bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated Modeling of Cu-Rich Fluid Migration and Mineralization in the Katangan Basin, Central African Copperbelt: Insights from Numerical Experiments
Authors: Bahlali Meissam , Woitischek Julia , Jacquemyn Carl , Purkiss Martin , Jackson Matthew
Published: March 2024

Sediment-hosted Cu deposits are a significant global source of copper. This study employs a mineral system approach, focusing on basin-scale groundwater flow as a key mechanism for Cu transport from source to trap. Numerical experiments using the open-source IC-FERST code investigate the controls on Cu transport in the Katangan Basin, Central African Copperbelt. The models developed for early and late stages of basin evolution incorporate fluid flow, heat and solute transport, and dynamic mesh optimization to enhance computational efficiency.The early-stage model, corresponding to the salt deposition period, attributes the formation of saline brine to a dense residual phase resulting from evaporite formation. In the late-stage model, corresponding to Cu mobilization and mineralization, Cu dissolution and mineralization are simulated using a partition coefficient informed by experimental data.Results reveal that density gradients induced by salinity and temperature variations play a crucial role in initiating convective groundwater flow. Highly saline, dense brines generated during salt deposition or dissolution form complex, downward-propagating plumes influenced by flow instabilities and geologic heterogeneity. Permeable faults and fractures in basement rocks enable groundwater to percolate, potentially mobilizing Cu from intra- or extra-basinal source rocks. Salinity and temperature gradients drive upwelling plumes, transporting Cu from deeper source rocks to shallower, organic-rich sedimentary rocks where mineralization occurs.
Deep Learning improved seasonal forecasts for the Blue Nile Basin
Authors: Wiegels Rebecca , Glawion Luca , Polz Julius , Chwala Christian , Weber Jan Niklas , Schober Tanja C. , Lorenz Christof , Kunstmann Harald
Published: March 2024

Seasonal predictions are essential in mitigating damage to people and nature as a result of climate change and extreme events by improving timely decision-making particularly for water and irrigation management. The newly constructed Grand Ethiopian Renaissance Dam, located in the Blue Nile (BN) Basin in Ethiopia at the border to Sudan, increases the urgency of optimized transboundary water management and improved seasonal predictions. However, the global seasonal forecasting systems have known limitations such as biases and drifts. Specifically at regional level, such as in the highlands of Ethiopia, the seasonal predictions need accurate post-processing. Recent developments have shown the large potential of Deep Learning (DL) applications to improve weather and climate predictions. The goal of this study is to improve the global seasonal forecasting system SEAS5 of ECMWF specifically for the BN Basin using DL approaches such as conventional Convolutional Neural Networks (CNN) or more advanced Adaptive Fourier Neural Operators (AFNO). We present first results for improving and downscaling SEAS5 global seasonal precipitation forecasts in the BN Basin with a particular emphasis on ensemble generation and calibration. The neural networks are trained with ERA5-Land-reanalysis data as a ground-truth, which has a higher resolution than SEAS5 (~9km compared to ~36km). This additional downscaling step allows us to consider the high variations in precipitation intensities in the Ethiopian highlands. The results show that the applied DL models have high potential in improving forecasting scores such as the continuous ranked probability skill score. They therefore allow for improved timely decision-making for water management in the transboundary BN Basin.
Geotechnical Characterization of theLithological Map of Italy
Authors: Monte Nunzia , Bucci Francesco , Santangelo Michele , Reichenbach Paola , Di Matteo Lucio , Marchesini Ivan
Published: March 2024

The increasing availability of computational resources and the widespread use of distributed and parallel computing applications, enable the possible application of physically distributed geo-hydrological models at regional and national scales. However, the potential use of these models is constrained by the lack of data on the geotechnical and lithologic characteristics of rocks and materials. In a recent study, Bucci et al. (2022) published a lithological map of Italy at a 1:100k scale with the specific aim of facilitating the modelling of geo-hydrological phenomena. However, the lithologies on the map are not associated with values or ranges of values of the most important geotechnical parameters relevant to slope stability assessment such as: porosity, influencing soil permeability and drainage capacity, and cohesion and angle of friction, which contribute to defining the soil's resistance to erosion.An ongoing work at CNR-IRPI, is aimed at assessing whether and how many of the lithotypes presented in Bucci et al. map (2022) can be characterized from a geotechnical perspective and with what level of precision. More than 100 articles published in indexed journals were examined, to extract information on cohesion, friction angle, and porosity for more than108 different lithotypes.Most of the articles report data obtained through laboratory tests, field experiments, or empirical approaches. The minority of the articles, uses bibliographic sources, or provides data obtained in a mixed manner. The values of cohesion, friction angle, and porosity obtained and assigned to different lithological classes reveal, as expected, significant variability. The range of the values can be attributed to various factors, including: (i) assumptions made to assign specific rocks, formations, or soils to the (few) lithological classes present in the 1:100k map; (ii) the diversity of geological conditions in which lithotypes are formed; (iii) methods and approaches in data acquisition, and (iv) the natural variability of material characteristics.The results will allow to better characterize or subdivide the lithotypes shown in the cartography by Bucci et al. (2022), with the purpose to reduce uncertainty regarding the values of geotechnical parameters that can be used in physics-based slope stability models.ReferenceF. Bucci , M. Santangelo, L. Fongo , M. Alvioli , M. Cardinali, L. Melelli , and I. Marchesini . A new digital lithological map of Italy at the 1 : 100 000 scale for geomechanical modelling. Earth Syst. Sci. Data, 14, 4129–4151, 2022 https://doi.org/10.5194/essd-14-4129-2022 
Solar Orbiter: Mission Goals, Recent Discoveries, and Future Outlook
Authors: Rivera Yeimy
Published: March 2024

ESA’s Solar Orbiter mission, launched in February 2020, is designed to investigate how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To achieve its objectives, Solar Orbiter is equipped with a comprehensive suite of remote sensing and in situ instruments that work in concert to connect coronal structures and phenomena to their heliospheric counterparts. It aims to advance our understanding of the solar dynamo, responsible for the Sun’s magnetic cycle, by venturing out of the ecliptic plane to directly observe the Sun’s polar regions, providing an unprecedented view of our star. Since its launch, Solar Orbiter has completed 5 perihelion passes below the orbit of Mercury where it has taken the most detailed images of the Sun to date. The high resolution images have revealed previously unresolved coronal features that deepen our knowledge of how the corona is heated and the solar wind is formed, as well as how eruptions are triggered and release energy. As we now enter farther into solar maximum, the mission is perfectly placed to gain fresh insight to how transients drive heliospheric variability and impact local space weather. As such, the talk will present a brief overview of the overarching Solar Orbiter science objectives, discuss recent discoveries by the mission, and outlook for future observations and its exciting journey out of the ecliptic plane.
Changes in ambient concentrations of monoterpenes during the winter-summer transition period in an urban site of India
Authors: Sahu Lokesh , Malik Tanzil , Gupta Mansi , Tripathi Nidhi
Published: March 2024

In the earth’s atmosphere, volatile organic compounds (VOCs) are emitted from natural (biogenic) and anthropogenic sources. VOCs are important components of photochemical processes with strong significance to atmospheric chemistry and climate change through the formation of ozone and organic aerosols. Despite their large biogenic emissions and strong photochemical cycling under the tropical conditions, the speciated measurements of biogenic-VOCs (BVOCs) over the South Asia region are extremely rare. Recently, a project “Network of Volatile Organic Compounds (VOCs) Measurements in India: Biosphere-Atmosphere Exchange” has been implemented for the measurements of BVOCs over different environments of India and surrounding oceanic regions. We have conducted ambient air measurements of C6-C12 compounds at an urban site of Ahmedabad in western part of India during January-May 2020. The well time resolved continuous measurements provided excellent dataset to characterize the diurnal, day-to-day, and seasonal variations of VOCs originated from both biogenic and anthropogenic sources. The mains scientific focus of this study is to characterize the ambient air variations of α- and β-pinene, which are the main representatives of the monoterpene group. Unlike the large reductions in concentrations of anthropogenic VOCs during summer also coinciding with COVID-19 lockdown, the mixing ratios of α- and β-pinene showed a strong increasing trend from winter to summer. The monoterpenes showed clear diurnal patterns with higher night-time and daytime concentrations during winter and summer season, respectively. The monthly mean mixing ratios of α-pinene and β-pinene varied n the ranges of 10-22 and 3-16 pptv, respectively. Despite minimum anthropogenic influences and intense photo-oxidation loss in summer of 2020, the huge enhancements of monoterpenes in ambient air indicate the strong biogenic emissions from local vegetation. Our analysis indicate the combined effect of the northwest wind flow and higher air temperatures leading to high emissions of BVOCs from local vegetation.
An evaluation of the Southern Annular Mode in the Twentieth Century Reanalysis
Authors: Jones Julie , Lorrey Andrew , Fogt Ryan , Slivinski Laura , Compo Gilbert , Brohan Phillip , Marshall Gareth
Published: March 2024

We explore whether improvements to the Twentieth Century Reanalysis (20CR) in the most recent version (v3) have improved representation of the Southern Annular Mode (SAM).  The negative SAM index bias in the first half of the 20th century compared to instrumental SAM reconstructions in previous 20CR versions (due to a systematic high latitude high pressure bias) is still present. It is reduced in summer and autumn, but not in winter and spring.  Correlations between reanalysis and reconstructed SAM indices through the full series in all seasons do show improvements in v3 compared to previous versions.  A reduction in SAM index ensemble spread is evident during periods with higher numbers of assimilated observations, in particular in summer and autumn.  Analysis of the spatial distribution of assimilated observations shows clear improvement in years/periods with greater numbers of ships observations in the Southern Ocean and Antarctic observations (e.g. early 20th century Antarctic expeditions).  However it is not until the advent of greater numbers of ships observations in the Southern Ocean and regular data from Antarctic meteorological stations in the late 1940s that there are enough high latitude observations to realistically constrain the reanalysis.  Enhancements have been enough to improve how the reanalysis follows the observations temporally, highlighting the benefit of data rescue, but due to the bias, we recommend that the 20CR should still not be used for the analysis of long-term SAM trends, and caution should be exerted when using SLP data from the high latitude Southern Hemisphere from all 20CR versions prior to 1957.
Non-target screening analysis on ice and snow samples: a new opportunity to enhance our understanding on past and present atmospheric aerosol composition.
Authors: Burgay Francois , Singer Thomas , Salionov Daniil , Sharkov Dmitrii , Eichler Anja , Jenk Theo , Bruetsch Sabine , Huber Carla , Vogel Alexander , Barbaro Elena , Maffezzoli Niccolo , Scoto Federico , Isaksson Elisabeth , Ramirez Librada , Bjelic Sasa , Schwikowski Margit
Published: March 2024

Organic aerosols make up to 70-90% of the total aerosol mass, yet ice-core studies have predominantly focused on a limited set of compounds or bulk fractions altogether. Previous investigations have centered on biomass burning tracers, marine phytoplankton oxidation products, low molecular weight carboxylic acids and persistent organic pollutants, leaving a large majority of molecules unidentified. Advances in high-resolution mass spectrometry (HRMS) have recently enabled the exploration of a wider chemical space through the development of non-target screening (NTS) workflows.In this work, we present three applications of a novel NTS method. Designed to detect secondary organic aerosol compounds in ice-core and snow samples, the method has contributed to a more comprehensive characterization of past molecular aerosol composition and has supported the development of new molecular proxies. Initially, the method was applied to the Belukha ice core (Siberian Altai, 4072 m. a.s.l.) between 1830 and 1980 CE, providing the first NTS ice-core record that embraces both the pre-industrial and industrial periods. More than 400 compounds were identified, and a clear anthropogenic fingerprint was recognized over the industrial period. Subsequently, the ice core samples from Colle Gnifetti (Switzerland, 4500 m. a.s.l.) covering the period from 1750 to 2000 CE were analyzed. Here, a smaller number of molecules was detected (≈200), consistent with the lower concentrations of dissolved organic carbon observed at this site. In both cores, most of the molecules are composed of carbon (C), hydrogen (H) and oxygen (O) and are associated with atmospheric oxidation of monoterpenes and isoprenes (e.g., succinic acid, pinic acid, azelaic acid). The industrial onset was characterized by an increase in nitrogen and sulfur containing compounds, likely due to the atmospheric reactions with anthropogenic NOx and  SO2. The higher occurrence of compounds with higher O/C ratios during the industrial period observed at both locations, suggests an increase in the atmosphere oxidative capacity. Lastly, the method was applied to 56 snow samples collected in springtime close to Ny-Ålesund (Svalbard Archipelago) and covering both pre- and phytoplankton bloom periods. Together with marine observations of algal bloom, the NTS results suggest promising evidence towards new ice-core marine productivity proxies for long-term reconstructions.
Data assimilation and the reconstruction of surface fluxes in quasigeostrophic and transport equations.
Authors: Bröcker Jochen , Carigi Giulia , Kuna Tobias , Martinez Vincent Ryan
Published: March 2024

In this contribution, we will analyse simple data assimilation schemes that not only estimate the underlying states of a dynamical system but simultaneously reconstruct unknown components of the dynamics. We focus on quasigeostrophic and transport-diffusion equations (for instance for atmospheric aerosols or tracer gases) and reconstruct forcings or surfacd fluxes, along with the underlying dynamical states. Tracer gases and aerosols play an important role in the dynamics of the atmosphere; aerosols for instance act as condensation nuclei and thus have a major influence on precipitation, while tracer gases such as ozone, methane, or CO2 impact the radiative transfer and are thus linked to important atmospheric phenomena such as the ozone hole and the energy budget of the planet ("greenhouse effect"), respectively. Furthermore, gases as well as aerosols (especially in the lower troposphere) are common pollutants with strong and potentially adverse effects on the environment, human activity, and health. We discuss two algorithms that both apply in the context of the quasigeostrophic as well as the transport-diffusion equations.
Overview of SMÄLTA: Secondary Marine Aerosol precursors and Links to aerosol growth at ice-melT onset in the Arctic
Authors: Zang Cort , Willis Megan , Asplund Julia , Mattsson Fredrik , Zieger Paul , Tjernström Michael
Published: March 2024

The sources, composition, and reactive transformation of reactive organic carbon (ROC, non-methane organic carbon) as well as the processing, abundances, and distribution of organosulfur compounds in the Arctic marine atmosphere are unconstrained partially due to a lack of targeted measurements.  Understanding the emission, transport and processing of ROC and organosulfur compounds is important for improving our understanding of the impacts of gaseous precursors on aerosol nucleation and growth, and atmospheric oxidation capacity. There is a shift in aerosol size distribution that occurs with the Arctic spring-to-summer transition period and there are very few Arctic marine measurements of trace gases during this same period. Constraining the composition of organosulfur compounds and ROC is important for understanding the drivers in the shift of aerosol size distribution.We present shipborne gas-phase measurements of ROC and organosulfur compounds in the Arctic marine atmosphere as part of the Atmospheric Rivers and the onseT of sea ice MELT (ARTofMELT) campaign. ARTofMELT took place from May 7th to June 15th of 2023 over pack ice and within the marginal ice zone between 78 and 81°N in the Fram Strait. We deployed a reagent ion switching chemical ionization mass spectrometer to target ROC and organosulfur compounds using H­3O+ ionization for the detection of reduced compounds and NH4+ ionization for the detection oxidized species. The measurements encompass a variety of different conditions including ozone depleted air masses (
Integrating and managing nitrogen and phosphorus dynamics in agriculturally impacted inland waters via a stoichiometric nutrient management framework
Authors: Graeber Daniel , Große Anika , Westphal Katja , Wachholz Alexander , Stutter Marc , Weigelhofer Gabriele , Davidson Thomas Alexander , Shatwell Tom , Musolff Andreas , Kumar Rohini , Borchardt Dietrich
Published: March 2024

Agricultural nutrient management tends to treat nitrogen (N) and phosphorus (P) in surface waters as separate entities, potentially overlooking their strong interactions in biogeochemical cycles. This study proposes a unifying approach by integrating these nutrients through a stoichiometric nutrient management framework. This framework suggests two paradigm shifts in inland-water nutrient management: 1. It improves catchment and ecosystem-level understanding of N and P sources and effects via N : P ratio assessments of sources, transport and ecological effects, such as eutrophication. 2. It proposes that provision of organic carbon (OC) can increase the retention of N and P in agriculturally impacted inland waters, which can be assessed using C : N : P ratios. Provision of OC to modify C : N : P ratios may be reached through restoring natural OC sources. This can be done by focusing on areas such as wetlands, riparian forests, and bogs at catchment scale. Here, stoichiometric rules are utilized to assess the responses of key microbial processes, which includes examining how nutrients are assimilated by microbial primary producers and heterotrophs, as well as the process of denitrification. Understanding the secondary effects of wetted area development through the stoichiometric nutrient management framework will also support decision making for flood and drought protection based on such wetted areas. With these aspects, the stoichiometric nutrient management framework provides comprehensive understanding of nutrient dynamics, retention, and their ecological impacts in inland water catchments and ecosystems. In the presentation, we will present evidence supporting the comprehensiveness of the stoichiometric nutrient management framework. This evidence is based on a series of studies we conducted, including conceptual modeling, statistical modeling, ratio-based monitoring, and targeted proof-of-concept microcosm experiments. We conclude that the stoichiometric nutrient management framework could provide crucial strategies to mitigate current nutrient pollution issues in agriculturally-impacted inland waters, thereby aligning with the Water Framework Directive’s objectives for improving water quality.
Identification of river channel bankfull geometry from topographic indicators extracted from high-resolution digital elevation datasets 
Authors: Ruscitto Valeria , Delchiaro Michele , Schwanghart Wolfgang , Brignone Eleonora , Piacentini Daniela , Troiani Francesco
Published: March 2024

River channel bankfull geometry and discharge are important features providing valuable insights into fluvial monitoring and flood recurrency. The bankfull stage represents the riverbank position that approximates the level at which water overflows onto the floodplain. Bankfull discharge is considered the channel-forming discharge, with a recurrence interval of approximately 1.5 years. Bankfull floods are significant, as they are highly effective in changing channel shape and characteristics. Their recurrence intervals can be used for stream assessment and have implications for infrastructure design and flood mapping. Additionally, gaining insights into the factors influencing floodplain inundation across various time periods is crucial, as the frequency of flood events is predicted to rise with the increase in global temperatures.In this contribution, we present a novel approach to identify the bankfull geometry through a set of dedicated MATLAB functions. A Digital Elevation Model (DEM) with ground resolution of 1 m/pixel is used as input elevation dataset, obtained with airborne LiDAR (Light Detection and Ranging) survey. The selected river channels are divided in regularly spaced sampling sections, where the bankfull geometry is extracted. Then, the hydraulic depth function that plots the elevation above the river thalweg vs. the ratio between the area and the width is computed for every section. Then, the elevation above river associated to the lowest and the most prominent peaks of the function, corresponding respectively to the bankfull stage or bankfull/floodplain inflection point and to the floodplain, are automatically extracted for each section. Manning’s equation is then applied to the hydraulic geometry corresponding to the lowest peaks elevation to compute the bankfull discharge at every river channel section. The validation process includes the comparison between the results obtained through the automatic bankfull geometry and discharge estimation and discharge data available from river hydrological gauges. Results demonstrate that the developed approach is effective to delineate the bankfull geometry from high-resolution DEMs and complements traditional qualitative field observations. Thus, our approach represents a cost-effective alternative for mapping detailed spatial variations over large spatial extents that are difficult to cover with traditional fieldwork.
The impact of Greenland ice sheet melt on the future North Atlantic ocean circulation
Authors: Mehling Oliver , Bellomo Katinka , Fabiano Federico , Devilliers Marion , von Hardenberg Jost , Corti Susanna
Published: March 2024

Changes in surface freshwater fluxes are a main factor governing the response of the ocean circulation to future climate change. However, they are not well-represented in the most recent generation of Earth System Models (CMIP6), as most CMIP6 models do not include an interactive ice sheet component. Instead, most of them use a very idealized representation of ice sheets. While this approach may yield the correct order of magnitude for present-day meltwater runoff, it might not accurately extrapolate the increasing ice melt under future global warming.Here, we address this deficiency by prescribing physically plausible meltwater fluxes from the Greenland ice sheet in a CMIP6 model, EC-Earth3, under a strong global warming scenario (SSP5-8.5) until the 23rd century. The meltwater fields were obtained from a CESM2-CISM simulation in which the Greenland ice sheet was fully coupled. The corresponding meltwater flux reaches about 0.4 Sv by the year 2300, comparable to what is often used in water hosing experiments. Using two EC-Earth ensembles of four members each (with and without Greenland meltwater flux), we compare the impact of this previously underestimated runoff on long-term projections of deep-water formation in the North Atlantic and on the evolution of the Atlantic Meridional Overturning Circulation. Our results allow us to quantify the importance of Greenland meltwater on AMOC weakening under strong global warming.
Response of natural dust to removal of anthropogenic emissions over South Asia
Authors: Stevenson David , Agarwal Prerita , Heal Mathew , Zaveri Rahul
Published: March 2024

We use the regional chemistry transport model WRF-Chem (v4.2.1) to analyse the sensitivity of surface dust across Northern India to various emissions' sources. We use idealised model experiments that switch off individual sources in an attempt to apportion dust aerosol concentrations to anthropogenic, biomass-burning, and natural dust sources. However, these experiments show significant non-linear interactions between sources, making simple apportionment difficult. Across the natural dust-dominated western part of the domain, we find that switching off anthropogenic emissions results in an increase in dust. Alternatively, this can be considered in the opposite sense: the presence of anthropogenic pollutants reduces surface dust aerosol concentrations by almost 50 % on average. We diagnose the processes responsible for this somewhat surprising result. Heterogeneous chemical reactions between dust and nitric acid (HNO3) shorten the dust’s lifetime, increasing the sink for natural dust as HNO3 is enhanced by anthropogenic NOx emissions. The modelled dust lifetime is enhanced by nearly 4 hours when anthropogenic precursor emissions are excluded. The model shows a strong anticorrelation between dust and HNO3, related to the preferential uptake of HNO3 by dust particles over a broad relative humidity range (10 – 90 %). The strong non-linear response of dust loading to idealised emissions changes shows considerable regional variation. The effect of these dust-pollution interactions on dust lifetime suggest that dust concentrations will increase as anthropogenic NOx emissions reduce, making control of particulate pollution harder, particularly in regions with high natural dust sources.
Understanding Hyporheic exchange flows around a meandering section of pristine Himalayan headwaters
Authors: Reddy P Kedarnath , Sen Sumit
Published: March 2024

River systems, such as the Himalayan, consist of three zones: source (high mountains, glaciers), transition (lower mountains, agriculture), and floodplain. About 800 million people in the highlands and Indo-Gangetic plains depend on the Himalayas, hence called the "Water towers of Asia," for freshwater (Kulkarni et al., 2021). While the transition zone contains lower mountains and sustains agricultural activities, the source zone has severe gradients, high peaks, and deep valleys (Nepal et al., 2014). Hence, it is imperative to understand the river systems. It is important to explore methods that have the potential to increase the water quality by inherent natural processes of lotic systems that can assimilate contaminants. One such process is Hyporheic exchange (HE). Keeping in mind the expenses associated with field testing and with the goal of facilitating the development of a deeper understanding over a greater spatial extent, a cost-effective approach is sought. Thus, my study aims to develop a preliminary understanding of hyporheic exchange in the pristine Himalayan headwaters over a meandering section of the Ringali gad stream flowing through the Mussoorie Wildlife Sanctuary. Wherein mini drive point piezometers were used to measure vertical hydraulic gradient (VHG) variations in response to rainfall events over a period of 30 days, and it is observed that the downwelling zones that were giving VHG values of around -0.1 also converted to upwelling zones with VHG values of around +0.1.
Ensemble Data Assimilation with Model Error Inclusion for Estimating Fault-Slip Occurrence in Large-Scale Laboratory Experiments
Authors: Diab-Montero Hamed Ali , Li Meng , van Dinther Ylona , Vossepoel Femke C
Published: March 2024

The forecasting of earthquake occurrence remains a significant challenge in seismology, primarily due to uncertainties in understanding the current state of stress, strength, and the parameters controlling the slip behaviour of faults. Among these parameters, friction parameters are crucial as they control the earthquake recurrence interval and their nucleation size. There is a critical gap in effectively integrating observational data with physics-based models, particularly in the face of parameter bias. This study addresses how ensemble data assimilation methods can be optimized to address these challenges and reduce uncertainties in fault-slip estimates.Our objective is to enhance the accuracy of earthquake forecasting by incorporating model error into ensemble data assimilation methods, thus improving the estimation of critical state variables such as shear stress and slip velocity. We employed the Ensemble Kalman (EnKF), Adaptive Gaussian Mixture (AGMF), and Particle Flow (PFF) filters, which are integrated with earthquake sequence models. These methods were applied in two stages: 1) Perfect model experiments using 1-D Burridge-Knopoff models to assess the benefits of including model error in estimating non-periodic and chaotic behaviours in low-dimensional systems. 2) Application in a meter-scale direct-shear laboratory setup, assimilating measurements from shear-strain gauges near the fault, to examine the effects of varying normal stress profiles on the fault on the estimates and the impact of including model error.The perfect model experiments demonstrated improved estimation of shear stress, slip velocity, and the state variable (θ), particularly in estimating non-periodic sequences and chaotic behaviour using stable periodic solutions when confronted with small parameter biases. In the laboratory setup, variations in normal stress profiles significantly influenced the information content. Sensor placement relative to the fault and seismic phase was found to critically impact the observations' informational value, with sensor proximity to the fault being a critical aspect and the information content being higher around the coseismic phase.This research provides valuable insights into the intricate process of earthquake forecasting, underscoring the role of data-assimilation techniques in enhancing our understanding and forecasting abilities in this field.
A machine learning approach to structure and energy in magnetic reconnection
Authors: Waters Cara , Eastwood Jonathan , Fargette Naïs , Goldman Martin , Newman David , Lapenta Giovanni
Published: March 2024

Magnetic reconnection is a fundamentally important process in space plasmas due to the release and repartition of the magnetic energy stored within the reconnecting field. As this energy transfer significantly impacts magnetospheric dynamics, understanding the partition of this energy and how this varies across the reconnection site can provide further insight into other magnetospheric processes. Although in situ spacecraft data provide direct measurements of relevant plasma properties, it can be difficult to establish the location of spacecraft relative to the reconnection site. This frustrates efforts to evaluate the way in which energy fluxes change with distance from the central reconnection X-line. Under certain circumstances, reconstruction techniques can be used to estimate the spacecraft trajectory through individual events, but these may rely on simplifying assumptions limiting their use.This motivates new approaches to determining where a spacecraft is relative to the reconnection structure. By utilising forefront machine learning techniques, we can more accurately study individual regions associated with the reconnection process and thus understand how they individually contribute to repartitioning the overall energy budget. In this context, we present these new applications of machine learning techniques to identify the regions in both simulation and spacecraft data.Firstly, we present the results of a robust method which utilises k-means clustering to identify different regions encountered within the overall reconnection X-line structure. This uses plasma fluid and field variables output by a 2.5-D PIC simulation with a geometry comparable to that of reconnection in Earth’s magnetotail. We then translate this model for use in spacecraft data by implementing an approach based on a recurrent neural network to account for the temporal context of the observations. We demonstrate the use of this model on MMS observations of reconnection in the Earth’s magnetotail, examining the properties of the plasma energy flux in different regions. We conclude by discussing how this approach may find use in other contexts where reconnection is observed in space plasmas.
Detecting Multiscale Carbon Controls in a Mediterranean Tree-Grass Ecosystem with Different Fertilization Treatments
Authors: Nadolski Laura , El Madany Tarek , Carrara Arnaud , Nelson Jacob , Hildebrandt Anke , Reichstein Markus , Lee Sung-Ching
Published: March 2024

Semi-arid ecosystems significantly impact the variability of the global terrestrial carbon sink and are influenced by a changing climate as well as anthropogenic nitrogen deposition. To understand how different nutrient availability impacts the drivers of net ecosystem exchange (NEE) in these ecosystems across temporal scales, we analyze a long-term dataset of biometeorological, soil and flux data from 2016 to 2022 from three Eddy Covariance (EC) measurement stations in Western Spain. The site (Majadas de Tiétar) is a Mediterranean tree-grass ecosystem home to a large-scale fertilization experiment. One station area received nitrogen treatment, another one both nitrogen and phosphorus treatments, and the third one serves as control. We apply Singular Spectrum Analysis to identify the variability of the different variables on multiple timescales (daily, multiday, seasonal). We then utilize metrics of mutual information to identify the main drivers of NEE across these timescales.Preliminary findings show an increase in NEE dynamics in the fertilized areas both at ecosystem scale and at the grass-layer only. The dominant factors driving the dynamics of NEE vary depending on the timescale. On the daily scale, NEE is closely coupled to radiation, whereas on the seasonal scale water availability gains importance in predicting NEE. We find that the importance of vegetation greenness at the tree layer increases with longer timescales, and that also soil temperatures affect NEE at seasonal timescale. The relationships are further modified by different nutrient availability. While on the daily scale the differences between the three fertilization treatments are marginal, they intensify at the seasonal scale. Our comprehensive analysis facilitates a detailed understanding of the complex interactions between NEE and its controls under different environmental conditions and can help to improve the accuracy of terrestrial ecosystem models.
How did plate tectonics evolve? Insights from 3-D spherical thermochemical convection simulations
Authors: Yan Jun , Tackley Paul
Published: March 2024

Plate tectonics is a fundamental framework for understanding the geodynamic processes shaping our planet, including seismicity, volcanism, mountain building, and even the long-term climate system and habitability of our planet. However, how plate tectonics evolved over 4.5 billion years remains a major unanswered question. In this study, we employ dynamically self-consistent three-dimensional thermochemical geodynamic models to simulate plate tectonics evolution with physically realistic parameters. Our results demonstrate that plate tectonics undergoes three main stages due to differing dominant mantle cooling modes. Initially, magmatism dominates surface heat transport, with extrusive volcanism leading to a mobile heat-pipe mode, characterised by a high level of volcanism, large surface heat flux, and highly mobile plates in the first 1.5 billion years. This differs from the "heat-pipe" mode occurring on Jupiter's satellite Io by additionally having plate-like behaviour as well as crustal delamination and lithospheric dripping. As the mantle cools, it transitions to a stable mode where mantle convection patterns and their surface expressions become stable for around 1-2 billion years, followed by a smooth evolution to present-day plate tectonics. Our model matches key observations of the surface heat flux, strain rate, plate velocity, and plate distribution patterns, indicating that the early mobile heat pipe mode plays a crucial role in efficiently extracting heat from the mantle. Magmatic intrusion is also expected to have important effects, which we will examine. This study may provide insights into the Earth's dynamic processes and mantle-atmosphere feedback related to plate tectonics and the dynamic evolution of other terrestrial planets, which ultimately affect the long-term climate system and habitability of our planet.
Identification of the Storegga Tsunami offshore Shetland: implications for seabed infrastructure hazard risk assessment
Authors: Earland Jane , Scourse James , Ehmen Tobias , Kender Sev
Published: March 2024

The Shetland Islands (UK) are a seminal location for investigating palaeo-tsunami deposits. Onshore evidence suggests three tsunamis have occurred during the Holocene: the Storegga tsunami ca. 8175 cal yr BP, the Garth tsunami ca. 5500 cal yr BP and the Dury Voe tsunami ca. 1500 cal yr BP. However, to date no research has been published on the impact of tsunami on the subtidal shelf where a large amount of North Sea hydrocarbon infrastructure is located. During the SEACHANGE research cruise DY150 (2022), cores were recovered offshore east Shetland from the Fetlar Basin. The cores contained distinct sand and shell lenses within a Holocene mud sequence, indicating increases in bed shear stress. We test the hypothesis that these lenses represent the subtidal expression of North Sea tsunami. Radiocarbon dates bracketing the sand lenses overlap with the published dates for the Storegga tsunami, suggesting these sand lenses result from processes related to the Storegga tsunami. Dates within the deposit are older than the Storegga tsunami, indicating reworking and deposition of older sediments at the core site by the tsunami. Particle size analysis, ITRAX and MSCL data evidence increases in grain size, a reduction in sorting capacity, increased shell concentrations and peaks in associated elements (log(Ca/Fe), log(Ca/Ti) and Sr) and magnetic susceptibility. These attributes are typical of both palaeo and modern offshore tsunami deposits. No evidence was found within the cores for any later Holocene tsunami, due to either bioturbation, active currents, or lack of initial deposit. The data indicate that sediments in the Fetlar Basin were disturbed by the Storegga tsunami to palaeo-water depths of at least 88 m. This highlights the need to assess the potential impact of any future tsunami on existing or proposed hydrocarbon infrastructure.
Modelling the global geodynamic and seismological consequences of different phase boundary morphologies. 
Authors: Morgan Gwynfor , Davies J. Huw , Myhill Bob , Wookey James , Panton James
Published: March 2024

Throughout Earth’s mantle, several significant phase transitions occur, with the Ol→Wd and Rw→Brm+Pc reactions (exothermic and endothermic respectively) producing large discontinuities in Earth’s seismic velocity structure at 410 and 660km depth respectively (‘410’ & ‘660’). The equilibrium depth of these reactions is sensitive to temperature, and the resulting topography has been observed with various seismic phases. Numerical modelling from the 1980s onwards has suggested that the topography on endothermic phase transitions can stagnate downwellings and even layer mantle convection for extreme Clapeyron slopes or density changes. The thermodynamic properties of the post-spinel reaction make it unlikely that slabs would stagnate due to effects associated with phase transitions. At cooler temperatures the post-spinel reaction splits into two reactions (Rw + Ak → Ak + Pc → Brm + Pc) which seems to explain well aspects of the observed topography of the ‘660’ discontinuity. It has been suggested that this second reaction (which has a more extreme Clapeyron slope than the post-spinel reaction) could stagnate downwellings. Recently, Ishii et al (2023) suggested that the post-garnet reaction (Gt → Brm + Cor [+ St]) is in fact univariant, producing a sharp reaction that is endothermic for cooler temperatures and exothermic at higher temperatures – and that this may contribute to slab stagnation. Here, we test these slab stagnation mechanisms using realistic mineral physics and whole-mantle convection models (MCMs).The lack of anti-correlation between the topography of the ‘410’ and ‘660’ discontinuities does not match simple theory if they are controlled solely by temperature variations across the post-olivine and post-spinel reactions respectively. Previous work has shown that the calculated topography on the discontinuities can be markedly different for various single-composition mantles generated from MCMs (Papanagnou et al, 2022). Here we will explore the impact of laterally varying chemistry generated in thermochemical MCMs on global discontinuity topography.
Laminar Gypsum deposited during the Messinian salinity crisis acme: a case study from the Racalmuto basin (Sicily, Italy).
Authors: Nallino Enrico , Sabino Mathia , Dela Pierre Francesco , Natalicchio Marcello
Published: March 2024

During the late Miocene Messinian salinity crisis (MSC), the Mediterranean Basin was transformed into the youngest salt giant in Earth's history. The acme phase of the MSC appeared to have coincided with a high-magnitude sea level drop, resulting in widespread erosion of sulphate evaporites deposited in shallow, marginal basins during the early phase of the MSC. Clastic gypsum deposits were consequently emplaced by submarine mass movements and low to high-density gravity flows in deep basins interfingering with thick halite deposits and hemipelagic, laminated sediments including organic-rich shales and laminar gypsum. Deciphering the depositional mechanisms behind hemipelagites is pivotal to reconstruct the paleoenvironmental and paleoceanographic conditions of deep Mediterranean basins during the MSC acme, including water depth and chemical, physical and biological characteristics of the aquatic system. This work focuses on the Racalmuto basin (Sicily, Italy), where a continuous sedimentary record from the pre-evaporitic Tripoli Fm. to the final stages of the MSC (Upper Gypsum) is exposed. Here, the MSC acme is recorded by gypsum turbidites and a chaotic interval, interbedded with laminar gypsum (“balatino”) formed by nucleation of gypsum crystals in the water column and their subsequent deposition on the sea floor (cumulate deposits). The most typical microfacies consist of an intricated network of gypsum crystals with a rhombohedral to prismatic elongated habit (< 1 mm in size). Petrographic observations show textural changes across the studied interval. The size of the crystals progressively decreases upwards across the studied section, possibly reflecting the increase in the saturation of the brine approaching the time of halite deposition in the deeper parts of the basin. The appearance of a diversified calcareous nannofossils assemblage, interbedded with gypsum laminae immediately below the bottom-grown selenitic gypsum of the Upper Gypsum (final stage of the MSC) suggests that normal marine conditions were intermittently established in the upper water column approaching the end of the MSC acme.
Cyclostratigraphy of the Ediacaran Nama Group in Namibia based on photogrammetry
Authors: Spiering Bianca , Zwarts Maarten , Bissick Ajani , Boscaini Andrea , Davies Joshua , Halverson Galen , Gibson Brandt , Laflamme Marc , Hilgen Frederik
Published: March 2024

The middle Nama Group, deposited during the late Ediacaran in southern Namibia, is a 1 km-thick mixed carbonate-siliciclastic shallow-marine succession that displays observable regularity in its weathering profile. However, the possible role of astronomical climate forcing in this succession remains poorly understood. As a first step to understand the origin of the regularity, an initial cyclostratigraphic framework was developed using Google Earth satellite images and published U-Pb zircon ages of volcanic ash beds. Although the estimated average periodicity of 120-180 k.y. for the dominant scale of variation falls within the frequency band of astronomical forcing, it is not yet possible to discriminate between an origin related to short (~100 k.y.) eccentricity or 173 k.y. obliquity amplitude modulation. In order to refine the framework, we generated high-resolution quantitative records of the weathering profile based on drone photogrammetry. Spectral analysis on the depth series of slope steepness reveals significant spectral power related to the dominant variation at a scale of tens of meters. Additionally, it captures spectral power related to smaller-scale variations at less than 10 m. For age control, the depth series are linked to published U-Pb ages as well as to newly collected volcanic ash samples more closely tied to the analyzed sections. New high-precision dates will be crucial to determine the astronomical origin of these cycles.
Simulating the Colocation of High-Precision Microwave and Optical Techniques for Tropospheric Parameter Determination in Context of the ACES Mission.
Authors: Vollmair Peter , Schlicht Anja , Hugentobler Urs
Published: March 2024

The future Atomic Clock Ensemble in Space (ACES) mission of the European Space Agency (ESA) will address the development of a time transfer concepts for tomorrow's technologies. The ACES configuration includes a new generation of high-precision atomic clocks, a microwave link terminal (MWL) on the ground and on the satellite, and an optical detector and reflector also on the satellite. Due to the fact, that the official launch date is in 2025, there is a lack of real observation data. For that, a full-scale simulation software has been implemented. The simulator produces MWL code and phase observations in downlink and uplink, as well as one- and two-way laser observations. To analyse the efficiency of a time transfer concept before launch, we used the simulator to generate a data set of 100 passes during July 2021. Investigations based on this data set showed that the colocation of the high-precision geodetic observation techniques of the ACES mission could better separate the individual error contributions of a measurement. Due to the colocation of optical and microwave-based geodetic observation techniques, also error parameters like orbit and troposphere correction can be estimated together. Estimation of a common troposphere for all observation techniques, improves the accuracy of the determination of the offset between ground and ACES clocks. Our further investigations focus on the common troposphere estimation of multi-color optical observations, together with microwave-based observations and the effects of different weighting methods. An extension to a network of ground stations will demonstrate the advantages of the ACES mission for synchronizing multiple ground clocks. The colocation of different high-precision geodetic observation techniques and estimation of common parameters will benefit timing and ranging applications and fundamental physics studies.