bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal Predictability of wintertime North Atlantic cyclonic activity through the NAO and the eddy-driven jet stream
Authors: Aranyossy Alvise , Brune Sebastian , Hellmich Lara , Dobrynin Mikhail , Krieger Daniel , Baehr Johanna
Published: March 2022

We investigate the potential for enhancing the seasonal prediction skill of mid-latitude cyclonic activity, represented by eddy kinetic energy (EKE) at 250 hPa over the North Atlantic and Europe, in hindcast simulations with the Max Planck Institute Earth System Model (MPI-ESM) against the ECMWF ERA5 reanalysis. Our analysis focuses on wintertime months (December-March) from 1982 to 2019, with a 30-member seasonal hindcast ensemble initialized every November 1st. Based on the initial confirmation that in both ERA5 reanalysis and MPI-ESM hindcasts, the eddy-driven jet stream and the wintertime North Atlantic Oscillation (NAO) play a significant role in wintertime's spatial and temporal distribution of mid-latitude cyclonic activity, we perform ensemble subsampling.

Specifically, we sample each winter so that a northern position of the jet stream is consistent with a positive phase of the NAO and represents poleward enhanced EKE activity. In contrast, a southern position of the jet stream is consistent with a negative phase of the NAO and represents equatorward enhanced EKE activity. Preliminary analysis of the predictive skill of MPI-ESM hindcasts with respect to ERA5 shows that such subsampling with respect to a consistent representation of the jet stream position and the NAO phase leads to improvements over the skill from the 30-member ensemble mean, with significant correlations concentrated over areas of major frequency of storm tracks. Our results put into practical use that an enhanced representation of the large-scale climate variability plays a crucial role in the long-term prediction of high-frequency events such as mid-latitude cyclones.
 An improved workflow to efficiently compute local seismic probabilistic tsunami analysis (SPTHA): a case study for the harbour of Ravenna (Italy)
Authors: Baglione Enrico , Brizuela Beatriz , Volpe Manuela , Armigliato Alberto , Zaniboni Filippo , Tonini Roberto , Selva Jacopo
Published: March 2022

We present a refined methodological procedure for computationally efficient local SPTHA based on regional SPTHA.  The adopted procedure extracts from the regional SPTHA the most impacting tsunami sources at the investigated site, and reconstructs hazard curves on high-resolution topobathymetric models based on a reduced set of inundation simulations. This procedure enhances the original workflow for local SPTHA quantification described by Volpe et al. (2019), applying some significant upgrades to simplify its application and improve the accuracy of the results. In particular, the description of local sources has been refined through a more detailed discretization of the natural variability (aleatory uncertainty), eventually reducing the epistemic uncertainty. Then, a more efficient filtering procedure, based on the strategy proposed by Williamson et al. (2020), is adopted to select a subset of scenarios to be modelled at high resolution, eventually reducing the epistemic uncertainty introduced by this selection. This allows to perform only coarse-grid simulations after the regional source filtering and local source refinement, and then combine coarse-grid results with fine-grid topography. Overall, the resulting method simplifies the original one, improving accuracy and decreasing uncertainty. The newly developed procedure is applied to an illustrative case study for the harbour of Ravenna (Northern Adriatic Sea, Italy).
The timing, duration and magnitude of the 8.2 ka event in global speleothem records
Authors: Parker Sarah , Harrison Sandy P.
Published: March 2022

Abrupt events punctuate the climate of the Holocene epoch, providing valuable insight into rapid climate change. The most notable abrupt event of the Holocene was the 8.2 ka event, when a large influx of meltwater into the North Atlantic reduced northward heat transport in this region. The event provides valuable insight into the global climate response to North Atlantic freshening. Here, we examine the timing, duration and magnitude of the climate response using a global network of speleothem oxygen isotope (δ18O) records.

Firstly, we objectively identified abrupt climate events in 402 globally distributed speleothem records from the SISAL (Speleothem Isotopes Synthesis and AnaLysis) database (Atsawawaranunt et al., 2018; Comas-Bru et al., 2020) during the Holocene. Secondly, we examined the timing, duration and anomalies of the 8.2 ka δ18O excursions using 70 speleothem δ18O records.

We show that the 8.2 ka event is the most globally coherent and significant abrupt event of the last 12,000 years, with an abrupt δ18O excursion identified in >70% of speleothem records. The δ18O anomalies are regionally homogeneous; they are negative across Europe and the Mediterranean, positive across Asia, and negative in South America and southern Africa. The excursion is not registered in the Indonesia/Australia region. The median timing of the event from the speleothem records is 8223 ±12 to 8062 ±14 years BP, indistinguishable from the timing in Greenland ice cores of 8247 to 8086 ± 47 years BP (Thomas et al., 2007). The median duration of the 8.2 ka event excursion in speleothems is 159 ±11 years, indistinguishable from the duration in Greenland of 160.5 ± 5.5 years (Thomas et al., 2007). There is no significant difference between the timing and duration in regions both near (Europe) and far (Asia) from the North Atlantic. This globally synchronous timing and duration supports a rapid and widespread climate response, likely via rapid atmospheric teleconnections.

 

Atsawawaranunt, K., et al., 2018. The SISAL database: a global resource to document oxygen and carbon isotope records from speleothems. Earth System Science Data, 10(3), pp.1687-1713.

Comas-Bru, L., et al., 2020. SISALv2: a comprehensive speleothem isotope database with multiple age–depth models. Earth System Science Data, 12(4), pp.2579-2606.

Thomas, E.R., Wolff, E.W., Mulvaney, R., Steffensen, J.P., Johnsen, S.J., Arrowsmith, C., White, J.W., Vaughn, B. and Popp, T., 2007. The 8.2 ka event from Greenland ice cores. Quaternary Science Reviews, 26(1-2), pp.70-81.
Carbonate triple oxygen isotope analyses of brachiopod shells
Authors: Bajnai David , Jäger Oliver , Pack Andreas
Published: March 2022

The 18O/16O ratio (δ18O) and the clumped isotope composition (∆47) of marine carbonates are widely used proxies of Earth’s past seawater temperature. However, kinetic isotope fractionation effects occurring during carbonate precipitation and diagenesis complicate their use as climate proxies. Specifically, the failure to identify disequilibrium precipitation and post-depositional alteration in the investigated samples could lead to biased temperature estimates [1,2]. The identification of these effects using the δ18O and the ∆47 proxies are not straightforward. The triple oxygen isotope method, that is, the combined analyses of the 18O/16O and the 17O/16O ratios, expands the traditional oxygen (and clumped isotope) scheme by another dimension, thus providing information on the nature and extent of kinetic effects involved in carbonate formation and the subsequent diagenetic processes [2].

In this study, we measured the triple oxygen isotope composition (∆17O) of modern and fossil brachiopods. Brachiopods are an important group of calcifiers because they are abundant in the sedimentary archive and present since the Cambrian. We show how triple oxygen isotope analyses can help identify and disentangle kinetic effects and diagenesis and ultimately provide a more accurate palaeotemperature estimate.

[1] Bajnai et al. (2018) Sci Rep

[2] Wostbrock et al. (2020) GCA
ITRF2020: main results and key performance indicators
Authors: Altamimi Zuheir , Rebischung Paul , Collilieux Xavier , Metivier Laurent , Chanard Kristel
Published: March 2022

More than 30 years of space geodetic data have been reprocessed
by the International Association of Geodesy technique services
and submitted to compute the new realization of the
International Terrestrial Reference System (ITRS). The new
realization, ITRF2020, is intended to replace ITRF2014. It is
provided in the form of an augmented reference frame so that in
addition to station positions and velocities, parametric
functions for both post-seismic deformation (PSD) and seasonal
signals (expressed in the Center of Mass frame derived from
Satellite Laser Ranging data) will also be delivered to the
users. The presentation summarizes the main results of ITRF2020
analysis and evaluates its internal consistency via some key
performance indicators. In particular, the paper discusses the
level of the scale agreement between the four techniques, its
linear and nonlinear time evolution, and the strategy adopted
for the ITRF2020 scale definition. In addition, we evaluate the
performance of the parametric functions for both seasonal
signals and PSD and the level of consistency between the four
techniques at colocation sites.
Pore-scale modeling of acid etching in a carbonate fracture
Authors: Lu Renchao , Miao Xing-Yuan , Kolditz Olaf , Shao Haibing
Published: March 2022

Acid fracturing has been widely used in the oil and gas industry to increase permeability in carbonate reservoirs. In recent years this chemical stimulation technique has been borrowed from the oil and gas industry, employed in the enhanced geothermal systems at Groß Schönebeck, Germany (Zimmermann et al., 2010), and at Soultz-sous-Forêts, France (Portier et. al., 2009). In concept, acid fracturing utilizes strong acids that react with acid-soluble rock matrix in order to non-uniformly etch fracture surfaces. The permeability-enhancing effect depends upon the degree of surface irregularity after pore-scale acidizing which is affected by the compositional heterogeneity of the reacting rock matrix, fracture aperture heterogeneity, and flow and transport heterogeneity. In order to have an insight into these impacts on the acid etching process with the final goal of determining optimum operating conditions (e.g., acid type and acid injection rate), a pore-scale acid-fracturing model is needed. The core components of the pore-scale acid-fracturing model consist in tracking the motion of the fluid-matrix boundary surface induced by acid etching. To date, a number of front tracking approaches (e.g., local remeshing technique, embedded boundary method, immersed boundary method, and level-set method) have been proposed by many researchers in order for moving boundary problems. Each approach has its pros and cons. In this work, we propose employing the phase-field approach as an alternative to the existing front tracking approaches to capture the physically sharp concentration discontinuities across the liquid-solid interface. The developed pore-scale acid-fracturing model includes the Stokes-Brinkmann equations for fluid flow in the fracture-matrix system, the multi-component reactive transport equation for transport of solute species in the rough-walled fracture, and the phase-field equation for the reaction-driven motion of the fluid-matrix boundary surface. Through this numerical study, we demonstrate that the phase-field approach is viable to track recession of carbonate fracture surface by acid etching and to capture the solute concentration jump (w.r.t., Ca2+, H+, and HCO3−) across the solid-liquid interface.

 

Reference

Zimmermann, G., Moeck, I. and Blöcher, G., 2010. Cyclic waterfrac stimulation to develop an enhanced geothermal system (EGS) — conceptual design and experimental results. Geothermics, 39(1), pp.59-69.

Portier, S., Vuataz, F.D., Nami, P., Sanjuan, B. and Gérard, A., 2009. Chemical stimulation techniques for geothermal wells: experiments on the three-well EGS system at Soultz-sous-Forêts, France. Geothermics, 38(4), pp.349-359.
Modelling solar-induced chlorophyll fluorescence using the P-model, an optimality-based model for vegetation productivity.
Authors: Morfopoulos Catherine , Gu Chuanxin , Iain Colin Prentice
Published: March 2022

Photosynthesis is the core engine of vegetation productivity, usually estimated by Gross Primary Production (GPP), the rate of carbon fixed by photosynthesis per unit of ground area. A better understanding of ecosystem productivity relies on two main streams of information: observations and modelling. However, both streams have severe limitations with respect to GPP: 1- no large-scale measurements exist for GPP, 2- while satellites typically measure light reflectance by foliage, the light reactions (i.e., light absorption by photosystems generating reduction power and energy for carbon-fixation) are still described empirically in vegetation models.

Part of the energy absorbed by the Chlorophyll pigments is radiatively dissipated through fluorescence. In the recent years, using narrow band observations in the oxygen A-band, first global Solar Induced Chlorophyll Fluorescence (SIF) measurements were obtained opening a new insight for estimates of vegetation photosynthesis. Yet, fluorescence quenching is a passive energy quenching and fluorescence yields are dependant of the faction of energy used for photochemistry and dissipated through non-photochemical quenching (NPQ). Thus direct comparison between GPP and SIF can lead to misinterpretation.

In this study, we append the P-model to include SIF simulations. The P-model is a new-generation vegetation model based on optimality principles and require minimal parametrisation. Two approaches to simulate fluorescence yield are tested. The first one is based on the van der Tol et al. (2014) fluorescence model and simulate fluorescence using an empirical method. The second is based on recent development from Johnson and Berry (Johnson and Berry, 2021), who proposed a process-based model for partitioning absorbed light between photochemistry, NPQ and fluorescence. The two approaches are evaluated and assessed against SIF satellite products.
Seismicity and the deformation of subducting slabs
Authors: Craig Tim
Published: March 2022

Earthquakes associated with the subduction of tectonic plates into the Earths’ interior occur in four dominant settings: (i) major seismic failure on the interface between the two plates (the subduction “megathrust”); (ii) shallow crustal earthquakes within the overriding plate; (iii) earthquakes within the outer rise region of the downgoing plate, as it bends into the subduction zone; and (iv) earthquakes that occur within the subducting slab as it descends into the mantle. These latter two classes of earthquakes reflect the internal deformation of the downgoing plate, and are the focus for this talk.  

Both of these types of intraslab, or intraplate, earthquakes are principally driven by bending of the plate.  The bending and flexure of subducting plates creates complex stress and strain fields, which are highly variable across short distances, both vertically and laterally.  This leads to complex patterns of intraplate seismicity, which offers our principal insight into the dynamics of the subducting slab.  Beyond this, these intraslab earthquakes offer our main observational constrains on the rheology of the slab, and its rheological evolution over the its initial stages of subduction.  From the potential for fluid infiltration into the subducting plate at the outer rise, to the role that metamorphism and fluid release play in permitting intermediate depth intraslab seismicity, these earthquakes also relate to the chemical evolution of the plate during subduction.  Lastly, although less common, and usually smaller in magnitude, than earthquakes occurring on the subduction interface, intraplate subduction zone earthquakes pose a critical, and often under-appreciated, hazard for the overlying regions, particularly given their potential to trigger secondary hazards in the setting of the supra-subduction arc.

Here, I will consider earthquakes associated with the internal deformation and bending of subducting plates through the initial phases of subduction, from an intact oceanic plate entering the subduction zone to the descent of the plate into the mid-mantle, the controls on their occurrence, and their geodynamic implications. 
Electric Field Turbulence in the Solar Wind from MHD down to Electron Scales: Artemis Observations
Authors: Salem Chadi , Bonnell John , Huang Jordan , Chaston Christopher , Franci Luca , Klein Kristopher , Verscharen Daniel
Published: March 2022

Recent observational and theoretical work on solar wind turbulence and dissipation suggests that kinetic-scale fluctuations are both heating and isotropizing the solar wind during transit to 1 AU.  The nature of these fluctuations and associated heating processes are poorly understood. Whatever the dissipative process that links the fields and particles - Landau damping, cyclotron damping, stochastic heating, or energization through coherent structures - heating and acceleration of ions and electrons occurs because of electric field fluctuations. The dissipation due to the fluctuations depends intimately upon the temporal and spatial variations of those fluctuations in the plasma frame.  In order to derive that distribution in the plasma frame, one must also use magnetic field and density fluctuations, in addition to electric field fluctuations, as measured in the spacecraft frame (s/c) to help constrain the type of fluctuation and dissipation mechanisms that are at play.

We present here an analysis of electromagnetic fluctuations in the solar wind from MHD scales down to electron scales based on data from the Artemis spacecraft at 1 AU. We focus on a few time intervals of pristine solar wind, covering a reasonable range of solar wind properties (temperature ratios and anisotropies; plasma beta; and solar wind speed). We analyze magnetic, electric field, and density fluctuations from the 0.01 Hz (well in the inertial range) up to 1 kHz. We compute parameters such as the electric to magnetic field ratio, the magnetic compressibility, magnetic helicity, compressibility and other relevant quantities in order to diagnose the nature of the fluctuations at those scales between the ion and electron cyclotron frequencies, extracting information on the dominant modes composing the fluctuations. We also use the linear Vlasov-Maxwell solver, PLUME, to determine the various relevant modes of the plasma with parameters from the observed solar wind intervals. We discuss the results and the relevant modes as well as the major differences between our results in the solar wind and results in the magnetosheath.
Products of Sedimentary Volcanism around Adamas Labyrinthus, Mars
Authors: Cuřín Vojtěch , Brož Petr , Hauber Ernst , Markonis Yannis
Published: March 2022

Landforms with specific flow-like morphology are characteristic for the area of Adamas Labyrinthus in the southwestern part of Utopia Planitia. These landforms have been previously described as degraded mud flows originating from a partly frozen muddy ocean. However, such interpretation remained ambiguous as lava flows observed elsewhere on Mars look quite similar. We mapped and investigated over 300 features spread across a 500 × 1300 km large area in order to reveal whether they were formed by the movement of mud or lava. Based on our systematic examination of their shapes, their spatial distribution as well as geological context we conclude that they were formed due to the ejection of mud from a gradually freezing muddy body. Once exposed to the surface, the mud spread by flowing over the surface, while freezing at the same time. This limited its ability to flow and caused the resulting outflows to have an appearance similar to terrestrial lava flows. Emergent landforms differentiated based on the effusion rates and overall volumes of the source material and subsequently degraded over time as the liquid part of the compound sublimed away. These processes eventually lead to the characteristic morphology of hills, ridges, plateaus, and complexly layered units which we observe today. We propose that all the >300 studied features were formed by subsurface sediment mobilization and that the material likely originated from the same source.
A minimal SDE model of D-O events with multiplicative noise
Authors: Kypke Kolja , Ditlevsen Peter
Published: March 2022

The abrupt transitions in the last glacial period between cold stadial and warmer interstadial climate states found in Greenlandic ice-core records, known as Dansgaard-Oeschger (D-O) events, are a rich topic of study not only due to their potential similarities in time scales and mechanisms to present and near-future climate transitions but also since their underlying physical mechanisms are not fully understood. The dynamics of the climate can be described by a Langevin equation dx = −∂U/∂x dt + η(t) where the potential U(x) has a bimodal distribution to represent the stable stadial and interstadial states and the stochastic process η(t) is usually realized as a Gaussian white noise process that causes jumps between these two states. From the steady-state of the Fokker-Planck equation associated with this Langevin equation, the potential U(x) can be determined from the probability distribution of the ice-core record time series. Thus this minimal model simulates time series with statistics similar to those of the original ice-core record. Novel to this study, we introduce a multiplicative noise term η(t, x) to represent the different statistical properties of the noise in the stadial and interstadial periods. The difference between the Itô and the Stratonovich integration of the Langevin equation with multiplicative noise results in slight differences in the attribution of the drift and diffusion terms for a transformed variable. This is illustrated by performing both.
Mexican agricultural frontier communities differ in forest dynamics with consequences for conservation and restoration
Authors: Lohbeck Madelon , Devries Ben , Bongers Frans , Martinez-Ramos Miguel , Navarrete-Segueda Armando , Nicasio-Arzeta Sergio , Siebe Christina , Pingarroni Aline Pingarroni , Wies Germán , Decuyper Mathieu
Published: March 2022

Forest regrowth is key to achieve restoration commitments, but a general lack of understanding when it occurs and how long secondary forests persist, hampers effective upscaling. We quantified spatiotemporal forest dynamics in a recently colonized agricultural frontier in southern Mexico, and tested how temporal variation in climate, and cross-community variation in land ownership, land quality and accessibility affect forest disturbance, regrowth and secondary forest persistence.

We consistently found more forest loss than regrowth, resulting in a net decrease of 45% forest cover (1991-2016) in the study region. Secondary forest cover remained relatively constant while secondary forest persistence increased, suggesting that farmers are moving away from shifting cultivation. Temporal variation in disturbance was explained by annual variation in climatic variables and key policy and market interventions.

We found large differences in forest characteristics across communities, and these were explained by differences in land ownership and soil quality. Forests were better conserved on communal land, while secondary forest was more persistent when farms were larger and soil quality is better. At the pixel-level both old forest and secondary forests were better represented on low-quality lands indicating agricultural concentration on productive land. Both old forest and secondary forest were less common close to the main road, where secondary forests were also less persistent.

We demonstrate the suitability of timeseries analyses to quantify forest disturbance and regrowth and we analyse drivers across time and space. Communities differ in forest dynamics, indicating different possibilities, needs and interests. We warrant that stimulating private land ownership may cause remaining forest patches to be lost and that conservation initiatives should benefit the whole community. Forest regrowth competes with agricultural production and ensuring farmers have access to restoration benefits is key to restoration success.
Initial results of modelling 3D plate dynamics in the Alpine-Mediterranean area
Authors: Schuler Christian , Kaus Boris , Le Breton Eline , Riel Nicolas
Published: March 2022

Tectonic reconstructions of lithospheric plate motion can be approached by different geological methods. However hypotheses derived from these findings are often not validated in a physically consistent manner. Therefore we employ 3D geodynamic modelling in order to test geological reconstructions.

In this work, 3D thermomechanical forward simulations of the Alpine-Mediterranean area are conducted using the software LaMEM (Kaus et al. (2016)). A viscoelastoplastic rheology and an internal free surface are applied, which means that apart from the internal dynamics also the surface response can be investigated. Kinematic reconstructions of Le Breton et al. (2021) at 35 Ma serve as an initial setup for the simulations. The goal of these simulations is to determine the main driving forces of plate dynamics in this area. This is done by evaluating effects of different model parameters such as the thermal structure and the geometry of the slabs, the viscosity of the mantle and brittle parameters of the crust.

The geodynamic behaviour of the Alpine-Mediterranean area is dominated by various subducting plates which makes it particularly difficult to distinguish the unique influence of different geodynamic processes. The Adriatic microplate plays a key role in the development of the Alpine Orogeny and its plate motion and therefore serves as a marker as it is possible to compare the current position of this plate with the simulation itself. Even though these forward simulations are not capable of exactly reconstructing the current tectonic setting, they provide insights into parameters which influence the subduction dynamics.

First results suggest that the plate motion of Adria is primarily driven by the interaction of the Calabria slab and the Hellenic slab and that the propagation of these slabs strongly depends on the slab geometry and the initial trench location. Furthermore the spreading rate of rifting in the Liguro-Provençal Basin massively affects the timing of Adria’s plate motion.

 

Kaus, B. J. P., A. A. Popov, T. S. Baumann, A. E. Pusok, A. Bauville, N. Fernandez, and M. Collignon, 2016: Forward and inverse modelling of lithospheric deformationon geological timescales. Proceedings of NIC Symposium.

Le Breton, E., S. Brune, K. Ustaszewski, S. Zahirovic, M. Seton, R. D. Müller, 2021: Kinematics and extent of the Piemont–Liguria Basin–implications for subduction processes in the Alps. Solid Earth, 12(4), 885-913.

 

 

 

 

 

 
Can catchment scale implementation of green infrastructure protect the flow regime of an urban stream facing urbanisation and climate change ? A modelling study in Lyon, France.
Authors: Bonneau Jérémie , Branger Flora , Castebrunet Hélène
Published: March 2022

Urbanisation and climate change jeopardize the health of peri-urban streams, by yielding decreased baseflow and increased peakflows. Green infrastructure can help protecting and even restoring urban streams by storing, infiltrating and losing urban runoff to evapotranspiration. However, whether green infrastructure implementation at the catchment-scale (and how much) can counter future urbanisation and climate change remains a question of interest for urban managers. We modelled the hydrology of a 20 km2 peri-urban catchment in the western suburbs of Lyon, France with the physically-based, spatially distributed hydrological model J2000P, at the hourly time step. We created 12 future urbanisation scenarios with stepwise increases of impervious cover as well as 36 climate change scenarios based on one climate projection (CNRM-CM5-ARPEGE- ALADIN63-RCP 8.5) and the observed temperature and precipitation records from the city of Orange, which is located 200 km south of Lyon in France. We applied a delta method to transform current hourly rainfall and evapotranspiration timeseries into potential future climate timeseries. We coupled these scenarios to stormwater management strategies, through the integration of a site-scale model of green infrastructure into J2000P. Five stormwater management strategies with increasing implementation of green infrastructure were tested: from ‘no green infrastructure’ to ‘all impervious areas drained into green infrastructure’. 640 scenarios coupling urbanisation, climate and stormwater management scenarios were simulated. For each simulation a range of hydrological indicators were calculated. We found that catchment-scale implementation of green infrastructure could mitigate the hydrological impacts of urbanisation. Sewer overflow were particularly sensitive to green infrastructure and urbanisation. Green infrastructure was however unable to mitigate the impact of climate change on the stream flow regime, because green infrastructure only impacted the urban parts of the catchment that accounted for less than 15% of the whole catchment. Non-urban areas (forests, pastures), which contributed very strongly to the flow regime, were impacted by climate change but not significantly by urban stormwater management strategies. These results can inform urban planners and water managers of the great potential of green infrastructure (reduction of sewer overflows, compensation for urbanisation) but also its limitations (little impacts on catchment scale induced flow peaks and droughts).
The record of the End Triassic Extinction in southern Tethyan carbonate platforms
Authors: Falzoni Francesca , Montanaro Andrea , Iannace Alessandro , Parente Mariano
Published: March 2022

The End Triassic Extinction (ETE), one of the “big five” of the Phanerozoic, caused a severe loss of biodiversity both in the continental and in the marine realm. The ETE has been linked with enhanced volcanism of the Central Atlantic Magmatic Province (CAMP), which injected a large amount of CO2 in the ocean-atmosphere system, triggering major paleoenvironmental perturbations including climate change, ocean acidification and marine anoxia.

In the marine realm, shallow-water benthic biocalcifiers of subtropical carbonate platforms were severely affected, with reef-building scleractinian corals and calcisponges, large megalodontid bivalves, involutinid benthic foraminifers and dasycladalean algae being among the most famous victims. In the classical localities of the Northern Calcareous Alps and Transdanubian Range, the ETE coincides with the demise of the Dachstein-type carbonate platform, which is generally sharply overlain by relatively deep-water facies of outer ramp to basinal environment. This stratigraphy has been interpreted as recording subaerial exposure of the carbonate platform, associated to a sea-level drop in the late Rhaetian that generated a hiatus of variable and generally poorly constrained duration, followed by drowning during transgression in the Early Jurassic.

A different stratigraphic evolution is recorded in some areas of the southern Tethyan margin (i.e., the southern Apennines and Sicily in southern Italy, Greece, the United Arab Emirates and Oman) where carbonate platform facies persist across the Triassic/Jurassic boundary. Stratigraphic sections in these areas are particularly significant to document the evolution of biodiversity of shallow-water benthic biocalcifiers across the ETE interval.

In this study we present new data on the stratigraphic distribution and changes in abundance of benthic foraminifers in two latest Triassic–earliest Jurassic carbonate platform sections of the southern Apennines (Italy) and Pelagonian domain (Greece). We document a decline in diversity and abundance of involutinid benthic foraminifers predating the extinction of several genera in the latest Rhaetian. Carbon isotope profiles of the studied sections show a complicated pattern of repetitive high-frequency negative excursions, seemingly related to local paleoenvironmental and/or early diagenetic features. However, by integrating bio- and carbon isotope stratigraphy we are able to correlate the studied sections with other persistent carbonate platform sections and with reference sections of the Lombardy Basin and of the Northern Calcareous Alps.
40Ar/39Ar In-Situ Dating of Altered Mafic Rocks in the Karoo Large Igneous Provinces.
Authors: Antoine Clémentine , Spikings Richard A. , Gaynor Sean P. , Schaltegger Urs
Published: March 2022

Dating of the extrusive parts of large igneous provinces has been a challenge because of the lack of mineral phases that can be dated by high-precision techniques. This is the case for the rapidly emplaced Drakensberg lavas, part of the Karoo LIP in South Africa and Lesotho. The circulation of hot fluids through the lava stack during rapid emplacement of continental flood basalts develops relatively high degrees of fracturing and alteration of the rocks, which often results in the re-opening of isotopic systems and inaccurate dates. This alteration occurs on varying length scales, from the outcrop to the micrometric scales, creating Argon loss in minerals of interest for 40Ar/39Ar dating (i.e. plagioclase) and making the procedure of separation for step-heating 40Ar/39Ar a tedious and sometimes ineffective task. Here, we re-approach measuring 40Ar/39Ar by directly analyzing leached and unleached thin sections without having to go through mineral separation, and therefore effectively eliminating the mixing issue of mechanically separating the plagioclase crystals. Half of each plagioclase aliquot was leached in acid, and then irradiated at the TRIGA reactor (Oregon State). We used a 193nm excimer UV-laser attached to a noble gas extraction and purification line, and an Argus VI mass spectrometer at the University of Geneva on thick sections for in-situ analysis. Plagioclase separates from the same Karoo lava flow samples were previously analyzed for 40Ar/39Ar geochronology using step heating, on aliquots of both leached and unleached plagioclase separates, using the same noble gas analytical equipment. This allows for a direct comparison of the in-situ­ analysis, testing the potential differences between the two different analytical systems and a potential way of assessing differences in accuracy between the two. Preliminary results show that accurate ages can be achieved by this technique at the cost of a larger precision.  
Volatile emissions in spruce could act as cues for bark beetle host selection
Authors: Lehmanski Linda , Hartmann Henrik
Published: March 2022

The last decades have been marked by an increase in spruce mortality, partially triggered by the European spruce bark beetle Ips typographus. More frequent extreme weather events presumably prompted by climate change have led to rising stress and susceptibility of trees, a fragility which the bark beetle can exploit for its advantage. One aspect of the beetles’ life cycle that is not fully understood is the selection by pioneer beetles of an appropriate hosts that allows successful infestation. While it is often suggested that volatile or olfactory cues determine the suitability of a tree as host and that beetles generally tend to attack weakened trees, methodological challenges in field studies have so far hampered progress in empirical process understanding. Here we present a methodological approach for quantification and qualification of volatile emissions in situ. The method consists from a mobile GC/MS which is implemented into a stem incubation chamber system. We report preliminary results of in situ assessment of volatile compounds emitted by spruce trees as a first step toward a better understanding in tree-insect interactions.
Geochemical analysis of microbiologically treated red mud
Authors: Fajković Hana , Huljek Laura , Vrkić Ivana , Ivanković Tomislav , Fiket Željka , Gotovac Atlagić Suzana , Sukur Sunčica , Tomašić Nenad
Published: March 2022

Historical disposal sites of red mud can be found all around Europe, most notably at Sardinia, in Hungary, or at many locations in East-Southeast Europe. Red mud contains dominantly iron, aluminum, and silicon oxides, with races of various metals and compounds that can still be reprocessed if appropriate methods are applied. Some of the promising methods include microorganisms, and in particular bacteria.

The main objective of the study was to determine whether prolonged bacterial activity changes the geochemistry of the red mud. The bacteria for the experiment were isolated through several selective steps from activated sludge of wastewater treatment plant and red mud from three different locations: Dobro Selo and Zvornik (Bosnia and Herzegovina), and Almásfüzitő (Hungary).

After successful isolation, the bacteria were applied to the homogenized red mud samples, with nutrient media and water added in different combinations and ratios. The experiment lasted for 6 months after the bacteria were first applied to the red mud samples. During this period, geochemical analyses of the red mud were carried out twice, after 4 weeks and after 24 weeks, while the analysis of bacterial survival and quantity in the red mud samples were carried after 4, 8, and 24 weeks. The goal of geochemical analyses was to determine whether the bacteria caused changes in the concentrations of the elements of interest in the red mud when used as cultivating substrate and whether the elements of interest became more available to the bacteria due to their growth and adaptation to the red mud.

Prior to geochemical analysis, subsamples were heated at 100°C for 60 minutes to induce bacteriolysis and filtered twice with MiliQ water (red band filter paper). The eluates were stored in plastic cuvettes and kept in a dark place at 4°C until analysis (HR-ICP-MS). The filter papers containing the treated red mud were dried, sealed, and stored for further geochemical analysis of total major and trace element concentrations by ICP-MS and mineralogical (XRPD) analyses. Detailed results of the geochemical and mineralogical analyses are pending.

This work has been supported by EIT Raw Materials project RIS-RESTORE, project number 19269.
Where, when and why do extratropical cyclones cluster?
Authors: Dacre Helen , Pinto Joaquim
Published: March 2022

The weather conditions in the mid-latitudes are largely determined by the absence or presence of extratropical cyclones. Frequent passage of cyclones over the same location in quick succession (serial clustering) can lead to accumulated impacts such as flooding and wind damage. These impacts have motivated a wide variety of research studies into serial cyclone clustering.  However, the different definitions, metrics and datasets used in this research makes comparison of results difficult.  The aim of this study is to review the previous research and provide clear a framework for serial cyclone clustering into which past and future studies can be placed, allowing easier comparison of results irrespective of the research direction.

 

We find that several climatologies of serial cyclone clustering agree as to where clustering occurs preferentially, but these studies are largely limited to the North Atlantic. Future projections of cyclone clustering are highly uncertain.  This is largely due to sample uncertainty, caused by short timeseries, and poor representation of key processes such as Rossby wave breaking, caused by low spatial resolution. Research investigating the dynamical mechanisms determining when and why serial cyclone clustering occurs have shown that clustering is linked to the position of the jet stream and the occurrence of Rossby wave breaking.  Studies have investigated this link for different aggregation timescales. On daily timescales cyclone clustering is related to jet streaks and families of cyclones forming on the same frontal feature. On seasonal timescales active seasons are often associate with persistent large-scale flow patterns and successive Rossby wave breaking events. Current knowledge gaps and future research directions are identified.
Detection and tracking of individual surface breaking waves from a fixed stereo video system
Authors: Peach Joseph , Callaghan Adrian , Bergamasco Filippo , Benetazzo Alvise , Barbariol Francesco
Published: March 2022

Sea surface wave breaking is the dominant process that results in dissipation of ocean surface wave energy. During the breaking process, wave energy is converted into turbulent kinetic energy, and if significantly energetic, entrains air which facilitates air-sea gas transfer and scatters light to create the signature whitecap. Exploiting the broadband scattering of light by the surface whitecaps, this study uses a fixed stereo video system to detect and track individual air-entraining surface breaking waves at wind speeds of up to 16 m/s. The sea surface foam (whitecap) from a breaking event is detected in grayscale images using a brightness thresholding technique based on the image pixel intensity histogram. The movement of individual whitecaps is estimated with optical flow and is used to track whitecaps between consecutive frames. Once breaking events have been tracked through their lifetime, fundamental properties of the whitecap such as the time-evolving foam area [m2], breaking speed [m/s], average crest length [m] and foam area growth and decay timescales [s] are extracted and subsequently aggregated into whitecap statistics. The geometric, kinematic and dynamic quantities obtained for individual whitecaps via this tracking method are used in conjunction with the volume-time-integral method developed in Callaghan et al 2016 to estimate the energy dissipated by each individual whitecap and to then develop an empirical frequency-dependent whitecap energy dissipation source term.
Combining field survey and time series data to learn about plant water usage in a South African agroforestry system
Authors: Hoffmeister Svenja , Hassler Sibylle K. , Kestel Florian , Maier Rebekka , Zehe Erwin
Published: March 2022

Agroforestry systems (AFSs) are associated with many benefits such as augmented soil fertility or enhanced biodiversity. However, in water-limited areas the competition over water resources between trees and crops can reduce the productivity of the crop component. We want to share some of our results gained from in-depth analyses of time series (October 2019 to March 2020) and campaign (September 2019) data of soil moisture and matric potential in a South African AFS.

Soil water content was measured in a soil profile at two locations within an AFS plot: alongside a windbreak consisting of Italian Alders (Alnus cordata) and amongst the crop i.e. within blackberry rows. Matric potential time series are only available at the windbreak soil profile. Surficial soil samples taken along transects perpendicular to the windbreak were analysed for physical properties (e.g. texture, water retention curve).

Based on extracted water retention curves and matric potential time series, we found no evidence for plant water limitation during the measurement period (summer months) within the field site. Estimated root water uptake indicated that the trees take water from a greater range of depths, including deeper layers, than the blackberry plants. We observed divergent hydrological behaviour of the soil at the two locations during precipitation events, potentially resulting from dissimilar storage capacities and runoff formation potentials. Furthermore, the matric potential revealed hydrological information on plant water usage that was not as obvious from the soil moisture data.
Long waves in the Port of Klaipėda 
Authors: Nesteckytė Laura , Klepšaitė-Rimkienė Loreta , Myrberg Kai Antero
Published: March 2022

The entire strait is the base of the port aquatorium and a vital shipping artery from the Baltic Sea to the Curonian Lagoon as well as a complex water system connecting two water basins of different sizes and depths and nature: differing considerably in salinity and density. Although the quays are well protected from the waves of the open sea, dangerous water level fluctuations still occur in the port area, the origin of which is not yet well understood. This study aims to identify the occurrence and main characteristics of the long waves, with the period from minutes to several hours, to identify their origin and impact.

Analysis of the spectral composition of these oscillations is based on continuous pressure recordings at a frequency of 4 Hz in Klaipėda harbour during the stormy season 2016-2017 and repeated during calm and stormy seasons in 2021. Most of the oscillation energy is concentrated in two frequency bands. Significant water level changes occurred due to infragravity motions with periods of 30 s (0.03 Hz) and disturbances with the typical periods of wind waves on the Lithuanian coast with periods of 3-10 s (0.1-0.3 Hz). The highest peak in the wind wave frequency band corresponds to typical storm conditions in the Baltic Sea with periods of 5-9 s. While the typical amplitudes of the oscillations in this range were modest, hazardous changes in water level occurred at lower frequencies with amplitudes of 0.5 m. The record shows the presence of harbour oscillations with periods of 30-200 s (0.005-0.03 Hz) and seiches of the Curonian Lagoon with periods of 1200 s (0.0008 Hz).

The largest oscillations are created by a combination of wind waves and infragravity waves with periods that roughly match the natural seiche periods of Klaipėda Strait and harbour oscillations and seiches can be observed not only during the stormy season.
Absolute radiance calibration for UV-vis measurements of scattered sun light
Authors: Wagner Thomas , Beirle Steffen , Donner Sebastian , Dörner Steffen , Pukite Janis
Published: March 2022

Spectroscopic measurements of scattered sun light are widely used to retrieve atmospheric trace gas distributions. Usually, the used instruments are not radiometrically calibrated, because for the analysis of the narrow-band molecular absorptions no absolute calibration is needed.  For some applications, however, an absolute radiance calibration is needed, e.g. for the determination of aerosol and cloud properties or actinic fluxes.

The radiance calibration is usually performed in the laboratory using calibrated light sources. However, such calibrations have their own uncertainties. Moreover, during transport of the instruments from the laboratory to the field, often changes of the instrument properties occur.

Here we propose a new calibration method which can be directly applied in the field using measurements of zenith scattered sun light. We found that especially during sunset and sunrise, the scattered light intensity from the zenith is rather insensitive to the effect of atmospheric aerosol scattering. 

If e.g. the AOD is 0.3 or less, while the actual AOD is not known, the respective uncertainties of the radiance calibrations at an SZA of 90° are about 5% at 340nm, 8% at 380nm, or 12% at 440nm. For larger wavelengths, the uncertainties increase strongly. If, however, the AOD is known within about 0.1, the corresponding uncertainties are much smaller, ranging between about 2% at 340nm and about 12% at 700nm. These uncertainties also include the effects of the uncertainties of the surface albedo, aerosol optical properties, their vertical profiles as well as variations of the stratospheric ozone absorption, the stratospheric aerosols and the effect of Raman scattering. Thus, in combination with sun photometer measurements a radiometric calibration even at larger wavelengths is feasible. It should be noted that the RTM simulations have to be performed including polarisation.

We present sensitivity studies based on radiative transfer simulations, the application of the new method to real measurements and a comparison to independent measurements.