bluuebunny/crossref_metadata_2025 huggingface dataset:
Crust necking of the northeastern South China Sea: Insights from deep seismic data
Authors: Deng Hongdan
Published: February 2023

During rifting, continental crust necks, leading to significant thickness reduction in a few tens of kilometres. However, deformations associated with the necking process remain elusive due to few outcrop examples and a lack of seismic data coverage that clearly images crustal architecture at depth. Here we use deep, high-resolution seismic data across a well-developed necking zone in the northeastern South China Sea passive margin to show the structural style associated with the crustal necking. Seismic stratigraphy in the necking domain can be divided into pre-, syn- and post-rift sequences based on the nature of sequence-bounding unconformities and their relation with faults. Seismic expression of continental crust exhibits two types of reflection characteristics – homogeneous upper crust and layered lower crust. The necking domain shows significant thinning that reduced its thickness from ~30 km to less than over 10 km in a distance of about ~50 km and is characterised by seaward removal of layered lower crust, while the homogeneous upper crust thickness remains largely unchanged in thickness. The necking domain is bounded by inner and outer breakaway complexes that define a portion of flexed crust. Crustal flexure is evidenced by progressive tilting of the necking domain that gradually increases the pre-rift sequence dip from 0° to 10°. Within the tilted necking domain, densely-spaced, landward-dipping minor faults and fractures are organised in a domino configuration, implying a top-to-the-continent movement and a simple shear deformation of the whole continental crust. We suggest that the flexed necking domain could be home to fractured reservoir providing that it is effectively sealed by post-rift sequences.
Impact of SLR long-term mean range biases on the orbits of altimetry and SLR satellites for ITRS2020 realizations
Authors: Rudenko Sergei , Bloßfeld Mathis , Zeitlhöfler Julian , Kehm Alexander , Dettmering Denise
Published: February 2023

In 2022-2023, new (2020) realizations of the International Terrestrial Reference System (ITRS) were published, namely ITRF2020, DTRF2020, and JTRF2020. One of the differences for these realizations with respect to the previous (2014) ones is the application of Satellite Laser Ranging (SLR) station-specific long-term mean range biases for the four geodetic satellites LAGEOS-1, -2 and Etalon-1 and -2. These range biases were subtracted at the observation level from the SLR observations used to derive the ITRS2020 realizations. In this context, a question arises if these range biases should be applied in SLR-observation-based precise orbit determination for any satellite to obtain the highest orbit quality possible, when using ITRS2020 realizations as the a priori reference frame. We present results of a study on the application of the SLR long-term mean range biases derived from LAGEOS-1, -2 and Etalon-1 and -2 for precise orbit determination of some altimetry and other spherical SLR satellites using ITRS2020 realizations as the a priori reference frame and make a conclusion on the necessity of application of these biases. Furthermore, we present results of precise orbit determination for altimetry satellites based on long-term mean range biases explicitly determined for the respective satellites.
Interactions Between Salt Tectonics and Crustal Tectonics in The Mediterranean
Authors: Gaullier Virginie , Travan Gaia
Published: February 2023

The deposition during the Messinian Salinity Crisis (MSC, 5.96 – 5.33 My) of a thick layer of evaporites and especially of a mobile halite unit has deeply inﬂuenced the architecture and evolution of the Mediterranean margins. The Mediterranean has characteristics that set it apart from most “classic” salt-bearing basins, where salt was deposited after (or right after) the rifting stage. Conversely, in the Mediterranean, salt was not related to a rifting event and it covers vast areas that are geodynamically active presently. These include regions of divergence (Tyrrhenian Sea), young or mature convergence (Algerian and Ligurian Margins, Ionian Sea, Mediterranean Ridge), oblique convergence (Eastern Cyprus Arc), and strike-slip (Levant Basin). Despite the progress in seismic processing, the strong acoustic impedance contrast between salt and sediments prevents an accurate seismic imaging of the sub-salt deep structures. Second, the evaporites act as a decoupling layer (thin-skinned tectonics) preventing the propagation of the crustal structures towards the surface. Last, when crustal tectonics generates horizontal and vertical movements in the basement, these movements can trigger a gravitational response in the salt and its overburden, thereby blurring the deeper tectonic signal. In order to bypass these difﬁculties, we propose to use salt tectonics as a proxy to better constrain these deep structures both in terms of geometry and timing. Furthermore, the comparison between natural examples (seismic data) with analogue modelling allows a better understanding of the margins’ structure and evolution. We present here a synthesis of several Mediterranean study cases in different geodynamical settings (convergence, divergence, strike-slip). The complexity and variety of its margins, along with the presence of a widely distributed Messinian salt décollement, make the Mediterranean the perfect area to analyze salt deformation and its relationships with different tectonic styles, including the effects of crustal structures.
Modeling post-fire regeneration patterns under different restoration scenarios to improve forest recovery in degraded ecosystems
Authors: Mantero Giulia , Anselmetto Nicolò , Morresi Donato , Meloni Fabio , Bolzon Paola , Lingua Emanuele , Garbarino Matteo , Marzano Raffaella
Published: February 2023

Applied nucleation (AN) is a nature-based solution alternative to traditional regular plantations. It is a cost-effective technique that integrates artificial seedlings and natural regeneration dynamics to enhance forest recovery, mimicking successional processes. Given the current shift of disturbance regimes caused by global change, this technique will likely be a valuable active restoration approach for many forest ecosystems affected by extreme disturbance events. Indeed, AN is suitable for ecological restoration after stand-replacing events, improving seed availability and microsite conditions supporting natural regeneration. AN has been mostly applied in tropical forests, but its use in Mediterranean forests should be increasingly considered since a higher occurrence of large and severe fires has been observed over the last decades and further increases are expected in the future. These changes are raising concerns about regeneration recruitment, particularly for obligate seeders in mountain ecosystems. In these ecosystems, it is crucial to reconsider current post-fire policies to identify strategies that promote and maintain the ecosystem services of degraded forests, particularly when natural regeneration is ineffective. The main aim of this study was to define the best methodology for implementing AN in a mountain area affected by a large stand-replacing fire that occurred in 2005 in the Aosta Valley Region (North-Western Italy). After the fire salvage logging was performed, increasing ecosystem degradation, and, 16 years later, natural regeneration is still scarce and struggling to settle. Hotspots for AN were identified based on post-fire natural regeneration response to a series of site characteristics, such as topography, fire severity, and distance from seed trees. We assessed the drivers of post-fire regeneration through a machine learning correlative model (Bayesian Regression Tree, BART). The probability of regeneration presence across the landscape was then predicted under the current situation and a set of AN scenarios. Starting from the current scenario, we reclassified the prediction raster into three levels, according to the probability of presence and uncertainty. Polygons with low uncertainty and probability (< 0.3) were included in level one and considered hotspots for AN. From these predictions, it was possible to assess the most efficient active management scenario to speed up the regeneration process. Our results showed that AN could be a promising post-fire management technique for promoting natural regeneration while limiting anthropic interventions and their related economic and ecological costs.  
Impact of contemporary ocean stratification on the global tides: A preliminary modeling study
Authors: Opel Lana , Schindelegger Michael , Ray Richard D.
Published: February 2023

Low-frequency non-astronomical changes of ocean tides of (1 cm) have been documented in water level measurements around the globe, but their causative mechanisms remain poorly understood in many cases. While anthropogenic developments (e.g., harbor dredging) are certainly a leading factor at individual sites, the spatially coherent tidal variability seen in areas with distributed tide gauge information is revealing of natural processes. Here we use a general circulation model, configured on a 1/12° horizontal grid, to spatially map the influence of ocean stratification changes on the global M2 tide from 1993 to 2019. We partition the problem into separate yearly simulations of short duration (40 days) and relax each forward integration to the year’s “true” stratification, as provided by an eddying ocean reanalysis. The simulations reveal typical stratification-driven M2 amplitude changes of 0.5 cm on interannual time scales, as calculated at positions of 40 coastal tide gauges in three particular regions (New Zealand & Australia, Florida & Gulf of Mexico, Northeast Pacific). Most of the identified fluctuations at the coast are present in the barotropic tidal component, suggesting an origin in changing tidal conversion at remote topography or turbulent energy dissipation in shallow water. In addition, we fit linear rates to the yearly M2 solutions over the 1993–2019 time span and compare the resulting in-phase and quadrature trends to a novel (but still tentative) estimate of M2 trends in the open ocean from TOPEX-Jason satellite altimetry. The two solutions bear gross resemblance to each other and indicate large spatial-scale trends of ~1 cm cy-1 in the barotropic M2 tide in the Indian Ocean, the western and northern Pacific (e.g., in the Gulf of Alaska), and Baffin Bay. Our results highlight that efforts seeking to explain interannual to secular changes of tides at the coast and in the open ocean must consider both sea level rise and contemporary changes in ocean stratification.
Using super-residual heat transport to elucidate ocean heat storage in a resolution hierarchy of models
Authors: Lee Jiheun , Kuhlbrodt Till , Tailleux Remi , Storkey Dave
Published: February 2023

The large spread in projections of ocean heat uptake found in CMIP simulations is known to be problematic, leading to large uncertainties in the projected future ocean heat storage. This study introduces a new diagnostic, super-residual transport (SRT), to trace ocean heat uptake processes consistently in different models. SRT is the contribution to ocean heat uptake associated with residual mean advection and isopycnal diffusion, and therefore explains large and mesoscale heat transports in terms of spatial scale regardless of model resolution. We compare two different resolutions (eddy-parameterising and eddy-present models) of the global coupled HadGEM3-GC3.1 models to investigate performance of ocean heat uptake simulation and suggest where focus should be applied in model development.We find that high-latitude regions show substantial inter-resolution differences in SRT of the mean state. Due to strong along-isopycnal heat uptake poleward of 50°S, a large amount of heat is stored in the Southern Ocean with little sea surface warming. The ocean heat uptake in the mixed layer is stronger and deeper near Drake passage in the eddy-present model which has steeper isopycnal surfaces of the Southern Ocean. The deep ocean warming varies with model resolution due to different properties of deep water formation in Weddell Sea and North Atlantic, which provides different paths from the surface to the bottom of the ocean. We demonstrate that mesoscale eddy advection due to baroclinic instability, implemented by Gent-McWilliams parameterisation, is key to understanding the differences in warming Antarctic Bottom Water and North Atlantic Deep Water across resolutions.In the context of CO2-forced change, SRT shows much higher similarity across model resolutions than in the mean state. For both model resolutions, the mixed layer warming driven by SRT is much reduced in the high-latitude Southern Ocean. This results mainly from slumping of isopycnals, which brings excessive heat further northward of 50°S and then downward by enhanced Deacon cell. Consistent with our findings in the mean state, deep ocean warming penetrated to the bottom of the Southern Ocean is only observed in the eddy-present model. An important implication of this result is that better agreement across model resolutions in AMOC strength and North Atlantic warming is achieved in CO2-induced SRT. This suggests that whether ocean mesoscale is explicitly resolved or parameterised becomes less influential with respect to the patterns of ocean warming as the climate warms, which results from abrupt changes in mean circulation and reduced effect of Gent-McWilliams parameterisation.
Sensitivity study of the PALM model system to different driving conditions
Authors: Radovic Jelena , Belda Michal , Resler Jaroslav , Krč Pavel , Eben Kryštof , Bureš Martin , Geletič Jan
Published: February 2023

The LES-based PALM model system 6.0 is a state-of-the-art atmospheric numerical model widely used among scientists for urban boundary layer and urban climate studies. Despite being subjected to many validation and sensitivity studies which tested the model’s accuracy and applicability to urban environments, a major step is needed to test its sensitivity to different driving conditions.In this study, we performed a series of PALM model simulations for a given domain and two selected episodes during the year 2019. Each simulation lasts 72 h, and all of them were performed for an 8 km x 8 km domain in 10 m resolution encompassing a real built-up residential area in the southeast part of the city of Prague, Czech Republic. The simulation setups are identical apart from  the initial and boundary conditions imposed. For that purpose we utilized the mesoscale WRF model and created an ensemble consisting of several members with different parameterization schemes.This study's findings are serving to better understand how different initial and boundary conditions affect the PALM model simulations. In addition, we present the process, complexity, and challenges one can encounter while trying to find the optimal set of initial and boundary conditions for a given PALM model simulation. Moreover, the performed simulations have shown that most of the variance in the ensemble comes from the driving conditions. 
Development of forecasting rainfall accuracy correction method based on observation scenario
Authors: Yoon Jungsoo , Hwang Seokhwan , Kang Narae
Published: February 2023

Numerical weather prediction (NWP) provided by the Korea Meteorological Administration (KMA) has rainfall predictions such as typhoons, so it simulates the time point relatively well, but the rainfall intensity of heavy rain, such as the peak of precipitation, is inaccurate to use for flood forecasting. Various methods have been tried for peak smoothing or under-estimation limits due to limitations due to the temporal and spatial scale of the prediction field, but a solution that can be used in practice has not been found. In order to solve this problem, this study developed a technique for correcting the temporal distribution of meteorological forecast data using the representative temporal distribution extracted based on a large amount of past observation data. In order to solve the peak smoothing problem of numerical forecasting, after merging radar quantative precipitation forecasting (QPF) and NWP, the abnormal distribution of precipitation around the peak was corrected using the standard time distribution based on observation data. As a result of correction for typhoon Hinnamno attack in 2022, the accuracy was improved from 68% of the actual rainfall before correction to 85% due to improvement in the peak. Acknowledgement : This research was supported by a grant(2022-MOIS61-002) of ‘Development Risk Prediction Technology of Storm and Flood for Climate Change based on Artificial Intelligence’ funded by Ministry of Interior and Safety(MOIS, Korea). 
Are soil quality indicators good predictors for agricultural yield?
Authors: Overturf Emily , Seidel Felix , Schneider Florian , Don Axel
Published: February 2023

Soil quality scoring is a useful tool in land management as it can help determine the most suitable land use and is used to estimate the value of land for agricultural or forestry production. In agriculture, soil scoring can also help to inform management practices such as fertilizer application and irrigation rates, or even determine taxation levels as is the case in Germany. Various indicator-based soil scoring systems exist, and are often claimed to be linked to crop yield potential as an important ecosystem service.  In Germany, a system more than 100 years old called the Bodenschätzung is still used today and provides the most detailed soil information system for agricultural land across Germany. Calculating the Bodenzahl (soil score) with this method requires expert knowledge, is only applicable to German soils and does not consider climate variables such as mean annual temperature and precipitation. The Müncheberg Soil Quality Rating (MSQR) is an emerging method developed in Germany in 2007 which attempts to make yield potential scoring simpler, more widely applicable and more accurate. This system claims to be usable without extensive training and was suggested to be globally applicable by some previous studies. It also considers climate variables such as drought risk and soil temperature regime that may allow for more accurate yield predictions than soil-only methods like the Bodenzahl. However, there is little evaluation on the relation between soil quality indicators and yield. Therefore, we tested the implementation of the MSQR system and calculated MSQR scores for 3104 sampling points from the first German Agricultural Soil Inventory following the MSQR guide. In addition, we tested the performance of the Bodenschätzung with the Bodenzahl for the sampling points and related these soil quality indicators with 10 years of point specific yield data from our data set.  Preliminary findings suggest that the MSQR may determine yield potential and yield stability better than the Bodenschätzung, likely due to the fact that climate variables are considered. However, MSQR parameters may need to be adjusted locally for the method to accurately predict yields in different regions, which makes a global application of the method more complex. In general, soil indicators seem to predict only part of agricultural yield at national scale with management practices and climate still playing important roles.
Variability of compound drought and heatwave events over the Mediterranean and their large-scale atmospheric circulation drivers
Authors: Cartalis Constantinos , Philippopoulos Kostas , Agathangelidis Ilias , Polydoros Anastasios , Mavrakou Thalia
Published: February 2023

Current research has shown that extreme events can be interrelated and can trigger cascading impacts. Traditional climate risk and impact assessments typically consider a single extreme event, a fact that leads to the underestimation of risks, as such events are often interdependent. This work will address the field of extreme climate and weather through the assessment of compound drought and heatwave (CDHW) events. The principal aim of this study is to evaluate the current state of climate over the Mediterranean in terms of droughts and heatwaves, focusing on their compound effects, and identifying their large-scale atmospheric circulation drivers. The identification of the CDHW climatology is carried out through the improvement of a novel index tailored to the Mediterranean region. Multiple combinations are examined according to the generic definition of CDHW events (i.e., heatwaves that occur during the period of drought events) and an optimum compound index is developed that successfully quantifies the interrelations of droughts and heatwaves. Extensive statistical analysis is carried out to evaluate their frequency, duration, intensity, and trends. The analysis is based on the high-resolution state-of-the-art ERA5-Land reanalysis product at a 0.1° x 0.1° horizontal resolution. Following a data-driven methodology, the role of large-scale atmospheric circulation drivers on the onset, duration, and intensity of the CDHW events is examined using the synoptic climatology approach. The ‘environment-to-circulation’ approach is selected that employs the Self-Organizing Map (SOM) artificial neural networks for clustering and mapping the atmospheric circulation for enabling the understanding of the large-scale drivers responsible for CDHW events. The analysis provides the hot-spot regions of CDHW high-impact phenomena over the Mediterranean region and their association with large-scale circulation is established.
Detection of soil compaction by the spatial analysis of vegetation characteristics via UAV and clustering algorithms
Authors: Lindenstruth Frauke , Kuhwald Michael , Augstin Katja , Duttmann Rainer
Published: February 2023

Soil compaction due to field traffic can reduce yields and increase a fields susceptibility to surface runoff and soil erosion. However, detecting and monitoring compacted soils is time and labor intensive. Additionally, most detection methods focus on few points within a field and usually do not provide information on the spatial distribution of soil compaction and its effects on a field scale. In this study, we aim to present a method for detecting potentially compacted areas on field scale using an unpiloted aerial vehicle (UAV). Using an UAV enable the non-inversive collection of field vegetation patterns want, which can be linked to differences in soil properties and soil structure.In two study regions, we monitored six fields for four years. For each field, at least four UAV-flights were carried out per season. The UAV was equipped with a RGB and a multispectral sensor. Spatial corrections and spectral calibrations were performed with ground control points and calibration targets. To analyze the data for patterns in the vegetation, models of plant height and various vegetation indices (NDVI, SAVI, WDRVI, EVI) were calculated and combined with three different clustering algorithms (k-means, fuzzy k-means, CLARA). To validate the identified vegetation patterns, several field campaigns were conducted to analyze soil texture, saturated hydraulic conductivity, air permeability, bulk density, and yield. Our study shows that patterns in the vegetation can be distinguished by their geometry and orientation. Linear patterns running parallel to the tramlines and planar patterns in the headland indicate potential compaction, whereas rounded patterns are indicators for topography changes. Soil samples within the detected linear patterns overall showed an increase in bulk density, and a decrease in saturated hydraulic conductivity and air permeability. Yield samples were also reduced in those patterns for all studied crops. Thus, we can conclude that UAV analysis is suitable method for soil compaction detection. However, detected patterns can be overlaid by other causes.
Relevance of using ensemble forecasts of flash-flood impacts for an emergency service: an evaluation for the October 2018 flood event in the Aude river basin, France
Authors: Charpentier-Noyer Maryse , Nicolle Pierre , Payrastre Olivier , Gaume Eric , Bouttier François , Marchal Hugo
Published: February 2023

Flash floods (FF) represent an important part of the flood damages and fatalities in the world. Today, operational FF nowcasting and warning systems are often based on the use of precipitation weather radars, and therefore still offer limited anticipation. They also generally rather represent the intensity of the flood events than their severity in terms of impacts, which may limit the capacity of emergency services to take relevant decisions.This contribution aims at evaluating the value of a new ensemble FF impacts forecasting chain for the decision making of an emergency service.  The case study corresponds to the Aude River flash floods that occurred on October 15 and 16, 2018, and which are among the most important FF observed in southeastern France in the recent years. This event is responsible for the death of 15 people (99 people injured), as well as particularly large material damages.The tested FF impacts forecasting chain combines three new rainfall ensemble forecast products (provided by CNRM), specifically designed for short-range forecasting (0-6h), and a highly distributed rainfall-runoff model (Charpentier-Noyer et al., 2022). A simple impacts model is built and applied for each river reach based on a catalog of 8 inundation scenarios corresponding to return periods of 2 to 1000 years. The impacts are represented in terms of a number of inundated buildings.The value of the ensemble impacts forecasts is finally evaluated based on the implementation of a multi-agent model, for the simulation of the field decisions taken by an emergency service. This new evaluation approach, based on simple but realistic hypotheses, allows to illustrate and measure the gains associated with a better anticipation of impacts, and the costs associated with false alarms, which lead to the unnecessary mobilization of rescue teams, to the detriment of really impacted locations. In case of extremely limited means for safety operations (low number of rescue teams), the decisions based on a naive zero future rainfall scenario may sometimes appear better than those using ensemble rainfall forecasts. Nevertheless, in all the simulated cases, the decisions taken from the ensemble rainfall forecasts appear more efficient than those based only on field observations.  Charpentier-Noyer, M., Peredo, D., Fleury, A., Marchal, H., Bouttier, F., Gaume, E., Nicolle, P., Payrastre, O., and Ramos, M.-H.: A methodological framework for the evaluation of short-range flash-flood hydrometeorological forecasts at the event scale, Nat. Hazards Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/nhess-2022-182, in review, 2022.
Strategies for Climate Smart Water Management in Awash River basin, Ethiopia
Authors: Taye Meron Teferi , Tekleab Sirak , Geressu Robel Tilaye , Alemu Muluken , Seid Abdulkarim
Published: February 2023

Awash River is the most utilized river basin in Ethiopia. The basin has a total of 110,000 km2. The water resources are exploited for various competing needs; domestic, agriculture, livestock's, energy, industry and environment. This study is aimed at enhancing the existing water resources management practices to make them climate resilient in light of climate variability and change. Frequent rainfall extremes, floods and droughts, an imbalance in water availability and demand, water over use in irrigated fields, water use competition and water quality deterioration are the key water management challenges of the basin. Small scale food producers reliant on rain-fed agriculture, small scale irrigators, pastoral and semi-pastoral communities are vulnerable to climate variability and experiencing its impact already. This study identified that their livelihoods are being impacted due to rainfall failure to produce adequate production in the growing period and shortage of fodder for their cattle due to limited soil moisture availability. Based on the identified problems and the existing water management practices, this study developed a conceptual framework, that encompass Climate Smart Water Management (CS-WM) definitions, CS-WM strategies, actions and recommendations to enhance the existing practices on multiple spatial scales. The proposed strategies briefly include improving data and information for more adaptive water resources planning and management, raising awareness and community engagement for improved water management; enhancing effectiveness of water management via technology and innovations, and enhancing alternative clean energy sources to support economic development while minimizing negative consequences of climate variability and change. The strategies and recommendations proposed are tailored to site specific locations and based on societal needs that could solve the identified water management problems and manage tradeoffs among different sectors in the basin.
Enhancing decision making tools for climate-smart water management in the Awash Basin, Ethiopia.
Authors: Seid Abdulkarim , Geressu Robel , Tekleab Sirak , Alemu Muluken , Taye Meron Teferi
Published: February 2023

Decision analysis techniques to meet water systems management challenges under climate change uncertainty have improved with advances in computational technology in the last decades. Infusing improved design and decision analysis techniques in developing countries can be of paramount importance given their higher vulnerability to climate change, fewer professionals with sufficient capacity, and generally high incentive for rapid expansion of low-cost solutions.  However, a large gap exists between scientific progress and practical and policy applications, especially in global south countries. In this paper we discuss the observed challenges in design, analysis and decision making process to achieve climate smart water management in the highly utilized Awash Basin of Ethiopia. The approach we followed is key-informant interviews with water professionals working across multiple disciplines (i.e., water supply, irrigation, hydropower infrastructure design) and working for different organizations (i.e., government ministries, research institutions, consultancy offices) and freelancers and academicians. Efforts were made to represent informants from different academic levels, gender, and professional responsibilities. The results demonstrate multiple but related challenges including the lack of incentive to apply changes at individual or institutional levels, cultural and policy inertia against transparency and public debate in decision making. Technical challenges emanate from the non-inclusion of up-to-date climate change science at higher education level along with lack of access to computational and communication technology. We present tailor made decision support tools to improve management by leveraging advances in computational and visualization of large data to reveal tradeoffs and synergies of water and food systems at multiple watershed scales.  Efficient and timely solutions for vulnerable small-scale producers can be best achieved by changing the role of institutions to reflect local capacity in the water system management sector.  Proposed solutions to help tackle these challenges include overhaul of the skill requirement for water resources professionals along with continuous skills training and evaluation.
Metagenomes reveal purple non-sulfur bacteria linked to bare ice habitats on the Greenland Ice Sheet
Authors: Keuschnig Christoph , Trivedi Christopher B. , Feord Helen , Mourot Rey , Zervas Athanasios , Bolander Marie , Sipes Katie , Perini Laura , Tranter Martyn , Anesio Alexandre M. , Benning Liane G.
Published: February 2023

Phototrophic organisms blooming during the summer melt season on snow and ice surfaces are dominated by eukaryotic green algae (Chlorophytes and Streptophytes, respectively), with Cyanobacteria restricted to cryoconite habitats. However, the role and interactions between the algae and other light-harvesting organisms are largely understudied in these ecosystems.We searched metagenomes of snow and ice samples collected from the Greenland Ice Sheet during the summer melting season for signatures indicating anoxygenic photosystems, which are used by certain groups of bacteria to gain energy from light without releasing oxygen. Two metagenome assembled genomes (MAGs) carrying all genes necessary to perform anoxygenic photosynthesis and carbon-fixation were found. Whole-genome phylogenetic comparison placed the MAGs within the Alpha- and Gamma-proteobacteria, which was confirmed by alignment of the respective functional marker genes pufL and pufM to known sequences from cultured anoxygenic phototrophic bacteria. The identified functions and phylogeny suggest that the MAGs belong within the group of purple non-sulfur bacteria, a pigmented and metabolically versatile group of bacteria often found in shallow aqueous environments, but very little is documented in cryogenic environments. Our data show that these procaryotic organisms are preferably linked to glacial ice algae habitats and, to a lesser extent, to algae in snow habitats. Our results pose intriguing ecological questions for supraglacial habitats, such as the contribution of these procaryotes to the ongoing biological darkening of ice surfaces or the potential mutualistic light-harvesting strategies on ice, as the used wavelength of purple non-sulfur bacteria are complementary to those used by indigenous high abundant glacial ice algae.
A low cost multi-chamber system (“Greenhouse Coffins”) to monitor CO2 and ET fluxes under semi-controlled conditions: Design and first results
Authors: Hoffmann Mathias , Al Hamwi Wael , Lück Matthias , Schmidt Marten , Dubbert Maren
Published: February 2023

Determining greenhouse gas (GHG) fluxes, water (ET) fluxes and their interconnectivity within the soil-plant-atmosphere-intersphere is crucial, not only when aiming to find solutions for current agricultural systems to mitigate the global climate crises but also to adapt them to related challenges ahead, such as more frequent and severe droughts. In a first attempt for a better understanding, often laboratory and/or greenhouse pot experiments are performed, during which gas exchange is predominately measured using especially manual closed chamber systems. Commercially available systems to determine gas exchange in terms of CO2 and ET are, however, costly and measurements itself labour-intensive. This limits the amounts of variables to be studied as well as possible repetitions during a study. Additionally, it resulted in the long-term focus on agroecosystems of the northern hemisphere while agroecosystems of sub-Saharan Africa as well as Southeast Asia are still being underrepresented.We present an inexpensive (<1.000 Euro), Arduino based, multi-chamber system to semi-automatically measure 1) CO2 and 2.) ET fluxes. The systems consists of multiple, self-sufficient, closet-shaped PVC “coffins”. The “coffins” a closed by a frontal door and periodically ventilated through a sliding window. Relays connected to the microcontroller are used to steer closure/opening (linear actuator) and ventilation (axial fans). CO2 and ET fluxes are determined through the respective concentration increase during closure by a low-cost NDIR CO­2 (K30FR; 0-10,000 ppm, ± 30 ppm accuracy) and rH sensor (SHT-41). Parallel measurements of relevant environmental parameters inside and outside the “coffins” are conducted by DS18B20 (temperature) and BMP280 (air pressure) sensors. Sensor control, data visualization and storage, as well as steering closure/opening and ventilation is implemented in terms of a wifi and bluetooth enabled, socket powered (9V), compact microcontroller (D1 RS32) based logger unit. Here, we present the design, and first results of the developed, low-cost multi-chamber system. Results were validated against results of customized CO2 and ET measurement systems using regular scientific sensors (LI-COR 850) and data logger components (CR1000), connected to each “coffin” by a multiplexer.  Flow-meter were used for measurement synchronization.
Comparison of emission factors of particles from shipping using different equipment
Authors: van Dinther Daniëlle , Weigelt Andreas , Beecken Jörg , Mellqvist Johan , Conde Jacobo Vladimir , Blom Marcus , Duyzer Jan
Published: February 2023

Air quality in urban cities with ports can significantly be impacted by shipping. For example Visschedijk and Denier van der Gon (2022) showed that, within Rotterdam area (the Netherlands), sea shipping is the main source of ultra-fine particles (UFP) with a contribution of 56% to total UFP emissions. Within EU-project SCIPPER (Shipping Contributions to Inland Pollution Push for the Enforcement of Regulations) a measurement campaign of six weeks was undertaken at the river Elbe near Hamburg (Germany). Sea going vessels pass by on the way to or from the port of Hamburg, which is located about 10 km upstream of the measurement site. Three different groups measured side-by side different gaseous compounds and aerosols on-shore. The aerosol measurements consisted of different equipment measuring different sizes ranging from 6 to 10 000 nm, also black carbon was measured by two groups. The emission factors (EF) of the different ships were calculated in #/kg fuel as well as mg/kg fuel from these measurements. This provides a unique dataset to better understand the emission characteristics of different ships as well as the comparability of different devices. This comparability is important if in the future legislation to decrease aerosol emissions of shipping is applied and needs to be verified. Results showed the relatively large contribution of mainly ultrafine particles, with 90% of the total amount of particles being smaller 80 nm and 75% of the total particle mass comes from particles smaller 200 nm. The comparison showed very promising results when the same equipment was tested side-by-side (R2 above 0.85 for all size ranges). The comparability of EFs of same sources that were measured by different devices was somewhat lower, but especially for smaller size ranges still promising (R2 of 0.69 for particle number ranging from 90 to 300 nm). For black carbon the experimental set-up proved to be too different (drying vs non-drying and different inlet cut-offs) to give comparable emission factors. Concluding the data showed promising results to be able to use on-shore monitoring in the future to monitor aerosol ship emissions, also when using different equipment.References:Visschedijk, A., Denier van der Gon, H. (2022). UFP emissie in de Rijnmond regio in 2019 (in Dutch). Utrecht: TNO-report R10616.
Particle-in-Cell simulations of the electron-deficit instability in the solar wind
Authors: Micera Alfredo , Verscharen Daniel , Boella Elisabetta , Innocenti Maria Elena , Coburn Jesse
Published: February 2023

An ambipolar electric field is expected to develop in the solar wind, to maintain quasineutrality between the ions and electrons, which, due to their smaller mass, have a higher mobility than ions (Pierrard and Lemaire, 1996; Maksimovic et al., 2001). An electron deficit in the sunwards direction associated with this electric potential has recently been observed in the near-Sun solar wind by Parker Solar Probe (Berčič et al., 2021a; Halekas et al., 2021).
In this work, we use fully kinetic Particle-in-Cell (PIC) simulations, performed using the Energy Conserving Semi-Implicit Method (ECSIM, Lapenta 2017) to investigate whether this electron deficit may act as a source of whistler waves.
We start from an electron velocity distribution function (VDF) modelled after those observed in the inner heliosphere, and prove that the sunward electron deficit drives a kinetic instability and generates whistler waves that propagate quasi-parallel to the background magnetic field. These waves interact with the electron VDF and are able to scatter, through resonant interactions, the electrons near the cut-off towards smaller values of perpendicular velocities and larger absolute values of parallel velocities. Consequently, the sunward electron deficit is filled as the instability evolves. As this initial deviation from thermodynamic equilibrium is reduced a decrease in the electron heat flux occurs. The properties of the instability are closely related to the position of the cut-off in the distribution.
The results of our PIC simulations confirm recent Solar Orbiter (SO) observations (Berčič et al., 2021b) that showed a consistent correlation between parallel whistler wave detection and the presence of the sunward deficit in the electron VDF.
Constraining ocean dynamic sea level projections along the coast of the Netherlands
Authors: Le Bars Dewi , Keizer Iris , Jesse Franka , Drijfhout Sybren
Published: February 2023

Ocean dynamic sea level (ODSL) is the local height of the sea surface above the geoid. It is computed by atmosphere-ocean coupled general circulation models from the coupled model intercomparison projects (CMIP). In many places it is one of the most important components of sea level projections for the coming century. However, because it depends on climate dynamics, there is a low agreement between climate models. Moreover, the difficulty to estimate ODSL from observations has resulted in IPCC AR5 and AR6 sea level projections using CMIP5 and CMIP6 outputs without model selection nor bias correction. We use multiple lines of evidence to constrain ODSL along the coast of the Netherlands: ocean reanalyzes, sea-level budget closure using tide gauges and satellite altimetry observations, and direct integration of steric sea level change from observed temperature and salinity together with an estimation of wind influence on sea level. We find that CMIP6 overestimates ODSL change along the Dutch coast and that this overestimation is not only related to the overestimation of global mean temperature increase. Based on the emergent constraint framework, we provide improved ODSL projections with reduced uncertainty and an increased level of confidence.
Modelling the impacts of ice damage on the response of Thwaites Glacier, West Antarctica
Authors: Li Yanjun , Navarro Javier Blasco , Pattyn Frank , Qiao Gang
Published: February 2023

Ice shelves around the coastal portion of the Antarctic ice sheet are sensitive indicators of climate change. The thinning of ice shelves diminishes buttressing, promotes longitudinal spreading, and increases ice flux across the grounding line, leading to accelerated glacier discharge into the ocean. Thwaites Glacier in the Amundsen Sea Embayment is one of the fastest-changing outlet glaciers in Antarctica. Damaged areas with densely distributed crevasses and open fractures on Thwaites Glacier are key to future ice shelf stability, grounding line retreat and sea level contribution. The damage feedback processes should be taken into consideration when simulating the evolution of Thwaites Glacier using ice sheet models.Here, we add the continuum damage mechanics approach to the F.ETISh/Kori ice flow model, to simulate the present-day and near future behavior of the ice sheet and ice shelf system, including brittle ice physics. The damage field is described by equating it to the total crevasse depths used in Nick et al. (2010) and Sun et al. (2017). 100 years simulations under present-day climate conditions with and without damage in different scenarios have been conducted, and the change in ice velocity, ice thickness, the grounding line retreat and the sea level contribution of Thwaites Glacier have been analysed. Moreover, the change in ice velocity along four ice flow profiles in the first 20-year simulation has been analysed and the impact of damage on velocity has been assessed by comparing the simulated velocity fields with the observations (e.g., the MEaSUREs and ITS_LIVE ice velocity products).Results indicate that damage drastically increases the ice velocity over the ice shelves and weakens them as such that grounding line retreat ~18 km after 20 years, accelerates (~1.5 times) compared to the observed increase in flow speed and contributes around an order of magnitude to the sea level rise in 50 years. Change in ice velocity profiles of Thwaites Glacier also show that local damage may overestimate ice velocity, especially in the grounded ice near the grounding line, while it underestimates observed ice flow when local damage is omitted. Through a series of further sensitivity experiments, an analysis on the timing and magnitude of damage has been carried out to gauge the current and near future state of the Thwaites glacier basin. 
SOL2022-03-30 X1.4 GOES Class Flare: Localising the source of quasi periodic pulsations in the Hard X-ray and microwave emissions with STIX onboard Solar Orbiter and EOVSA.
Authors: Collier Hannah , Hayes Laura , Battaglia Andrea , Harra Louise , Krucker Säm
Published: February 2023

In this work the analysis of the SOL2022-03-30 X1.4 GOES class flare is presented. This flare was observed by Solar Orbiter during perihelion as well as from Earth based observatories including SDO’s AIA and the Extended Owens Valley Solar Array (EOVSA). It displays well correlated fast time variation in the HXR and microwave wavelengths of emission with time dependent lags. The mechanism behind such observed puslations is not yet fully understood and is important for gaining an understanding of particle acceleration and energy release in solar flares. In this flare, the oscillatory behaviour grows in time and can be split into three phases with QPP periods ~7s, ~14s and ~35s. New capabilities from Solar Orbiter’s Spectrometer Telescope for Imaging X-rays (STIX) allows for the localisation of individual bursts on short timescales which enables us to determine the spatial morphology of the HXR emission and its evolution in time. The HXR source locations are compared with the microwave sources observed by EOVSA and the ribbon structure determined from AIA 1600Å and 1700Å. The QPP source locations are found to change significantly in time. Furthermore, the electron spectral index is anti-correlated with the observed HXR emission, obeying the soft-hard-soft relation. When combined, these observations point towards a mechanism for QPP generation which involves quasi-periodic energy release and injection of electrons into the flaring loop. However, several open questions remain about how these QPPs are generated.  