bluuebunny/crossref_metadata_2025 huggingface dataset:
Arctic temperature persistence in winter and spring and seasonal forecasting
Authors: Ólafsson Haraldur , Ekrami Negar
Published: March 2024

Persistence is a natural first approximation or a baseline to seasonal temperature forecasting.  In the present study, winter and spring persistence in mean montly temperatures in the circumpolar Arctic is explored in long time-series of monthly mean data for the winter and spring seasons.Locally, very high temporal correlations, as well as significant negative correlations are detectedPhysically, the persistence may be traced to snow cover and sea-ice extent.  The variability in these factors may contribute directly to seasonal variability in the radiation budget as well as in surface fluxes, but there are also indirect, but detectable impacts upon regional circulation patterns.
Raising a peat meadow’s groundwater level: fertilizer strategies to minimize N2O emissions
Authors: Blondeau Erne , Westerik Dorien , Velthof Gerard , Heinen Marius , van Groenigen Jan Willem
Published: March 2024

Peat soils store a large part of the global soil carbon stock, which can potentially be lost when they are drained and taken into cultivation. In the Netherlands, 75% of the peat and peaty soils are drained and are mainly used for grassland cultivation. This results in an estimated yearly emission of 5.6 Mton CO2 due to peat oxidation, accounting for about 3% of the national CO2 emissions. Groundwater level (GWL) management has been proposed to mitigate peat soil oxidation, but this may lead to increased emissions of nitrous oxide (N2O). Peat meadows experiencing (intermediate) wet conditions, and frequent fertilization events, are favorable locations for N2O production.We hypothesize that the selection of a fertilizer with a relatively low mineral nitrogen (N) content (such as farmyard manure), will limit the risk for increased N2O emissions as a result of raising the GWL, compared to fertilizers with a high mineral N content (such as calcium ammonium nitrate). The effects of these two management factors (groundwater level and fertilizer type) were studied in a two-year field experiment. The experiment took place in 2022 and 2023, on two adjacent grassland fields of a dairy farm near Zegveld, in the low-lying western peat area in the Netherlands. On the first field, drainage was controlled by the ditch water levels, leading to GWLs ranging between -100 cm in the summer and -20 cm in the winter. The GWL of the second field was maintained at a more steady level around -40 cm using infiltration drainage pipes. In year two, a third groundwater level treatment was added, with infiltration drainage aimed at a GWL of -20 cm. Following a randomized block design for each GWL object, the N2O emissions and N yields were compared for six fertilizer products and an unfertilized control treatment in four replicates: calcium ammonium nitrate, ammonium sulphate, farmyard manure, cattle slurry and the liquid and solid fraction products after slurry separation. The results of 2022 suggested that the combination of raising the GWL (using infiltration drains aimed at -40 cm) and application of cattle slurry or its liquid fractionation product - both having a relatively high mineral N content - led to a strong increase in N2O emissions. As expected, emissions were lowest for farmyard manure and the solid fraction of slurry. However, these fertilizers in combination with a raised GWL resulted in significantly lower N yield in the harvested grass, making the combination less attractive to a dairy farmer. Variation in N2O emissions was still large, indicating the importance of several measurement years. Here, we will present the combined results of 2022 and 2023, including fertilizer-specific N2O emission factors calculated over two years.
Low clouds over the subtropical Indian Ocean in the Mascarene High environment and sub-seasonal circulation associations with the Indian summer monsoon
Authors: Tamilselvam Gokul , Vellore Ramesh , Choudhury Ayantika Dey , Viswanath Divya , Raghavan Krishnan , Kooran Reji Mariya Joy
Published: March 2024

This study investigates anomalous low cloud fractions (LCFs) in the Mascarene High(MH) environment of subtropical Indian Ocean (SIO) during June-September, and their sub-seasonal (10-90 day) circulation changes in the SIO and associated variations of the Indian summer monsoon (ISM) using observations and ERA5 circulation products based on 1999-2014 period. Periods of anomalous excess and deficits in LCFs in the SIO clearly reveal different sub-seasonal circulation attributes across the equator with precursor signals to the strength of ISM. Anomalous circulation composites from the excess LCF periods shows mean sea level pressure (MSLP) enhancements of about 2 hPa in the MH region in correspondence with increasing areal extent and intensifications in LCFs, and a net increase in low-level southerly momentum between MH and monsoon trough (MT) environments. The MSLP reinforcements in the MH are clearly demonstrated to emerge from the strength of cloud-top radiative cooling and associated winds and mass adjustments. The 10-20 [30 -50] day modes of the circulation in the SIO further elucidates zonally propagating [quasi-stationary] manifestations on MH reinforcements. There is an increase in meridional transport of moisture fluxes, by about 7 times relative to deficit LCF periods, channelled through aconduit region (15-30°S, 60-90°E) juxtaposing the cross-equatorial circulation (CEC) from both western and eastern sides of the Indian Ocean. This occurs in tandem with a zone of moisture flux convergence in the ISM region advancing poleward towards the climatological MT region - implying that excess LCF periods portend the likelihood of stronger ISM. Deficit LCF periods, on the contrary, show a mirrored scenario of the above with a net northerly low-level wind anomalies between MH and MT, pressure deficits in the MH region, and also portend the likelihood of weaker ISM. Low cloudsin the SIO are not only instrumental for MH stability, but also essential for circulation and moisture support across the equator and the signals for the strength of ISM on sub-seasonal scale.
Advancing Atmospheric Retrieval: A Rapid Physics-Informed Data-Driven Approach using FORUM Simulated Measurements
Authors: Sgattoni Cristina , Chung Matthias , Sgheri Luca
Published: March 2024

FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) represents the ninth Earth Explorer mission chosen by the European Space Agency (ESA) in 2019. This satellite mission focuses on delivering interferometric measurements within the Far-InfraRed (FIR) spectrum, constituting approximately 50% of the Earth's longwave flux emitted into space. Enhanced accuracy in measuring the Top Of the Atmosphere (TOA) spectrum in the FIR is crucial for minimizing uncertainties in climate models. However, current instruments fall short, necessitating the incorporation of innovative computational techniques. The mission aims to refine understanding across various atmospheric variables, including tropospheric water vapor, ice cloud properties, and notably, surface emissivity in the FIR.During the mission's early development, an End-to-End Simulator (E2ES) was devised to showcase proof-of-concept and assess the impact of instrument characteristics and scene conditions on the accuracy of reconstructed atmospheric properties. This simulator comprises a sequence of modules simulating the entire measurement acquisition process, accounting for all major sources of discrepancies in operational conditions leading to the retrieval of geophysical quantities.From a mathematical perspective, two challenges arise: the radiative transfer equation, known as the direct problem, and its inversion, referred to as the retrieval problem. Both problems can be addressed through a full physics method, particularly applying the Optimal Estimation (OE) approach—a specialized Tikhonov regularization scheme based on Bayesian formulation. However, the computational demands of a full physics method hinder Near Real-Time (NRT) data analysis. Faster models become imperative for next-generation satellites measuring hundreds of spectra per minute and climatology models simulating years of global-scale radiative transfer.To expedite solutions for both problems, a hybrid approach is employed, combining an a priori regularized data-driven method utilizing the Moore-Penrose pseudoinverse and a neural network approach.  
Enhancing salt marshes monitoring: Estimating biomass with drone-derived habitat-specific models.
Authors: Curcio Andrea Celeste , Barbero Luis , Peralta Gloria
Published: March 2024

To quantify the amount of carbon sequestered by salt marshes, it is essential to estimate their aboveground biomass (AGB). In this study, we propose utilizing low-altitude remote sensing techniques to collect high-resolution LiDAR and multispectral (MS) data for biomass assessment. We characterized salt marsh vegetation habitats by examining vegetation indices (VIs), and the high-resolution topographic information from LiDAR helped assess habitat distribution. Specifically, the Anthocyanin Reflectance Index 2 (ARI2), combined with the Digital Surface Model (DSM), allows for the identification and separation of the two habitats with distinct dominant species (Sarcocornia spp. and Sporobolus maritimus). The VIs for the two vegetation classes exhibit different seasonal changes throughout the annual cycle, suggesting distinct growth mechanisms for each. Biomass models for the specific seasons are created, showing higher precision (up to 99%) from habitat-specific models compared to those treating species uniformly. Differences are observed in biomass estimation patterns depending on whether the marsh is assessed as a whole or separated into dominating habitats, indicating that the two dominant species exhibit different behaviours that influence biomass production differently throughout the year. Seasonal variations in AGB indicate a peak in summer and a decline in spring, with annual variation accounting for just 9% of the total output, possibly influenced by increased soil salinity and stress in spring. Using LiDAR and MS data from an unmanned aerial vehicle (UAV) is essential for precise identification of primary marsh habitats, facilitating the creation of highly accurate biomass models. This user-friendly, repeatable, and cost-effective method enables the study of salt marshes, evolutionary trends, and climate change response requiring less fieldwork.
Emergy-based accounting method for glacier ecosystem services valuation (ESV): A case of Tibetan Plateau
Authors: Zhang Can , Su Bo , Fang Shiming , Beckmann Michael , Volk Martin
Published: March 2024

Glacier ecosystems play a vital role in providing freshwater resources to humans, in regulating and stabilizing climate, runoff and offering potential for hydropower generation, and in providing unique cultural services for humans. However, few studies have systematically assessed the socio-economic contribution of glaciers, especially from a contributor perspective. To fill this knowledge gap, the aim of this study is to develop an assessment method applied to glacier ESV based on emergy theory. Emergy analysis is a measure that converts all forms of energy into the same unit of comparison, providing a common scale for measuring and comparing all forms of energy. This includes: (1) to develop an emergy-based accounting system and methods for glacier ESV from a donor-side perspective; (2) to evaluate the spatiotemporal characteristics of glacier ecosystem services (ESs) on Tibetan Plateau (TP) during the early 21st century. The results show that: (1) glacier ESs on TP increased from 1.25E+25 sej/yr in the 2000s to 1.28E+25 sej/yr in the 2010s, which is mainly due to the fast growth of provisioning services, although a slow decrease of regulating services is observed during the study period; (2) among the various services, the descending order of value is climate regulation (7.34E+24 sej/yr, 55.65%), hydropower generation (2.73E+24 sej/yr, 20.67%), and freshwater resources (2.68E+24 sej/yr, 20.31%); (3) the spatial characteristics of glacier ESs, where the glacier ESs values in the marginal TP are larger than in endorheic TP; (4) glacier ecosystems are divided in stock and flow, with stock referring to glaciers in the solid state and flow referring to glaciers in the so-called meltwater state. The glacier stock service still dominates in the early 21st century with a small downward trend in the last decade, while the glacier flow service has increased significantly from 2000s to 2010s due to the glacier recession. (5) Except climate regulation and carbon sequestration, all other services values are increasing, especially for tourism and recreation, and knowledge and education, which have shown a rapid growth with the social development. The theory and methodology used here are conducive to enhancing the understanding of material and energy flows within the cryosphere-society system and providing common scales for measuring and comparing different material, energy and monetary flows. Furthermore, this study will help to improve the glacier service assessment system, lay the theoretical and methodological foundation for the development of regional and global glacier service accounting, and provide a scientific basis for glacier resource development and management.
Basal melting of Antarctics ice shelves in Amundsen and Bellingshausen seas
Authors: Felemban Lamees Refat
Published: March 2024

West Antarctic ice shelves in the Amundsen and Bellingshausen seas are losing mass from basal melting. This is caused by the intrusion of circumpolar deep water underneath the ice shelves. The mechanisms driving circumpolar deep water towards the Western Antarctic ice shelves are still not fully understood. I will present time series (for the years from 2003 to 2023) of basal melt rate for the ice shelves in Amundsen and Bellingshausen seas along with time series for the upper end of Antarctic bottom water layer from underneath ice shelves. From these two data sets, we want to quantify the mass loss from the ice shelves and see how the freshwater flux that results from it will affect the volume of Antarctic bottom water. Our work requires estimating ice shelf height change from 2003 to 2023 in two different reference frames: Lagrangian and Eulerian from differential equations of height change where we can incorporate satellite observations of ice elevation. From the differential equation of Lagrangian reference frame, we determine the characteristics of ice flow of the ice shelf. This will help us to highlight the contribution of basal melt rate to the ice shelf height change. The height change from Eulerian reference frame will be used in a formula that produces a time series of basal melt rate. This time series will show the differences between the basal melt rate in the Eulerian reference frame and the steady state in the Lagrangian frame. For the Lagrangian ice shelf height where the ice shelf height is equal to ice elevation data from satellite altimetry minus ocean height data, we will create a unique data set of ocean surface height containing data produced by Southern Ocean State Estimate (SOSE) general circulation model where the data shows the distribution of water properties to a high depth.  This can be used to evaluate the ocean heat content. With this dataset, we aim to determine how many times the circumpolar deep water travels from the Antarctic circumpolar current to the ice shelves in the Amundsen and Bellingshausen seas (in the years between 2003 and 2023). We also want to ascertain whether changes in the distribution of water layers beneath the ice shelves contribute to propelling the circumpolar deep water closer to the surface. This could potentially aid in the improvement of ice shelf models by incorporating a function that represents the effect of ocean thermal forcing on ice shelves.
 
 
 
 
 
 
 
 
 
 
 
 
Characteristics of slip-rate variability and temporal earthquake clustering across a distributed network of active normal faults from in situ 36Cl cosmogenic dating of fault scarp exhumation.
Authors: Roberts Gerald P. , Sgambato Claudia , Papanikolaou Ioannis , Mildon Zoe , Beck Joakim , Michetti Alessandro , Faure Walker Joanna , Mitchell Sam , Meschis Marco , Shanks Richard , Phillips Richard , McCaffrey Ken , Vittori Eutizio , Iezzi Francesco , Robertson Jennifer , Visini Francesco , Iqbal Maz
Published: March 2024

We present an in situ 36Cl dataset recording the exhumation of 27 active normal fault planes by earthquake slip for the central Apennines, Italy. We do this to constrain the characteristics of earthquake clustering and anticlustering across the entire extending orogen, and in an attempt to constrain the reasons why clustering and anticlustering occurs. We show that duration and magnitude of clustering and anticlustering, and their characteristics, can be explained by a model where the transfer of differential stress between faults and their underlying shear-zones, and between neighbouring fault/shear-zone structures, produces changes in strain-rates on underlying viscous shear zones which drive periods of rapid or reduced slip-rate on their overlying faults. We suggest that stress increase on an underlying shear zone produced by coseismic slip on its overlying fault could be the mechanism that initiates an earthquake cluster. We suggest that stress reductions on shear-zones from coseismic slip located across strike could be the mechanism that initiates an earthquake anticluster. The durations of anticlusters are controlled by the summed stress decreases through time on shear zones, because although these shear zones are slipping relatively slowly, eventually they will load their overlying fault to failure initiating a new cluster, with anticlusters induced across strike. Thus, there is dynamic feedback both up and down dip between faults and their underlying shear zones and crucially across strike between neighbouring fault/shear-zone structures. If the dynamics producing clustering and anticlustering can be constrained, it may be that observations of these phenomena should be included in probabilistic seismic hazard assessments (PSHA) and also interpretations of regional deformation rates and crustal rheologies based on geodetic data. Multi-millennial clustering and anticlustering should become a subject for discussion in these scientific communities.
Atmospheric radioisotopes in cryoconite from the Flade Isblink ice cap, NE Greenland
Authors: Beard Dylan , Baccolo Giovanni , Clason Caroline , Millward Geoffrey , Łokas Edyta , Rangecroft Sally , Sala Dariusz , Wachniew Przemysław , Blake William
Published: March 2024

Under climatic warming and increased melting, glaciers and ice caps are becoming secondary sources of contaminants deposited decades ago. Cryoconite, an organic-rich material found on the surface of many glaciers, is particularly efficient at accumulating airborne contaminants due to biogeochemical exchanges with the organic matter within cryoconite. Atmospherically derived radioactive isotopes, commonly referred to as fallout radionuclides, have now been found to accumulate in cryoconite globally. However, data from the polar regions, especially ice sheets and ice caps, is scarce. This study helps to address this regional gap in understanding fallout radionuclide accumulation in glacial settings. We present the first radioactivity dataset from cryoconite on a Greenlandic ice cap and assess the role of cryoconite in the distribution of radioactive species in the High Arctic. Forty-six cryoconite samples were collected from the Flade Isblink ice cap (NE Greenland) in August 2022. These samples were analysed via alpha and gamma spectrometry for atmospheric radionuclides, including 137Cs, 241Am, 210Pbexc., 207Bi, 7Be, and several plutonium isotopes. The results of this study confirm cryoconite's exceptional ability to accumulate fallout radionuclides, even in remote and relatively pristine regions such as Northern Greenland. The activities of radionuclides in cryoconite from Flade Isblink are among the highest reported across the High Arctic and the highest ever reported from Greenland. Flade Isblink's radioactivity source is compatible with the stratospheric reservoir established during atmospheric nuclear tests and with weapon-grade fissile fuel, likely originating from Novaya Zemlya. Our findings emphasise the necessity for continued research efforts on the release of legacy contaminants from glaciers, particularly given accelerated global warming and consequent glacier retreat.
Climate controls on deuterium excess in Antarctic precipitation - insights from an isotope-enabled atmospheric GCM ECHAM
Authors: Gao Qinggang , Sime Louise C. , McLaren Alison J. , Bracegirdle Thomas J. , Capron Emilie , Rhodes Rachael H. , Steen-Larsen Hans Christian , Shi Xiaoxu , Werner Martin
Published: March 2024

We present new work that improves our understanding of the controls on Antarctic precipitation and ice cores. This is critical for gaining insights into polar changes. The work relies on our implementation of innovative water tracing diagnostics in an atmospheric general circulation model. These tracers provide new precise information on moisture source locations and properties of Antarctic precipitation - and allow us to evaluate how one should interpret water isotopic profiles of Antarctic ice cores. Heavy precipitation in Antarctica is sourced by longer-range moisture transport: it comes from 2.9° (300 km, averaged over Antarctica) more equatorward (distant) sources compared to the rest of precipitation. Precipitation during negative phases of the Southern Annular Mode (SAM) also comes from more equatorward moisture sources (by 2.4°, averaged over Antarctica) than precipitation during positive SAM phases, likely due to amplified planetary waves during negative SAM phases. Our new, more precise information on moisture source properties also shows that the logarithmic definition of deuterium excess exhibits a stronger correlation with moisture source properties than the classical linear definition of deuterium excess. Results support the conventional practice of interpreting deuterium excess in terms of source sea surface temperature, without concerning source 2 m relative humidity and source 10 m wind speed. We find there is no added value to include δD for the reconstruction of source temperature in addition to deuterium excess, but including deuterium excess does bring some (small) added benefit in reconstructing site temperature in addition to δD. Nevertheless, it is arguable whether one should incorporate deuterium excess considering uncertainties in the transfer function and post-depositional effects on deuterium excess. Our results demonstrate that improving our understanding of the physics underlying supersaturation function could also help constrain the key uncertainties associated with these model results. Overall, our novel water tracing diagnostics enhance our understanding of the controlling factors of Antarctic precipitation and ice cores.
Beyond Static Analysis: Importance of Multi-Temporal Inventories in Alpine Environments for Dynamic Landslide Assessment in Belluno Province (Veneto Region, NE, Italy). 
Authors: Bhookya Rajeshwari , Floris Mario
Published: March 2024

Landslides are complex and dynamic natural hazards that require a comprehensive understanding of their temporal changes for effective assessment and management. Traditional landslide inventories often focus on static analysis, providing a snapshot of landslide occurrences at a specific point in time. However, to capture the dynamic nature of landslides and assess their evolution over time, multi-temporal inventories are essential. This study aims to go beyond static analysis by proposing the use of multi-temporal inventories for dynamic landslide assessment. The approach involves the integration of remote sensing data, advanced modeling techniques, and deep learning algorithms to analyze and map landslides over multiple time periods. By considering the temporal dimension, the proposed method enables the identification of changes in landslide patterns, movements, and susceptibility over time. We used orthophotos retrieved from WMS and WMTS services provided by the Italian national portal, covering the period from 1989 to 2021, for a study conducted in the Cordevole and Alpago areas (Belluno province, NE Italian Alps). These areas were impacted by two extreme meteorological events (return period > 100 years) in 2018 (October 27th–30th) and 2020 (December 4th–6th). The first, known as windstorm VAIA, has induced severe damage to the forest cover. The generated multi-temporal inventories provide valuable information for understanding the temporal dynamics of landslides, which is crucial for accurate landslide hazard assessment and risk management. The findings of this study highlight the importance of incorporating multi-temporal inventories into landslide assessment methodologies to enhance our understanding of landslide behavior and improve decision-making processes.Acknowledgement:This study was carried out within the PNRR research activities of the consortium iNEST (Interconnected North-Est Innovation Ecosystem) funded by the European Union Next-Generation EU (Piano Nazionale diRipresa e Resilienza (PNRR) – Missione 4 Componente 2, Investimento 1.5 – D.D. 1058 23/06/2022, ECS_00000043). This manuscript reflects only the Authors’ views and opinions; neither the European Union nor the European Commission can be considered responsible for them.
Climate change, water resources and the hydropower system in Iceland
Authors: Gunnarsson Andri , Helgason Hörður B. , Sveinsson Óli G. B. , Tómasson Gunnar G.
Published: March 2024

In Iceland, hydropower represents around 72% of the gross electricity generation annually, with energy production capabilities around 13.8 TWh/a. Most of the hydropower infrastructure is in the central highlands, relying on water resources temporarily stored as snow and ice. These resources are vulnerable to climate change, projected to undergo substantial changes in the coming decades. Changes in flow volumes, seasonality of flow and extremes will have a strong impact on the hydropower system in Iceland as over 50% of inflow energy to the system originates from glacier ablation during summer. The high natural climate variability and energy system isolation pose a risk to the energy security of the power system as droughts and cold periods are usually not foreseen with great advance. Changes in hydrological flow dynamics, e.g.: onset of snow- and glacier melt, melt magnitudes and precipitation patterns pose a series of challenges for the hydropower system.In glacier-dominated catchments, climate warming will initially increase glacier meltwater runoff to a maximum and then runoff will reside as the glacier area and volume decrease over time. The timing of the discharge peak is influenced by the catchment topoclimate characteristics and location. Understanding and quantifying these changes is important both for operational control and planning of energy infrastructure on shorter timescales (days, months, years) and climate change adaptation, on longer time scales, for both current energy projects as well as future development to maximize efficient water resource utilization.To assess the impacts of changes in inflow dynamics on the hydropower system, hydrological models were developed to create inflow scenarios. Historical inflows were first reconstructed, followed by a construction of future runoff scenarios using climate projections and different glacier geometry evolution. This allowed for the assessment of meltwater-induced changes in runoff, although generally increasing in the next decades, certain areas are closer to reaching maximum meltwater production and will decrease in the coming decades. In all cases meltwater-induced increase in runoff is temporary, while large uncertainties exist with the timing of maximum peak inflow.Utlization of the inflow scenarios created include current day operation to optimize reservoir management strategies and the design of future power projects, including refurbishments and capacity increases. This accommodates the expected increased flow rates 10–50 years into the future.   
Linking the Permanent Service for Mean Sea Level’s (PSMSL) global mean sea level dataset to the ellipsoid 
Authors: Kim Chanmi , Matthews Andrew , Bradshaw Elizabeth
Published: March 2024

The Permanent Service for Mean Sea Level (PSMSL) is the internationally recognised global sea level data bank for long term sea level change information from tide gauges, responsible for the collection, publication, analysis and interpretation of sea level data. The PSMSL was founded 90 years ago, and today operates from the Liverpool site of the UK’s National Oceanography Centre. The PSMSL’s main product, a dataset of monthly and annual means from over 2000 locations worldwide aggregated from over 200 suppliers, is a cornerstone in our understanding of changes in sea level over the two centuries. For our highest quality Revised Local Reference (RLR) dataset, we ensure the data can all be referred to a fixed point on land, ensuring a consistent vertical reference frame is used throughout the record. Also, we provide GNSS solutions near the guage to estimate the ellipsoidal height and rate of movement of the site in our website.Here we introduce the PSMSL mean sea level dataset, and explain how we present these ellipsoidal ties on our website. We also discuss ongoing efforts to improve the breadth of metadata we supply, and attempts to ensure they meet FAIR data practices (Findable, Accessible, Interoperable and Reusable).  
Toward the Local Identification of Equatorial Waves 
Authors: B. Cruz Joao , Castanheira José M. , C. daCamara Carlos
Published: March 2024

Equatorial waves (EWs) are synoptic to planetary-scale disturbances in the tropical atmosphere and are associated to a variety of tropical atmospheric phenomena. For instance, EWs can couple with convection, modulating a substantial fraction of cloud and rainfall variability in the tropics. Space-time filtering techniques that rely on the projection of data onto the structures of EWs are widely used in the literature. Such projection methods are employed with multiple purposes, including the unravelling of physical mechanisms underlying tropical atmospheric phenomena and the evaluation of numerical weather predictions in the tropics. However, most projection techniques rely on the global structures of these waves and, to our knowledge, there have not been efforts toward developing methodologies that identify EWs locally, i.e. over regions covering specific longitude ranges. This type of approach would highly decrease both the amount of data required and the computational power needed to identify EWs. Furthermore, it could potentially reduce the artificial effects local forcings may have on global projections.This work makes use of the meridional and zonal structures of the solutions to the free Laplace tidal equations, known as Hough vector harmonics. By exploiting the properties of these solutions, we propose a methodology that allows for the identification of EWs over specific longitude ranges and perform a local analysis of fundamental wave properties. This work was supported by IDL (UIDB/50019/2020) and CESAM (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020) through national funds by Fundação para Ciência e Tecnologia I.P./MCTES (FCT), Portugal.
Robust polar amplification in ice-free climates relies on ocean heat transport and cloud radiative effects 
Authors: England Mark , Feldl Nicole
Published: March 2024

A fundamental divide exists between previous studies which conclude that polar amplification does not occur without sea ice and studies which find that polar amplification is an inherent feature of the atmosphere independent of sea ice. We hypothesise that a representation of climatological ocean heat transport is key for simulating polar amplification in ice-free climates. To investigate this we run a suite of targeted experiments in the slab ocean aquaplanet configuration of CESM2-CAM6 with different profiles of prescribed ocean heat transport, which are invariant under CO2 quadrupling. In simulations without climatological ocean heat transport, polar amplification does not occur. In contrast, in simulations with climatological ocean heat transport, robust polar amplification occurs in all seasons. What is causing this dependence of polar amplification on ocean heat transport? Energy-balance model theory is incapable of explaining our results and in fact would predict that introducing ocean heat transport leads to less polar amplification. We instead demonstrate that shortwave cloud radiative feedbacks can explain the divergent polar climate responses simulated by CESM2-CAM6. Targeted cloud locking experiments in the zero ocean heat transport simulations are able to reproduce the polar amplification of the climatological ocean heat transport simulations, solely by prescribing high latitude cloud radiative feedbacks. We conclude that polar amplification in ice-free climates is underpinned by ocean-atmosphere coupling, through a less negative high latitude shortwave cloud radiative feedback that facilitates enhanced polar warming. In addition to reconciling previous disparities, these results have important implications for interpreting past equable climates and climate projections under high emissions scenarios.
Accelerated drought-induced resilience decline across European forests
Authors: Buras Allan , Meyer Benjamin , Gregor Konstantin , Layritz Lucia , Jevšenak Jernej , Zang Christian , Rammig Anja
Published: March 2024

The recent intensification of hotter droughts due to climate change has resulted in a reduced resilience of forests at global scale. This response is not only mirrored by increasing rates of tree dieback, but also reflected in a reduced canopy greenness (Buras et al., 2021) as well as emerging statistical early-warning signals of declining forest resilience (EWS, Forzieri et al., 2022). Yet, a systematic investigation on how atmospheric water demand, canopy greenness decline, and EWS are linked across European forests and including the most recent extreme droughts of 2022 and 2023 is missing. To overcome this research gap, we 1) deployed time series of remotely sensed canopy greenness (NDVI) at moderate spatial resolution (6.25 ha) over the period 2001-2023 for the European continent, 2) derived three independent statistical indices of forest resilience, and 3) related these data streams to atmospheric water demand (VPD).Over the study period, VPD displayed an increasing trend over most of Europe, which was mirrored in a concurrent decline of forest canopy greenness. Moreover, we found a clear and significant non-linear negative impact of rising VPD on canopy greenness for 75% of European forests. The grid-specific frequency of identified EWS was significantly linked to VPD and featured a record extent in 2023 with about one fifth of European forests being affected. This observation was independently supported by a strong increase in the spatiotemporal memory of canopy greenness since the extreme drought of 2018 (Buras et al., 2020). Finally, in the years following 2018 VPD-based predictions increasingly overestimated canopy greenness, hinting at forests decreasing ability to recover from extreme drought impacts. In conclusion, our study underscores the enhanced vulnerability of European forests during the extraordinarily dry period 2018-2023 with important implications for forestry, land-based mitigation plans, and regional climate feedbacks. Buras, A., Rammig, A., Zang, C.S., 2021. The European Forest Condition Monitor: Using Remotely Sensed Forest Greenness to Identify Hot Spots of Forest Decline. Frontiers in Plant Science 12, 2355. https://doi.org/10.3389/fpls.2021.689220Buras, A., Rammig, A., Zang, C.S., 2020. Quantifying impacts of the 2018 drought on European ecosystems in comparison to 2003. Biogeosciences 17, 1655–1672. https://doi.org/10.5194/bg-17-1655-2020Forzieri, G., Dakos, V., McDowell, N.G., Ramdane, A., Cescatti, A., 2022. Emerging signals of declining forest resilience under climate change. Nature 608, 534–539. https://doi.org/10.1038/s41586-022-04959-9
An experimental demonstration of fault preconditioning for reduced seismic hazard
Authors: Fryer Barnaby , Noël Corentin , Arzu Feyza , Lebihain Mathias , Passelègue François
Published: March 2024

The mechanical stimulation of a fault or fracture in the case of an Enhanced Geothermal Reservoir (EGS) is generally reliant on inducing shear dilation of a targeted discontinuity. However, this same process can lead to the nucleation of a potentially-damaging seismic event. Here, a reservoir stimulation technique known as preconditioning is demonstrated experimentally for the first time. This technique consists of initially increasing the effective normal stress along the fault, in practice corresponding to a period of fluid production. Following this the fault is locally unloaded, corresponding to fluid injection. As the unloading continues, a slipping patch may form, eventually leading to dynamic rupture. However, the previously-induced high effective normal stress further along the fault acts as a fracture energy and reduced-stress-drop barrier, potentially resulting in rupture arrest. Here, a highly-instrumented (strain gauges, accelerometers, acoustic sensors, displacement sensors, load cells) biaxial apparatus is used to demonstrate this procedure, making use of the translucence of polymethylmethacrylate (PMMA) and a high-speed camera to image the development of propagating ruptures. It is demonstrated, as previously predicted from theory, that preconditioning has the ability to halt dynamic ruptures and may therefore be a viable stimulation technique resulting in reduced hazard in EGS stimulation. Specifically, experiments are performed at nominal normal stresses of 60, 90, and 120 bar, with preconditioning (or normal stress increase) corresponding to approximately 8, 16, and 24%; in addition to control cases with no preconditioning. Generally, preconditioning slows rupture propagation at 8% normal stress increase and completely halts it for larger values of preconditioning. It further results in a reduced shear stress drop, increased fracture energy, and reduced slip velocity. These results may one day have further implications for the potential of controlled stress release along natural faults.
Moderate impact of landfill gas on a naturally reducing aquifer should not be confused with leachate pollution   
Authors: Preziosi Elisabetta , Parrone Daniele , Frollini Eleonora , Ghergo Stefano , Sciarra Alessandra , Ruggero Livio , Ciotoli Giancarlo
Published: March 2024

The processes leading to high levels of arsenic, iron, and manganese in a naturally reducing aquifer beneath a landfill are investigated. Between 2016 and 2022, groundwater monitoring (physical-chemical parameters, major and trace inorganic compounds) has been complemented with the analysis of environmental isotopes (tritium, δ2H, and δ13C) of groundwater and of the dissolved gases (δ13C of CH4 and CO2, 14C of CH4). Statistics, including Pearson/Spearman correlation and PCA, were used to define the main correlation among variables. The presence of methane and carbon dioxide was attributed to landfill gas migration from the waste as 14C dating confirmed that methane is modern (F14C = 1.0684) and likely produced by methyl fermentation within the waste. While methane, enhancing the naturally reducing conditions of the aquifer, appears to be the driver of the high concentration of Fe and As, Mn appears to be governed by carbon dioxide. At the same time, CO2 may locally lower the pH, thus increasing the dissolution of sedimentary carbonates and ultimately producing high alkalinity and salinity. Furthermore, the reuse of water from leachate treatment to meet circular economy requirements was invoked to explain the elevated levels of tritium and 2H, associated with significantly negative 13C, observed in a production well and in a nearby piezometer. The integration of environmental isotopes and geochemical parameters allowed to exclude leachate contamination: tritium, δ2H, and δ13C were within the expected range for natural groundwater. No compounds typical of leachate contamination were detected. Environmental isotopes can fruitfully complement traditional monitoring when the comprehension of processes is desired, but this requires an expert judgment and a solid conceptual hydrogeological model.
A novel model of volcanic plume evolution from high-temperature chemistry to reactive plume chemistry in the atmosphere
Authors: Nies Alexander , Roberts Tjarda , Dayma Guillaume , Fischer Tobias , Kuhn Jonas
Published: March 2024

The first seconds of the interaction of volcanic gases with the atmosphere have so far often been drastically simplified, e.g., by assuming thermochemical equilibrium. In this period, hot and reduced magmatic gases mix with ambient air and undergo rapid cooling. The in-mixture of atmospheric oxygen triggers fast oxidation processes which depend on the dynamic interplay of chemical kinetics, mixing and cooling.We present a novel chemical box model, which can capture rapid chemical kinetics alongside cooling and mixing of the early plume. The model combines a chemical combustion mechanism with atmospheric chemistry mechanisms and includes sub-mechanisms for halogens, sulfur, reactive nitrogen and mercury, respectively. It is fast and flexible to test many different emission temperatures, mixing scenarios, eruption styles, and gas compositions.Here, we focus on the formation of reactive halogen species (e.g. bromine oxide (BrO), bromine chloride (BrCl), hypobromous acid (HOBr), and atomic bromine (Br)) during the first seconds, minute to hours of plume evolution, which significantly influence atmospheric chemistry on a regional scale. We study the impact of the high-temperature initializations on ambient-temperature plume chemistry to capture for example the catalytic destruction of ozone by bromine chemistry in the cooled plume. The simulations show that up to 40% of the emitted bromine can be converted into reactive forms within seconds. It promotes fast formation of BrO in the early evolution of the volcanic plume, at magnitudes consistent with UV-remote sensing measurements.We further assess the presence of reduced species (e.g. molecular hydrogen (H2) and carbon monoxide (CO)) in the cooled plume and potential implications for the interpretation of observations of redox pairs in the plume. Our kinetic model contrasts to previous thermochemical equilibrium assumptions of near-complete oxidation of H2 and CO. We identify emission temperatures and plume cooling conditions that allow these reduced species to persist whilst reactive bromine is formed, as well as conditions where the reduced species become oxidized.The combustion-atmospheric model is a unique tool for analyzing volcanic plume composition measurements as it provides the link to the original composition of the magmatic gas by a kinetic treatment of the magma-atmosphere interface. Future applications include the study of aerosol formation by SO2-sulfate transformation, mercury and NOx-nitrate chemistry.   
Investigation of SOM sequestration and storage in the Southern Transdanubian region of Hungary
Authors: Végh Péter , Balázs Pál , Bidló András , Horváth Adrienn
Published: March 2024

Site factors determine the occurrence and growth of forest stands. The climate is one of the most important. In Hungary, several forest stands located near to the Xeric limit, where climate change is more sensitive. Therefore carbon-rich forests and their soils are being prioritized to achieve carbon neutrality as soon as possible. Our research aims to assess and compare the organic carbon stored in oak and beech forest ecosystems of different climate classes.In the last period, we sampled 2 Beech, 11 Sessile oak and 13 Turkey oak forest stands to determine the amount of soil organic carbon stored in the soil.The soils were collected by soil boring to 0-110 cm. Besides the soil sampling, the existing forest stand composition assessed on each stand near to sampling points.Based on the analyses carried out in the 26 selected forest stands, the soils of the sites can be classified as Cambisols and Luvisols (WRB 2023). The soil pH showed slightly acidic to neutral (mean H2O = 6.7), and the texture can be determined as loam. The relative organic matter content (SOM) was 0.67% on average between 0-110 cm. It corresponds to ~8.2 t of carbon per hectare.With the accelerated rate of climate change (drought), there is an increasing urgency to assess the status of ideal organic matter-rich soils and to develop adaptation strategies to increase the carbon stock.This article was made in the frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme. This publication was supported by the project GINOP-2.3.3-15-2016-00039.
Streamflow Prediction and Flood Forecasting with Time-Lag Informed Deep Learning framework in Large Transboundary Catchments
Authors: Ma Kai , He Daming
Published: March 2024

In facing the challenges of limited observational streamflow data and climate change, accurate streamflow prediction and flood management in large-scale catchments become essential. This study introducing a time-lag informed deep learning framework to enhance streamflow simulation and flood forecasting. Using the Dulong-Irrawaddy River Basin (DIRB), a less-explored transboundary basin shared by Myanmar, China, and India, as a case study, we have identified peak flow lag days and relative flow scale. Integrating these with historical flow data, we developed an optimal model. The framework, informed by data from the upstream Hkamti sub-basin, significantly outperformed standard LSTM, achieving a Kling-Gupta Efficiency (KGE) of 0.891 and a Nash-Sutcliffe efficiency coefficient (NSE) of 0.904. Notably, the H_PFL model provides a valuable 15-day lead time for flood forecasting, enhancing emergency response preparations. The transfer learning model, incorporating meteorological inputs and catchment features, achieved an average NSE of 0.872 for streamflow prediction, surpassing the process-based model MIKE SHE's 0.655. We further analyzed the sensitivities of the deep learning model and process-based model to changes in meteorological inputs using different methods. Deep learning models exhibit complex sensitivities to these inputs, more accurately capturing non-linear relationships among multiple variables than the process-based model. Integrated Gradients (IG) analysis further demonstrates deep learning model's ability to discern spatial heterogeneity in upstream and downstream sub-basins and its adeptness in characterizing different flow regimes. This study underscores the potential of deep learning in enhancing the understanding of hydrological processes in large-scale catchments and highlights its value for water resource management in transboundary basins under data scarcity.