bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetotail Ion Structuring by Kinetic Ballooning-Interchange Instability
Authors: Panov Evgeny V. , Lu San , Pritchett Philip L.
Published: March 2022

By combining three-probe THEMIS observations and 3-D Particle-in-Cell simulations, we identify key structures on the ion gyroradius scale that occur in connection with ballooning-interchange instability (BICI) heads in the Earth’s magnetotail. The mesoscale structures occur at sites of strong ion velocity shear and vorticity where the thermal ion Larmor radius is about half of the width of the head. Finer structures occur at the smaller scales characterizing the wavelength of the electromagnetic ion cyclotron waves generated at the heads. These two processes act to erode and thin the current sheet, thereby forming a local magnetotail configuration that is favorable for reconnection.
Hydro cyclone flow as a physical process of ejection of material in the plumes of Enceladus and influence in the atmosphere.
Authors: Villavicencio Valero Katherine , Ramírez-Juidías Emilio , Allemand Pascal
Published: March 2022

On Enceladus, the first sign of water vapor plumes was detected by the UVIS instrument of Cassini during a stellar occultation in July 2005. The dynamics of these water plumes, probably related to the ocean activity, are an important subject of study in order to understand the exchange of material from this ocean into the atmosphere. There are different theories that might explain the physical processes that allow for the expulsion of material from the subsurface. The formation of these jets could be produced by the sublimation of ice (temperatures below 273 K) rising beneath the hydrostatic pressure along the ice layer or can come from underground boiling liquid that erupts through vents. Other hypothesis assumes that there are regions where the pressure can drop below the saturation vapor pressure of the liquid, allowing for it to boil, so it can produce a pocket of gas in equilibrium with ice grains and liquid water. Another possibility is that the thermal activity in the seafloor of Enceladus creates hot water outflows that locally affect the ice shell and the thinner icy crust in the polar region due to tidal stress. This work presents another possible model for the formation of these vapor plumes. The hydro cyclonic flow could be also a mechanism that produces a constant ejection of these jets and contributes to atmospheric processes. Here we describe a simulation of the dynamic of the energy budget into the atmosphere. Enceladus is tidally locked with Saturn, making the moon spinning around the planet always showing the same face, generating in this way a difference in temperatures between the internal side and the external one. This contrast of temperatures might produce a movement of violent flows of jets on the equator similar to the storms observed on Jupiter. If the tidal axis is not aligned with the major axis, the tidal forces exert a net momentum on the moon, forcing a realignment of the orbit. The result of these processes is a hydro cyclonic flux in the shape of a tornado that eventually generates, due to pressure differences, a straight upwards constant flow that separates the fine particles rising towards the surface from the heavy ones sinking towards the ocean. This hydro cyclonic type of flow might explain the constant jets from the tiger stripes on Enceladus that could decrease when the energy flux received from the sun drops due to the distance between Saturn and the Sun, and the atmospheric and physical conditions are stable.
Mechanical controls on methane bubble solute exchange within muddy aquatic sediments and its growth characteristics
Authors: Zhou Xiongjie , Katsman Regina
Published: March 2022

Methane (CH4) bubbles in muddy aquatic sediments threaten climate sustainability and sediment mechanical stability. Mechanical response of muddy sediment to bubble growth is described by Linear Elastic Fracture Mechanics (LEFM). Minor roles of mechanical sediment characteristics in CH4 bubble solute supply and growth rates were quantified compared to biogeochemical controls. We investigate them using a coupled single-bubble mechanical/reaction-transport numerical and analytical models. We demonstrate that inner pressure of the growing bubble at fracturing, concentration at its surface, bubble size and spatial location, are uniquely defined by Fracture Toughness. However, a temporal evolution of the bubble inner pressure at expansion between the fracturing events depends on Young’s modulus. Fracture Toughness and Young’s modulus thus play complementary, spatial and temporal, roles in bubble growth. Their proportionality suggested by LEFM manages the bubble growth rates.  Fracture Toughness controls development of longer flatter bubbles in the deeper sediments. A substantial role of mechanical muddy sediment characteristics in the CH4 bubble growth dynamics and solute exchange is demonstrated, comparable to the role of the biogeochemical controls. Their contribution to emergence of “no-growth” and competitive bubble growth conditions, affecting a macro-scale gas dynamics are discussed that encourages a proper experimental evaluation of muddy sediment mechanical characteristics.
Approximating downward short-wave radiation flux using all-sky optical imagery using machine learning trained on DASIO dataset.
Authors: Koshkina Vasilisa , Krinitskiy Mikhail , Anikin Nikita , Borisov Mikhail , Stepanova Natalia , Osadchiev Alexander
Published: March 2022

Solar radiation is the main source of energy on Earth. Cloud cover is the main physical factor limiting the downward short-wave radiation flux. In modern models of climate and weather forecasts, physical models describing the passage of radiation through clouds may be used. This is a computationally extremely expensive option for estimating downward radiation fluxes. Instead, one may use parameterizations which are simplified schemes for approximating environmental variables. The purpose of this work is to improve the accuracy of the existing parametrizations of downward shortwave radiation fluxes. We solve the problem using various machine learning (ML) models for approximating downward shortwave radiation flux using all-sky optical imagery. We assume that an all-sky photo contains complete information about the downward shortwave radiation. We examine several types of ML models that we trained on dataset of all-sky imagery accompanied by short-wave radiation flux measurements. The Dataset of All-Sky Imagery over the Ocean (DASIO) is collected in Indian, Atlantic and Arctic oceans during several oceanic expeditions from 2014 till 2021. The quality of the best classic ML model is better compared to existing parameterizations known from literature. We will show the results of our study regarding classic ML models as well as the results of an end-to-end ML approach involving convolutional neural networks. Our results allow us to assume one may acquire downward shortwave radiation fluxes directly from all-sky imagery. We will also cover some downsides and limitations of the presented approach.
Insights on carbonate diagenesis in methanogenic zones from full-speciation reaction-transport modelling
Authors: Meister Patrick , Herda Gerhard , Petrishcheva Elena , Gier Susanne , Dickens Gerald R. , Bauer Christian , Liu Bo
Published: March 2022

Diagenetic carbonates in marine sediments contribute to the global burial of carbonates (Schrag et al., 2013; Sun & Turchyn, 2014). The carbonates often form in zones of enhanced anaerobic microbial activity, where the consumption and release of metabolites leads to supersaturation of the porewater with respect to carbonate minerals.

Some diagenetic carbonates occur in zones of methanogenesis, where methane concentrations can be very high and reach gas hydrate stability. So far, it has not been clarified how carbonate formation is induced in methanogenic zones. The production of methane by both fermentation of acetate and reduction of carbonate by H2 is stoichiometrically linked to release of excess CO2 and, therefore, should lower carbonate supersaturation in the porewater.

Nevertheless, porewater extracted from drill-cores across methanogenic zones, as at ODP Site 1230 in the Peru-Chile Trench, shows very high total alkalinity of 150 mmol/l, buffering the acidification imposed by the CO2. Based on full-speciation reaction-transport modelling (Meister et al., 2022), it is possible to reproduce alkalinity production as a result of the combined effects of dissimilatory release of ammonia and dissolution/alteration of clay minerals under high pCO2 conditions. Hence, acidification of the fluid is buffered by mineral reactions. In this way, silicate alteration in marine sediments may represent a significant CO2 buffer that contributes to the formation and burial of diagenetic carbonates.

Schrag, D.P., Higgins, J.A., Macdonald, F.A., Johnston, D.T. (2013) Authigenic carbonate and the history of the global carbon cycle. Science 339, 540–3.

Sun, X., Turchyn A.V. (2014) Significant contribution of authigenic carbonate to marine carbon burial. Nature Geoscience 7, 201.

Meister, P., Herda, G., Petrishcheva, E., Gier, S., Dickens, G.R., Bauer, C., Liu, B. (2022) Microbial alkalinity production and silicate alteration in methane charged marine sediments: implications for porewater chemistry and diagenetic carbonate formation. Frontiers in Earth Science 9, 756591, 1-18. https://doi.org/10.3389/feart.2021.756591
SO2, SO3, OCS, H2S, and other trace gases in the Venus mesosphere from SOIR on board Venus Express: Detection and upper limit profiles
Authors: Mahieux Arnaud , Robert Séverine , Mills Frank , Trompet Loïc , Aoki Shohei , Piccialli Arianna , Jessup Kandis Lea , Vandaele Ann Carine
Published: March 2022

We report the detection of SO2, SO3, H2S, and OCS above the cloud deck using the SOIR instrument on-board Venus Express, and upper limit profiles of HOCl, CS, and CS2.

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 µm) at a resolution of 0.12 cm-1, the highest of all instruments on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. SOIR performed more than 1500 solar occultation measurements leading to about two millions spectra.

The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere at the terminator in the mesosphere, with an emphasis on vertical distribution of the gases.

In this work, we report detections in the mesosphere, between 60 and 100 km.

Implications for the mesospheric chemistry will also be addressed.
Ventilation and oxygen export in the Labrador Sea
Authors: Koelling Jannes , Atamanchuk Dariia , Karstensen Johannes , Handmann Patricia , Wallace Douglas W.R.
Published: March 2022

The Labrador Sea is one of the few regions where ventilation can replenish oxygen to the deep ocean, owing to wintertime deep convection that occurs primarily in the center of the basin. While some recent studies have aided in quantifying the amount of oxygen taken up during Labrador Sea Water (LSW) formation, less is known about how different spreading pathways of LSW contribute to the export of oxygen.

In this study, we use oxygen data from the 53N mooring array in the boundary current at the exit of the Labrador Sea, together with Argo float data, in order to investigate the connection between deep convection, spreading of LSW, and oxygen export. We find that the annual cycle of the oxygen concentration is driven largely by an increased input of newly formed LSW into the boundary current in the spring and summer. The resulting oxygen increase is a result of a fast, direct southward pathway of LSW, and we estimate that the associated oxygen export accounts for about half of the uptake in the interior. The 4-year record that is presently available also indicates that the strength of the oxygen export varies interannually, which may be related to changing convection patterns.

Overall, our results highlight the important role that the Labrador Sea plays in supplying oxygen to the deep ocean, and represent a first step towards better understanding the ventilation pathways out of this critical region.
Earthquake catalogue enhancement through template matching: an application to the Southern Apennines (Italy)
Authors: Diaferia Giovanni , Valoroso Luisa , Piccinini Davide , Improta Luigi
Published: March 2022

Improving the capability of seismic networks to detect small-magnitude seismicity, commonly near or below the detectability threshold, is the prerequisite to characterize the seismotectonics of an area in terms of fault geometry, kinematics and mechanics, thus leading to an improved comprehension on the physical mechanisms that generate small and large earthquakes. In this work, we apply template-matching, a cross-correlation based technique for the detection of hidden earthquakes, at the scale of the Southern Apennines (Italy). Here, the ongoing extension of the Mio-Pliocene Apennine thrust-belt poses a major seismic risk, as testified by several Mw~7 earthquakes that struck this area in the past 300 years. No clear consensus exists on the seismotectonic models related to such events, particularly in terms of characterization of the fault structure and crustal rheology that can thus largely benefit from the application of template-matching.

As template events, we use ~9000 earthquakes occurring between 2009 and 2015, recorded by 181 stations from the INGV National Seismic Network. Six years-long (2009-2015) continuous recordings are scanned by the template-matching algorithm. Of about 3 million new detections, around 3% (~88.000 events) comply with the minimum quality thresholds we set (at least four P and S picks, recorded at least at five stations). For determining earthquake locations we used the fully-probabilistic non-linear code NonLinLoc, with an ad-hoc 1D velocity model and corrections for station residuals.

By accounting for the quality of the hypocenter location, the final catalog comprises ~50.000 new seismic events with a mean horizontal and vertical error of 1.4 and 2.5 km, respectively, and a mean RMS of 0.13 s, parameters that are similar to those of the template catalog. Given the small magnitude (Mw<1) of the majority of the newly detected events, the new catalog shows a decrease in magnitude of completeness from 2.5 to 1.9, assessed through the Lilliefors’ goodness-of-fit test.

The spatial and temporal pattern of seismicity unravelled by the enhanced catalog provide new insights especially for those seismogenic structures that are poorly known. For the main seismic sequences that occurred in the analyzed period (i.e., Pollino and Matese Mw5+ sequences) the aftershocks as well as the foreshock phases appear particularly enriched. Main NW-SE trending seismogenic structures of the axial zone of chain are illuminated by abundant microseismicity, with evident gaps delineating the boundary of such structures. In addition, the new catalog unravels distinct E-W oriented clusters in the external zone of the seismic belt, likely related to shear zones developed in the deeper crystalline crust of the Adria plate.
Dayside to nightside dust column density ratios in the inner comae of comets
Authors: Thomas Nicolas , Marschall Raphael , Gerig Selina-Barbara , Pinzon-Rodriguez Olga
Published: March 2022

It was recognized in observations of the innermost coma of comet 1P/Halley by the Halley Multicolour Camera onboard Giotto, that the dayside dust coma was, on average, only around a factor 3.2 brighter than the dust coma on the nightside. This was considered surprising because the phase angle of the approach (107.2°) was not substantially different from a terminator viewing direction. The dominance of water sublimation in comets and the assumption that nightside activity should be strongly limited led to the conclusion that lateral (non-radial) flow of dust from the dayside to the nightside must be responsible. This was apparently supported qualitatively by evidence of dust gradients seen against the background of the shadowed nucleus (Keller and Thomas, 1989).

Using observations from the MICAS camera on Deep Space 1, Ho et al. (2003) found for 19P/Borrelly a dayside to nightside coma brightness ratio (DS:NS) of just 1.7 at a phase angle of 88° and rh= 1.36 AU and subsequently compared this to the results from 1P/Halley (Ho et al., 2007). The brightness ratio was even smaller despite the observation being from almost directly above the terminator. This observation has not been widely promoted, possibly in part because of the quite poor imaging quality of MICAS.

Lateral flow is not the only means of producing low values of DS:NS. Both slow moving particles in orbit about the nucleus and nightside outgassing can influence the observed column density ratio. Gerig et al. (2020) have investigated the observational data at 67P/Churyumov-Gerasimenko and have established both the low DS:NS ratio (as at the other comets) and an increasing DS:NS ratio with reducing heliocentric distance. Furthermore, the brightness distribution with distance in the innermost coma most closely fits radial outflow suggesting that gravitationally bound particles are not the dominant influence on DS:NS. Pinzon-Rodriguez et al. (2021) have modelled H2O and CO2 emissions from 67P in a simplified, coupled, thermal system and shown that for reasonable parameters, nightside emission of dust driven by CO2 is a promising explanation for the observations.

The presentation will provide the observational evidence for the DS:NS ratio, describe the modelling work, and demonstrate the results.

 

Gerig, S.-B., et al., (2020) , Icarus, 351, 113968.

Ho, T.M., et al., (2003), Advances in Space Research, 31, 2583.

Ho, T.-M., et al. (2007), Planetary and Space Science, 55, 974-985.

Keller, H.U. and N. Thomas, (1989), Astronomy and Astrophysics, 226, L9.

Pinzón-Rodríguez, O., et al., (2021), Astronomy and Astrophysics, 655, A20.
Sensor and performance modelling of an optical accelerometer for future gravity field missions
Authors: Kupriyanov Alexey , Reis Arthur , Schilling Manuel , Müller Vitali , Müller Jürgen
Published: March 2022

Electrostatic accelerometers (EA) are one of the limiting factors of space gravimetry missions dominating the error contribution at low frequencies (<10−3Hz). The focus of this study is on the modelling of an optical accelerometer that can improve gravity field retrieval to unprecedented accuracy. Contrary to GRACE(-FO) or GOCE accelerometers, optical accelerometers sense the motion of the test mass (TM) in one or more axes by applying laser interferometry. Combination of sensing in multiple directions and of several test masses would lead to enhanced gradiometry which would improve the determination of the static gravity field to a higher spatial resolution. Modelling of the above-mentioned accelerometer blocks in Matlab Simulink allows to simulate various TM measurement scenarios for satellite missions under different conditions, e.g. dedicated satellite configurations, various non-gravitational forces, etc. This research is based on very promising results of the mission LISA-Pathfinder (LPF) which has demonstrated the benefit of a drag-free system in combination with optical accelerometry that allowed sensing of non-gravitational accelerations several orders of magnitude more accurate than those of current gravity missions like GRACE-FO. This research project is carried out in close collaboration with the IGP and the DLR-SI, to provide - on the long run - a roadmap for improved angular and linear accelerometry for the next generation of gravity field missions.

In this presentation, we now introduce a functional model of 6 degrees-of-freedom (DoF) optical accelerometer and compare its output with the measurements of electrostatic accelerometers for the dual satellite configuration, i.e. GRACE-FO mission. Also, the current state of the Simulink implementation of the accelerometer model which are mainly developed by IGP are presented. Finally, the simulated gravity gradients from the novel gradiometer based on the optical accelerometers are demonstrated as well as benefits that can be acquired from this sensor.

This project is funded by: Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464.
Modelling pathways for development of a new forest industry in Mozambique
Authors: Ofoegbu Chidiebere
Published: March 2022

Forest-based initiatives are receiving greater attention in global and national strategies on change and bio-economy. It is therefore vital to identify multi-win activities and strategies for the tropical forest industries within the context of global and national climate and bio-economy policy. The “Good Wood” value chain could be one of these solutions—restoring natural tropical forests, mitigating climate change, and improving livelihoods. The “Good Wood” value chain adopts an integrated timber processing business concept to tropical timber utilization. This concept contrasts conventional forestry practices—, which rely on logging large trees of a few species from relatively pristine natural forests—in that it is adapted to degraded natural forests with small and damaged trees of many species. It also includes a number of value-adding steps—such as drying and further finishing—to enable access to regional and export markets. Linking manufacturers directly with customers allows for product development and customized timber products, which maximizes both wood recovery and profit. Drying onsite dramatically improves quality and access to high-value markets reduces waste (e.g., warped, rotten, and low-quality timber), and allows for greater use in long-lived wood products (e.g., construction materials).

The overarching purpose of the study is to assess the extent to which the “Good Wood” timber processing business concept contributes to climate change mitigation, forest restoration, and sustainable development. We discuss emerging results from our empirical study in Mozambique. The main goal of the study is to contribute to the development of new forest management systems in accordance with the Good Wood timber processing business concept—integrated with a sawmill and market—to restore degraded forests and provide timber.

The intent is that findings will be used to support and promote the Good Wood concept to governments as a strategy for meeting sustainable development and Nationally Determined Contributions to the UN climate agreement and Forest Landscape Restoration commitments, and business entrepreneurs.
Pan-European coastal vulnerability: translating incomplete data and information for communicating situational awareness
Authors: Moses Cherith , Butterill Cerys , Chopra Tanvi , Humphries Amber , van Heteren Sytze
Published: March 2022

The identification and communication of potential risks faced by coastal-zone populations is becoming increasingly important to strengthen society’s resilience and enabling people to better handle coastal hazards. Assessing risk and vulnerability is important to inform the public, as well as coastal managers, on sustainable policy and practice. This so-called coastal vulnerability has been assessed, quantified and mapped using a wide variety of approaches, focussing on hazard, risk and resilience. Many studies place emphasis on physical parameters such as geology and topography, and on marine factors such as wave energy and storm frequency. Others also incorporate socio-economic factors such as population, cultural heritage, presence of crucial infrastructure, land use and conservation status.

Our pan-European assessment of coastal vulnerability adds a new layer of information to the existing EMODnet Geology product suite on shoreline change. EMODnet Geology benefits the public sector, civil society, the private sector and the research community through harmonising and integrating existing and new datasets for dissemination via the EMODnet portal. Using the most complete inventory to date of case studies on coastal vulnerability in scientific journals, books and governmental reports, we have developed a detailed database on various vulnerability aspects across Europe and in other countries around the world. By geo-locating the maps from these studies, we are able to assess the extent of coverage of coastal vulnerability assessment around European shorelines. Drawing on the existing literature, we are developing a common legend, indicating low, medium and high levels of vulnerability that can be mapped at a pan-European scale.

Our research indicates incomplete coverage by existing studies. Using data from existing EMODnet products such as shoreline migration, geology and bathymetry, we will develop a basic coastal vulnerability index that can be validated against existing studies and used to fill the gaps. The resulting applied data product will help raise awareness in the general public and facilitate the work of coastal policy makers, planners and practitioners.
Climate-driven rapid mass loss in West Antarctica revealed by Swarm gravimetry in the absence of GRACE
Authors: Zhang Chaoyang , Shum Che-Kwan , Bezděk Aleš , Bevis Michael , Teixeira da Encarnação João , Tapley Byron , Zhang Yu , Su Xiaoli , Shen Qiang
Published: March 2022

GRACE observations revealed that rapid mass loss in the West Antarctic Ice Sheet (WAIS) abruptly paused in 2015, followed by a much lower rate of mass loss ( 21.3±5.7 Gt‧yr-1) until the decommissioning of GRACE in 2017. The critical 1-year GRACE inter-mission data gap raises the question of whether the reduced mass loss rate persists. The Swarm gravimetry data, which have a lower resolution, show good agreement with GRACE/GRACE-FO observations during the overlapping period, i.e. high correlation (0.78) and consistent trend estimates. Swarm data efficiently bridge the GRACE/GRACE-FO data gap and reveal that WAIS has returned to the rapid mass loss state (  161.5±48.4  Gt‧yr-1) that prevailed prior to 2015 during the GRACE inter-mission data gap. The changes in precipitation patterns, driven by the climate cycles, further explain and confirm the dramatic shifts in the WAIS mass loss regime implied by the Swarm observations.
Topographic and photogrametric techniques applied to the study of the morphology of ravines in Campana city, Buenos Aires, Argentina
Authors: Serraiocco Leandro , Barbero Diego , Santomauro Melina , Peyrot Sandra , Maroni Andrea
Published: March 2022

Abstract

The comprehensive study of the stability of ravines includes various aspects to be considered. One of them, interesting in this case, is the characterization of the morphology of the slopes, which due to their high inclination, presence of vegetation and irregularity in the surface, making it difficult to achieve this objective.

In the present study, we proceeded to study a ravine, located on the right bank of the Paraná de las Palmas river, in the town of Campana, northeast of the province of Buenos Aires. This work was focused on the surroundings of the coordinates 39º9'30.40 ”S 58º57'14.60” where lays a slope with structural conditions of interest. The morphology of the ravine in this area was studied in order to obtain a more precise assessment of the exposed surface and therefore a correct geometric and mass estimation of the slope.

For this propuse, an analysis of elevation models obtained from topographic surveys carried out with Drone and Total Station and, georeferenced with GPS equipment along the slope, was carried out. From there, the reliability of the applied methods and the results obtained could be evaluated comparatively.

All this information was complemented with a photographic record and available information on the environment to achieve a complete evaluation of the condition of the ravine in this area.

The importance of this work lies in the possibility of testing different methods and contrasting the results obtained using topographic and photogrammetric equipment and a combination of them. This will allow the characterization of slopes to be scaled over larger portions considering that this is part of a larger study along the Paraná river ravine. The greater reliability in the morphological results obtained is considered to be of significant utility for estimating the stability of the slopes, an aspect of interest to evaluate the geological danger and evaluate different engineering solutions.

Key Words: Ravine, Slope, Río Paraná, Argentina, Geological Risk, Drone.

           
Deflection of CMEs in Different Background Magnetic Fields 
Authors: Torok Tibor , Ben-Nun Michal , Downs Cooper , Titov Viacheslav S. , Caplan Ronald M. , Lionello Roberto
Published: March 2022

As suggested by Isenberg and Forbes (2007) and demonstrated numerically by Kliem et al. (2012), the Lorentz forces stemming from the interaction of the axial current in an erupting magnetic flux rope (MFR) with an ambient magnetic-field component that has the same orientation as the initial MFR axis leads to a rotation of the top part of the MFR about its rise direction. In principle, the same mechanism can be applied to CMEs that propagate in a unipolar radial field in the corona or inner heliosphere. In such cases, however, the corresponding forces should not lead to a rotation, but to a deflection of the CME front, thereby significantly altering the CME's magnetic orientation. Apart from a brief consideration in Lugaz et al. (2011), such deflections have, to the best of our knowledge, not yet been studied systematically. 

Here we employ three-dimensional (3D) idealized magnetohydrodynamic (MHD) simulations to investigate this effect in background fields of increasing complexity. We first consider a freely expanding toroidal MFR in a uniform background field, as well as the propagation of a compact, line-tied MFR in a unipolar radial field. In both cases, we find significant deflections. We then use a more realistic setup, in which we erupt an MFR from a localized, bipolar source region into a global dipole field and solar wind, which allows for a significant expansion of the MFR before it encounters open field. We perform a parametric study in which we vary the location and magnetic orientation of the source region, as well as the handedness (helicity sign) of the MFR. In this presentation, we discuss the influence of these parameters on the CME trajectory.
Assessing crustal stability via fault stress perturbation analysis
Authors: Zaccagnino Davide , Telesca Luciano , Doglioni Carlo
Published: March 2022

Assessing the stability state of faults is a crucial issue not only for seismic hazard, but also for understanding how the earthquake machine works. A possible approach consists in perturbing fault systems and studying how seismicity changes after additional stress is provided: if the starting energy state is stable, it will oscillate around it; otherwise, the background seismic rate will be modified. Tides provide natural stress sources featured by a wide range of frequencies and amplitudes, which make them a suitable candidate for our needs.  Analyses prove that the brittle crust becomes more and more sensible to stress modulations as the critical breaking point comes close.  Especially, the correlation between the variation of Coulomb failure stress induced by tidal loading, ΔCFS, and seismic energy rate progressively increases as long as seismic stability is kept; conversely, abrupt drops are observed as foreshocks and preslip occur. A preparatory phase, featured by increasing correlation, is usually detected before large and intermediate (Mw > 5) shallow (depth < 50 km) earthquakes. The duration of the anomaly, T, is suggested to be related to the seismic moment M of the impending mainshock by T ∝ M^(1/3) for M < 10^19  N m. The same power exponent characterizes seismic nucleation scaling of single earthquakes. This analogy may be explained assuming that the physical mechanism behind both these phenomena is the same. Consequently, the anomalies we measure might be interpreted as diffuse nucleation phases throughout the crust. The scaling relation becomes T ∝ M^0.1 for M > 10^19 N m, probably because of preparation processes occurring contemporaneously in interacting faults.  We apply this method to dozens of seismic sequences which hit California, Greece, Iceland, Italy and New Zealand, we also analysed seismic activity jointly with slow slip events in the Cascadia subduction zone, Manawatu region and in the Nankai Trough. Even though it is unlikely that our results may ever be of practical use for seismic hazard, the procedure could illuminate slow hidden processes of destabilization taking place within the brittle crust.                                                             
Space-time variations of crustal, fault zone, and seismicity structures
Authors: Ben-Zion Yehuda
Published: March 2022

Beno Gutenberg made fundamental contributions to knowledge about large-scale earth structures and properties of moderate to large earthquakes using the seismic data available at the time. Data recorded in the last few decades by improved regional networks and dense seismic arrays provide opportunities for resolving fine details of subsurface rocks and seismicity in 4D. I review such results based primarily on recent data from Southern California. The discussed topics include multi-scale seismic imaging of the crust and fault zones, monitoring temporal changes of seismic velocities, and tracking localization of rock damage and low magnitude seismicity before large earthquakes.

The seismic imaging results reveal hierarchical rock damage structures around large fault zones with intense core damage zones and bimaterial interfaces. The fault damage zones follow overall a flower-shape structure, with significant damage in the top few km that decreases in amplitude and width with depth, and they tend to be offset from the surface trace to the side with higher seismic velocity at depth. The top 100-300 m section has generally extreme seismic properties (very low Vp, Vs, Q values; very high Vp/Vs ratios), which make it highly susceptible to failure and temporal changes. Large earthquakes produce changes of seismic velocities that decay with distance from the rupture zones, but remain significant on a regional scale in the shallow crust. The co-seismic velocity changes are followed by log(t) recovery, and can be very large (e.g. >30%) in the top 100-300 m. Appreciable changes of shallow materials are also generated by atmospheric and other non-tectonic loadings on various timescales.

The results on localization processes are based on (i) estimated production of rock damage by background seismicity, (ii) spatial localization of background events within damaged areas, and (iii) progressive coalescence of individual earthquakes into clusters. The analyses reveal generation of earthquake-induced rock damage on a decadal timescale around eventual rupture zones of large earthquakes, and progressive localization of background seismicity 2-3 yrs before M > 7 earthquakes in Southern and Baja California and M > 7.5 events in Alaska. This localization phase is followed by coalescence of earthquakes into growing clusters that precede the mainshocks. Corresponding analyses around the 2004 M6 Parkfield earthquake in the creeping section of the San Andreas fault, which is essentially always localized, show opposite tendencies to those involving faults that are locked in the interseismic periods.

Continuing efforts in these topics include merging local high-resolution imaging results within regional models, monitoring temporal changes of properties at seismogenic depth, and including geodetic data and insights from laboratory experiments in the localization analyses.
THE END OF THE MESSINIAN SALINITY CRISIS IN THE MEDITERRANEAN: new data on the Miocene-Pliocene boundary.
Authors: Pilade Francesco , Dela Pierre Francesco , Natalicchio Marcello , Vasiliev Iuliana , Birgel Daniel , Mancini Alan , Lozar Francesca , Gennari Rocco
Published: March 2022

The Miocene-Pliocene transition (MPT) in the Mediterranean area represents one of the unresolved geological riddles of the Neogene. The MPT coincides with the end of the Messinian salinity crisis (MSC, Hsü et al., 1977), an event that led to the deposition of massive volume of evaporite on the Mediterranean seafloor. The final stage of the MSC started at ~5.53 Ma and its uppermost part corresponds to the “Lago-Mare” phase, characterized by the occurrence of brackish shallow water ostracods of Parathethyan origin. The “Lago-Mare” deposits are sharply overlain by Zanclean (earliest Pliocene) marine sediments, astrocronologically dated to start at 5.33 Ma (Van Couvering et al. 2000).

The interpretation of this abrupt environmental change is strongly debated. One scenario assumes a catastrophic flooding of all Mediterranean sub-basins that were previously disconnected from the Atlantic Ocean and from each other (Caruso et al., 2020). An alternative scenario invokes a gradual refilling started during the Lago-Mare phase and continued during the basal Pliocene (early Zanclean) (Roveri et al., 2008; Stoica et al., 2016; Merzeraud et al., 2018).

To investigate the paleoenvironmental conditions across the MP transition, we investigated six sections along a west to east transect of the Apennines foredeep, using an integrated approach that merge the traditional stratigraphic, palaeontological, geochemical, and petrographic data with the analysis of molecular fossils (lipid biomarkers).

The top of the Messinian sediments is marked by a bioturbated dark layer in all six studied sections. The presence of glauconite at the top of the dark layer and of firm ground burrows of the Glossifungites icnofacies filled with Zanclean sediments suggest starved sedimentary conditions and the partial lithification of the sea floor during the earliest Zanclean. In addition, the benthic foraminifera indicate an increase of bottom oxygen content and a deepening of the basin across the MPT. Preliminary results of over 40 samples indicate excellently preserved molecular fossils both in the “Lago-Mare” sediments and in the Zanclean open marine deposits with a predominance of terrestrially-derived higher-plants long chain n-alkanes (LCalk) and of glycerol dialkyl glycerol tetraethers (GDGTs) of both marine and terrestrial origin. Future analyses will focus on the compound specific carbon and hydrogen isotopes of LCalk to further constrain precipitation and vegetation changes associated to the MPT. Changes in seawater (via isoprenoidal GDGTs) and land temperatures (via branched GDGTs) will be also reconstructed.
Simulating the surface mass balance at the Monte Sarmiento Massif, Cordillera Darwin, Chile
Authors: Temme Franziska , Farías-Barahona David , Seehaus Thorsten , Sauter Tobias , Jaña Ricardo , Arigony-Neto Jorge , Gonzalez Inti , Schneider Christoph , Fürst Johannes
Published: March 2022

Together with the Northern and the Southern Patagonian Icefield, the Cordillera Darwin Icefield (CDI) in Tierra del Fuego experienced strong ice loss during the last decades. In some areas the observed glacier retreat contrasts with findings of recent surface mass balance studies, which implies that the observed losses are partly caused by dynamic adjustments. However, the difficult accessibility of Patagonian glaciers and the harsh conditions result in scarce observational data of glacier mass balances, especially for the CDI. In the westernmost region of the CDI, Monte Sarmiento is located. It hosts an 83 km2 icefield, with Schiaparelli Glacier being the largest glacier, terminating in a proglacial lake.

We focus on reproducing the local meteorological conditions using statistical downscaling of atmospheric reanalysis data to the study site as well as a linear model of orographic precipitation. Subsequently, we concentrate on a best representation of the surface mass balance (SMB) conditions on the local glaciers. For this purpose, we apply four melt models of different complexity: i) a positive degree-day model, ii) a simplified energy balance model using potential insolation, iii) a simplified energy balance model using the actual insolation (accounting for cloud cover, shading effects and diffuse radiation) and iv) a fully-fledged surface energy balance model. For the latter, we rely on the “COupled Snowpack and Ice surface energy and mass balance model in PYthon” (COSIPY). These models are calibrated on Schiaparelli Glacier (24.3 km2), which is the largest and best-studied glacier of the Monte Sarmiento Massif. Observational records comprise in-situ stake, thickness and meteorological measurements as well as remotely sensed elevation changes and flow velocities. After the melt model calibration, we apply them to other adjacent glacier basins and assess their performances against geodetic mass changes. This way, we want to answer the question if it is feasible to apply SMB models, calibrated for one single glacier, to surrounding glaciated areas under these unique climatic conditions. If a single-site calibration showed poor transferability properties, further remotely sensed observables will be considered in the calibration. This way we also hope to answer the question, which melt model can best reproduce the spatial variability in remotely sensed specific mass balances over a larger region.
Sea level and the Bering Strait gateway as determinant parameters in the ocean dynamics as illustrated from pan-Arctic Holocene records
Authors: de Vernal Anne , Hillaire-Marcel Claude , Song Tengfei , Liu Yanguang , Falardeau Jade
Published: March 2022

The shallow (~ 50 m deep) Bering Strait, which is the unique gateway linking the Pacific Ocean to the Arctic Ocean, deserves special attention as sea-level changes modify considerably the exchanges between the two oceans. Under high sea level, poleward heat transfer and freshwater fluxes from the Pacific impact the Arctic freshwater budget and sea ice distribution. Furthermore, sea level determines the status of the Arctic shelves, submerged or not, which plays a role in sea-ice production, as well as in the latent heat from Atlantic waters flowing northward through Fram Strait and the Barents Sea. Hence, high sea levels result in the connection of the Arctic basin with the Pacific, which modifies the Arctic freshwater and heat budgets and leads to the submergence of shelves, thus the potential development of sea-ice factories. The impacts of sea-level on the Arctic Ocean and subarctic seas are not easily reconstructed from sedimentary records, but radiocarbon-based chronologies and proxy-data covering the present interglacial provide useful information. For example, micropaleontological and geochemical records from the Chukchi Sea show progressive warming in surface water accompanying the increase of Pacific flux during the Holocene, until sea-level reached its present-day limit at ~ 4 ka BP. This contrasts with a trend towards perennial sea-ice cover in the southeastern Arctic and with changes at the eastern gateway of the Fram Strait, where cooling is recorded from early to late Holocene. Hence, we hypothesize that increased freshwater inflow from the Pacific into the Arctic together with enhanced sea-ice formation rates, both linked to sea-level rise, may have played a role in the general cooling trend culminating during the late Holocene.
Precipitation trends in Southern South America in the last centuries: attribution and mechanisms
Authors: Diaz Leandro Baltasar , Vera Carolina Susana
Published: March 2022

Southern South America (SSA) is one of the regions of the world where the largest trends in precipitation have been recorded during the last 120 years. While South-Eastern South America (SESA) has been affected by a noticeable increase in austral summer rainfall, a remarkable decrease has been observed in Southern Andes (SAn). Moreover, long-term precipitacion has been registered in subtropical Andes and Altiplano regions, which show wetter periods during the 17th century in the Little Ice Age (LIA) and dryer periods during the current Global Warming Period (GWP). In spite of the large impacts related to these trends, the attribution of them is still an open-question. 

This work will assess the attribution of the observed austral summer rainfall trends in SSA to anthropogenic and natural forcings using models available in World Climate Research Programme (WCRP) Coupled Model Intercomparison Project - Phase 5 (CMIP5) and Phase 6 (CMIP6). Analysed experiments include Historical, Pre-Industrial Control and Last Millennium simulations to study long-term changes, as well as the Detection and Attribution Model Intercomparison Project (DAMIP) to assess the attribution of last-century trends. 

The assessment of the Last Millennium simulations allows to detect the following changes in LIA (GWP): (a) equatorwards (polewards) displacement of the southern branch of the Hadley cell, in turn associated with wetter (drier) conditions in subtropical south America; (b) negative (positive) upper-level zonal wind changes related with positive (negative) December, January and February (DJF) rainfall changes in the Altiplano; and (c) positive (negative) low-level zonal wind changes associated to positive (negative) JJA rainfall changes in the subtropical Andes, being in turn related to hemispheric wind changes resembling a negative (positive) phase of the Southern Annular Mode (SAM). The last century changes in the Altiplano reveal a signal associated with the anthropogenic forcing in upper-level zonal wind trends, but it is weak as compared with the internal climate variability. 

Regarding last century trends, positive (negative) rainfall trends in SESA (SAn) are identified in most historical simulations. For both regions, greenhouse-gases-forcing-only simulations show trends consistent with all-forcing simulations, while natural-forcing-only simulations exhibit negligible values. SESA (SAn) shows negative (negligible) trends associated with aerosol-forcing-only simulations and high uncertainty (negative trends) for stratospheric-ozone-forcing-only simulations. Moreover, SAn rainfall trends could be also connected to consistent trends of opposite sign for the Southern Annular Mode (SAM). Overall, our results provide evidence for anthropogenic influences on SSA rainfall trends.