ALBERT

Description: In 2021, more than 50 paroxysmal episodes occurred at the South-East Crater (SEC) of Mt Etna, Italy. The 23–24 March lava fountain was one of the longest episodes and began with weak Strombolian explosions, gradually transitioning to lava fountaining. The eruption intensity then dropped more slowly than in previous episodes, resulting in pulsating Strombolian explosions dominated by ash emission. Thirty-four tephra samples were used to reconstruct the fallout dispersal and estimate the total erupted mass. Grain size, textural, petrological and geochemical analyses indicate different features and were compared with the gas phase ( SO2 and HCl) in the volcanic plume. By applying stochastic global optimization to simulations of the temporal evolution of the eruption column height and tephra dispersal and deposition, the total erupted mass retrieved (6.76 × 108 kg) matches well the total erupted mass estimation by the ground-based deposit (8.03 ± 2.38 × 108 kg), reducing the column height throughout the episode from 6.44 to 4.5 km above sea level and resulting in a mass eruption rate ranging from 1.96 × 105 to 8.18 × 103 kg/s. The unusual duration of the March episode and the characteristics of the erupted products point to the change in explosive style and magma fragmentation from fountaining to ash emission phases, associated with a slower magma supply inducing a change in magma rheology and a final, prolonged ash generation. Furthermore, this study showed that using observational data and the variation in eruption source parameters for numerical simulations can improve the accuracy of predicting the dispersal plume, thus mitigating the potential impact of longer paroxysmal episodes.

Description: Published

Description: 56

Description: OSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilità

Description: JCR Journal

Description: The Azores archipelago, situated east of the Mid-Atlantic Ridge, comprises volcanic islands arranged along sub-parallel spreading systems and rests on a thick oceanic crust. Magma is supplied directly from the roots of the volcanic systems. Located at or nearby the boundary between the crust and the mantle, they consist of mafic cumulates and mafic mush layers. This work focuses on tephra samples and a submarine lava younger than 40.000 years, collected from both central volcanoes and fissure zones. Our report details a new dataset of major, trace, and volatile elements analysed in glassy melt inclusions trapped in olivine (Fo75.8–85.6) which are extracted from cumulative bodies at the vicinity of the crust-mantle boundary. Their compositions cover a range from subalkaline to mildly alkaline basalt, and trachybasalt, which match those of Azores lavas. They registered a chemical evolution through fractional crystallisation of olivine alone, as well as olivine and clinopyroxene, as both the FeOt/MgO (1.4–3.1) and CaO/Al2O3 (0.4–1.0) ratios of the melt decrease. Incompatible element ratios of Zr (40–352 ppm), Ba (135–612 ppm), and Rb (5–77 ppm), as compared to Nb (5–82 ppm), exhibit variability within a limited but significant range of values. The ranges in the Nb/Zr, Ba/Nb and Rb/Nb ratios recorded by melt inclusions possibly reveal distinct geochemical sources (at least two), and mixing between partial melts as they move upward. The halogen signature is characteristic of the shallow mantle. The majority of melt inclusions show Cl/K ratio (0.06) similar to E-MORB, although some of them are comparable to N-MORB (Cl/K = 0.03). Their F/Nd ratio may achieve a rather high value (27.8).

Description: Published

Description: 64

Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici

Description: JCR Journal

Description: Over the last 25 years, Canadian scientists have studied the permafrost environmental archives in the Klondike Goldfields south of Dawson City (e.g. Fraser and Burn, 1997; Kotler and Burn, 2010; Froese et al., 2009; Porter et al., 2016; Monteath et al., 2023). In 2023, a small Canadian-German team visiting this area to sample mining exposures in the Klondike area (Figure 1A). The goal was to conduct studies on ground ice (ice wedges and pore ice) and frozen sediments to reconstruct past landscape and climate conditions. Detailed profiles were sampled at three sites at Little Blanche Creek, Whitman Gulch and Bear Creek. Ice wedges were described in terms of their size, the color of ice, internal structure, existence and form of gas bubbles and were sampled by chain saw as blocks. The frozen sediment was cleaned, and ice, sediment and cryostructures were described, followed by sediment sampling with an axe and hammer. Separately, sediment cores were collected with a battery driven drill for biomarker studies. In our presentation, we present the first results of new field and laboratory studies. This concerns age determinations, sediment data, stable isotopes and hydrochemistry of the ground ice. The mean ice content measured was 38 ± 10 wt%. We expect new knowledge regarding the reconstruction of Late Quaternary environment of Central Yukon. References Fraser, T.A. and Burn, C.R. 1997: On the nature and origin of "muck" deposits in the Klondike area, Yukon Territory, Canadian Journal of Earth Sciences 34(10), 1333-1344, https://doi.org/10.1139/e17-106. Froese, D., Zazula, G., Westgate, J., Preece, S., Sanborn, P. A., Reyes, A., and Pearce, N. 2009: The Klondike goldfields and Pleistocene environments of Beringia, GSA Today, 19, 4-10, https://doi.org/10.1130/GSATG54A.1. Kotler, E. and Burn, C. R. 2000: Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory, Can. J. Earth Sci., 37, 849-861, https://doi.org/10.1139/e00-013. Monteath, A. J., Kuzmina, S., Mahony, M., Calmels, F., Porter, T., Mathewes, R., Sanborn, P., Zazula, G., Shapiro, B., Murchie, T. J., Poinar, H. N., Sadoway, T., Hall, E., Hewitson, S., and Froese, D. 2023: Relict permafrost preserves megafauna, insects, pollen, soils and pore-ice isotopes of the mammoth steppe and its collapse in central Yukon, Quaternary Science Reviews, 299, 107878, https://doi.org/10.1016/j.quascirev.2022.107878. Porter, T. J., Froese, D. G., Feakins, S. J., Bindeman, I. N., Mahony, M. E., Pautler, B. G., Reichart, G. J., Sanborn, P. T., Simpson, M. J., and Weijers, J. W. H. 2016: Multiple water isotope proxy reconstruction of extremely low last glacial temperatures in Eastern Beringia (Western Arctic), Quaternary Science Reviews, 137, 113-125, https://doi.org/10.1016/j.quascirev.2016.02.006.

Description: The study of modern cave deposits forming under near isotopic equilibrium conditions can potentially help disentangle the processes influencing the oxygen isotope system and suitability of stalagmites as archives of past hydrological or thermal changes. We used cave monitoring to evaluate the impact of kinetic isotope fractionation and assess the conditions under which modern cave carbonates form in the Caumont cave and quarry system, located in Normandy, northwest France. Over 20 months, we collected climatological data, dripwater, and modern carbonate samples at 2–4-week intervals at three different stations inside the Caumont cave and quarry system. We find highly stable (10.4 ± 0.3 – 11.3 ± 0.1°C) temperature in the deeper sections of the Caumont cave and quarry system. The temporal dynamics of δ18 Odrip indicates that the drip water composition in Caumont reflects the original (though subdued) signal of precipitation, rather than the impact the seasonal to interannual cave air temperature has on isotopic fractionation. The monitoring reveals that δ13 C of modern carbonate is influenced by prior carbonate precipitation that occurs during the summer season when evapotranspiration can minimize effective infiltration. Comparison of δ18 O from dripwater and modern calcite, precipitated on glass plates and collected every two to four weeks, reveals that modern calcite forms near oxygen isotope equilibrium. A Hendy test on modern carbonate deposited on a stalagmite-shaped glass flask over 20 months confirms this finding because neither does δ13 C increase with distance from the apex, nor are δ13 C and δ18 O positively correlated. We conclude that the δ13 C signal in speleothems reflect summer (and longer-term) prior carbonate precipitation in response to effective infiltration dynamics, and that the δ18 O signal likely reflects annual to multi-annual changes in the composition of precipitation above the cave.

Description: Tropospheric reactive bromine (Bry) influences the oxidation capacity of the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol acidity plays a crucial role in Bry abundances through acid-catalyzed debromination from sea-salt-aerosol, the largest global source. Bromine concentrations in a Russian Arctic ice-core, Akademii Nauk, show a 3.5-fold increase from pre-industrial (PI) to the 1970s (peak acidity, PA), and decreased by half to 1999 (present day, PD). Ice-core acidity mirrors this trend, showing robust correlation with bromine, especially after 1940 (r = 0.9). Model simulations considering anthropogenic emission changes alone show that atmospheric acidity is the main driver of Bry changes, consistent with the observed relationship between acidity and bromine. The influence of atmospheric acidity on Bry should be considered in interpretation of ice-core bromine trends.

Description: Oxygen isotopes in biogenic silica (δ18OBSi) from lake sediments allow for quantitative reconstruction of past hydroclimate and proxy-model comparison in terrestrial environments. The signals of individual records have been attributed to different factors, such as air temperature (Tair), atmospheric circulation patterns, hydrological changes, and lake evaporation. While every lake has its own local set of drivers of δ18O variability, here we explore the extent to which regional or even global signals emerge from a series of paleoenvironmental records. This study provides a comprehensive compilation and combined statistical evaluation of the existing lake sediment δ18OBSi records, largely missing in other summary publications (i.e. PAGES network). For this purpose, we have identified and compiled 71 down-core records published to date and complemented these datasets with additional lake basin parameters (e.g. lake water residence time and catchment size) to best characterize the signal properties. Records feature widely different temporal coverage and resolution, ranging from decadal-scale records covering the past 150 years to records with multi-millennial-scale resolution spanning glacial-interglacial cycles. The best coverage in number of records (NCombining double low line37) and data points (NCombining double low line2112) is available for Northern Hemispheric (NH) extratropical regions throughout the Holocene (roughly corresponding to Marine Isotope Stage 1; MIS 1). To address the different variabilities and temporal offsets, records were brought to a common temporal resolution by binning and subsequently filtered for hydrologically open lakes with lake water residence times 〈100 years. For mid- to high-latitude (〉45°N) lakes, we find common δ18OBSi patterns among the lake records during both the Holocene and Common Era (CE). These include maxima and minima corresponding to known climate episodes, such as the Holocene Thermal Maximum (HTM), Neoglacial Cooling, Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). These patterns are in line with long-term air temperature changes supported by previously published climate reconstructions from other archives, as well as Holocene summer insolation changes. In conclusion, oxygen isotope records from NH extratropical lake sediments feature a common climate signal at centennial (for CE) and millennial (for Holocene) timescales despite stemming from different lakes in different geographic locations and hence constitute a valuable proxy for past climate reconstructions.

Description: Seed dispersal affects gene flow and hence genetic differentiation of plant populations. During the Late Quaternary, most fruit-eating and seed-dispersing megafauna went extinct, but whether these animals have left signatures in the population genetics of their food plants, particularly those with large, ‘megafaunal’ fruits (i.e. 〉4 cm—megafruits), remains unclear.Here, we assessed the population history, genetic differentiation and recent migration among populations of four animal-dispersed palm (Arecaceae) species with large (Borassus madagascariensis), medium-sized (Hyphaene coriacea, Bismarckia nobilis) and small (Chrysalidocarpus madagascariensis) fruits on Madagascar. We integrated double-digest restriction-site-associated DNA sequencing (ddRAD) of 167 individuals from 25 populations with (past) distribution ranges for extinct (e.g., giant lemurs and elephant birds) and extant seed-dispersing animals, landscape and human impact data, and applied linear mixed-effects models to explore the drivers of genetic variation in Malagasy palms.Palm populations that shared more megafrugivore species in the past had lower genetic differentiation than populations that shared fewer megafrugivore species. This suggests that megafrugivore-mediated seed dispersal in the past may have led to frequent gene flow among populations. In comparison, extant frugivore diversity only decreased genetic differentiation in the small-fruited palm. Furthermore, genetic differentiation of all palm species decreased with landscape connectivity (i.e. environmental suitability, forest cover and river density) and human impact (i.e. road density), while migration rates of the small-fruit palm increased with road density.Synthesis. Our results suggest that the legacy of megafrugivores regularly achieving long dispersal distances is still reflected in the population genetics of palms that were formerly dispersed by such animals. Furthermore, low genetic differentiation was possibly maintained after the megafauna extinctions through alternative dispersal (e.g. human- or river-mediated), long generation times and long lifespans of these megafruit palms. Our study illustrates how species interactions that happened 〉1000 years ago can leave imprints in their population genetics.

Description: In this paper, two species of the water mite genus Kongsbergia Thor, 1899 (Aturidae), i.e., K. uttarakhandensis Pešić & Smit n. sp. and K. tuzovskiji Pešić & Smit n. sp. are described from streams in Uttarakhand State of India. The latter species was named after late Dr Petr Tuzovskij for his outstanding contribution to the research of water mites.

Description: Acanthodes has long been the primary source of information on the pharyngeal skeleton of ‘acanthodians’. Because of this its anatomy has played a disproportionate role in attempts to understand the evolution of the jawed vertebrate pharynx and the clade as a whole. However, the anatomy of the pharynx of Acanthodes, now understood to be a stem-group chondrichthyan, remains poorly characterized and subject to several com- peting interpretations. We used computed tomography to image the articulated pharyngeal skeletons of three specimens of Acanthodes confusus from Lebach, Germany. Acanthodes has a mélange of osteichthyan-like and chondrichthyan-like morphologies in its pharyngeal skeleton. Like many other chondrichthyans, Acanthodes lacked hypohyals, and had four pairs of posteriorly oriented pharyngobranchials. Like osteichthyans, Acanthodes possessed an interhyal, but lacked the separate infra- and supra-pharyngobranchial elements present in osteichthyans and the crown- chondrichthyan Ozarcus. Using these new data we built and animated a digital 3D model of the pharyngeal endoskeleton in Acanthodes, showing that the jaws could have swung outwards during the opening cycle, increasing the anteriorly facing area of the gape for suspension feeding. These new data provide a more definitive picture of the anatomy of a taxon that has long been of great significance in early vertebrate palaeontology.

Description: This study presents the mathematical framework and experiments to achieve an orbit and clock combination using Multi-GNSS products. Over the past years, the International GNSS Service (IGS) has been putting efforts into extending its service by setting up and running the Multi-GNSS Experiment and Pilot Project (MGEX). Several MGEX Analysis Centers (ACs) contribute by providing solutions containing not only GPS and GLONASS but also Galileo, BeiDou, and QZSS. As the current IGS combination software can only handle one constellation at a time, obtaining a consistent MGEX orbit and clock product requires substantial modifications. Therefore is presented a least-squares framework for a Multi-GNSS orbit and clock combination, where the weights used to combine the ACs’ products are determined by least-squares variance component estimation. Two different weighting strategies are proposed and discussed: AC specific weights or AC and constellation specific weights. An automated Z-score test is implemented, yielding a common set of core satellites that are used to determine the weights. Both strategies are tested using MGEX orbit and clock solutions for a period of two and a half years, where the two data processing yielded similar results. The agreement with the ACs’ orbits is around one centimeter level for GPS and up to a few centimeters for the other constellations. The 3D-RMS is generally slightly better with the AC and constellation weighting. As a validation of the strategies, a comparison of our combination approach with the official IGS combination using three years of GPS and GLONASS orbits shows an agreement of better than 5 mm and 12 mm for GPS and GLONASS, respectively. An external validation using Satellite Laser Ranging (SLR) shows that the mean residuals of our combined products are around −3 mm for Galileo, 6 mm for GLONASS, −8 mm for BeiDou, and −31 mm for QZSS. For the clock products, the agreement with the IGS final product is around 32 ps and the Precise Point Positioning (PPP) analysis showed that the combined product agrees with the residuals of the ACs with values of less than 10 mm. The MGEX clock combination showed that most of the ACs agreement is below 80 ps for GPS and Galileo, and for the other constellations, the values are more sparse. In addition, it is noted that SHA and JAX presented big discrepancies compared with the other ACs. The validation is performed again in comparison IGS official combination where the agreement with the presented solutions is around 32 ps. A PPP processing is also performed using the combined solutions, showing the suitability of the products. The ACs products from the IGS third reprocessing campaign are also used as input in the combination and discussed. Finally, an extension of the orbit combination is done for the combination of Low Earth Orbit (LEO) satellites. The results show that the proposed combination can deliver reliable products following the standards of the IGS.

Description: Diese Studie stellt den mathematischen Rahmen und die Experimente vor, um eine Kombination von Umlaufbahn und Uhr mit Hilfe von Multi-GNSS-Produkten zu erreichen. In den letzten Jahren hat der International GNSS Service (IGS) Anstrengungen unternommen, um seinen Dienst durch die Einrichtung und Durchführung des Multi-GNSS-Experiment- and Pilot Project (MGEX) zu erweitern. Mehrere MGEX Analysis Centers (ACs) tragen dazu bei, indem sie Lösungen anbieten, die nicht nur GPS und GLONASS, sondern auch Galileo, BeiDou und QZSS enthalten. Da die derzeitige IGS-Kombinationssoftware jeweils nur eine Konstellation verarbeiten kann, sind für den Erhalt eines konsistenten MGEX-Bahn und Uhrenprodukts erhebliche Änderungen erforderlich. Daher wird ein Least-Squares-Rahmen für eine Multi-GNSS-Bahn- und Uhrenkombination vorgestellt, bei dem die zur Kombination der AC-Produkte verwendeten Gewichte durch eine Least-Squares-Varianzkomponentenschätzung bestimmt werden. Es werden zwei verschiedene Gewichtungsstrategien vorgeschlagen und diskutiert: AC-spezifische Gewichte oder AC- und konstellationsspezifische Gewichte. Es wird ein automatischer Z-Score-Test durchgeführt, der einen gemeinsamen Satz von Kernsatelliten ergibt, die zur Bestimmung der Gewichte verwendet werden. Beide Strategien werden anhand von MGEX-Bahn- und Uhrenlösungen über einen Zeitraum von zweieinhalb Jahren getestet, wobei die beiden Datenverarbeitungen ähnliche Ergebnisse erbrachten. Die Übereinstimmung mit den Bahnen der ACs liegt bei GPS bei etwa einem Zentimeter und bei den anderen Konstellationen bei bis zu einigen Zentimetern. Der 3D-RMS ist im Allgemeinen etwas besser mit der AC- und Konstellationsgewichtung. Zur Validierung der Strategien zeigt ein Vergleich unseres Kombinationsansatzes mit der offiziellen IGS-Kombination unter Verwendung von GPS- und GLONASS-Umlaufbahnen aus drei Jahren eine Übereinstimmung von besser als 5 mm und 12 mm für GPS bzw. GLONASS. Eine externe Validierung mittels Satellite Laser Ranging (SLR) zeigt, dass die mittleren Residuen unserer kombinierten Produkte bei etwa −3 mm für Galileo, 6 mm für GLONASS, −8 mm für BeiDou und −31 mm für QZSS liegen. Bei den Uhrenprodukten liegt die Übereinstimmung mit dem IGS-Endprodukt bei etwa 32 ps, und die Analyse der präzisen Precise Point Positioning (PPP) ergab, dass das kombinierte Produkt mit den Residuen der ACs mit Werten von weniger als 10 mm übereinstimmt. Die MGEX-Uhrenkombination zeigte, dass die meisten ACs unter 80 ps für GPS und Galileo übereinstimmen, und für die anderen Konstellationen sind die Werte spärlicher. Darüber hinaus ist festzustellen, dass SHA und JAX im Vergleich zu den anderen ACs große Diskrepanzen aufweisen. Die Validierung erfolgt wiederum im Vergleich mit der offiziellen IGS-Kombination, bei der die Übereinstimmung mit den vorgestellten Lösungen bei etwa 32 ps liegt. Eine PPP-Verarbeitung wird ebenfalls unter Verwendung der kombinierten Lösungen durchgeführt, was die Eignung der Produkte zeigt. Die ACs-Produkte aus der dritten IGS-Reprocessing-Kampagne werden ebenfalls als Input für die Kombination verwendet und diskutiert. Schließlich wird eine Erweiterung der Orbit-Kombination für die Kombination von Low Earth Orbit (LEO)-Satelliten durchgeführt. Die Ergebnisse zeigen, dass die vorgeschlagene Kombination zuverlässige Produkte gemäß den Standards des IGS liefern kann.