bluuebunny/crossref_metadata_2025 huggingface dataset:
Minor pulsations of Abramov glacier (Kyrgyzstan) observed with multi-sensor optical remote sensing
Authors: Mattea Enrico , Machguth Horst , Berthier Etienne , Hoelzle Martin
Published: February 2023

In situ monitoring of glacier mass balance – through a network of reference sites – is essential to improve process understanding and detect changes, as well as provide calibration and validation for local and large-scale modeling and remote sensing studies. Still, the interpretation and representativeness of measured mass balances can be affected by unsteady glacier flow dynamics, from minor pulsations to extreme surges. Such events can alter mass balance gradients and apparent trends; englacial water storage associated with glacier surges can lead to biases in high‑resolution geodetic assessments, and in situ measurements can be disrupted by surface changes during rapid ice movement. At the same time, mass balance and its perturbations can exert multiple influences on glacier dynamics, from an indirect control on surge frequency to the direct triggering of instabilities and propagating waves. So far, a very small number of glaciers worldwide has seen combined long-term observations of mass balance and unsteady ice flow, limiting understanding of their interaction.Here, we investigate the flow dynamics of the Abramov glacier (Pamir-Alay, Kyrgyzstan), whose measured mass balance series is one of the longest in Central Asia. We use multi-sensor optical remote sensing, including the recently released SPOT World Heritage archive as well as ASTER, IRS-1C/D and RapidEye data, to augment the Landsat record over the past 25 years. Through a dense series of digital elevation models and orthoimages, we quantify a front advance over 2000‑2005 at sub‑seasonal resolution. While the event was not observed in situ, negative mass balances in the preceding decades support an interpretation in terms of unstable ice dynamics. Moreover, asynchronous front advances on several neighboring glaciers reveal a high prevalence of unsteady ice flow in the region. We compare the Abramov advance to a previous surge of 1972/73, which was well documented with extensive in situ measurements but was virtually unknown outside Soviet glaciology. Both events do not fit well within the traditional surge models of hydrological or thermal switch, similar to previous observations in the Pamir-Karakoram.At present, the west branch of the Abramov glacier is undergoing a slow, regular and widespread inter‑annual speed-up. In the light of continued surface thinning and front retreat, the current evolution likely represents the build-up phase to the next episode of dynamic instability.
Towards an unsupervised generic seismic detector for hazardous mass-movements: a data-driven approach
Authors: Paitz Patrick , Chmiel Małgorzata , Husmann Lena , Volpi Michele , Kamper Francois , Walter Fabian
Published: February 2023

Hazardous mass-movements pose a great danger to the population and critical infrastructure, especially in alpine areas. Monitoring and early-warning systems can potentially save many lives and improve the resilience of mountain communities to catastrophic events. Increasing coverage of seismic networks recording hazardous mass-movements opens up new warning perspectives as long as efficient algorithms screening the seismic data streams in real-time are available.We propose to combine physical and statistical properties of seismic ground velocity recordings from geophones and seismometers as a foundation for an unsupervised workflow for mass movement detection. We evaluate the performance, consistency, and generalizability of unsupervised clustering algorithms like K-means and Bayesian Gaussian Mixture Models against supervised methods like the Random Forest classifier. Focusing on debris-flow records at the Illgraben torrent in Switzerland, we present a generic mass-movement detector with high accuracy and early-warning capability. We apply this detector to other datasets form other sites to investigate its transferability.Since our results aim to enable mass-movement monitoring and early-warning worldwide, Open Research Data principles like Findability, Accessibility, Interoperability and Reusability (FAIR) are of high importance for this project. We discuss how using the Renku (renkulab.io) platform of the Swiss Data Science Center ensures FAIR data science principles in our investigation. This is a key step towards our ultimate goal to enable seismology-based early warning of mass-movements wherever it may be required.
Investigating the relationship between drought and clay-shrinkage-induced subsidence damage at the town scale over France
Authors: Barthelemy Sophie , Bernardie Séverine , Bonan Bertrand , Grandjean Gilles , Kapsambelis Dorothée , Moncoulon David , Calvet Jean-Christophe
Published: February 2023

Clay shrink-swell consists in volume changes of clayey, smectite-rich soils as a function of their soil water content. Building foundations can be affected by soil shrinkage during droughts, entailing what is called subsidence damage. This is the second costliest peril covered by the French national natural disaster compensation scheme, the losses amounting to more than 16B€ between 1989 and 2021 (CCR, 2021). As illustrated by the 2022 drought in France, these costs are likely to increase as a result of climate change and of the related amplification of annual soil moisture cycles.In this context, we investigate the relationship between drought and subsidence damage, using the ISBA land surface model developed by the French meteorological service (Météo-France), geotechnical data from the French geological survey (BRGM) and data from a national claim database operated by the French state-owned national reinsurance company (CCR). We compute several yearly drought indices based on multi-layer soil moisture time series simulated by the ISBA model. Different configurations of the indices are considered, varying in particular the ISBA model settings, and the soil drought definition through a threshold value accounting for a given temporal frequency, for each model soil layer. We assess a large range of configurations by using the Kendall rank correlation of the indices with yearly town-scale insurance claim data from 2000 to 2018, processed using the geotechnical data. The analysis is repeated for five sets of four towns with an important damage history distributed throughout France, in contrasting climate conditions.Highest rank correlation coefficients are obtained for soil layers deeper than 60 cm, and with temporal frequency threshold values corresponding to intense droughts. Under these conditions, the indices are able to fairly represent the occurrence of damages. The relationship between drought indices and the number of claims is non-linear. This study benefits from the latest improvements in land surface modeling and is a step forwards in climate risk modeling since the indices investigated can be considered as new predictors for subsidence damage. Climate change impact studies will be conducted in a next phase.[References] CCR: Les Catastrophes naturelles en France, Bilan 1982-2021, 2021.
The impacts of climate change on eroding coastal historic landfills
Authors: Xue Shudan , Spencer Kate , Grieve Stuart
Published: February 2023

Impacts of climate change – sea level rise, more frequent storms and coastal flooding will exacerbate coastal erosion, resulting in the erosion of coastal historic landfills. These historic landfills are particularly vulnerable to such erosion as they typically have no lining or leachate management, limited information of the proportion and/or types of waste mixtures they contain and inaccurate records of their location and waste volumes. There are over 1200 coastal historic landfills in England alone, and over 10,000 such sites are at risk of release both solid waste and soluble contaminants across Europe. The contaminated matrix and solid wastes make landfills a major sink and source of microplastics and heavy metal, posing a threat to the coastal and marine environment.We investigated heavy metal and microplastic pollution on the beach and foreshore in three coastal historic eroding landfills, East Tilbury (n = 32 samples), Lynemouth (n = 33 samples), Northam Burrows Tilbury (n = 33 samples), UK. Samples were collected every 50 meters along the shoreline, with 100g of surface soil from the landfill edge, and 1kg of beach and intertidal sediment collected from each transect. The metal concertation was measured with handheld X-ray Fluorescence (XRF). Microplastics were density separated with a zinc chloride solution (1.5 g cm−3), after the samples were dried and digested with hydrogen peroxide. The extracted microplastics were recorded under stereomicroscope at 50× magnification with a digital camera, and characterized with Fourier-transformed infrared (ATR-FTIR) spectroscopy.This study is one of the first few to investigate the impacts of eroding historic landfill. Our preliminary findings suggest that eroding landfill are releasing significant amounts of microplastics and heavy metal pollution. These findings will be crucial to assess the impacts of eroding landfills, identify solutions and raise public attention to this environmental problem.
Nutrient Dynamics in Soil and Soil Water impact Arbuscular Mycorrhizal Fungi (AMF) Colonization and Abundance on Grassland Slopes in Eastern Bavaria, Germany
Authors: Holmer Anna Sophia , Lei Kaiyu , van Grinsven Sigrid , Völkel Jörg
Published: February 2023

It is widely known that natural soils under different land use provide a heterogenous environment regarding nutrient availability. This affects plants as well as microorganisms such as arbuscular mycorrhizal fungi (AMF).  It can have an impact on the abundance and amount of root colonization by AMF. These complex systems are often studied in experimental setups, while the wider scope of natural systems shaping entire landscapes so far received less attention.To unravel the impact of land use and the soil parent material (including the typical periglacial layering along slopes in the area) on nutrient availability and thus AMF root colonization and total abundance, two forest-grassland-creek catenae were selected in the low mountain region of the eastern Bavarian Forest (Germany). This landscape is characterized by the uniformity of the bedrock and its weathering product (saprolite), which decisively shapes the landscape. One of the two catenae was extensively used for feed production with 2-3 cuts per year. It received slurry twice a year as well as carbonic magnesium lime. The other catena had always been used as part of a deer browsing area with low stocking density. It has never been fertilized (apart from deer excretions) or limed and is mulched once per year. Soil profiles along both catenae were sampled and suction cups placed according to the periglacial layering, to investigate the nutrients in percolation- and interflow water coming downslope. Moreover, samples were taken for the investigation of AMF colonization and abundance according to the catena-profiles.We will present our results on the nutrient dynamics observation along the two catenae. These consist of nutrient concentrations in slope water from the suction cups as well as carbon, nitrogen and phosphorus contents along the catenae. Moreover, we will show the corresponding AMF root colonization and AMF abundance data. We expect these data to show a correlation of nutrient dynamics along the slope with AMF colonization and abundance as well as a difference between the two sites in nutrient dynamics and resulting AMF occurrence, according to the divergent land use.To summarize, we will provide a field-based observation of the impact of land use regimes and landscape-shaping geological disposition on nutrient dynamics along grassland slopes in the Bavarian Forest, which influence AMF colonization and abundance.
New CNN based tool to discriminate anthropogenic from natural low magnitude seismic events
Authors: Hourcade Céline , Bonnin Mickaël , Beucler Éric
Published: February 2023

Over the past 15 years, the deployment of dense permanent seismic networks leads to a dramatic increase in the amount of data to process. The seismic coverage and the station quality pave the way toward a comprehensive catalogue of natural seismicity. This means to i) detect the lowest magnitudes as possible and ii) to discriminate natural from anthropogenic events. To achieve this discrimination, we present a new convolutional neural network (CNN) trained from 60 s long three component spectrograms between 1 and 50 Hz. This CNN is trained using a reliable database of labelled events located in Metropolitan France between January 2020 and June 2021. The application of our trained model on the detected events in Metropolitan France between June and November 2021 gives a high discrimination accuracy of 98.18%. To demonstrate the versatility of our approach, this trained model is applied to different catalogues: from a post-seismic campaign in NW France (48 events) and from University of Utah Seismograph Stations, Utah, USA, (396 events between January and March 2016). We reach an accuracy of 100.00% and 96.72%, respectively, for the discrimination between natural and anthropogenic events. Since each discrimination comes with a level of confidence, our approach can be seen as a decision making tool for the analysts. It also allows to build reliable seismic event catalogues and to reduce the number of mislabelled events in the databases.
PANAME: a portal laboratory for city's environmental data
Authors: Douet Vincent , Bouffiès-Cloché Sophie , Dumont Joanne , Haeffelin Martial , Dupoont Jean-Charles , Kotthaus Simone , Masson Valéry , Lemonsu Aude , Gros Valerie , Cantrell Christopher , Michoud Vincent , Payan Sébastien
Published: February 2023

The urban is at the heart of many disciplinary projects covering very broad scientific areas. Acquired data or simulations are often accessible (when they are) via targeted thematic portals. However, the need for transdisciplinarity has been essential for several years to answer specific scientific questions or societal demands. For this, the crossing of human sciences data, health, air quality, land use, emissions inventories, biodiversity, etc., would allow new innovative studies in connection with the city.PANAME (PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch) developed by AERIS was designed as the first brick of a data portal that can promote the discovery, access, cross-referencing and representation of urban data from various sectors with air quality and urban heat islands as a starting point. The portal and future developments will be discussed in this presentation.
Towards a Digital Twin of the Earth: ECMWF's effort to build a Kilometre-scale Earth System Model
Authors: Vannière Benoît , Sandu Irina , Gascon Estibaliz , Forbes Richard , Polichtchouk Inna , Van Niekerk Annelize , Suetzl Birgit , Diamantakis Michail , Bechtold Peter , Balsamo Gianpaolo
Published: February 2023

This presentation gives an overview of the work undertaken at ECMWF, in the  Destination Earth initiative of the European Comission, to build the global continuous component of the Weather-induced and Geophysical Extremes Digital Twin (Extremes DT) of the Earth. The Extremes DT aims to forecast and monitor extreme weather, globally, at a range of around 5 days, with unprecedented fidelity.The Extremes DT utilizes the ECMWF Integrated Forecasting System cycle 48r1, with the Tco2559 grid, which has a horizontal resolution of 4.5 km. Our evaluation strategy is based on both 5-day forecasts of extreme weather cases and forecasts initialized daily over one summer and winter seasons. The performance of these simulations is compared to that of ECMWF’s operational deterministic 9km forecasts, using the following metrics: forecast skill as compared to the operational analysis or the observations, and ability to capture extreme weather events.The results show a clear added-value of higher resolution for near-surface fields and the predicted precipitation amounts in regions of high orography. However, some aspects of the forecasts, which were initially degraded, have required additional developments and tunings. For instance, the atmospheric circulation over the Tibetan plateau has a clear dependence on time-step and resolution, which is linked to the treatment of the mean and sub-grid orography, as well as the representation of orographic gravity waves. Additionally, temperature biases in the lower troposphere in the Tropics are likely due to the sensitivity of moist physics to the model time-step. We will present the choices made to reduce those biases. This work can offer valuable insights into strategies for evaluating and improving kilometric-scale Earth System Models. 
Processes affecting lateral carbon fluxes from drained forested peatlands
Authors: Palviainen Marjo , Könönen Mari , Peltomaa Elina , Pumpanen Jukka , Ojala Anne , Hasselquist Eliza , Laudon Hjalmar , Ostonen Ivika , Renou-Wilson Florence , Kull Ain , Veber Gert , Mosquera Virginia , Laurén Annamari
Published: February 2023

Lateral carbon (C) flux results from complex interplay of formation, transport and biodegradation of dissolved organic carbon (DOC), and is an important but rather scarcely studied component of the C balance in peatlands. Temperature and water table (WT) are the primary factors regulating peat CO2 emissions and the release of DOC. DOC dynamics in soil is complicated because the DOC storage is continuously increased by the decomposition of solid organic matter, but simultaneously decreased by biodegradation. Any upscaling of lateral C fluxes requires understanding these coinciding processes. We studied the effect of temperature and WT on CO2 emission and DOC concentration in pore water while incubating peat columns (diameter 0.2 m height 0.5 m) in laboratory conditions for eight months. Peat columns were extracted from drained forested peatlands in Finland, Estonia, Sweden and Ireland. WT was set to -0.2 m and -0.4 m distance from the column upper end. During the incubation, the temperature ranged between 18  and 34 ⁰C. DOC samples were extracted in monthly intervals from the columns using Rhizon soil water samplers. At the same time CO2 emission was measured from the headspace of the column. DOC biodegradation to CO2 and its temperature sensitivity was studied by incubating soil water samples in controlled conditions. The quality (aromaticity) of DOC was investigated with a UV-VIS spectrophotometer. The effect of temperature on DOC concentration was not straightforward unlike in the case of CO2 emission. DOC concentration increased steepest when the temperature exceeded 25  ⁰C, whereas with lower temperatures DOC was unchanged or slightly decreased. This can be due to different temperature sensitivities of DOC release and its biodegradation. Low WT resulted in high CO2 emissions and DOC concentrations. These results are important in developing ecosystem models accounting for lateral C fluxes and the effects of forest management, drainage and climate change in managed peatlands.
Halocarbon dynamics from Las Palmas to Guayaquil in winter 2021/2022 – Results of SO287-CONNECT
Authors: Quack Birgit , Booge Dennis , Hepach Helmke , Atlas Elliot , Karnatz Josefine , Rosa Alexandra , Cardoso Claudio , Ball Stephen , Potin Philippe , Röttgers Rüdiger
Published: February 2023

Short-lived bromo-, chloro- and iodocarbons from marine and anthropogenic sources contribute to the atmospheric halogen budgets and to ozone depletion in the troposphere and stratosphere. Their spatial variations are poorly known, given the sparse observations of marine and atmospheric concentrations. The distribution and air-sea fluxes of halocarbons need to be quantified in order to clarify the oceanic contributions to future tropospheric and stratospheric ozone chemistry.Here we present the first marine and atmospheric halocarbon dataset from the research cruise SO287-CONNECT (Pan-Atlantic connectivity of marine biogeochemical and ecological processes and the impact of anthropogenic pressures). The transit of RV SONNE from Las Palmas, Spain (departure: 11.12.2021) to Guayaquil, Ecuador (arrival: 11.01.2022) was conducted to decipher the coupling of biogeochemical and ecological processes and their influence on atmospheric chemistry along the transport pathway of water from the upwelling zones off Africa into the Sargasso Sea and further to the Caribbean and the equatorial Pacific. A comprehensive work program, which combined continuous underway and station work, marine and atmospheric measurements and sampling with incubation experiments was conducted.The distribution of short-lived halocarbons, e.g. bromoform (CHBr3), dibromomethane (CH2Br2), methyl iodide (CH3I), and trichloromethane (CHCl3) was highly dynamic in both ocean and atmosphere. We calculate the air-sea exchange of the compounds and relate physical and biological parameters to our observations. Among these are transport processes (e.g. long-range transport, eddies) and we show the varying composition of air and water masses and the potential sources of the compounds. For the first time, we estimate the contribution of the floating macroalgae Sargassum to halocarbon cycling around the North Atlantic gyre and in the Caribbean. The evaluation of the comprehensive data set collected during SO287-CONNECT improves our knowledge on the general role of the great Atlantic Sargassum belt and anthropogenic pollution in elemental biogeochemical cycles, as well as on trace gas exchange across the ocean-atmosphere interface.
A modeling study on the role of aerosols in modulating the lightning flash rates over two different climatological regions of India
Authors: Ghoshal Chowdhury Subhojit , Ganguly Dilip , Dey Sagnik
Published: February 2023

Over the last few decades, lightning has been one of the fatal extreme weather phenomena in the Indian subcontinent. Aerosols which act as cloud condensation nuclei (CCN) and ice nuclei (IN) can modify the cloud properties and alter the thermodynamic processes within the deep convective clouds in a way that eventually affects the lightning flash rates associated with thunderstorms. Long-term satellite observations suggest that a maximum number of lightning strikes (40-45 flashes/km2) occur during the pre-monsoon (March-May) and monsoon (June-September) seasons over the Indian subcontinent. We analyzed the lightning data available from satellite observations over two distinctly different climatological regions namely, northeast India and western India. In this study, we evaluate the performance of a numerical weather research and forecasting model (WRF) in reproducing the lighting characteristics over these two regions and further try to understand the sensitivity of simulated lightning flash rates to aerosol characteristics and aerosol-cloud interactions considered in the model.Two severe lightning episodes which occurred on 5-6 May 2013 and 16 April 2019 over northeast India and western India respectively are chosen as case studies for our model sensitivity experiments. We used Morrison, NSSL & SBM microphysics schemes to understand the capability of bulk and bin schemes in simulating these events. Our results show that SBM (bin) scheme affects lightning flash events more accurately than the other two bulk schemes. Increasing aerosol concentrations, increases the cloud droplet number concentrations, thus influences the collision-coalescence processes thereby increase lightning activity over both regions. To further understand the influence of aerosol size, we used a spectral bin microphysics method with a dry radius range of (0.7nm-12µm), which modified the cloud microphysical features. Changing the number concentration and default size of aerosols also influenced the meteorology and hence the deep convection and thunderstorms occurring over the two selected case study regions. More results with greater details will be presented.
Potential Impact of Spring Thermal Forcing Over the Tibetan Plateau on the Following Winter El Niño–Southern Oscillation
Authors: Yu Wei
Published: February 2023

Using observational analysis and numerical experiments, we identify that the dipole mode of spring surface wind speed (SWS) over the Tibetan Plateau (TP) could act as a trigger for subsequent winter El Niño–Southern Oscillation events. During the positive phase of spring SWS dipole mode (south-positive and north-negative), a self-sustaining “negative sensible heating–baroclinic structure” prevails over the western TP, which is characterized by negative surface sensible heating anomalies, anomalous low-level anticyclones, and mid–high-level cyclones. The “negative sensible heating–baroclinic structure” stimulates the surface westerly wind anomalies over the tropical western Pacific in May through two pathways, favoring the occurrence of subsequent El Niño events. One is through weakening the zonal monsoon circulation over the tropical Indian Ocean and the Walker circulation over the tropical western Pacific. The other is modulating the air–sea interaction over the North Pacific through triggering Rossby waves. The negative SWS dipole mode tends to induce La Niña events.
Paleoenvironmental evolution of an alkaline fluviogenic peatland (fen) from northern France: a 14 kyr bottom valley history between climatic and anthropogenic forcing
Authors: Garcia Chloé , Brasseur Boris , Mathieu Lou-Anne , Gauthier Agnès , Antoine Pierre
Published: February 2023

Fens are common in Northwest Europe in chalky bedrock valleys (from France to Poland). The peat from the valley bottoms of the River Somme basin is a remarkable wetland characterized by a significant organic accumulation (4 to 6 m on average). This alkaline peat sequence provides outstanding archives to describe the environmental evolution of Northwestern France over the last 14,000 years. Fens are also fragile environments forming huge carbon sinks. In the current context of rapid climate change, it is important to better understand and protect this carbon accumulating ecosystem. In this context, a research initiative has been initiated to highlight the respective roles of climatic and anthropogenic forcing factors (drainage, slope soil erosion) on peat formation and degradation processes and the modification of the related fluvial environments. The study focuses on a high-resolution stratigraphic transect of the valley in Morcourt (about 600 m wide) based on more than fifty manual boreholes and mechanical corings. The reconstruction of sedimentation dynamics and palaeoenvironments evolution is based on a multiproxy approach combining sedimentology, geochemistry, palynology, and plant macro-remains identification, supplemented by thirty-five 14C dates. This work reveals that the first peat deposits were restricted to channel filling at the beginning of Lateglacial (14.6 - 14.0 ka cal. BP). This peaty event was then interrupted during the Younger Dryas by the deposition of highly calcareous overbank silts (CaCO3 > 40%) in the whole alluvial plain. Typical peat formation with high TOC values (> 45%) then growth from the beginning of the Preboreal period around 12 ka cal. BP to the Atlantic (6.5 ka cal. BP) and rapidly extended to the entire valley bottom (0.07 cm/year). During the Subboreal, the reactivation of the river flow (climate modification and soil erosion) is then indicated by the development of a deep meandering channel progressively filled in with laminated silty-organic deposits and a slower peat accumulation rate in the alluvial plain (0.03 cm/year) due to lowering of the water table. These modifications are contemporaneous with the generalized opening of the landscape (palynology), associated with the acceleration of anthropic erosion processes on the slopes. Since the Subatlantic (2.9 ka cal. BP) peat deposits have higher mineral component originating from flood and slope erosion (carbonated: 65% of CaCO3; silicated: up to 27% in silty-peat). Since the late Middle Ages, organic silts fed by the erosion of loessic soils have rapidly buried the peat system which, combined with drainage, is now essentially inactive and fossilized.
Importance of water and water producing processes in cascading events in mountainous regions
Authors: Munch Jessica , Bartelt Perry
Published: February 2023

Over the last years, several multiphase avalanches have been observed, some of them leading to a cascade of events, such as in Chamoli, India, 2021, where a mixture of ice and rock fell down Ronti Peak, and transitioned to a debris flow with large amounts of water being involved. Another example is the event that occurred at Pizzo Cengalo, Switzerland, in 2017, where the rock face collapsed on the underlying glacier, entraining part of it, and also transitioning to a debris flow. When such a mass movement occurs, and leads to a cascade of events, the runout distances are much longer, and the consequences, both for humans and infrastructure, are much more important. When a multiphase avalanche turns into a cascade of events, the amount of water present in the flow seems to be a determining factor for the runout distance. The sources of water, for both of the events aforementioned remain debated, and the amounts of water that can be generated by the melting of the ice in the flow or by entrainment are poorly constrained. Indeed, from the moment that ice and snow are involved in a multi-material gravitational flow, they have the potential to melt due to friction between the different components of the flow and with the ground, and hence generate water. Material entrainment on the way also has the potential to either directly incorporate water in the flow, or bring in material with a high water content (i.e. hydrated sediments) or ice, that has the ability to melt while the flow propagates. An accurate modelling the thermal aspect of the flow as well as its ability to entrain material on the way is necessary to quantify the amount of water present in the flow.Here, using a multiphase depth-average model specifically designed to handle gravitational flows made of rocks/ice/water/snow or any single components of these, we want to assess 1) the impact of heat transfers between the materials and 2) entrainment of multiphase ground material on the flow behaviour and more specifically on the water content in the flow and the consequences it has in term of runout distances and potential for cascading events. First results show that both entrainment and heat transfer within the flow play a major role in water production. Our experiments suggest that heat transfer between rocks and ice leads to the most efficient water production. Material entrainment also plays a major role in incorporating water in the flow, or producing it by melting entrained ice. Better constrains regarding material thermal properties, ground composition and potential for entrainment are however necessary to accurately quantify the amounts of water that can join the flow and influence the runout distances.
Effect of shallow heterogeneities on wavefield gradients measurements
Authors: Bracale Mirko , Brossier Romain , Pedersen Helle , Campillo Michel
Published: February 2023

In recent years, the use of rotational sensors and DAS has become a topic of increasing interest within the seismological community because of their increasing sensitivity and affordability. We analyze the sensitivity of wavefield gradients, in the form of normal strain and rotation, to localized shallow velocity changes in a homogeneous medium.We performed several numerical simulations, using a suitably modified 3D-SEM code, to observe, in addition to wavefield itself, the normal strain and rotation as a direct output.We analyzed two case studies in which a velocity anomaly is placed in a homogeneous medium. In the first case the velocity change between the anomaly and the surrounding medium is 10%, in the second case 70%. We analyzed the sensitivity of these new observables in terms of phase shift and amplitude change.We observe a very local effect of the wavefield gradients, which show larger amplitude near the boundary between the medium and the anomaly, while away from it they behave like the displacement wavefield itself.
Subglacial discharge as a driver of fjord circulation in Ilulissat Icefjord
Authors: Kajanto Karita , de Fleurian Basile , Seroussi Helene , Straneo Fiammetta , Nisancioglu Kerim
Published: February 2023

The ice-ocean interface of Greenlandic outlet glaciers is the main source of uncertainty in the sea level contribution estimates from the Greenland ice sheet in the coming century. Subglacial discharge of surface meltwater is a currently understudied process that connects atmospheric forcing to the marine terminus. At the terminus, subglacial discharge drives buoyant plumes that enhance melt of the glacier. Surface meltwater from the ice sheet is often assumed to be directly and instantaneously transported to the gounding line as subglacial discharge. However, the subglacial drainage network evolves as a response to changes in surface meltwater volume, thus moderating and distributing the discharge along the grounding line. The early-season and late-season networks are likely to have different transport properties, leading to different properties of the buoyant subglacial discharge plume, and the accompanying melt rate.We model the subglacial hydrologic network of Sermeq Kujalleq (Jakobshavn Isbræ) glacier in West Greenland with GlaDS in ISSM. We characterize the evolution of subglacial discharge into the fjord throughout the runoff season, and compare different runoff years. Furthermore, we use the MITgcm ocean model of Ilulissat Icefjord to characterize the impact of seasonality of the subglacial discharge to fjord properties, circulation and submarine melt of the glacier front.
Retrieval of aerosol optical depth using FY-3D MERSI-II data over land
Authors: Wang Qingxin , Li Siwei
Published: February 2023

Fengyun 3 (FY-3) series of satellites is the second generation of Chinese polar-orbit, sun-synchronous meteorological satellites. As the fourth satellite in the series, FY-3D carries 10 sets of remote-sensing instruments to observe the earth's atmosphere, biosphere, hydrosphere, and cryosphere. The Medium Resolution Spectral Imager-II (MERSI-II) onboard the FY-3D satellite is equipped with aerosol-associated bands similar to MODIS which has great capability in detecting aerosols. However, there is still a lack of a stable and reliable aerosol retrieval method for the operational inversion of aerosols from MERSI-II images. This study focuses on developing a high-precision algorithm to retrieve aerosol optical depth (AOD) over entire land areas (except snow/ice and inland waters) based on MERSI-II observations. A new cost function was constructed to improve the retrieval efficiency based on the spectral dependence of AOD and the slow spatial variation of aerosol types. To extend the application adaption of the FY-3D MERSI-II AOD retrieval and avoid the errors caused by the surface Lambertian hypothesis, a monthly bidirectional reflectance distribution function (BRDF) database is built using Moderate Resolution Imaging Spectroradiometer (MODIS) products. Eight candidate aerosol optical models in different natural zones of China are constructed based on long time series of AERONET aerosol products. The new method is applied to MERSI-II images over China and validated with ground-based measurements from 14 stations in 2021. MODIS aerosol products from dark target (DT), deep blue (DB), and Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithms are also used for comparison purposes. The results show that MERSI-II AOD retrievals agree well with the ground-based measurements with correlation coefficient (R) and root mean square error (RMSE) of 0.911 and 0.128, respectively. In addition, 70.91% of AOD matchups fall within the expected error envelopes (± (0.05+20%)). MERSI-II AOD also shows higher stability in terms of spatial and temporal and better performance under heavy aerosol loading conditions than MODIS products. A good agreement in AOD distribution is also shown between MERSI-II and MODIS products with R of 0.756 to 0.868.
A depth-resolved snapshot of microplastic abundances in riffle heads in a gravelbed river
Authors: Utecht Steve , Schuetz Tobias
Published: February 2023

To date, we know little about depth-resolved distributional patterns of microplastic particles (<630 µm) of streambed sediments. Reports in literature about the abundance of considerable amounts of microplastic particles in fluvial sediments indicate that the transport follows naturally occurring flow vectors into streambed sediments. We hypothesize, that locally occurring hydraulic conditions at the water-sediment interface which are characteristic for various naturally occurring riverbed morphological structures might influence the evolution of microplastic depth profiles.As a first step of identifying morphologic feature specific microplastic depth profiles, we have carried out a series of six freeze core sampling campaigns at the centre of the longitudinal axis of two riffles located in a fourth order gravelbed river (Ruwer) contributing to the Moselle River in Trier, West Germany. The setup allows for sampling a 50 cm long undisturbed sediment freeze-core. Using dry ice as coolant and a diamond saw blade we obtained ten undisturbed sediment cube samples (125 ccm) cut from the vertical axis up to 50 cm depth from each freeze-core. Over the range from 5000 – 25 μm five size fractions were analysed with regard to mineralic sediment and microplastic particle distribution. In all sediment cube samples microplastic particles and fibres could be detected without showing distinct distributional patterns related to its depth. Although the samples represent only a small surface area (25 sq. cm), we could qualify and quantify 81 microplastic items plus 606 suspected items mainly composed of transparent fibres using Raman microspectroscopy. Furthermore, we observe an exponentially increase in microplastic abundance with decreasing size fraction by three orders of magnitude. Dominant plastic types are polypropylene, polyethylene, nitrile and polyether terephthalate representing 85% of our findings. Our first results imply that in riffle heads downward directed transport within the sediment layer affects rather the shape and size of the plastic than the absolute abundance. As a next step, typical depth patterns of microplastic at the upstream and downstream end of streambed riffles have to be identified.
Heavy metal contamination in surface and groundwater and its human health risk assessment in the Upper Yamuna River Basin, India
Authors: Rajan Shijin , Raju N. Janardhana
Published: February 2023

Heavy metal pollution in the riverine system is a major concern as it is a primary source of fresh water and has the potential to cause minuet to severe health impacts in humans. Excess heavy metal contamination in the riverine system may introduce potentially toxic elements into the aquifers via recharge or vice versa. The present study is aimed to understand the heavy metal pollution and the human health risk assessment of surface and groundwater in the Upper Yamuna River Basin (UYRB) and its spatial distribution.  For the study, twenty-eight river water and forty-eight groundwater samples were collected in May 2022 and analyzed for 15 heavy metals. Except for a few metals in groundwater (As, Fe, Mn, and Al) and surface water (As, Al, Mn), the rest were in compliance with the BIS and WHO acceptable limits. The mean metal concentration in groundwater were observed in the order of Cd < Cu < Cr < Ni < Co < Mo < Li < As < Al < Ba < B < Mn < Sr < Zn < Fe, whereas in surface water it followed the order of Cd < Cu < Cr < Ni < Co < Mo < Zn < Li < As < Ba < Al < Mn < Fe < B < Sr. The non-carcinogenic (HI) value for groundwater in adults ranged between 0.3 – 15.4 with an average of 3.95, while it ranged between 0.3 – 7.4 with an average of 2.4 for river water.  Similarly, the average incremental lifetime cancer risk (ILCR) value for adults in groundwater is 1.4 × 10-3 and 9 × 10-4 for river water. The health risk implication in children were found to be higher than the adults. The higher HI and ILCR values may be associated with the high arsenic concentration compared to their standard acceptable limit. Even though the HI and ILCR values exceeded the standard values, the heavy metal pollution (HPI) index values for all the samples were below the permissible limit. It may be due to the lower concentration or the absence of major concerned metals (Cd, Cu, Cr, Ni, etc.). Heavy metals are varyingly distributed in the basin, whereas, the lower catchment, which is the major urban center of the country is found to have comparatively higher concentrations of heavy metals and related health risks.Keywords: Heavy metal, Yamuna river, Human health assessment, Pollution index
Velocity distribution functions and non‐Maxwellianity of magnetosheath jets using MMS
Authors: Raptis Savvas , Karlsson Tomas , Vaivads Andris , Lindberg Martin , Trollvik Henriette
Published: February 2023

The interaction between the solar wind and Earth’s magnetic field results in the formation of a supercritical bow shock. Downstream of this shock wave, the magnetosheath region emerges, in which high-speed plasma flows can be formed.  These jets have been connected to several shock and foreshock properties. Moreover, due to their unique properties (i.e., higher density and velocity compared to the ambient flow), they can cause a variety of different phenomena, including magnetopause reconnection, excitation of ULF waves and electron acceleration.In this work, we use Magnetosphere Multiscale (MMS) mission to demonstrate jets’ complex structure by investigating their velocity distribution functions. Specifically, we focus on how their VDFs change over time and on whether they exhibit non-Maxwellian properties. By comparing with the VDFs taken from the background magnetosheath, we show that full particle plasma moments provide an inadequate description of jet plasma properties. Furthermore, we present different metrics to quantify the non-Maxwellian features exhibited by jet observations. Finally, we discuss how the observed kinetic properties of jets may provide insight into jets generation, wave excitation and evolution.
Aerosol composition at EMEP remote sites in France : mass balance and de-weathered trends of PM2.5 and its main components
Authors: Font Anna , Bourin Aude , Gouillou Corentin , Debevec Cécile , Bonnaire Nicolas , Sauvage Stéphane , F. de Brito Joel , Riffault Véronique
Published: February 2023

Atmospheric particulate matter with an aerodynamic diameter < 2.5 µm (PM2.5) is associated with adverse effects on the climate system, the human health, vegetation and the ecosystems. The World Health Organization (WHO) lowered the guideline limit for PM2.5 in autumn 2021 and this is exceeded in many regions including rural and remote areas in mainland Europe. Measurements of the chemical composition of PM2.5 is essential to assess the sources which contribute to PM2.5 mass concentrations and to further design meaningful policies to tackle sources at their origin.Here we report 6 years (2014- 2020) of PM2.5 mass and chemical speciation at five remote sites across France belonging to the EMEP network (European Monitoring and Evaluation Programme). The seasonal and spatial variability of aerosol composition and source contributions based on the proximity of sources and long-range transport are discussed. Trends in PM2.5 and the main components at the five locations were evaluated by means of random-forest modelling coupled with a de-weathering algorithm. This approach is advantageous as resulting trends are driven by changes in emission or atmospheric processes and not by changes in weather conditions and/or long-range transport patterns. Random-forest regression modelling was built using meteorological data, backtrajectory information and temporal variables at each site and quantified the most important factors that explain PM2.5 concentrations at remote rural areas in France.All sites observed statistically significant downward trends in PM2.5 at a rate of -4 to -9% year-1 for the period 2014 – 2020. The decrease in PM2.5 concentrations was mostly explained by changes in the secondary inorganic species (sulphate, nitrate and ammonium) and not by changes in primary PM2.5 emissions. The variability in trends in PM2.5 and components observed across the sites is discussed with their implications for policy makers.
Definitions and implications of climate-neutral aviation
Authors: Brazzola Nicoletta , Patt Anthony , Wohland Jan
Published: February 2023

To meet ambitious climate targets, the aviation sector needs to neutralize CO2 emissions and reduce non-CO2 climatic effects. Despite being responsible for approximately two-thirds of aviation’s impacts on the climate, most aviation non-CO2 species are currently excluded from climate mitigation efforts. Here we identify three plausible definitions of climate-neutral aviation that include non-CO2 forcing and assess their implications considering future demand uncertainty, technological innovation, and CO2 removal. We use empirical relationships to translate aviation emissions to climate forcing and a reduced-complexity climate model to assess the impacts of these climate neutrality frameworks, including the needed CO2 removal, on global temperature in the context of the different demand and technology scenarios. We demonstrate that simply neutralizing aviation’s CO2 emissions, if nothing is done to reduce non-CO2 forcing, causes up to 0.4 °C additional warming, thus compromising the 1.5 °C target. We further show that substantial rates of CO2 removal are needed to achieve climate-neutral aviation in scenarios with little mitigation, yet cleaner-flying technologies can drastically reduce them. Our work provides policymakers with consistent definitions of climate-neutral aviation and highlights the beneficial side effects of moving to aircraft types and fuels with lower indirect climate effects.
Morphometric Study of The Ediacaran Tubular Fossils Sinotubulites
Authors: Dai Qiaokun , Hua Hong , Luo Jinzhou
Published: February 2023

Sinotubulites is a kind of late Neoproterozoic straight or slightly curved cylindrical tubular fossils with multiple sets of wall structure and both ends open. It has now been found worldwide, and regarded as one of the representatives of the tubular animal radiation before the Cambrian explosion. In this paper, morphological data about Sinotubulites in the Ediacaran Gaojiashan Biota at the Lijiagou section of Ningqiang, Shaanxi province were analyzed to explore the possible relationship between the characteristics of each part of Sinotubulites in ontogenetic process. A total of 378 well preserved fossil samples were selected for measurement, among which 150 apertural and 134 side view samples were examined under scanning electron microscopy (SEM), and 94 samples were examined under micro-scope, of them, the latter was only used as supplementary data for more accuracy analysis. Through the data processing, it was found that a positive linear relationship exists between the maximum diameter and the diameter of the inner circle (Linear regression R2=0.7), and the linear relationship between the maximum diameter (both five radiant and six radiant tubes) and unilateral length is the most robust (Linear regression, R2=0.8903) in Sinotubulites tubes. In general, there is no significant correlation between the tube length and the wall thickness, either bet ween the tube length and the maximum diameter. The results showed that Sinotubulites may simply discarded its old tube, and secreted a new one to construct a home at different stages of the growth. At the same time, under turbulent hydrodynamic conditions, Sinotubulites, may rely on the variable longitudinal ridges to stabilize the tubes, instead of the secretion of thicker shell walls.