bluuebunny/crossref_metadata_2025 huggingface dataset:
A kink in the plate boundary, rotation and transtension: new 4d insights into the tectonics of the southern Dead Sea Transform
Authors: Fedorik Jakub , Afifi Abdulkader , Zwaan Frank , Schreurs Guido
Published: March 2022

The southern Dead Sea Transform (SDST) is an active left-lateral transform plate boundary that extends from the Sinai triple junction to the Lebanon restraining bend, separating the Arabian and Sinai plates. In this study, we analyze structural variations along the SDTS, and reproduce these variations in a 4D analogue model.  

From south to north, the structural styles along the SDTS indicate (1) rotational transtension within the Gulf of Aqaba, (2) pure strike-slip in Wadi Araba and Jordan River valley, and (3) pull-apart basins in the Dead Sea, Sea of Galilee and Hula basin. These different structural styles were replicated experimentally in an analogue model incorporating transtension with minor rotation along a kinked plate boundary. Our 4D model produced a deep southern depression with en echelon faults corresponding to the Gulf of Aqaba, a simple strike-slip fault system without vertical displacement reflecting the Wadi Araba and Jordan Valley, and a set of pull-apart basins reminiscent of the Dead Sea, Sea of Galilee and Hula basins. The accurate reproduction of the structural styles along this 600km-long plate boundary segment constrains the relative movement between the Arabian and Sinai plates to a simple combination of transtension with minor rotation, thereby negating the earlier hypothesis of Euler pole shift during the tectonic evolution of the SDST. 
Decoupling between fluvial aggradation-incision dynamics and paleo-denudation rates during the last glacial cycle, Crete, Greece
Authors: Ott Richard , Scherler Dirk , Wegmann Karl , D'Arcy Mitch , Ivy-Ochs Susan , Christl Marcus , Vockenhuber Christoph
Published: March 2022

The impact of Quaternary climate cycles on denudation as well as fluvial aggradation and incision is debated, especially in regions that did not experience glaciation. Here we present a record of paleo-denudation rates, and geochronologic data constraining aggradation and incision from the Sfakia and Elafonisi alluvial sequences on the island of Crete, Greece. We report seven new optically stimulated luminescence (OSL) and ten new radiocarbon ages, as well as eight 10Be and eight 36Cl denudation rates from modern and terrace sediments. At the Elafonisi fan system, we identify four periods of aggradation, where marine isotope stages (MIS) 2, 4, and likely 6 correspond to aggradation periods, and MIS 1, 3, and likely 5e are characterized by incision. The dating of paleoshorelines indicates constant uplift over the past 71 ka, at rates of 1.2 mm/a. Aggradation occurred throughout the entire glacial cycle at the Sfakia fan, followed by up to 50 m of incision in the past 10 ka. Chronological constraints indicate that aggradation rates were particularly high during MIS 2 and 4, analogous to the Elafonisi fan system. However, our paleo-denudation rates indicate mostly constant denudation throughout the past 80 ka; with only two samples indicating an up to 50% increase in paleo-denudation rates compared to modern rates. Nearby climate and vegetation records show that MIS 2, 4, and 6 were characterized by cold and dry climate with sparse vegetation, whereas forest cover and wet conditions prevailed during MIS 1, 3, and 5. Our data suggest that variations in climate and vegetation cover were not sufficient to markedly alter landscape-wide denudation rates, but that changes in hydroclimate and vegetation exerted a strong control on the aggradation-incision behavior of the drainages. During relatively cold stages, low vegetation cover and river sediment transport capacity led to aggradation, whereas the increased river transport capacity during relatively warm stages caused subsequent incision. We therefore hypothesize that the studied catchments show a decoupling between transport-limited streams responding to climate forcing and near-steady hillslope denudation.
Atmospheric microplastics over ocean: abundance, distribution and transport
Authors: wang xiaohui
Published: March 2022

Atmospheric transport was considered as an important pathway through which MPs (microplastics) enter the ocean since the early 2019s, but the source, transport, and fate of atmospheric MP have not well known. Besides, the connection between terrigenous atmospheric MP emissions and impacts over the ocean is not well known. In this conference, we will present our research about the variations of atmospheric MP over the ocean based on the three transoceanic survey, include the west Pacific Ocean, south china sea and east Indian ocean. Results suggest that synthetic MP comprised 25.89 % of total atmospheric particles over the west Pacific Ocean, with most being cotton and cellulose (51.68%). We found that the atmospheric MP was sparsely distributed over ocean, with different characteristics. The mean abundance of atmospheric MP over the western Pacific Ocean during the sampling period were 0.841 ± 0.698 items/100 m3. The abundance of atmospheric MP over the Pearl River Estuary (4.2 ± 2.5 items/100 m3) was significantly higher than that over the East Indian Ocean (0.4 ± 0.6 items/100 m3). However, the abundance of atmospheric MP in the SCS (0.8 ± 1.3 items/100 m3) was not significantly different from the East Indian Ocean and Pearl River Estuary. Results indicated that the size of airborne MP fiber over ocean is probably not the limiting factor during the long-range transport. Research reveal that MP undergoes long-range transport, more than 1000 km away. Furthermore, backward trajectory model analysis preliminary showed the potential sources of atmospheric MP over ocean. Our study provides the better understanding on the impact of atmospheric transport on global plastic cycle.
Geopotential measurement with a robust, transportable Ca+ optical clock
Authors: Huang Yao , Guan Hua , Gao Kelin
Published: March 2022

We present a robust, transportable Ca+ optical clock, with a systematic uncertainty of 1.3 × 10−17 limited
by the black-body radiation (BBR) field evaluation and an uptime rate of >75% over a 20-day period. The
clock is then installed in an air-conditioned car trailer, making it more convenient for applications. Referenced
to a stationary laboratory clock, geopotential measurements are made with the transportable clock with a total
uncertainty of 0.33 m (statistically 0.25 m and systematically 0.22 m) and agree with the spirit level measurement.
After being moved >1200 km, the absolute frequency of the Ca+ optical clock transition is measured
as 411 042 129 776 400.41(23) Hz, with a fractional uncertainty of 5.6 × 10−16, which is about one order
of magnitude smaller than our previous measurement. The transportable built can be used for sub-meter-level
elevation measurements, comparing intercontinental optical clocks, verifying basic physical theories, etc.
Heat transfer across scales: from single fractures to fracture networks
Authors: Heinze Thomas
Published: March 2022

Temperature estimation in hydrothermal reservoirs is a critical point for the feasibility of geothermal projects and subsequent processes, such as chemical and biological activity as well as thermal stresses. As flowing fluid and surrounding host rock locally diverge in temperature until equilibrium occurs, heat transfer between phases needs to be described. However, this is a challenging task, especially in fractures, because the heat transfer coefficient depends on various parameters, such as flow velocity and aperture. Heat transfer characteristics in fracture networks, and their dependence on fracture network characteristics, have been rarely studied so far.

Starting from a newly developed analytical solution of heat transfer in single fractures, a consistent formulation for heat transfer in fractured reservoirs is presented. Using an intermediate step of bench-scale experiments, the sensitivity of the temperature field in the fracture network with respect to the heat transfer coefficient is investigated. Due to multiple flow paths within a reservoir, the heat transfer capabilities of individual fractures can become less relevant in well-connected reservoirs. On the other hand, single fractures with uncommon velocity or aperture values can cause local heterogeneities in the temperature field due to the velocity-dependent heat transfer.

Bridging the gap between well-defined networks with a limited number of fractures and large-scale fracture networks of arbitrary shape requires a change in the parameters used. On large scale, effective values such as fracture density and anisotropic permeability are more suitable and accessible than single fracture apertures. To incorporate such a change in parameterization, a new theoretical framework based on the assumption of fracture networks with a regular geometry is presented.

The presented work sheds new light on the heat transfer mechanisms in fractures and fracture networks and is the first attempt to derive a consistent mathematical framework for heat transfer in fractures across scales.
Climatology and Spatial Patterns of Cloud Shadows and Irradiance Peaks
Authors: Mol Wouter , Heusinkveld Bert , Knap Wouter , van Heerwaarden Chiel
Published: March 2022

Surface irradiance variability is present on many spatio-temporal scales, but most strongly on the scale of minutes to seconds due to low broken clouds. Fast and large fluctuations, or spatial heterogeneity, of irradiance affects solar energy production. In idealised settings, let alone in operational forecasts, the modelling of realistic fields of surface irradiance in the presence of clouds is challenging. It relies on realistic cloud fields, is computationally demanding due to the nature of 3-d radiative transfer models, and ultimately requires observations for validation. Dense spatial observation of irradiance on the scale of cloud shadows or solar energy parks are rare, however. Even 1-d time series are often not available at high enough resolution. 

In ongoing work, we provide those missing observations. I will present our gathering and analyses of new and detailed observations of surface irradiance to address knowledge gaps in our physical understanding and provide validation datasets for models. In 2021, we deployed a dense network of custom, low-cost radiometers at two field campaigns, FESSTVaL (Germany) and LIAISE (Spain), to observe spatial patterns of irradiance driven by clouds. The instruments are able to closely match expensive conventional instruments, and combined with skyview imagery, the spatial observations are directly linked to observed clouds. To complement these short term spatial data, long-term statistics of irradiance variability are derived from a 10-year 1 Hz resolution data from the Baseline Surface Radiation Network station in Cabauw, the Netherlands. Distributions and typical spatio-temporal scales of cloud shadows and irradiance peaks can be related to cloud type and meteorological conditions. The gathering and study of these datasets will lead to a better understanding of the physics, help validate models, and ultimately improve our ability to accurately forecast irradiance variability at the small scales.
The Recipes for Earth Sciences Go Trilingual: MATLAB, Python and Julia
Authors: Trauth Martin H.
Published: March 2022

It’s been almost 30 years since I started with MATLAB, coming from FORTRAN77, and at a time when Python was still in its infancy and 20 years before Julia was developed. However, I recognize the popularity of Python, including the growing prevalence of Julia, and find that a bilingual and trilingual version of my MATLAB-based books and my courses could be beneficial. I’ve been learning Python for a few months now, with the goal of writing a Python version of my first book, MATLAB Recipes for Earth Sciences, 5th Edition (Springer 2021). In the meantime, almost all chapters of the book, with topics such as time series analysis, signal processing, digital terrain analysis and image processing, have been translated from MATLAB into Python, some also into Julia. Using the trilingual code in a master's course shows an unexpected but extremely positive side effect: students get away from a particular software or programming language, and focus instead on the method they want to implement. In addition, solutions often use mixtures of programming languages, exploiting the advantages of each. This is an advantage, also helps a lot to produce sustainable and reproducible code. Furthermore, this approach makes the students fit for a job in academia or industry, where other software tools are used than the ones we use in class. Here, I will share my experiences with courses on data analysis in earth sciences with 2–3 programming languages and with translating a data analysis book from one to another programming language.
Improving atmospheric angular momentum forecasts by machine learning
Authors: Dill Robert , Saynisch-Wagner Jan , Irrgang Christopher
Published: March 2022

Earth angular momentum forecasts are naturally accompanied by forecast errors that typically grow with increasing forecast length. In contrast to this behavior, we have detected large quasi-periodic deviations between atmospheric angular momentum wind term forecasts and their subsequently available analysis. The respective errors are not random and have some hard to define yet clearly visible characteristics which may help to separate  them from the true forecast information. In order to implement an automated forecast correction we tested several machine learning methods. We found, that a cascading forward neural network model performed best in this problem. A total error reduction with respect to the unaltered forecasts amounts to about 30% integrated over a 6 day forecast period. Integrated over the initial 3 day forecast period, in which the largest artifcial errors are present, the improvements amount to about 50%. After the application of the neural network, the remaining error distribution shows the expected growth with forecast length. However, a hourly modulation and an remaining initial baseline error became evident that were hidden before under the larger forecast error.
Particle size segregation in debris flows: insights from simulations of immersed sheared granular flows
Authors: Cui Kahlil Fredrick , Zhou Gongdan , Jing Lu
Published: March 2022

During the course of a debris flow’s motion, large particles, such as rocks and boulders, rise to the free-surface while the finer sand and silt-sized particles settle to the base. This inverse-grading process influences the development of coarse-grained heads and levees in debris flows that consequently enhance the flow mobility. Size segregation is well-studied in dry granular flows wherein it is found to be highly efficient and results in sharply separated layers of differently sized particles. Segregation diminishes in the presence of pore fluids (i.e. water or muddy slurry) and in some cases is no longer evident, although the mechanisms behind this inhibitive effect is poorly understood. In order to accurately capture size segregation in debris flows, and its impacts on the flow dynamics, it is important to understand how different types of pore fluids influence the segregation process. In this research, we systematically investigate the effects of various interstitial fluids, characterized by their density and viscosity, on the rate of particle size segregation through coupled granular-fluid simulations. Debris flows are simulated as sheared granular mixtures composed of spheres having two distinct particle sizes, immersed in ambient fluids. Solid and fluid interactions are modelled through drag and buoyant forces. Fluid effects are also evaluated across different shear rates, confining pressures, mean diameters, and gravity. It is found that the segregation slows down as the fluid viscosity is increased, but is unaffected by it below certain threshold values. In the low viscosity limit, segregation is affected only by the relative density between the particles and the fluid, and by flow inertial conditions. Analysis of stresses acting on a segregating particles reveals that the decrease of segregation rates with the viscosity is due to the increase of fluid drag forces which effectively weaken the contact stress gradients and velocity fluctuations responsible for driving the large particles upward. An empirical scaling formula is developed which accounts for the effects of fluid viscosity and the relative density on size segregation immersed in different fluids.
Coupled surface and groundwater modeling for the analysis of management options in groundwater affected catchment areas
Authors: Tix Mauritius
Published: March 2022

In this project a water management concept for the southern Randowbruch is developed, which meets the climate protection goals according to the Climate Protection Plan 2050 of the German Ministry of Environment regarding a comprehensive moor protection in the Randowbruch. The paper forms the basis for the realization of a management concept and deals in particular with the analysis of the special characteristics of the catchment area and the possible management options with the current management system. The catchment area of the Randow has a long and highly anthropogenic influenced history of melioration. The moor, which formed during the Vistula Ice Age around 18,000 years ago in the washout channel of a glacier, has been continuously drained and made agriculturally usable throughout the past 300 years by targeted human interventions. The moor was drained by ditches installed along the original main receiving water, the Randow, and dams to control water levels for agricultural use. The draining measures reached their peak in the 60s and 70s of the 20th century and have remained unchanged since. Taking into account the intensive interaction between groundwater and surface water in this area, the analysis of this catchment with a hydrological model is only possibly by including this interaction. The primary process of this interaction is the exfiltration of groundwater into the system of ditches, as well as the infiltration of water back into the groundwater. Thus, the evaporation and in particular the water levels of areas with high levels of groundwater and the adjacent ditches represent the essential boundary conditions for the exchange of the two hydrological units. Therefore, the basis for the development of the management concept is a coupled model of ArcEGMO and FEFLOW, with FEFLOW modeling the groundwater flow and ArcEGMO simulating the hydrologic balance and the complex system of water bodies. 

Keywords: 

coupled modeling, ArcEGMO, FELFOW, water resource management, moor protection 
On-site floral resources and surrounding landscape characteristics impact pollinator biodiversity on solar parks
Authors: Blaydes Hollie , Potts Simon , Whyatt Duncan , Armstrong Alona
Published: March 2022

As solar photovoltaic make a greater contribution to the energy mix, there will be increasing land use change for solar parks. Land use change can affect biodiversity across spatial scales and opportunities to incorporate biodiversity benefits into the energy transition are increasingly being recognised. For example, solar parks could support insect pollinators through providing critical resources such as flowering plants. However, understanding of pollinator response to solar park developments is currently limited and empirical data are lacking. To address this knowledge gap, we surveyed bumble bees, butterflies and flowering plants between July and September across 15 solar parks in the UK. We also investigated the composition and connectivity of the landscapes surrounding each solar park using landcover data and a GIS, allowing us to explore the impacts of on-site floral resources and surrounding landscape characteristics on bumble bee and butterfly abundance and diversity. We found that bumble bee and butterfly biodiversity varied across solar parks, but overall butterflies were more than five times more abundant than bumble bees. Pollinator biodiversity was impacted by both on-site resources and landscape characteristics. However, characteristics of the floral resources on site appeared to be the most important factors, with increases in floral diversity, floral cover and vegetation height associated with increases in pollinator abundance and diversity. Our findings suggest that local and landscape scale factors affect pollinator biodiversity on solar parks, but solar parks that provide diverse and abundant flowering plants may be best placed to support pollinators. Incorporating this knowledge into existing and future solar park developments could promote benefits to insect pollinators alongside the energy transition.
Spatial and temporal variability of soil moisture in land-use legacy forest soils in Brandenburg, Germany
Authors: Schneider Anna , Bonhage Alexander , Raab Alexandra , Raab Thomas
Published: March 2022

Soil physical properties can show high heterogeneity in forest soils, implying a high spatial variability of soil moisture and plant water availability. Legacy effects of past land use, resulting in a small-scale mosaic of anthropogenically modified and unmodified soils in forest areas, further increase this spatial heterogeneity. The soils associated with relict charcoal hearths (RCH), most prominently characterized by a technogenic layer rich in charcoal fragments, are a widespread example for such land use legacy soils in forest areas. 

The objective of our study was to characterize the soil moisture regime of forest soils and RCH soils on sandy substrates in the northeastern German lowlands; and in particular to assess the long-term effect of the prolonged summer drought period in 2018 on spatial and temporal variability of soil moisture. We monitored matric potentials, soil water contents and soil temperature from June 2018 in forest soils in the Tauersche Forst (Brandenburg, Germany). Three soil profiles (one reference forest soil profile and two characteristic RCH soil profiles) were instrumented, sampled for laboratory analyses of bulk density, pore size distribution, saturated hydraulic conductivity, and persistence of water repellency; and root density distribution in the profiles was recorded. 

The soils in all profiles show low porosity and plant available water contents. On RCH soils, overall porosity is clearly higher compared with the reference soils, mainly related to larger volumes of coarse and fine pores. Soil moisture monitoring shows very high spatial and temporal variability of the recorded data after the prolonged dry period in 2018, with gradual rewetting over the winter periods and only short-term fluctuations of soil moisture in reaction to high-intensity precipitation events in the summer periods. The comparison of in-situ and laboratory-based water retention data shows strong hysteresis effects during the rewetting, with increasingly clear reactions of soil water contents to precipitation events over the years following the dry period, especially in the charcoal-rich substrates. The differences in soil moisture between the dry and the wetter periods were clearly higher in the RCH soils, which, compared with the reference soils, showed higher water contents under wet conditions and lower water contents under dry conditions. The results affirm that land use legacies can clearly increase the spatial and temporal variations of soil moisture in forest areas.
Temperature impact on viticulture phenological stages in Croatia under present climate condition
Authors: Omazić Branimir , Blašković Lucija , Telišman Prtenjak Maja , Prša Ivan , Karoglan Marko
Published: March 2022

As many studies shows, temperature is key element that affects grapevine growth. Global warming and temperature rise shifted grapevine phenology in many vineyard regions worldwide. Also, temperature and precipitation extremes can effect wine quality and yield. In Croatia, viticulture represents one of the most important branches of agriculture in the economical and traditional sense. Therefore, it is important to study changes in vine growth, as well as impact of meteorological parameters on it, so that it can be used to predict suitability and growth under future climate.

In this study, dates of beginning of 3 phenological phases (budburst, flowering and veraison), as well as harvest dates, collected from wineries across country, were analyzed. Results show earlier appearances of almost all phases, regardless of variety. With rise of temperature, the duration between two phases is shorted and that leads to an earlier harvest.

Also, 5 agrometeorlogical indices (Growing degree day, Winkler index, Huglin index, Cool night index and Dryness index) in two 30 year long period (1961-1990, 1991-2020) were calculated from meteorological data collected from 74 meteorological stations in Croatia. A spatial interpolation was applied on results and maps were made at 1-km resolution. Maps show significant changes in temperature indices between two periods. This raises the possibility of growing new varieties in certain regions, but also hints that grapevine could be cultivated in new regions.

In addition, temperature impact on the phenological phases is studied. Relationship between begging of the phases and mean daily temperate averaged over period that precede is calculated. Also, multi-linear regression between start dates of phenological phases and monthly averages of minimum, maximum and mean temperature is calculated, so that the best correlation could be determined. Results show a good correlation between dates and temperature, which can be valuable indicator for even more significant changes in vine growth in future.
Investigating global and regional sea level budgets by combining GRACE(-FO) and altimetry data in a joint fingerprint inversion
Authors: Uebbing Bernd , Rietbroek Roelof , Kusche Jürgen
Published: March 2022

Sea level change affects hundreds of millions of people living in coastal regions. In addition to measuring the total sea level change via satellite altimetry, it is important to understand individual mass and steric contributors on global and regional scales. Consequently, deriving accurate global and regional sea level budgets is of key interest for understanding the underlying processes and aid in assessing future impacts of sea level rise. Furthermore, steric sea level change is related to the Earth’s Energy Imbalance and thus a key indicator of global warming.

The global fingerprint inversion method (Rietbroek et al., 2016) allows to combine GRACE(-FO) gravity measurements and along-track satellite altimetry observations in order to jointly estimate the individual mass and steric changes in a consistent manner. We use an extended fingerprint approach which allows further separation of the ocean mass variations into contributions from the melting of land glaciers and the Greenland and Antarctic ice-sheets as well as terrestrial hydrology effects and changes of the internal mass transport within the ocean. Furthermore, the updated inversion presented here, aims at splitting the steric sea level change into contributions of the upper 700m and the deeper ocean.

Here, we present the inversion results of a closed global sea level budget (within 0.1 mm/yr) during the GRACE era (2002-04 till 2015-12) attributing 1.68 mm/yr and 1.40 mm/yr to ocean mass and steric changes, respectively. Compared to state-of-the art studies the steric contribution is found to be in line while the mass estimates are slightly lower. We provide budgets for major ocean basins and compare our results to individually processed GRACE, altimetry and ocean re-analysis datasets as well as published estimates. Furthermore, we will show preliminary results when extending the inversion to incorporate additional GRACE-FO data. Finally, we extent our investigations to regional sea level budgets for selected regions of interest, such as the Bay of Bengal or the North Sea, which are dominated by completely different sea level components.
Advances in electromagnetic imaging in the presence of well casings: algorithms and field experiments
Authors: Streich Rita , Orujov Gurban , Swidinsky Andrei
Published: March 2022

Controlled-Source Electromagnetic (CSEM) methods have the potential to be powerful geophysical tools for imaging and monitoring the distribution of electrically resistive fluids, such as freshwater aquifers, CO2 injected into the subsurface or hydrocarbons during oil and gas production.  However, the presence of metallic infrastructure (steel well casings, pipelines etc.) presents an enormous challenge, because the highly conductive metal masks the electromagnetic response of subsurface geology and distorts any associated time-lapse changes. Therefore, numerical techniques to predict and mitigate the contamination caused by pipelines and casings on CSEM surveys are critical for real world imaging and 4D applications near any such metal objects.

In a collaborative project between the Colorado School of Mines and Shell, we have developed CSEM modeling and inversion tools that can handle realistic scenarios with multiple vertical as well as deviated casings and complex pipeline networks, as will be encountered in mature oil field environments. First, we implemented a forward modeling code based on the Method of Moments technique, which effectively turns the casings into extra sources, such that we do not need to discretize them into excessive numbers of very small model cells. We used this modeling tool to demonstrate quantitatively how steel casings impact synthetic and real time-lapse EM data. The forward modeling code was then combined with a newly developed Gauss-Newton inversion engine, which by itself has been demonstrated to provide images of superior resolution, depth penetration and data fit with less dependency on initial conditions compared to previous quasi-Newton inversion engines.

In this contribution, we first demonstrate on synthetic data that the combination of these two algorithms provides high-quality electrical resistivity images in the immediate vicinity of well casings. Then, we show encouraging results of applying the new tools to field trial data acquired over known casings under semi-controlled conditions. The images obtained are nearly free of casing imprint and subsurface geology could be recovered. These results suggest that this technology may enable us to explain severely distorted field data that were previously uninterpretable.
Terrestrial nutrient exports and environmental changes explain eutrophication trends in fifty large lakes of Yangtze Plain, China
Authors: Guan Qi , Tang Jing , Feng Lian , Olin Stefan , Schurgers Guy
Published: March 2022

Over the past two decades, lakes in Yangtze Plain have suffered from serious eutrophication, in some regions with increased frequency of cyanobacteria blooms over years. In this study, we investigated the underlying causes of eutrophication using a combination of process-based ecosystem modelling and statistical data analysis. We found that terrestrial nutrient exports with runoff have significantly increased from 1979 to 2018 in Yangtze Plain, directly linked to the enhanced usage of chemical fertilizer for crops. Based on statistical analyses of environmental variables, terrestrial nutrient exports and satellite-observed probability of eutrophication occurrence (PEO), we separated the studied fifty lakes into five classes with similarities in environmental and nutrient variations, and attributed key factors in controlling the temporal changes of PEO. The results showed that the satellite-observed PEO trends in five classes could be largely linked to the terrestrial nutrient exports and environmental changes. Specifically, we found agricultural activities can explain the observed eutrophication trends in western lakes where lake catchments are dominated with arable and natural land, and the reduced discharge of industrial wastewater was found to be linked to the declining trends in eutrophication for eastern lakes where the green growth of industrialization were promoted from 2003 to 2011. These findings highlight the importance of sustainable management of agriculture and industrialization to overcome eutrophication issues in this region.
New mapping of the Afar Depression: towards the better understanding of rift dynamics in a hotspot-influenced continental rift zone
Authors: Rime Valentin , Foubert Anneleen , Atnafu Balemwal , Kidane Tesfaye
Published: March 2022

The Afar Depression forms a triple junction between three rift systems: the Red Sea Rift, the Gulf of Aden Rift and the Main Ethiopian Rift. Rifting began in the Oligocene after the eruption of the Ethiopian Flood Basalts. It represents a unique modern example of hotspot-influenced continental breakup. Its emerged position allows detailed field and remote sensing investigations. Important mapping efforts in the area during the 60s and 70s provided very valuable input for the understanding of the local geology but also for the development of global tectonic, volcanological and sedimentary concepts in continental rift settings.

This study presents the compilation of a new geological map which covers the complete Afar depression and includes its Phanerozoic sedimentary and magmatic cover. The map is based on extensive literature research, remote sensing and fieldwork. The geological history of the Afar Depression has also been reviewed. The map evidences the complexity of the rift system with the interaction of distinct tectonic plates, blocks, rift segments, sedimentary basins and volcanic areas that evolve through time and space. This integrative geological map and review is used to reassess and discuss aspects of the style, evolution, kinematics and dynamics of this rift system. Studying this unique modern example of active rifting will help in the better comprehension of rift processes and passive margin development worldwide.
Investigation of the applicability of rainfall generators for the estimation of the rainfall erosivity for ungauged locations
Authors: Bezak Nejc , Pidoto Ross , Müller-Thomy Hannes , Shehu Bora , Callau-Beyer Ana , Zabret Katarina , Haberlandt Uwe
Published: March 2022

Rainfall erosivity is one of the main inputs for soil erosion modelling. Long high-resolution rainfall time series are needed for the estimation of rainfall erosivity but these are likely to be lacking at many locations around the globe. An alternative approach could be the generation of synthetic rainfall time series using stochastic rainfall models. In this study, four methods for estimating the rainfall erosivity were evaluated at ungauged sites:

i) estimation from regionalised observed 5 minute rainfall time series,

ii) direct regionalisation of the rainfall erosivity estimated from observations,

iii) estimation from 5 minute rainfall time series disaggregated from daily observations,

iv) estimation from rainfall time series generated by a regionalized stochastic rainfall model.

Data from 159 stations from Lower Saxony, Germany, were used to evaluate the performance of different methods. All tests were performed using the leave-one-out cross validation method. Additionally, we also analysed the minimum time series length necessary to adequately estimate the rainfall erosivity.

The results indicated that the direct regionalization of the mean annual rainfall erosivity yielded the best performance in terms of relative bias followed by the regionalization of the 5 minute rainfall data. However, the main advantage of the rainfall generators is that they can generate long synthetic time series and can also provide estimates of other rainfall erosivity characteristics such as number of erosive rainfall events, etc. Applying the alternating renewal model indicated that more than 60 years of data are needed to obtain a stable estimate of rainfall erosivity and that rainfall erosivity estimations using 5 years of data can lead to significant uncertainty. Moreover, it was also found that the rainfall erosivity calculations are sensitive to the resolution of the input data.  

Acknowledgment: The results of the study are part of the bilateral research project between Slovenia and Germany “Stochastic rainfall models for rainfall erosivity evaluation” (BI-DE/18-19-008). 
Applying artificial intelligence in modeling the relationship of tree ring growth index with different climate variables
Authors: Salehnia Nasrin , Ahn Jinho
Published: March 2022

Trees are one of the best sources of high-resolution proxy data to understand the past climate. By analyzing Tree Ring Width (TRW) data with climate variables and indicators, we can find main clues, which can help us to encode paleoclimate signals. Nowadays, scientists try to model TRW data with various climate data versus reconstructing the mentioned data for an extended period through different statistical methods. One of the newest methods is AI (Artificial Intelligence). This study aimed to model TRW data with the most effective climate variables by comparing the statistical methods vs. the AI method. First, seven climate variables were gathered from the nearest synoptic station (Sokcho) to the TRW site (Whachae Peak-Sorak), in northeast South Korea, during 1901–1998. The climate variables include maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tm), diurnal temperature range (DTR = Tmax – Tmin) (°C), precipitation (Pr) (mm), and vapor pressure (VP) (hPa). The in-situ data were applied to correct the Climate Reach Unit (CRU, Version 4.03). Moreover, we have checked two meteorological drought indices, namely the Palmer drought index (PDSI) and standardized precipitation index (SPI). We applied two regression methods (namely multiple linear regression (MLR) and stepwise regression (SR)) and one AI (Nonlinear autoregressive with exogenous input (NARX)) method. In the first step of analyzing data, we did not see any specific significant results for the relationship between drought effects and TRW data in the case study. Then in the second step, modeling continued with the climate variables. Finally, the results demonstrated that among the three used methods, the NARX method achieved the best outcomes, as MLR with r = 0.44 (p < 0.003); SR with r = 0.27 in p < 0.001; and the NARX model was the best outcomes with r = 0.78. This study revealed that regression methods were not strong enough to reconstruct TRW data. Whereas, by noticeable results, the AI method has obtained the best performance.    
Revealing unexpected sources and quantities of groundwater discharge into major river systems during drought conditions
Authors: Zill Julia , Siebert Christian , Rödiger Tino , Weitere Markus , Mallast Ulf
Published: March 2022

The understanding of groundwater interactions with riverine systems is of utmost importance for ecosystem assessment and management. Diffuse groundwater born nutrients, such as N, P and C contribute significantly to an increase of algae growth in rivers and eventually in estuaries, leading to eutrophication with severe consequences for water quality and ecosystem health. Thus, knowledge of both location dynamics and temporal dynamics of diffuse groundwater discharge areas, as well as the discharging groundwater quantity are required.

Here we provide a multi-methodological approach to gain this information for a large river in Germany, i.e. the Elbe River. We applied complementary methods to a 450 km long stretch including: i) analysis of daily time series of hydraulic gradients between river- and groundwater levels, ii) a flux balance for river segments spanning between neighboring gauging stations, iii) inverse geochemical modeling of the river water composition for each segment, and iv) a Darcy approach as an additional tool based on the hydraulic conductivity of the upper aquifer. The results are manifold, including a spatiotemporal answer to the dynamics and orientation of groundwater interaction with the Elbe.

Groundwater inflow is variable but occurs along the entire river. Areas of high groundwater contribution are located in the upstream mountainous parts, where groundwater makes up to 11% of the total river flow. Further downstream, groundwater inflow decreases, while inversion of hydraulic gradients indicate an immense infiltration of river water into the river banks. Unexpectedly high input of groundwater-like fluids could be detected in the lowland, where geochemical modeling indicated a massive inflow of water in a magnitude of 10% of the total river flow. Given a missing surface and groundwater contribution, an unidentified but apparently large system of subsurface drainage ditches co-exists, which transports water to the Elbe River efficiently during and due to drought-related low flow conditions.

Gaining insight into such a large-scale setting with interfering surface water contributions, effluents of wastewater treatment plants, and diffuse groundwater in- and outflows was possible only by applying the combination of independent geochemical, hydraulic and balancing approaches. With a similar availability of river and well levels and the physical access to the latter, the presented multi-method approach may provide a blueprint for the assessment of other large river systems.
Trees Talk Tremor—Wood Anatomy and δ13C Content Reveal Contrasting Tree-Growth Responses to Earthquakes
Authors: Mohr Christian , Manga Michael , Helle Gerhard , Heinrich Ingo , Giese Laura , Korup Oliver
Published: March 2022

Large earthquakes can increase the amount of water feeding stream flows, raise groundwater levels, and thus grant plant roots more access to water in water-limited environments. Here, we quantify growth and photosynthetic responses of Pinus radiata plantations to the Maule Mw 8.8 earthquake in geometrically simple headwater catchments of Chile's Coastal Range. To this end, we combine high-resolution wood anatomic (lumen area) and biogeochemical (δ13C of wood cellulose) proxies of daily to weekly tree growth sampled from trees on valley bottoms and close to ridge lines. We find that, immediately after the earthquake, at least two out of six tree trees on the valley floor had enlarged lumen area and lowered δ13C, while trees along the hillslope ridge had a reverse trend. Our findings favor a control of soil water on this response, largely consistent with models that predict how enhanced postseismic vertical soil permeability causes groundwater levels to rise on valley floors, but fall along the ridges. Statistical analysis with non-parametric boosted regression trees reveals that streamflow discharge gained importance for photosynthetic activity on the ridges, but lost importance on the valley floor after the earthquake. We conclude that earthquakes may stimulate ecohydrological conditions favoring tree growth over days to weeks by triggering stomatal opening. The weak and short-lived signals that we identified, however, imply that such responses are only valid under water-limited, rather than energy-limited tree, growth. Hence, dendrochronological studies targeted at annual resolution may overlook some earthquake effects on tree vitality.
Predictability of the Southern Ocean dynamics through ensemble simulation hindcasts
Authors: Zanchettin Davide , Pierini Stefano , Aliani Stefano , Rubino Angelo , Zambianchi Enrico , Viana Barreto Ricardo , de Ruggiero Paola , Colella Alessio
Published: March 2022

The Southern Ocean (SO) dynamics, and the various fronts of the Antarctic Circumpolar Current in particular, are well known to display a very energetic variability covering a wide range of spatial and temporal scales. Since a substantial fraction of such variability is known to be intrinsic, and therefore basically chaotic, predictability in this part of the world ocean is particularly poor.

In this context, the YOPP-endorsed IPSODES project of the Italian “Programma Nazionale di Ricerche in Antartide” (PNRA) is aimed at improving process understanding concerning the predictability of the SO dynamics through ensemble simulation (ES) hindcasts analyzed by means of various statistical techniques supported by dynamical interpretations, with special focus on multiscale interactions linking high-frequency (up to seasonal) and low-frequency (interannual and larger) variability. IPSODES uses existing state-of-the-art eddy-permitting global ocean-sea-ice model ESs and coupled global atmosphere-ocean-sea-ice model ESs developed for decadal climate predictions. Moreover, new ESs performed with an ocean model specifically developed for IPSODES are carried out: sensitivity numerical experiments to assess model uncertainty are performed with these new simulations. The study of transport of marine debris provides an application of such modelling effort, and contributes also to model validation through the use of an available valuable data set.

This contribution illustrates advances achieved so far in IPSODES towards improving our understanding of the predictability properties of oceanic variability of the SO dynamics.
Evolution of the DPRK5 and DPRK6 aftershock sequences: 2016 to 2022
Authors: Kitov Ivan
Published: March 2022

The first aftershock of the announced nuclear test conducted by the DPRK on 09.09.2016 was found by the detection method based on waveform cross correlation on September 11, 2016. This was the only aftershock which was found during the period between the first (09.10.2006) and the sixth (03.09.2017) DPRK tests, using the signals of the DPRK tests as waveform templates. The DPRK6 underground test with mb=6.1 generated a significant aftershock sequence, with some events detected at teleseismic distances. The aftershocks with the best signal quality were used as master events in the multi-master method, working as an active radar focused on the aftershock area. The multi-master method allowed to find more than 100 aftershocks, including 7 aftershocks of the DPRK3 and DPRK4. The aftershock sequence is still active, with 25 aftershocks detected between January 1 and December 10, 2021. The mutual cross correlation of the DPRK aftershocks revealed the presence of two sequences generated by the DPRK5 and DPRK6 cavity collapse. The length, intensity, and alternating character of these two sequences suggest specific mechanisms of energy release. Such a mechanism can be associated with the interaction of the damaged zones of the DPRK5 and DPRK6 and the collapse of their cavities with progressive propagation of the collapsing chimneys towards the free surface. The higher activity in 2021 indicates that the chimney collapse is not finished. We expect more aftershocks, possibly ended with the chimney reaching the free surface.