bluuebunny/crossref_metadata_2025 huggingface dataset:
Greenland ice-stream dynamics: short-lived and agile?
Authors: Eisen Olaf , Franke Steven , Bons Paul D. , Westhoff Julien , Weikusat Ilka , Binder Tobias , Streng Kyra , Steinhage Daniel , Helm Veit , Paden John D. , Eagles Graeme , Jansen Daniela
Published: February 2023

Reliable knowledge of ice discharge dynamics for the Greenland ice sheet via its ice streams is essential if we are to understand its stability under future climate scenarios as well as their dynamics in the past, especially when using numerical models for diagnosis and prediction. Currently active ice streams in Greenland have been well mapped using remote-sensing data while past ice-stream paths in what are now deglaciated regions can be reconstructed from the landforms they left behind. However, little is known about possible former and now defunct ice streams in areas still covered by ice. Here we use radio-echo sounding data to decipher the regional ice-flow history of the northeastern Greenland ice sheet on the basis of its internal stratigraphy. By creating a three-dimensional reconstruction of time-equivalent horizons, we map folds deep below the surface that we then attribute to the deformation caused by now-extinct ice streams. We propose that locally this ancient ice-!ow regime was much more focused and reached much farther inland than today’s and was deactivated when the main drainage system was reconfigured and relocated southwards. The insight that major ice streams in Greenland might start, shift or abruptly disappear will affect our approaches to understanding and modelling the past or future response of Earth’s ice sheets to global warming. Such behaviour has to be sufficiently reproduced by numerical models operating on the mid- to longer-term timescales to be considered adequate physical representations of the naturally occuring dynamic behaviour of ice streams.
Preliminary 3D isotropic full-waveform inversion model of the Alpine lithosphere from assimilation of AlpArray teleseismic body waves
Authors: Beller Stephen , Mohammadi Najmieh , Monteiller Vadim , Operto Stéphane
Published: February 2023

The Alps, which result from the convergence between the African and Eurasian plates, are an ideal natural laboratory to study the dynamics and evolution of continental orogens. This mountain range is indeed well documented both by geology and geophysics, which have notably allowed to highlight the different stages of continental subduction and collision during its formation. Nevertheless, large uncertainties remain about the 3D shape of structures and the internal composition of the Alps at crustal and upper mantle scales. This context motivated the European initiative AlpArray which deployed a dense array of more than 600 seismic sensors in the Alps and its periphery paving the way for the application of advanced seismic imaging techniques such as teleseismic waveform inversion (FWI). FWI is becoming a state-of-the-art method for lithospheric imaging as it allows the determination of various subsurface properties (seismic wavespeed, density, anisotropy or even attenuation) with high resolution and accuracy. In this study, we present the preliminary results of the LisAlps project which aimed at applying teleseismic FWI to the AlpArray  dataset to build isotropic and anisotropic high-resolution seismic models of the Alps from the surface down to the transition zone. Our preliminary application successfully built an isotropic (P and S seismic wave-speeds and density) model of the entire Alpine lithosphere from the assimilation of the first 60 s of the direct P waveforms of 18 teleseismic events within a period band ranging from 30 to 10 seconds. The resulting models recover large crustal structures of the Alpine range. In the crust, it recovers the surroundings sedimentary basins, crustal thickening in the internal part of the Alps as well as crustal thinning in the Ligurian sea and in the Ivrea zone. In the upper-mantle, where only the P wave-speed model is currently resolved, our model recovers large-scale mantle structures of the European and Apennines slabs.
An InSAR-based Soil Moisture Product for Arid Regions
Authors: De Zan Francesco
Published: February 2023

High-resolutions soil moisture products from remote sensing are very valuable but are not free from limitations. Products based on back-scatter change can give conflicting results over dry areas, when the penetration in dry soils becomes significant.[1]The interferometric phase of Synthetic Aperture Radar acquisitions (in short, the InSAR phase) contains information about the soil moisture variations of the observed target.This work shows the characteristics of a novel In-SAR-based soil moisture product derived from Sentinel-1 radar observations. The algorithm is based on phase closure inversion, an observable which is immune from atmosphere and deformation contributions to the phase.[2]The proposed soil moisture product has a resolution of about 200 m and a good coverage in arid and semi-arid regions. It has the potential of filling the gaps of existing high-resolution products based on backscatter change.An example of the InSAR-based soil moisture product is given in the following figure, which shows a moisture pattern over a rare rain event in the Namibian gravel plain in 2021. Notice the fine structure of channels present in the product. The colorscale units are m3/m3. ValidationThe figure below presents a comparison with the ERA5 weather model and a radiometer-based product (C3S passive), which, despite the low resolution, seem to be reliable also over dry areas. The InSAR soil moisture time series corresponds to one year of Sentinel-1 acquisitions over eastern Spain from the ascending orbit direction. The standard deviation of the difference between the InSAR soil moisture and ERA5 surface soil moisture is just under 3% (m3/m3). Notably, the errors are concentrated on a few dates. As expected, products derived from scatterometry (C3S active) are rather unreliable over this site.Comparisons with weather radar precipitation data validate the high resolution patterns seen in the InSAR product. The match between the two is typically very good.So far, all the results indicate that the InSAR-based soil moisture can be a reliable product on arid regions and can complement back-scatter change methods in areas with significant penetration. It is expected that InSAR-based soil moisture product will be able to cover larger portions of the land areas with sensors operating at longer wavelengths.---References[1] F. De Zan and G. Gomba, “Vegetation and soil moisture inversion from SAR closure phases: First experiments and results,” Remote Sensing of Environment, vol. 217, pp. 562–572, 2018[2 ] W. Wagner, R. Lindorfer, T. Melzer, S. Hahn, B. Bauer-Marschallinger, K. Morrison, J.-C. Calvet, S. Hobbs, R. Quast, I. Greimeister-Pfeil, and M. Vreugdenhil, “Widespread occurrence of anomalous C-band backscatter signals in arid environments caused by subsurface scattering,” Remote Sensing of Environment, vol. 276, 2022
Prolate microswimmer in surface gravity waves
Authors: Ventrella Francesco Michele , De Lillo Filippo , Boffetta Guido , Cencini Massimo , Thiffeault Jean-Luc , Pujara Nimish
Published: February 2023

Planktonic microorganisms immersed in a fluid interact with the ambient flow, altering their trajectories. In surface gravity waves, a common goal for microswimmers is vertical migration. By modeling phytoplankton as spheroidal bodies with a certain swimming velocity, we investigate how the combination of swimmer's dynamical characteristics and fluid velocity gradients affect the motion. We investigate the case of prolate, negative buoyant swimmers. We consider also the case of gyrotactic swimmers. We find that it is possible for microswimmers to be trapped at a finite depth below the sea level. This phenomenon is due to the coupling between swimming, gyrotaxis and flow-induced reorientations. The trajectories obtained by numerical simulations, indicate that the dynamics consist of fast oscillations at the surface wavelength superposed with a slower trend at a longer timescale. This suggests using a multiple time-scale expansion to remove the fast oscillations. The presence of stable fixed points for the slow dynamics allows the trapping behaviour.
Arc and forearc rifting in the Tyrrhenian subduction system
Authors: Corradino Marta , Balazs Attila , Faccenna Claudio , Pepe Fabrizio
Published: February 2023

The evolution of backarc and forearc basins is usually treated separately, as the volcanic arc represents a clear barrier between them. We analyse their spatial and temporal relationships in the Tyrrhenian subduction system, using seismic profiles and numerical modelling. Our results highlight that the Marsili volcano, commonly interpreted as the spreading centre of the Marsili backarc basin, was instead a part of an old (Pliocene) volcanic arc associated with the development of the Vavilov backarc basin (4.3-4.1 to 2.6 Ma). The old volcanic arc was successively affected by arc rifting. This process caused the shift of the Marsili volcano eastwards and the formation of an oceanic backarc basin (~ 1.8 Ma) located between the Marsili volcano and the old remnant arc, which remained fixed. The eastern side of the Marsili basin, previously considered as the other half of the oceanic backarc basin, is instead a part of the forearc domain floored by serpentinised mantle. As slab rollback continued, volcanism migrated towards the trench and a new volcanic arc (Aeolian Island) formed at ~1 Ma in the forearc domain. The formation of the new volcanic arc represents the onset of the forearc-rifting that could lead to the opening of a new backarc basin between the old and young volcanic arc, resulting in the decrease of the initial forearc region extension.The example of the Tyrrhenian Sea illustrates how the evolution of forearc and backarc domains is intimately interconnected. Fluids, released from the downgoing plates, control lithospheric hydration and mantle serpentinisation as well as asthenospheric mantle melting. Fluids and melts induce weakening of the volcanic arc region and drive the arc-rifting that led to the backarc basin formation. Later, the slab rollback causes the trench-ward migration of volcanism that led to the forearc- rifting under the control of fluids released from the downgoing plate.
Evaluating the impact of urban wetlands as nature-based solutions at the catchment scale
Authors: Peng Fangjun , Liu Leyang , Gao Yuxuan , Krivtsov Vladimir , Dobson Barnaby , Mijic Ana
Published: February 2023

During COP14 in 2022, Ramsar Convention commended 25 cities around the world for their efforts to protect urban wetlands. With the development of cities and the increase in land demand, the trend is to reduce the number of open blue spaces. Yet when preserved and sustainably used, urban nature-based solutions in the form of constructed wetlands could provide water management benefits including water quality regulation and flood mitigation. However, these water management benefits have rarely been evaluated at a catchment scale, and the mechanisms behind them are not fully understood, both of which hinder effective integrated constructed wetlands planning. We aim to explore the impact of wetland changes on water quality and quantity at the catchment scale. This study firstly evaluates the benefits by analysing the monitoring water quantity and quality datasets before and after the wetland construction in Enfield catchment, London. To understand the mechanisms behind the benefits, we build a Water Systems Integration Modelling framework (WSIMOD) to simulate the catchment-scale water cycle. This model is validated against monitoring river flow and water quality data. The constructed wetlands are then conceptualised and integrated into the WSIMOD, and their interactions with the catchment water cycle are simulated. Scenarios are constructed to analyse the impacts of different configurations and sizes of the constructed wetlands on the catchment water cycle. The results show that urban wetlands play a role in flood detention and water quality purification of watershed water resources at the catchment scale. Scattered small wetlands can more effectively reduce the impact of a flood under the same total wetland area. The results provide useful insights into the planning of constructed wetlands for maximising the water management benefits at a catchment scale. Future studies could focus on representing the interaction between the quantity and quality of water in a wetland with biodiversity and leveraging this representation to design interventions to improve biodiversity.
On the influence of the Bay of Bengal’s sea surface temperature gradients on rainfall of the South Asian monsoon
Authors: Sheehan Peter , Matthews Adrian , Webber Benjamin , Sanchez-Franks Alejandra , Klingaman Nicholas , Vinayachandran Pn
Published: February 2023

The southwest monsoon delivers over 70% of India’s annual rainfall and is crucial to the success of agriculture across much of South Asia. Monsoon precipitation is known to be sensitive to sea surface temperature (SST) in the Bay of Bengal (BoB). Here, we use a configuration of the Unified Model of the UK Met Office coupled to an ocean mixed layer model to investigate the role of upper-ocean features in the BoB on southwest monsoon precipitation. We focus on the pronounced zonal and meridional SST gradients characteristic of the BoB; the zonal gradient in particular has an as-yet unknown effect on monsoon rainfall. We find that the zonal SST gradient is responsible for a local decrease in rainfall over the southern BoB of approximately 5 mm day−1, and an increase in rainfall over Bangladesh and northern India of approximately 1 mm day−1. This increase is remotely forced by a strengthening of the monsoon Hadley circulation. The meridional SST gradient acts to decrease precipitation over the BoB itself, similarly to the zonal SST gradient, but does not have comparable effects over land. The impacts of barrier layers and high-salinity sub-surface water are also investigated, but neither has significant effects on monsoon precipitation in this model; the influence of barrier layers on precipitation is felt in the months after the southwest monsoon. Models should accurately represent oceanic processes that directly influence BoB SST, such as the BoB cold pool, in order to faithfully represent monsoon rainfall.
Physics of plasma–surface–exosphere–dust coupling at the lunar surface for future exploration programmes
Authors: Futaana Yoshifumi ,   ESA Topical Team : Physics Of Plasma-Surface-Exosphere-Dust Coupling At The Lunar Surface For Future Exploration Programmes
Published: February 2023

Exploration of the Moon provides opportunities to investigate the deep space environment upstream of the geospace and the terrestrial magnetosphere and associated space weather phenomena. Moreover, the Moon interaction with the solar wind adds novel, interdisciplinary aspects to fundamental space research: a complex coupling between the solar wind/magnetospheric plasma – energetic particles – exosphere – dust – solid-surface – mini-magnetosphere. As the Moon is the next step in space exploration, characterizing the environment provides vital support to this endeavor. We note that investigations in this area of science are invaluable in providing a characterization of the environment for the needs of human exploration. On the other hand,  the lunar environment is fragile against human activities. For example, the total mass of the lunar atmosphere is of the order of 10 tons. Therefore, the environment will change drastically once human activity starts on the lunar surface. It is significantly essential to characterize the environment before the fragile lunar atmosphere is “contaminated” by human activities at the surface.With these aspects as a background, we formed an ESA topical team to formulate scientific questions in space plasma physics that can be uniquely investigated on or near the lunar surface. We also derived the required measurements, which can be addressed by lunar missions in the short and long term, including the EL3 (European Logistic Lunar Lander) mission. This presentation introduces the background scientific context and describes the derived scientific concepts. 
Relaxing requirements for spatio-temporal data fusion
Authors: Goyena Harkaitz , Pérez-Goya Unai , Montesino-San Martín Manuel , F. Militino Ana , Atkinson Peter M. , Ugarte M. Dolores
Published: February 2023

Satellite sensors need to make a trade-off between revisit frequency and spatial resolution. This work presents a spatio-temporal image fusion method called Unpaired Spatio-Temporal Fusion of Image Patches (USTFIP). This method combines data from different multispectral sensors and creates images combining the best of each satellite in terms of frequency and resolution. It generates synthetic images and selects optimal information from cloud-contaminated images, to avoid the need of cloud-free matching pairs of satellite images. The removal of this restriction makes it easier to run our fusion algorithm even in the presence of clouds, which are frequent in time series of satellite images. The increasing demand of larger datasets makes necessary the use of computationally optimized methods. Therefore, this method is programmed to run in parallel reducing the run-time with regard to other methods. USTFIP is tested through an experimental scenario with similar procedures as Fit-FC, STARFM and FSDAF. Finally, USTFIP is the most robust, since its prediction accuracy deprecates at a much lower rate as classical requirements become progressively difficult to meet.
Variability of CO and aerosols plumes from wildfires in the Northern Hemisphere in 2008-2022 using satellite observations.
Authors: Ehret Antoine , Turquety Solène , George Maya , Clerbaux Cathy
Published: February 2023

Wildfires are responsible for significant emissions of greenhouse gases, pollutants and aerosols. In addition to being a large source of carbon monoxide (CO) and carbon dioxide (CO2), they alone account for more than half of black carbon emissions and the majority of primary organic aerosol emissions.Despite proactive fire suppression policies in the Northern Hemisphere (NH), allowing a decrease in fires, especially in Europe, an increase in the number of extreme fires can be noted in recent years. In the NH, this increase is mainly in Western America and boreal regions. The pollution plumes produced during extreme fires can be transported over thousands of kilometers, impacting background pollutant levels on a hemispheric scale. Thus, variability in fire intensity may explain a large part of the spatial and temporal variability of many atmospheric pollutants. For longer lived pollutants, wildfires may significantly increase background levels.In this study, the link between extreme fire weather (high temperature), large fires and background pollution in the Northern Hemisphere is analyzed based on satellite observations. The impact of large wildfires on background levels of CO and aerosols above Europe is studied more specifically. We present the variability of fire frequency in the NH, their intensity and the related emissions using 20 years (2003-2022) of MODIS fire observations analyzed with the APIFLAME model. The link between large events and fire weather is studied using the ERA5 reanalyses and the Canadian Fire Weather Index (FWI). The related impact on the variability of total CO and AOD in the NH is analyzed using 15 years (2008-2022) of satellite observations from IASI/Metop and MODIS/Terra and Aqua, respectively. Finally, plume retro trajectories are computed in order to assess the contribution of the different geographical areas of the NH on the CO and AOD variability.
The Feasibility Assessment of Quick Landslide Identification Methods After Hazards with Sentinel-1 SAR Imagery
Authors: Wang Kuo-Lung , Lin Jun-Tin , Lee Yi-Hsuan
Published: February 2023

In remote sensing of landslide investigation, the interpretation of optical image is the main method at present. However, when a disaster occurs, it is very difficult to obtain images without cloud coverage. For example, Typhoon Lubi in August 2021 and Typhoon Nissa in 2022 caused many landslides and road interruptions. However, due to the cover of clouds and fog, it was impossible to obtain satellite images in time to judge the scale of the disaster. Unmanned vehicles are also affected by weather factors, which greatly increases the risk of flight. Therefore, it is extremely necessary to develop disaster identification methods that are not affected by weather.In this study, the long electromagnetic waves of synthetic aperture radar (SAR) are not affected by cloud and fog to develop a landslide detection model for radar images. The reference range of the location and scale of the landslide can be obtained under bad weather conditions to make up for the weather limitations when evaluating the scope of the disaster with optical images.In this study, the NDSI&RVID method is used as the index for the identification and interpretation of the landslide area, and the analysis and discussion of the landslide area is carried out in combination with multi-time series and different orbital data. The effect of landslide identification is improved by three methods: single-sequence identification and interpretation stacking, multi-time-series index stacking, and multi-time-series image stacking. Among them, better interpretation results can be achieved by stacking multiple time-series images. It is recommended to use the number of 4 images before the disaster and 1 image after the disaster for data interpretation. Although the image pixel classification effect still needs to be improved, the identification rate for landslides of more than 10 hectares can reach more than 90%. In the absence of optical images, it has considerable reference value.
Eerie sounds of Earth’s magnetic field
Authors: Nielsen Klaus , Linden-Vørnle Nikolai , Kloss Clemens , Finlay Chris
Published: February 2023

In October 2022 an audio installation using Data Sonification methods premiered in Copenhagen. The project was a sonic representation of Earth’s magnetic field played on a 32-channel speaker system dug into the ground of a public square. The project was a massive success – particularly online with close to a million plays on ESA’s SoundCloud and thus proved a great opportunity to showcase the important work in Earth Observation done within the Swarm community.The audio installation is an artistic representation controlled by magnetic field data through a sonification method called parameter mapping. The output of the 32 speakers was controlled individually by fluctuations in the magnetic field strength at 32 locations on the globe. Data was taken from the GGF100k – a global field model going back 100.000 years – and condensed into a 5-minute sequence composed of 32 different tracks running simultaneously. Six different parameters were mapped to various qualities of the audio playback (volume, pitch, filter, sample playback speed); these included the three components of the magnetic field at the core mantle boundary, the rate of change, and the field average at surface level.The soundtrack was meant to give the listener an impression of a living planet in constant flux and is build up from recordings of natural sounds in various combinations. This presentation will describe the approach and give a demonstration of the results. In addition, it will briefly discuss data sonification as a method for inclusion and science outreach.
High-resolution map of the upper range limit of trees over the cold and arid region, a case study in the Three-River-Source National Park, Tibetan Plateau
Authors: Xu Jinfeng , Wang Xiaoyi , Lv Guanting , Wang Tao
Published: February 2023

The upper range limit of trees is the most conspicuous boundary on the Earth. However, the publicly available forest extent or forest cover datasets systematically underestimated sparse tree cover, which hindered our recognition of tree limit distribution and its drivers over cold and arid regions. Here, we built a three-step upscaling strategy, that integrates in situ measured vegetation types with spaceborne Light Detection and Ranging (LiDAR), microwave, and Landsat images in a Convolutional Neural Networks (CNN) classification algorithm, to develop a new map of the upper range limit of trees over the Three-River-Source National Park circa 2020 at 30 m resolution. The multi-satellite-based new products consider vertical structure information that could better detect sparse trees and better distinguish between the shrub, grass, and forest. Validation shows our result reveals high consistency with manual interpretations from Google Earth high-resolution images (R2 = 0.97, slope = 0.99, ME = 18 m). Our proposed method provides a fast and effective tree limit mapping solution at the global scale.
H2020ReSET: Monitoring and modelling the hydrological impact of ecosystem restoration scenarios at scales from local to continental using FreeStation and WaterWorld
Authors: van Soesbergen Arnout , Burke Sophia , Mulligan Mark
Published: February 2023

ReSET (Restarting Economy in Support of Environment, through Technology) is an EC H2020 research and development project focused on future and emerging technologies (FET) in Environmental Intelligence (EI). EI brings together multiple data streams, employing human reasoning and machine learning to better understand and manage the environment.As part of ReSET, we are developing and deploying distributed networks of in-field sensors to monitor the hydrological impact of natural flood management, regenerative farming and other ecosystem restoration.  These sensor networks use FreeStation.org, low-cost, internet connected environmental sensing and data logging to provide locally specific evidence for the hydrological impact of a range of restoration investments in different locations and at different scales. More than 100 data loggers  have been deployed for 18 months collecting data every 10 minutes. This provides both capacity to directly analyse the effectiveness of investments in water ecosystem services  and co-benefits for non water ecosystem services and helps develop the understanding to better parameterise these restoration investments in spatial models like WaterWorld.  We apply  the WaterWorld Policy Support System  to assess the hydrological impact of novel scenarios for ecosystem restoration at the national and European scale. As well as ecosystem restoration, a  key  focus is regenerative agriculture (RA) which is a land management technique that involves no or low tillage, the use of cover crops and diverse crop rotations to help restore soil structure to a more natural state, encouraging infiltration and reducing runoff generation. This management technique has the potential to increase the water storage capacity of the soil, thereby reducing downstream runoff generation and flood risk..Our local scale monitoring indicates that restoration of Eurasian Beaver habitat and of farmed soil through reduced tillage have the potential to increase flood storage locally and can reduce flood risk at downstream assets if applied at scale. Our national and continental scale modelling indicates that soil and canopy stores are critical to natural flood management since water body and wetland stores have only local influence and floodplain stores often contain important assets that preclude the use of the floodplain.  Ecosystem restoration has the potential to regenerate Europe's waters, but significant effort will be required to reach the level of restoration that will be needed 
Conversion of IP data and its uncertainty from time-domain to frequency-domain using Debye decomposition
Authors: Hase Joost , Gurin Grigory , Titov Konstantin , Kemna Andreas
Published: February 2023

The time-domain (TD) induced polarization (IP) method is used as an extension to classical DC resistivity measurements to capture information on the ability of the subsurface to develop electrical polarization, which is closely coupled to petrophysical parameters of relevance in hydrogeophysical characterization. In a TD IP measurement, the transient voltage decay between two electrodes is measured after the termination of an injected current between two other electrodes. TD IP measurements are typically analyzed in terms of chargeabilities, while in the frequency domain (FD) polarization responses are measured as complex-valued impedances. The latter can be inverted into a subsurface model of complex electrical resistivity by means of existing tomographic inversion algorithms. In order to apply these FD inversion algorithms to TD IP measurements, the necessity of TD to FD data conversion arises. A suitable conversion approach must transform the measured decay curve into a FD impedance and, preferably, also propagate the corresponding measurement uncertainty from TD into FD. Here we present such an approach based on a Debye decomposition (DD) of the decay curve into a relaxation-time distribution (RTD). Since equivalent formulations of the DD exist in TD and FD, it is possible to compute the FD response from the RTD inverted from the TD response. The corresponding FD data error can be obtained by applying error propagation through all these steps, assuming that the errors on the underlying parameters are normally distributed. To accomplish the DD we implemented a non-linear Gauss-Newton inversion scheme which automatically tunes the regularization strength to achieve a stable FD estimate and FD uncertainty. We test the performance of the inversion scheme in a synthetic study and demonstrate its application to field data on a tomographic TD IP data set measured on the Maletoyvaemskoie field of altered rocks (Kamchatka, Russia), which features epithermal gold deposits of high sulfidation type. The converted tomographic TD IP data set is inverted into subsurface models of complex electrical resistivity at frequencies of 1 Hz and 20 Hz. The proposed conversion approach yields accurate impedance data for relaxation processes which are resolved by the TD measurements. The error propagation scheme provides a reasonable FD uncertainty estimate, as revealed by a Monte-Carlo analysis of the underlying parameter distributions. Propagated FD errors are in agreement with previously established FD error models. The presented methodology to convert TD to FD IP data allows to invert and analyze field data collected with widely used TD instruments in the frequency domain, where the diagnostic potential of electrical impedance spectroscopy can be fully exploited for an improved interpretation.
Modelling the Interaction of Alfvénic fluctuations with Coronal Mass Ejections in the low solar corona
Authors: Sishtla Chaitanya , Pomoell Jens , Kilpua Emilia , Good Simon , Vainio Rami
Published: February 2023

Alfvénic fluctuations of various scales are ubiquitous in the solar wind, with their non-linear interactions and eventual cascade resulting in an important heating mechanism to accelerate the solar wind via turbulent heating. Such fluctuations are also present in other transient & coherent plasma structures such as Coronal Mass Ejections (CMEs), and exhibit varying properties as compared to the solar wind plasma. In this study we investigate the interactions between solar wind Alfvénic fluctuations and CMEs using MHD simulations. We use an ideal magnetohydrodynamic (MHD) model with an adiabatic equation of state. An Alfvén pump wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, and a CME is injected by inserting a flux-rope modelled as a magnetic cloud into the quasi-steady solar wind.We observe that upstream Alfvén waves experience a decrease in frequency and change in the wave vector direction due to the non-spherical topology of the CME shock front. The CME sheath inhibits the transmission of low frequency fluctuations due to the presence of non-radial flows in this region. The frequency of the solar wind fluctuations also affect the steepening of MHD fast waves causing the CME shock propagation speed to vary with the solar wind fluctuation frequencies.
Tales of compacting sand to anticipate strain budget of rupture processes
Authors: Voigtländer Anne , Sikolenko Vadim , Turowski Jens M. , Illien Luc , Bedford Jonathan , Pruß Gunnar
Published: February 2023

Prior to earthquake ruptures and slope failures, accelerated surface deformations can sometimes be observed. To anticipate rupture processes, these deformations are interpreted in terms of a strain budget and its stressors. If the budget exceeds an assumed critical value, rupture happens. But not all components of the budget can readily be inferred from the bulk deformation. For example, elastic strain build-up and other ‘silent’ contributions challenge the predictability of these potential natural hazards. We present preliminary experimental results, focussing on deformation by compaction. We report an analogous experiment of loading and unloading to constrain compaction behaviour, elastic strain-build up, and release to understand their ‘silent’ contributions to the strain budget. As analogue material, we use sand to assess emergent bulk behaviour. Using natural quartz crystals allows to apply in-situ neutron diffraction to measure elastic strain during loading and unloading stages. We find that while compaction and remnant compaction scale linearly with load magnitudes, elastic strain build-up seems to be independent of stresses ≥60 MPa. In addition to the in-situ neutron diffraction experiments, we conducted mechanical compaction tests at ramped load stages and analysed the post-compaction changes of the grain size distribution. With increased loading, the mean grain size decreased, leading to increased bulk density in the compacted portion. Based on these observations, we reason that the linear elastic bulk compaction of our samples is due to non-linear local brittle deformation. There is only limited elastic strain built up during the compaction, which is likely released due to local crushing. Localized failure produces a denser material in which strain can build up more homogeneously, causing rupture at its bulk elastic limit. Our experiments show that deducing or simply converting loading and displacement to stress-strain relationships to establish a strain budget may be inadequate. Silent components that are likely due to non-linear and emergent processes can in the short term lead to local elastic strain energy release or bulk dynamic ruptures. Conceptually, to especially anticipate the timing of slope failures and the magnitude of earthquake ruptures, the hidden costs, e.g. due to localized failure, and internal changes, concerning density or elastic properties, are crucial components that need to be constrained while compiling a strain or energy budget of these processes.
An interactive map platform for groundwater data visualization and real-time numerical modeling
Authors: Ni Chuen-Fa , Lee I-Hsien , Nugraha Gumilar Utamas , Nguyen Thai Vinh Truong
Published: February 2023

Accurate assessment of groundwater resources relies on sufficient measurements and efficient analysis tools. The integrated technologies and multidisciplinary knowledge of groundwater have enhanced the understanding of dynamics in groundwater systems. Taking advantage of wide developments in computer sciences and web services, the web platform provides an excellent open environment for groundwater investigations. Most groundwater-relevant web platforms are mainly focusing on data visualization. The data, such as points, polylines, polygons, and pre-analysis results (i.e., the figures) overlap a street map to indicate the locations of interest and quantify the influenced regions of groundwater hazards. Such a one-way interaction framework has significantly limited the implementations of measurement data and groundwater-relevant applications. The study aims to develop an online web-based platform for groundwater data visualization, temporal and spatial data analysis, mesh generation and flow modeling. The study integrates multiple program languages to bridge the data flow and online visualization. The interactive real-time web environment enables users to screen temporal and spatial measurements on the web map, conduct online data analyses, and develop numerical groundwater models. With a well-designed database and numerous modules for data analyses and modeling, the platform allows users to share data and develop collaborative activities. The built-in analysis tools can also improve the efficiency of groundwater management and decision-making processes.
Modeling Sustainable Intensification of Agriculture under Resource Constraints
Authors: Joseph Julian , Tramberend Sylvia , Luna Gonzalez Diana , Fischer Günther , Kahil Taher
Published: February 2023

Sustainable Intensification of agriculture is a means to meet increasing future food demand in regions with rapidly growing populations and economies. In many of these regions, productivity is currently low. Increasing productivity while limiting additional use of resources such as water and land is therefore key to providing demanded and nutritious food in these countries. To model sustainable intensification, we build an optimization model. In its main economic specification, the objective of the model is to maximize farmer profit while at the same time respecting ecological boundaries. Therefore, constraints of the model are given by land availability and agronomic and climatic constraints to crop growth from the Global Agroecological Zones (GAEZ) method, as well as water availability derived from the Global Hydro-Economic Model (ECHO). The framework can be applied for either a single crop or multiple crops. The results of our analysis provide guidance on where and under which circumstances production of a crop can most efficiently be intensified. This can include the spatial distribution of irrigation or the allocation of several crops to optimally meet estimated demand. Demand is derived from projections of human population, economic growth and income elasticities. We use scenario analysis to examine how optimal sustainable intensification strategies change under different trade regimes for agricultural products and under different levels of climate resilience. Application of the model focuses on the East African extended Lake Victoria Basin (eLVB). In eLVB agroecological conditions are favorable for a wide range of crops, sufficient water is available in several sub-basins and population and food demand are projected to rapidly expand.
Biodiversity threatened by increasing mountain forest loss
Authors: He Xinyue , Zeng Zhenzhong , Holden Joseph , Spracklen Dominick
Published: February 2023

Mountain forests are currently experiencing severe losses in many parts of the world because they are sensitive to climate change and anthropogenic pressures. However, the distribution of the world’s mountain forest loss and how it has changed in the 21st century remain unclear. Here, we conducted a global analysis on mountain forest loss by using multiple high-resolution remote sensing datasets. Our results show that the total forest loss over global mountains during 2001–2018 was 78 million ha (7% of the mountain forest area in 2000) and that annual mountain forest loss tripled by 2016. Spatially, the largest loss area occurred in the tropical and boreal mountain forests, particularly in Southeast Asia, Russia, and Canada. We find many mountain regions with considerable losses in forest cover are also biodiversity hotspots, suggesting these areas need more attention and require protection. Our findings indicate that the interaction of mountain forest changes and biodiversity impact should be incorporated into future impact assessments.
Geodynamic-mineralogical predictions of mantle transition zone seismic structure
Authors: Papanagnou Isabel , Schuberth Bernhard S. A. , Thomas Christine
Published: February 2023

The mantle transition zone (TZ) is expected to influence vertical mass flow between upper and lower mantle as it hosts a complex set of mineral phase transitions and an increase in viscosity with depth. Still, neither its seismic structure nor its dynamic effects have conclusively been constrained. The seismic discontinuities at around 410 and 660 km depth ('410' and '660') are classically associated with phase transitions between olivine polymorphs, the pressure of which is modulated by lateral temperature variations. Resulting discontinuity topography is seismically visible and can thus potentially provide insight on temperature and phase composition at depth. Besides the olivine phase changes, the disassociation of garnet may additionally impact the 660 at higher temperatures. However, the volume of material affected by this garnet transition and its dynamic implications have not yet been quantified.This study presents hypothetical realizations of TZ seismic structure and major discontinuities based on the temperature field of a published 3-D mantle circulation model for a range of relevant mineralogies, including pyrolite and mechanical mixtures (MM). Systematic analysis of these models provides a framework for dynamically informed interpretations of seismic observations and gives insights into the potential dynamic behaviour of the TZ. Using our geodynamic-mineralogical approach we can identify which phase transitions induce specific topographic features of 410 and 660 and quantify their relative impact. Areal proportions of the garnet transition at the 660 are ∼3 and ∼1 per cent for pyrolite and MM, respectively. This proportion could be significantly higher (up to ∼39 per cent) in a hotter mantle for pyrolite, but remains low (< 2 per cent) for MM. In pyrolite, both slabs and plumes are found to depress the 660 —with average deflections of 14 and 6 km, respectively— due to the influence of garnet at high temperatures indicating its complex dynamic effects on mantle upwellings. Pronounced differences in model characteristics for pyrolite and MM, particularly their relative garnet proportions and associated topography features, could serve to discriminate between the two scenarios in Earth.
Hydroacoustic Monitoring of Earthquake Sequences on the Blanco Oceanic Transform Fault
Authors: Liu Hui , Tan Yen Joe , Dziak Robert
Published: February 2023

Understanding how earthquakes initiate lies at the heart of earthquake physics and analyzing foreshock sequences is one way to probe the initiation process of large earthquakes. A few oceanic transform fault (OTF) earthquakes have been observed to have more foreshocks compared to continental earthquakes. It has also been proposed that OTFs accommodate plate motion primarily by slow creep instead of rapid seismic slip, though with significant along-fault variability. These characteristics make OTFs unique laboratories for probing the physical processes underlying foreshocks and their relations with slow slip events. However, in the past, detailed studies at OTFs have been limited due to their distance from land-based seismic stations. Since 2015, small arrays of ocean-bottom seismometers and hydrophones have been permanently deployed on cabled seafloor observatories in the northeast Pacific Ocean, allowing for monitoring of seismicity on the Blanco Transform Fault (BTF) using the earthquake’s radiated hydroacoustic energy (T-phase). T-phases propagate through the SOFAR channel in the world’s oceans with little attenuation, allowing for the detection of low-magnitude earthquakes at large distances. In this study, we apply a suite of techniques to detect, associate, and locate foreshocks and aftershocks of large mainshocks occurring along the BTF since 2015. We define a mainshock as the largest event occurring within two weeks and a radius of 50 km. 19 Mw  5.0 mainshocks are selected from the GCMT catalogue. However, we are only able to analyze 12 mainshocks due to data availability issues. We use the STA/LTA algorithm to detect T-phase arrivals one week before and after each mainshock through the continuous waveforms recorded on both OBSs and hydrophones. For each detection, we then use the relative station arrival times compared to the mainshock to make sure we only retain events close to the mainshock, i.e., its foreshocks and aftershocks. We then employ the GLOBAL mode Non-Linear Location (NLLoc) program for event localization using a 3D ocean sound velocity model. Compared to the IRIS catalogue which only has a minimum detection level of magnitude 3, lower-magnitude T-phase events are successfully detected by our method. Using our T-phase catalogue, we quantify how the BTF sequences compare with earthquake sequences observed at continental transform faults and test the various proposed models to explain foreshock spatiotemporal behavior and the partitioning of seismic and slow slips along the BTF.  
Identification of hot/cold spots inside the Surface Urban Heat Island of the main cities in North-Eastern Romania using Landsat imagery
Authors: Cretu Stefanel-Claudiu , Sfica Lucian , Amihaesei Vlad-Alexandru , Breaban Iuliana-Gabriela , Ichim Pavel
Published: February 2023

Urban Heat Island (UHI) is caused by inadvertent climate modification due to human spatial concentration, being generally defined as the difference in temperature between urban areas and their rural surroundings. However, seen at fine spatial resolution, the heat island seems rather to look like an archipelago of hot spots delimited by colder areas. This study analyses the Surface Urban Heat Islands (UHISurf) of 16 cities located in Romania’s North-East Development Region for the identification of these hot and cold spots.For each city, in order to identify UHISurf’s hot and cold-spots, Landsat series of satellites were used due to their potential to provide Land Surface Temperature (LST) product at a high spatial resolution, which is commonly required for micro or local scale studies. For this purpose, LST is derived from the Landsat 4, 5, 7, and 8 (1988-2021), collection 1 (using the Statistical Mono-Window algorithm), implemented in Google Earth Engine platform.For hot /cold spots identification, Hot Spot Analysis (Getis-Ord Gi*) tool from ArcGIS Pro 3.0 was used. This tool calculates the Getis-Ord Gi* statistic for each feature in a dataset by looking at each feature within the context of neighboring features. To be classified as a statistically significant hot spot, a feature will have a high value and has to be surrounded by other features with high values. The local sum for a feature and its neighbors is compared proportionally to the sum of all features and a statistically significant z-score results. The larger the z-score is (positive), the more intense the clustering of high values defined as hot spots. The smaller the z-score is (negative), the more intense the clustering of cold spots. When the False Discovery Rate (FDR) correction is applied, statistical significance is adjusted to account for multiple testing and spatial dependency.This procedure was applied for each of 16th cities, summing up 10900 images which cover an area of 2526,8 km2. LST is strongly controlled by surface properties (radiative, thermal, geometric, moisture and aerodynamic), these giving a greater surface temperature variability compared to air temperature, particularly during the day. Inside the identified hot spots, the LST is with 8-10C higher than the mean of UHISurf LST. Generally, light industrial, warehouses and transportation infrastructure (airports) are often relatively hot-spots, while cold-spots, are obviously more heavily vegetated areas, water bodies and areas of well-watered vegetation, but their futures are related to each city characteristics. The obtained results are designated to be used as the main assessment of urban heat island, delivering for stakeholder a clear image of the target regions inside the cities for the policies dedicated to the mitigation of the urban heat island effect.