bluuebunny/crossref_metadata_2025 huggingface dataset:
Uncovering Stick-Slip Events: Denoising Cryoseismological Distributed Acoustic Sensing Data with an Autoencoder
Authors: Zitt Johanna , Paitz Patrick , Walter Fabian , Umlauft Josefine
Published: March 2024

One major challenge in cryoseismology is that signals of interest are often buried within the high noise level emitted by a multitude of environmental processes. Specifically, basal sources such as stick-slip events often stay unnoticed due to long travel paths to surface sensors and accompanied wave attenuation. Yet, stick-slip events play a crucial role in understanding glacier sliding and therefore, it is of great interest to investigate their spatio-temporal evolution, across the entire glacier from its ablation to its accumulation zone.Distributed Acoustic Sensing (DAS) is a technology for measuring strain rate by using common fiber-optic cables in combination with an interrogation unit. This technology enables us to acquire seismic data over an entire glacier with great spatial and temporal resolution. To unmask stick-slip events, new techniques are required that effectively and efficiently denoise large cryoseismological DAS data sets. Here, we propose an autoencoder, a type of deep neural network, which is able to separate the incoherent environmental noise from the temporally and spatially coherent signals of interest (e.g., stick-slip events or crevasse formations). We trained the autoencoder in order to denoise a DAS data set acquired on Rhonegletscher, Switzerland, in July 2020. Due to the highly active and dynamic cryospheric environment as well as non-ideal cable-ground coupling the collected DAS data are characterized by a low signal to noise ratio compared to classical point sensors.Several models were trained on a variety of data subsets, differing in recording positions (ablation or accumulation zone), event types (stick-slip event or surface event) and the quantity of training events. We compare and discuss the denoising capabilities of these models with several metrics, such as inter-channel coherence, similarity between seismometer and DAS recordings, and visual assessment. This evaluation is conducted while considering different data types in a qualitative and quantitative manner. All models show an increase in inter-channel coherence of the seismic records after denoising. Further, all models uncover previously undetected stick-slip events, whereby models trained on manually picked training data perform better than models trained on randomly picked training data. We believe that the application of our models can improve the understanding of basal stick-slip information in cryoseismological DAS datasets, potentially uncovering previously hidden information.
A simple model for beaching and resuspension of plastic debris
Authors: Mørk Jenny Margareta , Nordam Tor , Breivik Øyvind
Published: March 2024

When modelling the transport of plastics in the marine environment it is common to use a Lagrangian modelling framework. The movement of the particles is governed primarily by advective and diffusive transport, but the plastics are also subjected to a number of other physical, chemical, and biological processes that affect their fate. For transport in coastal regions, one of the more important processes is the interaction between particles and the shoreline.Currently, there is no consensus on how to handle shoreline interactions in particle tracking models, and many resort to over-simplified descriptions such as considering a particle to be permanently beached at the position where it first hits land, or not allowing for beaching of debris at all. However, it is well-known that a lot of floating marine litter ends up on beaches, and mark-recapture studies of plastic on beaches around the world show that there can be considerable turnover in the litter on a beach. Furthermore, these studies show that both beaching and resuspension rates vary both over different beaches, and over different seasons at the same beach, indicating that these processes depend on several different factors, such as wind and wave conditions, beach morphology, and likely also the shape, size, and density of the object. Thus, in order to accurately predict the accumulation sites for floating plastic debris in coastal regions, more care should be put into modelling shoreline interactions.Here we investigate a toy model for beaching of floating plastic debris, implemented in an idealised Lagrangian framework with analytically defined current, spatially constant wind and diffusivity, and a domain bounded on one edge by a straight, homogeneous shoreline. We implement different strategies for handling the beaching and resuspension of debris and compare the resulting distribution of particles. There is currently insufficient experimental data on the extent to which the different factors affect the beaching and resuspension processes for different kinds of plastic objects, so the purpose of this work is not to reproduce actual conditions, but rather to investigate the effect of the choice of beaching and resuspension strategies on the simulation results. We investigate e.g. a simple resuspension model where particles have an average lifetime on the beach, as well as a wave-based model where the beaching and resuspension is affected by randomly generated wave heights. 
Exploring the hydrothermal vent field of Milos Island in Aegean Seausing novel radiation instrumentation
Authors: Siltzovalis Georgios , Madesis Ioannis , Lagaki Varvara , Mertzimekis Theodoros J. , Krassakis Pavlos , Kazana Stavroula , Nikolopoulos Konstantinos
Published: March 2024

Radioactivity monitoring in the marine environment exhibits various challenges. First and foremost, the water-induced attenuation substantially limits the detection ability and range of the sensors. Additionally, the harshness and remoteness of underwater locations pose significant obstacles to existing technological solutions towards dense and extended radioactivity mapping of the oceans. The highly ambitious EU FET Proactive Research Programme RAMONES (Radioactivity Monitoring in Ocean Ecosystems) is aiming towards overcoming existing limitations by developing and deploying novel underwater radiation-sensing instruments, enabling direct correlation of marine radioactivity with underwater geological and geochemical processes.The present study will focus on the analysis of experimental data collected during field experiments conducted in the extended hydrothermal vents of Milos, an island located on the south Aegean Sea that is part of the Hellenic Volcanic Arc. The shallow active hydrothermal system of Milos is associated with calc-alkaline volcanic rocks from basaltic andesites to dacites, and rhyolites that have been deposited over several cycles of volcanic activity. Novel portable γ-detectors based on lightweight CdZnTe crystals, were deployed to acquire in situ measurements from coastal locations at the eastern part of the island. Complementary sediment samples were collected to offer baseline NORM (Naturally Occurring Radioactive Material) levels from Milos Island having attracted a lot of attention recently due to its role as a potential geohazards source. These measurements are used to benchmark the γ spectrometers and prepare them for underwater operation aboard autonomous underwater gliders. Collected data will feed a prototype Risk Information System (RIS) titled as POIS2ON (PrOtotype Information System for SOcioecoNomic stakeholders). POIS2ON database will include datasets accompanied by geoinformation to be visualized though NORM levels heat maps, as well as support detailed Monte Carlo simulations to evaluate the radiation doses on local marine ecosystems.
Fate and effects of nitrogen added in a long-term experiment to a sub-alpine forest in Switzerland
Authors: Schleppi Patrick
Published: March 2024

Atmospheric nitrogen deposition was artificially increased for 27 years (1995-2022) by sprinkling rain water enriched with NH4NO3 (+22 kg ha-1 y-1 N) to a small headwater catchment in a spruce (Picea abies) forest growing on gley soils at Alptal (central Switzerland). This treatment was compared to a control in a paired catchment design. Nitrate leaching increased already during the first rain events after starting the treatment and continued to increase within the first 5 years. Later, it increased again markedly after part of trees had been girdled then felled in 2010. As shown by 15N labelling, most of the added N remained in the soil. In plots receiving the same treatment, this lowered the C/N ratio, changed the composition of the fungal community and tended to reduce the total microbial biomass, the abundance of Collembola and soil respiration. Soil acidification was observed in those plots located on small mounds but was effectively buffered in topographical depressions. Denitrification was clearly increased, but other processes like mineralisation were not significantly affected. Over time, trees took up about 1/10 of the added N and used it mainly to build larger needles. Their growth was slightly improved, presumably by a better use of the light in their relatively open canopy. Both the soil microbiote and the trees showed signs of limitation by other nutrients like P and Mg, but the poor aeration remained the major limiting factor of the gley soils on this site.
Warming-induced phenological mismatch between trees and shrubs explains high-elevation forest expansion
Authors: Liang Eryuan , Li Xiaoxia , Camarero J. Julio , Rossi Sergio , Zhang Jingtian , Zhu Haifeng , Fu Yongshuo H. , Sun Jian , Wang Tao , Piao Shilong , Peñuelas Josep
Published: March 2024

 Despite the importance of species interaction in modulating the range shifts of plants, little is known about the responses of coexisting life forms to a warmer climate. Here, we combine long-term monitoring of cambial phenology in sympatric trees and shrubs at two treelines of the Tibetan Plateau, with a meta-analysis of ring-width series from 344 shrubs and 575 trees paired across 11 alpine treelines in the Northern Hemisphere. Under a spring warming of + 1°C, xylem resumption advances by 2–4 days in trees, but delays by 3–8 days in shrubs. The divergent phenological response to warming was due to shrubs being 3.2 times more sensitive than trees to chilling accumulation. Warmer winters increased the thermal requirement for cambial reactivation in shrubs, leading to a delayed response to warmer springs. Our meta-analysis confirmed such a mechanism across continental scales. The warming-induced phenological mismatch may give a competitive advantage to trees over shrubs, which would provide a new explanation for increasing alpine treeline shifts under the context of climate change.
Alternative approaches to the velocity of climate change: assessment against observations
Authors: Kasparian Jérôme , Moinat Laure , Gaopnenko Iaroslav , Goyette Stéphane
Published: March 2024

Climate change causes shifts in distribution ranges of species. The velocity of these shifts is often related to that of climate change, such as the poleward shift of the isotherms. However, species range shifts are not solely determined by climate parameters. Short-term meteorological values, topography, and other barriers also play a role. Moreover, the magnitude and direction of the climate velocity are not defined univocally. They depend on implicit assumptions that underlie the calculations, particularly in determining the direction of the velocity vector. The classical gradient-based definition of climate change [1] displays limitations, in particular local divergence [2], which led us to recently introduce an alternative method maximising the regularity of the velocity field, named Monte-cArlo iTerative Convergence metHod (MATCH) [3].
Since the latter stems from mathematical arguments, its relevance to ecology requires careful assess- ment. We consider North-American birds based on the Audubon Christmas Bird Count as well as marine species recorded in the North-East Atlantic region of the NOAA fisheries survey. For each species, the centroid of the distribution area is determined at two time ranges, and its shifting velocity, in magnitude and direction, is deduced. We also calculate the shift of the isotherms for ground and sea-surface tem- peratures, respectively, at each observation spot, and deduce an average shifting velocity for both the Gradient-based and the MATCH methods.
When comparing the respective shifts of the ranges of species and of climate, we only found a significant positive correlation between latitudinal shift of marine species and their climate counterpart, as calculated with the MATCH approach. Neither the classical gradient method, nor longitudinal shifts, nor bird range shifts displayed significant correlations. Our results therefore suggest that the MATCH approach may provide more ecologically relevant velocity fields. We also confirmed previous observations that marine species better track temperature evolutions than terrestrial ones. Such assessment may help anticipating species range shift and designing conservation strategies.
References
1. S. R. Loarie et al. Nature 462, 1052 (2009)
2. J. Rey, G. Rohat, M. Perroud, S. Goyette, J. Kasparian, Env. Res. Lett. 15, 034027 (2020)
3. I. Gaponenko, G. Rohat, S. Goyette, P. Paruch, J. Kasparian, Sci. Rep., 12, 2997, (2022)
Assessing the Effect of Droughts on Complex Multi-sector Water Systems
Authors: Sangiorgio Matteo , Zaniolo Marta , Giuliani Matteo , Castelletti Andrea
Published: March 2024

In recent years, climate change has significantly intensified the frequency and severity of drought events. Rising temperatures, altered precipitation patterns, and changing weather dynamics have led to more prolonged and intense droughts altering water availability and exacerbating tradeoffs, especially in complex multi-sector water systems.An archetypal example of this situation is the Lake Como water system, in the north of Italy. Lake Como is operated to provide water downstream to the agricultural sector, control floods on the lake shores, and contrast low water levels that would negatively impact navigation and aquatic ecosystems. The conflict between the interests of these sectors is expected to exacerbate in the years to come due to the evolving hydroclimatic regimes. Among different adaptation options considered by the regional authority, we investigate the potential expansion of the lake's active storage capacity enabled by the recent construction of flood mobile dykes.Here, we contribute a framework for evaluating the impact of droughts on multiple water users. Specifically, we adopt a synthetic weather generator to create multiple streamflow ensembles (scenarios) controlling the drought’s frequency, duration, and intensity. Drought features are then linked to impacts (e.g., agricultural deficit) using a simulation model of the lake. Failure thresholds are defined for each impact indicator to set the minimum level of performance acceptable to each sector. Finally, a logistic classifier is used to identify the combination of drought features leading to a system failure.Our results show that system failures can be accurately estimated using a linear combination of drought frequency, duration, and intensity. The combined effect of these three characteristics, rather than the extreme values of one of them, is responsible for system failure. Our analysis also proves that storage expansion is fundamental to reduce the downstream deficit, as well as to prevent most of the flood events.
Exposing Underestimated Channelized Basal Melt Rates in Antarctic Ice Shelves
Authors: Zinck Ann-Sofie Priergaard , Lhermitte Stef , Wouters Bert
Published: March 2024

Ice shelves play a pivotal role in stabilizing the Antarctic ice sheet by providing crucial buttressing support. However, their vulnerability to basal melting poses significant concerns for ice sheet and shelf stability. Our study focuses on assessing basal melt rates at a 50 m posting of 12 ice shelves where earlier studies have identified high melt rates. We make use of the Reference Elevation Model of Antarctica (REMA) strips to generate surface elevation- and melt rates using the Basal melt rates Using Rema and Google Earth Engine (BURGEE) methodology.BURGEE reveals higher melt rates in areas with thinner ice than existing remote sensing basal melt products. This is for instance the case for basal channels on both Dotson, Totten and Pine Island ice shelves. Modelling studies have already shown that remote sensing inferred basal melt rates are underestimated at the thinnest part of basal channels, and that this underestimation scales with resolution coarsening. Since the thinner parts of an ice shelf also represent its weakest part, it is crucial that we capture its melting well to fully grasp the vulnerability of the ice shelf.Our work, therefore, represents a crucial step in uncovering the vulnerability of Antarctic ice shelves. By exposing detailed melting patterns, particularly in areas like basal channels, we highlight not just extensive melting but also potential weak points, significantly contributing to our understanding of ice shelf stability. These findings bear substantial importance in comprehending the broader implications of ongoing climate changes on Antarctica's ice sheet integrity and, consequently, global sea levels.
New insight into the surface composition of Zhurong landing area
Authors: Zhang Qing , Carter John , Vincendon Mathieu , Poulet François , Pineau Maxime , Guo Lin , Luo Yuxuan , Liu Dawei , Bibring Jean-Pierre , Liu Jianjun , Li Chunlai
Published: March 2024

The Zhurong rover conducted in-situ spectral investigations of southern Utopia Planitia, where orbital observations revealed the presence of spectrally featureless dust. However, in-situ reflectance spectra collected by the Short Wave Infrared (SWIR) spectrometer exhibit hydrated features for all observations along the traverse. These features have been interpreted as being associated with groundwater (Liu Y. et al., 2022) or ocean (Liu C. et al., 2022; Xiao et al., 2023) or atmospheric water (Zhao et al., 2023). Here, we combine the Multispectral Camera (MSCam) and SWIR data to characterize the spectra of landing site and provide some new insights into the surface composition diversity.Multispectral images suggest that most of surfaces are consistent with the presence of dust whereas a few of rock surfaces exhibiting dark tones are compositionally distinct. The co-observational SWIR data can be used to further constrain the surface compositions. With Principal Component Analysis (PCA) and unmixing analysis of the SWIR data, we found that these dusty surfaces are ubiquitously characterized with faint 1900 and 2200 nm absorptions and the dark rock surfaces exhibit strong blue slopes in the NIR.The hydrated dust features seem to contrast with previous knowledge, that the dust does not exhibit obvious NIR hydration features from orbital observations. Such discrepancies were also observed at Jezero crater, where the fine soils or dusty rocks exhibit a 1900 nm H2O absorption but without 2200 nm band (Mandon et al., 2023). Spectral variation may reflect distinct surface dust compositions between the Perseverance and Zhurong landing site, indicating different dust reservoirs or dust alteration processes. The surface dust of different sites may be mixtures of globally well-mixed fine materials and local/regional distinct hydrated phases. Another possibilities is that the dust underwent different post-deposition aqueous alteration.The dark rock surfaces may represent less dust-coated surfaces. The strong blue slope features have been previously attributed to coatings on a dark substrate. Furthermore, the morphological properties show that these surfaces exhibit relatively fragile surface context, consistent with surface coatings or rinds.
Identifying uncataloged low-frequency earthquake sources with deep learning
Authors: Münchmeyer Jannes , Giffard-Roisin Sophie , Malfante Marielle , Frank William , Poli Piero , Marsan David , Socquet Anne
Published: March 2024

Tectonic faults exhibit a wide spectrum of processes releasing stress: from fast earthquakes to slow deformation. Mapping smaller-scale slow deformation directly is challenging because of the limited signal-to-noise ratio of geodetic recordings. Instead, we need to rely on other telltale signs of slow deformation. Low-frequency earthquakes (LFEs) are such signs: a class of seismically observable signals that coincide with slow deformation.However, detecting LFEs is challenging due to their emergent nature and generally low magnitude. The most common method for LFE detection is template matching. Due to the need for waveform templates, this method is specific to a set of LFE sources and seismic stations. This limitation renders the template matching unable to discover uncataloged sources or detect LFEs in regions without prior known LFE activity.Here, we present a novel, deep learning method for detecting LFEs. Our method detects phase arrivals from LFEs, allowing to detect them with a workflow closely modeled after a standard earthquake detection workflow. In contrast to template matching, the deep learning method is substantially more flexible and can generalise to unknown LFEs and even across world regions. We apply our method to a diverse set of regions, including regions with previously known LFE activity, such as Cascadia and Nankai, and without known LFE activity, such as Northern Chile.
A coupled discrete-continuum approach to simulating CO2 migration and dissolution in porous media 
Authors: Ashmore Nicholas , Molnar Ian , Gilfillan Stuart , Krol Magdalena
Published: March 2024

Carbon capture and storage (CCS) has emerged as a principal emissions reduction technology for the energy transition. Its effectiveness hinges largely on the security of the storage reservoir, which may be susceptible to leakage through permeable pathways such as abandoned wells and faults. Storage failure presents risks of environmental impacts, increases in atmospheric carbon emissions, reduces both the value of carbon credits and public confidence in CCS as a viable technology for the energy transition. Given the importance of storage security, our understanding of CO2 leakage and its fate and transport in overburden must be improved to help in the prediction, detection and assessment of leaks. Shallow groundwater monitoring for dissolved gases can be complicated by multicomponent mass transfer dynamics in the subsurface. As CO2 migrates through the subsurface, much of the mass will partition from the gaseous to the aqueous phase, and conversely background dissolved gases present in groundwater such as N2 and O2 may partition to the gaseous phase, impacting both the evolution of dissolved gas concentrations and the persistence of free-phase gas in the subsurface. This process may also impact the performance of noble gas tracers in groundwater monitoring techniques. There is therefore a need for numerical models capable of accurately predicting the fate and transport of CO2 in the subsurface. However, traditional multiphase flow models struggle to describe the buoyant unstable gas flow regime expected at leak sites, dominated by gravity and capillary forces.Unstable gas flow is characterized by discontinuous gas clusters and sharp variations in gas saturations in space, in contrast with the smooth variation in gas saturation predicted by continuum multiphase flow models. Discrete approaches such as macroscopic invasion percolation (MIP) are better equipped to model unstable gas flow, however they are limited by assumptions of instantaneous gas movement. ET-MIP (Electro-thermal MIP) is a general purpose model which couples continuum-based electrical, thermal, groundwater and chemical species modules with a discrete MIP gas flow module. This coupled approach allows for accurate simulation of slow gas displacement characteristic of shallow subsurface gas releases while simultaneously predicting the dissolution of CO2. ET-MIP has been validated against bench scale experiments and shown to accurately predict gas generation, multiphase transport and capillary trapping – all mechanisms which govern the fate of CO2 in the subsurface. This talk will present comparison of ET-MIP with a bench-scale CO2 injection and dissolution experiment and a sensitivity study showing the effects of key model parameters on CO2 migration. Findings highlight the benefits of using a discrete-continuum coupled approach for simulating CO2 migration in porous media, and the importance of considering background dissolved gases in the subsurface.
A stochastic landscape evolution model framework for debris flow and fluvial processes
Authors: Liu Dingzhu , Tang Hui , Braun Jean , Turowski Jens
Published: March 2024

Debris flow is an important process that shapes steep landscapes, connecting the hillslopes and fluvial domains. Yet, it is unclear how debris flows quantitatively influence the topography. Here, we propose and develop a new framework considering debris flows as stochastic processes in long-term landscape evolution. We assume that debris flows occur randomly in time with different initial debris flow volumes, which we model using five different distribution functions. Debris flows propagate along the channel and increase their volume by eroding additional material using deterministic equations. The model predicts the slope-area relationship that is generally assumed to be indicative of debris-flow-dominated landscapes. We suggest a new equation to fit the slope-area relationship, including both debris flow and fluvial domains. This equation features a total of five metrics, two of which are power law exponents, two are representative areas, and one representative slope. The topography in the debris flow-dominated domain is sensitive to the properties of the debris flow, e.g., the initial volume of debris flow, frequency, erosion coefficient, Manning coefficient, uplift rate, and channel width and length. The representative slope and area are primarily sensitive to the total initial volumes of the debris flow, and secondarily to the frequency of occurrence of debris flows. The type and shape parameters of distributions and the debris flows’ volume and frequency have limited effects on the slope-area relationship.
Escalate Dry-hot compounded fires threaten Eurasian drylands
Authors: Yu Huiqian
Published: March 2024

Compound climate extreme events has inflicted enormous damage since it amplifies their impacts on societies and ecosystems. However, it remains challenging to quantify its interaction and influences due to the vulnerability of drylands. We quantified the spatial and temporal pattern change, climate drivers of fire during 2001-2020 and investigated the interaction between the dry-hot conditions and fire events. The results show that fires mostly occurred in spring and autumn among three typical hotspots located in Southern of the East Europe and Central Asia, northeastern of East Asia, and Indian Peninsula. Cropland fires and grassland fires occurred mostly, followed by forest and shrub and savana fires. The average fire burned area decreased by 0.30 km2/yr in the Eurasian dryland during 2001-2020, while dry-hot compounded fires burned area increase in 0.78 km2/yr. Temperature, precipitation and wind are the main explanatory factors, while lighting is the most important variable around the Black Sea. Dry-hot condition in early stage will increase the frequency and intensity of fire, mainly through affecting the fuel flammability and abundance. Our findings highlight the importance to understand the interrelated co-occurring climate extremes, and further efforts for monitoring and take action to reduce its threat.
Centennial Total Solar Irradiance variation : a paradigm shift for Sun-Climate research.
Authors: Dewitte Steven
Published: March 2024

A variation of the solar energy received by the earth – quantified by the Total Solar Irradiance (TSI) – is a radiative forcing for climate changes on earth. Since the 1976 Science paper by J. Eddy, solar-climate research has been dominated by the paradigm that solar activity and TSI have been slowly increasing since the Maunder Minimum - extending from about 1645 to 1715 – and the present, which was believed to be a Modern Solar Maximum. If this paradigm were valid, over the last 50 years, when most of the global warming has occurred, this warming would be partly due to anthropogenic greenhouse gas warming, and partly due to natural solar warming.However, evidence has been accumulating against the ‘Modern Solar Maximum paradigm’. Based on this evidence, recently a new reconstruction of the centennial TSI variation from 1700 to 2020 was published. This new centennial TSI reconstruction is nothing less than a paradigm shift for Sun-Climate research. Following the new TSI reconstruction, the TSI did not gradually increase over the last 320 years, but rather varied with a long term periodicity of 105 years, and currently we are near the minimum of this 105 year variation. Therefore over the last 50 years, the sun did not contribute to global warming, but rather tried to cool the earth, partly counteracting greenhouse gas warming. Since we are near the minimum of the 105 year variation, we can expect a trend reversal and for the next 50 years we can expect that the sun will contribute to global warming, making it more difficult for mankind to reach the goals of the Paris Climate Agreement, in order to avoid catastrophic climate change.
Artistic engagement with a deglaciating world
Authors: Nicholson Lindsey
Published: March 2024

Artists, sometimes within activism, have produced work engaging with the timescales of glaciers, the environmental records stored inside them, their apparent remoteness, melting and its connection to human activities, as well as using the medium of ice in symbolic ways. By considering examples of how artists have worked with the theme of the ongoing deglaciation of Earth and its consequences, I showcase some ways in which artistic interventions have the power to raise awareness and translate scientific knowledge into graspable reality.Thereafter, I provide a personal reflection of working at the interface of science and art in my own work as a glaciologist and as a practicing artist exploring properties of natural ice: I show a selection of my projects from recent years, in which I attempted to tackle the topics of human responsibility and choices; potential misplacement of ecological grief; and irreversibility through the lens of natural ice on Earth. Using these works as examples I discuss the extent to which integrating artistic and scientific research influences my practice of both. 
Classifications of atmospheric circulation patterns as a tool for explaining asymmetry of day-to-day temperature difference
Authors: Huth Radan , Stryhal Jan , Krauskopf Tomáš
Published: March 2024

Classification of atmospheric circulation patterns has been a major powerful tool in synoptic climatology for a long time. Recently, its generalization has been introduced, which consists in developing geographically sliding classifications, i.e., independent classifications centred over individual gridpoints of a regular grid.We employ such a tool in an attempt to explain the asymmetry of day-to-day temperature differences (DTDs). DTD is defined simply as a difference of daily temperature between two consecutive days. DTD in Europe is asymmetric: its skewness is negative over most of Europe in summer, while in winter, there is a tendency for a positive skewness to occur in the north and for negative skewness to occur in the south and over the British Isles.We employ the ERA5 reanalysis as a major data source of both circulation and temperature data and the ECA&D station database for verification of temperature skewness in ERA5. Daily maximum temperature in summer and daily minimum temperature in winter are analyzed. Atmospheric circulation is characterized by sea level pressure, which is subject to classification by the Jenkinson-Collison (JC) method at all gridpoints over the European continent with spatial resolution of 2.5° x 2.5°. The JC method is based on types pre-defined by the strength, direction, and vorticity of geostrophic flow. We utilize its versions with 27 types (full version) and 11 types (with 8 directional types, two vorticity-based types and one undetermined for a weak flow). Under each type and at every gridpoint, we count small negative and small positive DTDs (small DTDs defined approximately as central 50% of its distribution). Types with the largest difference between small positive and small negative DTDs (i.e., with the largest asymmetry in small DTDs) are then identified.A general behaviour, characteristic for the majority of European landmass, can be summarized as follows: Anticyclonic types, types with weak flow, and types with warm advection from south to southwest directions contribute to the asymmetry of Tmax DTD in summer, while anticyclonic types and types with cold northerly to northeasterly advection contribute to the Tmin DTD asymmetry in winter. Nevertheless, under specific conditions (upwind or leeward side of mountains, seashore, valley), any of the 11 JC types can occur among the three that most support the DTD asymmetry.
Risk, Ethics, and Law: A framework (E4Rs) to understand disasters, learned through response to earthquake disasters in Aotearoa New Zealand, Italy, and Nepal. 
Authors: Shrestha Shakti Raj
Published: March 2024

In disaster science, the discussions predominantly stem from the various notions of risk and associated concepts. While understanding risk is an undeniable necessity to comprehend disasters, it is inadequate. This is because, risk only provides an understanding of what is, but it doesn’t describe what could be done and what should be done. As such, there are additional parameters that needs to be included to fully capture the complexities of disaster risk reduction. To this end, it is argued that disasters need to be framed through additional lens of law and ethics that interact with the concepts of risk. A framework, termed Ethics for 4Rs (E4Rs) where 4Rs represent the 4 phases of disaster cycle (reduction, readiness, response, and recovery), is proposed where the three main concepts: risk, ethics, and law interact continuously. Additionally, this framework emphasizes the need to explicitly express the importance of our values, i.e., ethics as disasters are fraught with difficult decisions. This theoretical framework was derived based on understanding gained through studies on the use of post-earthquake cordons as a response and recovery strategy following major disasters in three countries: Aotearoa New Zealand (Christchurch earthquake 2011), Italy (L’Aquila earthquake 2009), and Nepal (Gorkha earthquake 2015). For the case studies, a qualitative research methodology was used for data collection, where 44 experts from varying backgrounds such as politicians, emergency managers, city council members, police, community leaders among others were interviewed. The development of this framework has also been supported through review of ethical concepts from health sciences, in particular public health sciences. This is because discussions on ethics in relation to disasters are limited in literature where as they have been developed more thoroughly in public health sciences. Although, there are differences in disasters due to natural hazards and public health events such as a pandemic, the complexity, urgency, scale and the need to make difficult decisions remain the same and are comparable. Finally, it is suggested that this framework will bring about discussion on disasters and ethics where a significant gap remains in the current disaster science discourse.
GGOS Bureau of Products and Standards: Recent activities and future plans
Authors: Angermann Detlef , Gruber Thomas , Michael Gerstl , Robert Heinkelmann , Urs Hugentobler , Laura Sanchez , Peter Steigenberger
Published: March 2024

The GGOS Bureau of Products and Standards (BPS) supports the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) in its goal to provide highly accurate, consistent, and long-term stable geodetic products needed to monitor, map, and understand changes in the Earth’s shape, rotation, and gravity field. A key objective of the BPS is to keep track and to foster homogenization of adopted geodetic standards and conventions across all IAG components for the generation of geodetic products. This includes the interaction with the IAG Services and other entities that deal with standards and conventions, such as the Conventions Center of the IERS (International Earth Rotation and Reference Systems Service), the Commission A3 ”Fundamental Standards” of the International Astronomical Union (IAU) and the Technical Committee 211 of the International Organization for Standardization (ISO/TC 211).This contribution presents the structure and role of the BPS. It highlights some of the recent activities, which are focused on the updating the BPS inventory of standards and conventions used for the generation of IAG products, the revision of the IERS Conventions, mainly related to Chapter 1 ”General definitions and numerical standards” as well as the description and promotion of geodetic products published at the GGOS website (www.ggos.org). The BPS also contributes to the generation of GGOS outreach material, such as videos, brochures, social media posts, etc. to make other disciplines and society aware of geodesy and its beneficial products. Finally, planned activities of the BPS according to the new GGOS Strategic Plan 2024-2034 are provided.
EnVision Gravity investigation
Authors: Rosenblatt Pascal , Marty Jean-Charles , Genova Antonio , Dumoulin Caroline
Published: March 2024

The Radio Science Experiment (RSE) onboard EnVision comprises a Radio-Occulation and a Gravity experiment. The scientific objectives of the Gravity experiment onboard EnVision are a thorough determination of Venus’ gravitational anomalies at high spatial resolution, tidal potential Love number k2 and its phase lag, and pole orientation. Accurate measurements of the pole precession, which constrains the moment of inertia of the planet, and gravitational tides preserve key information on the size and state of the core, and the mean viscosity of the mantle. The gravity investigation will use the Doppler shift of the carrier of the telemetry radio-link (X-up and X/Ka-down) between the spacecraft and tracking stations on Earth (ESTRACK network). The Doppler tracking will be performed daily during at least 3.5 hours in the nominal mission that cover 6 entire Venus cycles (4 Earth’s years).The Doppler measurements will be used to precisely determine the spacecraft trajectory from which the gravity field, Love number and moment of inertia solutions are derived. We present numerical simulations that show the radio tracking data analysis for the precise orbit determination (POD) of the spacecraft including the gravity field inversion. Our results show a significant enhancement in spatial resolution (up to 140 km) in areas mainly located in the northern hemisphere. A joint analysis of this high-resolved gravity map and topography will improve the determination of the spatial variation of the crust and lithosphere properties, in turn providing a better understanding of the thermal evolution of the planet.  A significant improvement is also obtained for the Love number k2 whose expected accuracy is 0.003. Our analysis shows tidal phase lag and moment of inertia accuracies of 0.3° and 1.5%, respectively. The combination of these geophysical measurements is well-suited to enable tighter constraints on the state and size of the core and the mantle viscosity.Further numerical simulations are carried out to detect the time-variable gravity signature expected from the atmosphere (thermal tides), especially through the estimation of the load Love number. This additional parameter also depends on the internal structure of the planet, leading to complementary information on the core state. We have also taken into account more realistic perturbations of the forces that drive the spacecraft motion, like the drag undergone by the spacecraft at low-altitude part of the orbit, and realistic perturbations of the a priori knowledge of the gravity field itself. These simulations are performed using the GINS software developed by the space French agency CNES.
Large and problematic gradients in temperature and VPD in field research settings
Authors: Novick Kim , Barnes Mallory , Gentine Pierre
Published: March 2024

Temperature and vapor pressure deficit (VPD) are fundamental drivers of plant ecophysiological function, and developing conceptual and predictive frameworks describing how photosynthesis, stomatal conductance, and transpiration respond to (and modify) these drivers is an long-standing research challenge. At the plant- and ecosystem-scale, much of our understanding of these processes has been derived by linking whole plant responses (e.g. from flux towers, sap flow, etc) to the temperature and VPD of the air measured some horizontal or lateral distance away from the plants themselves. However, thermodynamic processes frequently promote large gradients between canopy leaf and air temperatures, with tremendous variations across vertical and horizontal gradients. Here, we will synthesize observations from >100 flux towers to show that this difference can amount to 10 degrees C (or more), especially on hot summer days when heat impacts are most deleterious. The gradient between canopy and air temperature is not well explained by plant functional type, albedo, or climate, but are clearly related to canopy height and the dynamics of evapotranspiration. These profound differences in canopy versus air temperature translate into large (e.g. >5 kPa) differences between the VPD of the air and the vapor pressure differences experienced by leaves. Empirically derived sensitivities of stomatal conductance and photosynthesis to VPD are likely overestimated when the VPD of the air is used as a proxy for the vapor pressure difference experienced by plants. These biases can obscure our species-level understanding of how gas exchange responds to VPD and become especially problematic when observed sensitivities are compared with theoretical expectations or implemented in models that do not account for VPD gradients. We will conclude by discussing some strategies to limit these biases in field settings. 
Using radiogenic Sr isotopes to trace nutrient uplift from permafrost thaw: a field-based soil warming experiment
Authors: Roux Philippe , Schuur Edward , Opfergelt Sophie
Published: March 2024

The amplified warming at the poles have largely impacted arctic and subarctic ecosystem by accelerating permafrost degradation. The resulting topographical and hydrological consequences have induced significant shifts in vegetation development and composition with a clear trend of increased productivity since the early 1980’s. This trend, referred to as Arctic greening, causes significant feedback to climate dynamics by altering ground albedo, solar radiation, and shading, as well as the ecosystem net C balance through respiration, photosynthesis and litter degradation.Firstly, Arctic greening is characterized by increased productivity, resulting from warmer temperatures, longer growing seasons, increased precipitation, atmospheric CO2 concentrations, and access to newly thawed nutrients from deeper soil horizons. Secondly, over the past decades, a notable shift in vegetation has been occuring with an overall increase in shrub dominance accompanied by local increase in graminoid expansion in subsided and poorly drained areas. Given that changing nutrient sources for tundra vegetation has major implications for vegetation changes in the Arctic, and thereby on vegetation-climate feedback, there is a need to identify the processes controlling changes in nutrient sources and mobility for Arctic tundra vegetation upon permafrost thaw. We hypothesize the release and uplift of essential nutrients at depth to result from vegetation cycling and/or water table rise.To test this hypothesis, we compared radiogenic Sr isotopes composition of three typical tundra plants with different rooting depth subjected to an eight-year soil warming experiment at the Eight-Mile Lake study site in Alaska. We show that plants subjected to soil warming exhibit access to a different nutrient source than that of the control plants, representative of a deeper, recently thawed soil layer. This shift is observed regardless of rooting depth, indicating uplift of thawed nutrients. Therefore, to identify the dominant process governing nutrient mobility upon permafrost thaw, we used vegetation composition survey and mass balance equation to model the magnitude of nutrient transfer from vegetation cycling and water table rise.
Three-Dimensional Fault Slip Risk Analysis in a Shale Gas Development Area: A Case Study of the Luxian Shale Gas Field, Sichuan Basin, China
Authors: Yang Xuhang , Tao Wei , Lu Renqi , Zhang Weikang
Published: March 2024

The occurrence of induced moderate to strong earthquakes is generally believed to be the reactivation of pre-existing faults of a certain size due to stress disturbances caused by the industrial activities. Therefore, pre-existing faults in the crust are already subjected to the background tectonic stress field, and different orientations of faults experience different stress state. Therefore, evaluating the risk of faults slipping with different orientations under the tectonic stress field is the basis for guiding industrial construction design to reduce induced seismic risk.The Luxian County shale gas field is one of the four shale gas development areas in southern Sichuan, China. In this study, we conduct a fault slip risk analysis based on the distribution of the three-dimensional (3D) faults in Luxian County shale gas field . Luxian County is situated in the southwestern part of the Huayingshan fold belt, nestled between the steep Gufoshan anticline and the Luoguanshan anticline, with a broad and gentle Fuji syncline in between. The region exhibits extensive development of faults and fractures. Since the extensive implementation of hydraulic fracturing related to shale gas extraction in this region in 2019, there has been a noticeable increase in seismic activity.In this study, we interpret the 3D fault planes in Luxian County based on seismic reflection profiles. Based on the collection of in-situ stress and formation pressure data, we establish the background tectonic stress field in the Luxian shale gas field and calculate the critical pore pressure increment required for the slipping of 3D fault planes under the background tectonic stress field, as well as the fault slip tendency. Furthermore, we construct a 3D fully coupled poroelastic finite element model to calculate the static Coulomb stress perturbation that injection operations might cause on faults. Considering the uncertainty of stress field and fault orientations, based on the Monte Carlo method, the potential of fault reactivation is calculated. Our research  provides a mechanical basis for the seismic hazard analysis of the Luxian shale gas development area, serving as an excellent example for conducting seismic hazard analysis in shale gas development fields.