bluuebunny/crossref_metadata_2025 huggingface dataset:
On the First Observed Wave-induced Stress over the Global Ocean
Authors: Chen Sheng
Published: March 2021

Despite many investigations/studies on the surface wave-induced stress, the global feature of the wave-induced stress has not been obtained previously as that requires a simultaneous observation of wave spectra and wind on a global scale. The China France Oceanography Satellite (CFOSAT) provided an opportunity for the first time to evaluate the global wave-induced stress and its contribution to the total wind stress. In this study, the global spatial distributions of wave-induced stress and its correlated index for August to November in 2019 are presented using the simultaneous ocean surface winds and wave spectra from the CFOSAT. The main results show that the wave-induced stress is fundamentally dependent on the wind and wave fields on a global scale and shows significant temporal and spatial variations. Further analyses indicate that there is an upward momentum flux under strong swells and low wind speeds (below approximately 5 m/s), and an anti-correlation between the dimensionless wave-induced stress and the proportion of swell energy to the total. Finally, the variations of the surface wave induced wind stress are clear asymmetric between northern and southern hemispheres in late summer but symmetric in late fall, which are closely associated with the seasonal changes in large-scale atmospheric circulation.
Assimilating sea ice deformation observations using a multiscale alignment ensemble data assimilation method
Authors: Ying Yue , Bertino Laurent
Published: March 2021

A multiscale alignment (MSA) method was proposed by Ying (2019) for ensemble data assimilation to reduce the errors caused by displacement of coherent features. The MSA method decomposes a model state into components ranging from large to small spatial scales, then applies ensemble filters to update each scale component sequentially. After a larger scale component analysis increment is derived from the observations, displacement vectors are computed from the analysis increments through an optical flow algorithm. These displacement vectors are then used to warp the model mesh, which reduces position errors in the smaller scale components before the ensemble filter is applied again.

The MSA method is now applied to a sea ice prediction problem at NERSC to assimilate satellite-derived sea ice deformation observations into the next generation Sea Ice Model (neXtSIM) simulations. Preliminary results show that the MSA can more effectively reduce the position errors of the linear kinematic features of sea ice than the traditional ensemble Kalman filter. The alignment step is shown to be a big contributor for error reduction in our test case. We will also discuss the remaining challenges of tuning parameters in the MSA method and dealing with model deficiencies.
Efficient carbon drawdown allows for a high future carbon uptake in the North Atlantic
Authors: Goris Nadine , Tjiputra Jerry , Ohlsen Are , Schwinger Jörg , Lauvset Siv , Jeansson Emil
Published: March 2021

As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating and ameliorating the ongoing global warming. Projections of the North Atlantic carbon sink in a high-CO2 future vary greatly among models, with some showing that a slowdown in carbon uptake has already begun and others predicting that this slowdown will not occur until nearly 2100.

Discrepancies among models largely originate because of differences in the efficiency of the high-latitude transport of carbon from the surface to the deep ocean. This transport occurs through biological production, deep convection and subsequent transport via the deep western boundary current. For an ensemble of 11 CMIP5-models, we studied the efficiency of this transport and identified two indicators of contemporary model behavior that are highly correlated with a model´s projected future carbon-uptake. The first indicator is the high latitude summer pCO2sea-anomaly of a model, which is tightly linked to winter mixing and nutrient supply, but also to deep convection. The second indicator is the fraction of the anthropogenic carbon-inventory stored below 1000-m depth, indicating how efficient carbon is transported into the deep ocean. By comparing to the observational database, these indicators allow us to better constrain the model ensemble, and demonstrate that the models with more efficient surface to deep transport are best aligned with current observations. These models also show the largest future North Atlantic carbon uptake, which we then conclude is the more plausible future evolution. We further study if the high correlations between our contemporary indicators and a model´s future North Atlantic carbon uptake is also upheld for the next model generation, CMIP6. We hypothesize that this is the case and that our indicators can not only help us to constrain the CMIP6 model ensemble but also inform us about progress made between CMIP5 and CMIP6 in terms of North Atlantic carbon uptake, winter mixing, nutrient supply, deep convection and transport of carbon into the deep ocean.
Seasonal forecasting of groundwater levels in Europe using Pastas time series models and ECMWF SEAS5 forecasts
Authors: Collenteur Raoul , Birk Steffen
Published: March 2021

Groundwater level monitoring is an important way for water resource managers to obtain information on the state of the groundwater system and make informed decisions. In many countries around Europe the right to abstract groundwater (e.g., for drinking water or irrigation purposes) is bound to observed groundwater levels. In particular during and after periods of drought such rights to abstract groundwater may be temporarily denied. As climate change is expected to increase the frequency and intensity of hydrological extremes, severe drought events become more likely, potentially increasing the gap between groundwater demand and supply. An early warning system of a potential groundwater drought could help water managers make informed decisions in advance, to try and counteract the effects of drought. In this study we investigate the use of seasonal forecasts from the ECMWF SEAS5 system to forecast groundwater levels around Europe. The groundwater levels are simulated using a non-linear time series model using impulse response functions as implemented in Pastas (https://github.com/pastas/pastas). Forecasts are compared to groundwater level simulations based on historic meteorological data from the E-OBS database. The methods are tested on 10 long-term (30 years) groundwater level time series. The use of the Standardized Groundwater Index (SGI) is tested to assess the forecast quality and communicate results with decision makers. Bias-correction of the SEAS5 forecasts is found to be necessary to forecast groundwater levels at this local scale. Preliminary results show that the forecast quality depends on the memory effect of the groundwater system, which can be characterized by the auto-correlation of the time series. In addition, it is found that the groundwater levels forecasts have smaller ranges in spring then in the winter months. This may be explained by the fact that groundwater levels in spring are more dependent on evaporation than on precipitation and that forecast of the first are better than those of the latter. The results from this study may be used to improve early warning systems that forecast groundwater droughts.
Regional full seismic waveform inversion of crustal velocity structure in Qaidam Basin
Authors: Yang Biao , Wang Zhoupeng , Wang Yanbin
Published: March 2021

       Under the northward push of the Tibetan Plateau, Qaidam basin is the intersection of Traim block, Bayan Har block and Qilian orogen. Inversion and interpretation of the crustal structure under Qaidam basin are helpful to understand the evolution of the plateau. On November 10, 2008, an Mw6.3 earthquake occurred in the northern margin of Qaidam basin and was recorded by 17 broadband temporary stations installed by the INDEPTH IV Project. We performed inversion of the recorded regional seismic waveforms combining niche genetic algorithm and reflectivity method and obtained the crustal velocity structure of the eastern, western and northwestern part of Qaidam basin.The inversion results show that the structures of the eastern and western basin are similar, where both exist a very thin low velocity layer at about 26km in the middle crust. The thicker lower crust of the west basin results in thicker crust than that of the east basin, which reveals decoupling of the upper and lower crust of the basin. The structure of the northwestern basin is quite different from other regions with much thicker crust, lower velocity of the lower crust and upper mantle, indicating strong deformation and partial melting.
A new and efficient computational thermodynamics approach for magmatic systems
Authors: Riel Nicolas , Kaus Boris , Green Eleanor , Berlie Nicolas , Rummel Lisa
Published: March 2021

During the last decade, the development of numerical geodynamic tools helped the geosciences community to unravel complex thermo-mechanical processes at play during plate tectonics. Yet, the high computational cost of thermodynamic calculations, which simulates phase change, hampers our ability to integrate complex chemistry in such problems. This is particularly important for simulating magmatic processes, where the chemistry of differentiating melts can vary significantly from the mantle to the upper crust. The typical approach, currently used, is to precompute one or many phase diagrams and use them as look-up tables. For many geodynamic processes this is adequate but when the melt chemistry varies drastically it would be better to be able to do thermodynamic calculations on the fly, along with the geodynamic models.

For that, the thermodynamic computational approach must be sufficiently fast, should work fully automatically and be tuned for melting models of magmatic systems, for example by utilizing the recently developed thermodynamic melting model of Holland et al. (2018). Existing approaches do not fulfill all criteria, which is why we have developed a new computational library for this purpose. Our code is written in C, runs on massively parallel machines (MPI) and uses an adaptive mesh refinement strategy to compute phase diagrams. At the moment we have focused on the 'igneous set' of the Holland & Powell dataset (as defined in the thermocalc software) to calculate stable phase equilibria in the system K2O–Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3–Cr2O3 (KNCFMASHTOCr). The code uses pressure, temperature and bulk-rock composition as input and returns relevant petrological and geodynamic information such as (but not restricted to) stable assemblage, phase fractions and phase densities. Different than many of the existing approaches, our method can efficiently utilize initial guesses which naturally occur in geodynamic simulations where the changes in chemistry between timesteps are usually minor.

The methodology performs a Gibbs free energy minimization and involves two main steps. First, we use a combination of levelling methods (iterative change of base) to reduce the number of potential (pure and solution) phases and to bring the G-hyperplane close to solution. Second, we use a partitioning of Gibbs energy approach coupled with local minimization to satisfy the Gibbs-Duhem rule and to retrieve the final set of stable solution phases. To illustrate the efficiency of the library up to supra-solidus conditions we present a set of dry phase diagrams and compare results of our computations with thermocalc calculations.

Ongoing development includes the treatment of solvus to extend its applicability to complex wet systems involving solution phase such as amphibole.
Use of L- and C-Band SAR Satellites for Sea Ice and Iceberg Monitoring (LC-ICE)
Authors: Dierking Wolfgang , Davidson Malcolm
Published: March 2021

In support of ESA's Mission Advisory Group for ROSE-L (Radar Observing System for Europe at L-band), a project team consisting of members of operational ice services and the International Ice Charting Working Group,  the International Ice Patrol, and groups from universities and research institutes is investigating the benefits of using data from L-band SAR in addition to C-band SAR imagery for separating different sea ice classes and detecting icebergs. The tasks are: (1) a critical assessment of the current state-of-the-art in sea ice monitoring and iceberg detection, (2) matching C- and L-band SAR images acquired with temporal gaps of several hours, (3) tests and assessments of the practical use of L-band images in the operational mapping services, and (4) comparison of classification accuracies that can be achieved at C-band, L-band, and a combination of both, based on the results of automated segmentation and classification algorithms. Based on the suggestions of operational ice centers, data have been collected since April 2019 over six test sites for the Northern Hemisphere: Fram Strait, Belgica Bank, northern and southern parts of Greenland, Baffin Bay and Labrador Sea. The SAR images are acquired by Sentinel-1 at Extra Wide and Interferomeric Wide Swath modes, by RADARSAT-2 at ScanSAR mode, and by ALOS-2 PALSAR-2 at Wide Beam and Fine Beam modes. The PALSAR-2 data are provided through the 2019 to 2022 mutual cooperation project between ESA and JAXA on using SAR data in earth sciences and applications. The presentation - with contributions from project partners - will focus on the conclusions from the literature review, assessments of operational ice services regarding the gain they find in using L-band SAR images supplementary to routinely analyzed C-band imagery, and preliminary results of automated classification. 
Introducing HydroPy, an updated global hydrology model rewritten in Python
Authors: Stacke Tobias , Hagemann Stefan
Published: March 2021

Global hydrological models (GHM) are a useful tool to investigate the water cycle, to evaluate its sensitivity towards systematic changes, e.g. human impacts, and to project future conditions in river catchments for varying scenarios. They have been successfully applied for decades and there is still room for improvement.

Recently, we revised the Max Planck Institute for Meteorology’s Hydrology model (MPI-HM), which is an established GHM that was used in multiple case studies and inter-comparison projects. While still performing well, its source code (mainly Fortran77) has become increasingly difficult to maintain, thus hampering the implementation of new processes. For this reason, the model was rewritten from scratch based on the MPI-HM process formulations. The new model is mainly written in Python, thereby taking advantage of the highly optimized numpy and xarray libraries, and, hence, is aptly renamed to HydroPy. Using the original formulations, we make sure to preserve or even improve the old model’s skill while the switch to Python allows for much easier debugging and interactive model development.

In our presentation, we will evaluate the performance of the new HydroPy model and demonstrate its skill to simulate river discharge. Furthermore, we compare HydroPy to its predecessor MPI-HM and discuss the reasons of differences between their results.
Testing the impacts of wildfire on hydrological and sediment response using the OpenLISEM model
Authors: Wu Jinfeng , Nunes João Pedro , Baartman Jantiene E. M.
Published: March 2021

Wildfires have become a major concern to society in recent decades because increases in the number and severity of wildfires have negative effects on soil and water resources, especially in headwater areas. Models are typically applied to estimate the potential adverse effects of fire. However, few modeling studies have been conducted for meso-scale catchments, and only a fraction of these studies include transport and deposition of eroded material within the catchment or represent spatial erosion patterns. In this study, we firstly designed the procedure of event-based automatic calibration using PEST, parameters ensemble, and jack-knife cross-validation that is suitable for event-based OpenLISEM calibration and validation, especially in data-scarce burned areas. The calibrated and validated OpenLISEM proved capable of providing reasonable accurate predictions of hydrological responses and sediment yields in this burned catchment. Then the model was applied with design storms of six different return periods (0.2, 0.5, 1, 2, 5, and 10 years) to simulate and evaluate pre- and post-wildfire hydrological and erosion responses at the catchment scale. Our results show rainfall amount and intensity play a more important role than fire occurrence in the catchment water discharge and sediment yields, while fire occurrence is regarded as an important factor for peak water discharge, indicating that high post-fire hydro-sedimentary responses are frequently related to extreme rainfall events. The results also suggest a partial shift from flow to splash erosion after fire, especially for higher return periods, explained by a combination of higher splash erosion in burnt upstream areas with a limited sediment transport capacity of surface runoff, preventing flow erosion in downstream areas. In consequence, the pre-fire erosion risk in the croplands of this catchment is partly shifted to a post-fire erosion risk in upper slope forest and natural areas, especially for storms with lower return periods, although erosion risks in croplands are important both before and after fires. This is relevant, as a shift of sediment sources to burnt areas might lead to downstream contamination even if sediment yields remain small. These findings have significant implications to identify areas for post-wildfire stabilization and rehabilitation, which is particularly important given the predicted increase in the occurrence of fires and extreme rainfall events with climate change.
Where shall we measure? Results from the second phase of the Ice Thickness Models Intercomparison eXperiment (ITMIX2)
Authors: Farinotti Daniel ,   ITMIX2 consortium
Published: March 2021

Knowing the ice thickness distribution of glaciers and ice caps is of critical importance for a number of studies. However, since measuring ice thickness directly is difficult and time consuming, the availability of such information is generally scarce. Here, we present results from the Second Phase of the Ice Thickness Models Intercomparison eXperiment (ITMIX2) which had a two-fold objective. First, it aimed at characterizing the capability of numerical models to use sparse thickness measurements to their advantage. Second, it aimed at identifying possible strategies for maximizing the information content gained through direct ice thickness surveys.

The experiment was designed around 23 test cases including both real-world and synthetic glaciers, and comprised a set of 16 different experiments per test case simulating different scenarios of data availability. Based on a total of 2,544 individual solutions submitted by 13 different models, our results show that for locations without direct measurements, the ice thickness can be predicted with typical deviations in the order of 16% of the mean ice thickness. Despite large scatter, even limited sets of ice thickness observations are found to be effective in constraining the glacier total volume, particularly when the thickest part of a glacier is surveyed. Other spatial distributions of the ice thickness observations have only a weak influence on the predicted thickness, although surveys restricted to the lowest glacier elevations often result in an underestimation of the glacier’s total volume. The response to the various scenarios of data availability is found to be specific to individual models, and while no single best approach emerges, an ensemble-approach based on a combination of models is shown to be beneficial in terms of accuracy and robustness.
The GPS Scintillations and TEC Variations in Association with A Polar Cap Arc
Authors: Wang Yong , Cao Zheng , Xing Zan-Yang , Zhang Qing-He , Jayachandran Periyadan T. , Oksavik Kjellmar , Balan Nanan , Shiokawa Kazuo
Published: March 2021

The first example of a polar cap arc producing clear amplitude and phase scintillations in the GPS L-band is presented using observations from an all-sky imager and a GPS receiver at Resolute Bay and the SuperDARN Inuvik radar. The polar cap arc moved quickly from the dusk-side to the midnight auroral oval at a speed of ~700 m/s, as revealed by all-sky 557.7 nm and 630.0 nm images. When it intersected the ray path of GPS signals, both amplitude and phase scintillations appeared, which is very different from previous results. Moreover, the scintillations were precisely determined through power spectral analysis. We propose that the strong total electron content (TEC) enhancement (~6 TECU) and flow shears in association with the polar cap arc were causing the scintillations. It provides instructive evidence for the existence of polar cap arc scintillations that may be harmful for satellite applications even through L-band signals.
Prospects of oil-bearing in the Rhine Rift (Germany)
Authors: Galant Yuri , Pikovskiy Yuri , Čížek Pavel
Published: March 2021

Searching for oil in Germany is an urgent task, since from its own reserves Germany can cover only four percent of the total volume of oil required for the country's economy. In this regard, we have conducted research with the aim of assessing the prospects of the Rhine Rift oil potential. Were analyzed in basalts Polycyclic Aromatic Hydrocarbons (PAH). The PAH Petroleum Association clearly indicates the presence of petroleum hydrocarbons in rocks and are an indicator of the oil content of deep horizons. The previous report (EGU2020) highlighted the positive factors of oil   potential in the Rhine Rift. There are favorable geological settings of Rhine Rift, such as seismic activity, new tectonic movements, and presence of basalt, decompressed rocks of mantle, rift stretching mode, and favorable geochemical indications, such as existence of typomorphic oil-associated PAH (Phenanthrene, Chrysene, Pyrene, Benz(a)pyren), presence the components resembling on compositions of Moravia oil . For detailing research conducted mathematical correlation between the non-hydrocarbon components PAH (Naftalen + Homologus, Difenil, Benz (ghi) perylene, Fluorene, Perilen, Antracen, Tetraphen) and hydrocarbon components PAH (Phenanthrene, Pyrene, Chrysene, Benz(a)pyren). Mathematical correlation is 0.041, which is a weak positive relationship on the Chaddock scale. The weak positive relationship between the oil components of PAHs and non-oil components probably indicates that the sources of the oil components of PAHs and non-oil components of PAHs are different. And the source of the oil PAHs is probably the oil fields. Thus the geological-geochemical-mathematical factors point to favorable oil-bearing entrails Rhine Rift! For prospecting   cluster of oil   in the first instance recommended at areas: Bad Urah, Kaizertuhl-Shellingen !

 
Carbon balance of annual versus perennial cropping systems
Authors: Pullens Johannes Wilhelmus Maria , Chen Ji , Lærke Poul Erik
Published: March 2021

To meet the growing challenges of food security, sufficient biomass for biorefineries and mitigation of climate change, perennial grass is recommended as an alternative for annual grain crop to increase biomass production while protecting soil C stock. However, the long-term biomass yield production, soil C stock, and ecosystem CO2 flux are rarely simultaneously evaluated in the same study site, limiting the understanding of C flows in different cropping systems. We compared the annual grain crop triticale (Triticosecale) grown every year since 2012 with the productive perennial grass festulolium (Festulolium braunii) both established in 2012 and festulolium renewed in 2018. Annual yield production, five-year changes in soil C stock, and ecosystem CO2 fluxes in 2020 are documented. The first five-year field observations showed that festulolium produced 76% more biomass as compared to triticale (grain and straw). Meanwhile, there was an increasing trend of soil C stock in festulolium but a declining trend of soil C stock in triticale across the first five years, despite both changes were statistically non-significant. By having measurements of the complete carbon balance for 2020, we can investigate the carbon cycling of a cereal and a perennial grass crop. The results improve our knowledge in how we can optimize the biomass, yield and carbon stocks.

 

Keywords: continuous monoculture; perennial grass; biomass production; soil carbon content; ecosystem CO2 flux
Total and fractional bedload transport in alpine streams approximated by different surrogate measurement systems
Authors: Ammann Lorenz , Nicollier Tobias , Badoux Alexandre , Rickenmann Dieter
Published: March 2021

Knowledge about bedload transport in rivers is of high importance for many hydraulic engineering applications, in particular related to flood protection measures. Passive acoustic surrogate measurement techniques provide useful continuous estimates of bedload transport in terms of total mass, as well as for different grain-size classes.

We compare different surrogate measurement systems regarding their performance in quantifying total and fractional bedload transport in three alpine streams. The investigated measurement systems are the well-established Swiss plate geophone (SPG), an equivalent system in which the geophone sensor is replaced by an accelerometer sensor, and the miniplate accelerometer (MPA) system. The latter is a more recent device and consists of four small square metal plates embedded in elastomere elements. While the signal recorded with the SPG is known to be proportional to the transported bedload mass, we find that the MPA-signal shows a non-linear dependency. In addition, the MPA reacts more sensitively to small grain size classes than the other two systems, indicating a possible alternative to improve the quantification of bedload transport consisting of those classes.

Based on the raw signal recorded with the SPG and the MPA in a flume experiment, we test the ability of different empirical models to predict the known weight of the impacting particle. We show that it is possible to identify the particle weight with high accuracy with relatively simple models using data of either of the two measurement systems. One remaining challenge is to account for the site-to-site variability in the (amount of) signal caused by the combination of differing numbers of plates in the measurement setup and the lateral transmission of the signal across multiple plates, especially for the SPG system.
Measurement of soil hydraulic properties of structured and repacked soils
Authors: Pečan Urša , Žvokelj Luka , Ferlin Jure , Zupanc Vesna , Pintar Marina
Published: March 2021

Soil hydraulic properties provide important information about soil behavior under unsaturated and saturated conditions. Often sampling of undisturbed soils is not possible and soil samples have to be repacked for laboratory analysis. The HYPROP® measuring system (METERgroup, Munich, Germany) is a convenient method for determination of soil water retention characteristics and unsaturated hydraulic conductivity of undisturbed soil samples. It measures the matric potential of the saturated and drying soil sample using two tensiometers placed at different depths. Although the tensiometers are based on a new design that theoretically withstands cavitation at higher tension values, they are still considered to operate in the low tension range. Since soil water retention properties in the low tension range are strongly influenced by soil structure and pore size distribution, we were interested in the changes in hydraulic properties when measured on disturbed and then repacked samples, and undisturbed soil samples. Therefore, we investigated the soil hydraulic properties of three different soil types using the evaporation method on undisturbed and repacked samples. The results provide important insights for the interpretation of the results when the collection of undisturbed samples is not possible, and for designing laboratory experiments with repacked soils.
Partitioning of daily evapotranspiration using a modified shuttleworthwallace model, random Forest and support vector regression, for a cabbage farmland
Authors: Li Han , Chen Han , Huang Jinhui Jeanne , McBean Edward , Zhang Jiawei , Gao Junjie , Lan Zhingqing
Published: March 2021

Prediction of vegetation transpiration (T) is of increasing importance in water resources management and agricultural practices, in particular to facilitate precision irrigation. Traditional evapotranspiration (ET) partitioning dual source modeling requires an extensive array of ground-level parameters and needs model correction and calibration to attain model certainty. In response, a quick and low-cost method is described to predict T using artificial intelligence (AI) modeling based on meteorological factors, status of crop growth factors and soil parameters. This study compares Random Forest (RF) and Support Vector Regression (SVR) in building AI models using three years (2014–2017) of continuous high-resolution monitoring data in a cabbage farmland.Input data included air temperature (Ta), solar radiation (Ra), relative humidity (RH), vapor pressure deficit(VPD), wind speed (Ws), soil moisture (SM), vegetation height (H), and leaf area index (LAI). The results show that soil surface resistance calculations by Monte Carlo iterative method and vegetation stomatal resistance calculations and carbon dioxide concentration and emission, improve performance of the original Shuttleworth–Wallace(S-W) model. In addition, the AI model indicates Ta and Ra are essential inputs for both model types. When there are sufficient observation data, or only lacking soil and vegetation data, the RF model is recommended for use. When there are only limited data or lack of critical Ta and Ra data, the SVR model is the preferred model. Scientific guidance is provided for agriculture precision irrigation, indicating which AI model can best estimate T and water demand for irrigation planning and water management.
What ensemble size is required for accurate forecasts? Idealised model experiments with very large ensembles
Authors: Tempest Kirsten , Craig George
Published: March 2021

Ensembles of numerical weather prediction models are currently used to represent the forecast uncertainty of forecast variables. However due to the computationally expensive nature of these ensembles, these uncertainties are only known with a large sampling error, and often the underlying distributions are assumed to be gaussian for Data Assimilation purposes. Furthermore, it is unclear how many members are required in an ensemble to obtain a designated level of sampling error. This work endeavours to understand how this error decreases as ensembles become larger, and how the forecast uncertainty evolves over a 24 hour free forecast period, before answering the pressing question of: how many ensembles are required in an NWP ensemble in order to sufficiently resolve the uncertainty? To do this, a simple 1D modified shallow water model which replicates the main features of convection is employed in the form of a massive ensemble with over 100,000 members. The shape of the distributions from this ensemble, which develop significant non-gaussianity, resembles those of the operational NWP ensembles of SCALE-RM and ICON, indicating that this model is sufficiently realistic in representing the forecast uncertainty. The simple model will be used to determine the rate of convergence of different forecast variables as ensemble size increases, and to evaluate the errors resulting from using the small ensemble sizes that are typical in operational NWP.
Sensitivity of the Antarctic ice sheets to the warming of MIS11c
Authors: Mas e Braga Martim , Bernales Jorge , Prange Matthias , Stroeven Arjen P. , Rogozhina Irina
Published: March 2021

The Marine Isotope Substage 11c (MIS11c) interglacial (425 – 395 thousand years before present) is a useful analogue to climate conditions that can be expected in the near future, and can provide insights on the natural response of the Antarctic ice sheets to a moderate, yet long lasting warming period. However, its response to the warming of MIS11c and consequent contribution to global sea level rise still remains unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice-sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three ice core and one sedimentary proxy records of ice volume. We identify a tipping point beyond which oceanic warming becomes the dominant forcing of ice-sheet retreat, and where collapse of the West Antarctic Ice Sheet is attained when a threshold of 0.4 oC oceanic warming relative to Pre-Industrial levels is sustained for at least 4 thousand years. Conversely, its eastern counterpart remains relatively stable, as it is mostly grounded above sea level. Our results suggest a total sea level contribution from the East and West Antarctic ice sheets of 4.0 – 8.2 m during MIS11c. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea-level reconstructions, this range is reduced to 6.7 – 8.2 m, and mostly reflects uncertainties regarding the initial configuration of the East Antarctic Ice Sheet.
Palaeoenvironmental signals from stromatolites of the Mesoproterozoic Stoer Group, N.W. Scotland
Authors: Dennis Paul , Duchesne Bridie , Marca Alina
Published: March 2021

The sedimentary environment and notably the climate conditions that pertained during deposition of the Mesoproterozoic (~1200 Ma) Torridonian Stoer Group have been subject to debate for some time. On one hand it has been proposed that, despite the low palaeolatitude, the Group is largely represented by fluvio-lacustrine sediments deposited under cold, possibly glacial conditions.  On the other hand, evidence and arguments have been put forward in favour of either a marine, or arid to semi-arid terrestrial environment. Contributing to this debate, in this study we focus on thin calcitic layers within the Clachtoll formation and younger Poll a’ Mhuilt member that may represent stromatolites, or stromatolite like deposits. Whilst recent work has cast doubt on the biogenic origin of these calcite layers, suggesting they may be either evaporitic or detrital in origin, we believe that much of the petrographic and isotope evidence is equivocal. Focusing on large scale morphology, sedimentary structures, micro-fabrics and mineralogy we  present new evidence for the biogenicity of these deposits. A key difficulty is resolving both diagentic (pressure solution, stylolite development and neomorphism) and later grain growth fabrics associated with low grade metamorphism from unaltered fabrics and grains. In combination with bulk (δ13C and δ18O) and clumped isotope (Δ47) studies we find that whilst the Stoer Group has undergone low grade metamorphism with maximum temperatures of ca. 120oC the isotope system has remained closed with respect to exchange with diagenetic and metamorphic fluids. The implication is that the very depleted δ18O values for the calcites of -18‰VPDB are characteristic of the original environmental conditions. Meteoric water values would need to be as low as -15 to -20‰VSMOW for precipitation of the calcite at ambient Earth surface temperatures. This is prima facie evidence that the deposits are terrestrial and not marine and at face value also implies cold conditions with isotopically depleted rainfall. We cannot rule out, however, that precipitation sourced from a global ocean that is significantly depleted in 18O as suggested by some models may contribute to explaining the very depleted isotope signatures and apparent low temperatures.
Oceanic Anoxic Event 1d (late Albian) in deep-water sediments of the Outer Carpathians, Poland; Carbon isotope and agglutinated foraminiferal records
Authors: Bąk Krzysztof , Zbigniew Górny , Bąk Marta
Published: March 2021

The Albian–Cenomanian transition is stratigraphically still poorly constrained in deep-water environments below the CCD. For this reason, the recognition of the OAE1d in such sedimentary records is extremely rare. Our high-resolution carbon-isotope (δ13Corg) stratigraphy of the Upper Albian and Lower Cenomanian turbidite/hemipelagic succession, accumulated in the marginal Silesian Basin of the Western Tethys, made it possible to identify the interval corresponding to the OAE1d. It has been recognized within two lithostratigraphic units of the Silesian Nappe of the Outer Carpathians (the Lower and Middle Lgota Beds), which are composed mostly of turbidite sediments containing a large amount of bioclastic material occurring in the silty and sandy fraction (locally over 70%). Bioclasts were redeposited from marginal shelf of the European Platform. The hemipelagic non-calcareous claystones which separate the turbidite sequences contain deep-water agglutinated foraminiferal (DWAF) assemblages, and are devoid of calcareous benthic foraminifers.

Using the analysis of the DWAF morphogroups, as well as changes in the benthos abundance and its taxonomic composition in relation to the characteristics (colour and TOC content) of hemipelagic sediments, we indicated changes in the environmental conditions that took place during the OAE1d at the bottom of the Silesian Basin. The most abundant horizons of organic-rich shales are characteristic of the lower part of the OAE1d succession corresponding to the Pialli Level from the Umbria-Marche Basin, although thin intercalations of black shales are also present along the upper part of this succession, where the hemipelagic sediments are dominated by green-coloured shales. The variability of organic matter in the studied sediments only slightly correlates with the abundance of the DWAFs and with their taxonomic composition. The more visible features in the latest Albian agglutinated benthos concern relative proportions of foraminiferal morphogroups which correspond to life-style and feeding strategies, and in this way reflect changes in selected environmental parameters. It seems that fluctuations in the morphogroup distribution along the OAE1d succession reflects the influence of two groups of factors: (i) oxygen concentration in bottom waters (low in the older part of the OAE1d, with fluctuations in the younger part of this isotope event), and (ii) the organic carbon flux that was linked to the onset of a massive redeposition of biogenic material from the European shelf. The last factor is related to the sea level fall during the 3-rd order regressive cycle.
Water and nitrogen balance assessment for Krško polje aquifer case study in Slovenia
Authors: Curk Miha , Glavan Matjaž , Pintar Marina , Zupanc Vesna
Published: March 2021

Groundwater is the main source of drinking water in Slovenia, but nitrate pollution originating from agricultural activities as well as urban sources such as faulty sewage systems is threatening its quality in several areas of the country. One of such is the Krško-brežiško polje alluvial plain in the southeast. The main aim of this study was to assess the water and nitrogen balance for three common land-use types, as well as the whole area. Three field trial sites were set up to monitor water and nitrogen balance. Gaps in data were further evaluated by SWAT model simulations. Results will contribute to the existing knowledge of nitrate pollution pathways in the area, and strengthen understanding of land use and soil type’s influence on the process.

This work was funded by the Slovenian Research Agency project L4-8221 and IAEA TCP-SLO5004.
Overview of terrestrial water storage changes over the Indus River Basin based on GRACE/GRACE-FO solutions
Authors: Zhu Yu , Liu Shiyin , Yi Ying , Xie Fuming , Miao Wenfei
Published: March 2021

The Indus River Basin (the Indus) is facing the threat of great water shortages due to rapid population growth, expanding of irrigation area and increasing meltwater from snow and ice under the background of global warming. Being a less gauged basin, the effective usage of water resources in the Indus is always challenged by the high variability of the surface and ground water under a warming climate. This study therefore aimed to characterize and uncover the driving force of changes in water storage in the Indus based on GRACE and GRACE-FO solutions. A series of statistical techniques, such as EOF, modified STL, and Mann-Kenddall test, were applied to quantify and attribute the spatiotemporal patterns of the water storage dynamics. Our results demonstrated that (1) terrestrial water storage anomaly (TWSA) of the basin displayed a deficit and the deficit was largely concentrated in the middle and upper Indus plain (MUIP) during 2002 and 2020. (2) A slight decline in TWSA in the upper Indus basin (UIB) might be attributed to the accelerated melting of glacier and snow cover. (3) The excessive withdrawal of groundwater (1.57 mm/month) dominated the decrease of TWSA over the MUIP although weak increase of precipitation happened in the region. Anthropogenic activities imposed approximately 86.9% impact of the decrease in groundwater and this impact will aggravate for a long time if no effective water management schemes are taken. (4) Influenced by favorable meteorological conditions, the precipitation presented positive trend against the weakness of the India Summer Monsoon and the Westerlies, which exerted the positive influence on TWSA.
Salt morphologies and crustal segmentation relationship: new insights from Western Mediterranean Sea and other salt passive margins 
Authors: Bellucci Massimo , Aslanian Daniel , Moulin Maryline , Rabineau Marina , Leroux Estelle , Pellen Romain , Poort Jeffrey , Del Ben Anna , Gorini Christian , Camerlenghi Angelo
Published: March 2021

Salt tectonics at salt-bearing margins is often interpreted as the combination of gravity spreading and gravity gliding, mainly driven by differential sedimentary loading and margin tilting, respectively. Nevertheless, in the Western Mediterranean Sea, the classical salt tectonics models are incoherent with its morpho-structural setting: the Messinian salt was deposited in a closed system, formed several Ma before the deposition, horizontally in the entire deep basins, above a homogenous multi-kilometre pre-Messinian thickness. The subsidence is purely vertical in the deep basin, implying a regional constant initial salt thickness, the post-salt overburden is homogenous and the distal salt deformation occurred before the mid-lower slope normal faults activation. Instead, the compilation of MCS and wide-angle seismic data highlighted a clear coincidence between crustal segmentation and salt morphology domains. The geometrical variation of salt structures seems to be related to the underlying crustal nature segmentation. Regional thermal anomalies and/or fluid escapes, associated with the exhumation phase, or the mantle heat segmentation, could therefore play a role in adding a further component on the already known salt tectonics mechanisms. The compilation of crustal segmentation and salt morphologies in different salt-bearing margins, such as the Santos, Angolan, Gulf of Mexico and Morocco-Nova Scotia margins, seems to depict the same coincidence. In view of what is observed in Western Mediterranean Sea, the heat segmentation influence in the passive margins should not be overlooked and deserves further investigation.
Investigating vegetation role on UHI with mechanistic modelling worldwide
Authors: Zhang Ziyan , Paschalis Athanasios , Mijic Ana , Meili Naika , Fatichi Simone
Published: March 2021

The urban heat island effect (UHI), defined as the temperature difference between urban areas and their surroundings, has been widely observed in many cities worldwide, impacting urban energy demand, citizen’s comfort and health. UHI intensities have been found to depend on background climate, and the urban fabric, including built (building thermal properties, heights, reflectance) and natural characteristics (vegetation cover, species composition, vegetation management). In this study, we focus on developing a global scale mechanistic understanding of how each of those properties alters the urban energy budget and leads to UHI development. To achieve this goal, we use the state-of-art urban ecohydrological and land-surface model (urban Tethys-Chloris) to perform a set of detailed UHI simulations for multiple large urban clusters across America, Europe and China in a 10-year time period (2009-2019), spanning a gradient of aridity, vegetation amount, and different compositions of the urban fabric. Model simulations were set up using the latest generation remote sensing data and climate reanalysis (ERA5). Using the simulations, we develop a paradigm of how UHIs develop worldwide, and propose viable solutions for sustainable UHI mitigation.
Detection of Fourth Generation Synthetic Halocarbons in the Upper Troposphere
Authors: Schuck Tanja , Meixner Katharina , van Velthoven Peter , O’Doherty Simon , Vollmer Martin , Engel Andreas , Zahn Andreas
Published: March 2021

Synthetic halocarbons are used for a wide range of applications, for example air conditioning or foam blowing. Many of them are long-lived greenhouse gases contributing to climate change and, in addition, may contribute to stratospheric ozone depletion if containing chlorine or bromine. Therefore, their production and use are regulated by the Montreal Protocol and its amendments. These long-lived halocarbons are increasingly replaced by a fourth generation of unsaturated short-lived halocarbons, the hydrochlorofluoroolefines (HCFOs) and hydrofluoroolefines (HFOs). The main removal process of these compounds in the atmosphere is reaction with OH radicals, and their average lifetimes are of the order of up to a few tens of days.

As part of the IAGOS-CARIBIC instrument package we operate an automated air sample collection system during regular flights in the upper troposphere and lowermost stratosphere. At altitudes around 10-12 km, samples are collected in stainless steel and glass flasks at predefined times. Post-flight laboratory analyses include gas chromatography - mass spectrometry measurements of a wide range of halocarbons. The short-lived compounds HFO-1234ze(E) and HCFO-1233zd(E) were detected in a small number of samples, indicating that these compounds are sufficiently long lived for transport into the upper troposphere. There were not found in stratospheric samples.

At this altitude, low abundance of OH and low temperatures may slow down chemical decay, and tracer lifetimes may increase significantly. Based on average temperatures and OH abundance, we estimate local lifetimes of HFO-1234ze(E) and HCFO-1233zd(E)  in the mid-latitudes of up to 75 days and 200 days, respectively. Short-lived H(C)FOs reaching the upper troposphere could thus be transported over large distances and their degradation products may be deposited  far from their emission sources.
Unusual enhancement of ~30 MeV proton flux in an ICME sheath region
Authors: Oka Mitsuo , Obara Takahiro , Nitta Nariaki , Yashiro Seiji , Shiota Daikou , Ichimoto Kiyoshi
Published: March 2021

In gradual Solar Energetic Particle (SEP) events, shock waves driven by coronal mass ejections (CMEs) play a major role in accelerating particles, and the energetic particle flux enhances substantially when the shock front passes by the observer. Such enhancements are historically referred to as Energetic Storm Particle (ESP) events, but it remains unclear why ESP time profiles vary significantly from event to event. In some cases, energetic protons are not even clearly associated with shocks. Here we report an unusual, short-duration proton event detected on 5 June 2011 in the compressed sheath region bounded by an interplanetary shock and the leading-edge of the interplanetary CME (or ICME) that was driving the shock. While <10 MeV protons were detected already at the shock front, the higher-energy (>30 MeV) protons were detected about four hours after the shock arrival, apparently correlated with a turbulent magnetic cavity embedded in the ICME sheath region.