InSAR relative error in the order of 1 mm/yr on a large scale (>100km). The second milestone of the project was automatic extraction of information from the data. In this work, the focus is on detecting volcanic deformations. Since the real data prepared in such manner is limited, to train a deep learning model for detection of volcanic deformations, a synthetic training set is used. Models are trained from scratch and InceptionResNet v2 was selected for further experiments as it was found to give best performance among the tested models. The explainable AI (XAI) techniques were used to understand and analyze the confidence of the model and to understand how to improve it. The models trained on synthetic training set underperformed on real test set. Using GradCAM technique, it was identified that slope induced signal and salt lake deformations were mistakenly identified as volcanic deformations. These patterns are difficult to simulate and were not contained in synthetic training set. Bridging this distribution gap was performed using hybrid synthetic-real fine-tuning set, consisting of the real slope induced signal data and synthetic volcanic data. Additionally, false positive rate of the model is reduced using low-pass spatial filtering of the real test set, and finally by adjustments of the temporal baseline received from a sensitivity analysis. The model successfully detected all 10 deforming volcanoes in the region, ranging from 0.4 - 1.8 cm/yr in deformation.
How will we live in the Anthropocene? A scientific guided tour at the 2021 Venice Architecture Biennale.
Authors: Falcieri Francesco Marcello , Ghezzo Michol , Castellani Caterina , de Manicor Lucia
Published: March 2022

The 17th International Architecture Exhibition organized by La Biennale di Venezia ran from 22 May to 21 November 2021 with the title “How will we live together?”. Its main were the social and political questions on the rapidly changing social norms, the political polarization between left and right, climate change, and the growing gap between labor and capital. In the context of the exposition the ongoing collaboration between La Biennale and CNR-ISMAR lead to the development of a guided tour in the Central Pavillion and in the Danish pavilion targeted toward primary schools (6-11 years old). The guided visit used the art pieces presented as a starting point to discuss different aspects Ocean Literacy, climate change and human impacts on the environment with on site explanations and activities to be held once back in class. The tour was divided into three sections: 1) how the Earth-system works and what is the Anthropocene; 2) What are the direct impacts of human activities on the oceans; 3) Which are the consequences of those impact on mankind. A total of 41 classes from primary schools in the Veneto region participated the visit and were later monitored for satisfaction and retention of the information provided during the visit.

In the La Biennale CNR-ISMAR collaboration this was a first attempt to create a guided tour on Ocean Literacy using as a starting point an already established architecture exposition.
Climate X: Meeting the demand for multi-hazard climate risk information tailored to financial services
Authors: Zeneli Markela , Burke Claire , Ramsamy Laura , Mitchell Hamish , Brennan James , Kluza Kamil
Published: March 2022

As uncertainty around the impacts of climate change become more apparent, businesses and communities are relying on cutting-edge information to help them navigate their next steps. Climate X are a climate risk information provider that aims to help businesses and communities prepare for a rapidly changing environment, with an explainable and transparent method.

Our flagship product, Spectra, presents users with a multitude of potential hazards including flooding (fluvial, pluvial, and coastal), subsidence, landslides, and extreme heat. Each hazard risk is quantified at street level, and we project risks and impacts for low emissions (RCP2.6) and high emissions (RCP8.5) scenarios. This allows users to see the difference between the best-case and worst-case scenarios for assets across the UK.

This poster will cover our methods of finding data, interpolating, modelling, and predicting, as well as a tour of our easy-to-use UI.
How do recreational swimmers affect lake-atmosphere and lake-sediment transport?
Authors: Kirillin Georgiy , Liu Liu , Murakaeva Asiya , Dämpfling Hauke , Grossart Hans-Peter
Published: March 2022

Natural waters in urban and suburban areas experience growing stresses from active water use and recreational activities, such as leisure boating, fishing, and swimming. Among other factors, leisure swimmers are considered to have a minor effect on the large-scale dynamics of water bodies. Certain physical processes are however very sensitive to disturbances of boundary layers - a thin diffusive layer at the lake surface and the upper layer of sediment. During hot summers, a high concentration of swimmers in small lakes and ponds may disrupt the boundary layers, intensifying the vertical heat and mass exchange and producing localized outbursts of methane into the atmosphere and(or) release of the dissolved nutrients from sediment to the water column. We performed a series of experiments in the suburban area of Berlin, Germany to estimate the potential swimmer effects on the vertical heat and mass transport. Monitoring of physical and water quality parameters in small (~2 km2) Lake Mellensee revealed a consistent  increase of turbidity and decrease of transparency in the vicinity of the beach actively visited by weekend swimmers from Berlin and surroundings. The measured concentrations of the dissolved methane and the methane fluxes at the lake surface, while indicating potential increase due to localized swimming activities, were heterogeneous and depended strongly on variations in sediment composition and on wind conditions. To quantify the effects on the lake-atmosphere fluxes, we performed estimations of the surface temperature disturbance by swimmers in a large mesocosm facility using UAV-based multispectral and infrared cameras. A manifold increase of the surface heat flux derived from the root-mean-square temperature fluctuations results from the diffusive layer disruption and implies a proportional increase of the dissolved gas release.
How could uncertainty in future ENSO diversity influence assessments of seasonal precipitation anomalies over the 21st century? 
Authors: Dieppois Bastien , Maher Nicola , Capotondi Antonietta , O'Brien John
Published: March 2022

The El Niño-Southern Oscillation (ENSO) is the leading mode of tropical climate variability, with impacts on ecosystems, agriculture, freshwater supplies, and hydropower production spanning much of the globe. Most impact studies use a canonical representation of ENSO, as characterised by sea-surface temperature anomalies (SSTa) in the central-eastern Pacific. However, ENSO shows large differences from one event to another in terms of its intensity, spatial pattern and temporal evolution. For instance, while the 1997/98 El Niño displayed extreme SSTa in the eastern equatorial Pacific, the largest SSTa during the 2002/03 event were weaker and primarily confined to the central equatorial Pacific. These differences in the longitudinal location and intensity of ENSO events, referred to as “ENSO diversity”, are associated with different regional climate impacts throughout the world. The representation of such differences in ENSO spatial patterns in climate models thus strongly influence the skill of impact prediction systems. Here, we exploit the power of single model initial-condition large ensembles (SMILEs) from 14 fully-coupled climate models from both CMIP5 and CMIP6 (totalling over 500 simulations in historical and SSP-RCP scenarios) to examine the system trajectories, and identify future variations in the location and intensity of El Niño and La Niña events. We then quantify how contrasting pathways for ENSO event location, and their associated intensity, could alter seasonal precipitation anomalies throughout the world over the 21st century.
Providing constraints on Antarctic Subglacial Environments using Observations of Active Subglacial Lakes from Satellite Radar Altimetry
Authors: Malczyk George , Gourmelen Noel , Werder Mauro , Wearing Martin , Goldberg Daniel
Published: March 2022

Subglacial water at the base of the ice sheet has been shown to impact ice flow and its discharge into the ocean – which modifies ocean properties and melt rates of fringing ice shelves. Subglacial water, generated from frictional heating and geothermal heat flux, collects in hydrological sinks which store and release water in episodic events. These events, interpreted as water moving in and out of active lakes, have a signature at the surface of the ice sheet which can be detected and quantified by satellite altimetry. By quantifying the volume of water involved in these active events, it is possible to obtain insight into processes otherwise hidden from view. In particular, observing the gain in volume following a drainage event provides constraints on hydrological recharge rates, subglacial water fluxes, and processes leading to basal melt water production. Such a method was applied to the inventory of Antarctic active subglacial lakes using CryoSat’s radar altimeter observations over the 2010-2020 period. Out of 136 known lakes, 13 lakes show clear signs of recharge during the observation period. From these we can extract recharge rates, which act as a lower bound on subglacial melt production. These rates are compared against rates of recharge derived by routing modelled subglacial melt production across the Antarctic Ice Sheet. We demonstrate that, for connected subglacial lake networks, satellite observations can provide a robust validation dataset for sub-glacial melt models. Our results show that, at a local level, estimates of melt water flux is highly dependent on the routing method chosen. We also highlight subglacial lakes where observed rates of recharge are too high to be explained by our current knowledge of the bed and of processes responsible for subglacial melting rates.
The Güralp smart seismic range of instruments benefit from enhanced networking functionality with the new Güralp Data Centre (GDC) software package for easy mass data acquisition and station metadata observing
Authors: Lindsey James , Barbara Rui , Reis Will , Mohr Sally , Cilia Marcella , Watkiss Neil , Hill Phil
Published: March 2022

Güralp’s smart seismic range of seismic instrumentation (incorporating Certimus, Fortimus, Minimus, Radian and Aquarius) prioritizes technical features like low-latency, communication, and computational processes, as well as practical features like compatibility and modular design for easy adaptation and integration with existing networks. 

The Güralp Data Centre interface offers ‘one click’ tools to configure seismic instruments to stream data to a central (typically cloud based) server. From here the data is saved in miniSEED form in configurable folder structures. This application is particularly important for operators dealing with large volumes of seismic waveform data from regional and national networks. The GDC proves to be particularly effective when coupled with low-latency transmission protocols, where data is streamed from seismic stations to the GDC and then efficiently forwarded to the desired location and in the most appropriate format, reducing the overall latency of the system.   

Additionally, the data can be streamed on to downstream processors such as Earthworm or SeisComP to build more advanced large-scale seismic monitoring and data analysis systems. Industry standard protocols are employed throughout whilst offering a simple interface to set up and monitor the operation of the network, meaning that the GDC can be easily implemented into existing systems and networks with minimal configuration.

Long term latency monitoring, network outages and bandwidth usage are all captured and displayed in a number of applets that make the maintenance of large networks straight forward. The Güralp Data Centre includes the Discovery software dashboard which allows network managers to monitor key SOH parameters in Realtime and to also configure system on mass.

Trigger events from instruments can be recorded and displayed on a map as part of a range of features dedicated to EEW implementations. This information is conveyed using the open Common Alert Protocol (CAP). The CAP messages are created as a result of individual station or sub-network triggers and will contain important parameters such the on-site recorded PGA, PGV and PGD. This method provides the lowest possible latency for simple network early warning.

 
Effect of discharge ratio on flow and passive scalar transport in a T-shaped confluence with a wider downstream channel
Authors: Jin Tian , Xavier Ramos Pedro , De Mulder Tom
Published: March 2022

Open-channel confluences are important junctions in fluvial and artificial networks, which regulate the mixing phenomena of substances transported by the merging flows. This paper aims at contributing to the study of how the discharge ratio of the incoming flows influences the flow patterns and mixing phenomena at a T-shaped open-channel confluence with a wider downstream channel. In this study, Large Eddy Simulations (LES) are applied to compare the flow and passive scalar transport processes at two discharge ratios. The results clearly show that in the tributary-dominant case, the shear layer and the mixing interface move to the outer bank, due to the larger lateral velocities in the Confluence Hydrodynamics Zone (CHZ). Moreover, the turbulence and the secondary flow are enhanced, leading to a higher degree of mixing, as compared to the case with a dominance of the incoming flow from the main channel.
Complex basal motion of a Greenland Ice Sheet tidewater glacier
Authors: Law Robert , Christoffersen Poul , MacKie Emma , Cook Samuel , Haseloff Marianne , Gagliardini Olivier
Published: March 2022

Uncertainty tied to the mechanics of the fast motion of the Greenland Ice Sheet plagues sea-level rise predictions. Much of this uncertainty arises from imperfect representations of physical processes in constitutive relationships for basal slip and internal ice deformation, with continued misalignment between model output and borehole field data. To investigate further, we model two isolated cuboid domains from the fast-moving Sermeq Kujalleq (a.k.a Store Glacier), incorporating temperate ice rheology (softer ice at the melting point) and statistically realistic variogram-generated bed topography. Our results indicate a hitherto unappreciated complexity in ice-sheet basal motion over rough beds. Realistic topographic variability leads to highly variable basal slip rates (from <10 to >70% of surface velocity over ~1km), complex and variable deformation patterns, and a basal temperate ice layer that varies greatly in thickness in agreement with borehole observations (from <10 to >150 m). Velocity variations at the relatively smooth upper boundary of the temperate ice layer are significantly less variable, indicating that the slim basal temperate ice layer is an important control on ice motion. These results suggest that inversion procedures for basal traction over rough beds (including parts of Antarctica) may also be accounting for deformation within a temperate ice layer, which is problematic if the inclusion of a temperate ice layer and rough topography means commonly used basal slip relationships are no longer applicable. 
Mercury distribution and reactivity in the Siberian Shelf: preliminary data from the Arctic Expedition ISSS-2020
Authors: Azaroff Alyssa , Gustafsson Örjan , Semiletov Igor , Jonsson Sofi
Published: March 2022

Despite the remote location of the Arctic Ocean (AO), mercury (Hg) level in some Arctic species has increased due to the global anthropogenic Hg emissions. Methylmercury (MeHg), the form of Hg known to bioaccumulate in biota to levels of concern, is a neurotoxin that is mainly produced by microbial methylation of inorganic mercury (iHg) in sediments and natural waters. While huge efforts are made to better understand the Hg cycling of the AO, observational data is still missing for many areas. This is especially true for the largest continental shelf on earth, the Siberian continental shelf.

Here we present the first data on mercury speciation from the international Russian-Swedish Arctic expedition “International Siberian Shelf Study 2020” (ISSS-2020). During the expedition, onboard the research vessel Akademik Mstislav Keldysh, water and sediment were collected from the Barents Sea, Kara Sea, Laptev Sea, and the East Siberian Sea. In addition to samples collected for Hg speciation analysis, experimental incubations of water and sediment using isotopically enriched stable mercury were performed to estimate potential mercury transformations rates. Microbial samples were also collected to determine the microbial diversity associated with mercury transformation.
Sedimentary and environmental evolution of an alpine lake in Sierra Nevada, western Mediterranean region, since the last deglaciation
Authors: López-Avilés Alejandro , Jiménez-Moreno Gonzalo , García-Alix Antonio , García-García Fernando , Camuera Jon , Anderson R. Scott , Sanjurjo-Sánchez Jorge , Arce Chamorro Carlos , Carrión José S.
Published: March 2022

The alpine wetlands from Sierra Nevada mountain range, located in the western Mediterranean region, are highly sensitive to climate and environmental changes and their sedimentary records preserve a high-quality signal of past natural environmental conditions. Previous studies from the Sierra Nevada show that alpine wetland formation occurred principally during the YD-Early Holocene transition in former glacier cirque areas and thus older sedimentary records are lacking from that area. In this study, we present the Laguna Seca (LS) record, which is the longest and oldest sedimentary record (14.1 meters and 18 cal kyr BP, respectively) ever retrieved in the alpine Sierra Nevada. In this record we have carried out detailed chronological and sedimentological analyses and we have obtained magnetic susceptibility, total organic carbon, and carbon/nitrogen data with the main goal of understanding how alpine environments of this region responded to climate variations since the last glacial-interglacial transition. Four climatically-controlled facies associations have been identified and interpreted in terms of transport mechanisms and paleoenvironments: (1) subaerial cohesionless debris flows during a paraglacial stage, (2) till or nival diamicton during a small glacier/nivation hollow stage, (3) massive mudstone by suspension settling of clays into standing water during a lacustrine stage from ~15.7 cal kyr BP to the present and; (4) frost-shattering breccia deposited inside the lacustrine stage, only in an area of the wetland, probably during the YD and related with a periglacial substage. The increase in summer insolation, temperatures and precipitation in the western Mediterranean area probably boosted a significant ice-melting and the glacier retreat in the Sierra Nevada, triggering the development of a deep lake in LS ~15.7 cal kyr BP with an important organic matter contribution until the end of the Early Holocene (except in the Younger Dryas that probably the lake level dropped). The general long-term aridification trend observed in the western Mediterranean region from the Middle Holocene to the present triggered the evolution from deep to ephemeral lacustrine conditions with an increase in aquatic productivity in the LS basin that ended up with the current summer desiccation of the lake.
Water cycle and water resources of the Pyrenees under climate change: the PIRAGUA datasets.
Authors: Palazón Leticia , Beguería Santiago ,   PIRAGUA Team
Published: March 2022

The Pyrenees range is a transboundary mountain region shared by Spain, France and Andorra. As many other mountain regions, the Pyrenees host the upper catchments and recharge zones of the region's main river basins and aquifers. Therefore, it is the main source of water resources that are used in a much larger area that includes important urban concentrations and highly productive rural areas. This territory and its water resources are particularly vulnerable to the consequences of climate change. The PIRAGUA project (2018-2021, https://www.opcc-ctp.org/piragua), funded by FEDER through the POCTEFA Program of the EU, addressed the characterization of the hydrological cycle of the Pyrenees in a climate change context, in order to improve the territories’ adaptation capacity. The goals of the project were to unify and homogenize the existing information, prospect future scenarios, develop indicators of change, and propose adaptation strategies with impact on the territory. The project results were compiled in a series of regional datasets, and are available through the geo-portal of the Pyrenees Climate Change Observatory (https://opcc-ctp.org/geoportal). These include the following resources: PIRAGUA_resources stores information related to water resources use, exploitation and management; PIRAGUA_indicators contains daily streamflow and aquifer level indicators from observed series during the historical period (1950-2019); PIRAGUA_flood includes the number and classification of flood events, at the municipal level; PIRAGUA_atmos_analysis contains observation-based meteorological data suited for hydrological simulation, for the historical period (1981-2010); PIRAGUA_atmos_climate is a  statistical downscaling of six global climatic models, for the historical and future periods (1981-2100); finally, two datasets include the hydrological water cycle components derived from simulations with different hydrological models (SWAT, SASER, GIS-BALAN and RECHARGE) and climate forcings: PIRAGUA_hydro_analysis (1981-2010) and PIRAGUA_hydro_climate (1981-2100). This contribution is devoted to describing these datasets and the tools to explore them and acquire the data, and to provide examples of the main results regarding the climate change effects on the Pyrenees’ water resources.
Natural processes behind the CO2 sink variability in the Southern Ocean during the last three decades
Authors: Yilmaz Elif , Bernardello Raffaele , Martin Adrian P.
Published: March 2022

Anthropogenic activities during the past two centuries have caused an increase in atmospheric CO2 which has driven a linear increase in oceanic CO2 uptake. The Southern Ocean (SO, < 35ᵒS) is one of the major uptake areas for anthropogenic CO2, responsible for ~40% of ocean CO2 sink. Apart from the linear increase in the CO2 sinking trend, in the SO pronounced variations have been observed in recent decades, driven by natural processes, but the exact mechanisms behind them are still debated. Aiming to fill this knowledge gap, we investigated the natural drivers of CO2 flux variations in the SO using existing observation-based datasets between the years 1982-2019. We removed the long-term linear trend in the time series of CO2 flux and other indexes to focus on decadal variations. We found that two mechanisms explain the interannual to decadal variations in the SO: Ekman upwelling and eddy kinetic energy, by their controls on different components of surface pCO2 variations. The pattern of variability in Ekman upwelling during the time period studied was markedly circumpolar, and the time series of its 1st principal component was strongly correlated with the detrended SAM Index (r=0.81, p<0.05). Similarly, leading EOF maps of CO2 flux anomalies and the components of surface pCO2 changes (i.e., nonthermal and thermal) show that their variations were dominantly symmetric. As previously shown, weakening of SO CO2 sink in the 1990s coincides with intense positive SAM episodes. Following the late 1990s, the intensity of SAM decreased, which strengthened the CO2 sink in the early 2000s. At the same time, the relative contribution of the thermal component grew south of the Polar Front, indicating positive temperature anomalies during this period. Such warming events, following intense and recursive SAM episodes were reported before and were attributed to the increased mesoscale eddy activity in the region. In agreement with these studies, our results show that eddy kinetic energy increased after intense SAM periods with a lagged response of ~2 years, and a positive temperature anomaly in low frequency was observed following these peaks. This warming prevented the CO2 uptake rate from reaching immediately to its potential strength in the absence of strong westerlies, and explains the growing effect of the thermal pCO2 component.
Testing the validity of pluvial flood risk models
Authors: Steinhausen Max , Drews Martin , Larsen Morten A. D. , Huszti Levente , Schröter Kai
Published: March 2022

Pluvial floods present an increasing risk in urban environments all over the world. High-resolution, state-of-the-art pluvial flood risk assessments are urgently needed to inform disaster risk reduction measures and climate change adaptation. Still, pluvial flood risk models are generally not empirically tested because of the rarity of local high-intensity precipitation events and/or lack of monitoring and reporting capabilities.

With a combination of Volunteered Geographic Information (VGI) and insurance claims data, we test the validity of hazard, exposure, and multiple vulnerability components of a pluvial flood risk model. As background for our research, we use the city of Budapest, which suffered three heavy rainfall events associated with significant flood damages in just five years (2015, 2017 and 2020). For each pluvial flood event, we collected photographic evidence of flooding from different online media sources, as well as claims data from the Association of Hungarian Insurance Companies (MABISZ) for residential buildings.

Based on the context information shown in the photos, we identified their location in the city through comparison with Google Street View imagery and estimated the associated water depths. These were compared with the results of a generic-type pluvial flood model. The estimation of flood losses revealed spatial patterns of pluvial flood risk in Budapest. We tested the loss estimates against reported loss in the 23 districts of Budapest to better understand the reliability and accuracy of pluvial loss models.

In general, our findings highlight the untapped potential, but also reveal important challenges in using VGI for model evaluation. It is proposed that VGI are used more systematically to improve the confidence in model-based risk assessments for climate change adaptation and disaster risk reduction.

 
Evaluation of the efficiency and impact of a shallow geothermal installation. Case of Can Batlló, Barcelona.
Authors: Coscia Franco Tomás , Criollo Rotman , Scheiber Laura , Bulboa Ignacio , Pujades Estanislao , Vázquez-Suñé Enric
Published: March 2022

The “Can Batlló” factory was built on the Can Mangala between 1877 and 1879, as a cotton yarn and fabric, as well as bleaching, printing and sizeing factory. It is intended to install a geothermal system for the air conditioning of an administrative building in the city of Barcelona in one of the factory´s buildings.

The purpose of this study is to confirm whether the proposed energetic demand can be achieved in a sustainable manner and to assess potential impacts in the subsurface over time.

The numerical model of flow and heat has been pre-calibrated with the regional flow model and thermal response test (TRT) of the area. The results indicate that the extracted geothermal energy could be higher (12-20% more) than the initial design. This higher performance would imply an optimisation of the system. It could be implemented by means of modifying the design of the heat exchangers, by reducing their amount and their length, or by changing the location of the exchangers to the whole location of Can Batlló, and not reducing their installation to a single building. Therefore, in addition to being able to design a more efficient and economic geothermal system, the investment could be recovered sooner[Rotman Cr1] .

Simulations at 10 years of geothermal exploitation indicate that a downstream plume may occur. This variation of the natural subsurface temperature can affect the environment.

Although the analyses carried out have made it possible to know the behavior of the subsurface in the front of this geothermal installation, to make a deeper study would be advisable to determine in more detail the long-term effects (more than 10 years) that it can cause in the subsurface. For this reason, the following tasks are recommended: (1) To create a control network at the scale of the study area to monitor the performance and the effects of the geothermal field once its installation is on operation; (2) To define the optimal characteristics of the exchangers to obtain a better geothermal performance; (3) To perform a drilling of a minimum depth of 200 meters to verify the materials described in the data collection; (4) To perform hydrochemical and isotopic analysis of the executed point to analyze the feasibility of possible groundwater uses; and (5) To carry out the conceptual and numerical modelling of the local and regional hydrogeological and geothermal system with the detail obtained with the previous point and to analyze the optimisation scenarios mentioned above.
Statistical comparison of different strategies to reduce computational time within high resolution hydromorphodynamic modelling
Authors: Sánchez-Artús Xavier , Gracia Vicente , Espino Manuel , Sánchez-Arcilla Agustín
Published: March 2022

Hydromorphodynamic modelling has as one of its pillars the speed of obtaining results. Sometimes it is only due to the necessity to finish some work or to make other simulations but for example when talking about operational systems, this problematic takes even more strength. If other coastal operational modelling have to be coupled after, the model itself has to be fed by other models or the results have to be published periodically, the importance of the simulation speed is clear. A problem appears because there is an insoluble paradigm which doesn’t allow to make simulations combining the best approaches for this three variables: low ”computational time”, high ”resolution” and huge ”study area”. For example, if we want to simulate a huge coastal area but we need to present the results as soon as possible (i.e. low computational time), we will not be able to use a high-resolution grid because it will fail in the second statement. This problem appears in all the other possible scenarios involving this three variables where the best response for all of them cannot be satisfied at the same time due to the paradigm. Then, since it is impossible to totally solve this problematic, a lot of efforts have been made to reduce its effects and to work with the best possible approaches. In this work, two methodologies that try to improve the performance of the hydromorphodynamic simulations with XBeach model are tested and statically compared with the typical performance. On one hand, a direct reduction of the computational time using parallel computing, specifically Message Passing Interface (MPI) with Cluster application. On the other hand, the conversion of the grids that are used for the simulation from rectangular to curvilinear in order to increase only the resolution of the area of interest in the grid, maintaining lower resolutions for the rest of the area.

This research received funding from INTERREG EFA 344/19 MARLIT  Project  European Union / European Regional Development Fund thanks (FEDER) and was done with the support from the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund. We also want to thank the Research, Development and Innovation Program through the grant to ECOPLANTS project (REF: PID2020-119058RB-I00).