bluuebunny/crossref_metadata_2025 huggingface dataset:
Shallow Asthenospheric Volumes Beneath Cenozoic Volcanic Provinces in the Circum-Mediterranean: Evidence From Seismic Tomography And Integrated Geophysical-Petrological Thermochemical Modelling
Authors: El-Sharkawy Amr , Hansteen Thor H. , Clemente-Gomez Carlos , Fullea Javier , Lebedev Sergei , Meier Thomas
Published: February 2023

During the Cenozoic, the Circum-Mediterranean has experienced extensive and widespread igneous magmatism (i.e. intraplate, subduction-related and mixed-origin) that reflects the response of the upper mantle to the geodynamic evolution of this area. The exact origin of the volcanic activities and its relation to the underlying thin lithosphere especially in the continental regions have been long-lasting debated. We investigate the structure of the lithosphere and the sub-lithospheric mantle in the Circum-Mediterranean using regional high-resolution 3-D surface wave tomography and integrated geophysical-petrological thermochemical modelling of the temperature field and explore the relation to the occurrence intraplate and mixed-origin volcanic provinces (IMVPs).We define 9 shallow asthenospheric volumes (SAVs) across the Circum-Mediterranean upper mantle that form an almost interconnected belt of reduced shear wave velocities starting from the western Mediterranean to the Middle East and surrounding the Calabrian, Adriatic, Alpine slabs, however only interrupted by the eastern Mediterranean thick oceanic lithosphere. The SAVs are characterized by pronounced variations in shear-wave velocity not only laterally but also vertically between 70 and 300 km depths. Results from integrated geophysical-petrological thermochemical modelling show that the low velocities of the SAVs correspond to areas of thinned lithosphere (i.e., 1300 ºC at about 60-80 km depth) and anomalously warm asthenosphere (down to 300 km approximately) with respect to the average ambient mantle geotherm. A remarkable correlation between these areas and locations of IMVPs is observed with a mean lateral distance of < 100 km separating any SAV to the neighboring IMVP. The maximum separating distances are in order of ~ 350 km indicating a dense network of volcanic provinces above the shallow SAVs.The origin of the SAVs is related either to asthenospheric upwelling caused by slab rollback and decompressional melting during the formation of the back-arc basins (i.e., Agean-Anatolia, Pannonian, Moesian, Western Mediterranean) or to lithospheric thinning and rifting (Middle East and Rhone-Rheine areas). For the origin of the remaining SAVs (Adriatic, Central European, North Africa), other processes, i.e. thermal erosion feed by input from deep mantle sources, are suggested. According to the oldest ages of the IMVPs in the Circum-Mediterranean, the development of the SAVs started at least about ~ 60 - 70 Ma ago and accelerated in the Neogene.
Obtaining robust estimates of the Vs/Vp ratio in the Earth’s lowermost mantle
Authors: Restelli Federica , Koelemeijer Paula , Zaroli Christophe
Published: February 2023

Seismic tomography provides valuable insights into the structure, composition and evolution of the mantle. However, the origin of structures like the Large-Low-Velocity-Provinces (LLVPs) in the lowermost mantle remains debated. Their velocity anomalies have been interpreted to be due to purely thermal or also compositional variations, with implications for mantle circulation, the evolution of the core and the Earth’s heat budget.To uniquely interpret seismic structures such as the LLVPs, it is crucial to constrain the relationships between different seismic observables, e.g. the ratio between shear-wave velocity (Vs) and compressional-wave velocity (Vp) variations. Joint inversions of seismic velocities have been performed, but their velocity amplitudes may be biased, uncertainties are typically not provided, and the resolution of Vs and Vp structures generally differs in existing models.To overcome these issues, we make use of the recently developed SOLA method (Zaroli, 2016), which is based on a Backus-Gilbert philosophy. Instead of finding a model with a particular data fit, we aim to construct model averages of the true Earth with uncertainties, whilst having a control on the model resolution. This direct control on resolution enables us to build Vs and Vp models that sample the same parts of the mantle, and therefore to robustly constrain the Vs/Vp ratio.Here, we test this philosophy by applying the SOLA method to normal modes. These free oscillations of the Earth are particularly useful to study the relationships between seismic velocities as they are directly sensitive to multiple physical parameters, including Vs, Vp as well as density. We illustrate our approach and discuss the trade-off between uncertainties and resolution using synthetic tests for both Vs and Vp, before showing real data inversions. Finally, we discuss the implications of our results for the Vs/Vp ratio in terms of mantle temperature and composition.
Synthetic Generation of Extra-Tropical Cyclones’ fields with Generative Adversarial Networks
Authors: Dainelli Filippo , Taormina Riccardo , Ascenso Guido , Scoccimarro Enrico , Giuliani Matteo , Castelletti Andrea
Published: February 2023

Extra-Tropical Cyclones are major systems ruling and influencing the atmospheric structure at mid-latitudes. They are characterised by strong winds and heavy precipitation, and can cause considerable storm surges potentially devastating for coastal regions. The availability of historical observations of the extreme events caused by intense ETCs are rather limited, hampering risk evaluation. Increasing the amount of significant data available would substantially help several fields of analysis influenced by these events, such as coastal management, agricultural production, energy distribution, air and maritime transportation, and risk assessment and management.Here, we address the possibility of generating synthetic ETC atmospheric fields of mean sea level pressure, wind speed, and precipitation in the North Atlantic by training a Generative Adversarial Network (GAN). The purpose of GANs is to learn the distribution of a training set based on a game theoretic scenario where two networks compete against each other, the generator and the discriminator. The former is trained to generate synthetic examples that are plausible and resemble the real ones. The input of the generator is a vector of random Gaussian values, whose domain is known as the “latent space”. The discriminator learns to distinguish whether an example comes from the dataset distribution. The competition set by the game-theoretic approach improves the network until the counterfeits are indistinguishable from the originals.To train the GAN, we use atmospheric fields extracted from the ERA5 reanalysis dataset in the geographic domain with boundaries 0°- 90°N, 70°W - 20°E and for the period 1st January 1979 - 1st January 2020. We analyse the generated samples’ histograms, the samples’ average fields, the Wasserstein distance and the Kullback-Leibler divergence between the generated samples and the test set distributions. Results show that the generative model has learned the distribution of the values of the atmospheric fields and the general spatial trends of the atmosphere in the domain. To evaluate better the atmospheric structure learned by the network, we perform linear and spherical interpolations in the latent space. Specifically, we consider four cyclones and compare the frames of their tracks to those of the synthetic tracks generated by interpolation. The interpolated tracks show interesting features consistent with the original tracks. These findings suggest that GANs can learn meaningful representations of the ETCs’ fields, encouraging further investigations to model the tracks’ temporal evolution.
Simulation of Arctic sea ice within the Eocene Deep-Time Model Intercomparison Project: thresholds, seasonality and factors controlling sea ice development
Authors: Niezgodzki Igor , Knorr Gregor , Lohmann Gerrit , Lunt Daniel , Poulsen Christopher , Steinig Sebastian , Zhu Jiang , de Boer Agatha , Chan Wing-Le , Donnadieu Yannick , Hutchinson David , Ladant Jean-Baptiste , Morozova Polina
Published: February 2023

The early Eocene greenhouse climate driven by high atmospheric CO2 concentrations serves as a testbed for future climate changes dominated by increasing CO2 forcing. Especially, the early Eocene Arctic region is important in light of future CO2-driven climate warming in the northern polar region. Here, we present early Eocene Arctic sea ice simulations carried out by coupled climate models within the framework of the Deep-Time Model Intercomparison Project. We find differences in sea ice responses to CO2 changes across the ensemble and compare the results with existing proxy-based sea ice reconstructions from the Arctic Ocean. Most of the models simulate winter sea ice presence at high CO2 levels (≥ 840 ppmv = 3x pre-industrial (PI) level of 280 ppmv). However, the threshold when sea ice permanently disappears from the ocean varies significantly between the models (from < 840 ppmv to > 1680 ppmv). Based on a one-dimensional energy balance model analysis we find that the greenhouse effect plays an important role in the inter-model spread in Arctic winter surface temperature changes in response to a CO2 rise from 1x to 3x the PI level. We link this greenhouse effect to increased atmospheric water vapour concentration. Furthermore, differences in simulated surface salinity in the Arctic Ocean play an important role in controlling local sea ice formation. These inter-model differences result from differences in the exchange of waters between a brackish Arctic and a more saline North Atlantic Ocean that are controlled by the width of the gateway between both basins. As there is no geological evidence for Arctic sea ice in the early Eocene, its presence in most of the simulations with 3x PI CO2 level indicates either a higher CO2 level and/or models miss important mechanism/feedback.
Global groundwater recharge modeling in karst with explicit consideration of land cover and snow and glacier storage
Authors: Hartmann Andreas , Liu Yan , Gomez Ospina Mariana
Published: February 2023

Estimating karst water resources at a global scale represents a key step towards enhancing groundwater management. Although recharge estimations at global scale exist, the special karst features leading to different recharge processes, in particular the preferential flow path, have not been adequately accounted for. Representing these special recharge processes is crucial for realistically quantifying recharge in karst regions. In this study, we present a new version of a global karst recharge model and the estimation of its model parameters using multiple observations. The updated model includes a new routine to consider eight land cover types for calculating evapotranspiration, interception and infiltration, as well as a new routine to account for snow and glacier melt. To prepare parameter estimation, six karst landscapes are defined based on the properties of karst grids (spatial resolution of 0.25°). For each of these landscapes, model parameters are found separately using a Monte Carlo uncertainty estimation framework and observations from the international soil moisture network (ISMN) and actual evapotranspiration observations from FLUXNET. With the new calibration, the updated model provides more precise estimates of groundwater recharge in athe karst regions of the world. It will therefore serve as a too  to improve water management in karst regions and identify areas potentially suffering from water shortage.
Web-apps as active learning tools in hydrology classrooms
Authors: Gannon John
Published: February 2023

Active learning strategies such as simulations or problem sets have been shown again and again to be critically useful for helping students understand complex concepts. Students develop a more thorough understanding of processes or problem solving strategies when they are able to practice or explore them with hands-on activities. In hydrology, however, there are several concepts taught, even in introductory classes, where developing suitable activities for this type of learning is difficult. For example, even a simple water balance activity often requires a relatively thorough understanding of spreadsheets or a lot of tedious hand-calculations if students are going to explore relationships between multiple inputs and outputs. Similarly, even the most basic discussion of how a simple box model works is difficult to supplement with an activity that doesn’t involve spreadsheets or writing computer code. Furthermore, it is often beyond the scope of introductory level hydrology classes to teach programming or spreadsheet skills, and hand calculations often take a prohibitive amount of time. Web applications offer a tool to address some of these issues. With the development of tools like Shiny apps for R or Python, instructors with programming experience can relatively easily create interactive learning tools for their classes. Many studies in fields such as statistics and mathematics have shown that these web-apps aid in student learning. Furthermore, hosting and sharing these apps is becoming more accessible, with organizations like CUAHSI running shiny servers. In this presentation, I will show two examples of implementations of a web app to aid in student learning, one on the concept of a water balance, and one on running and parameterizing a basic catchment hydrology model. I will also discuss tools and strategies for building and hosting your own shiny app to address the learning goals for your classes.
The relative sensitivity of convective simulations to perturbations in initial conditions and microphysics parameters
Authors: Posselt Derek
Published: February 2023

Deep convective cloud systems are one of the leading contributors to weather related disasters, provide much of the fresh water used by society, and contribute significantly to the interactions among weather and climate. Convection is known to be influenced strongly by the characteristics of its environment, including the vertical structure of temperature, moisture, and wind. It has also been shown in many numerical modeling studies to be sensitive to the assumptions made in the representation of cloud processes. This presentation will explore the relative influence of environmental (extrinsic) factors and cloud microphysical parameter (intrinsic) uncertainty in the evolution of tropical deep convection. The effect of both types of factor on the energy and water cycle, as well as on convective dynamics and heating, are shown. Ensemble Monte Carlo experiments quantify convective storm sensitivity, while ensemble data assimilation experiments provide traceability from convective outcomes to control factors. The results have implications for modeling, data assimilation, and the design of future observing systems.
Spatiotemporal variability of microcystin concentrations in water of an irrigation pond in Maryland, USA
Authors: Smith Jaclyn , Stocker Matthew , Pachepsky Yakov
Published: February 2023

Cyanotoxins in agricultural irrigation waters pose a potential human and animal health risk. Cyanotoxins can be transported to crops and soil during irrigation where they can remain in the soils for extended periods and be absorbed by root systems. While studies have reported spatial and temporal distributions for cyanotoxins in various freshwater sources, little has been reported for agricultural irrigation ponds. This research aimed to determine if persistent spatial and temporal patterns of the cyanotoxin microcystin occur in agricultural irrigation ponds. The study was performed at a working irrigation pond in Maryland, USA, during the 2022 summer sampling campaign consisting of 6 sampling dates over a fixed spatial 10-location grid. Concentrations of microcystin were determined using ELISA microcystin-ADDA kits. Ten water quality parameters were obtained using fluorometry and in-situ sensing. Relative differences (RDs) between a sampling location’s microcystin concentration and average concentrations across the pond were computed for each sampling date. Mean relative differences (MRDs) were computed for each sampling location for all sampling dates. Positive (negative) MRDs were found in locations where concentrations were predominantly larger (smaller) than the pond’s average. Persistent spatial patterns of microcystin concentrations were established. The pond’s flow conditions and bank proximity to sample locations were indicative of the MRD values signs and amplitude. The highest absolute values of the Spearman correlation coefficients were found between microcystin and pH (-0.777), and microcystin and phycocyanin (0.669). The lowest absolute values for correlation coefficients were found for colored dissolved organic matter (0.226) and chlorophyll-a (0.289). Correlations between microcystin relative differences and water quality relative differences were generally low and not statistically significant. Results of this work show that microcystin concentrations can exhibit stable spatial and temporal patterns in irrigation ponds, indicating that water quality sampling for cyanotoxins and placement of water intake should not be arbitrary. Research of the spatiotemporal organization of other cyanotoxin concentrations as well as understanding the degree of site-specificity of cyanotoxin concentration relationships with water quality parameters presents an interesting research avenue.
Satellite-derived coastal bathymetry over a broad range of geography and water clarity
Authors: Caballero Isabel , Stumpf Richard
Published: February 2023

Monitoring the complex seafloor morphology that drives the functioning of shallow coastal ecosystems is vital for assessing marine activities such as navigation, research, fisheries, aquaculture, tourism, and design or monitoring applications. Satellite-derived bathymetry (SDB) can support these activities, particularly when using data from a platform, like the Sentinel-2A/B twin mission of the Copernicus programme, which provides routine and repetitive image acquisition at 10 m spatial resolution. As a result, SDB can expand on the temporal and spatial scope of more conventional mapping methods, such as lidar or multi-beam. However, SDB still has limitations when applied to the turbid, but optically shallow, nearshore regions that encompass large areas of the world’s coasts. Turbid water produces false shoaling in the imagery, constraining SDB for its routine application. In this study, we integrate water quality information from the Sentinel-2A/B satellites with a multi-temporal compositing method to demonstrate a potential for comprehensively operational bathymetric mapping over a range of environments. The automated compositing method diminishes the turbidity impact in addition to inferring the maximum detectable depth and removing optically deep-water areas. It also returns turbidity data to indicate areas that may still have residual shoaling bias. Examining a wide range of conditions along the Caribbean and eastern coast of the U.S. shows detailed bathymetry as deep as 30 m at 10 m spatial resolution with median errors <1 m when compared to high-resolution lidar surveys. These results demonstrate that the model adopted can provide useful bathymetry in areas that do not have consistently clear water and can be extended across multiple geographic regions and optical conditions for local, regional, and national scales. Because minimal in-situ information is required, this computationally-efficient technique has the potential for automated implementation, allowing rapid and repeated application in more environments than most existing methods. Certainly, SDB can enhance our knowledge of Earth’s nearshore regions generating a crucial dataset for bathymetry maps to understand hazards and impacts produced by climate change in vulnerable coasts.
Transient fluid flow recorded in the Crust-Mantle transition zone of the Oman Ophiolite
Authors: Yoshida Kazuki , Oyanagi Ryosuke , Kimura Masao , Plümper Oliver , Fukuyama Mayuko , Okamoto Atsushi
Published: February 2023

Fluid flow in subduction zones is one of the essential factors of seismic activity in subduction zones. However, the timescale of fluid flow and fluid flow velocity in subduction zones is unclear. In this study, we report antigorite veins with brucite-rich reaction zones in the crust-mantle transition zone of the Oman ophiolite and estimate the timescale and fluid flow velocity during vein formation.In this study, we observed 28 samples in the lower crust to upper mantle section obtained from the Oman Drilling Project Hole CM1A (Kelemen et al., 2020). The lithology of borehole CM1A consists of lower crust (0-160 m depth), crust-mantle transition zone (160-310 m depth), and mantle section (310-404 m depth), which were mainly composed of altered gabbroic rocks (olivine gabbro, troctolite: 5-95% altered) and completely serpentinized dunite and 70-100% serpentinized harzburgite, respectively. Antigorite-chrysotile (Atg-Ctl) vein network was found in dunite at 160-180 m in Hole CM1A. The matrix of the dunite (lizardite, brucite, and magnetite) is cut by antigorite-chrysotile (Atg-Ctl) vein network. Trace element analysis using LA-ICP-MS revealed that the Atg-Ctl vein is enriched in As and Sb compared to the matrix lizardite, suggesting that the Atg-Ctl veins were formed by fluids interacting with subducting sediments. Some of the Atg-Ctl veins are accompanied by brucite-rich reaction zones. The brucite-rich reaction zone was developed at both sides of the antigorite veins with widths of 0.5 – 4 mm. Elemental mapping of the reaction zone using EPMA and TEM show sharp reaction front at scale from micro- to nano- meter.Mass balance calculations and thermodynamic considerations of the reaction zone suggest that the formation of the reaction zone was caused by the removal of silica from the host rock during the precipitation of antigorite in the veins. Based on a diffusion model, we estimated the fluid activity is short-lived (2.1 × 10–1 to 1.1 × 101 yr), and the fluid flow velocity of 2.7 × 10–3 to 4.9 × 10–2 m s-1, which is much faster than those observed for the intact mantle and crustal rocks. This fluid flow velocity along the fractures within the mantle wedge is similar to the observed propagation velocities of seismic events in subduction zones. These results suggest that fluid flow in the overlying plate occurs as episodic pulses as observed as the migration of seismicity in the present subduction zones.
Eruptive processes and landforms recognition in the Garrotxa Volcanic Field, Iberian Peninsula
Authors: Pedrazzi Dario , Cerda Daniela , Granell Jordi , Kerestzuri Gabor , Geyer Adelina , Planagumà Llorenç , Martí Joan , Bolós Xavier
Published: February 2023

The Garrotxa Volcanic Field (GVF) is one of the monogenetic Quaternary volcanic fields associated with the intraplate European Cenozoic Rift System. The GVF is located between the cities of Olot and Girona, NE Spain, and it covers an area of about 600 km2. This volcanic field ranges in age from 0.7 Ma to early Holocene and is considered active since the last eruption dated 11,000-13,000 years ago.The volcanic activity, mainly controlled by regional normal faults generated during the Neogene extension, was highly variable with over 50 scattered eruptive vents that were produced during short-lived monogenetic eruptions. Scoria cones represent the most common landforms of the GVF with subordinate maars and tuff rings/cones. Most of the volcanoes are located in the northern sector between the towns of Olot and Santa Pau and they stand on a folded Eocene basement. Volcanoes located in southern area of the field, close to the city of Girona, stand mainly on a fractured Paleozoic basement.The objective of this work is to identify eruptive processes and the geomorphic evolution of volcanic edifices and related them to environmental influencing factors. The best volcanic structures in the GVF have been selected due to their well-preserved morphologies. Cones (Wco) and craters (Wcr) mean diameters, as well as cones maximum height (Hmax), maximum crater depth (Dcrmax) and external slope of the cones (Smedian) have been measured.This study shows that it is possible to create a catalogue of likely eruption sequences based on field evidences and morphological/morphometric data. In this way, a more realistic eruption scenarios can be developed for different parts of the volcanic field. Morphometry can also provide rough relative age constraints on edifices. These methodologies can improve our understanding for a better evaluation of volcanic hazards in urbanized volcanic fields as the GVF.
The effects of 3D normal fault interactions in seismic cycles
Authors: Rodriguez Piceda Constanza , Mildon Zoë , van den Ende Martijn , Ampuero Jean Paul
Published: February 2023

Numerical earthquake simulators are valuable tools for investigating the causal dynamics between seismic events and improving our understanding of seismic sequences. This approach has been widely applied to single strike-slip faults, but physics-based simulations of earthquake cycles for normal fault(s) and networks are still limited. This is partly due to the focus on studying the California fault system and the computational cost of modelling dip-slip faults, which involve additional computations related to normal stress changes during the earthquake cycle. We aim to address this gap by focusing on the effect of normal fault interaction in the generation of complex seismic sequences. Using the open-source boundary-element method QDYN, we model two 3D normal faults incorporating rate-and-state friction and elastic interactions. We examine the impact of variable spatial offsets between the faults on different properties of the earthquake cycle, including slip, slip rate, magnitude distribution, and recurrence intervals within and between faults. By doing so, we aim to provide a physical explanation for the spatial and temporal variability observed in the geological record of natural normal fault networks, such as those found in the Central and Southern Apennines in Italy. Our results will shed light on the behaviour of normal fault networks and contribute to a more comprehensive understanding of earthquake cycles in these systems.  
Effects of large-scale layering and small-scale mineral fabric on the seismic anisotropy of Ivrea-type lower continental crust
Authors: Luo Zheng , Müntener Othmar , Hetényi György , Holliger Klaus
Published: February 2023

Most information on the P-wave seismic velocity of the lower continental is based on controlled-source wide-angle seismic experiments, for which the direction of wave propagation in the target region is largely horizontal. Following the common practice of interpreting such data in an isotropic framework, too high P-wave velocities would therefore be inferred in an anisotropic lower continental crust, for which the long axis of the anisotropy ellipsoid is roughly aligned with the horizontal direction. This, in turn, would result in a bias of the interpretation of the lower crustal bulk composition towards the mafic side and potentially also lead to incorrect estimations of crustal thickness. Anisotropy of this type can arise from the small-scale sub-horizontal alignment of anisotropic minerals and/or from large-scale sub-horizontal layering. To assess the likely importance of lower crustal anisotropy in general and the respective contributions of mineral fabric and layering in particular in Ivrea-type lower continental crust, we analyze a range of layered canonical models. The individual layers are parameterized based on published laboratory measurements of seismic velocities from pertinent rock samples. Our preliminary results indicate that anisotropy related to the mineralogical composition and fabric prevails over the corresponding effects of layering. For the considered canonical models, these effects are particularly prominent in the presence of metapelitic rocks, where a petrological interpretation of the inferred average horizontal P-wave velocity could indeed lead to a notable overestimation of the mafic component. Conversely, our initial results also indicate that in the absence of metapelitic rocks, the anisotropy-induced velocity bias may be sufficiently benign to allow for a reasonably reliable interpretation of the bulk composition of the lower continental crust based on the P-wave velocity inferred from wide-angle seismic data.
A novel C-Band UAV-Radar for 3D characterisation of forest canopy backscatter profiles - Preliminary results
Authors: Escobar-Ruiz Veronica , Morrison Keith , Sjögersten Sofie , Siewert Matthias B. , Fox Nigel
Published: February 2023

This work reports on a novel C-band monostatic UAV-radar system deployed over two forested wetlands in arctic Sweden, near to the Abisko research station. A Videodrone X4S drone acted as the carrying body, allowing programmable and repeatable flight paths. The radar system is multi-polarized (VV, VH, HV, HH), using one transmitter and optionally one or two receivers. The radar operates in a sawtooth FMCW mode, monotonically stepping in frequency across 5.2 GHz to 5.6 GHz. The choice of sweep time (1 to 8 ms) and number of data points (128 to 2048) are programmable and selected before a flight. The radar is triggered in flight manually from the ground using a Wi-Fi link, and which then repeatedly loops over a pre-set number of 10 s scans. Here, the choice of a drone speed of 5 m s-1 meant that each scan covered a 50 m flight line. There is a re-setting time of 0.3 s between scans. The wetlands are covered by a sparse forest, primarily of birch typically 3 to 7 m tall. We used the tomographic profiling (TP) scheme to collect high-resolution maps of the vertical scattering through the forest canopy. Such information is not available from the coarser satellite imagery, which provides no information on the vertical distribution of the backscatter, not even on the relative strengths of the ground and canopy returns. As the TP scheme has the antennas forward facing, only a narrow image transect beneath the flight path is collected. A synthetic aperture technique is used both to sharpen the real beam in the along track direction, and additionally steer it in angle. Thus, post-measurement, a single flight can be processed to capture the incidence angle response of the whole scene at a single incidence angle, selectable over a ~40 degree range. The results show how the forest backscatter response changes from one dominated by a ground return close to nadir viewing, to one dominated by the canopy above 20 degrees incidence angle. Comparisons and comment will also be provided of the differing responses with polarisation. 
Evidence of a dual kinetic energy cascade by surface drifter observation in the Walvis Ridge Region
Authors: Draeger-Dietel Julia , Griesel Alexa , Walter Maren , Horstmann Jochen , Carrasco Alvarez Ruben , Carpenter Jeff
Published: February 2023

The characteristics of turbulence and  processes driving it in the regime connecting mesoscales (mainly upscale energy transfer rates) and classical microscales turbulence (downscale energy transfer) are not fully well-established.
Here we analyse two-point velocity data from 2 entangled near-simultaneous relases of two different kinds of surface drifters floating in different depth (50 cm and 15 m) of the ocean mixed layer in the Walvis Ridge Region in the South Atlantik. For the 'deep drifters' the compensated third order longitudinal velocity structure function  shows a positive plateau for inertial scales roughly between 15 km  and 150 km,
revealing evidenve of an inverse cascade similar to former findings in the Benguela region. In contrast the 'shallow drifter'
do not show a positive platau at these scales, but show evidence of a forward cascade (negative plateau) and Kolmogorov self-similarity on  spatial scale around 500 m.
Elemental chemostratigraphy in the Ediacaran-Cambrian Nama Group, Namibia: preliminary results.
Authors: Pescarini Thales , Fernandes Henrique , Pereira Luiz Gustavo , Bedoya Rueda Carolina , Babinski Marly , Leme Juliana , Boggiani Paulo Cesar , Trindade Ricardo
Published: February 2023

The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life system, as evidenced by intense perturbations in biogechemical cycles and the appearance of complex macroscopic life. Many questions remain regarding the relationship and feedback between the biotic and abiotic processes that operated in that period, particularly the interconnections between changes in paleoclimate, tectonics, and the biological evolution. Here we present new geochemical data for the Nama Group, South Namíbia, sampled as part of the ICDP GRIND (Geological Research through Integrated Neoproterozoic Drilling) project, a global scientific collaboration that aims to study, in an integrated and multidisciplinary way, different sedimentary sequences in Namibia, China and Brazil, which encompass the terminal Ediacaran and the base of the Cambrian. Our sampling was carried out in the entire stratigraphic interval of the Nama Group in a 5 m resolution, always respecting the variations in facies and fossiliferous content and avoiding highly disturbed strata. X-ray fluorescence analyses were conducted 745 samples through a portable XRF device. The preliminary results of major elements, such as Si, Al, Ti, Sr and Ca, show major environmental shifts in the stratigraphic column, usually reflecting facies variations. The preliminary data presented herein is of key importance for the subsequent studies in the drill cores of the GRIND project, comprising geochronology, isotope analyses and paleontology.
Changing impact of the large-scale atmospheric circulation on the regional climate variability of the Baltic Sea for the period 1950-2022
Authors: Lehmann Andreas , Post Piia , Myrberg Kai
Published: February 2023

A detailed assessment of climate variability of the Baltic Sea area for the period 1958-2009 (Lehmann et al. 2011) revealed that recent changes in the warming trend since the mid-1980s, were associated with changes in the large-scale atmospheric circulation over the North Atlantic. The analysis of winter sea level pressure (SLP) data highlighted considerable changes in intensification and location of storm tracks, in parallel with the eastward shift of the North Atlantic Oscillation (NAO) centres of action. Additionally, a seasonal shift of strong wind events from autumn to winter and early spring existed for the Baltic area. Lehmann et al. (2002) showed that different atmospheric circulation regimes force different circulation patterns in the Baltic Sea. Furthermore, as atmospheric circulation, to a large extent, controls patterns of water circulation and biophysical aspects relevant for biological production, such as the vertical distribution of temperature and salinity, alterations in weather regimes may severely impact the trophic structure and functioning of marine food webs (Hinrichsen et al. 2007). To understand the processes linking changes in the marine environment and climate variability, it is essential to investigate all components of the climate system which of course include also the large-scale atmospheric circulation. Here we focus on the link between changes/shifts in the large scale atmospheric conditions and their impact on the regional scale variability over the Baltic Sea area for the period 1950-2021. This work is mostly an extension of previous studies which focused on the response of the Baltic Sea circulation to climate variability for the period 1958-2008 (Lehmann et al. 2011, Lehmann et al. 2014). Now extended time series ECMWF ERA 5 reanalysis for 7 decades are available, highlighting recent changes in atmospheric conditions over the Baltic Sea. The main focus of this work is to identify predominant large scale atmospheric circulation patterns (climate regimes) on a monthly/seasonal time scale influencing the regional atmospheric circulation over the Baltic Sea area. Furthermore, long-term changes on the annual to decadal time scale will also be investigated.
Disentangling biotic and abiotic drivers of CO2 flux in a drained German peatland using eddy covariance flux measurements and modelling techniques
Authors: Behrens Nicolas , Gharun Mana
Published: February 2023

Natural undisturbed peat lands act as a net carbon sink while drainage and subsequent aeration of the peat layers leads to oxidation of the organic material and the release of greenhouse gases. In Germany emissions from peatlands make up over 7 % of the country’s total annual carbon emissions. However, continuous observations with a high temporal resolution in German peatlands are still rather sparse. Due to the heterogeneity of peatland ecosystem characteristics and their relations to GHG fluxes, it is a major challenge to understand and model emissions across the wider category of peatlands. Some of the frequently used models (for example in interpolation of chamber-based measurements) are straightforward and easy to implement but leave potentially valuable information aside. In this study we use high-frequency (10Hz) CO2 and H2O exchange measured with eddy covariance at a drained bog, along with a suite of meteorological, hydrological and phenological measurements to disentangle the roles of biotic and abiotic variables in peatland CO2 emissions. The site is a highly drained but intact bog with a peat body of roughly 3 m and a groundwater depth of around 60 cm, located in northwestern Germany. Preliminary results collected with manual chambers show that methane fluxes are negligible. First, we test the model performance of the commonly used rectangular hyperbolic light response curve for GPP. We then extend this model by including a greenness index derived from a time series of daily Phenocam images, allowing us to evaluate the impact of biotic drivers and their seasonality. Similarly, for Reco we test the performance of the classical exponential Lloyd & Taylor model and modify it by accounting for the underlying hysteresis observed in the response of respiration to soil temperature changes, by including hydrological drivers such as soil moisture, precipitation and water table depth. Our results advance our capacity for understanding and predicting how peatland ecosystems respond and contribute to changes in the Earth´s future climate. 
Vertical momentum in the boundary layer and its consequences for transport of greenhouse gases
Authors: Abril-Gago Jesús , Kowalski Andrew S.
Published: February 2023

Like mass and energy, momentum is an extensive quantity and so the momentum of a system is equal to the sum of the momenta of its components. Considering boundary-layer air in the surface-normal ("vertical") direction, its components have momentum in different directions. That of carbon dioxide is downward due to photosynthetic uptake by ecosystems, while those of oxygen and water vapor are upward due to photosynthetic and evaporative sources, respectively. And so on. Importantly, evaporation is several orders of magnitude greater than any other form of surface exchange, and therefore the vertical momentum of air can be precisely approximated by that of water vapor. This allows estimation of the vertical velocity as simply the ratio of the evaporative flux density to the air density, and has important consequences for many aspects of boundary-layer meteorology.We analyzed atmospheric data from numerous flux towers over a range of climatological and ecological contexts to characterize the vertical velocity and consequent magnitudes of non-diffusive greenhouse gas transport. Our results invalidate long-standing and intuitive attribution of diffusion of some greenhouse gas directly to its sources and sinks, which has neglected the key role of water vapor in diluting the components of dry air.This work was supported by the projects PID2020-117825GB-C21 (INTEGRATYON3), B-RNM-60-UGR20 (OLEAGEIs) and P18-RT-3629 (ICAERSA) including European Union ERDF funds.
Geophysical methods of soil fertility mapping for precision agriculture applications in semi-arid regions (Morocco)
Authors: Aallem Fatima-Ezzahra , Charbaoui Anas , Ahmed Laamrani , Kchikach Azzouz , Jaffal Mohammed , Jnaoui Younes
Published: February 2023

Experiments on a plot-scale of apparent electrical conductivity (ECa) and resistivity (ERT) variation with correlation of soil properties were studied for soil mapping at the experimental farm of Mohammed VI Polytechnic University of Benguerir (UM6P). The ElectroMagnetic Induction (EMI) technique was applied using a soil sensor EM38-MK2 which provides auxiliary ECa data sets with accuracy. The other method ERT was used to measure the electrical resistivity. The study was supported by soil sampling to ensure the reliability and potential of ECa measurements for soil mapping.  ECa readings in mS/ m ranged from 12 to 26 and 8 to 20 respectively in the vertical (ECa-V) and horizontal mod. ECa and ERT readings correlated best with soil properties such as texture (clay and sand), and upper soil chemical properties (OM, CEC, Ca2+, Fe2+and Mg2+). A modest correlation was found between ECa-V, clay and subsurface water content (r = 0.80), (r = 0.79). The linear relationship found between apparent electrical conductivity and soil clay content explained 80% of the measured variability. The results of the study raised the hope that soil mapping by ECa measurement can fairly represent the spatial variation of soil properties such as texture, chemical fertility and organic matter content. The use of spatial variability in EC as a co-variate in statistical analysis could be a complementary tool in the evaluation of experimental results.
Numerical modelling of opposing subduction in the Western Mediterranean
Authors: Peral Millán Mireia , Fernàndez Manel , Vergés Jaume , Zlotnik Sergio , Jiménez-Munt Ivone
Published: February 2023

The geodynamic evolution of the Western Mediterranean related to the closure of the Ligurian-Tethys ocean is not yet fully resolved. We present a new 3D numerical model of double subduction with opposite polarities fostered by the inherited segmentation of the Ligurian-Tethys margins and rifting system between Iberia and NW Africa. The model is constrained by plate kinematic reconstructions and assumes that both Alboran-Tethys and Algerian-Tethys plate segments are separated by a NW-SE transform zone enabling that subduction polarity changes from SE-dipping in the Alboran-Tethys segment to NW-dipping in the Algerian-Tethys segment. The model starts about late Eocene times at 36.5 Ma and the temporal evolution of the simulation is tied to the geological evolution by comparing the rates of convergence and trench retreat, and the onset and end of opening in the Alboran Basin. Curvature of the Alboran-Tethys slab is imposed by the pinning of its western edge when reaching the end of the transform zone in the adjacent west-Africa continental block. The progressive curvature of the trench explains the observed regional stress reorientation changing from N-S to NW-SE and to E-W in the central and western regions of the Alboran Basin. The increase of the retreat rates from the Alboran-Tethys to the Algerian-Tethys slabs is compatible with the west-to-east transition from continental-to-magmatic-to-oceanic crustal nature and with the massive and partially synchronous calc-alkaline and alkaline magmatism.
Sedimentary ancient DNA reveals plankton community shifts in subarctic western Bering Sea back to the Eemian interglacial
Authors: Stoof-Leichsenring Kathleen , Buchwald Stella , Nürnberg Dirk , Harms Lars , Herzschuh Ulrike
Published: February 2023

Understanding past ecosystems in the Arctic and subarctic oceans is important to project ecosystem development under enhanced warming. Sedimentary ancient DNA (sedaDNA) is a fantastic proxy providing information with sufficient taxonomic width and depth to comprehensively reconstruct past ecosystems. This study uses shotgun metagenomics of 42 sediment samples to decipher phyto- and zooplankton community changes over the last glacial-interglacial cycle back to the Eemian in the subarctic western Bering Sea. We aim to understand the sensitivity of plankton community composition to climate changes and its consequences on food web dynamics and carbon export. Our results indicate that micro- phytoplankton, like sea-ice associated diatoms, and cold-adapted chlorophytes, along with crustaceous zooplankton (copepods) dominated during the last glacial period. Contrarily, pico/nano-sized phytoplankton and the diatom family Chaetocerotaceae accompanied by heterotrophic protists and reduced abundance of copepods characterized the interglacial plankton communities. Further, we identified profound differences between the Holocene and Eemian. Particularly, the Holocene records a pronounced increase of pico-sized cyanobacteria, whereas in the Eemian, cold-water related taxa like Bathycoccaceae and Triparmaceae sub-dominate the community, supporting unique communities in both interglacials, challenging an analogy to future warming scenarios. In summary, our study shows evidence for a shift from micro-sized towards pico-sized phytoplankton with climate warming in the Holocene, accompanied by a more diverse zooplanktonic community dominated by bacterial grazing heterotrophic protists. Under future warming, decreased phytoplankton cell size and shifts in the grazing communities could affect food web linkages and result in reduced potential carbon sequestration and export in the subarctic Bering Sea, weakening its function as an effective carbon sink.
Climate and anthropogenic effects on the coevolution of soils and vegetation: A case-study in the Pacific island of Santa Cruz (Galapagos, Ecuador)
Authors: Vanacker Veerle , Paque Rose , Alomia Herrera Ilia , Dixon Jean , Montes Anchali Yessenia , Zeheter Frantz , Molina Armando
Published: February 2023

Understanding the complex interactions between climate, vegetation and soils is important for the sustainable management of soil ecosystems in the context of climate and land use change. Few benchmark data exist on soil-landscape and vegetation interactions, as most soil ecosystems have a legacy of past land use and management.By working in the Galapagos Islands, a UNESCO World Heritage Site, we have the opportunity to better constrain the coevolution of soils and vegetation over millennial timescales for pristine soil ecosystems. Five monitoring sites are located on the Pacific Island of Santa Cruz, and they cover a ~10 km long NW-SE stretch. Along this gradient with a 10-fold increase in mean annual precipitation, the climate effects on the coevolution of soils and vegetation were quantified. Soil weathering extent was assessed through geochemical proxies, and these data were then related to time-series of precipitation, air and soil temperature, and humidity to explore the relationships between soil and vegetation development, and climate. Then, by contrasting the data from five pristine soil ecosystems with data from agricultural soils, new information was obtained on the anthropogenic effects on soil ecosystems.Soil weathering indices and elemental mass balances were used as a measure of soil development and were derived from the soil's physical and chemical properties measured at soil profiles. For the pristine sites, there is a nonlinear relationship between the degree of soil and vegetation development and (hydro)climatic data. Forest conversion into agricultural land leads to measurable effects on soil ecosystem services and functions.