ALBERT

Description: The Caribbean and South American tectonic plates bound the north-eastwards expulsion of the North Andean Block in western Venezuela. This complex geodynamic setting resulted in the formation of major strike-slip fault systems and sizeable mountain chains. The 100-km-wide Mérida Andes extend from the Colombian/Venezuelan border to the Caribbean coast. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Knowledge of lithospheric structures, related to the formation of the Mérida Andes, is limited though, due to a lack of deep geophysical data. In this study, we present results of the first broad-band magnetotelluric profile crossing the Mérida Andes and the Maracaibo and Barinas–Apure foreland basins on a length of 240 km. Geoelectrical strike and dimensionality analysis are consistent with 1-D or 2-D subsurface structures for the sedimentary basins but also indicate a strong 3-D setting for the Mérida Andes. Using a combination of 2-D and 3-D modelling we systematically examined the influence of 3-D structures on 2-D inversions. Synthetic data sets derived from 3-D modelling allow identification and quantification of spurious off-profile features as well as smoothing artefact due to limited areal station coverage of data collected along a profile. The 2-D inversion models show electrically conductive basins with depths of 2–5 km for the Barinas-Apure and 2–7 km for the Maracaibo basins. A number of resistive bodies within the Maracaibo basin could be related to active deformation causing juxtaposition of older geological formations and younger basin sediments. The most important fault systems of the area, the Boconó and Valera Faults, cross-cut the Mérida Andes in NE–SW direction along its strike on a length 400 km and N–S direction at its centre on a length 60 km, respectively. Both faults are associated with subvertical zones of high electrical conductivity and sensitivity tests suggest that they reach depths of up to 12 km. A sizeable conductor at 50 km depth, which appears consistently in the 2-D sections, could be identified as an inversion artefact caused by a conductor east of the profile. We speculate the high conductivity associated with the off-profile conductor may be related to the detachment of the Trujillo Block. Our results partially support the ‘floating orogen hypothesis’ developed to explain the geodynamic evolution of western Venezuela and they highlight the relevance of the Trujillo Block in this process.

Description: Gases encountered in different salt beds from evacuated and packer-sealed borehole sections in a potash mine were sampled and characterized for their chemical and isotopic composition so as to conclude on their origin and evolution in the salt rocks. These gases were either generated autochthonally or originate from fluid influx from the surrounding rocks outside the salt formation. Fixation in the salt rocks can take place laminar on mineral grain boundaries, disrupter and fracture zones or trapped in inclusions inside or between mineral grains. In situ flow tests with pure argon between several boreholes at distances ranging from decimeter to meter suggest that formation gas is stripped from the intermediate salt packet. This gas must have been trapped on grain boundaries along the pathways of the flowing argon. The stripped formation gas comprises mainly CO2 with traces of CH4 and H2. The CO2 isotopic composition matches well with gases originating from a mantle source, whereas CH4 is classified to be of thermogenic origin formed in a marine environment. Plausible explanations for the H2 generation are the radiolysis of water, reaction of FeII with water or microbial processes. We conclude that these trapped gases are of allochthonous origin migrating from the surrounding rocks into the salt formation where they were fixated mainly along fracture surfaces and fissures.

Description: Satellite remote sensing offers the possibility to monitor the Earth's surface at high temporal and spatial resolutions. An important methodological field is the detection and interpretation of changes on the Earth’s surface. A robust and widely utilized family of approaches is post-classification change-detection (PCCD). In our research, we address an important challenge to using PCCD from a user’s perspective. Users often face difficulties finding changes in the result sets of PCCD that are relevant to their application scenarios. We propose a Visual Analytics approach that supports users in terms of exploring the temporal dynamics and the spatial distribution of automatically-detected changes generated via PCCD.

Description: Radio-Magnetotelluric (RMT) method is based on measurements of the electromagnetic (EM) field of remote radio transmitters in a frequency range of 10 – 1000 kHz where CSRMT measures the EM field from a controlled-source in a wider frequency range of 1 – 1000 kHz. This, results to a higher signal to noise ratio compare to RMT method. Two perpendicular transmitters with 800 meters long, are used in this experiment. Therefore, the full impedance tensor and the tipper elements will be observed. In order to increase the data coverage, RMT measurements also carried out when the transmitter was off . These, also used to test the near-field condition. In this study, near-field is also been considered as well as far-field.

Description: Das Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung ist nun bereits seit 1962 fester Bestandteil des wissenschaftlichen Austausches für Wissenschaftlerinnen und Wissenschaftler aus dem Bereich der Geophysik mit Schwerpunkt Elektromagnetik (EM) in Deutschland. Alle zwei Jahre bietet das Kolloquium einen besonderen Rahmen, aktuelle Arbeiten vorzustellen und neue Aspekte der Erforschung des Untergrundes mit elektromagnetischen Methoden zu diskutieren. Das 28. Kolloquium fand vom 23. bis 27. September 2019 in Haltern am See statt. Es wurde von der Arbeits- gruppe „Elektromagnetik“ der Westfälischen Wilhelms-Universität Münster unter der Leitung von Prof. Michael Becken ausgerichtet.

Description: This report compiles observations made within a time frame of two months on 24 representative thin-section samples representing the periods before and after 4- and 9-years of injection of CO2 into the reservoir. Given this short period of time until completion of this report, some observations and conclusions drawn have to be judged preliminary. Further analytical work and in-depth interpretation of the results are underway. Information provided for the period 0–4 years after CO2 injection include observations made by S. Bock in the framework of her not yet finished Ph.D. thesis.

Description: Abstract Back to top Although the knowledge of the gravity of the Earth has improved considerably with CHAMP, GRACE, and GOCE (see appendices for a list of abbreviations) satellite missions, the geophysical community has identified the need for the continued monitoring of the time-variable component with the purpose of estimating the hydrological and glaciological yearly cycles and long-term trends. Currently, the GRACE-FO satellites are the sole dedicated provider of these data, while previously the GRACE mission fulfilled that role for 15 years. There is a data gap spanning from July 2017 to May 2018 between the end of the GRACE mission and start the of GRACE-FO, while the Swarm satellites have collected gravimetric data with their GPS receivers since December 2013. We present high-quality gravity field models (GFMs) from Swarm data that constitute an alternative and independent source of gravimetric data, which could help alleviate the consequences of the 10-month gap between GRACE and GRACE-FO, as well as the short gaps in the existing GRACE and GRACE-FO monthly time series. The geodetic community has realized that the combination of different gravity field solutions is superior to any individual model and set up the Combination Service of Time-variable Gravity Fields (COST-G) under the umbrella of the International Gravity Field Service (IGFS), part of the International Association of Geodesy (IAG). We exploit this fact and deliver the highest-quality monthly GFMs, resulting from the combination of four different gravity field estimation approaches. All solutions are unconstrained and estimated independently from month to month. We tested the added value of including kinematic baselines (KBs) in our estimation of GFMs and conclude that there is no significant improvement. The non-gravitational accelerations measured by the accelerometer on board Swarm C were also included in our processing to determine if this would improve the quality of the GFMs, but we observed that is only the case when the amplitude of the non-gravitational accelerations is higher than during the current quiet period in solar activity. Using GRACE data for comparison, we demonstrate that the geophysical signal in the Swarm GFMs is largely restricted to spherical harmonic degrees below 12. A 750 km smoothing radius is suitable to retrieve the temporal variations in Earth's gravity field over land areas since mid-2015 with roughly 4 cm equivalent water height (EWH) agreement with respect to GRACE. Over ocean areas, we illustrate that a more intense smoothing with 3000 km radius is necessary to resolve large-scale gravity variations, which agree with GRACE roughly at the level of 1 cm EWH, while at these spatial scales the GRACE observes variations with amplitudes between 0.3 and 1 cm EWH. The agreement with GRACE and GRACE-FO over nine selected large basins under analysis is 0.91 cm, 0.76 cm yr−1, and 0.79 in terms of temporal mean, trend, and correlation coefficient, respectively.

Description: Elevated levels of arsenic (As) in soils and groundwaters remain a pressing global challenge due to its widespread occurrence and distribution, high toxicity and mobility. In oxygen-limited subsurface conditions, redox-active mineral phases can be important substrates in controlling the fate and mobility of As in the environment. Among these redox-active minerals, green rust (GR) phases, an Fe(II)-Fe(III)-bearing layered double hydroxide, have been shown to be able to sequester a wide range of toxic metals and metalloids, including As. However, very little is known regarding how GR phases interact with As species and what is the fate of the immobilized As under dynamic geochemical conditions. GR phases are suggested to form through the transformation of metastable iron mineral phases in non-sulfidic, reducing environments. However, the exact mechanism and pathway of this transformation, as well as the fate of mineral-associated As (i.e. whether it is re-released back into the groundwater by desorption, dissolution or redox transformation) is not yet known but critically needed for modelling As cycling in contaminated environments. To address these knowledge gaps, I conducted a series of experimental geochemical studies and combined them with various laboratory- and synchrotron-based solid and liquid phase characterization methods to examine the interaction between GR sulfate (GRSO4) and As species [As(III) and As(V)]. Specifically, I performed several batch experiments under anoxic and near-neutral pH conditions to determine As-GR interaction mechanisms during GR formation and transformation. Moreover, I also quantified how these transformation reactions affect the toxicity and mobility of As species in contaminated environments. From the batch adsorption experiments, I showed that synthetic GRSO4 can adsorb up to 160 and 105 mg of As(III) and As(V) per g of solid, respectively. These adsorption capacities are among the highest reported for iron (oxyhydr)oxides that form in soils and groundwaters. Results from this study also show that As removal by GRSO4 can be inhibited by several geochemical parameters such as pH, high ionic strength, presence of co-existing inorganic ions (e.g., Mg2+, PO43-, Si) and low temperature. I also employed an integrated nano-scale solid-state characterization approach to elucidate As-GRSO4 interactions. Specifically, I combined scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray (EDX) spectroscopy together with bulk synchrotron-based X-ray techniques including high energy X-ray total scattering, pair distribution function (PDF) analysis and X-ray absorption spectroscopy (XAS). With these, I was able to directly visualize and pinpoint As binding sites at the GR surface sites and to identify the binding mechanism for both As(III) and As(V). In the case of As(III)-reacted GR, STEM-EDX maps showed that As(III) were preferentially adsorbed at the GR crystal edges, primarily as bidentate binuclear (2C) inner-sphere surface complexes based from the differential PDF and As K-edge XAS data. For the As(V)-reacted GR, As(V) was sequestered as a newly-formed As-bearing mineral phase parasymplesite and as adsorbed As(V) species at the GR edges (in 2C geometry). To assess the fate of As in subsurface environments, I studied As during GR formation and transformation to quantify As uptake and/or its potential release back into solution and the stability of GR and other Fe (oxhydr)oxide phases in this process. During the Fe2+-induced transformation of As(V)-bearing ferrihydrite, I followed the changes in aqueous behavior and speciation of As, as well as the changes in composition of the Fe mineral phases, as a function of varying Fe2+(aq)/Fe(III)solid ratios (0.5, 1 ,2). In all the ratios tested, GRSO4, goethite and lepidocrocite formed in the early stages of transformation (≤ 2h). However, at low ratios (〈2), the initially formed GRSo4 and/or lepidocrocite disappeared as the reaction progressed, leaving goethite and unreacted ferrihydrite after 24 h. At an Fe2+(aq)/Fe(III)solid ratio of 2, GRSO4 was formed and remained in the solids until the end of the 24-h transformation, with goethite and unreacted ferrihydrite. The initial As(V) was partially reduced to As(III) by the surface-associated Fe2+-GT redox couple, and extent of reduction increased from 34 to 44% as Fe2+(aq)/Fe(III)solid ratios increased. Despite this reduction to the more mobile and more toxic As(III) species, no significant As release was observed during the mineral transformation reactions. Finally, I tested the long-term stability and reactivity of GR by aging synthetic GRSO4 in pristine and As-spiked natural groundwater at ambient (25 °C) and low (4 °C) temperatures. The spiked As in the groundwater was completely removed after 120 days at 25 °C while the removal rate was ~2 times slower at 4 °C with only ~66% As removal after 120 days. On the other hand, the stability of synthetic GRSO4 in groundwater was strongly affected by the presence of adsorbed As species and temperature. At ambient temperature, the initial GRSO4 aged in As-free groundwater was converted to GRCO3 by ion exchange within a few days and both GR phases eventually transformed to magnetite after 120 days. Remarkably, both the addition of As species in groundwater and lowering the temperature increased long-term GRSO4 stability through the inhibition of (a) ion exchange in the GRSO4 interlayer (i.e., slower conversion to GRCO3) and (b) transformation of GR to magnetite. Moreover, a synergistic stabilization effect was observed with both As addition and low temperature, significantly enhancing GR stability up to a year. Overall, the work presented in this thesis clearly emphasizes the potential role of GR phases in controlling the mobility and toxicity of As species in subsurface environments. Specifically, I contributed to the fundamental understanding of the reactions involving As(III) and As(V) at GR surfaces, elucidating the relevant binding mechanisms and visualizing specific binding sites of immobilized As species. This work also identified critical geochemical factors that affect As removal and GR formation and transformation under anoxic and circum-neutral pH conditions. More importantly, I was able to show the enhanced long-term stability of GR in natural groundwaters and its prolonged reactivity for As sequestration.

Description: The West Bohemian Massif as part of the geodynamically active European Cenozoic Rift System is characterised by ongoing magmatic processes in the intra-continental lithospheric mantle. A series of phenomena such as massive degassing of CO2 and repeated earthquake swarms make the Eger Rift a unique target area for European intra-continental geo-scientific research. The ICDP project "Drilling the Eger Rift" was funded to study the field of earthquake-fluid-rock-biosphere interaction. In the framework of this ICDP project, magnetotelluric (MT) experiments have been conducted to image the subsurface distribution of the electrical conductivity down to depths of several tens of kilometres as the electrical conductivity is particularly sensitive to the presence of high-conductive phases such as aqueous fluids, partial melts or metallic compounds. Based on recent MT experiments in 2015/2016, Munoz et al. (2018) presented 2D images of the electrical conductivity structure along a NS profile across the Eger Rift. It reveals a conductive channel at the earthquake swarm region that extend from the lower crust to the surface forming a pathway for fluids up to the region of the mofettes. A second conductive channel is present in the south of the model. Due to the given station setup along a profile, the resulting 2D inversion allows ambiguous interpretations of this feature. As 3D inversion is required to distinguish between the different interpretations, we conducted another MT field experiment at the end of 2018. This data publication (10.5880/GIPP-MT. 201810 .1) encompasses a detailed report in pdf format with a description of the project, information on the experimental setup, data collection, instrumentation used, recording configuration and data quality. The folder structure and content of the data repository are described in detail in Ritter et al. (2019). Time-series data are provided in EMERALD format (Ritter et al., 2015).

Description: The potential of polar compound compositions from electrospray ionization ultra-high resolution mass spectrometry (FT-ICR-MS) to characterize petroleum fluids as well as petroleum system processes is shown in the example of the Eagle Ford Formation in Texas, USA. A set of six black oil and nine source-rock bitumen samples is investigated with respect to its organic nitrogen-, sulphur- and oxygen-compound inventory in order to assess maturity, depositional environment, lithofacies and retention and migration behaviour. Compared to conventional geochemical tools based on molecular parameters from gas chromatographic analyses, FT-ICR-MS enables a maturity assessment from immature to late mature stage, which is barely influenced by source or depositional environment. Due to the increased molecular mass and polarity range of its target compounds, FT-ICR-MS is the most convincing tool to describe the retention and fractionation of polar compounds in a petroleum system.

Description: The dataset presented here is an earthquake catalog for the Central Sea of Marmara (Turkey) obtained by applying a matched-fliter technic to continuous waveforms. The magnitude of completeness of this catalog is Mc=1.1. We use as templates events published by national agencies (KOERI and AFAD). The matched-fliter technic is described in Bentz et al. (2020). The column of the data file are: event ID, Year, Month, Day, Hour, Minute, Seconds, Matlab time (serial time), Latitude (dec.degrees), Longitude (dec.degrees), Depth (km), Magnitude, Cross-correlation coefficient (CC), Template ID, MAD(ratio between CC and median absolution of daily correlogram), Quality flag The ZIP files contains configuration files for ph2dt and HypoDD applications together with input phase and seismic network data.

Description: This cumulative thesis is concerned with the evolution of geomagnetic activity since the beginning of the 20th century, that is, the time-dependent response of the geomagnetic field to solar forcing. The focus lies on the description of the magnetospheric response field at ground level, which is particularly sensitive to the ring current system, and an interpretation of its variability in terms of the solar wind driving. Thereby, this work contributes to a comprehensive understanding of long-term solar-terrestrial interactions. The common basis of the presented publications is formed by a reanalysis of vector magnetic field measurements from geomagnetic observatories located at low and middle geomagnetic latitudes. In the first two studies, new ring current targeting geomagnetic activity indices are derived, the Annual and Hourly Magnetospheric Currents indices (A/HMC). Compared to existing indices (e.g., the Dst index), they do not only extend the covered period by at least three solar cycles but also constitute a qualitative improvement concerning the absolute index level and the ~11-year solar cycle variability. The analysis of A/HMC shows that (a) the annual geomagnetic activity experiences an interval-dependent trend with an overall linear decline during 1900–2010 of ~5 % (b) the average trend-free activity level amounts to ~28 nT (c) the solar cycle related variability shows amplitudes of ~15–45 nT (d) the activity level for geomagnetically quiet conditions (Kp〈2) lies slightly below 20 nT. The plausibility of the last three points is ensured by comparison to independent estimations either based on magnetic field measurements from LEO satellite missions (since the 1990s) or the modeling of geomagnetic activity from solar wind input (since the 1960s). An independent validation of the longterm trend is problematic mainly because the sensitivity of the locally measured geomagnetic activity depends on geomagnetic latitude. Consequently, A/HMC is neither directly comparable to global geomagnetic activity indices (e.g., the aa index) nor to the partly reconstructed open solar magnetic flux, which requires a homogeneous response of the ground-based measurements to the interplanetary magnetic field and the solar wind speed. The last study combines a consistent, HMC-based identification of geomagnetic storms from 1930–2015 with an analysis of the corresponding spatial (magnetic local time-dependent) disturbance patterns. Amongst others, the disturbances at dawn and dusk, particularly their evolution during the storm recovery phases, are shown to be indicative of the solar wind driving structure (Interplanetary Coronal Mass Ejections vs. Stream or Co-rotating Interaction Regions), which enables a backward-prediction of the storm driver classes. The results indicate that ICME-driven geomagnetic storms have decreased since 1930 which is consistent with the concurrent decrease of HMC. Out of the collection of compiled follow-up studies the inclusion of measurements from high-latitude geomagnetic observatories into the third study’s framework seems most promising at this point.

Description: The Cheb Basin (CZ) is a shallow Neogene intracontinental basin located in the western Eger Rift. The Cheb Basin is characterized by active seismicity and diffuse degassing of mantle-derived CO2 in mofette fields. Within the Cheb Basin, the Hartoušov mofette field shows a daily CO2 flux of 23–97 tons. More than 99% of CO2 released over an area of 0.35 km2. Seismic active periods have been observed in 2000 and 2014 in the Hartoušov mofette field. Due to the active geodynamic processes, the Cheb Basin is considered to be an ideal region for the continental deep biosphere research focussing on the interaction of biological processes with geological processes. To study the influence of CO2 degassing on microbial community in the surface and subsurface environments, two 3-m shallow drillings and a 108.5-m deep scientific drilling were conducted in 2015 and 2016 respectively. Additionally, the fluid retrieved from the deep drilling borehole was also recovered. The different ecosystems were compared regarding their geochemical properties, microbial abundances, and microbial community structures. The geochemistry of the mofette is characterized by low pH, high TOC, and sulfate contents while the subsurface environment shows a neutral pH, and various TOC and sulfate contents in different lithological settings. Striking differences in the microbial community highlight the substantial impact of elevated CO2 concentrations and high saline groundwater on microbial processes. In general, the microorganisms had low abundance in the deep subsurface sediment compared with the shallow mofette. However, within the mofette and the deep subsurface sediment, the abundance of microbes does not show a typical decrease with depth, indicating that the uprising CO2-rich groundwater has a strong influence on the microbial communities via providing sufficient substrate for anaerobic chemolithoautotrophic microorganisms. Illumina MiSeq sequencing of the 16S rRNA genes and multivariate statistics reveals that the pH strongly influences the microbial community composition in the mofette, while the subsurface microbial community is significantly influenced by the groundwater which motivated by the degassing CO2. Acidophilic microorganisms show a much higher relative abundance in the mofette. Meanwhile, the OTUs assigned to family Comamonadaceae are the dominant taxa which characterize the subsurface communities. Additionally, taxa involved in sulfur cycling characterizing the microbial communities in both mofette and CO2 dominated subsurface environments. Another investigated important geo–bio interaction is the influence of the seismic activity. During seismic events, released H2 may serve as the electron donor for microbial hydrogenotrophic processes, such as methanogenesis. To determine whether the seismic events can potentially trigger methanogenesis by the elevated geogenic H2 concentration, we performed laboratory simulation experiments with sediments retrieved from the drillings. The simulation results indicate that after the addition of hydrogen, substantial amounts of methane were produced in incubated mofette sediments and deep subsurface sediments. The methanogenic hydrogenotrophic genera Methanobacterium was highly enriched during the incubation. The modeling of the in-situ observation of the earthquake swarm period in 2000 at the Novy Kostel focal area/Czech Republic and our laboratory simulation experiments reveals a close relation between seismic activities and microbial methane production via earthquake-induced H2 release. We thus conclude that H2 – which is released during seismic activity – can potentially trigger methanogenic activity in the deep subsurface. Based on this conclusion, we further hypothesize that the hydrogenotrophic early life on Earth was boosted by the Late Heavy Bombardment induced seismic activity in approximately 4.2 to 3.8 Ga.

Description: Das Eger-Becken (CZ) ist ein flaches, intrakontinentales neogenes Becken im westlichen Eger-Graben. Das Eger-Becken zeichnet sich durch aktive Seismizität und die diffuse Entgasung von aus dem Mantel stammenden CO2 in Mofettenfeldern aus. Das Mofettenfeld von Hartoušov weist einen täglichen CO2-Fluss von 23-97 Tonnen auf. Mehr als 99% des CO2 werden auf einer Fläche von 0,35 km2 freigesetzt. Im Untersuchungsgebiet wurden in den Jahren 2000 und 2014 seismisch aktive Perioden beobachtet. Aufgrund der aktiven geodynamischen Prozesse gilt das Egerer Becken als ideale Region für die kontinentale Tiefenbiosphärenforschung, die sich auf die Wechselwirkung von biologischen Prozessen mit geologischen Prozessen konzentriert. Zur Untersuchung des Einflusses der CO2-Entgasung auf die mikrobielle Gemeinschaft in der ober- und unterirdischen Umwelt wurden 2015 und 2016 zwei 3 m tiefe Flachbohrungen und eine 108,5 m tiefe wissenschaftliche Bohrung durchgeführt. Zusätzlich wurde auch aus dem Tiefbohrloch Flüssigkeit gewonnen. Die verschiedenen Ökosysteme wurden hinsichtlich ihrer geochemischen Eigenschaften, der mikrobiellen Abundanzen und der mikrobiellen Gemeinschaftsstrukturen verglichen. Die Geochemie der Mofetten zeichnet sich durch einen niedrigen pH-Wert und hohe TOC- und Sulfatgehalte aus, während das unterirdische Milieu einen neutralen pH-Wert und verschiedene TOC- und Sulfatgehalte in unterschiedlichen lithologischen Umgebungen aufweist. Auffällige Unterschiede in der mikrobiellen Gemeinschaft unterstreichen den erheblichen Einfluss erhöhter CO2-Konzentrationen und stark salzhaltigen Grundwassers auf mikrobielle Prozesse. Generell waren die mikrobiellen Abundanzen in dem tiefen Untergrundsediment im Vergleich zur flachen Mofette gering. Innerhalb der Mofette und des tiefen unterirdischen Sediments zeigt die Häufigkeit der Mikroorganismen jedoch keine typische Abnahme mit der Tiefe, was darauf hinweist, dass das aufsteigende CO2-reiche Grundwasser einen starken Einfluss auf die mikrobiellen Gemeinschaften hat, indem es genügend Substrat für anaerobe chemolithoautotrophe Mikroorganismen bietet. Die Illumina-MiSeq-Sequenzierung der 16S rRNA-Gene und die multivariate Statistik zeigen, dass der pH-Wert die Zusammensetzung der mikrobiellen Gemeinschaft in der Mofette signifikant bestimmt, während die unterirdische mikrobielle Gemeinschaft signifikant vom Grundwasser beeinflusst wird, das durch das ausgasende CO2 geprägt ist. Azidophile Mikroorganismen zeigen eine viel höhere relative Abundanz in der Mofette, wohingegen die der Familie Comamonadaceae zugeordneten OTUs die dominierenden Taxa der unterirdischen Gemeinschaften darstellen. Zusätzlich charakterisieren Taxa, die am Schwefelzyklus beteiligt sind, die mikrobiellen Gemeinschaften sowohl in der Mofette als auch in der CO2-dominierten unterirdischen Umwelt. Eine weitere wichtige Untersuchung der Geo-Bio-Interaktion ist der Einfluss der seismischen Aktivität. Während seismischer Ereignisse kann freigesetztes H2 als Elektronendonator für mikrobielle hydrogenotrophe Prozesse, wie z.B. die Methanogenese, dienen. Um zu bestimmen, ob die seismischen Ereignisse durch die erhöhten geogenen H2-Konzentrationen möglicherweise methanogene Prozesse auslösen können, führten wir Laborsimulationsexperimente mit Sedimenten durch, die aus den Bohrungen gewonnen wurden. Die Simulationsexperimente weisen darauf hin, dass nach der Zugabe von Wasserstoff beträchtliche Mengen an Methan in inkubierten Mofettensedimenten und tiefen unterirdischen Sedimenten produziert wurden. Die methanogene hydrogenotrophe Gattung Methanobacterium wurde während der Inkubation stark angereichert. Die Modellierung der in-situ-Beobachtung der Erdbeben-Schwarmzeit im Jahr 2000 im Schwerpunktgebiet Novy Kostel/Tschechische Republik und unsere Laborsimulationsexperimente zeigen einen engen Zusammenhang zwischen seismischen Aktivitäten und der biotischen Methanproduktion durch erdbebeninduzierte H2-Freisetzung. Wir kommen daher zu dem Schluss, dass H2 - dass bei seismischer Aktivität freigesetzt wird - möglicherweise methanogene Aktivität im tiefen Untergrund auslösen kann. Basierend auf dieser Schlussfolgerung gehen wir weiter davon aus, dass das frühe hydrogenotrophe Leben, durch die durch Late Heavy Bombardment induzierte seismische Aktivität in etwa 4,2 bis 3,8 Ga verstärkt wurde.

Description: The night has historically been neglected in both disciplinary and interdisciplinary research. To some extent, this is not surprising, given the diurnal bias of human researchers and the difficulty of performing work at night. The night is, however, a critical element of biological, chemical, physical, and social systems on Earth. Moreover, research into social issues such as inequality, demographic changes, and the transition to a sustainable economy will be compromised if the night is not considered. Recent years, however, have seen a surge in research into the night. We argue that “night studies” is on the cusp of coming into its own as an interdisciplinary field, and that when it does, the field will consider questions that disciplinary researchers have not yet thought to ask.

Description: Goethite-cemented duricrusts, also known as canga, commonly occur as a capping rock protecting underlying iron ore deposits. The processes that govern canga formation are still unclear but include recurrent partial dissolution and recrystallisation of goethite through biogeochemical cycling of iron, hypothesised to be catalysed by plants and bacteria. In the present study, the effect of plant exudates on mobilisation of iron in canga was examined using model plants grown on crushed canga in RHIZOtest devices, which separate roots from substrate by a semi-permeable membrane. Moderate plant-induced acidification of the canga was detected, however the primary driver of mineral dissolution was the synergistic effect of reductive and ligand-promoted dissolution, identified by an increase in organic acids concentration and the presence of low concentrations of free ferrous iron. Whilst organic acids exudation lasted, iron cations were stabilised in solution; once the organic acids were degraded by microorganisms, the free cations precipitated as iron oxy-hydroxides. Mineralogical analysis and high-resolution microscopy confirmed our hypothesis that plants that grow in this iron-rich substrate contribute to iron dissolution indirectly (e.g., during phosphate solubilisation), and that the resulting surplus iron not taken up by the plants is redeposited, promoting the cementation of the residual minerals. Understanding the contribution of plants to the iron cycling in canga is crucial when formulating post-mining rehabilitation strategies for iron ore sites.

Description: Hydrological extremes, in particular floods and droughts, impact all regions across planet Earth. They are mainly controlled by the temporal evolution of key hydrological variables like precipitation, evaporation, soil moisture, groundwater storage, surface water storage and discharge. Precise knowledge of the spatial and temporal evolution of these variables at the scale of river basins is essential to better understand and forecast floods and droughts. In this article, we present recent advances on the capability of Earth observation (EO) satellites to provide global monitoring of floods and droughts. The local scale monitoring of these events which is traditionally done using high-resolution optical or SAR (synthetic aperture radar) EO and in situ data will not be addressed. We discuss the applications of moderate- to low-spatial-resolution space-based observations, e.g., satellite gravimetry (GRACE and GRACE-FO), passive microwaves (i.e. SMOS) and satellite altimetry (i.e. the JASON series and the Copernicus Sentinel missions), with supporting examples. We examine the benefits and drawbacks of integrating these EO datasets to better monitor and understand the processes at work and eventually to help in early warning and management of flood and drought events. Their main advantage is their large monitoring scale that provides a “big picture” or synoptic view of the event that cannot be achieved with often sparse in situ measurements. Finally, we present upcoming and future EO missions related to this topic including the SWOT mission.

Description: The Flood Damage Database HOWAS 21 contains object-specific flood damage data resulting from fluvial, pluvial and groundwater flooding. The datasets incorporate various variables of flood hazard, exposure, vulnerability and direct tangible damage at properties from several economic sectors. The main purpose of development of HOWAS 21 was to support forensic flood analysis and the derivation of flood damage models. HOWAS 21 was first developed for Germany and currently almost exclusively contains datasets from Germany. However, its scope has recently been enlarged with the aim to serve as an international flood damage database; e.g. its web application is now available in German and English. This paper presents the recent advancements of HOWAS 21 and highlights exemplary analyses to demonstrate the use of HOWAS 21 flood damage data. The data applications indicate a large potential of the database for fostering a better understanding and estimation of the consequences of flooding.

Description: We study the crustal structure of Sri Lanka by analyzing data from a temporary seismic network deployed in 2016-2017 (Seneviratne et al., 2016) to shed light on the amalgamation process from the geophysical perspective. Rayleigh wave phase dispersion from ambient noise cross-correlation and receiver functions were jointly inverted using a transdimensional Bayesian approach (Bodin et al., 2012, Dreiling et al., 2019).

Description: In this study, a series of hydraulic fracturing tests under different injecting conditions was performed on Pocheon granite rock to account for the evolution of hydro-mechanical behavior during the fracturing process. We investigated the effect of the fluid viscosity and pressurization rate on the fracturing process of granite. Two different type of injection fluids, water and oil, were used under different pressurization rate. Visual inspection techniques such as X-ray computed tomography and thin section imaging were employed to capture the fracture pattern together with AE monitoring. As a result, the water injection case has larger saturation zone into the formation at breakdown while the oil infiltrates only vicinity of main fracture. The AE monitoring results show that the oil injection cases have a big sudden rise in the cumulative AE hit energy during fracture propagation which is more manifest under high pressurization rate. The induced fractures are observed to be larger in aperture and less tortuous for the higher fluid viscosity and higher pressurization rate cases through thin section images. On the other hand, the sleeve testing cases yield relatively very small aperture of induced fractures.

Description: The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. The Geodetic Observatory Pecný (GOPE) is located in the Czech Republic, about 40 km south-east of Prague, in the Central Bohemian hilly land at the elevation of about 500 m. It is surrounded by a mixed wood. Except for one local road the next nearest local road is about 1 km apart, the nearest railway is 5.2 km, the nearest village 1 km (Ondřejov). The bigger river (Sázava) flows through the valley at a distance of 5 km from the observatory at the height of about 300 m. No construction or other technological works (mines, industrial plants etc.) run either in the close surroundings or at longer distance. The hill Pecný is in the old metamorphic paleozoic synclinal zone of the Čerčany Chlum neighbouring with the Central Bohemian granitic massif and the perm massif of Černý Kostelec. From the geological point of view, GOPE was established in very stable region. GOPE is operated by the Research Institute of Geodesy, Topography and Cartography (RIGTC) and was established in 1957. GOPE has been involved in tidal observations with spring gravimeters since the early seventies of the last century, cooperation with the International Center for Earth Tides (ICET) has been dated since 1990. GOPE belongs to the core stations of ECGN - European Combined Geodetic Network, established by the EUREF IAG Subcommission. Since February 2007, the observatory type of one sphere superconducting gravimeter OSG-050 was running in the old gravimetric laboratory (OGL) of GOPE located in the cellar of the main building of GOPE (Latitude: 49.9137 N, Longitude: 14.7856 E, Elevation: 534.58 m), about 1.8 m under the ground of the surrounding relief. Almost uninterrupted 10-year time series of gravity record with OSG-050 has been carried out till October 2017, when the OSG-050 has been moved to the new gravimetric laboratory (NGL) situated in the top of the hill Pecný, less than 100 m from OGL. NGL (Latitude: 49.9141 N, Longitude: 14.7868 E, Elevation: 545.10 m) provides 3 concrete pillars in the ground level, which are founded to the bedrock (4 m below the ground). Two pillars are used for repeated observations with absolute gravimeters (AG) and in the third pillar, located in a separate room, the OSG-050 is running continuously. All rooms are thermally stabilized by air-conditioning systems. Due to the excellent stability of the station and the facilities to inter-compare different AGs, the GOPE was developed as a regional comparison site which serves as a reference for the Czech Gravimetric Network. Since 2001, repeated absolute measurements with interval of one month have been carried out in OGL and later in NGL to achieve continuous drift-free gravity time series by combination of absolute and superconducting data. At the area of the station, meteorological (precipitation, air temperature, humidity, air pressure) and hydrological (ground water and soil moisture) parameters are measured by different sensors. These data are available through auxiliary data in the IGETS database. Raw gravity and local atmospheric pressure records sampled at second and the same records decimated at 1‐minute samples are provided as Level 1 products of the IGETS network.

Description: Rivers have always flooded their floodplains. Over 2.5 billion people worldwide have been affected by flooding in recent decades. The economic damage is also considerable, averaging 100 billion US dollars per year. There is no doubt that damage and other negative effects of floods can be avoided. However, this has a price: financially and politically. Costs and benefits can be estimated through risk assessments. Questions about the location and frequency of floods, about the objects that could be affected and their vulnerability are of importance for flood risk managers, insurance companies and politicians. Thus, both variables and factors from the fields of hydrology and sociol-economics play a role with multi-layered connections. One example are dikes along a river, which on the one hand contain floods, but on the other hand, by narrowing the natural floodplains, accelerate the flood discharge and increase the danger of flooding for the residents downstream. Such larger connections must be included in the assessment of flood risk.

Description: Flüsse haben seit jeher ihre Auen überflutet. In den vergangenen Jahrzehnten waren weltweit über 2,5 Milliarden Menschen durch Hochwasser betroffen. Auch der ökonomische Schaden ist mit durchschnittlich 100 Milliarden US Dollar pro Jahr erheblich. Zweifelsohne können Schäden und andere negative Auswirkungen von Hochwasser vermieden werden. Allerdings hat dies einen Preis: finanziell und politisch. Kosten und Nutzen lassen sich durch Risikobewertungen abschätzen. Dabei werden in der Wasserwirtschaft, von Versicherungen und der Politik Fragen nach dem Ort und der Häufigkeit von Überflutungen, nach den Dingen, die betroffen sein könnten und deren Anfälligkeit untersucht. Somit spielen sowohl Größen und Faktoren aus den Bereichen der Hydrologie und Sozioökonmie mit vielschichtigen Zusammenhängen eine Rolle. Ein anschauliches Beispiel sind Deiche entlang eines Flusses, die einerseits in ihrem Abschnitt Überflutungen eindämmen, andererseits aber durch die Einengung der natürlichen Vorländer den Hochwasserabfluss beschleunigen und die Gefährdung für die Anlieger flussab verschärfen. Solche größeren Zusammenhänge müssen in der Bewertung des Hochwasserrisikos einbezogen werden. In derzeit gängigen Verfahren geht dies mit vereinfachenden Annahmen einher. Risikoabschätzungen sind daher unscharf und mit Unsicherheiten verbunden. Diese Arbeit untersucht den Nutzen und die Möglichkeiten neuer Datensätze für eine Verbesserung der Hochwasserrisikoabschätzung. Es werden neue Methoden und Modelle entwickelt, die die angesprochenen Zusammenhänge stärker berücksichtigen und auch die bestehenden Unsicherheiten der Modellergebnisse beziffern und somit die Verlässlichkeit der getroffenen Aussagen einordnen lassen. Dafür werden Daten zu Hochwasserereignissen aus verschiedenen Quellen erfasst und ausgewertet. Dazu zählen neben Niederschlags-und Durchflussaufzeichnungen an Messstationen beispielsweise auch Bilder aus sozialen Medien, die mit Ortsangaben und Bildinhalten helfen können, die Überflutungsflächen abzugrenzen und Hochwasserschäden zu schätzen. Verfahren des Maschinellen Lernens wurden erfolgreich eingesetzt, um aus vielfältigen Daten, Zusammenhänge zwischen Hochwasser und Auswirkungen zu erkennen, besser zu verstehen und verbesserte Modelle zu entwickeln. Solche Risikomodelle helfen bei der Entwicklung und Bewertung von Strategien zur Minderung des Hochwasserrisikos. Diese Werkzeuge ermöglichen darüber hinaus Einblicke in das Zusammenspiel verschiedener Faktoren sowie Aussagen zu den zu erwartenden Folgen auch von Hochwassern, die das bisher bekannte Ausmaß übersteigen. Diese Arbeit verzeichnet Fortschritte in Bezug auf eine verbesserte Bewertung von Hochwasserrisiken durch die Nutzung vielfältiger Daten aus unterschiedlichen Quellen mit innovativen Verfahren sowie der Weiterentwicklung von Modellen. Das Hochwasserrisiko unterliegt durch wirtschaftliche Entwicklungen und klimatische Veränderungen einem steten Wandel. Um das Wissen über Risiken aktuell zu halten sind robuste, leistungs- und anpassungsfähige Verfahren wie sie in dieser Arbeit vorgestellt werden von zunehmender Bedeutung.

Description: The Central Andean orogeny is caused by the subduction of the Nazca oceanic plate beneath the South-American continental plate. In Particular, the Southern Central Andes (SCA, 27°-40°S) are characterized by a strong N-S and E-W variation in the crustal deformation style and intensity. Despite being the surface geology relatively well known, the information on the deep structure of the upper plate in terms of its thickness and density configurations is still scarcely constrained. Previous seismic studies have focused on the crustal structure of the northern part of the SCA (~27°-33°S) based upon 2D cross-sections, while 3D crustal models centred on the South-American or the Nazca Plate have been published with lower resolution. To gain insight into the present-day state of the lithosphere in the area, we derived a 3D model that is consistent with both the available geological and seismic data and with the observed gravity field. The model consists on a continental plate with sediments, a two-layer crust and the lithospheric mantle being subducted by an oceanic plate. The model extension covers an area of 700 km x 1100 km, including the orogen, the forearc and the forelands.

Description: The Atacama Fault System (AFS) in N-Chile is a complex fault system with a variety of fault segments showing different degrees of activity. Initiated as a trench-linked fault system during the Jurassic it is now exposed in the Coastal Cordillera in the forearc of the Nazca-South America convergent plate margin. Fault scarps and surface ruptures indicate varying degrees of reactivation of this fault system that most likely roots into the subduction zone interface at the downdip end of coupling. Therefore, the interaction of these two systems is evident though not well understood. The active fault database for the northernmost segment of the Atacama Fault System (AFS) is the result of creating a comprehensive catalogue of active faults in the forearc to investigate activity patterns of the forearc in relation with megathrust segmentation and upper plate seismicity in the Coastal Cordillera of N-Chile (19°12’S - 25°12’S). The dataset has been compiled in Arc-GIS and is available as .mpk as well as .kmz formats to be visualised in Google Earth. The activity patterns are mapped according to a well-defined set of criteria (see below). The database for activity starts out from a thorough literature review and is supplemented by new evidences combining interpretation of remote sensing data, field work and upper plate seismicity from the Integrated Plate Boundary Observatory in Chile (IPOC) (Sippl et al., 2018) and a local seismic catalogues covering the area of the Salar Grande segment (Bloch et al., 2014). It also includes the available age data of offset geological units as references to bracket the chronology of fault activity. Fault activity for this study has been defined according to the Quaternary fault and fold database of the United States (https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-science_support_page_related_con=4#qt-science_support_page_related_con), but is subject to significant error due to slow slip rates (〈 0.2mm/yr), few chronologically constrained fault offsets and lack of historically or instrumentally observed earthquakes along the fault segments. Therefore, this database does not have the aim to serve as active fault database for seismic hazard assessment. It has been created with the clear aim to serve as database for general aspects of upper plate fault reactivation in relation with the megathrust seismic cycle and megathrust segmentation. This publication is part of an ongoing study investigating the interaction of megathrust segmentation with activity patterns in the overriding forearc.

Description: Response Spectrum Analysis (RSA), one of the most popular methods to carry out the seismic design of multi-degree-offreedom (MDOF) structures, is based on the concept of modal superposition, by which the uncoupled equations of motion that represent each mode of vibration of the system can be solved independently and the resulting responses superimposed by assuming linear elastic behaviour. Each mode is represented by a single-degree-of-freedom (SDOF) system, whose peak response is retrieved from response spectra deemed suitable for design. However, while modal superposition allows for the total response of a MDOF system to be determined by simple addition of the individual modal responses at each time step, combination of spectral values needs to take into account the fact that peak modal responses do not necessarily occur at the same time or along the same horizontal directions. These considerations give rise to the use of modal and spatial combination rules that aim to calculate the likely peak response of a MDOF system instead of conservatively carrying out an algebraic sum of maxima. Current design codes prescribe methodologies that were defined in the 1970s and 1980s, such as the Complete Quadratic Combination (CQC) [1], its three-dimensional extension CQC3 [2], the Square Root of the Sum of the Squares (SRSS) [3], or the 30% rules [4], based mostly on random vibration theory. However, access to large numbers of ground motion records at the present time allow us to revisit these approaches from a data-driven perspective, and investigate the relationship across the peaks of SDOF responses to seismic excitation at different orientations and at different points in time, with the ultimate goal of characterising this relationship in a fully probabilistic way. This paper presents results of a study of SDOF demands obtained considering 1,218 accelerograms from the RESORCE database [5], whose two horizontal perpendicular components were rotated around all non-redundant angles every 2° and applied to SDOF systems with periods of vibration of 0.2, 1.0 and 3.0 seconds, and sets of secondary systems with periods ranging from 0.5 through 0.95 times the three aforementioned periods. The concept of peak response was extended to include all peaks with amplitudes above two alternative thresholds of 80% and 95% of the maximum absolute response. Two main kinds of parameters were studied and are presented: (i) time differences between peaks of the same component and across perpendicular components, and (ii) ratios of instantaneous displacement demands between perpendicular components and the same component for different oscillator periods, as one of the components reaches a peak in the oscillator’s response. While results for the latter resemble the idea of the 0.3 coefficient from the 30% rule in average terms, the dispersion associated with all these parameters is large and should not be neglected.

Description: The relation between the response of an elastic single degree of freedom oscillator subject to seismic shaking and the seismological characteristics of the input waveforms represented in terms of the Fourier amplitude spectrum (FAS) has become a topic of growing interest in the engineering seismological community in recent years. As simulations of ground motions assume a greater prominence in engineering design and databases of both strong and weak motion records expand exponentially, the need to reconcile the influence of the controlling seismological properties of the motions with their potential impacts on structural response is becoming ever more important. Prediction of ground motion in the Fourier amplitude domain has several key advantages when compared to that of the response spectrum, namely a closer relationship to the physical seismological properties of the source, path and site that can be inferred from more abundant small magnitude and weak motion data, as well as maintained linearity of site response at all frequencies. Recognising this, new empirical ground motion models have been developed in terms of FAS [1, 2], in addition to an inter-frequency correlation model that can facilitate the definition of conditional spectrum compatible empirical and simulated ground motion records for design [3]. In spite of these advantages, the usage of FAS in seismic hazard and risk analysis remains limited to the scaling of simulated ground motions in the development of median ground motion models using random vibration theory (RVT). One major factor behind this is that translation from FAS to response spectra via RVT requires joint characterization not only of ground motions across a range of frequencies but also of strong motion duration. However, this limitation could potentially be overcome if fragility functions were to be derived directly in terms of FAS. It is for this purpose that a comparison is made in this paper between the efficiency of intensity measures based on the FAS and those based on conventional response spectra for a set of simple building fragility models of the type commonly used in seismic risk analysis. The feasibility of achieving end-to-end loss estimation exclusively in the Fourier amplitude domain is subsequently explored. While its full range of benefits and limitations will require further study, the potential for embedding seismological theory and data more deeply into engineering applications is appealing for the future practice of seismic design and risk analysis.

Description: Any strategy to change Carbon (C) pool would have a substantial effect on functionality of numerous ecosystem functions, detachment of Soil Organic Carbon (SOC), atmospheric carbon dioxide (CO2) concentration, and climate change mitigation. As the largest amount of the world’s C is stored in forests soils, the importance of forest SOC management is highlighted. Total SOC in forest varies not only laterally but also vertically with depth; however, the SOC storage of lower soil horizons have not been investigated enough despite their potential to frame our understanding of soil functioning. Visible–Near Infrared (vis–NIR) reflectance spectroscopy enables rapid examinations of the horizontal distribution of forest SOC, overcoming limitations of traditional soil assessment. This study aims to evaluate the potential of vis–NIR spectroscopy for characterizing the SOC contents of organic and mineral horizons in forests. We investigated 1080 forested sites across the Czech Republic at five individual soil layers, representing the Litter (L), Fragmented (F), and Humus (H) organic horizons, and the A1 (depth of 2–10 cm) and A2 (depth of 10–40 cm) mineral horizons (total 5400 samples). We then used Support Vector Machine (SVM) to model the SOC contents of (i) the profile (all organic and mineral horizons together), (ii) the combined organic horizons, (iii) the combined mineral horizons, and (iv) each individual horizon separately. The models were validated using 10-repeated 10-fold cross validation. Results showed that there was at least more than seven times as much SOC in the combined organic horizons compared to the combined mineral horizons with more variation in deeper layers. All individual horizons’ SOC was successfully predicted with low error and R2 values higher than 0.63; however, the prediction accuracy of F and A1 was greater compared to others (R2 〉 0.70 and very low-biased spatial estimates). We have shown that modelling of SOC with vis–NIR spectra in different soil horizons of highly heterogeneous forests of the Czech Republic is practical.

Description: Salt pans are highly dynamic environments that are difficult to study by in situ methods because of their harsh climatic conditions and large spatial areas. Remote sensing can help to elucidate their environmental dynamics and provide important constraints regarding their sedimentological, mineralogical, and hydrological evolution. This study utilizes spaceborne multitemporal multispectral optical data combined with spectral endmembers to document spatial distribution of surface crust types over time on the Omongwa pan located in the Namibian Kalahari. For this purpose, 49 surface samples were collected for spectral and mineralogical characterization during three field campaigns (2014–2016) reflecting different seasons and surface conditions of the salt pan. An approach was developed to allow the spatiotemporal analysis of the salt pan crust dynamics in a dense time-series consisting of 77 Landsat 8 cloud-free scenes between 2014 and 2017, covering at least three major wet–dry cycles. The established spectral analysis technique Sequential Maximum Angle Convex Cone (SMACC) extraction method was used to derive image endmembers from the Landsat time-series stack. Evaluation of the extracted endmember set revealed that the multispectral data allowed the differentiation of four endmembers associated with mineralogical mixtures of the crust’s composition in dry conditions and three endmembers associated with flooded or muddy pan conditions. The dry crust endmember spectra have been identified in relation to visible, near infrared, and short-wave infrared (VNIR–SWIR) spectroscopy and X-ray diffraction (XRD) analyses of the collected surface samples. According these results, the spectral endmembers are interpreted as efflorescent halite crust, mixed halite–gypsum crust, mixed calcite quartz sepiolite crust, and gypsum crust. For each Landsat scene the spatial distribution of these crust types was mapped with the Spectral Angle Mapper (SAM) method and significant spatiotemporal dynamics of the major surface crust types were observed. Further, the surface crust dynamics were analyzed in comparison with the pan’s moisture regime and other climatic parameters. The results show that the crust dynamics are mainly driven by flooding events in the wet season, but are also influenced by temperature and aeolian activity in the dry season. The approach utilized in this study combines the advantages of multitemporal satellite data for temporal event characterization with advantages from hyperspectral methods for the image and ground data analyses that allow improved mineralogical differentiation and characterization.

Description: The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.

Description: A coherence-based earthquake detection technique was applied to continuous (1 year) waveform data recorded along the Irpinia fault system (Southern Italy). The earthquake detection was performed using coherent P- and S-wave arrivals recorded by the dense seismic network operating in Irpinia and assuming a local velocity model. We applied a strategy to simultaneously detect and locate earthquakes and to discriminate among true and false detections using an automated and fast procedure, able to process 1 year of data in ~ 1.75 days. The final catalogue of automatically retrieved earthquakes shows a performance improvement with respect to the standard monitoring practices, with an increase in the number of detected small events of about a factor three with respect to the automatic Earth-worm Binder implemented in ISNet and decreases in completeness magnitude of almost half unit magnitude.

Description: Interest in small-to-medium magnitude earthquakes and their potential consequences has increased significantly in recent years, mostly due to the occurrence of some unusually damaging small events, the development of seismic risk assessment methodologies for existing building stock, and the recognition of the potential risk of induced seismicity. As part of a clear ongoing effort of the earthquake engineering community to develop knowledge on the risk posed by smaller events, a global database of earthquakes with moment magnitudes in the range from 4.0 to 5.5 for which damage and/or casualties have been reported has been compiled and is made publicly available. The two main purposes were to facilitate studies on the potential for earthquakes in this magnitude range to cause material damage and to carry out a statistical study to characterise the frequency with which earthquakes of this size cause damage and/or casualties (published separately). The present paper describes the data sources and process followed for the compilation of the database, while providing critical discussions on the challenges encountered and decisions made, which are of relevance for its interpretation and use. The geographic, temporal, and magnitude distributions of the 1958 earthquakes that make up the database are presented alongside the general statistics on damage and casualties, noting that these stem from a variety of sources of differing reliability. Despite its inherent limitations, we believe it is an important contribution to the understanding of the extent of the consequences that may arise from earthquakes in the magnitude range of study.

Description: Over the last 15 years, the Gravity Recovery and Climate Experiment (GRACE) mission has provided measurements of temporal changes in mass redistribution at and within the Earth that affect polar motion. The newest generation of GRACE temporal models, are evaluated by conversion into the equatorial components of hydrological polar motion excitation and compared with the residuals of observed polar motion excitation derived from geodetic measurements of the pole coordinates. We analyze temporal variations of hydrological excitation series and decompose them into linear trends and seasonal and non-seasonal changes, with a particular focus on the spectral bands with periods of 1000–3000, 450–1000, 100–450, and 60–100 days. Hydrological and reduced geodetic excitation series are also analyzed in four separated time periods which are characterized by different accuracy of GRACE measurements. The level of agreement between hydrological and reduced geodetic excitation depends on the frequency band considered and is highest for interannual changes with periods of 1000–3000 days. We find that the CSR RL06, ITSG 2018 and CNES RL04 GRACE solutions provide the best agreement with reduced geodetic excitation for most of the oscillations investigated.

Description: Basin modeling in structurally complex areas involves several difficulties associated with its geometric and thermal history approaches. There have been multiple developments concerning the structural geometry in doing three-dimensional (3-D) basin modeling in these settings. However, their applicability is limited because most of these improvements require 3-D structural restorations, which is an input that is not always available at basin scale. Although a traditional basin model using backstripping could give a faster overview of the petroleum system elements, it is an alternative method that may distort the structural evolution and, consequently, the petroleum potential evaluation. Equally important are the thermal history uncertainties in these environments, where several factors disturb the thermal regime. Despite these difficulties, traditional 3-D basin modeling could be a reliable tool when we are able to understand the geometric and thermal histories and implement the proper adjustments. We propose alternative methods to tackle common problems when building 3-D basin models, and we demonstrate their validity with an example in the Middle Magdalena Valley, Colombia. This hydrocarbon province located in the northern Andes corresponds to an intermountain basin that has undergone a complex evolution. Its structural configuration represents a modeling challenge by means of the backstripping method. Additionally, a high variability exists in the present-day basal heat flow related to its structural evolution. The result of our model not only fits the calibration data, but also reflects the geological processes better. The proposed methodology intends to aid basin modelers in providing additional options when modeling in structurally deformed basins.

Description: Paleomagnetic, magnetic fabric and rock magnetic studies were carried out in the late Middle to early Late Cambrian Campanario Formation exposed in NW Argentina. The study also presents preliminary results from the Early Cambrian metasediments of the Puncoviscana Formation and from Mojotoro intrusive. A new paleomagnetic pole, C2, was computed for the Campanario Formation (23.6°N, 346.5°E, A95, 7.0°, N: 11 sites) from the localities of Tilcara (T), Terma de Reyes (R) and El Perchel (EP), including previous data from Santa Victoria Oeste (M), in northernmost Argentina. A positive fold test was obtained for Tilcara locality while a positive regional tilt test was obtained for mean site directions for the four localities. This pole can be considered as the representative pole position for the Pampia terrane for the late Middle to Late Cambrian. Previous paleomagnetic data for the same formation from the Iruya-Matancillas locality show an in situ clockwise rotation of about 30° around a vertical axis when compared with the mean Pampia pole. The same is observed when comparing the early Ordovician pole for the Santa Rosita Formation at those localities with the recently obtained coeval pole of the La Pedrera Formation, indicating that local tectonic rotations, affected that area. These results suggest that previous paleomagnetic interpretations for these Late Cambrian and Early Ordovician rocks in the region as recording displacement of the Pampia terrane in Cambrian times are probably incorrect. Additionally, two virtual geomagnetic poles were computed for the Puncoviscana Formation (TP1: 34.5°N, 52.3°E, A95: 5.0°, n: 22 specimens and TP2: 38.3°N, 33.6°E, A95: 5.7°, n: 14 specimens) and one for the Mojotoro Intrusive (MO: 9.1°N, 345.6°E, A95: 16.4°, n: 11 specimens). These and previous Early Cambrian paleomagnetic data from the Pampia terrane differ from Gondwana coeval reference directions in inclination and/or declination, lacking a simple pattern.

Description: The convergence between the Indian and Eurasian plates has produced the thick crust and uplifted the Tibetan plateau since about 50 Ma. However, the deformation of the mantle lithosphere is still a puzzle. The geometry of the subducting Indian mantle lithosphere beneath the plateau and the thickening or/and delamination of the Tibetan mantle lithosphere are the keys for understanding the continental collision process and the evolution of the plateau. However, knowledge has been restricted due to sparse data coverage in Tibet. In this study, S-wave receiver functions are calculated using tele-seismic waveforms recorded by two broadband arrays in central Tibet to image the lithospheric structure, mainly the depth variation of the lithosphere-asthenosphere boundary (LAB). Our results show that the depth of the Tibetan LAB decreases from ∼150 km in the west to ∼120 km in the east across the north-south trending Yadong-Gulu rift. Similarly, the LAB depth of the subducting Indian slab decreases from ∼270 km in the west to ∼200 km in the east, and the northernmost subducting Indian slab can be observed beneath the Bangong-Nujiang suture. These observations suggest that the thickness of the Tibetan lithosphere and the depth of the underlying Indian slab are segmented across the Yadong-Gulu rift in different degrees. The abrupt changes imply that the subducting Indian slab has been torn, which provided an upwelling channel for the asthenosphere contributing to the development of the rift.

Description: Varved lake sediments provide climatic records with seasonal to annual resolution and low associated age uncertainty. Robust and detailed comparison of well-dated and annually laminated sediment records is crucial for reconstructing abrupt and regionally time-transgressive changes as well as validation of spatial and temporal trajectories of past climatic changes. The VARved sediments DAtabase (VARDA) presented here is the first data compilation for varve chronologies and associated palaeoclimatic proxy records. The current version 1.0 allows detailed comparison of published varve records from 95 lakes. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. VARDA additionally provides a technical environment that enables us to explore the database of varved lake sediments using a connected data model and can generate a state-of-the-art graphic representation of a multisite comparison. This allows the reassessment of existing chronologies and tephra events to synchronize and compare even distant varved lake records. Furthermore, the present version of VARDA permits the exploration of varve thickness data. In this paper, we report in detail on the data-mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies, as well as the technical infrastructure of the database. Additional palaeoclimatic proxy data will be provided in forthcoming updates. The VARDA graph database and user interface can be accessed online at https://varve.gfz-potsdam.de (last access: 15 September 2020), all datasets of version 1.0 are available at https://doi.org/10.5880/GFZ.4.3.2019.003 (Ramisch et al., 2019).

Description: Private precautionary measures play an increasingly important role in flood risk management. The degree to which private precautionary measures mitigate flood risk depends mainly on the type of measure (and how effective it is) and how frequently and successfully it is implemented. These aspects are influenced by a complex interaction of physical and socio-economic processes, which makes the assessment and the prediction of the mitigation of flood risk via private precautionary measures a challenge. This paper provides an overview of factors and processes that influence the implementation and effectiveness of private precaution in mitigating flood risk, underpinning it with highlights from international examples. We recommend private precautionary measures for further use to improve flood risk mitigation, but stress that they need to be considered and implemented through a holistic systems approach to maximize their effectiveness

Description: Climate conditions in Africa have varied substantially during the Late Quaternary with alternating humid and arid periods controlled mainly by the African monsoonal regime. However, the duration and termination of the last African Humid Period (14–6 ka BP) and its internal climatic variability are still debated. Using a laminated sequence from the Nile Deep-Sea Fan, we reconstruct for the first time the monsoon-induced frequency of exceptional Nile floods at centennial resolution during the African Humid Period. By combining sedimentological, geochemical and microscopic tools and comparing our record with two proximal piston cores and with regional paleoclimatic records, we show: a) the occurrence of recurrent high-energy floods between 10.1 and 9 ka BP, during the height of the African Humid Period; b) a shift in the hydro-climatic regime as early as 9 ka BP, with a progressive reduction in flood frequency and magnitude until 8.2 ka BP, likely related to a southward migration of the monsoon rainfall belt; c) a drastic reduction of flood activity between 8.2 and 7.8 ka BP; d) an unstable Ethiopian-Nile hydrological system from 7.8 ka BP, followed by a further decrease in river runoff until ∼4 ka BP. The occurrence of a stepwise hydro-climatic deterioration over the Ethiopian Highlands from ∼9 ka BP brings into question the climatic linkages and feedbacks between low and high latitudes during the Early to Mid-Holocene and in particular around the 8.2 ka BP North Atlantic cooling event. Our unique record of flood frequency at centennial-resolution therefore allows us to draw new insights on fluvial and geomorphic feedbacks of the Nile hydrologic system to monsoonal regimes during a period of major environmental shifts.

Description: Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. To determine the related injectivity decline over time, the spatial precipitation distribution in the subsurface near the injection well is assessed by modelling barite growth kinetics in a radially diverging Darcy flow domain. Flow and reservoir properties as well as fluid chemistry are chosen to represent reservoirs subject to geothermal exploration located in the North German Basin (NGB) and the Upper Rhine Graben (URG) in Germany. Fluids encountered at similar depths are hotter in the URG, while they are more saline in the NGB. The associated scaling amount normalised to flow rate is similar for both regions. The predicted injectivity decline after 10 years, on the other hand, is far greater for the NGB (64%) compared to the URG (24%), due to the temperature- and salinity-dependent precipitation rate. The systems in the NGB are at higher risk. Finally, a lightweight score is developed for approximating the injectivity loss using the Damköhler number, flow rate and total barite scaling potential. This formula can be easily applied to geothermal installations without running complex reactive transport simulations.

Description: Elastic moduli derived from vertical seismic profiles (VSPs) and 2-D SH-wave reflection seismic profiles are used to characterize mechanical properties of rocks in sinkhole areas. VP and VS were used to calculate the Poisson’s ratio and the dynamic shear modulus. The study shows that 2-D shear wave reflection seismics is suited to depict the heterogeneities of the subsurface induced by subsurface erosion. Low shear wave velocities of ca. 120–350 m s–1 and low shear strength values between 25 and 250 MPa are identified for the subsurface erosion horizon that consists of soluble Permian evapourites and the disturbed overlying deposits. These low values are a result of cavities and fractures induced by dissolution, creating unstable zones. In compliance with the shear modulus the Poisson’s ratio derived from the VSPs shows values of 0.38–0.48 for both the presumed subsurface erosion horizon, and the deposits above. This is a further indicator of reduced underground stability. In the VSPs, anomalies of the shear modulus and the Poisson’s ratio correlate with low electrical resistivities of less than 10 Ωm from borehole logs, indicating high conductivity due to fluid content. Further investigation reveals a conversion of S-to-P wave for the subsurface erosion horizon, which is probably the result of dipping layers and an oriented fracture network. Seismic attribute analysis of the 2-D sections shows strong attenuation of high frequencies and low similarity of adjacent traces, which correlate with the degree of subsurface erosion induced wave disturbance of the underground.

Description: Airborne and orbital imaging spectroscopy can facilitate the quantification of chemical and physical attributes of surface materials through analysis of spectral signatures. Prior to analysis, estimates of surface reflectance must be inferred from radiance measurements in a process known as atmospheric correction, which compensates for the distortion of the electromagnetic signal by the atmosphere. Inaccuracies in the correction process can alter characteristic spectral signatures, leading to subsequent mischaracterization of surface properties. Global observations pose new challenges for mapping surface composition, as varied atmospheric conditions and surface biomes challenge traditional atmospheric correction methods. Recent work adopted an optimal estimation (OE) approach for retrieving surface reflectance from observed radiance measurements, providing the reflectance estimates with a posterior probability. This work incorporates these input probabilities to improve the accuracy of surface feature measurements. We demonstrate this using a generic feature-fitting method that is applicable to a wide range of Earth surface studies including geology, ecosystem studies, hydrology and urban studies. Specifically, we use a probabilistic framework based on generalized Tikhonov-regularized least squares, a rigorous formulation for appropriate weighting of features by their observation uncertainty and leveraging of prior knowledge of material abundance for improving estimation accuracy. We demonstrate the validity of this procedure and quantify the increase in model performance by simulating expected accuracies in the reflectance estimation. To evaluate global uncertainties in mineral estimation, we simulate observations representative of the expected global range of atmospheric water vapor and aerosol levels, and characterize the sensitivity of our procedure to those quantities.

Description: Earthquake moment tensors in eastern Pacific (ePac) slabs typically show downdip tensional (DT) axes, whereas in the western Pacific (wPac), they typically show downdip compressional (DC) axes or have mixed orientations indicative of unbending. Prevailing conceptual models emphasize uniform stress/deformation modes, that is, bulk slab stretching or shortening, as the dominant control on intermediate depth seismic expression. In contrast, we propose that a diversity of seismic expression, including DT‐ and DC‐dominated regions, is consistent with expectations of flexural strain accumulation, based on systemic differences in slab geometry. Our analysis reveals two largely unrecognized features of ePac intraslab seismicity. First, earthquake clusters consistent with slab unbending are present in ePac slabs, albeit at much shallower depths than typical of wPac slabs. Second, intermediate depth ePac DT seismicity is strongly localized to the upper half of zones undergoing curvature increase, such as flat slab segments. Our study highlights how the seismic expression of slab flexure is impacted by the relative contribution of brittle and ductile deformation. The strongly asymmetric temperature structure that is preserved in sinking slabs means that seismicity disproportionately records the deformation regime in the colder part of the slab, above the neutral plane of bending. The expression of in‐plane stress may be discernible in terms of a systematic modifying effect on the seismic expression of flexure.

Description: Lacustrine sediments are important archives for high resolution palaeoenvironmental reconstructions of the Holocene. Despite the density of ancient cities and settlements along the western coast of Turkey, the archives from coastal lakes in this area have until now not been recognized to their fullest potential and are, therefore, only poorly studied. The exceptional geo-bio-archive of Lake Belevi is located close to the ancient city of Ephesos in western Turkey. Two sediment cores have been analysed using geochemical, sedimentological, microfaunal, palynological, and archaeoparasitological methods. The in-depth study of these Holocene deposits is supported by a robust age-depth model that used 33 radiocarbon dates and tephrochronology. The results reveal the existence of a freshwater lake in the Early Holocene which turned brackish when the rising sea level connected it with the sea. The delta evolution of the Küçük Menderes led to the re-establishment of a freshwater lake. The natural vegetation was represented by open oak woodlands. There are hints for first agricultural activities in the environs of Belevi as early as 8000 cal yr BP. Intensive cultivation of Olea is proven since 3000 cal yr BP. Starting during the 3rd millennium BP, the human impact with enhanced deforestation activities and correlative high sedimentation rates is attested for sites such as Belevi (Ephesos), Elaia (Pergamon) and Miletos. For the first time, tephra from the eruption of Minoan Santorini has been identified in the environs of Ephesos. This ash covered the vegetation by a thick layer, wherefore low-growing plants were strongly affected. The comparison between the results from the quasi natural area of Lake Belevi and the area around the city of Ephesos gives insights into the development and use of the landscapes, the environmental changes as well as the duration and intensity of the human impact.

Description: Soil degradation is a major threat for European soils and therefore, the European Commission recommends intensifying research on soil monitoring to capture changes over time and space. Imaging spectroscopy is a promising technique to create spatially accurate topsoil maps based on hyperspectral remote sensing data. We tested the application of a local partial least squares regression (PLSR) to airborne HySpex and simulated satellite EnMAP (Environmental Mapping and Analysis Program) data acquired in north-eastern Germany to quantify the soil organic carbon (SOC) content. The approach consists of two steps: (i) the local PLSR uses the European LUCAS (land use/cover area frame statistical survey) Soil database to quantify the SOC content for soil samples from the study site in order to avoid the need for wet chemistry analyses, and subsequently (ii) a remote sensing model is calibrated based on the local PLSR SOC results and the corresponding image spectra. This two-step approach is compared to a traditional PLSR approach using measured SOC contents from local samples. The prediction accuracy is high for the laboratory model in the first step with R2 = 0.86 and RPD = 2.77. The HySpex airborne prediction accuracy of the traditional approach is high and slightly superior to the two-step approach (traditional: R2 = 0.78, RPD = 2.19; two-step: R2 = 0.67, RPD = 1.79). Applying the two-step approach to simulated EnMAP imagery leads to a lower but still reasonable prediction accuracy (traditional: R2 = 0.77, RPD = 2.15; two-step: R2 = 0.48, RPD = 1.41). The two-step models of both sensors were applied to all bare soils of the respective images to produce SOC maps. This local PLSR approach, based on large scale soil spectral libraries, demonstrates an alternative to SOC measurements from wet chemistry of local soil samples. It could allow for repeated inexpensive SOC mapping based on satellite remote sensing data as long as spectral measurements of a few local samples are available for model calibration.

Description: In the presented work, the spectral emissivity of basaltic melts at magmatic temperatures was retrieved in a laboratory-controlled experiment by measuring their spectral radiance. Granulated bombs of Etnean basalts were melted and the radiant energy from the melting surface was recorded by a portable spectroradiometer in the short wavelength infrared (SWIR) spectral range between 1500 and 2500 nm. The Draping algorithm, an improved algorithm for temperature and emissivity separation, was applied for the first time to SWIR hyperspectral data in order to take into account the non-uniform temperature distribution of the melt surface and, at the same time, solving the two temperatures and the spectral emissivity. The results have been validated by comparing our results with the emissivity measured at a "lava simulator". Basalt spectral emissivity does not vary significantly at magmatic temperature, but shows an absorption feature in the range 2180–2290 nm, an atmospheric window pivotal for the IR remote sensing of active volcanoes.

Description: The hydro- and morphodynamic processes within the Vietnamese Mekong Delta are heavily impacted by human activity, which in turn affects the livelihood of millions of people. The main drivers that could impact future developments within the delta are local stressors like hydropower development and sand mining, but also global challenges like climate change and relative sea level rise. Within this study, a hydro-morphodynamic model was developed, which focused on a stretch of the Tien River and was nested into a well-calibrated model of the delta’s hydrodynamics. Multiple scenarios were developed in order to assess the projected impacts of the different drivers on the river’s morphodynamics. Simulations were carried out for a baseline scenario (2000–2010) and for a set of plausible scenarios for a future period (2050–2060). The results for the baseline scenario indicate that the Tien River is already subject to substantial erosion under present-day conditions. For the future period, hydropower development has the highest impact on the local erosion and deposition budget, thus amplifying erosional processes, followed by an increase in sand mining activity and climate change-related variations in discharge. The results also indicate that relative sea level rise only has a minimal impact on the local morphodynamics of this river stretch, while erosional tendencies are slowed by a complete prohibition of sand mining activity. In the future, an unfavourable combination of drivers could increase the local imbalance between erosion and deposition by up to 89%, while the bed level could be incised by an additional 146%.

Description: The hemlock woolly adelgid (HWA; Adelges tsugae) is an invasive insect infestation that is spreading into the forests of the northeastern United States, driven by the warmer winter temperatures associated with climate change. The initial stages of this disturbance are difficult to detect with passive optical remote sensing, since the insect often causes its host species, eastern hemlock trees (Tsuga canadensis), to defoliate in the midstory and understory before showing impacts in the overstory. New active remote sensing technologies—such as the recently launched NASA Global Ecosystem Dynamics Investigation (GEDI) spaceborne lidar—can address this limitation by penetrating canopy gaps and recording lower canopy structural changes. This study explores new opportunities for monitoring the HWA infestation with airborne lidar scanning (ALS) and GEDI spaceborne lidar data. GEDI waveforms were simulated using airborne lidar datasets from an HWA-infested forest plot at the Harvard Forest ForestGEO site in central Massachusetts. Two airborne lidar instruments, the NASA G-LiHT and the NEON AOP, overflew the site in 2012 and 2016. GEDI waveforms were simulated from each airborne lidar dataset, and the change in waveform metrics from 2012 to 2016 was compared to field-derived hemlock mortality at the ForestGEO site. Hemlock plots were shown to be undergoing dynamic changes as a result of the HWA infestation, losing substantial plant area in the middle canopy, while still growing in the upper canopy. Changes in midstory plant area (PAI 11–12 m above ground) and overall canopy permeability (indicated by RH10) accounted for 60% of the variation in hemlock mortality in a logistic regression model. The robustness of these structure-condition relationships held even when simulated waveforms were treated as real GEDI data with added noise and sparse spatial coverage. These results show promise for future disturbance monitoring studies with ALS and GEDI lidar data.

Description: The combination of two well-established methods, of quadrocopter-borne air sampling and methane isotopic analyses, is applied to determine the source process of methane at different altitudes and to study mixing processes. A proof-of-concept study was performed to demonstrate the capabilities of quadrocopter air sampling for subsequently analysing the methane isotopic composition δ13C in the laboratory. The advantage of the system compared to classical sampling on the ground and at tall towers is the flexibility concerning sampling location, and in particular the flexible choice of sampling altitude, allowing the study of the layering and mixing of air masses with potentially different spatial origin of air masses and methane. Boundary layer mixing processes and the methane isotopic composition were studied at Polder Zarnekow in Mecklenburg–West Pomerania in the north-east of Germany, which has become a strong source of biogenically produced methane after rewetting the drained and degraded peatland. Methane fluxes are measured continuously at the site. They show high emissions from May to September, and a strong diurnal variability. For two case studies on 23 May and 5 September 2018, vertical profiles of temperature and humidity were recorded up to an altitude of 650 and 1000 m, respectively, during the morning transition. Air samples were taken at different altitudes and analysed in the laboratory for methane isotopic composition. The values showed a different isotopic composition in the vertical distribution during stable conditions in the morning (delta values of −51.5 ‰ below the temperature inversion at an altitude of 150 m on 23 May 2018 and at an altitude of 50 m on 5 September 2018, delta values of −50.1 ‰ above). After the onset of turbulent mixing, the isotopic composition was the same throughout the vertical column with a mean delta value of −49.9 ± 0.45 ‰. The systematically more negative delta values occurred only as long as the nocturnal temperature inversion was present. During the September study, water samples were analysed as well for methane concentration and isotopic composition in order to provide a link between surface and atmosphere. The water samples reveal high variability on horizontal scales of a few tens of metres for this particular case. The airborne sampling system and consecutive analysis chain were shown to provide reliable and reproducible results for two samples obtained simultaneously. The method presents a powerful tool for distinguishing the source process of methane at different altitudes. The isotopic composition showed clearly depleted delta values directly above a biological methane source when vertical mixing was hampered by a temperature inversion, and different delta values above, where the air masses originate from a different footprint area. The vertical distribution of methane isotopic composition can serve as tracer for mixing processes of methane within the atmospheric boundary layer.

Description: In this study, we investigate the regional tectonic impact on salt movement at the northeastern margin of the intracontinental North German Basin. We discuss the evolution of salt pillows in the Bay of Mecklenburg in the light of thick‐ and thin‐skinned tectonics, including gravity gliding, and differential loading using seismic imaging. Stratigraphic and structural interpretation of a 170 km long, multichannel seismic line, extending from the Bay of Mecklenburg to northeast of Rügen Island, incorporates well information of nearby onshore wells. This new high‐resolution seismic line completely images the stratigraphic and tectonic pattern of the subsurface, from the base of the Zechstein to the seafloor. Our analysis reveals that subsidence during Late Triassic to Early Cretaceous at the northeastern basin margin was associated with transtensional dextral strike slip movement within the Trans‐European Suture Zone. We reinterpret the Werre and Prerow Fault Zones west of Rügen Island as an inverted, thin‐skinned normal fault system associated with the formation of the Western Pomeranian Fault System. Salt movement in the Bay of Mecklenburg was initiated in the Late Triassic and lasted until the Early Jurassic. A second phase of salt pillow growth occurred during the Coniacian until Cenozoic and correlates with compression‐related regional basin inversion due to the onset of the Africa‐Iberia‐Europe convergence. Thin‐skinned extensional initialization of salt pillow growth and compressional salt remobilization explains salt pillow evolution in the Bay of Mecklenburg. Additionally, we discuss an impact of gravity gliding on salt pillow evolution induced by basin margin tilt.

Description: Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.

Description: Free traveling Rossby wave normal modes (RNMs) are often investigated through large‐scale space‐time spectral analyses, which therefore is subject to observational availability, especially in the mesosphere. Ground‐based mesospheric observations were broadly used to identify RNMs mostly according to the periods of RNMs without resolving their horizontal scales. The current study diagnoses zonal wave numbers of RNM‐like oscillations occurring in mesospheric winds observed by two meteor radars at about 79°N. We explore four winters comprising the major stratospheric sudden warming events (SSWs) 2009, 2010, and 2013. Diagnosed are predominant oscillations at the periods of 10 and 16 days lasting mostly for three to five whole cycles. All dominant oscillations are associated with westward zonal wave number m =1, excepting one 16‐day oscillation associated with m =2. We discuss the m =1 oscillations as transient RNMs and the m =2 oscillation as a secondary wave of nonlinear interaction between an RNM and a stationary Rossby wave. All the oscillations occur around onsets of the three SSWs, suggesting associations between RNMs and SSWs. For comparison, we also explore the wind collected by a similar network at 54°N during 2012–2016. Explored is a manifestation of 5‐day wave, namely, an oscillation at 5–7 days with m =1), around the onset of SSW 2013, supporting the associations between RNMs and SSWs.

Description: Hydro‐fracturing is a routine industrial technique whose safety depends on fractures remaining confined within the target rock volume. Both observations and theoretical models show that, if the fluid volume is larger than a critical value, pockets of fluid can propagate large distances in the Earth's crust in a self‐sustained, uncontrolled manner. Existing models for such critical volumes are unsatisfactory, most are two‐dimensional and depend on poorly constrained parameters (typically the fracture length). Here we derive both analytically and numerically in three dimensions scale‐independent critical volumes as a function of only rock and fluid properties. We apply our model to gas, water and magma injections in laboratory, industrial and natural settings, showing that our critical volumes are consistent with observations and can be used as conservative estimates. We discuss competing mechanisms promoting fracture arrest, whose quantitative study could help to assess more comprehensively the safety of hydro‐fracturing operations.

Description: Monitoring soil moisture is still a challenge: it varies strongly in space and time and at various scales while conventional sensors typically suffer from small spatial support. With a sensor footprint up to several hectares, cosmic-ray neutron sensing (CRNS) is a modern technology to address that challenge. So far, the CRNS method has typically been applied with single sensors or in sparse national-scale networks. This study presents, for the first time, a dense network of 24 CRNS stations that covered, from May to July 2019, an area of just 1 km2: the pre-Alpine Rott headwater catchment in Southern Germany, which is characterized by strong soil moisture gradients in a heterogeneous landscape with forests and grasslands. With substantially overlapping sensor footprints, this network was designed to study root-zone soil moisture dynamics at the catchment scale. The observations of the dense CRNS network were complemented by extensive measurements that allow users to study soil moisture variability at various spatial scales: roving (mobile) CRNS units, remotely sensed thermal images from unmanned areal systems (UASs), permanent and temporary wireless sensor networks, profile probes, and comprehensive manual soil sampling. Since neutron counts are also affected by hydrogen pools other than soil moisture, vegetation biomass was monitored in forest and grassland patches, as well as meteorological variables; discharge and groundwater tables were recorded to support hydrological modeling experiments. As a result, we provide a unique and comprehensive data set to several research communities: to those who investigate the retrieval of soil moisture from cosmic-ray neutron sensing, to those who study the variability of soil moisture at different spatiotemporal scales, and to those who intend to better understand the role of root-zone soil moisture dynamics in the context of catchment and groundwater hydrology, as well as land–atmosphere exchange processes. The data set is available through the EUDAT Collaborative Data Infrastructure and is split into two subsets: https://doi.org/10.23728/b2share.282675586fb94f44ab2fd09da0856883 (Fersch et al., 2020a) and https://doi.org/10.23728/b2share.bd89f066c26a4507ad654e994153358b (Fersch et al., 2020b).

Description: Electrically charged particles are trapped by the Earth’s magnetic field, forming the Van Allen radiation belts. Observations show that electrons in this region can have energies in excess of 7 MeV. However, whether electrons at these ultra-relativistic energies are locally accelerated, arise from betatron and Fermi acceleration due to transport across the magnetic field, or if a combination of both mechanisms is required, has remained an unanswered question in radiation belt physics. Here, we present a unique way of analyzing satellite observations which demonstrates that local acceleration is capable of heating electrons up to 7 MeV. By considering the evolution of phase space density peaks in magnetic coordinate space, we observe distinct signatures of local acceleration and the subsequent outward radial diffusion of ultra-relativistic electron populations. The results have important implications for understanding the origin of ultra-relativistic electrons in Earth’s radiation belts, as well as in magnetized plasmas throughout the solar system.

Description: Various styles of ore deposits may form from a single magmatic-hydrothermal system. Identification of a possible genetic link between different ore types in a region is not only of critical importance for a better understanding of the magmatic-hydrothermal processes, but can also help in successful mineral exploration. Both iron oxide-apatite (IOA) and iron skarn deposits are closely associated with intrusive rocks of intermediate to felsic in composition, but whether these two ore types can form from the same magmatic intrusion remains poorly understood. In this study, we present a comparative study between a newly identified subsurface IOA ore body located at the apex of a diorite porphyry and the iron skarn ore bodies located immediately above it in the Jinniu volcanic basin of the Daye district, Middle-Lower Yangtze River metallogenetic belt (MLYRMB), eastern China in order to highlight a genetic link between these two styles of mineralization. The IOA ores are dominated by Ti-rich magnetite with variable amounts of fluorapatite, diopside, and actinolite. This mineralogical assemblage is distinctly different from the iron skarn ores, which consist mainly of Ti-depleted magnetite and subordinate pre-ore garnet and diopside, and post-ore quartz, chlorite, calcite, and pyrite. In addition, magnetite from the IOA ores is characterized by well-developed ilmenite lamellae and has high concentrations of Ni, V, Co, and Ga, consistent with high temperature crystallization, whereas magnetite grains from the iron skarn ores usually exhibit oscillatory growth zones and contain much lower Ni, V, Co, and Ga, indicating their formation under relatively low temperatures. Titanite and fluorapatite from the IOA ores have U-Pb ages of 132.5 ± 2.4 Ma to 128.4 ± 3.0 Ma, which match a titanite U-Pb age for the associated iron skarn ores (132.3 ± 2.0 Ma), and are consistent with zircon U-Pb ages for the ore-hosting diorite porphyry (130.4 ± 0.7 Ma to 130.3 ± 0.5 Ma). This age consistency supports a possible genetic link among the diorite porphyry, IOA ores, and iron skarn ores. We propose that the IOA and skarn ores are the products of two consecutive mineralization stages of the same magmatic-hydrothermal system, involving a high-temperature, hypersaline fluid coexisting with the diorite porphyry magma during emplacement and a subsequent low temperature, diluted hydrothermal fluid. Other IOA and iron skarn deposits of similar ages (130 Ma) are found in a series of volcanic basins in the MLYRMB, which forms one of the world’s largest IOA metallogenic belts. The close association of the two ore styles identified at Daye provides a useful exploration guide for IOA and iron skarn deposits both on a local and regional scale.

Description: Undifferentiated meteorites, like primitive chondrites, can contain presolar and solar nebula materials which would provide information about the origin and initial conditions of the solar system, whereas differentiated meteorites like iron meteorites, can show early phases of planetary accretion. They also provide the possibility to receive information about core properties and planetary bodies. In addition to the gain in such fundamental scientific knowledge both types are of interest for the exploration of critical raw materials (CRMs) and precious elements. The Santa Rosa de Viterbo meteorite shower, discovered 1810 in the Boyacá province of Colombia, represents a typical iron-nickel meteorite. The present study presents new structural, textural and geochemical results of one fragment of this meteorite, using reflecting microscopy, electron probe micro analyses (EPMA) and electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The present study presents trace element concentrations of the meteorite's minerals for the first time. The sample is dominated by kamacite (α-FeNi). Schreibersite (FeNi3P), taenite (γ-FeNi) and plessite (mixture of kamacite and taenite) are minor constituents. The occurrence of cohenite ((Fe,Ni,Co)3C) and troilite (FeS) are likely. The meteorite sample contains classical Neuman bands passing through kamacite and frequent Widmanstätten pattern. The bandwidth of kamacite defines the meteorite as finest octahedrite. Geochemically, it is characterized as a “Type IC meteorite”. While improving the characterization and classification of the Santa Rosa de Viterbo Iron Meteorite, notable concentrations of Au (〉400 ppm) and Ge (〉230 ppm) alongside major elements such as Fe, Ni and Co in the bulk composition of that meteorite, were proven. Major and rock-forming minerals such as kamacite and taenite incorporate hundreds of ppm of Ge whereas schreibersite, itself a minor component in that particular meteorite, is the major source for Au (〉1400 ppm). In kamacite and taenite also Ir, Pd and Ga were found in minor amounts. Nano-scale inclusions or atomic clusters called nano-nuggets may have been responsible for the high concentrations of Au, Ir, Pd and Ga. Raman and Laser-induced plasma spectroscopes installed in in space probes seems suitable exploration methods for Fe–Ni meteorites, containing Ni-concentrations 〉 5.8 wt% defining the meteorite as octaedrites.

Description: Northern lakes are considered a major source of atmospheric methane (CH4), a potent GHG1,2. However, large uncertainties in their emissions (7–26 Tg CH4 yr–1; ref. 2) arise from challenges in upscaling field data, including fluxes by ebullition (bubbling), the dominant emission pathway2. Remote sensing of ebullition would allow detailed mapping of regional emissions but has hitherto not been developed. Here, we show that lake ebullition can be imaged using synthetic aperture radar remote sensing during ice-cover periods by exploiting the effect of ebullition on the texture of the ice–water interface. Applying this method to five Alaska regions and combining spatial remote sensing information with year-round bubble-trap flux measurements, we create ebullition-flux maps for 5,143 Alaskan lakes. Regional lake CH4 emissions, based on satellite remote sensing analyses, were lower compared to previous estimates based on upscaling from individual lakes2,3 and were consistent with independent airborne CH4 observations. Thermokarst lakes formed by thaw of organic-rich permafrost had the highest fluxes, although lake density and lake size distributions also controlled regional emissions. This new remote sensing approach offers an opportunity to improve knowledge about Arctic CH4 fluxes and helps to explain long-standing discrepancies between estimates of CH4 emissions from atmospheric measurements and data upscaled from individual lakes.

Description: A new empirical model of field‐aligned currents in the Earth's ionosphere has been developed. This model is derived using magnetometer data from the CHAallenging Minisatellite Payload, Ø rsted, and Swarm satellite missions, which has created a database that spans more than 15 years. These data have been associated with solar wind conditions using the Advanced Composition Explorer satellite, as well as the urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0001, urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0002, urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0003, and urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0004 solar indices. With the wealth of data and associated driving conditions, this model has been developed to reproduce field‐aligned current maps of the ionosphere based on solar wind electric field, interplanetary magnetic field clock angle, dipole tilt angle, solar index, and geographic hemisphere. This model was constructed using a series of spherical cap harmonic analysis fits based on small selections of the overall database. The coefficients of these fits were then used to develop a model that would reproduce these coefficients based on the previously described driving conditions. One of the most notable improvements demonstrated by this model is the ability to show distinct current regions in the ionosphere, particularly with respect to Region 0 currents during northward urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0005 and highly positive or negative urn:x-wiley:jgra:media:jgra55433:jgra55433-math-0006.

Description: We use the improved Parker‐Oldenburg's formulas that include a reference depth into the exponential term and employ the Gauss‐fast Fourier transform method to determine Moho depth beneath the Tibetan Plateau. The synthetic models demonstrate that the improved Parker's formula has high accuracy with the maximum absolute error less than 0.25 mGal compared to the analytical solution. Two inversion parameters, that is, the reference depth and the density contrast, are essential for the Moho estimation based on the gravity field, and they need to be determined in advance to obtain correct results. Therefore, the Moho estimates derived from existing seismic studies are used to reduce the nonuniqueness of the gravity inversion and to determine these parameters by searching for the maximum correlation between the gravity‐inverted and seismic‐derived Moho depths. Another critical issue is to remove beforehand the gravity effects of other factors, which affect the observed gravity field besides Moho variations. In addition to the topography, the gravity effects of the sedimentary layer and crystalline crust are removed based on existing crustal models, while the upper mantle impact is determined based on the seismic tomography model. The inversion results show that the Moho structure under the Tibetan plateau is very complex with the depths varying from about 30–40 km in the surrounding basins (e.g., Ganges basin, Sichuan basin, and Tarim basin) to 60–80 km within the plateau. This considerable difference up to 40 km on the Moho depth reveals the substantial uplift and thickening of the crust in the Tibetan Plateau. Furthermore, two visible “Moho depression belts” are observed within the plateau with the maximum Moho deepening along the Indus‐Tsangpo Suture and along the northern margin of Tibet bounding the Tarim basin with the relatively shallow Moho in central Tibet between them. The southern “belt” is likely formed in compressional environment, where the Indian plate underthrusts northward beneath the Tibetan Plateau, while the northern one could be formed by the southward underthrust of the Asian lithosphere beneath Tibet.

Description: Global measurements of incision rate typically show a negative scaling with the time scale over which it was averaged, a phenomenon referred to as the ‘Sadler effect’. This time dependency is thought to result from hiatus periods between incision phases, which leads to a power law scaling of incision rate with timescale. Alternatively, the ‘Sadler effect’ has been argued to be a consequence of the mobility of the modern river bed, where the timescale dependency of incision rates arises from a bias due to the choice of the reference system. In this case, incision rates should be independent of the timescale, provided that the correct reference system is chosen. It is unclear which model best explains the ‘Sadler effect’, and, if a timescale dependency exists, which mathematical formulation can be used to describe it. Here, we present a compilation of 581 bedrock incision rates from 34 studies, averaged over timescales ranging from single floods to millions of years. We constrain the functional relationship between incision rate and timescale, and show that time‐independent incision rate is inconsistent with the global data. Using a power law dependence, a single constant power is inconsistent with the distribution of observed exponents. Therefore, the scaling exponent is site‐dependent. Consequently, incision rates measured over contrasting timescales cannot be meaningfully compared between different field sites without properly considering the ‘Sadler effect’. We explore the controls on the variable exponents and propose an empirical equation to correct observed incision rates for their timescale dependency.

Description: In typical Andean arc magmas, amphibole appears as a phenocryst phase only after considerable differentiation. However, some near-primitive volcanic rocks (high-Mg andesites and basalts) from monogenetic centers in the Puna plateau of Argentina also contain amphibole phenocrysts, implying special conditions of hydrous magma generation in this back-arc setting. This study documents typical examples from Southern and Northern Puna regions and uses the major and trace-element compositions of amphibole to constrain a petrogenetic model for the hydrous magmas. There are significant differences in the nature of amphiboles and their host lavas depending on location of the volcanic centers in the Southern and the Northern Puna regions. In the Southern Puna, basaltic andesitic lavas have Sr/Y values 〉40 and amphiboles show skeletal forms and occur in an assemblage with olivine and pyroxene. The amphibole compositions are relatively Al- and Ti-poor compared to the Northern Puna. Thermobarometry indicates amphibole crystallization temperatures of 960–1000 °C at moderate pressure (〈 5 kbar). In contrast, the mafic lavas from centers in the Northern Puna show Sr/Y ratios lower than 20 and amphiboles in these rocks coexist with a plagioclase-orthopyroxene assemblage. The Northern Puna amphiboles have higher Ti and Al contents than those in the southern region and the thermobarometry estimates imply generally higher crystallization temperatures (〉1000 °C) and pressures (6–8 kbar). Furthermore, the chemical composition of amphibole phenocrysts in the Northern Puna Campo Negro center suggests an alkaline affinity of the parental magmas which, together with radiogenic isotope data from earlier studies, indicates a significant contribution of the enriched lithosphere in the magma source. The new data collectively suggest high pressure evolution of hydrous magmas in the Southern Puna, whereas the Northern Puna magmas underwent more differentiation at higher levels in the crust. This contrast in the evolution history of magmas below both regions can be connected with their position relative to partial melting zones in the mid-upper crust, which are larger and longer-lived in the north than in the south, thus favoring a slower ascent of magmas in that region.

Description: Forecasting and early warning systems are important investments to protect lives, properties and livelihood. While early warning systems are frequently used to predict the magnitude, location and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services or financial loss. Complementing early warning systems with impact forecasts has a two‐fold advantage: it would provide decision makers with richer information to take informed decisions about emergency measures, and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multi‐hazard early warning systems. This review discusses the state‐of‐the‐art in impact forecasting for a wide range of natural hazards. We outline the added value of impact‐based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.

Description: This study investigates the usage of HyMAP airborne hyperspectral and Sentinel-2, ASTER and Landsat-8 OLI spaceborne multispectral data for detailed mapping of mineral resources in the Arctic. The EnMAP Geological Mapper (EnGeoMAP) and Iterative Spectral Mixture Analysis (ISMA) approaches are tested for mapping of mafic-ultramafic rocks in areas covered by abundant lichen. Using the Structural Similarity Index Measure (SSIM), the output classification results from airborne data are quantitatively compared to the available geological map and to the HyMAP reference data in case of using spaceborne dataset. Results demonstrate the capability of both airborne and spaceborne data to provide large-scale reconnaissance mapping of geologic materials over vast arctic regions where field access is limited. The distributions of three ultramafic units (dunite, peridotite, pyroxenite) and one mafic unit (gabbro) are mapped based on analyzing specific visible and near-infrared and short-wave-infrared spectral features. The extent of peridotite and dunite units mapped using both approaches is consistent with geological map, whereas pyroxenite abundance maps show different patterns in their distribution as compared to the geological map. The results suggest that EnGeoMAP method has a better performance than ISMA method for mapping the dunite unit, whilst ISMA performs better for mapping peridotite and pyroxenite rocks.

Description: In risk assessment, the exposure component describes the elements exposed to the natural hazards and susceptible to damage or loss, while the vulnerability component defines the likelihood to incur damage or loss conditional on a given level of hazard intensity. In this article, we propose a novel adaptive approach to exposure modeling which exploits Dirichlet-Multinomial Bayesian updating to implement the incremental assimilation of sparse in situ survey data into probabilistic models described by compositions (proportions). This methodology is complemented by the introduction of a custom spatial aggregation support based on variable-resolution Central Voronoidal Tessellations. The proposed methodology allows for a more consistent integration of empirical observations, typically from engineering surveys, into large-scale models that can also efficiently exploit expert-elicited knowledge. The resulting models are described in a probabilistic framework, and as such allow for a more thorough analysis of the underlying uncertainty. The proposed approach is applied and discussed in five countries in Central Asia.

Description: Knowledge of the in‐situ stress state of the Earth´s crust plays a key role in understanding geological processes including plate tectonics, earthquakes, slope failure and igneous emplacement. In this paper, we determine the in‐situ stress orientation from the PTA2 borehole on the Island of Hawai´i, drilled into a lava flow dominated sequence between Mauna Kea and Mauna Loa. High‐resolution acoustic images were collected from the open hole interval 886 m to 1567 m. Based on identification of 371 borehole breakouts for a total length of 310 m, the mean orientation of the minimum horizontal principal stress is N106° and remains constant across different volcanic rock fabrics. Changes in borehole breakout shape are linked to the different strength of volcanic facies and intra‐facies. The orientation of the present‐day stress field at Mauna Kea deviates from the plate forces and regional tectonic stress field. We interpret the compressive stress regime at the PTA2 site as resulting from the competing gravitational fields of the large topographic highs of Mauna Kea and Mauna Loa. Our study reveals that the mass accumulation associated with shield volcano growth imparts significant local variations to the sub‐surface stress state on volcanic islands consisting of overlapping shield volcanoes. The results have significant implications for stress accumulation leading to brittle failure and flank collapse, along with potentially influencing magma accumulation and ascent pathways during volcanic island evolution. This study provides the first insights into the orientation of the present‐day stress field between the major island forming shield volcanoes of Hawai’i.

Description: Wind turbines produce mechanical energy that can propagate to the ground and disturb sensitive measurements such as seismic recordings. The aim of the large-scale experiment Seismic Monitoring And Research of wind Turbine Induced Emissions (SMARTIE1) at a single wind turbine in Pfinztal (SW Germany) is to understand how wind turbines emit seismic signals under different operating conditions and how these seismic signals propagate through the local subsurface. The main objectives of SMARTIE1 are the investigation of wind turbine induced seismic signals, the characteristics of their propagation behaviour, as well as the radiation pattern of a single wind turbine as defined using particle motions. Moreover, we quantify the emission of the wind turbine induced seismic signals with respect to the wind speed. The combination of the wind turbine’s emission into the subsurface and the attenuation behaviour of the seismic signals (ground motion velocity) can be used to estimate protection radii around seismic stations to ensure the recording of seismic signals without noticeable influences of the wind turbines. In this study, we detect several discrete wind turbine induced frequency peaks ranging from 1 to 10 Hz. We identify a radiation pattern of the wind turbine, which could give further insights into the interaction between the movement of the wind turbine’s nacelle and the generation of the wind turbine induced seismic signals. Using profile measurements with a maximum distance of almost 3 km each, we fit a power-law decay for power spectral density proportional to 1/r b. The attenuation factor, b, ranges from 0.7 to 1.3 for lower frequencies between 1 and 4 Hz, and increases to b = 2.3 for the higher frequency peak around 5.25 Hz. Finally, we present an example of estimation of a protection radius around the seismic station of the Collm Observatorium that is part of the German Regional Seismic Network. The example protection radius around Collm Observatorium regarding this single wind turbine is reached at a minimum distance of 3.7 km.

Description: In the framework of the Deep Electromagnetic Soundings for Mineral Exploration project, we conducted ground‐based long‐offset transient‐electromagnetic measurements in a former mining area in eastern Thuringia, Germany. The large‐scale survey resulted in an extensive dataset acquired with multiple high‐power transmitters and a high number of electric and magnetic field receivers. The recorded data exhibit a high data quality over several decades of time and orders of magnitude. Although the obtained subsurface models indicate a strong multi‐dimensional subsurface with variations in resistivity over three orders of magnitude, the electrical field step‐on transients are well fitted using a conventional one‐dimensional inversion. Due to superimposed induced polarization effects, the transient step‐off data are not interpretable with conventional electromagnetic inversion. For further interpretation in one and two dimensions, a new approach to evaluate the long‐offset transient‐electromagnetic data in frequency domain is realized. We present a detailed workflow for data processing in both domains and give an overview of technical obstructions that can occur in one domain or the other. The derived one‐dimensional inversion models of frequency‐domain data show strong multi‐dimensional effects and are well comparable with the conventional time domain inversion results. To adequately interpret the data, a 2.5D frequency‐domain inversion using the open source algorithm MARE2DEM (Modeling with Adaptively Refined Elements for 2‐D EM) is carried out. The inversion leads to a consistent subsurface model with shallow and deep conductive structures, which are confirmed by geology and additional geophysical surveys.

Description: Geothermal reservoir production and associated induced seismicity may experience pronounced attention in the near future, given the ambitious plans for reducing greenhouse gas emissions toward a carbon-neutral economy and society. At some geothermal sites, the occurrence of hazard- and risk-prone induced earthquakes caused by or associated with reservoir stimulation has resulted in project shutdown (e.g., Pohang, South Korea, and Basel Deep Heat Mining, Switzerland). At other geothermal sites, the maximum event magnitudes were successfully maintained below a threshold defined by local authorities (e.g., Helsinki St1 Deep Heat project in Helsinki, Finland). In this study, we review some of our results from seismological and geomechanical reservoir characterization at The Geysers geothermal reservoir in California, USA, the largest producing geothermal field worldwide. We relate our findings to other geothermal sites to better understand the variability of reservoir behavior. In particular, we obtain a constant and relatively low seismic injection efficiency at The Geysers, which is interpreted to be related to the large energy dissipation through thermal processes and additional dissipation through aseismic slip, the latter now being considered to play a fundamental role in earthquake nucleation. We discuss some characteristics of the seismicity from The Geysers that suggest stable reservoir seismic injection efficiency and possibly low potential to rupture into large induced earthquakes, reducing the associated seismic hazard.

Description: Different Earth orientation parameter (EOP) time series are publicly available that typically arise from the combination of individual space geodetic technique solutions. The applied processing strategies and choices lead to systematically differing signal and noise characteristics particularly at the shortest periods between 2 and 8 days. We investigate the consequences of typical choices by introducing new experimental EOP solutions obtained from combinations at either normal equation level processed by Deutsches Geodätisches Forschungsinstitut at the Technical University of Munich (DGFI‐TUM) and Federal Agency for Cartography and Geodesy (BKG), or observation level processed by European Space Agency (ESA). All those experiments contribute to an effort initiated by ESA to develop an independent capacity for routine EOP processing and prediction in Europe. Results are benchmarked against geophysical model‐based effective angular momentum functions processed by Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences (ESMGFZ). We find, that a multitechnique combination at normal equation level that explicitly aligns a priori station coordinates to the ITRF2014 frequently outperforms the current International Earth Rotation and Reference Systems Service (IERS) standard solution 14C04. A multi‐Global Navigation Satellite System (GNSS)‐only solution already provides very competitive accuracies for the equatorial components. Quite similar results are also obtained from a short combination at observation level experiment using multi‐GNSS solutions and SLR from Sentinel‐3A and Sentinel‐3B to realize space links. For ΔUT1, however, very long baseline interferometry (VLBI) information is known to be critically important so that experiments combining only GNSS and possibly SLR at observation level perform worse than combinations of all techniques at normal equation level. The low noise floor and smooth spectra obtained from the multi‐GNSS solution nevertheless illustrates the potential of this most rigorous combination approach so that further efforts to include in particular VLBI are strongly recommended.

Description: Carbonates are the major hosts of carbon on Earth’s surface and their fate during subduction needs to be known to understand the deep carbon cycle. Magnesite (MgCO3) is thought to be an important phase participating in deep Earth processes, but its phase stability is still a matter of debate for the conditions prevalent in the lowest part of the mantle and at the core mantle boundary. Here, we have studied the phase relations and stabilities of MgCO3 at these P,T conditions, using Raman spectroscopy at high pressures (∼148GPa) and after heating to high temperatures (∼3600 K) in laser-heated diamond anvil cell experiments. The experimental Raman experiments were supplemented by x-ray powder diffraction data, obtained at a pressure of 110 GPa. Density-functional-theory-based model calculations were used to compute Raman spectra for several MgCO3 high-pressure polymorphs, thus allowing an unambiguous assignment of Raman modes. By combining the experimental observations with the density-functional-theory results, we constrain the phase stability field of MgCO3 with respect to the high-pressure polymorph, MgCO3-II. We further confirm that Fe-free MgCO3-II is a tetracarbonate with monoclinic symmetry (space group C2/m), which is stable over the entire P, T range of the Earth’s lowermost mantle geotherm.

Description: The magnetic equator in the Brazilian region has moved over 1100 km northwards since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long‐term changes in the daily variation due to the influence of secular variation, solar activity, season and lunar phase. The H day‐to‐day variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet‐time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day‐to‐day variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long‐term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation.

Description: Synthetic portlandite single crystals were used to measure thermal diffusivity and elastic constants. The full tensor of elastic constants cijkl is derived by Brillouin spectroscopy at ambient conditions. The resultant aggregate bulk and shear moduli are KS, VRH=32.2(3) GPa and GVRH=21.2(2) GPa, respectively. The thermal diffusivity D was measured from −100∘C to 700∘C parallel [001] and perpendicular [100] to the crystallographic c-axis using laser flash method. The dehydration of the crystals influences the thermal diffusivity determination depending on sample size, orientation and heating rate. Thermal diffusivity and the derived thermal conductivity show a pronounced anisotropy with a maximum perpendicular to the c-axis, i.e. in the plane of the [CaO6] octahedral layers. In the same direction the highest sound velocities (vP and vmean) and longest mean free path length of phonons are determined. The thermal diffusivity as well as the derived thermal conductivity show a distinct temperature dependence.

Description: The tectonic activity and potential for linkage of adjacent active faults are crucial for seismic assessment. As the two largest faults that bound the Weihe Graben (central China), the Qinling Northern Piedmont Fault (QNF, ~200 km) and the Huashan Piedmont Fault (HPF, ~150 km) are mainly responsible for seismic risk in this densely-populated area, where the 1556 M 8.5 Huaxian earthquake occurred with 830,000 fatalities. However, their tectonic activity and the degree of interaction remain poorly constrained, hampering an adequate seismic risk assessment of the Weihe Graben. Here, we integrate 23 new 10Be-derived catchment-averaged denudation rates of ~0.06–0.32 mm/yr with topographic metrics to evaluate the seismic risk. The results demonstrate that the landscape of the Qinling and Huashan Mountains is in transient state in response to the tectonic perturbations of the QNF and the HPF, with tectonic knickpoints formed along main streams and tributaries, and widespread unstable drainage divides. These two faults have comparable tectonic activity, and are potentially capable of generating earthquakes with the maximum magnitude of Mw ~7.7–7.9. Moreover, they have likely started linking, posing a greater seismic risk than previously estimated.

Description: Methane emissions from natural wetlands tend to increase with temperature and therefore may lead to a positive feedback under future climate change. However, their temperature response includes confounding factors and appears to differ on different time scales. Observed methane emissions depend strongly on temperature on a seasonal basis, but if the annual mean emissions are compared between sites, there is only a small temperature effect. We hypothesize that microbial dynamics are a major driver of the seasonal cycle and that they can explain this apparent discrepancy. We introduce a relatively simple model of methanogenic growth and dormancy into a wetland methane scheme that is used in an Earth system model. We show that this addition is sufficient to reproduce the observed seasonal dynamics of methane emissions in fully saturated wetland sites, at the same time as reproducing the annual mean emissions. We find that a more complex scheme used in recent Earth system models does not add predictive power. The sites used span a range of climatic conditions, with the majority in high latitudes. The difference in apparent temperature sensitivity seasonally versus spatially cannot be recreated by the non‐microbial schemes tested. We therefore conclude that microbial dynamics are a strong candidate to be driving the seasonal cycle of wetland methane emissions. We quantify longer‐term temperature sensitivity using this scheme and show that it gives approximately a 12% increase in emissions per degree of warming globally. This is in addition to any hydrological changes, which could also impact future methane emissions.

Description: Multispacecraft missions such as Cluster, Themis, Swarm, and MMS contribute to the exploration of geospace with their capability to produce gradient and curl estimates from sets of spatially distributed in situ measurements. This paper combines all existing estimators of the reciprocal vector family for spatial derivatives and their errors. The resulting framework proves to be robust and adaptive in the sense that it works reliably for arrays with arbitrary numbers of spacecraft and possibly degenerate geometries. The analysis procedure is illustrated using synthetic data as well as magnetic measurements from the Cluster and Swarm missions. An implementation of the core algorithm in Python is shown to be compact and computationally efficient so that it can be easily integrated in the various free and open source packages for the Space Physics and Heliophysics community.

Description: Space weather driven atmospheric density variations affect low Earth orbit (LEO) satellites during all phases of their operational lifetime. Rocket launches, re-entry events and space debris are also similarly affected. A better understanding of space weather processes and their impact on atmospheric density is thus critical for satellite operations as well as for safety issues. The Horizon 2020 project Space Weather Atmosphere Model and Indices (SWAMI) project, which started in January 2018, aims to enhance this understanding by: - Developing improved neutral atmosphere and thermosphere models, and combining these models to produce a new whole atmosphere model. - Developing new geomagnetic activity indices with higher time cadence to enable better representation of thermospheric variability in the models, and improving the forecast of these indices. The project stands out by providing an integrated approach to the satellite neutral environment, in which the main space weather drivers are addressed together with model improvement. The outcomes of SWAMI will provide a pathway to improved space weather services as the project will not only address the science issues, but also the transition of models into operational services. The project aims to develop a unique new whole atmosphere model, by extending and blending the Unified Model (UM), which is the Met Office weather and climate model, and the Drag Temperature Model (DTM), which is a semi-empirical model which covers the 120–1500 km altitude range. A user-focused operational tool for satellite applications shall be developed based on this. In addition, improved geomagnetic indices shall be developed and shall be used in the UM and DTM for enhanced nowcast and forecast capability. In this paper, we report on progress with SWAMI to date. The UM has been extended from its original upper boundary of 85 km to run stably and accurately with a 135 km lid. Developments to the UM radiation scheme to enable accurate performance in the mesosphere and lower thermosphere are described. These include addition of non-local thermodynamic equilibrium effects and extension to include the far ultraviolet and extreme ultraviolet. DTM has been re-developed using a more accurate neutral density observation database than has been used in the past. In addition, we describe an algorithm to develop a new version of DTM driven by geomagnetic indices with a 60 minute cadence (denoted Hp60) rather than 3-hourly Kp indices (and corresponding ap indices). The development of the Hp60 index, and the Hp30 and Hp90 indices, which are similar to Hp60 but with 30 minute and 90 minute cadences, respectively, is described, as is the development and testing of neural network and other machine learning methods applied to the forecast of geomagnetic indices.

Description: The W. Alps high pressure ophiolitic terranes (Monviso and Rocciavre areas) are a natural laboratory to study processes such as nappe-stacking and crustal exhumation in the deep regions of subduction margins. We sampled each of the main shear zones, representing thrust contacts later reactivated as detachments, for petrological and Rb-Sr multi-mineral geochronological analyses. Three generations of white mica are commonly found in mylonitized metasediments with crystal cores formed during the high pressure event, a broad rim formed during decompression in the epidote blueschist facies and texturally late muscovite flakes locally lining the main foliation. Semi-brittle discrete shear zones commonly crosscut previous structures witnessing deformation at temperatures lower than 300°C during exhumation. In spite of this apparent structural heterogeneity, homogeneous deformation ages mostly ranging between 38 and 35 Ma were obtained for all the shear zones bounding these major ophiolitic bodies. Pseudosection modeling confirms that the bulk of the shearing occurred in the epidote blueschist facies around 400–450°C and 1.0–1.5 GPa. These findings suggest that the shear zones between high pressure ophiolitic nappes were being actively mylonitized during exhumation in the lower epidote blueschist facies (25–40 km depth) between 38 and 35 Ma while some of the units forming the internal crystalline massifs (e.g. the Dora Maira Ultra High-Pressure unit) were still buried at more than 100 km depth (3–4 GPa and 36-34 Ma, according to most recent peak burial estimates). The growth of a crustal-scale duplex in the W. Alps is seen here as a consequence of basal accretion events that followed the exhumation of eclogitized coherent crustal slices in a serpentinized subduction channel. We conclude that in the study area (i) the buoyancy-driven exhumation of subducted continental crust has not been the only and decisive trigger for the exhumation of eclogitized oceanic lithosphere and (ii) continental subduction imprint on crustal wedge dynamics may have not been as instrumental as previously thought.

Description: As an integral part of the Eastern Cordillera, the fault-bounded Malcante mountain range (up to 5100 m) in the NW Argentine Andes (ca. 25°S) is located in the transition between the arid Puna Plateau to the west and the humid broken foreland to the east. At this latitude, the topographic gradient of the eastern Andean margin forms an efficient orographic barrier that causes pronounced east–west rainfall and surface-process gradients. In this setting, the Malcante Range is an important, yet poorly studied structural high formed during the Cenozoic topographic growth of the Central Andes. In this study, we combine (a) detailed field observations, (b) a two-dimensional structural reconstruction, (c) apatite fission track and (U–Th-Sm)/He thermochronology of bedrock samples from a vertical transect across the western flank of the Malcante Range, and (d) inverse thermal modelling using QTQt software with the aim of deciphering the exhumation history of this mountain range. Field data indicate the presence of an angular unconformity between Cenozoic foreland deposits and older sedimentary strata, suggesting an initial episode of deformation during the middle-late Eocene, while our thermal model constrains the onset of exhumation at ~10 Ma. We suggest that exhumation was related to the unroofing of the easily erodible sedimentary cover, which prevented significant initial surface uplift. This may have changed as more resilient bedrock was exposed at ~5 Ma according to the thermal model, promoting rapid rock uplift. In combination with published data, our thermochronology allows us to speculate on the existence of a zone of deformation concentrated in the area of the present-day Pasha (24.5°S), Malcante (25°S), and Agua de Castilla (25.4°S) mountain ranges by ca. 10 Ma.

Description: Thermochronology, Apatite fission track, Apatite (U–Th)/He, Mountain building, Eastern cordillera, NW Argentina

Description: The relationships between volcanic activity and tectonics at the southernmost termination of the Main Ethiopian Rift (MER), East Africa, still represent a debated problem in the MER evolution. New constraints on the timing, evolution and characteristics of the poorly documented volcanic activity of the Dilo and Mega volcanic fields (VF), near the Kenya-Ethiopia border are here presented and discussed. The new data delineate the occurrence of two distinct groups of volcanic rocks: 1) Pliocene subalkaline basalts, observed only in the Dilo VF, forming a lava basement faulted during a significant rifting phase; 2) Quaternary alkaline basalts, occurring in the two volcanic fields as pyroclastic products and lava flows issued from monogenetic edifices and covering the rift-related faults. 40Ar/39Ar dating constrains the emplacement time of the large basal lava plateau to ~3.7 Ma, whereas the youngest volcanic activity characterising the two areas dates back to 134 ka (Dilo VF) to as recent as the Holocene (Mega VF). Volcanic activity developed along tectonic lineaments independent from those of the rift. No direct relations are observed between the Pliocene, roughly N-S-trending major boundary faults of the Ririba rift and the NE-SW-oriented structural trend characteristic of the Quaternary volcanic activity. We speculate that this change in structural trend may be the expression of (1) inherited crustal structures affecting the distribution of the recent volcanic vents, and (2) a local stress field controlled by differences in crustal thickness, following a major episode of reorganization of extensional structures in the region due to rift propagation and abandonment.

Description: One of Sweden’s most successful geologists, Professor Ove Stephansson, passed away on February, 19 2020. During his professional life he published more than 200 articles, conference papers and books.

Description: Knowledge of the internal state of rock is key to anticipate its rheological response and susceptibility to external factors. Time‐dependent failure in rock is controlled by internal state changes, like damage accumulation or strength degradation. But assessing internal states and changes thereof, non‐destructively and independent of external forcing is not straight forward. Residual strains, measured with neutron diffraction techniques are used as a proxy for the internal state in material sciences. We investigated its potential for progressive rock failure by measuring residual strain states of an untested and three mechanically and chemo‐mechanically pretested Carrara marble samples. We collected neutron diffraction data for three crystal lattice planes {10̅14}, {0006}, and {11̅20}. Measurements showed an initial overall contractional spatially homogeneous residual unit cell volume strain state of about ‐400μstrain, though magnitudes were strongly partitioned among measured crystal lattice planes. However, they are equal within the spatial orientations of the intact sample. For the pretested samples, the induction and relaxation of strains varied spatially with the pretesting stress field and environmental conditions. The vertical extent of superposition of the initial residual strain state was greatest in wet samples, the magnitude of induced extensional strain highest in the dry sample. This indicates chemo‐mechanically enhanced subcritical crack growth with concomitant residual strain relaxation as well as the mitigation of extensional strain built up by the presence of water during pretesting. Our experiments show, that residual strain has a significant potential to provide insights into past and actual internal states to anticipate progressive rock failure.

Description: We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5 and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including: (i) more comprehensive treatment of uncertainties; (ii) direct traceability between global and local projections; (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon and emissions scenario. Our analysis highlights the importance of variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlights the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large (〉 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see a substantial differences in the breakdown of model variance as a function of location, timescale and emissions scenario.

Description: Shrub encroachment has far‐reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning. We document the compositional change and potential drivers for a northern Namibian Combretum woodland transitioning into a Terminalia shrubland. We use a multiproxy record (pollen, sedimentary ancient DNA, biomarkers, compound‐specific carbon (δ13C) and deuterium (δD) isotopes, bulk carbon isotopes (δ13Corg), grain size, geochemical properties) from Lake Otjikoto at high taxonomical and temporal resolution. We provide evidence that state changes in semiarid environments may occur on a scale of one century and that transitions between stable states can span around 80 years and are characterized by a unique vegetation composition. We demonstrate that the current grass/woody ratio is exceptional for the last 170 years, as supported by n‐alkane distributions and the δ13C and δ13Corg records. Comparing vegetation records to environmental proxy data and census data, we infer a complex network of global and local drivers of vegetation change. While our δD record suggests physiological adaptations of woody species to higher atmospheric pCO2 concentration and drought, our vegetation records reflect the impact of broad‐scale logging for the mining industry, and the macrocharcoal record suggests a decrease in fire activity associated with the intensification of farming. Impact of selective grazing is reflected by changes in abundance and taxonomical composition of grasses and by an increase of nonpalatable and trampling‐resistant taxa. In addition, grain‐size and spore records suggest changes in the erodibility of soils because of reduced grass cover. Synthesis. We conclude that transitions to an encroached savanna state are supported by gradual environmental changes induced by management strategies, which affected the resilience of savanna ecosystems. In addition, feedback mechanisms that reflect the interplay between management legacies and climate change maintain the encroached state.

Description: This paper presents the results of multiproxy research (pollen, charcoal, plant macrofossil and testate amoebae) on the biogenic deposits core from Gorodetsky Moch, an ombrotrophic peatland in western Russia (Western Dvina Lakeland). We reconstructed the impact of disturbance on peatland development in the last 300 years by using chronology of the records based on 14C and 210Pb data set. The multiproxy reconstruction was compared with changes in the land cover using historical maps and Corona images, which provides a unique spatial analysis of past ecological and land-use changes. We aimed to determine the effect of local disturbances (drainage) and land-use changes (landscape openness) on the development of the peatland during the last 300 years. Our study suggests that human activity had a crucial impact on the development of the peatland in the last centuries. The analysis of testate amoebae and plant macrofossils revealed a clear disturbed layer in the second half of the 20th century CE. Most probably, the drainage of the peatland triggered changes in the community of testate amoebae and plants, thereby causing a functional shift in Sphagnum peatland ecosystem. The hydrological stress and vegetation composition shift led to the collapse of mixotrophic testate amoebae. However, the peatland showed strong resilience and recovered toward the end of the 20th century CE and the beginning of the 21st century CE, despite the lower water table. Our study shows an example of the peatland ecosystem that experienced a considerable stress but finally sustained the former function.

Description: Primary productivity of forest ecosystems depends on the availability of plant‐essential mineral nutrients. Because nutrient demand of trees often exceeds nutrient supply from rock, tree nutrition is sustained by efficient re‐utilization of organic‐bound nutrients. These nutrients are continuously returned from trees to the forest floor in litterfall. However, over millennia nutrient limitation may develop in landscapes from which nutrients are permanently lost by drainage and erosion. Such a deficit is prevented if advection of unweathered bedrock towards the surface as driven by erosion continuously supplies fresh nutrients. Yet, the mechanisms and the depth range over which this deep nutrient resource is accessed are poorly known. We show that in two montane temperate forest ecosystems in the Black Forest and Bavarian Forest the geogenic source of nutrients was found within a depth zone of several meters. This deep zone contains a large pool of biologically available nutrients. We applied isotope ratios as proxies for nutrient uptake depth, and we tracked the regolith depth at which the isotope ratios of 87Sr/86Sr and 10Be(meteoric)/9Be match the respective values in plant tissue. We mapped the depth distribution of the biologically available calcium‐bound form of the most plant‐essential mineral nutrient phosphorus and found that the depth of phosphorus availability is as deep or even deeper as the range defined by the isotope ratios. We conclude that nutrient supply from a regolith depth of several meters is critical for forest ecosystem function in landscapes of moderate hillslopes and rainfall that are affected by permanent nutrient loss.

Description: A reliable evaluation of four Scintrex CG-6 gravimeters was done with respect to the stability of the calibration, measurement uncertainty, repeatability, and daily drift behaviour. An uncertainty on the 10 nm/s2 level for adjusted g-results is striven for. Measurements were performed on the Vertical Gravimeter Calibration Line Hannover (VGCH, 192 μm/s2 range, 20-storey building, 10 μm/s2 interval, 2 · 10−4 expanded uncertainty of the scale). The achieved standard deviations of the adjusted calibration factors are in the order of 2 to 6 · 10−5, and the maximum variations between two calibration results for a single instrument varied between 2 to 7 · 10−4. Therefore, the stability of the scale factor (calibration) of a CG-6 instrument has to be controlled by the user before and after the microgravimetric survey. The transportation drift over some hours or a working day shows partly short-term variations with an impact of up to 100 nm/s2 which can only be identified and controlled by sufficient repeated observations on same points. The manufacturer Scintrex Ltd. solved the problematic nature of an instrumental air pressure effect but a test especially for older CG gravimeters is still recommended. Overall, the CG-6 gravimeters meet fully the expectations.

Description: Eine wirklichkeitsgetreue Evaluierung von vier Scintrex-CG6-Gravimetern wurde vorgenommen, um Aus­sagen zur Stabilität ihrer Kalibrierung, Messunsicherheit, Wiederholbarkeit und des Driftverhaltens treffen zu können. Dabei wird für ausgeglichene Schwerewerte eine Unsicherheit in der Größenordnung von 10 nm/­s 2 angestrebt. Die Messungen wurden in der Vertikalen Gravimeter-Kalibrierlinie Hannover durchgeführt. Die 20 Punkte decken insgesamt einen Schwerebereich von 192 μm/s 2 ab und haben einen Nachbarschaftsabstand von jeweils 10 μm/s 2 . Die Maßstabsgenauigkeit wird relativ mit 2 · 10 −4 angenommen. Bei den CG-6-Untersuchungen wurden für die Kalibrierfaktoren Standardabweichungen von 2 bis 6 · 10 −5 erhalten. Allerdings unterscheiden sich die einzelnen zeitlich auseinanderliegenden Kalibrierergebnisse mit maximalen Diskrepanzen zwischen 2 bis 7 · 10 −4 . Deshalb sollte die zeitliche Stabilität der Maßstabsfaktoren (Kalibrierung) der CG-6-Gravimeter durch die Nutzer jeweils vor und nach den mikrogravimetrischen Vermessungen kontrolliert werden. Die Transportdriften über einige Stunden oder einem Arbeitstag zeigen z. T. kurzperiodische Variationen mit Diskrepanzen von bis zu 100 nm/s 2. Bei Vermessungen mit nur einem Instrument können solche Driftverläufe nur durch wiederholtes Messen auf den einzelnen Punkten erkannt werden. Der Hersteller Scintrex Ltd. hat die Problematik eines instrumentellen Luftdruckeffekts bei seinen Instrumenten gelöst. Allerdings wird eine Überprüfung besonders bei älteren CG-Gravimetern seitens der Autoren empfohlen. Im Ganzen gesehen erfüllen die neuen CG-6-Gravimeter die Erwartungen.