bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of crustal fluids and thermo-mechanical structure for lower crustal seismicity: the Gargano Promontory (southern Italy)
Authors: Tallarico Andrea , Lavecchia Alessio , Filippucci Marilena , Selvaggi Giulio , Cecere Gianpaolo , Cloetingh Sierd
Published: February 2023

Several regions around the globe are characterized by a seismically active lower crust, at depths where lithological, thermal and rheological conditions suggest stress release by ductile flow. The Gargano Promontory (GP, southern Italy) is an example where a recently installed seismic network has recorded an intense seismic activity at depths between 20 and 30 km, i.e. in the lower crust. We analyze a possible mechanism controlling the distribution of seismicity in the GP to identify the factors that make the lower crust seismically active. To this aim, we construct a thermo-rheological model of a layered continental crust, calibrated on the basis of geometrical, lithological and thermal constraints. The model takes into account a multiphase crustal lithology, the presence of fluids in the crystalline basement, lateral variations of geotherm and stress field.The numerical simulations show that the presence of fluids is a key factor controlling the cluster of seismicity in the lower crust. Moreover, the presence of water in the upper crystalline basement and sedimentary cover provides a plausible explanation for upper crustal seismicity in a zone of very high heat flow SW of the GP. The distribution of the seismicity is probably affected by the composition of the crystalline basement, with mafic bodies injected into the crust during the Paleocene magmatic phase that affected the Mediterranean region. Our findings suggest that the presence of hydrous diapiric upwelling(s) in the upper mantle can feed a deep fluid circulation system, inducing lower crustal seismicity.
Hydrogen migration through natural rocks – an experimental approach
Authors: Strauch Bettina , Pilz Peter , Zimmer Martin , Hierold Johannes
Published: February 2023

The investigation of hydrogen storage options in geological formations is an important part towards the development of technologies for the use of renewable energy. Promising storage capacities are expected in either rock salt deposits or porous sandstone formations with a gas-tight mudstone as cap rock. To obtain crucial data on hydrogen diffusion rates in these rocks, experimental studies are necessary as a first approach.Here we present an experimental set up comprising two gas chambers, separated by the rock sample under investigation, where the driving force for gas migration through the rock sample is solely the chemical potential (concentration gradient). The hydrogen migration behaviour in samples of dry and wet sandstone, rock salt and mudstone was qualified by hydrogen break-through times and diffusion coefficients. Differences between the rock samples can be clearly seen. Also, the effect that wetted or water-saturated samples have higher retention due to closed pores and microcracks. The break through times varied from half an hour for dry sandstone to 918 hours for wetted rock salt. Based on concentration changes on the permeate side, hydrogen diffusion coefficients were derived in the range from 10-9 to 10-7 m²/s. The experimental set up proves to be suitable for determining diffusion parameters in natural rocks.
Distinction between watersheds prone to debris flow, debris flood, and flood using morphometry in Serra do Mar, Brazil (São Paulo State North shore).
Authors: Dias Vivian Cristina , Dias Helen Cristina , Grohmann Carlos Henrique
Published: February 2023

Among the hydrogeomorphologic processes, debris flows, debris floods, and floods stand out as the most destructive due to their potential to transport a variety of materials over long distances and the damage caused to urban infrastructures. The watershed dynamic and morphometry stand out as one of the paramount factors related to triggering the processes. The Serra do Mar, on the southeast coast of Brazil, is a mountain range with about 1,500 km where landslides are frequent, causing a high number of casualties and economic losses, especially when related to debris flows/floods.  Thus, studies focusing on the evaluation of the susceptibility of the areas are needed, aiming for mitigation and planning actions. In this way, the aim of this research was the characterization of watersheds for the occurrence of hydrogeomorphologic processes using morphometry on the North shore of Serra do Mar in São Paulo State. To reach this goal, the following methodological steps were carried out: (a) delimitation of the watersheds considering the proximity of the scarp of the Serra do Mar, altimetric range, angle, confinement of the channel, and evidence of past events; b) mapping of morphometrics parameters (Area, Length, Basin relief, Relief ratio, and Melton ratio) using a TanDEM-X Digital Elevation Model with 12 meters spatial resolution; and c) identification of watersheds prone to debris flows, debris floods, and floods according to the morphometry results. A total of 355 watersheds were mapped in three cities (Ubatuba, Caraguatatuba, and São Sebastião). The results show that according to the Melton ratio, 67% of the watersheds are prone to debris flows, with values > 0,60, followed by 30% prone to debris floods and floods, and only 3% prone to fluvial processes. Values vary from 0,16 to 1,70, with a mean of 0,68. Values for Area were between 0,07 to 8,02 km² (mean 0,70 km²), in the range for areas prone to debris flows, according to the literature (up to 10 km²). For the Length, the values vary from 0,47 to 6,73 (mean 1,30 km), with most of the watersheds (94%) with values up to 2,7 km (the threshold indicated for debris flow prone areas). Basin relief and Relief ratio presented values varying between 0,26 to 1,27 km (mean 0,57 km), and 0,09 to 0,79 (mean 0,44), respectively. The next step of the research is the investigation of past events using aerial photos and satellite images. The results of this research can contribute to government response and the reduction of the damage caused by natural hazards in Brazil.  
Radiation, Clouds, and Self-Aggregation in RCEMIP Simulations
Authors: Holloway Chris , Pope Kieran , Stein Thorwald , Jones Todd
Published: February 2023

The responses of tropical anvil cloud and low-level cloud to a warming climate are among the largest sources of uncertainty in our estimates of climate sensitivity. However, most research on cloud feedbacks relies on either global climate models with parameterized convection, which do not explicitly represent small-scale convective processes, or small-domain models, which cannot directly simulate large-scale circulations. We investigate how self-aggregation, the spontaneous clumping of convection in idealized numerical models, depends on cloud-radiative interactions with different cloud types, sea surface temperatures (SSTs), and stages of aggregation in simulations that form part of RCEMIP (the Radiative-Convective Equilibrium Model Intercomparison Project). Analysis shows that the presence of anvil cloud, which tends to enhance aggregation when collocated with anomalously moist environments, is reduced in nearly all models when SSTs are increased, leading to a corresponding reduction in the aggregating influence of cloud-longwave interactions. We also find that cloud-longwave radiation interactions are stronger in the majority of General Circulation Models (GCMs), typically resulting in faster aggregation compared to Cloud-system Resolving Models (CRMs). GCMs that have stronger cloud-longwave interactions tend to aggregate faster, whereas the influence of circulations is the main factor affecting the aggregation rate in CRMs.
Advection in granitic rock matrix: Modeling a radionuclide tracer transport experiment at the Grimsel Test Site.
Authors: Soler Josep M. , Jurado Deby , Saaltink Maarten W. , Martínez Lurdes , Hidalgo Juan J. , Lanyon G. William , Martin Andrew J.
Published: February 2023

Within the GTS-LTD project (Grimsel Test Site – Long-Term Diffusion), a field radionuclide tracer transport experiment in unfractured granitic rock was performed. Grimsel groundwater containing several tracers (3H as HTO, 36Cl-, 22Na+, 134Cs+, 133Ba2+) was continuously circulated through a packed-off borehole and the decrease in tracer concentrations in the liquid phase was monitored for a period of 1266 days (05/03/2014 – 22/08/2017). Additionally, tracer breakthrough was monitored in an observation borehole a few cm away.Initial modeling of the experiment (1D radial) showed that the evolution of tracer concentrations seemed to depart from the expected trend after some time, with concentrations in the injection borehole decreasing faster than expected from pure diffusive transport. Additional 2D calculations (section normal to the boreholes) were performed to check the possible effect of advection through the rock matrix. Advection could explain the evolution of concentrations in the injection borehole, but could not fully explain the measurements in the observation borehole.Rock samples around the experimental section were collected right after the end of the experiment, allowing the measurement of tracer distributions in the rock. The observed patterns for the non-sorbing tracers (HTO, 36Cl-) showed clear preferential transport directions, consistent with advective flow towards the gallery from which the boreholes were drilled. Final 3D modeling of the experiment can explain the measured concentrations in the boreholes and in the rock. Tracer transport is affected by both diffusion and advection through the granitic rock matrix. Also, in situ accessible porosities (about 0.0014) are smaller than those measured in rock samples (about 0.009), pointing to the destressing of the rock samples after drilling.
Wave Breaking Statistics Under Wind in Sea and Laboratory Conditions
Authors: Liberzon Dan , Knobler Sagi , Winiarska Ewelina , Babanin Alexander
Published: February 2023

The hydrodynamical process of breaking water waves is still a source of many unsolved questions. An extensive research work has been carried out during the last decades in order to quantify and define the associated energy redistribution, which directly influences a wide range of climate processes, maritime applications, and oceanic phenomena.Naturally, waves become steeper toward the inception of breaking; however, there is still a lack of unanimity regarding the relationship between breaking probability statistics and wave steepness. Here we present a detailed analysis of different sea states from the Black Sea measurements and from a closed wind-wave flume experiments. Together with the wind-derived parameters, the water wave statistics were gathered using an innovative breaking wave detection algorithm. The algorithm was recently developed to allow accurate detection of breaking waves based on the phase-time approach and wavelet analysis to identify breaking-associated patterns in the instantaneous frequency variations of surface elevation fluctuations. The in-depth analysis of breaking and non-breaking wave statistics included wave-by-wave calculations resulting in steepness and celerities of the local wave, derived from the local wave frequency and wavenumber. Finally, the findings, after investigation and validation, presented a skewed Gaussian-like steepness histogram, revealing that both non-breaking and breaking waves can reach steep profiles, above the Stokes limit. 
High-resolution water and stable isotope dynamics in drought-stressed urban vegetation
Authors: Ring Ann-Marie , Tetzlaff Dörthe , Dubbert Maren , Soulsby Chris
Published: February 2023

Urban green spaces are highly valuable in supporting the climate and infrastructure of cities through rainwater retention, evaporative cooling and shading. Investigating the diurnal and seasonal ecohydrological process dynamics in the urban soil-plant-atmosphere continuum is crucial to understand what types of landcover might best balance water re-distribution for a particular urban landscape providing cooling effects whilst not compromising groundwater recharge.Stable water isotopes are very useful tools to investigate these complex interactions between soil properties, plant physiology and atmospheric drivers. In 2022, we conducted an experimental study looking at the complex patterns of the urban soil-plant-atmosphere interface at high temporal resolution at an urban tree stand and a grassland in Berlin, Germany during an entire growing season. To assess atmospheric moisture demand and vegetation water dynamics, we performed novel in-situ and real-time sequential measurements in the field at different heights in tree xylem and in the atmosphere. This was complemented by destructive sampling of soil water isotopes from multiple depths and eddy flux measurements at an open field near the sites.We could identify clear evaporative and drought signals in the different water cycle components, including the extensive summer drought across continental Europe in July and August 2022. Results showed faster and larger responses to precipitation inputs in the upper soil moisture signal at the grassland. Atmospheric fluxes indicated clear evaporative losses just above the grass (15 cm height). Underneath tree canopies, upper soils responded more slowly to precipitation inputs and the atmospheric profile showed more homogenous spatio-temporal distribution of water vapour signals. Xylem water dynamics revealed contrasting diurnal and seasonal variations in different tree species and tree heights. Plant water sources were mostly drawn from deeper soil (70 cm) horizons. During the extended period of water scarcity in August, drought signals came from enriched atmospheric water vapour and low sap flux.This knowledge of the water dynamics under different drought-stressed urban vegetation is extremely useful for the development of isotope aided ecohydrological models and allows science-based evidence for sustainable urban planning tackling climate change and urban densification.
MJO-induced land-atmosphere feedbacks across East Africa
Authors: Talib Joshua , Taylor Christopher , Harris Bethan , Wainwright Caroline
Published: February 2023

Across East Africa, sub-seasonal rainfall variability predominantly depends on the phase of the Madden Julian Oscillation (MJO). Rainfall is enhanced during MJO phases 2 to 4, and suppressed during phases 6 to 8. Given that MJO-induced anomalous precipitation can persist beyond several days, a surface response is expected. Using earth observations and reanalysis data, in this presentation we will show how MJO-induced precipitation anomalies promote a surface response which feeds back onto local and regional atmospheric conditions.              MJO-induced rainfall suppression across East Africa decreases surface soil moisture across the exit region of the Turkana jet. Reduced soil moisture increases surface sensible heat fluxes and elevates land surface temperatures. The drier and warmer surface reduces surface pressure and leads to an intensification of the Turkana jet. We conclude that on average approximately 11% of the anomalous jet speed is associated with surface-driven pressure fluctuations over the course of a single day. Since the Turkana jet controls moisture transport from low-lying regions of East Africa into Central Africa, we highlight that surface-induced jet variations impact rainfall totals across East Africa. Furthermore, due to the Turkana jet response to spatial variations in surface warming, we also identify that the magnitude of MJO-induced anomalous precipitation is influenced by surface conditions prior an MJO event. For example, when the surface over southern South Sudan is anomalously dry, MJO-induced precipitation suppression is greater. This presentation will highlight that to fully exploit predictability from the MJO, forecast models must correctly represent surface processes and land-atmosphere interactions. Future work evaluating sub-seasonal forecast models and improving the representation of land-atmosphere interactions will enhance the lead-time of early warning systems across East Africa.
Imprints of large-scale oscillations on river flow in selected Canadian river catchments
Authors: Olusola Adeyemi , Ogunjo Samuel , Olusegun Christiana
Published: February 2023

Rivers within sub-tropical and temperate regions serve several purposes, including agricultural irrigation, hydro-power generation, and drivers of civilization. The impacts of six large-scale oscillation indices on river flow at three stations within Humber catchments (Ontario and Labrador) between 1970 and 2020 were investigated using sensitivity and wavelet analyses. Results showed that the discharge at East Humber River near Pine has the highest statistically significant sensitivity of 0.304 and 0.394 units per month to the Dipole Mode Index (DMI) and Tropical North Atlantic (TNA), respectively. Monthly significance analysis also showed the varied influence of large-scale oscillations on the river flow at these locations. Wavelet analysis reveals significant active multidecadal oscillations for the North Atlantic Oscillation (NAO) at East Humber River near Pine with high spectral power. This study has identified the contributions of different climatic indices to river flow within the Humber catchments. The results will be helpful in environmental planning and effective water management within the basin.
Reaction-assisted fracture propagation: An application to carbon storage
Authors: Pena Clavijo Santiago , Addassi Mouadh , Finkbeiner Thomas , Hoteit Hussein
Published: February 2023

Understanding fracture propagation in chemically active rock formations is of interest to several engineering and science disciplines. Fracture nucleation and growth governed by in-situ chemo-poro-mechanical processes is crucial, for instance, during the transformation of CO2 into solid carbonate rock. The process consists of injecting a non-resident mixed fluid phase of CO2 in water which dissolves parts of the fracture-porous medium system and precipitates secondary minerals, altering the solid’s porosity and permeability. Hence, dissolution/precipitation processes and concomitant solid weakening alter physico-chemical properties in the system, which in the presence of pore pressure changes, may facilitate and enhance fracture nucleation and growth. More importantly, the evolution of fracture networks in the rock determines fluid flow, which is crucial for progressing chemical processes such as ionic advection and diffusion. This study focuses on the complex chemo-hydro-mechanical responses in naturally fractured rock formations subject to acidic carbon water injection. We use a recently developed framework to incorporate the mechanisms of reactive transport, fluid flow and transport in porous media, and fracture propagation in poroelastic media. Due to the complexity of such coupled phenomena, few numerical modeling and experimental studies have been published in this area. Existing models often oversimplify the chemical interactions by using simplistic fitting functions. Contrary to these conventional approaches, the considered framework uses PHREEQC to estimate the localized chemical interactions for a general system. A key novelty of this study is in applying the considered framework to study CO2 injection into complex naturally fractured basalt formations.
How the effect of earthworms on soil organic matter mineralization and stabilization is affected, by litter quality and stage of soil development.
Authors: Frouz Jan , Irshad Saliha
Published: February 2023

Globally soil fauna can consume about half of litter fall. Important question is how this activity affect mineralization and stabilization of soil organic matter. Here we explore how much fauna effect litter decomposition and organic matter stabilization in soils of various ages supplied by litter of various quality.   Laboratory mesocosm consist from litter and mineral layer mineral soil originated either from spruce and alder stand which were growing either on post mining soils (young soil) or from soil in close vicinity of post mining sites (mature soil), mineral soils were supplied by matching litter, mesocosms were either without fauna or supplied by two individuals of earthworm Aporectodea rosea. Results show significant effect of tree, soil age and earthworm; alder respire more than spruce, young soil respire more than old soil, and mesocosms with earthworms respire more than without earthworms.  Earthworm effect show statistically significant interaction with tree and soil age, earthworms always increase respiration in alder soil, but in spruce only in mature soil while opposite was true for young soil.  In general earthworms promote removal of litter from soil surface and its accumulation in mineral soil. Earthworms promote C storage in MAOM  namely in young spruce soil. Results indicate that in young soils which are far from saturation (spruce on post mining soil) earthworm activity promote soil C storage most likely by promoting C storage in MAOM, in the contrary in mature,  C saturated soils, earthworms rather promote soil respiration.
Quantifying the uncertainty and errors between common analytical methods for measuring airborne microplastics
Authors: Revell Laura , Aves Alex , MacDonald Anna , Allen Deonie , Allen Steve , Materic Dusan , Gaw Sally , Davy Perry , Naeher Sebastian
Published: February 2023

In recent years airborne microplastics have emerged as a ubiquitous pollutant worldwide, with negative implications for ecosystems, climate and human health. The differing sampling and analysis techniques used amongst micro- and nanoplastic research groups limits our understanding of the global distribution of airborne microplastics and nanoplastics. We present plans and progress for an ongoing coordinated inter-laboratory experiment, designed to elucidate strengths and weaknesses of individual analysis methods. Daily active pumped air samples were collected in a controlled manner at a remote site in Canterbury, New Zealand, alongside weekly deposition samples. All samples were divided evenly, using specific contamination controls, into four sample sets for interlaboratory method comparisons, and distributed to participating research groups in New Zealand, Germany and the UK. Samples will be analysed using common microplastic analysis techniques: micro-Fourier transform infrared spectroscopy (µFTIR), micro-Raman spectroscopy (µRaman), fluorescence microscopy, pyrolysis – gas chromatography/mass spectrometry (Py-GC/MS), and thermal desorption – proton transfer reaction – mass spectrometry (TD-PTR-MS). The results will allow quantification of the relative uncertainties and biases associated with each individual method, and inform how future airborne microplastics studies performed with different analytical methods should be interpreted.
A National Landslide Dam Database for New Zealand
Authors: Wolter Andrea , Morgenstern Regine , Lukovic Biljana , Cox Simon C. , Bain Dan , Sirohi Akansha , Bruce Zane , Townsend Dougal , Rosser Brenda , Jones Katie , Massey Chris
Published: February 2023

As key components of multi-hazard, cascading slope-to-river systems around the world, landslide dams can have severe consequences. They form when landslides block a watercourse and can result in catastrophic flooding if they fail rapidly. Nonetheless, they are under-researched given the potentially high consequences of sudden dam breach and failure. Their formation, longevity, and breaching behaviour are not well understood, which is important information needed for effective risk management.We present an Aotearoa New Zealand database of landslide dams, spanning pre-historic to historic natural dams compiled from several existing datasets and inventories. The database includes ~1030 landslide dams, as well as information for each dam such as catchment properties, landslide and dam dimensions, dam type, and dam stability where available. Where possible, quantitative attributes have been calculated automatically using arcpy (a Python site package that utilises ArcGIS processing tools), which allows consistency and repeatability in the database. A data quality ranking scheme has also been developed to assess the reliability of each dataset. The database will be available online on the OSF platform in mid-2023.Several case studies, including the Hapuku, Stanton, Leader, Linton, and Conway landslide dams that formed during the 2016 Mw 7.8 Kaikōura earthquake, have been analysed in detail. Multiple field and remote sensing campaigns completed since 2016 – including field mapping, RTK surveying, drone photogrammetry, and LiDAR surveys – show the evolution of the landslide deposits and dams, providing high-resolution spatiotemporal data on their formation and breaching characteristics.The database is currently being analysed to improve our understanding of dam formation potential and longevity, as well as breaching behaviour. These analyses will contribute to improved hazard management and avoidance.
Counting (on) Blue Carbon - Challenges and Ways forward for carbon accounting of ecosystem-based carbon removal in marine environments
Authors: Mengis Nadine , Paul Allanah , Fernández-Méndez Mar
Published: February 2023

The latest IPCC assessment report highlights once more the need for negative emissions via carbon dioxide removal (CDR) measures to reach ambitious mitigation goals. In particular ecosystem-based CDR measures are currently the focus of national net-zero strategies and novel carbon crediting efforts. Using ecosystem-based carbon removal measures in marine environments as an example, we here highlight key challenges concerning the monitoring and evaluation of blue carbon fluxes for carbon crediting. Challenges specific to ecosystem-based CDR measures are i) the definition of baseline natural carbon fluxes, which is necessary for ii) clear anthropogenic CDR signal attribution, as well as iii) accounting for possible natural or anthropogenic disturbances of the carbon stock and hence an assessment for the durability of the carbon storage. In addition, the marine environment poses further monitoring and evaluation challenges due to i) temporal and spatial decoupling of the carbon capturing and sequestration processes, combined with ii) signal dilution due to high ecosystem connectivity, and iii) large pre-existing carbon stocks which makes any human-made increase in carbon stocks even harder to quantify. To increase the scientific rigor behind issued carbon credits, we propose a concentration of monitoring efforts on carbon sequestration rather than capturing processes, and baseline establishment for natural carbon sequestration in diverse ecosystems. Finally, we believe that making carbon credits subject to dynamic adjustments over time, will increase their credibility.
Multiscale analysis of typhoon-induced oceanic responses: A Case Study of Typhoon Kalmaegi in the South China Sea
Authors: Li Gang , He Yijun , Yang Yang , Liu Guoqiang , Lu Xiaojie , Perrie William
Published: February 2023

A localized multiscale energetics framework is used to study the multiscale typhoon-induced upper oceanic responses, in the case of Typhoon Kalmaegi in the South China Sea. A diagnostic methodology of the time-varying energetics, on the basis of the multiscale window transform (MWT) —namely, localized multiscale energy and vorticity analysis (MS-EVA) decomposes HYCOM variable fields into a low-frequency background flow window, a mid-frequency flow window and a high-frequency process window. The background window represents mesoscale processes and Kuroshio currents well and the mid-frequency window captures near-inertial processes influenced by typhoon-induced wind stresses. The scale-scale kinetic energy transfers from the near-inertial window to the background window, mainly on the right-hand side of the typhoon track. Advection and pressure work redistribute energy contribute to the accumulation of kinetic energy in the mid-frequency flow window and enhances ocean mixing. Negative vorticity has a significant impact on the distribution and downward propagation of the near-inertial energy, leading to heterogeneity in the mixing of the upper ocean. We offer new insights into understanding the multiscale interactions between typhoons and the upper ocean.
Diverse responses of multiple crops to drought and salinity stress
Authors: Wen Wen , Timmermans Joris , Chen Qi , van Bodegom Peter M.
Published: February 2023

Food security is threatened by co-occurring stresses (e.g. salinity and drought) under global climate change. To circumvent major impacts on food production, the vulnerabilities and tolerances to these threats need to be characterized. Traditionally, the tolerance of crops is evaluated in highly controlled small-scale experiments involving only a limited number of crop types. To increase our understanding in actual agricultural tolerances, plant functioning, as observed by functional traits, need to be performed in real-life scenarios for as many crops as possible. Remote sensing is presently the only tool capable of monitoring such plant functional traits simultaneously over large areas.The aim of this research therefore is to evaluate the crop tolerances to combined drought and salinity stress across various plant functions in real-life conditions. We evaluated drought and salinity tolerance impacts on different types of crops across the entire US continent, using five traits representative of different plant functions. Given crop tolerance highly depended on the moments, we evaluated the dominant stress and the onset among individual and combined effects of drought and salinity for five traits from March to October.We found strong interaction effects between stress and time using two-way ANOVAs. In general, crops were more sensitive to combined drought and salinity, although they differ significantly between species and moments. Of the individual traits, LAI was triggered first by stresses, followed by FAPAR and FVC, and Cab and Cw were the last to respond to stresses. This implies that plants reduce primary production before reducing water content.Our study provides a way of evaluating the tolerance of diverse crops to co-occurrence stresses both separately and in combination. Through applications to other vegetation types and stresses, our approach creates a quantitative backbone to inform sustainable food production.
Swarms of Microseismicity Beneath the Submarine Kolumbo Volcano Indicate Opening of Near‐Vertical Fractures Exploited by Ascending Melts
Authors: Schmid Florian , Petersen Gesa , Hooft Emilie , Paulatto Michele , Chrapkiewicz Kajetan , Hensch Martin , Dahm Torsten
Published: February 2023

The Kolumbo submarine volcano in the southern Aegean (Greece) is associated with repeated seismic unrest since at least two decades and the causes of this unrest are poorly understood. We present a ten-month long microseismicity data set for the period 2006–2007. The majority of earthquakes cluster in a cone-shaped portion of the crust below Kolumbo. The tip of this cone coincides with a low Vp-anomaly at 2–4 km depth, which is interpreted as a crustal melt reservoir. Our data set includes several earthquake swarms, of which we analyse the four with the highest events numbers in detail. Together the swarms form a zone of fracturing elongated in the SW-NE direction, parallel to major regional faults. All four swarms show a general upward migration of hypocentres and the cracking front propagates unusually fast, compared to swarms in other volcanic areas. We conclude that the swarm seismicity is most likely triggered by a combination of pore-pressure perturbations and the re-distribution of elastic stresses. Fluid pressure perturbations are induced likely by obstructions in the melt conduits in a rheologically strong layer between 6 and 9 km depth. We conclude that the zone of fractures below Kolumbo is exploited by melts ascending from the mantle and filling the crustal melt reservoir. Together with the recurring seismic unrest, our study suggests that a future eruption is probable and monitoring of the Kolumbo volcanic system is highly advisable.
Simultaneous observations of mesospheric bore and front over the Himalaya
Authors: Mondal Subarna , Guharay Amitava , Sarkhel Sumanta , Krishna M. V. Sunil , Mlynczak Martin G.
Published: February 2023

Interesting observational evidence of interaction between a mesospheric bore and a mesospheric front is found in O(1S) 557.7 nm airglow images over the western Himalayan region on 25 April 2022. The event is unique as it is the first report of a mesospheric bore interacting with a typical mesospheric front. The vertical profiles of temperature and Brunt Vaisala frequency indicate presence of a strong mesospheric inversion layer (MIL) which acts as a stable thermal duct for the propagation of the mesospheric bore. Analysis suggests that local chemical heating plays a significant role in sustaining a strong MIL/thermal duct. The bore front shows an anti-clockwise rotation, which is attributed to the differential phase speed of different regions of the bore due to variations in duct depth. The bore propagation above is observed to push the underlying OH layer downward, resulting in a maximum horizontal slope of the peak height of the OH volume emission rate (VER) on 25 April 2022. The results highlight the bore-front interaction, mesospheric background condition for bore propagation, and its effect on the altitudinal shift of adjacent airglow emission layers.
A periodic visco-elastic model for crevasses propagation in marine ice shelves
Authors: Zarrinderakht Maryam , Zwinger Thomas , Schoof Christian
Published: February 2023

Calving is a key mechanism that controls the length of floating ice shelves, and therefore theirbuttressing effect on grounded ice. A fully process-based model for calving is currently still notavailable in a form suitable for large-scale ice sheet models. Here we build on prior work thattreats crevasse growth in the run-up to calving as an example of linear elastic fracture growth.Purely elastic behaviour is confined to short time intervals, much less than a single Maxwelltime (the ratio of viscosity to Young’s modulus) in duration: this is typically hours to a few daysfor cold polar ice shelves, depending on temperature and state of stress. We explicitly recognizethat the elastic stresses occurring during fracture propagation act on an ice-mass subject to apre-stress created by long-term viscous deformation. By coupling a boundary element solverfor instantaneous elastic stress increments and the resulting fracture propagation with theElmer/Ice Stokes flow solver that computes the pre-stress and is able to model the long-termevolution of the domain, we are able to show how viscous deformation end elastic fracturemechanics interact. We show that viscous deformation is in general an essential part of calving,and as a result, viscous deformation ultimately sets the time scale for calving. The geometricchanges resulting from that deformation are necessary to cause continued growth to calvingof fractures that initially propagate only part-way through the domain. We identify two distinctmodes of fracture propagation: either fractures propagate episodically, the crack lengthening ineach instance by a finite difference over short (elastic) time scales. Alternatively, fractures growgradually in such a way as to keep the viscous pre-stress near the crack tip from becomingtensile, with elasticity playing a secondary role. Our results point to the purely instantaneousstress-based calving laws that have become popular in large-scale ice sheet mechanics beingtoo simplistic.

Figure1: ice shelf geometry evolution and crevasse propagation

 

 
Aspect Angle of Plasma Irregularities in the Ionosphere Measured by Using the Radar Imaging of VHF Arrayed Radar
Authors: Chen Jenn-Shyong , Wang Chien-Ya , Chu Yen-Hsyang
Published: February 2023

Multireceiver and multifrequency radar imaging techniques, implemented in the 46.5 MHz MU radar in Japan (34.85°N and 136.10°E), were employed to investigate the aspect sensitivity of field-aligned plasma irregularities (FAIs) in the mid-latitude ionospheric E region. Aspect sensitivity of refractive irregularities in the atmosphere describes the radar echo intensity varying with the radar beam direction. For the FAIs in the ionosphere, the radar echoes are generally strongest at the beam direction perpendicular to the geomagnetic field line, and decay rapidly with off-perpendicular angle along the geomagnetic field line. This feature relates partly with the values of electron-neutral collision frequency (νe), electron gyrofrequency (Ωe), ion-neutral collision frequency (νi), ion gyrofrequency (Ωi), the ratio νe/Ωe, among others, and moreover, is also subjected to nonlinear coupling process of unstable waves in the plasma irregularities. In practical observation, the radar beam of the MU radar was directed to geographic north and at 51° zenith angle, which was normal to the geomagnetic field line around 100-110 km height (range: ~160-175 km along the beam direction). Five carrier frequencies and nineteen receivers were operated for radar imaging to retrieve the power distribution in the radar volume, and then the angular power distribution was used to estimate the aspect angle along the geomagnetic field line. Retrieval algorithms such as Fourier, Capon, and norm-constrained Capon (NC-Capon) were utilized, in which the NC-Capon was applied to FAIs for the first time and found to be more suitable for the present study. The aspect angles estimated by the NC-Capon algorithm ranged between 0.1° and 0.4° mostly, which are close to the previous measurements with the radar interferometry (RI) made for the lower mid-latitude sporadic E region and the equatorial electrojet irregularities.
Heterogeneity of soil organic carbon dynamic regulated by microtopography in boreal peatlands
Authors: Wang Ming
Published: February 2023

Hummock-hollow microtopography is common in the northern peatlands of the world, but its effects on soil organic carbon (SOC) components are still poorly understood. In this study, we investigated effects of microtopography on SOC stocks and soil labile organic carbon (LOC) fractions in a sedge peatland in Changbai Mountain in northeast China. We found that SOC and soil LOC fractions had much heterogeneity in microtopography. SOC concentration in hummocks was significantly higher than under hummocks and in hollows. On average, the total SOC stock to a depth of 0.3 m below the ground surface was 19.00 kg C/m2. 56% of the total SOC stock was stored in soils in and under hummocks, despite the hummock only covering 30% of the total area. Light fraction organic carbon (LFOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC) in hummocks were significantly higher than under hummocks and in hollows. In addition, the cumulative soil CO2 emissions in hummocks were 2.0 and 4.5 times higher than those under hummocks and in hollows. The temperature sensitivity of soil CO2 fluxes (Q10) were 1.55, 1.67, and 1.52 in hummock, under hummock and in hollow, respectively. Redundancy analysis (RDA) identified that SOC explained most variations in soil LOC fractions (59.6%), followed by soil total phosphorus (7.4%) and soil water content (6.6%). Our findings indicate that the hummocks are important carbon pool in the sedge peatland, but they are vulnerable to global warming and human disturbance. Hummock-hollow microtopography creates heterogeneity in hydrological conditions and soil physicochemical properties, and thus influences SOC stocks and soil LOC fractions at a small scale. This study highlights the importance of microtopography in carbon storage and cycling and has direct implications for the assessment of the carbon sequestration function in northern peatlands.
Study of the Local Bow Shock Environment during Magnetosheath Jet Formation: Vlasiator Results
Authors: Suni Jonas , Palmroth Minna , Battarbee Markus , Turc Lucile , Alho Markku , Cozzani Giulia , Dubart Maxime , Ganse Urs , George Harriet , Gordeev Evgeny , Grandin Maxime , Horaites Konstantinos , Papadakis Konstantinos , Pfau-Kempf Yann , Tarvus Vertti , Tesema Fasil , Zaitsev Ivan , Zhou Hongyang
Published: February 2023

Magnetosheath jets are a class of phenomena that are usually defined as structures of enhanced dynamic pressure in the magnetosheath. The origins of some jets have been traced back to steepening ULF waves in the foreshock, but other formation mechanisms have also been described. In this study we use four 2D simulation runs of the global magnetospheric hybrid-Vlasov simulation Vlasiator to investigate the formation of magnetosheath jets at the bow shock. We use 2D views of the simulation and virtual spacecraft to investigate the plasma and magnetic field properties around and at the times and locations of jet formation. We find that of the 796 jets analysed this way, 91% appear to form in association with foreshock structures of enhanced dynamic pressure impacting the bow shock. These jets mainly form downstream of the ULF foreshock, while the remaining 9% are generally found near the ULF foreshock edges toward the flanks and have different properties from the foreshock structure-associated jets.
Machine learning for non-orographic gravity waves in a climate model
Authors: Hardiman Steven , Scaife Adam , van Niekerk Annelize , Prudden Rachel , Owen Aled , Adams Samantha , Dunstan Tom , Dunstone Nick , Seabrook Melissa
Published: February 2023

There is growing use of machine learning algorithms to replicate sub-grid parametrisation schemes in global climate models.  Parametrisations rely on approximations, thus there is potential for machine learning to aid improvements.  In this study, a neural network is used to mimic the behaviour of the non-orographic gravity wave scheme used in the Met Office climate model, important for stratospheric climate and variability.  The neural network is found to require only two of the six inputs used by the parametrisation scheme, suggesting the potential for greater efficiency in this scheme.  Use of a one-dimensional mechanistic model is advocated, allowing neural network hyperparameters to be trained based on emergent features of the coupled system with minimal computational cost, and providing a test bed prior to coupling to a climate model.  A climate model simulation, using the neural network in place of the existing parametrisation scheme, is found to accurately generate a quasi-biennial oscillation of the tropical stratospheric winds, and correctly simulate the non-orographic gravity wave variability associated with the El Nino Southern Oscillation and stratospheric polar vortex variability.  These internal sources of variability are essential for providing seasonal forecast skill, and the gravity wave forcing associated with them is reproduced without explicit training for these patterns.
The influence of water-saturation on the strength of volcanic rocks and the stability of lava domes
Authors: Heap Michael , Harnett Claire , Farquharson Jamie , Baud Patrick , Rosas-Carbajal Marina , Komorowski Jean-Christophe , Violay Marie , Gilg Albert , Reuschlé Thierry
Published: February 2023

The rocks forming a volcano are typically saturated or partially-saturated with liquid. However, most experiments aimed at better understanding the mechanical behaviour of volcanic rocks have been performed on dry samples, and therefore most large-scale models designed to explore volcanic stability have used parameters representative for dry rock. We present a combined laboratory and modelling study in which we (1) quantify the influence of water on the mechanical behaviour of variably altered dome rocks from La Soufrière de Guadeloupe (Eastern Caribbean) and (2) use these new laboratory data to investigate the influence of water on dome stability. Our laboratory data show that the ratio of wet to dry uniaxial compressive strength (UCS) and Young's modulus are ~0.95–0.30 and ~1.00–0.10, respectively. In other words, the rocks were all weaker when saturated with water. We also find that the ratio of wet to dry UCS decreases with increasing alteration (the wt% of secondary minerals). Micromechanical modelling suggests that the observed water-weakening is the result of a decrease in fracture toughness (KIC) in the presence of water. We also find that the ratio of wet to dry KIC decreases with increasing alteration, explaining why water-weakening increases with alteration. To explore the influence of water saturation on dome stability, we numerically generated lava domes using the experimental data corresponding to dry unaltered and altered rock, in Particle Flow Code. The strength of the dome-forming rocks was then reduced to values corresponding to wet conditions. Our modelling showed that, although the stability of the unaltered dome was not influenced by water saturation, large displacements were observed for the altered dome. Additional modelling in which we modelled a buried alteration zone within an unaltered dome showed that higher displacements were observed when the dome was water saturated. We conclude that (1) the presence of water reduces the UCS and Young's modulus of volcanic rock, (2) larger decreases in UCS in the presence of water are observed for altered rocks, and (3) large-scale dome stability modelling suggests that the stability of a dome can be compromised by the presence of water if the dome is altered or contains an altered zone. These conclusions highlight that the degree of alteration and water saturation should be monitored at active volcanoes worldwide, and that large-scale models should use values for water-saturated rocks when appropriate.
Towards an implementation of topography in a next-generation gravity-wave parameterisation
Authors: Achatz Ulrich , Chew Ray , Dolaptchiev Stamen
Published: February 2023

The Multi-Scale Gravity Wave Model (MS-GWaM) uses raytracing-based modelling that supports transient gravity-wave parametrisation. The state-of-the-art implementation of MS-GWaM in the upper-atmosphere ICON model solves the raytracing equations in three dimensions and accounts for background (non-orographic) and convective gravity-wave sources. Our work extends the capabilities of MS-GWaM to include orography gravity-wave sources, and we present methods and preliminary results towards this goal. Specifically, we first determine the spectral representation of the topography in each ICON grid cell via Fourier fitting. We then apply linear theory to obtain a representation of the bottom boundary for the raytracer. Finally, the bottom boundary serves as an initial condition for the raytracer-based parametrisation of orographic gravity waves. Preliminary results indicate that a judicious setup of this bottom boundary allows for an optimal tradeoff between computational efficiency and a sufficiently accurate representation of the underlying topography.