bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing the sensitivity of gross primary production to the water stress in the Amazon rainforest using CMIP6 models
Authors: Taguchi Takuto , Ichii Kazuhito
Published: February 2023

Tropical rainforests in the Amazon play a vital role in absorbing atmospheric CO2, yet there remains a significant degree of uncertainty surrounding the process, magnitude, and potential future changes. In this study, we used outputs of Earth System Models (ESMs) to explore the impacts of dry-season precipitation changes on the terrestrial carbon cycle, with a specific focus on Gross Primary Production (GPP), which has yet to be thoroughly examined. The seasonal amplitude of GPP over the Amazon rainforests from the CMIP6 ensemble displayed significant variations among models resulting from dry-season decline, and these are much higher amplitude compared to reference data from 1981-2000. The regions with less precipitation are particularly vulnerable in the models, and this dry-season decline is anticipated to significantly intensify by the end of the 21st century due to the drying associated with global warming.
Seasonal and inter annual effects of meltwater runoff on ice dynamics in Northeast Greenland
Authors: Tabone Ilaria , Fürst Johannes J. , Mölg Thomas
Published: February 2023

The large amount of meltwater reaching the base of a glacier at the beginning of the melt season accelerates its ice flow, as meltwater pressurised in cavities acts as bed lubricant. Proceeding in the melt season, if the erosive power of basal water becomes high enough to prevail on the creep-induced closure of such cavities, channels may form. In this regime, water is efficiently drained towards the ice front, basal pressure abates and ice flow decelerates. The temporary speed-up and deceleration throughout the melt season has been observed in many glaciers in Greenland, especially in the southwest. There, more observations are available and the ablation zone extends hundreds of km inland. Yet, there is no evidence that Northeast Greenland follows this hydrology-induced dynamic behaviour. In fact, very few observations of flow variability during the melt season are available for this area, hampering our understanding of impacts of meltwater on the ice dynamics in these remote arctic regions. In this work we run a fully coupled ice-flow-hydrology model (Elmer/Ice coupled to GlaDS) to explore the feedbacks between surface meltwater and ice-flow variations over the whole basin of Northeast Greenland. We address both seasonal and annual timescales by running the coupled model for successive melt seasons (from May 2016 to the end of September 2018). To do so, we make use of daily surface mass balance and runoff data computed by a fully-fledged surface energy balance model (COSIPY) resolving snowpack processes. Our simulations show a seasonal speed-up due to increase in melt water pressure at the base, followed by a decrease in velocities due to the activation of a channelised system beneath the ice sheet. Our results suggest that the Northeast Greenland presents a complex hydrological system that is comparable to other regions of the ice sheet and hint at hydrology-dynamics mechanisms to be a potential controlling factor in the evolution of the area. 
Testing the use of sodium polytungstate for an efficient extraction of microplastic particles from river sediments
Authors: Uguagliati Francesca , Ghinassi Massimiliano , Zattin Massimiliano
Published: February 2023

Rivers are the primary pathways for microplastic (MP) particles from terrestrial sources to the sea, but they can also be temporary reservoirs of MPs, that can be easily stored in alluvial sediments. Knowing the MPs content in sediments is critical for i) understanding where and how they accumulate over time, ii) assessing their toxic effects, and iii) developing mass balance models based on their fate and fluxes. Given the rapid growth of the research field and the lack of standardized methods, extraction strategies for MP particles from sediments have become inconsistent, and new techniques are constantly being developed. Several studies highlight that density separation using high-density concentrated saline solutions is one of the most reliable and efficient separation methods. In this study, we tested the efficiency of sodium polytungstate (ρ = 3.1 g · cm-3), diluted with distilled water to a density of 1.6 g · cm-3, as a density separation agent. Sodium polytungstate has an intermediate density between that of sediments and plastic and has also been used successfully for the gravity separation of minerals and rocks. Furthermore, it is non-toxic, it is stable in the pH range of 2-14 and can be easily recovered and reused. In this study, artificial sediment samples were created by adding 50 MP items into 25 grams of plastic-free sand. MPs-free sediments were sampled from Pleistocene alluvial deposits of the Upper Valdarno Basin (Italy) after removing the surficial layer to avoid contamination. Sediments were divided into three different particle size ranges (i.e., 250-63 μm, <63 μm, <250 μm). Different shapes of MPs were used in the experiments: i) fibres obtained by cutting 500 μm long segments of a nylon drawstring, ii) fragments created by cutting PVC pipes, and iii) PET glitters used as films. A total of 45 experiments were performed. Before applying the procedure for density separation, samples were prepared using Wet Peroxide Oxidation (WPO) to remove the organic matter. Successively, a sodium polytungstate saline solution was used for the extraction technique and the suspended solids were collected and transferred to filters. The MP particles were counted using a stereomicroscope. Results highlight the very high efficiency of the system, although some variance is present and related to the different shapes of MPs and the sediment particle size.
Revisiting the Messel palynoflora using a combined LM and SEM approach
Authors: Bouchal Johannes M. , Geier Christian , Ulrich Silvia , Wilde Volker , Lenz Olaf K. , Zetter Reinhard , Grímsson Friðgeir
Published: February 2023

The early to middle Eocene maar lake of Messel is a world-renowned fossil locality. Its oil shale deposits are well-known for their exceptional preservation of vertebrates (e.g., crocodiles, early horses) and invertebrates, especially insects. The makro- and microfossil remains of plants also contributed to providing a more holistic snapshot of this Eocene ecosystem. So far, the palynoflora has mostly been investigated using only conventional LM, and the classic taxonomic qualitative/illustrative work on the palynoflora dates back to the late 1980ies. Here we report on the first results from an ongoing study using combined LM and SEM, and in some cases even TEM, to re-investigate the Messel palynoflora qualitatively. The main goals of our study are to conclude (I) if some of the spores/pollen can be systematically placed with more certainty, (II) if additional spore/pollen types can be discovered, (III) to compare our combined method of investigation with the classic LM-based counting method, and finally (IV) to conclude about the composition and species richness of the palynoflora and how it correlates with the macro- and mesofloras. To accomplish this, we first processed a single sedimentary rock sample without fine-mesh sieving and then extracted and investigated every pollen type encountered using the single-grain method. So far, this sample has produced 30 spore types, 5 gymnosperm pollen types, and about 185 different angiosperm pollen types. The previous LM-based qualitative work identified 173 palynomorphs in an accumulative account from numerous rock samples up-trough the oil shale section. Our study, on a single sample from the lowest part of the oil shale revealed every single pollen type (except for Milfordia (Restionaceae) and Pityosporites microalatus (Cathaya, Pinaceae)) discovered in the accumulative approach using the classic LM counting method. Also, in addition to the c. 140 angiosperm pollen types previously recorded, we can now add at least 45 new pollen types for this locality. Our study shows that when taxonomic resolution and diversity are key, a combined LM and SEM investigation produces higher diversity than relying only on the conventional LM counting method when single samples are compared. In addition, a well-preserved single sample extensively studied using the combined approach is likely to provide the same or even higher number of taxa when compared to conventional LM counting methods analyzing an entire stratigraphic section. The qualitative combined approach will provide a more reliable presence/absence of taxa in the accumulation site hinterland. For quantitative analysis and subtle changes in the surrounding environments conventional counting methods are more appropriate because of the universal availability of light microscopes and difficulties with SEM-counting.
THM modelling of seismic velocities changes at DeepStor heat storage demonstrator
Authors: Fraile Clara , Gaucher Emmanuel , Kohl Thomas
Published: February 2023

In Central Europe, the thermal energy required for heating and cooling represents a major CO2 emitter in the energy sector. Seasonal underground heat storage offers the option to store a large amount of excess heat in summer for usage in winter and, with that, decrease the need for conventional sources of energy. Today, high-temperature aquifer thermal energy storage (HT-ATES) systems are attracting large interest for securing a heat demand in a sustainable manner.In HT-ATES systems, hot water is injected into a reservoir over the summer months while exchanged cold water is injected over the winter season. These changing temperatures and pressures will affect the geomechanical and thermo-hydraulic properties of the reservoir and the surrounding layers. Monitoring the changes in the reservoir properties is key to run a heat storage system safely and efficiently. We try to determine if active seismic imaging could be a suitable method to characterize the time-space evolution of the reservoir.With view on designing future geophysical assessment and monitoring systems, we perform thermo-hydro-mechanical (THM) modelling, using MOOSE and TIGER applications, with characteristics based on the DeepStor demonstrator under development in the north of Karlsruhe (Germany), at KIT, to determine the changes in the poroelastic properties of the underground. The first three layers model includes different mechanical properties with one borehole. The simulation of hot water injection over a period of time allows to quantify its effect on the underground material properties. Besides the DeepStor demonstrator expected operational frame, we test additional injection schemes with varying underground properties to simulate the different ranges of porosity changes and look at their effects on the elastic properties.The changes in the parameters from the THM model are linked to seismic sensitive variables, such as velocities and impedances, using empirical equations. Hence, we can quantify the effects of injection on such variables and determine if it would be possible to detect them with active seismic surveys.
Steady states in complex climate models and different methods for the construction of the bifurcation diagram
Authors: Brunetti Maura , Ragon Charline
Published: February 2023

The climate system can be regarded as a non-equilibrium dynamical system that relaxes toward a steady state under the continuous input of solar radiation and dissipative mechanisms over a multitude of temporal and spatial scales. The steady state is not necessarily unique. A useful tool to describe the possible steady states of the climate system is the bifurcation diagram, where the long-term behaviour of a state variable (like surface air temperature) is plotted as a function of force intensity. This diagram reveals the regions of multi-stability, the position of B-tipping (bifurcation points at critical forcing values giving rise to an abrupt and irreversible climate change), the range of stability of each attractor and the intensity of climate variability needed to induce transitions between states (N-tipping).The construction of the bifurcation diagram requires to run long simulations from a huge ensemble of initial conditions until convergence to a steady state is attained (standard method). This procedure has prohibitive computational costs in general circulation models of the climate that include deep ocean dynamics relaxing on timescales of the order of thousand years, or other feedback mechanisms with even longer time scales, like continental ice or carbon cycle.Using a coupled setup of the MIT general circulation model, we propose two techniques that require lower computational costs and show complementary advantages. We test them in a numerical setup that includes deep ocean dynamics and we compare the resulting bifurcation diagram with the one obtained with the standard method. The first technique is based on the introduction of random fluctuations in the forcing and allows one to explore a large part of the phase space. The second, based on the estimate of internal variability and relaxation time, is more precise in finding B-tipping.
Modeling terrestrial water balance using regionalization of hydrological model parameters at Kalli watershed, Estonia.
Authors: Noe Steffen M. , Ferreira Mercuri Emílio Graciliano
Published: February 2023

Terrestrial water storage and evapotranspiration (ET) have strong dependence on vegetation type at the catchment scale, and they also play an important role in the forest management and carbon exchange. Regionalization methods dependent on rainfall-runoff models comprise techniques for transferring calibrated parameters in instrumented basins (donor basins) to non-instrumented basins (target basins). In this study, regionalization was used to transfer of parameters from the GR4J-Cemaneige model calibrated in Reola hydrographic basin to predict daily flows in Kalli basin, both watersheds located in the south-east of Estonia. The basins are covered with hemi-boreal forests and we used the hypothesis that both basins have physiographic and climate similarity, besides being close to each other. ET historical data was collected from the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR Estonia), located in Järvselja forest in Kalli basin. Precipitation data was collected from Tartu-Tõravere and SMEAR stations, and the river flow from Reola hydrometric station. The time series period adopted for model calibration was 2015-2018 and the 2019 year was used for validation. Point precipitation measurements are generally used to calculate average precipitations at the watershed scale. However, several studies point out that the use of rain gauges can generate errors in undermeasurement of precipitation, both for snow (solid precipitation) and rain (liquid precipitation), mainly due to the effect of wind. Water Balance Method (WBM) was used to correct the precipitation from Reola Watershead and then GR4J-Cemaneige model was calibrated at Reola Basin, with Nash-Sutcliffe Efficiency index of 0.77. The precipitation series from SMEAR at Kalli watershed was corrected to consider the solid precipitation, using data from Tartu-Tõravere station. For modeling the Kalli watershed streamflow an iterative process was created and it consists of: i) run the hydrological model and obtain the streamflow, ii) apply the WBM correction on the precipitation data, iii) repeat step (i) until the correction factor stabilizes to a fixed value. This methodology allowed to obtain the terrestrial water storage daily variation from the beginning of 2015 to the end of 2019 with high reliability, since the watershed is treated as a system. The results indicate that the terrestrial water storage is positive in winter and negative in the summer period, reaching absolute maximum values of 200 mm.  This research allows a better understanding of the Järvselja hemi-boreal forest water dynamics and its variation through the seasons, especially in the context of climate change. Next steps are to analyze the relations between carbon, energy and water balance at stand and catchment scales.
The influence of landscape evolution on Scandinavian Ice Sheet dynamics and extent
Authors: Jungdal-Olesen Gustav , Pedersen Vivi Kathrine , Andersen Jane Lund , Born Andreas
Published: February 2023

Ice sheets have shaped the Scandinavian landscape during numerous glacial periods throughout the Quaternary, but little is known about the effects of a changing landscape on the Scandinavian ice sheets in return. Here, we use a higher-order ice-sheet model (iSOSIA) to investigate how past morphological changes in the Scandinavian landscape may have affected ice-sheet extent and dynamics. Our preliminary results indicate that the Scandinavian ice sheet would have extended further south before the formation of the Norwegian Channel, which is believed to have been formed by glacial erosion during recent glacial periods (since ∼0.5 Ma). This suggests that landscape changes should be considered in addition to varying climate conditions, when exploring changes in ice-sheet dynamics and extent between glacial periods.
Metamorphic evolution of a garnet-bearing schist from the Bogegga Formation, Svalbard
Authors: Turek Olga , Kośmińska Karolina
Published: February 2023

The Bogegga Formation crops out on Oscar II Land in the western part of Svalbard archipelago. It is part of the Kongsvegen Group which belongs to the Southwestern Basement Province. This unit contains garnet-bearing mica schists and gneisses, pegmatites, and calc-schists which experienced up to a medium grade metamorphism (Hjelle et al., 1999). However, the petrological studies including estimation of the pressure-temperature (P-T) conditions have not been performed so far. Here we present the petrological characteristics of the highest grade garnet-bearing mica schist and the P-T estimates using a combined approach.The studied schist consists of garnet porphyroblasts, white mica, biotite, quartz, and plagioclase. Tourmaline, epidote, allanite, zircon, and zoisite are accessory minerals. Garnet shows two distinctive compositions. Garnet-I forms cores and its composition is Alm76-81Grs6-9Prp8-14Sps2-4. It contains voluminous quartz inclusions. Garnet-II is generally calcium richer and forms rims or fills cracks within garnet-II. Its chemical composition can be characterized as Alm71-72Grs18-23Prp4-7Sps2-3. White mica is muscovite with Si content varying from 3.075 to 3.162 a.p.f.u. Biotite shows chemical zonation between the inclusions within garnet-I (XFe = 0.36 to 0.50) and matrix (XFe = 0.64 to 0.68). Plagioclase is dominated by albite endmember and its composition is Ab77-97An2-22Or1-2. Rims of bigger porphyroclasts are albite rich, whereas cores are enriched in anorthitic component. Two metamorphic phases M1 and M2 were distinguished based on the petrological studies and P-T estimates. Preliminary P-T estimates suggest garnet-I growth at  4.3 – 8.5 kbar and 415 – 560 °C (M1), followed by garnet-II and matrix minerals formation at higher pressures and temperatures of 7.5 – 10.8 kbar and 590 – 675 °C (M2).Amphibolite facies rocks that experienced similar P-T conditions are known from SW Svalbard (f.E. Müllerneset Formation, Berzeliuseggene unit, Isbjørnhamna Group, Pinkie unit). The correlations of the Boggega Formation with other amphibolite facies units cropping out along southwestern Svalbard require further studies including detailed geochronological analyses. This work was partly funded by the National Science Centre of Poland project no. 2021/43/D/ST10/02305.References:Hjelle A., Piepjohn K., Saalmann K., Ohta Y,. Salvigsen O., Thiedig W., Dallmann W.K. (1999). Geological Map, Svalbard 1:100 000, A7G Kongsfjorden, Norsk Polarinstitutt, Tromsø.
Comparisons and water level analyses using Sentinel-6MF satellite altimetry data with 1D Mascaret and 2D Telemac models.
Authors: Ricci Sophie , Nguyen Thanh Huy , Le Gac Sophie , Boy François , Piacentini Andrea , Rodriquez-Suquet Raquel , Peña-Luque Santiago , bonassies quentin , emery charlotte
Published: February 2023

Remote sensing products provided by satellite missions, airborne and unmanned aerial vehicle (UAV) campaigns have tremendously developed over the last decade. They undoubtedly offer opportunities to improve our ability to monitor and forecast flooding. The observation of inland waters benefits from several altimetry missions that provide along-track water surface elevation observation from nadir (e.g. TOPEX/Poseidon, Jason, SARAL/AltiKa, Sentinel-6) or large-swath altimeters (e.g. SWOT launched in December 2022), as well as other radar/optical missions (Sentinel-1, Sentinel-2) that provide high-resolution water masks. The limitations of each type of sensor are potentially circumvented when data from different satellite sensors are combined; the fusion of multi-source data has thus become one of the mainstream research topics in the remote-sensing community nowadays. Such fusion can be achieved with data assimilation algorithms applied to hydrodynamics models, namely MASCARET-1D and TELEMAC-2D. 
The present work focuses on the validation of water surface height (WSH) data from Sentinel-6MF with respect to in-situ gauge data, UAV and 1D/2D-hydrodynamics model outputs as shown in Figure 1. This work participates in a global effort that aims at combining various remote sensing products to represent and forecast flooding. The study is carried out over a dry period in June 2022 and over a flood event that occurred in December 2021-January 2022 over the Garonne catchment near Marmande, in the southwest of France. The WSH of the river is retrieved from Sentinel-6MF high-resolution fully-focused SAR data with an algorithm that relies on the estimation of the river width and the positioning of the river center line. The impact of these a priori data is investigated and the Sentinel-6MF-derived WSH observations are compared to the WSH simulated with TELEMAC-2D. It should be noted that due to the defection of Sentinel-1B (one of the two satellites in the Sentinel-1 constellation) in mid-December 2021, this flood event is only partly observed by Sentinel-1A and that the additional data from Sentinel-6MF with a 10-day revisit period are of great use. This study shows that hydrodynamic simulations and satellite altimetry time-series compare particularly well during the dry period whereas flooding events are often underestimated by satellite altimetry data. We believe that the combined use of satellite altimetry, hydrodynamics model simulations and independent UAV-borne data is key to a better understanding of the processes involved in the Garonne river flow dynamics and flooding events. We also take advantage of this study to improve our Sentinel-6MF data processing techniques.

Figure 1- Representation of water level height and flood extent with remote sensing data and hydrodynamic models.
 
On-fault damage evolution in laboratory earthquakes: a numerical perspective on fault complexity
Authors: Mollon Guilhem , Aubry Jérôme , Schubnel Alexandre
Published: February 2023

We propose a numerical model of laboratory earthquake cycle inspired by a set of experiments performed on a triaxial apparatus on sawcut Carrara marble samples. The model couples two representations of rock matter: rock is essentially represented as an elastic continuum, except in the vicinity of the sliding interface, where a discrete representation is employed. This allows to simulate in a single framework the storage and release of strain energy in the bulk of the sample and in the loading system, the damage of rock due to sliding, and the progressive production of a granular gouge layer in the interface. After independent calibration, we find that the tribosystem spontaneously evolves towards a stick-slip sliding regime, mimicking in a satisfactory way the behaviour observed in the lab. The model offers insights on complex phenomena which are out of reach in experiments. This includes the variability in space and time of the fields of stress and effective friction along the fault, the progressive thickening of the damaged region of rock around the interface, and the build-up of a granular layer of gouge accommodating shear. We present in detail several typical sliding events, we illustrate the fault heterogeneity, and we analyse quantitatively the damage rate in the numerical samples.
Oxygen isotopes in 2021 La Palma lavas reveal pre-eruptive magma storage and primitive mantle values
Authors: Troll Valentin , Deegan Frances , Bindeman Ilya , Harris Chris , Day James , Aulinas Meritxell , Geiger Harri , Perez Torrado Francisco , Carracedo Juan Carlos , Soler Vicente , Pinto Guillem , Albert Helena
Published: February 2023

Magma production, storage, and migration beneath volcanic ocean islands has been a matter of controversy and a multitude of methods are currently used to unravel magma evolution,  storage and migration processes. Here we report on a temporal sequence of lava samples1, 2 spanning the entirety of the 2021 La Palma eruption (19/09 to 13/12) for which time-series seismic information is also available. Based on the seismic data, initial tephrite lavas were likely drawn from a storage level at or just above the Moho (10-15 km depth), with increasing contributions from a deeper reservoir (>20 km depth) that delivered more primitive basanite lava as the eruption progressed. Early tephrite lava compositions changed rapidly during the first few weeks of the eruption and show significant oxygen isotopic variability (δ18O = +4.9 to 5.8‰), with some samples requiring a low-δ18O component. Later basanite lavas are compositionally less variable after day 20 of the eruption and show a narrower range in oxygen isotopes (δ18O = +5.3 to 5.7‰), close to Atlantic MORB values and similar to values from other historical eruptions and to earlier values recorded from the Cumbre Vieja volcanic system. The larger variability in δ18O in the early lavas is associated with significantly more radiogenic 187Os/188Os and the presence of amphibole and frequent gabbroic micro-xenoliths. Interaction with high-T altered Jurassic oceanic crustal gabbros and basalts with high-time-integrated Re/Os and variable δ18O could be an explanation for the initially wider variations in oxygen isotopes. This is in line with the seismic evidence that indicates the early lavas had been stored at (sub-)Moho levels within the Jurassic oceanic crust at ca. 8-15 km below the island prior to eruption. Later erupted magmas derive from a deeper, upper mantle storage level (>20 km depth) and have had little to no interaction with the igneous and sedimentary portions of the Mesozoic ocean crust, thus providing a useful estimate of primitive mantle δ18O values for the Western Canary Islands. 1Carracedo J.C., Troll V.R., Day J.M.D., Geiger H., Aulinas Junca, M., Soler V., Deegan F.M., Perez-Torrado F.J., Gisbert G., Gazel E., Rodríguez-González, A., and Albert H. (2022) The 2021 eruption of the Cumbre Vieja Volcanic Ridge on La Palma, Canary Islands. Geology Today 38: 94-107. 2Day J.M.D., Troll V.R., Aulinas M., Deegan F.M., Geiger H., Carracedo J.C., Pinto G.G., and Perez-Torrado F.J. (2022) Mantle source characteristics and magmatic processes during the 2021 La Palma eruption. Earth and Planetary Science Letters 597: 117793.
Spatio-temporally highly resolved validation of a rill-based soil erosion model with 4D data
Authors: Grothum Oliver , Favis-Mortlock Dave , Kavka Petr , Neumann Martin , Laburda Tomáš , Eltner Anette
Published: February 2023

Time-lapse photogrammetry has been proven to be a valuable tool to support the understanding of earth surface processes since it can be used to create 3D models with an unprecedented temporal resolution. Overlapping images are captured simultaneously and structure from motion (SfM) photogrammetry is used to reconstruct 3D point clouds from these images automatically.We performed one rainfall simulation on an erosion plot in the field covering about 16 square meters and having a slope of 9 degrees and another experiment in the laboratory with a plot of about 4 square meters and a slope of 20 degrees. Rainfall intensities were similar and high in both simulations to ensure rill formation. During the experiment, we measured soil surface changes with a time series of 3D point clouds derived via SfM photogrammetry. We also estimated runoff flow velocities with a tracer and observed the spatial pattern of runoff velocities with particle tracking velocimetry (PTV) applied to videos captured during the field experiment. At the plot outlet, we also measured runoff and sediment yield. These datasets were used as validation data for the soil erosion model.Soil erosion was simulated with the physically-based model RillGrow and SMODERP, which conceptualizes the formation of erosion rills as a self-organizing dynamic system. We ran several thousand erosion simulations using a Monte Carlo approach. The aim was first to assess the sensitivity of the input parameters of the model, and secondly to automatically find the best fitting set of input parameter values for the given field site conditions and rainfall intensity. We compare the simulation results to global values, such as the sediment yield and runoff, and to local changes, measured by the photogrammetric 4D data.Our study combines established as well as newly developed data recording and processing methods to create a spatio-temporal high-resolution dataset. This is used to test a soil erosion model with the aim of enhancing understanding of rill erosion processes.This research was supported by the projects DFG EL926/3-1, SFZP 085320/2022, SS05010180, and SGS OHK1-086/23/11143.
Exploring how a warmer Mediterranean Sea affects the origin and development of destructive Tropical-Like Cyclones
Authors: Ferretti Rossella , Liguori Giovanni , Cavicchia Leone , Miglietta Mario Marcello , Bonaldo Davide , Ricchi Antonio , Carniel Sandro
Published: February 2023

An enhanced understanding of Climate Change related implications in the maritime domain is needed in order to improve coastal infrastructure resilience and possible future operations, also in terms of climate security. Although the Mediterranean Sea is a relatively mild basin, it is however characterized by high geopolitical and economic relevance, occasionally showing intense cyclones with tropical-like characteristics known as Tropical-Like Cyclones (TLC). Many studies have highlighted that sea surface temperature (SST) distribution and anomalies play a crucial role in modulating the intense air-sea exchange, hence controlling both development and evolution of TLCs. However, given the complex interplay among ocean mixed layer, heat content and temperature, the role of the mixed layer depth (MLD) is of paramount importance. In this study we investigated the role of both SST anomaly, horizontal gradients and MLD profile on the origin and evolution of a recent record-breaking TLC (named IANOS). This cyclone originated over the southern Ionian Sea from 14 Sept 2020 to 19 Sept 2020, moving over the Central Ionian Sea from south-west to North-East, and made landfall over Greece mainland coast. It developed over a basin where a positive SST anomaly up to 4 °C was detected, which coincided with the sea area where it reached the maximum intensification and strength. We conducted a series of experiments using an atmospheric model (WRF - Weather Research and Forecasting system) driven by underlying SST (standalone configuration), either with daily update or coupled to a simple mixed-layer ocean model (SLAB ocean), with SST calculated at every time step using the SLAB ocean for a given value of the MLD. Sensitivity tests were performed increasing or decreasing MLD depth by 10 m, 30 m, 50 m, 75 m, 100 m, removing the horizontal gradients, removing the SST anomaly. Then, possible past and future climatological scenarios of MLD thickness were identified and tested. Preliminary results show that the MLD influences not only the intensity of the cyclone but also the structure of the precipitation field both in terms of magnitude and location. The fundamental role of the SST anomaly was also found to be essential to provide intense characteristics to IANOS. Results deserve further investigation in particular in the context of climate change scenarios that can provide useful insights into impact on coastal civil and military infrastructures in the whole Mediterranean region. 
The charge structure of thunderstorms revealed by the ground electric field monitoring network deployed in Tainan, Taiwan
Authors: Chen Alfred Bing-Chih , Chuang Chia-Wen
Published: February 2023

The generation and variation of the atmospheric electric field (hereafter E-field), which exists under all meteorological conditions and drives the charge flow around the Earth globally, and many natural phenomena such as lightning, thunderstorms, and even earthquakes have been observed accompanied by surface E-field disturbances; therefore, E-field observations are also used in disaster warnings. Since 2021, a ground E-field network consisting of three stations using in-house electric field mills has been deployed in the Tainan area, covering two known seismic faults, to monitor the characteristics of the e-field variation caused by diurnal cycle, thunderstorms, and earthquake precursor.The results indicated that the small-area E-field variation did not follow the Carnegie curve because local effects (aerosols, weather conditions, and environment) masked the variations of the global electrical circuit. In addition, the analysis of the disturbed E-field showed that more than 90% of the single-cell thunderstorms observed in the surface E-field could be classified as mature and dissipating stages. Each disturbance lasted approximately 34 minutes and was accompanied by an average of 1.4 times E-field phase reversals. Among them, the negative reversal of the surface electric field caused by the negative charge layer was relatively strong and frequent. Eventually, triangulation was used to reconstruct the charge structure of four distinctive single-cell thunderstorm events and restore the surface E-field responses during the passage of clouds. The correlation coefficients between the simulation and the observation were higher than 85%, and the trajectory and speed of the thunderclouds is also successfully reproduced by the recorded e-field data. Furthermore, some preliminary conclusions about earthquake precursors were drawn by analyzing the surface E-field.
Improving the temporal and spatial vegetation variability in land surface models based on satellite observations
Authors: van Oorschot Fransje , van der Ent Ruud , Hrachowitz Markus , di Carlo Emanuele , Catalano Franco , Boussetta Souhail , Balsamo Gianpaolo , Alessandri Andrea
Published: February 2023

Land-atmosphere interactions are largely controlled by vegetation, which is dynamic across spatial and temporal scales. Most state-of-the-art land surface models do not adequately represent the temporal and spatial variability of vegetation, which results in weaknesses in the associated variability of modelled surface water and energy states and fluxes. The objective of this work is to evaluate the effects of integrating spatially and temporally varying vegetation characteristics derived from satellite observations on modelled evaporation and soil moisture in the land surface model HTESSEL. Specifically, model fixed land cover was replaced by annually varying land cover, and model seasonally varying Leaf Area Index (LAI) was replaced by seasonally and inter-annually varying LAI. Additionally, satellite data of Fraction of green vegetation Cover (FCover) was used to formulate and integrate a spatially and temporally varying model effective vegetation cover parameterization. The effects of these three implementations on model evaporation and soil moisture were analysed using historical offline (land-only) model experiments at a global scale, and compared to reference datasets.The enhanced vegetation variability lead to considerable improvements in correlation of anomaly evaporation and surface soil moisture in semiarid regions during the dry season. These improvements are related to the adequate representation of vegetation-evaporation-soil moisture feedback mechanisms during water-stress periods in the model, when integrating spatially and temporally varying vegetation. These findings emphasize the importance of vegetation variability for modelling land surface-atmosphere interactions, and specifically droughts. This research contributes to the understanding and development of land surface models, and shows that satellite observational products are a powerful tool to represent vegetation variability.
Sensitivity of bias adjustment methods to low-frequency internal climate variability over the reference period: an ideal model study
Authors: Bonnet Remy , Vrac Mathieu , Boucher Olivier , Jin Xia
Published: February 2023

Climate simulations often need to be adjusted before carrying out climate impact studies at regional scale in order to reduce the biases often present in climate models. To do that, bias adjustment methods are usually applied to climate output simulations and are calibrated over a reference period. This period ideally includes good observational coverage and is often defined as the 2 or 3 more recent decades. However, on these timescales, the climate state may be influenced by the low-frequency internal climate variability. There is therefore a risk of introducing a bias to the climate projections by bias-adjusting simulations with low-frequency variability in a different phase to that of the observations. We proposed here a new pseudo-reality framework using an ensemble of simulations performed with the IPSL-CM6A-LR climate model in order to assess the impact of the low-frequency internal climate variability of the North Atlantic sea surface temperatures on bias-adjusted projections of mean and extreme surface temperature over Europe. We show that adjusting a simulation in a similar phase of the Atlantic Multidecadal Variability to that of the pseudo-observations reduces the pseudo-biases in temperature projections. Therefore, for models and regions where low frequency internal variability matters, it is recommended to sample relevant climate simulations to be bias adjusted in a model ensemble or alternatively to use a very long reference period when possible.
Mechanism of observed North Atlantic multidecadal upper ocean heat content changes 1950-202
Authors: Moat Ben , Sinha Bablu , Fraser Neil , Hermanson Leon , Josey Simon , MacIntosh Claire , Berry David , Williams Simon , Oltmanns Marilena , Jones Dan , Sanders Rachael
Published: February 2023

We synthesize observational datasets and a state of the art forced global ocean model to construct a multidecadal upper ocean heat budget for the North Atlantic for the period 1950 to 2020. Using multiple independent estimates of the variables allows us to provide robust uncertainty estimates for each term. Time-varying ocean heat transport convergence dominates the budget on multidecadal timescales in all regions of the North Atlantic. In the subpolar region (north of 45N) we find that the heat transport convergence is dominated by geostrophic currents whereas in the subtropics (26-45N) advection by ageostrophic currents is also significant. The geostrophic advection is dominated (especially in the subpolar regions) by anomalous geostrophic currents acting on the mean temperature gradient. The timescale and spatial distribution of the anomalous geostrophic currents are consistent with basin scale ‘thermal’ Rossby waves propagating westwards/northwestwards in the subpolar gyre. Multidecadal changes in North Atlantic Changes in ocean heat storage directly affect the climate of the surrounding continents, and hence it is important to understanding the mechanism behind these.
The changing pattern of rainfall erosivity and its impact on sediment load in the Loess Plateau, China: A case study of a typical watershed
Authors: Yu Kun-xia , Jia Lu , Xu Guoce , Li Peng , Li Zhanbin
Published: February 2023

The widespread occurrence of soil erosion reflects the accelerated deterioration of the surface ecological environment. The spatiotemporal variation of rainfall erosivity is the key driving factor for soil erosion by water, especially in the Loess Plateau in China. The Fenhe River basin in the Loess Plateau was selected as a case study based on the daily rainfall data from 1962 to 2019. Using a rainfall erosivity model based the daily rainfall, we studied the changing pattern. Furthermore, the impact of rainfall erosivity on sediment load was evaluated, and the possible causes for changes in sediment load were discussed. The results showed that the annual rainfall erosivity of the 12 weather stations experienced an insignificant change (p > 0.05). Moreover, before the 1980s, the decrease in annual watershed average rainfall erosivity may be the main reason for the decrease in annual sediment load, while after the 1980s, the construction of check dams may be the main factor leading to annual sediment load reduction, especially around 1993. However, the increase of vegetation was a main reason for the reduction of annual sediment load after 1999. Given Fenhe River basin as a typical watershed of the Loess Plateau, the study of rainfall erosivity and its impacts on the sediment in this area can provide a useful reference for further ecological construction and soil erosion control in the Loess Plateau.
Energy content of soil organic matter in soil profiles investigated by bomb calorimetry and DSC-TG
Authors: Lorenz Marcel , Diehl Dörte , Maskow Thomas , Thiele-Bruhn Sören
Published: February 2023

Soil organic matter (SOM) represents a continuum of progressively decomposing organic compounds mainly provided by primary producers and predominantly metabolized by adapted dynamic microbial communities. The carbon (C) in SOM flows through the microbial biomass, which needs – beside C and nutrients – Gibbs energy for growth and maintenance. The microbial metabolism and thus the degradation and stabilization of SOM follow thermodynamic laws. The thermodynamic perspective on soil systems is increasingly becoming the focus of research and has the potential to take us a substantial step towards a mechanistic understanding of SOM turnover and stabilization. An integral part of new bioenergetic concepts and models is the energy content of SOM, but the number of empirical studies dealing with soil C cycling or storage in relation to energy contents and flux is small.In this study, topsoil profiles (comprising organic forest floor horizons OL, OF, OH and the mineral soil layer 0-5 cm) at an afforested post-mining site were investigated to evaluate the influence of (i) soil depth – representing different stages of organic matter (OM) turnover – and (ii) litter quantity and quality (litterfall and fine root tissues) provided by different tree species (Douglas fir – Pseudotsuga menziesii, black pine – Pinus nigra, European beech – Fagus sylvatica, red oak – Quercus rubra) on the energy contents of SOM. The total energy content stored in soils and plant litter was determined using two calorimetric approaches: bomb calorimetry and differential scanning calorimetry combined with thermogravimetry (DSC-TG).The results of the litter inputs obtained with both methods showed the same trends: the C cycle in the soil was fueled by aboveground and belowground litter inputs, with energy-richer litterfall tissues (needles > leaves) compared to fine root tissues. However, with bomb calorimetry higher energy contents were generally observed in plant litter but also in the upper two forest floor horizons (OL, OF) of the soil profiles. The energy content per unit C (calorific value) changed with increasing depth due to the progressive turnover and stabilization of organic compounds but surprisingly, we identified opposite depth trends with both methods: bomb calorimetry revealed decreasing calorific values, while with DSC-TG increasing calorific values were determined. The few existing studies reported either the one trend or the other with ongoing decomposition, leading to different interpretations of the energetic driven microbial modulated formation and turnover of SOM.It is mandatory to overcome this fundamental challenge to achieve a reliable integration of the promising bioenergetic approaches into conceptual and modelling frameworks to assess SOC turnover and persistence based on robust empirical data.
Interactions of low-mode internal tides with mesoscale eddies in the Walvis Ridge region
Authors: Kourkouraidou Zoi , von Storch Jin-Song
Published: February 2023

Using the uncoupled model ICON-O with a high resolution of 5km, we aim to understand the working principles of interactions between low-mode internal tides and eddies such as their effect on internal mixing in the deep ocean. Such interactions can provide a direct energetic link between mesoscale processes and the internal wavefield. We focus the research on the Walvis Ridge region in the southeast Atlantic, since this is where energetic low-mode internal tides at the frequency of the principal lunar semidiurnal constituent (M2) are generated and propagate away from the ridge crossing the paths of eddies, which take the form of both Agulhas rings and other mesoscale features.Concentrating on the stationary changes in the internal wave properties, we identify the eddies in the area of interest and then investigate the vertical structure of the internal tidal properties in the vicinity of an eddy as well as far away from it. Preliminary results indicating such wave-eddy interactions are shown and discussed on the poster.
pointcloudset - A Python package to analyze large datasets of point clouds recorded over time
Authors: Goelles Thomas , Schlager Birgit , Muckenhuber Stefan
Published: February 2023

Point clouds can be acquired by different sensor types and methods, such as lidar (light detection and ranging), radar (radio detection and ranging), RGB-D (red, green, blue, depth) cameras, SfM (structure from motion), etc. In many cases multiple point clouds are recorded over time, sometimes also referred to as 4D point clouds. For example, automotive lidars from Ouster or Velodyne record point clouds at around 10-20Hz resulting in millions of points per second. In addition, monitoring with terrestrial laser scanners is becoming used more often. Producing similar datasets than the automotive lidars, although with larger individual point clouds at a lower frame rate.Analyzing such a large collection of point clouds is a big challenge due the size and unstructured nature of the data. The Python package "pointcloudset" provides a way to store, analyze, and visualize large datasets consisting of multiple point clouds recorded over time. Pointcloudset features lazy evaluation, parallel processing and is designed to enable the development of new point cloud algorithms and their application on big datasets. The package is based on the Python packages pandas, pytncloud, dask and open3D. Its API is easy to use and high level and the package is open source and available on GitHub. 