bluuebunny/crossref_metadata_2025 huggingface dataset:
Vigorous Internal Wave Generation at the Continental Slope North of Svalbard
Authors: Baumann Till M. , Fer Ilker
Published: March 2022

Mixing along the pathway of Atlantic Water in the Arctic Ocean is crucial for the distribution of heat in the Arctic Ocean. The warm boundary current typically flows along the upper continental slope where energy conversion from tides to turbulence and tidally driven mixing can be important; however, observations -and thus understanding- of these spatiotemporally highly variable processes are limited.

Here we analyze yearlong observations from three moorings (W1, W2 and W3) spanning the continental slope North of Svalbard at 18.5°E over 16 km from 400 m to 1200 m isobaths, deployed between September 2018 and October 2019. Full-depth current records show strong barotropic diurnal (i.e., sub-inertial) tidal currents, dominated by the K1 constituent. These tidal currents are strongest at mooring W2 over the continental slope (~700 m isobath) likely due to topographic trapping far north of their critical latitude (30°N). The diurnal tide undergoes a seasonal cycle with amplitudes reaching minima of ~4 cm/s in March/April and maxima of ~11 cm/s in June/July. Associated with the diurnal tide peak at W2 in summer 2019 is a strong baroclinic semidiurnal signal up to 15 cm/s around 4.5 km further offshore at W3 between 500 m and 1000 m depth. This semidiurnal current signal exhibits a fortnightly modulation and is characterized by upward energy propagation, indicative of generation at the bottom rather than the surface.

We hypothesize that the semidiurnal baroclinic waves are generated by the barotropic diurnal tide about 15 km upstream. There, the slope is oriented approximately normal to the major axis of the tidal current ellipses, maximizing the cross-isobath flow and thus the tidal energy conversion potential. The topographic slope angle approaches criticality for frequencies close to the second harmonic of K1 (2K1, with a semidiurnal period of 11.965 h) around the 620 m isobath and may thus facilitate an efficient generation of second harmonic internal waves. Linear superposition of a 2K1 wave with the rather weak (~5 cm/s) ambient M2 tide would explain the observed fortnightly modulation. The super-inertial wave (w2K1>f) propagates freely and its pathway is presently not known.

Although further research on the generation mechanism is needed, the strong baroclinic semidiurnal currents observed at the continental slope have direct implications for deep mixing. Furthermore, energetic diurnal tidal currents impinging on a steep continental slope are also known to generate non-linear internal lee-waves that can also lead to substantial turbulence and consequent mixing.
Microplastic mass balances in remote alpine lakes
Authors: Gateuille David , Dusaucy Julia , Naffrechoux Emmanuel , Fanget Philippe , Tourreau Grégory , Gallinelli Peter , Gillet Frédéric
Published: March 2022

Microplastics pose a threat to all the environmental compartments and specifically to aquatic ecosystems. Lakes are particularly exposed to it as they act as accumulator of pollution from their watersheds. Unfortunately, the fate of microplastics in lake ecosystems remains poorly understood because of the multiplicity of sources and transfer pathways. For the first time, the Plastilac project focuses on the contamination of high altitude lakes (from 1300 m to 2800 m above the sea level) by microplastics. Remote lakes constitute easier-to-investigate ecosystems because there are fewer potential sources of microplastics in their watershed, namely the atmospheric deposit, the supply from the watershed through the tributaries and the tourist attendance. Thus, both water column and sediment from 10 lakes located across the French Alps were sampled. The results showed that no lake was free from microplastics, proving the ubiquity of this pollution at a regional scale. The abundance of microplastics varied significantly from one lake to another and the concentrations measured in high altitude lakes (around 10 MP.m-3) were approximately 100 times lower than those reported in the literature for lowland lakes. The water column contamination was not correlated to the vicinity of potential sources (urban areas). On the contrary, higher sediment contaminations were observed in lakes located nearby urban areas. Our analyses also showed that the residence times of microplastics in the water column of these lakes were relatively short, of the order of a few days. In contrast, the residence times of microplastics in the sediments were much longer and lake bottoms retain traces of past contamination. This work constitutes a first for understanding the fate of microplastics in mountainous environments. It provides important information on their dynamics and, in particular, on the temporal dimension of this pollution.
Magnetotelluric investigations in the Ubaye seismic swarm region, Western Alps: a connection between electrical conductivity, fluids, and earthquakes?
Authors: Byrdina Svetlana , Got Jean-Luc , Metral Laurent , Hering Philip , Baques Marion , De Barros Louis , Garambois Stephane , Gueguen Philippe , Rath Volker
Published: March 2022

The Ubaye Region is a seismically active region in the Western Alps (France), regularly struck by seismic swarms characterized by a high number of small to moderate earthquakes, such as in 2003–2004 or 2012–2015. While some earthquakes could be associated with known faults, the character of the observations (high seismicity – low deformation rate) requires complex driving processes beyond local or regional tectonics. Most conceptual models involve fluids present down to depths of several km, and/or long-range transport.

Magnetotellurics (MT) is known to be an efficient imaging method sensitive to crustal fluids. During 2020/21, a data set of 30 MT sites was acquired, covering a signal period ranging between 10-4 to 104 s, with generally all 5 components measured. Data quality was generally satisfactory up to 3 s and sometimes up to 100 s. Major problems were related to topography (including logistics), and to the presence of electromagnetic noise, only to be mitigated by advanced processing methods (FFMT). For the 3-D inversion required by the data (phase tensors, WAL, topography), we have chosen a joint inversion of induction vectors, phase tensors and off-diagonal impedances (previously corrected for static shift with help of phase tensor inversion). This allowed us to obtain the best 3-D model using the ModEM inversion code, explaining all three data types reasonably well.

The main findings from this investigation include (a) a prominent conductor (down to 20 Ωm) located along the axis of the swarm zone, though generally above it; (b) a regional dominance of the Penninic Front in the East and the overridden Mesozoic (Dauphinoise) sediments in the West, both not fully covered by the current survey; (c) strike directions that agree well with most of the mapped faults and focal mechanisms of the strongest seismic events.

Uncertainties associated with the insufficient data coverage in some of the most interesting zones were studied by analysing the sensitivities provided by the inversion and direct forward modelling of significant model features. In general, this led to the conclusion that our sensitivity does reach the border of the seismic swarm activity, but does not cover its depth extent. Due to the gap in data in the central area of interest, the geometry and connectivity of the main conductor remains a hypothesis. Thus, a truly quantitative characterization of prominent identified structures is not currently possible and should be better assessed with additional measurement sites. The different conceptual models proposed for the origin of the seismic swarm activity will be discussed in the light of the MT imaging, and the associated uncertainties.
The representation of atmospheric processes in northeast Greenland in CMIP6 models
Authors: Pickler Carolyne , Turton Jenny , Mölg Thomas , McCrystall Michelle
Published: March 2022

Since the end of the 20th century, Greenland has been the largest contributor to sea level rise.  As temperatures continue to increase, this tendency is projected to continue.  This has resulted in numerous studies which evaluate present and future conditions of the Greenland Ice Sheet, many of which use general circulation models (GCMs). The majority of these focus on sea level rise and/or surface mass balance. While some analyses of atmospheric processes have been undertaken, these have typically been over a larger scale (Arctic or Greenland).  This has led to a lack of regional studies of atmospheric processes and how they are represented in GCMs, particularly over northeast Greenland, an area of increased interest in both its glaciology and atmosphere.

To address this, 67 CMIP6 GCM realizations were subject to the Pickler and Mölg (2021) model selection procedure to determine the most suitable realization over northeast Greenland.  The historical simulation of these realizations were evaluated for: (i) their ability to capture the space-time climatic anomalies over 1979-2014 with respect to ERA5 reanalysis data and (ii) their ability to simulate the mean climatic state of northeast Greenland with respect to four automated weather stations over 2009-2020.  MPI-ESM1-2-HR r6i1p1f1 was found to rank highest and ACCESS-ESM1-5 r10i1p1f1 lowest.

The 67 realizations were then evaluated on their ability to capture two important processes influencing the region: the North Atlantic Oscillation (NAO) and the Greenland blocking (GBI).  All realizations were able to simulate the NAO during boreal winter, while all failed to capture the GBI during boreal summer.  Furthermore, the ability of the top and bottom ranked realizations to simulate precipitation, katabatic winds, sea ice, and warm-air events were examined. This analysis reveals key differences between the representation of regional climates within the GCMs, which highlights the need for a rigorous selection procedure prior to estimating future changes.
Effects of soil biodiversity on soil multifunctionality after 5-year organic substitutions in a Maize field
Authors: Du Xiao fang , Liu Han wen , Li Ying bin , Zhang Xiao ke , Liang Wen ju
Published: March 2022

Organic substitution can benefit to enhance soil health and maintain sustainable food production. Soil organisms play important roles in decomposing organic matter, recycling soil nutrients and resisting pests and diseases. However, the effect of soil biodiversity on soil multifunctionality of farmland ecosystem under organic substitution is still unclear. Here, we studied the shifts of soil biotic communities and soil multifunctionality (functions related with C, nutrient cycling and crop yield), and investigated soil biotic diversity-ecosystem function relationship under a 5-year field organic substitution experiment (30% nitrogen fertilizer substitute with straw, cattle manure and biochar, respectively). Our results showed that the highest value of soil multifunctionality was found in straw substitution treatment. Soil nematode community composition significantly associated with soil multifunctionality. We used structural equation modelling to identify the effects of soil biotic diversities and composition on multifunctionality. The SEM model predicted 74% of the variation in soil multifunctionality, and found that nematode community composition directly drove soil multifunctionality, whereas organic substitution and bacterial community composition could indirectly affect soil multifunctionality by changing soil nematode community. Our study has important implications for the contribution of soil biodiversity in driving multifunctionality of farmland ecosystem and for maintaining the sustainable development of agriculture.
Tillage erosion as an important driver of soil organic carbon (SOC) dynamics long before agricultural mechanisation
Authors: Öttl Lena Katharina , Wilken Florian , Degg Marie-Rose , Wehrhan Marc , Juřicová Anna , Sommer Michael , Fiener Peter
Published: March 2022

Tillage erosion is known to be a major soil degradation process that is mainly associated with increasingly mechanised agriculture since the early 1950s. However, especially soil truncation on convex hilltops and slope shoulders can be already identified on historical aerial photos of our study region in Northeast Germany from the 1950s.

The aim of the study is to better understand the effect of mechanised and especially long-term non-mechanised soil redistribution processes on soil organic carbon (SOC) dynamics over the past 1000 years since the beginning of widespread soil cultivation in our study region and their contribution to the question of soil being a carbon (C) sink or source.

Therefore, a modified version of the spatially explicit soil redistribution and C turnover model SPEROS-C was applied on a large-scale catchment (approx. 200 km²) to simulate lateral soil and SOC redistribution, SOC turnover and erosion-induced vertical mixing within the profile (spatial and vertical resolution 5 m x 5 m and 0.1 m soil depth increments, respectively). The uncertainty of the modelling approach was estimated by varying the input variables according to different realisations of the development of agricultural management over the past 1000 years. The results were validated with an erosion classification derived from Sentinel-2 data and UAV based estimation of topsoil SOC. The lowest SOC stocks were found on hilltops, which points at tillage erosion as the major driver of soil degradation.

Our results show that the beginning influence of tillage erosion on catchment wide vertical SOC fluxes can be traced back to around 500 years ago. This clearly indicates that non-mechanised tillage erosion from the early stage of cultivation affected the SOC patterns in the study area and hence impacts todays C cycling.
Variability of Subpolar Mode Water Volume and Formation in the North Atlantic during 1993-2018
Authors: Stendardo Ilaria , Buongiorno Nardelli Bruno , Durante Sara , Iudicone Daniele , Kieke Dagmar
Published: March 2022

Subpolar Mode Water (SPMW) represents a variety of near-surface waters that occupy a large volume in the upper 1000 m of the water column of the Subpolar North Atlantic (SPNA). Originating in the eastern and northeastern SPNA through late winter water mass formation, SPMW acts as a precursor to the formation of the North Atlantic Deep Water, which is an important ingredient of the Atlantic Meridional Overturning Circulation (AMOC). In this study we address spatial and temporal changes in the SPMW layer thickness and volume. We relate these changes to variability in the water mass formation estimated through the net subduction/obduction rates along predefined isopycnal bins between σθ = 27.05 kg m-3 and σθ = 27.55 kg m-3 with 0.1 kg m-3 interval. We use two observation-based gridded 3D products from the Copernicus Marine Environmental Monitoring Service (CMEMS), i.e., the ARMOR3D and the OMEGA3D datasets. The first one provides 3D temperature and salinity fields and is available on a weekly 0.25° regular grid from 1993 to present. The second one provides observation-based quasi-geostrophic vertical and horizontal velocity fields with the same temporal and spatial resolution as ARMOR3D, but for the period 1993 to 2018. Throughout this period of 27 years of observations, the analysis reveals not only pronounced interannual variability in the SPMW formation and volume but also a strong spatial variability, which is caused by spatial changes of the main SPMW formation area within the northeastern SPNA.
The Central and Eastern European Infrasound Network Bulletin
Authors: Bondár István , Šindelářová Tereza , Ghica Daniela , Mitterbauer Ulrike , Liashchuk Alexander , Baše Jiří , Chum Jaroslav , Czanik Csenge , Ionescu Constantin , Neagoe Cristian , Pásztor Marcell , Kouba Dan , Le Pichon Alexis
Published: March 2022

To fill the gap in infrasound network coverage, the Central and Eastern European Infrasound Network (CEEIN) has been established in 2018 with the collaboration of the Zentralanstalt für Meteorologie and Geodynamik (ZAMG), Vienna, Austria; the Institute of Atmospheric Physics of the Czech Academy of Sciences (CAS IAP), Prague, Czech Republic; the Research Centre for Astronomy and Earth Sciences of the Eötvös Loránd Research Network (ELKH CSFK), Budapest, Hungary; and the National Institute for Earth Physics (NIEP), Magurele, Romania. The Main Centre of Special Monitoring National Center for Control and Testing of Space Facilities, State Agency of Ukraine joined CEEIN in 2019. We present the first CEEIN bulletin (2017-2020) of infrasound-only and seismo-acoustic events, and using ground truth events, we demonstrate how adding infrasound observations to seismic data in the location algorithm improves location accuracy. We show how the CEEIN infrasound arrays improve the detection capability of the European infrasound network and identify coherent noise sources observed at CEEIN stations.
Simulation of slow geomorphic flows with r.avaflow
Authors: Mergili Martin , Kellerer-Pirklbauer-Eulenstein Andreas , Bauer Christian , Fischer Jan-Thomas
Published: March 2022

GIS-based open-source simulation tools for extremely rapid mass flow processes such as snow avalanches, rock avalanches, or debris flows are readily available, covering a broad range of complexity levels – e.g., from single-phase to multi-phase. However, these tools are not suitable for slower types of mass flows characterized by high viscosities. The conventionally used momentum balance equations for rapid flows often appear numerically unstable for high viscosities, leading to the immediate reversion of flow direction or stopping, without appropriate numerical treatment. GIS-based simulation efforts of slow geomorphic flows are reported in the literature, and open source tools are available for specific phenomena such as glaciers, but no comprehensive and readily usable simulation tools have been proposed yet.

We present a simple depth-averaged model implementation for the simulation of slow geomorphic flows, including glaciers, rock glaciers, highly viscous lava flows, and those flow-type landslides not classified as extremely or very rapid. Thereby, we use an equilibrium-of-motion concept. For each time step, flow momentum and velocity are computed as the equilibrium between accelerating gravitational forces and decelerating viscous forces, also including a simple law for basal sliding. Momentum balances are not carried over from one time step to the next, meaning that inertial forces, which are not important for slow-moving mass flows, are neglected. Whereas these basic principles are applied to all relevant processes, there is flexibility with regard to the details of model formulation and parameterization: e.g., the well-established shallow-ice approximation can be used to simulate glacier flow.

The model is implemented with the GRASS GIS-based open-source mass flow simulation framework r.avaflow and demonstrated on four case studies: an earth flow, the growth of a lava dome, a rock glacier, and a glacier (considering accumulation and ablation). All four processes were reproduced in a plausible way. However, parameterization remains a challenge due to spatio-temporal changes and temperature dependency of viscosity and basal sliding. Our model and its implementation open up new possibilities for climate change impact studies, natural hazard analysis, and environmental education.
Study on slope stability of Maolin area in Kaohsiung (Taiwan) using mineralogical and microstructural techniques
Authors: Hung Ching shiuan , Chen Yen Hua
Published: March 2022

The Wanshan tribe is in the Maolin district of Kaohsiung City in Taiwan. This area belongs to the Chaochou Formation within the Lushan Slate Belt. Its terrain is hillslope and stream terrace with slate and argillite rock-composition. The geological features of this area include slope angle greater than 30 degrees, colluvium, and serious erosion, which had a debris flow during the Morakot typhoon (2009). The area is currently classified as a massive potential landslide region and is still in a slow slip (creeping).

In this study, mineralogical and microstructural techniques were applied to investigate the slope stability of this area, e.g. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), optical microscope (OM), scanning electron microscopy (SEM), and microcomputer tomography (micro-CT). A 40 m-depth rock-core was drilled at the field site and the core samples were prepared for related measurements and experiments. The rock-core composed of fresh slates and weathered slates.

Based on XRD and OM analyses, the mineral phases in this area included quartz, illite, chlorite, muscovite and feldspar. The weathered core-sample had a more content ratio of clay minerals compared to that in the fresh slate core-sample. The FTIR results exhibited that the weathered core-samples had a higher water content than that in the fresh slate samples. With the help of SEM and micro-CT, it can be observed that the weathered core-sample had many longitudinal fractures, however, the fresh slate core-sample just had the slate cleavage.

It is so interesting that the lithology of rock-core changed into a dense fresh slate at the depth of 20 m; it suggested that this rock-layer is more impermeable to water. The weathered rock is favorable for water infiltration and then induced rock weathering, which could weaken the mechanical strength of this rock-layer. It is known that the lithology variation/change of rock-layers preferred to accumulate water, and it was easy to become a weak interface-layer. Therefore, we should pay attention to the fluctuation of groundwater level in this area and the drainage system needs to be well done.
The role of biosolid derived compost on cation exchange
Authors: Nguyen Thao Bich , Arye Gilboa
Published: March 2022

In most productive agricultural soils, organic matter (OM) makes up a small percentage (3-6%) but plays a vital role in biogeochemical processes, particularly nutrient availability and soil structure stability as influenced by cation exchange processes. The loss of soil OM is one of the most severe threats to much of the World's arable areas. Thus, OM application (e.g. biosolids, livestock manure, and compost) is widely recommended due to its cost-effectiveness, and high macro- and micro-nutrient contents. In this regard, the intrinsic properties of soil OM in conjunction with cation exchange processes have not been thoroughly addressed. Therefore, it is essential to quantify cation exchange in biosolids and biosolid-amended soils, specifically, the competitive cation exchange process. The main objective of this study was to evaluate cation exchange equilibria on biosolid-derived compost in binary cation solutions. The target cations were NH4+, K+, Na+, Ca2+, and Mg2+, which are relevant to plant nutrient availability and the efficiency of remediation strategies for saline and sodic soils. Here, binary exchange isotherm experiments were conducted in which the biosolid was pre-saturated with Ca2+. The selectivity coefficient was calculated from the measured exchange isotherms. The results showed that the shape of the exchange isotherm curves and the amount of cations exchanged varied in different binary systems. The biosolid characteristics, as well as the preference of particular cations to the biosolid, will be presented and discussed.

Keywords: soil organic matter, biosolid, cation exchange, selectivity coefficient.
Heavy Metal and Rock in Space: Cluster RAPID Observations
Authors: Haaland Stein , Daly Patrick W. , Vilenius Esa , Krcelic Patrik
Published: March 2022

Metallic and silicate ions carry essential information about the evolution of the Earth and near-Earth small bodies. Despite this, there has so far been very little focus on ions with atomic masses higher than oxygen in the terrestrial magnetosphere. In this presentation, we report on abundances and  properties of energetic ions with masses corresponding to that of silicon (Si) and iron (Fe) in Earth's geospace.  The results are based on a newly derived data product from the Research with Adaptive Particle Imaging Detectors (RAPID) on Cluster. We find traces of both Si and Fe in all of the regions covered by the spacecraft, with the highest occurrence rates and highest intensities in the inner magnetosphere. We also find that the Fe and Si abundances are modulated by solar activity. During solar maximum, the probability of observing Fe and Si in geospace increases significantly. On the other hand, we find little or no direct correlation between geomagnetic activity and Si and Fe abundance in the magnetosphere. Both Si and Fe in the Earth's magnetosphere are inferred to be primarily of solar wind origin, as indicated by correlations with heavy ion observations from the ACE spacecraft at L1. Sputtering off the Moon is another possible source of the observed heavy ions.
Nighttime temperature and optimal photosynthetic capacity over the past fortnight jointly control the acclimation of leaf respiration
Authors: Ren Yanghang , Wang Han , Harrison Sandy P. , Prentice I. Colin , Reich Peter B. , Smith Nicholas G. , Stefanski Artur
Published: March 2022

Leaf dark respiration (Rd) accounts for approximately 50% of plant respiration. The acclimation of plant respiration to temperature weakens the positive feedback to global warming. Most existing land surface models (LSMs) adopt an empirical leaf respiration scheme with a constant Rd25 (leaf dark respiration rate at 25°C) for each vegetation type, since there is no acceptable theory of Rd acclimation and how it varies temporally and spatially. Here we propose that Rd25 adjusts to prior nighttime temperature (Tnight) to maintain the ratio of Rd to photosynthesis capacity (Vcmax) approximately constant. To test this hypothesis and explore the time scale of acclimation, we predict Rd25 over different time windows and evaluate these predictions using data from 14 sites from two datasets (Boreal Forest Warming at an Ecotone in Danger (B4WarmED) experiment and Leaf Carbon Exchange dataset (LCE)), one of which provides measurements through time and the other across spatial gradients. Predictions that account for the combined effects of Vcmax and Tnight have better predictive power for all species (mean R2=0.4) than considering the effect of one factor alone. Predictions of acclimation on different timescales show that Vcmax and Tnight averaged over the past fortnight explain the most variation in observed Rd25. These results could provide an alternative solution to the leaf respiration schemes used in LSMs.
Assessing Machine Learning algorithms to fill gaps of daily evapotranspiration measured in a citrus orchard using a combination of agro-meteorological and remote sensing data
Authors: Ippolito Matteo , De Caro Dario , Provenzano Giuseppe
Published: March 2022

The knowledge of crop evapotranspiration is crucial for several hydrological processes, including those related to the management of agricultural water sources. Among indirect methods to estimate actual evapotranspiration, ETa, the measurements of latent heat fluxes acquired with Eddy Covariance (EC) tower have been largely used. However, the malfunctioning of the commonly installed sensors can cause the loss of data, compromising the temporal continuity of the acquisitions. Machine learning (ML) algorithms can represent a powerful tool to perform gap-filling procedures and provide accurate predictions of missing data.

The objective of the research was to assess different ML algorithms to fill daily actual evapotranspiration measurements acquired in a Mediterranean citrus orchard, by using a combination of in-situ or ERA5-Land reanalysis agro-meteorological data and two vegetation indices (VIs) retrieved by the Sentinel 2 platform.

The experimental layout consisted of a standard weather station, an EC tower containing an open-patch gas-analyzer, a three-dimension sonic anemometer, a four-component net radiometer. Four “drill and drop” probes (Sentek Pty Ltd, Stepney, Australia) were also installed in the field. Six different algorithms of machine learning were tested, using in input, as climate variables the global solar radiation, mean air temperature and relative air humidity, as well as two VIs (NDVI e NDWI) characterized by a spatial resolution of 10 m and, finally, the average soil water content measured in the root zone (0-50 cm). The number of daily ETa measurements, acquired from March 2019 to September 2021, resulted in about 70% of the total days of the period; the missing data were caused by the malfunctioning of installed instruments, which occurred during the lockdown restrictions caused by the pandemic.

Among the different ML algorithms, the best performance was associated with the Gaussian Process Regression (GPR) based on nonparametric kernel probabilistic function (Rasmussen, 2006) when, with the other input variables, the average soil water content was included; in this case, the values of root mean square error (RMSE) and determination coefficient (R2) associated with the cross-validation resulted equal to 0.42 mm/d and 0.85, respectively. However, suitable results were also associated with the GPR model, when assuming, as input variables, on-site meteorological data and VIs (RMSE=0.49 mm/d and R2=0.78), or when considering the ERA5-Land meteorological variables (RMSE=0.56 mm/d and R2=0.73). The joint use of agro-meteorological and remote sensing data, associated with a GPR model, can therefore provide the opportunity to fill the gaps of ETa time-series.
Reconstructing the moisture availability of Central Mexico over the past 500,000 years using borehole logging data
Authors: Abadi Mehrdad , Zeeden Christian , Ulfers Arne , Wonik Thomas
Published: March 2022

Assessing the moisture history of Central Mexico reveals the responses of tropical areas to variation in past climate. Central Mexico has several long-lived lakes, which are potentially important paleoclimate archives. Lake Chalco in Central Mexico contains a ~300 m lacustrine sequence, which were deposited over a period of ~500,000 years. We conducted Spectral Gamma Ray (SGR) measurements across the lacustrine deposits of Lake Chalco to reconstruct the moisture availability over the past. The SGR data reflect the presence of naturally occurring radioactive elements including potassium (40K) and the equilibrium decay series of uranium (U) and thorium (Th). Natural sources of gamma radiation in lacustrine deposits of Lake Chalco are from volcanic ash deposition and detrital input of eroded sediments containing radioactive elements. However, redox conditions in the lake water influence the mobility of soluble U through conversion to more stable reduced phases. To extract the primary non-volcanic signals, we detected and removed signals from embedded tephra layers in the lacustrine sediments of Lake Chalco. We developed a moisture proxy by calculating the probability of authigenic U distributed across the lake sediments. We expect that an increasing U content in proportion to the content of K and Th indicate redox conditions in lake bottom water as a result of rising lake level. To evaluate this moisture proxy, we examined differences in the percent of the diatom species that are indicative of a deeper lake from literature. Results suggest that Lake Chalco likely formed prior or within MIS13, and the lake level rose gradually over time until the interglacial period of MIS9. Moisture levels are higher during the interglacial than glacial periods and interglacial periods show higher moisture variability. While glacial periods have less moisture, two periods, MIS6 and MIS4, still have a higher likelihood of authigenic U and more moist conditions. In order to determine potential regulators of moisture, we compared models containing the drivers of Earth’s orbital cycles, carbon dioxide and sea surface temperature. Carbon dioxide, eccentricity, and precession are all key drivers of the moisture content of Lake Chalco over the past 500,000 years. High levels of atmospheric CO2 have a positive effect on the moisture in Mexico while eccentricity and precession consistently have negative effects on lake moisture. Obliquity and δ18O have weaker effects on moisture in Mexico, probably due to the equatorial high-altitude region far away from poles, oceans and ice sheets.
Sensing individual components of atmospheric mass variability with future satellite gravimetry missions 
Authors: Dobslaw Henryk , Balidakis Kyriakos
Published: March 2022

Observations of the time-variable gravity field by means of GRACE and GRACE-FO are long known to be impacted by atmospheric non-tidal mass variability. To avoid aliasing artifacts from high-frequency mass variations into the Level-2 monthly gravity fields that are being calculated routinely out of the mission data, the impact of atmospheric mass variations is reduced with a time-variable background model based on ECMWF operational and reanalysis data (i.e., AOD1B). Future satellite constellations based on low-low satellite-to-satellite tracking in a double pair configuration as currently jointly explored by NASA and ESA within the MCM/MAGIC mission concept have the ability to directly observe atmospheric mass variations down to much shorter time-scales so that (possibly erroneous) background models might not be necessary anymore in the future. 

By means of two modern global atmospheric reanalyses ERA5 and MERRA2, we will assess the impact of non-tidal atmospheric mass variability for both the total atmospheric signal as well as its individual components (i.e., dry atmospheric mass; water vapor partial pressure; atmospheric moisture flux divergences, etc.). Results will be presented for different frequency bands (< 3days; 3-10 days; 10-30 days) and contrasted against the differences between ERA5 and MERRA2 as a measure of the present-day uncertainties in large-scale atmospheric modelling. This analysis will allow to explore the potential contribution of gravimetric satellite observations to future atmospheric reanalysis efforts -- or eventually even operational numerical weather prediction as long as the latency of satellite gravimetric data can be drastically improved.
Deformation mechanisms along the Main Marmara Fault around the ICDP-site GONAF
Authors: Scheck-Wenderoth Magdalena , Cacace Mauro , Heidbach Oliver , Bohnhoff Marco , Nurlu Murat , Fernandez Terrones Naiara , Bott Judith , Gholamrezaie Ershad
Published: March 2022

The Main Marmara Fault (MMF) in NW Turkey south of Istanbul is a segment of the North Anatolian Fault Zone (NAFZ) that constitutes a right-lateral continental transform fault.  Several well-documented strong (M7+) earthquakes indicate that the MMF poses a great risk to the Istanbul metropolitan region. A 150 km long stretch of the MMF has not ruptured since 1766 and the recurrence time of 250 yrs for M7+ events derived from historical records indicate that the fault is overdue. We introduce a new project addressing how the rheological configuration of the lithosphere in concert with active fluid dynamics within the crust and mantle influence the present-day deformation along the MMF in the Marmara Sea region. We test the following hypotheses: (1) the seismic gap is related to the mechanical segmentation along the MMF which originates from the rheological configuration of the crust and lithosphere; (2) variations in deformation mechanisms with depth in response to variations in temperature and (fluid) pressure exert a first-order control on the mode of seismic activity along the MMF, and, (3) stress and strain concentrations due to strength and structural variability along the MMF can be used as an indicator for potential nucleation areas of expected earthquakes. To assess what mechanisms control the deformation along the MMF, we use data from the ICDP GONAF observatory (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) and a combined work flow of data integration and process modelling to derive a quantitative description of the physical state of the MMF and its surrounding crust and upper mantle. Seismic and strain observations from the ICDP-GONAF site are integrated with regional observations on active seismicity, on the present-day deformation field at the surface, on the deep structure (crust and upper mantle) and on the present-day stress and thermal fields. This will be complemented by numerical forward simulations of coupled thermo-hydraulic-mechanical processes based on the observation-derived 3D models to evaluate the key controlling factors for the present-day mechanical configuration of the MMF and to contribute to a physics-based seismic hazard assessment.
Earthquake nucleation – viewpoint of dynamically growing asperities controlled by the fracture cohesion-zone and frictional shear
Authors: Dahm Torsten , Hainzl Sebastian
Published: March 2022

It has often been suggested that the frictional instability on small fault patches can lead to slow but accelerated creep and growth, which may explain the nucleation of earthquake rupture. Because of the small size of the asperity at depth, the nucleation process is difficult to verify by observations and its possible role for earthquake generation is still debated.

While most earthquake nucleation models are of complex geometry and assume that the asperity itself is static while its stress is increasing, we suggest a concept where the cohesion zone of a fault patch grows steadily and develops a self-induced high stress behind the crack tip. We show that a slip-weakening and velocity strengthening constitutive relation can generate the high stress cohesion zone. The aseismic growth of the asperity is accelerated, and the point to nucleate into a catastrophic rupture depends on the ambient stress on the fault and the stress drop in the centre of creeping segment. Interestingly the model predicts that earthquakes on faults with subcritical and small ambient stress will start with more energetic ruptures, as their Griffith energy is larger. This is unexpected and may question the common assumption that largest earthquake are triggered if the fault is critically stressed and the last earthquake occurred a long time before the average recurrence period.

Our fracture mechanical, theoretical asperity model is unconventional and questions established ideas on earthquake generation. We discuss the possible consequences and the postulated, testable predictions of the model to motivate laboratory and field experiments.
Global Teleconnections between QBO Dynamics and ITM Anomalies
Authors: Yudin Valery , Goncharenko Larisa , Karol Svetlana , Lieberman Ruth , Liu Hanli , McInerney Joe , Pedatella Nicholas
Published: March 2022

The importance of the realistic predictions of the climate variability in the whole atmosphere system, vertical and horizontal teleconnections between the stratospheric QBO and SAO and ITM dynamics are now well recognized. The paper presents a brief summary of the QBO impact on the MLT neutral dynamics seen from the last decade of ITM observations and predictions by two whole atmosphere models constrained in the lower atmosphere by GEOS meteorology of NASA/GMAO. We present the initial modeling and observational evidences that the QBO-related variations in the MLT thermal tides can modulate the equatorial ionospheric anomaly wave-4 and wave-3 longitudinal structure affecting the ITM system on regional scales. Several hypotheses about the influence of the stratospheric QBO on the ionosphere due to the combined influences of migrating and non-migrating tides will be suggested based on the preliminary multi-year observational analysis of TEC data.   
Detection Limits and Near-Field Ground Motions of Fast and Slow Earthquakes
Authors: Kwiatek Grzegorz , Ben-Zion Yehuda
Published: March 2022

We investigate theoretical limits to detection of fast and slow seismic events and discuss spatial variations of ground motion expected from an synthetic family of M6 earthquakes at short epicentral distances. The performed analyses are based on synthetic velocity seismograms calculated with the discrete wavenumber method assuming seismic velocities and attenuation properties of the crust in Southern California. The examined source properties include  magnitudes ranging from M -1.0 to M 6.0, static stress drops (0.1-10 MPa), and slow and fast ruptures (0.1-0.9 of shear wave velocity). For the M 6.0 events we also consider variations in rise times producing crack- and pulse-type events and different rupture directivities. We found slow events produce ground motions with considerably lower amplitude than corresponding regular fast earthquakes with the same magnitude, and hence are significantly more difficult to detect. The static stress drop and slip rise time also affect the maximum radiated seismic motion, and thus event detectability. Apart from geometrical factors, the saturation and depletion of seismic ground motion at short epicentral distances stem from radiation pattern, earthquake size (magnitude, stress drop), and rupture directivity. The rupture velocity, rise time and directivity affect significantly the spatial pattern of the ground motions. The results can help optimizing detection of slow and fast dynamic small earthquakes and understand the spatial distribution of ground motion generated by large events.
Mechanical Strength of Southern African’s Lithosphere from a Joint Inversion of Bouguer Gravity and Topography and its Uncertainty
Authors: Sobh Mohamed , Gerhards Christian , Fadel Islam
Published: March 2022

South African lithosphere is a mosaic of the best-preserved and exposed crustal blocks, assembled in the early to late Archean and then modified by a series of major tectono-thermal events, both of Precambrian and Phanerozoic age. Understanding the thermal and compositional structure of the South African lithosphere provides crucial information for the causes and processes of lithospheric stability and modification.

The lithosphere's effective elastic thickness (Te) is a proxy for mechanical strength that can be used to constrain lithospheric rheology and better understand how surface deformation affects deep Earth processes.

In this study, we calculate the admittance and coherence for southern Africa using topography and Bouguer gravity data from the GOCE satellite dataset. The admittance and coherence are then jointly inverted to estimate the spatial variations in southern African elastic thickness, by applying a wavelet transform in a probabilistic Bayesian framework.

Unlike other Cratonic regions, the low effective elastic thickness values and the shallow Curie depth estimated along the Kaapvaal Craton, demonstrate that lithospheric strength is influenced by regional thermo-chemical mantle upwelling dominated by composition, rather than just the continental geothermal state.

The lateral heterogeneity of Te across the Kaapvaal craton indicates that the Kaapvaal may not be a uniformly rigid craton and the modification is related to metasomatism and plume activity.

 
Historical and New Insights into Atmospheric Teleconnection 
Authors: Alpert pinhas , saaroni hadas
Published: March 2022

The “Teleconnection” term in climate studies was defined primarily for widely separated regions. This stems from the basic idea that a physical process, such as an advection or a particular synoptic system, cannot simply explain a relation or a correlation in large distances. Also, in modern times, models more often fail in predicting these remote patterns, particularly with regional models, such as in the hurricane example and its effect on Mediterranean precipitation, explored here. Several teleconnection relations are reviewed, with particular focus on Mediterranean rainfall. It is argued that even with a clear physical process of advection and for a short horizontal scale, ‘teleconnection’ is often not well understood, if the physical mechanism involved is complex, such as in the sub-synoptic scales of aerosol-rainfall interaction or megacities and their potential effects on precipitation. Thus, a broader look at the horizontal scale of teleconnection is proposed where the word TELE is still representing the word ‘far’, as in its Greek origin, but it also includes our limitation in understanding of complex atmospheric relations in various distances.

Furthermore, the hidden assumption that ancients were not able to observe teleconnections is contradicted by an example from ~1800 years ago. In this example, a claim was made in the Talmud that the Euphrates flow is strongly related to the rainfall over the greater Israel region, located at ~700-900 km westward. However, the understanding of this ancient teleconnection was only possible at the 2nd half of the 19th century when the role of synoptic systems in weather, has emerged. 

 

Keywords: Teleconnection, Rainfall, synoptic system, Euphrates discharge, Middle East, Levant, Talmud

 

REFERENCE:

P. Alpert and H. Saaroni, “Historical and New Insights into Atmospheric Teleconnection” Oxford Research Encyclopedia of Climate Science (eds von Storch, H. et al.)  (Oxford Univ. Press, Oxford, 2021).(accepted Aug. 2021)
2020 Vision: Using transdisciplinary approaches in understanding climate (in)action through youth led participation in mitigating hydrological extremes.
Authors: Parsons Katie J. , Jones Lisa , Halstead Florence , Le Hue , Thi Vo Thu , Hackney Christopher R. , Parsons Daniel R.
Published: March 2022

We are the midst of a climate emergency requiring urgent climate action that is, as yet, unforthcoming both on the scale, and at the speed, commensurate with the associated hazard and risk. This paper presents work that considers this current state of inaction and explores how we might understand the underpinning processes of attitudinal and behavioural change needed through the emotional framework of loss.

This inaction is also explored through the additional lens of the year 2020, a year of tumultuous social change created by the COVID–19 pandemic. The article draws parallels with and looks to learn from the ways in which the collective loss experienced as a result of COVID–19 may offer a sense of hope in the fight to adequately address climate change but how meeting the Sustainable Development Goals will require climate injustices to also be addressed. We argue that appropriate leadership that guides widespread climate action from all is best sought from those groups already facing the loss of climate change and therefore already engaged in climate-related social action and activism, including youth and Indigenous peoples.

In this regard we present work from an ongoing project based within the Red River catchment (Vietnam), which is already experiencing enhanced hydrological extremes. Resultant floods, landslides and soil erosion in the upper region is having impacts in communities, whilst relative sea-level rises in the region are affecting the frequency and magnitude of flooding. Our research is working with young people and their communities, alongside social and environmental scientists in partnership, to identify imaginative ways to mitigate these climate change challenges and foster action. The paper will outline how this youth-led approach explores how local, traditional, and indigenous knowledges can develop understandings and strengthen local and societal resilience, incorporating peer-to-peer, intergenerational and cross-/inter-cultural forms of collaborative, and socially just, learning.