bluuebunny/crossref_metadata_2025 huggingface dataset:
Patience Cowie and the Inception of Modern Fault Mechanics:  A Recollection
Authors: Scholz Christopher H.
Published: March 2021

Patience Cowie’s PhD thesis, conducted with me at Lamont, resulted in three papers, published in 1992, that laid the groundwork for the modern era of fault mechanics studies. In the first paper1 she reasoned that a cohesive zone model provided a plausible model of fault grown provided that the width of the cohesive zone scales linearly with fault length. In that case, the Griffith instability is avoided and faults grow self-similarly in quasistatic equilibrium. This model is consistent with the existence of faults of all sizes in which displacement scales linearly with length and the fault grows by the breakdown of a damage zone at the fault tip. In the second paper2 she showed that the then existing data for fault displacement and length were consistent with linear scaling for faults rupturing rock of similar strength. In the third paper3 she combined the earthquake slip/length scaling law with that fault scaling law to show how faults can grow by the accumulation of slip from earthquakes.

In the subsequent thirty years much more work has been done to expand on these themes pioneered by Patience. Here I share some memories of working with Patience in those formative years.

 

1          Cowie, P. A. & Scholz, C. H. Physical explanation for the displacement-length relationship of faults using a post-yield fracture mechanics model. J.       Struct. Geol. 14, 1133-1148 (1992).

2          Cowie, P. A. & Scholz, C. H. Displacement-length scaling relationship for faults: data synthesis and discussion. J. Struct. Geol. 14, 1149-1156 (1992).

3          Cowie, P. A., and Scholz, C.H. Growth of faults by accumulation of seismic slip. J. Geophys. Res. 97(B7), 11085-11095 (1992b).
An improved analytical method for Re-Os isotope analysis and its application to GSJ geochemical reference materials, JCu-1 and JZn-1
Authors: Ogasawara Mizuki , Ohta Junichiro , Ishida Mizuki , Yano Moei , Yasukawa Kazutaka , Kato Yasuhiro
Published: March 2021

The Re-Os isotope system is an effective tool in geological studies, especially in radiometric dating. Since both Re and Os are highly siderophile and chalcophile elements, they tend to be concentrated in various sulfide minerals. Therefore, the Re-Os geochronology has been employed for direct age determination of sulfide mineralization [1, 2]. However, conventional analytical methods for the Re-Os dating are complex and consume much time and cost.

Here we present an improved analytical method for Re-Os in sulfides combined with acid digestion using HClO4 [3] and sparging introduction of Os [4]. In our method, 0.4 g of powdered sulfide was digested by 1 mL of HClO4 in addition to 4 mL of inverse aqua regia in Carius tube, and then the Re and Os isotope ratios were measured by MC-ICP-MS. We applied this method to the GSJ geochemical reference materials JCu-1 (copper ore from Kamaishi mine, northeastern Japan) and JZn-1 (zinc ore from Kamioka mine, central Japan). The Re-Os concentrations of JCu-1 and JZn-1 were 255-280 ppt and 4622-4828 ppt for Re, and 39.7-41.7 ppt and 21.7-30.0 ppt for Os, respectively. Furthermore, the analytical results (Re-Os concentrations, 187Os/188Os, and 187Re/188Os) of separated chalcopyrite from Kamaishi mine showed good agreements with those by the conventional method digesting 0.5 g of sample by 10 mL of inverse aqua regia and measured with N-TIMS.

The new method, using less total volume of acids for sample digestion, enables MC-ICP-MS analysis of sulfides with relatively lower Re and Os concentrations. In addition, for Os isotopes, a sparging method using MC-ICP-MS [4] can be utilized as a simplified analytical procedure. This simplified and improved method may be useful for dating a wider range of sulfide deposits efficiently.

 

1: Nozaki, T. et al. (2013) Sci. Rep. 3, 1889.

2: Kato, Y. et al. (2009) Earth Planet. Sci. Lett., 278, 40-49.

3: Gao, B. et al. (2019) Microchem. J. 150, 104165.

4: Nozaki, T. et al. (2012) Geostand. Geoanal. Res. 36, 131-148.
Detection and quantification of irrigation water amounts at sub-kilometric scale using Sentinel-1 surface soil moisture
Authors: Zappa Luca , Schlaffer Stefan , Nendel Claas , Dorigo Wouter
Published: March 2021

Detailed information about the timing and the amount of water used for irrigation at a high spatial resolution is critical for monitoring and improving agricultural water use efficiency. However, neither statistical surveys nor current remote sensing-based approaches can accommodate this need. Being a natural source of information on the amount of water entering the ground, soil moisture is directly related to irrigation and precipitation. Hence, we present a novel approach based on the TU Wien Sentinel-1 Surface Soil Moisture product to fill this gap, i.e. detect and quantify irrigation water amounts at sub-kilometric scale. Theoretically, irrigation occurring in a specific field should be reflected by a local increase in soil moisture, while surrounding non-irrigated fields exhibit a different behavior.  We harness the spatio-temporal patterns of soil moisture to identify individual irrigation events, and then to estimate irrigation water heights. To retrieve the latter we include formulations of evapotranspiration and drainage as such vertical fluxes have a significant impact on sub-daily soil moisture variations. The proposed approach is evaluated against field scale irrigation data reported by farmers at three sites in Germany with heterogeneous field sizes, crop patterns, irrigation systems and management. 
Our results show that most irrigation events occurring in a field can be detected using soil moisture information at 500 m and 1-3 days resolution, however, lower accuracy is found during the peak of the growing season. The retrieved irrigation water heights increase with the fraction of pixel under irrigation as higher water amounts are expected over largely irrigated pixels. Finally, irrigation estimates are in agreement with reference data, in terms of temporal dynamics as well as spatial patterns, regardless of field-specific characteristics (e.g. crop type, irrigation system). Unlike most approaches based on microwave soil moisture data, the proposed framework does not rely on additional datasets, which are either locally available or do not even exist at (sub-) kilometric resolution. Hence, the proposed approach has the potential to be applied over large regions with varying cropping systems (e.g. national and even continental scale). 
Analytical expressions for past and present recharge interpretation of radiocarbon data in unconfined aquifers: application to Saharan aquifers
Authors: Chekireb Amine , Goncalves Julio , Hamelin Bruno , Deschamps Pierre , Seraphin Pierre
Published: March 2021

In this study, we developed two-dimensional hydrodynamic age expressions for the free-surface aquifer problem required for radiocarbon data interpretation in terms of recharge. Time-varying recharge is accounted for in fully transient or pseudo-steady state alternative analytical expressions applying to weakly or highly hydraulically reactive unconfined aquifers, respectively. These expressions extending a previous model based on a constant recharge represent a convenient alternative approach to the more complex numerical resolution of a particle tracking problem considering climate variability. An application of the developed expressions was carried out to assess past (40ky) and present recharge rates for the North Western Saharan Aquifers System (NWSAS) and the Djeffara plain (Tunisia-Libya). Using the available 14C data at different outcrops, we obtained local recharge values ranging from 1.27 to 6.86 mm yr-1. A linear relation between the present recharge and the average annual rainfall was obtained and used to identify the regional distribution of the recharge and domain-averaged values. Global values of 1.32 ± 1.47 mm yr-1 for the NWSAS and 3.97 ± 1.46 mm yr-1 for the Djeffara are in excellent agreement with the values obtained by hydrogeological models and derived using Satellite gravity data. The relation between recharge and rainfall obtained here can be used as a first-order estimate for hydrogeological modeling or water management analysis for aquifers in the Saharan area.
Symmetric (inertial) instability in cross-equatorial western boundary currents
Authors: Goldsworth Fraser , Marshall David , Johnson Helen
Published: March 2021

The upper limb of the Atlantic Meridional Overturning Circulation draws waters with negative potential vorticity from the southern hemisphere into the northern hemisphere. The North Brazil Current is one of the cross-equatorial pathways in which this occurs. It is known that upon crossing the equator fluid parcels within this current must modify their potential vorticity, to render them stable to symmetric (inertial) instability and to merge smoothly with the ocean interior.

A hierarchy of models predict the excitement of inertial instability in cross-equatorial flows dynamically similar to the North Brazil Current. A linear stability analysis of a barotropic flow is able to predict the structure and growth rate of the instability. A two-dimensional numerical model verifies these predictions and shows how the instability is able to stabilise unstable potential vorticity configurations. A simplified three-dimensional model demonstrates how large anti-cyclonic rings spun up at the equator entrain waters with negative PV, before the rings themselves become inertially unstable. The high-resolution, observationally constrained, MITgcm LLC4320 model is probed for signs of this instability process.
Sulphur functionalized nanomaterials for monitoring and trapping heavy metals in water environment
Authors: Dodla Ankit , Shukla Shobha , Adyel Tanveer , Saxena Sumit
Published: March 2021

Extensive industrialization and urbanization have adversely affected the quality of consumable water on the earth. The industrial effluents are the major source of micropollutants such as heavy metals, which deteriorates the environment making it toxic to the flora and fauna sustaining in the water. Heavy metals such as lead, cobalt, arsenic, chromium, and mercury are toxic even in trace amounts, whereas presence of higher concentration of iron, cobalt and zinc could be detrimental. Bioaccumulation and hypertoxicity of these heavy metals mark them one of important micropollutants to be monitored. Most of these heavy metals are soft Lewis acid metals such as Ag+, Au+, Cd2+, Hg2+, Pb2+ are considered as thiophilic. In nature, proteins responsible for metabolizing and binding to heavy metals are rich in sulphur functionalized groups such as cysteine and glutathione. This work will address the various sulphur functionalized nanomaterials which are inspired by nature will enhance the monitoring and trapping of heavy metals in water environment.
Trace elements of organic wastes with a potential use for improving soils
Authors: Navarro Pedreño Jose , Rodríguez Espinosa Teresa , Gómez Lucas Ignacio , Jordán Vidal Manuel M. , Almendro Candel María Belén
Published: March 2021

There are a lot of materials, i.e. organic and inorganic wastes that can be use to improve soil properties, and also can be part of Anthrosols and Technosols, both defined in the World Reference Base for Soil Resources (2015) as soils with strong human influence. The first one, associated to intensive agriculture and comprise soils that have been modified profoundly through human activities, such as addition of organic or mineral material. The second one combine soils whose properties and pedogenesis are dominated by their technical origin. Technosols contain a significant amount of artefacts (something in the soil recognizably made or strongly altered by humans or extracted from greater depths) or are sealed by technic hard material (hard material created by humans, having properties unlike natural rock) or contain a geomembrane. The use of organic wastes to improve their properties or being part of the components forming a Technosol can increment the presence of trace elements which an alteration of their composition. These trace elements could suppose an environmental risk as a source of pollution affecting soil, water and biodiversity. The objective of this work was to determine the trace element composition of five organic wastes (pine bark, palm leaf, hay straw, almond pruning, pomegranate fruit skin) in order to know their composition and possible effects when they will be used for Technosol making or to improve soil properties. The composition of them varied. Five samples from each waste were digested by using H2O2+HNO3 in microwave furnace and after that, elemental composition was measured by Inductively Coupled Plasma Optical Emission Spectroscopy. As, Cd, Co, Ni, Pb and V were under the limit of detection (we consider for all the elements a general limit of detection to compare all of them of 2 micrograms per litter; for this technique the limit varies from 0.03 to 1.5 micrograms per litter depending on the element). The elemental composition of the wastes showed that Ba, Cr, Cu, Li, Mn, Mo, Se and Zn were below 20 mg/kg dw in all of them. The rest of the elements presented concentrations over 20 mg/kg dw. In general, major differences were found in some trace and major elements: B and Ca in pine bark, K in pomegranate skin, Mg and Na in palm leaf and Sr in almond pruning. As a conclusion, the elemental composition of these wastes would be considered when a Technosol will be prepared including these materials or when they will be used as soil amendments.
Surface energy balance and climatology changes from WRF simulations with different horizontal resolutions and soil configurations 
Authors: García-García Almudena , Cuesta-Valero Francisco José , Beltrami Hugo , González-Rouco Fidel , García-Bustamante Elena
Published: March 2021

Interactions between the lower atmosphere and the shallow continental subsurface govern several surface processes important for ecosystems and society, such as extreme temperature and precipitation events. Transient climate simulations performed with climate models have been employed to study the water, mass and energy exchanges between the atmosphere and the shallow subsurface, obtaining large inter-model differences. Understanding the origin of differences between climate models in the simulation of near-surface conditions is crucial for restricting the inter-model variability of future climate projections. Here, we explore the effect of changes in horizontal resolution on the simulation of the surface energy balance and the climatology of near-surface conditions over North America (NA) using the Weather Research and Forecasting (WRF) model. 
We analyzed an ensemble of twelve simulations using three different horizontal resolutions (25 km, 50 km and 100 km) and four different Land Surface Model (LSM) configurations over North America from 1980 to 2013. Our results show that increasing horizontal resolution alters the representation of shortwave radiation, affecting near-surface temperatures and consequently the partition of energy into sensible and latent heat fluxes. Thus, finer resolutions lead to higher net shortwave radiation and temperature at high NA latitudes and to lower net shortwave radiation and temperature at low NA latitudes. The use of finer resolutions also leads to an intensification of the terms associated with the surface water balance over coastal areas at low latitudes, generating higher latent heat flux, accumulated precipitation and soil moisture. The effect of the LSM choice is larger than the effect of horizontal resolution on the representation of the surface energy balance, and consequently on near-surface temperature. By contrast, the effect of the LSM configuration on the simulation of precipitation is weaker than the effect of horizontal resolution, showing larger differences among LSM simulations in summer and over regions with high latent heat flux. This ensemble of simulations is then compared against CRU data. Comparison between the CRU data and the simulated climatology of daily maximum and minimum temperatures and accumulated precipitation indicates that enhancing horizontal resolution marginally improves the simulated climatology of minimum and maximum temperatures in summer, while it leads to larger biases in accumulated precipitation. The larger biases in precipitation with the use of finer horizontal resolutions are likely related to the effect of increasing resolution on the atmospheric model component, since precipitation biases are similar using different LSM configurations.
Imprint of intrinsic ocean variability on ocean heat content and thermosteric sea level over 2005-2015
Authors: Llovel William , Kolodziejczyk Nicolas , Penduff Thierry , Molines Jean-Marc , Close Sally
Published: March 2021

Ocean warming accounts for more than 90% of the net Earth energy imbalance. As oceans warm, sea level is rising due to the expansion of seawater. Therefore, estimating ocean heat content (OHC) and thermosteric sea level (TSL) appears of great importance to assess the impact of the on-going global warming.  Different research groups have estimated such climate variables for years now and even routinely (Boyer et al., 2016). These climate variables are derived from in situ temperature measurement at different depths with uneven spatial coverage. Two main sources of uncertainties are attributed to the evolving technology of temperature probes and to the uneven spatio-temporal distribution of in situ measurements (Boyer et al., 2016). A large ensemble of forced eddy-permitting ocean simulations revealed the existence of another uncertainty of regional OHC trend estimates (Sérazin et al 2017): a substantial intrinsic variability emerging from oceanic nonlinearities generates random multi decadal trends, which can mask its atmospherically-forced counterpart. This intrinsic variability can also leave a large imprint on regional sea level trends over the altimetry period (Llovel et al., 2018; Penduff et al., 2019). Less attention has been paid for estimating the imprint of such intrinsic ocean variability in OHC and TSL change associated with the uneven spatial coverage of in situ records. In this study, we investigate the imprint of ocean intrinsic variability and of the uneven distribution of in situ records on OHC and TLS change, by taking advantage of this large ensemble simulation. To do so, we extract synthetic in situ temperature profiles from the simulations in space, time and depth. We then interpolate these synthetic profiles using ISAS (Gaillard et al. 2016) to estimate both the imprint of intrinsic ocean variability and the uneven distribution of in situ data to OHC change and TSL change from 2005 to 2015.
Carbonatitic REE-Nb-Fe mineralisation in the Palaeoproterozoic Shin Group marble and calc-silicates, Loch Shin, Scotland
Authors: Heptinstall Eleanor , Parnell John
Published: March 2021

Carbonatitic magmatism and metasomatism are rare in Great Britain & Ireland. However, REE-Nb minerals were identified in impure marbles and calc-silicates on the Aird of Shin and Arscaig near Lairg, Scotland. They belong to the Palaeoproterozoic Shin Group, a supercrustal succession of amphibolites, banded silicic gneisses, marbles and calc-silicates. The Shin Group is one of several Palaeoproterozoic to Neoproterozoic marble inliers in the North Highlands of Scotland that present evidence of Caledonian orogen carbonatitic metasomatism. The Proterozoic Bayan Obo ore complex in China was similarly deposited as a dolomite-limestone and later subject to alkali intrusions and carbonatitic metasomatism during the Caledonian orogeny. The Bayan Obo complex hosts REE-Nb-Fe carbonatitic fine-grained dolomites, REE-Nb deficient coarse dolomites, carbonatitic dykes, limestones and dolostones. The Aird of Shin marble mineralogy comprises niobium and tantalum Ca-bearing oxides, scheelite, strontian barite, ilmenite, REE-bearing monazite, REE-epidote and Fe-Mo sulphides in an impure Na-Fe-K calcite fabric. The Arscaig Qtz-Na-K calc-silicates are enriched in REE-bearing monazite, Mg-Fe chlorite and Fe-oxides, with minor REE-bearing xenotime, Mn-Fe garnet and strontian barite. The REE-Nb Aird of Shin marble and the REE-phosphate bearing Arscaig calc-silicates are comparable with carbonatitic mineral phases in the Bayan Obo complex. This study adds support to previous recognition of Caledonian carbonatitic magmatism and carbonatitic metasomatism of Proterozoic limestones and calc-silicates in Scotland. 
From surface processes modelling to high-resolution drilling record: resolving key controls on sediment production and stratigraphic development in the Corinth Rift, Greece
Authors: Pechlivanidou Sofia
Published: March 2021

The Corinth Rift, Greece, is a young (~5 Ma) sea-level controlled rift and one of the most rapidly extending areas on Earth. The unique combination of high strain and sedimentation rate with a closed drainage system and the well preserved syn-rift sedimentary record makes the Corinth Rift an ideal laboratory for understanding interactions between surface processes and tectonics and their implications for syn-rift stratigraphy.

The Corinth Rift has exceptional onshore and offshore field data coverage and as such it represents one of the best natural examples for model calibration. To this end, offshore sediment packages mapped from seismic reflection data were used to validate the surface process model pyBadlands, by comparing the total real and modeled sediment volumes and deposition patterns over the past 130 kyr.  Our results shed light on the impact of tectonic forcing on sediment fluxes by showing that sediment supply to the rift is not primarily controlled by relief development, but instead by tectonically-driven tilting of the landscape. This is the first time that this has been demonstrated for a natural system and challenges the view that relief is a key control on catchment averaged erosion rates.

Moreover, recent drilling data from IODP Expedition 381 in the Corinth Rift generated a complete record of the syn-rift sequence offshore and provided the first age constraints to enable us to resolve sediment accumulation rates with high temporal resolution. The new cores record climate-driven cyclic variations in the basin paleoenvironment, alternating between glacial/isolated and interglacial/marine periods. A key finding is that sedimentation rates are markedly increased during glacial/isolated periods. Furthermore, bed frequency and bed thicknesses show significant stratigraphic variability and highlight the dominance of gravity flow sedimentation which represents > 60% of the total sedimentation during the last glacial-interglacial cycle.

This extraordinary offshore drilling data when combined with surface processes modelling will provide an unprecedented opportunity to address the challenge of resolving tectonic versus climatic controls on sediment production and stratigraphic development within rift basins.
The effect of temperature-dependent thermal parameters in thermal models of subduction zones
Authors: van Zelst Iris , Craig Timothy J. , Thieulot Cedric
Published: March 2021

The thermal structure of subduction zones plays an important role in the seismicity that occurs there with e.g., the downdip limit of the seismogenic zone associated with particular isotherms (350 °C - 450 °C) and intermediate-depth seismicity linked to dehydration reactions that occur at specific temperatures and pressures. Therefore, accurate thermal models of subduction zones that include the complexities found in laboratory studies are necessary. One of the often-ignored effects in models is the temperature-dependence of the thermal parameters such as the thermal conductivity, heat capacity, and density. 

Here, we build upon the model setup presented by Van Keken et al., 2008 by including temperature-dependent thermal parameters to an otherwise clearly constrained, simple model setup of a subducting plate. We consider a fixed kinematic slab dipping at 45° and a stationary overriding plate with a dynamic mantle wedge. Such a simple setup allows us to isolate the effect of temperature-dependent thermal parameters. We add a more complex plate cooling model for the oceanic plate for consistency with the thermal parameters. 

We test the effect of temperature-dependent thermal parameters on models with different rheologies, such as an isoviscous wedge, diffusion and dislocation creep. We find that slab temperatures can change by up to 65 °C which affects the location of isotherm depths. The downdip limit of the seismogenic zone defined by e.g., the 350 °C isotherm shifts by approximately 4 km, thereby increasing the maximum possible rupture area of the seismogenic zone. Similarly, the 600 °C isotherm is shifted approximately 30 km deeper, affecting the depth at which dehydration reactions and hence intermediate-depth seismicity occurs. Our results therefore show that temperature-dependent thermal parameters in thermal models of subduction zones cannot be ignored when studying subduction-related seismicity. 
Impacts of long-term warming and enhanced nitrogen and sulfur deposition on carbon sink potential in a boreal peatland
Authors: Larmola Tuula , Maanavilja Liisa , Kiheri Heikki , Nilsson Mats , Peichl Matthias
Published: March 2021

In order to assess peatland carbon sink potential under multiple global change perturbations, we examined the individual and combined effects of long-term warming and enhanced nitrogen (N) and sulfur (S) deposition on ecosystem CO2 exchange at one of the longest-running experiments on peatlands, Degerö Stormyr poor fen, Sweden. The site has been treated with NH4NO3 (15 times ambient annual wet deposition), Na2SO4 (6 times ambient annual wet deposition) and elevated temperature (air +3.6 C) for 23 years. Gross photosynthesis, ecosystem respiration and net CO2 exchange were measured weekly during June-August using chambers. After 23 years, two of the experimental perturbations: N addition and warming individually reduced net CO2 uptake potential down to 0.3-0.4 fold compared to the control mainly due to lower gross photosynthesis. Under S only treatment ecosystem CO2 fluxes were largely unaltered. In contrast, the combination of S and N deposition and warming led to a more pronounced effect and close to zero net CO2 uptake potential or net C source. Our study emphasizes the value of the long-term multifactor experiments in examining the ecosystem responses: simultaneous perturbations can have nonadditive interactions that cannot be predicted based on individual responses and thus, must be studied in combination when evaluating feedback mechanisms to ecosystem C sink potential under global change.
Persistently high CH4 emissions 10 years after restoration: The necessity for long-term observations when measuring GHG emissions of transitional systems
Authors: Antonijevic Danica , Vaidya Shrijana , Vincenz Claudia , Jurisch Nicole , Pehle Nathalia , Albiac Borraz Elisa , Gusovius Bertram , Lück Matthias , Augustin Jürgen , Hoffmann Mathias
Published: March 2021

When drained for e.g. agricultural use, natural peatlands turn from a net C sink to a net C source. It is therefore suggested that restoration of peatlands, despite of increasing CH4 emissions, holds the potential to mitigate climate change by reducing their overall global warming potential. The time span required for this transition, however, is fairly unknown. Moreover, greenhouse gas emission measurements from peatlands are often limited to a couple of years only. This is problematic in so far, as most peatland ecosystems are in transitional stage due to restoration related disturbances (e.g. enhanced water table) and global climate change. This might affect GHG emissions in one way or another which emphasizes the necessity of longer-term observations to avoid misinterpretations and premature conclusions.       
Exemplary for that, we present 14 consecutive years of CH4 flux measurements following restoration at a formerly long-term drained fen grassland within the Peene river catchment (near the town of Zarnekow: 53.52⁰N, 12.52⁰E). Restoration of peatland was done by simply opening the dike. Thus, no water table management was established and water table was strongly fluctuating.  CH4 flux measurements were conducted at two sites (restored vs. non-restored) using non-flow-through non-steady-state (NFT-NSS) opaque chambers. 
Throughout the 14 years study period, distinct stages of an ecosystems transition, differing in their impact on measured CH4 emissions, were observed. During the first two years of the measurement period directly following restoration in autumn 2004, an eutrophic shallow lake was formed. This development was accompanied by a fast vegetation shift from dying off cultivated grasses to submerged hydrophytes and helophytes and evidenced substantially increased CH4 emissions. Since 2008, helophytes have gradually spread from the shore line into the established shallow lake especially during drying years. This process was only periodically delayed by exceptional inundation, such as in 2011, 2012 and 2015, and finally resulted in coverage of the measurement site in 2016 and 2017. While, especially the period between 2009 and 2015 showed exceptionally high CH4 emissions, these decreased significantly after helophytes were established at the measurement site. Hence, CH4 emissions only decreased after ten years transition following restoration and potentially reaching a new steady state.
How Chosen Seismic Fault Picking Strategy Influences Subsequent Fault Analyses: A Case Study from the Horda Platform, with Implications for CO2 storage
Authors: Michie Emma , Mulrooney Mark , Braathen Alvar
Published: March 2021

Significant uncertainties occur through varying methodologies when interpreting faults using seismic data.  These uncertainties are carried through to the interpretation of how faults may act as baffles/barriers or increase fluid flow.  Seismic line spacing chosen by the interpreter when picking fault segments, as well as the chosen surface generation algorithm used, will dictate how detailed or smoothed the surface is, and hence will impact any further interpretation such as fault seal, fault stability and fault growth analyses.

This contribution is a case study showing how picking strategies influence analysis of a bounding fault in terms of CO2 storage assessment.  This example utilizes data from the Smeaheia potential storage site within the Horda Platform, 20 km East of Troll East.  This is a fault bound prospect, known as the Alpha prospect, and hence the bounding fault is required to have a high seal potential and low chance of reactivation upon CO2 injection.

We can observe that an optimum spacing for fault interpretation for this case study is set at approximately 100 m.  It appears that any additional detail through interpretation with a line spacing of ≤50 m simply adds further complexities, associated with sensitivities by the individual interpreter.  Hence, interpreting at a finer scale may not necessarily improve the subsurface model and any related analysis, but in fact lead to the production of highly irregular surfaces, which impacts any further fault analysis.  Interpreting on spacing greater than 100 m often leads to overly smoothed fault surfaces that miss details that could be crucial, both for fault seal / stability as well as for fault growth models.

Uncertainty associated with the chosen seismic interpretation methodology will follow through to subsequent fault seal analysis, such as analysis of whether in situ stresses, combined with increased pore pressure through CO2 injection, will act to reactivate the faults, leading to up-fault fluid flow / seep.  We have shown that changing picking strategies significantly alters the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability, and picking using every line leads to the interpretation of a critically stressed fault.  Alternatively, it is important to note that differences in picking strategy show little influence on the overall predicted fault membrane seal (i.e. shale gouge ratio) of the fault, used when interpreting the fault seal capacity for a fault bound CO2 storage site.
Superheating and cooling rates effects on olivine growth in chondritic liquid: experimental and petrographic approach
Authors: Auxerre Marion , Faure François , Lequin Delphine
Published: March 2021

Chondrules - major constituent of chondrites (primitive meteorites) - belong to the first object formed in the solar system. They are millimetre-sized igneous objects resulting from partial to complete fusion and are divided into main families: non-porphyritic and porphyritic (Gooding and Keil, 1981); the latter one is more abundant in chondrites. This study aims to reproduce thermal histories of macro-porphyritic olivine chondrules (PO) and to better constrain (thermal, temporal) the conditions reigning in the early solar system.

In general, PO chondrules are composed of numerous euhedral crystals of olivine and/or pyroxene suggesting an initially melting below their liquidus temperatures. By contrast, in our study, the macro-porphyritic olivine chondrule displays only one large euhedral olivine. The low number of olivine crystals indicates that chondrule suffered an initial step of superheating, limiting nucleation process (Lofgren, 1988; Hewins et al., 1988). Moreover, embayments observed in euhedral olivine show that olivine crystal began to growth rapidly and then the growth-rate decreased during the cooling. Therefore, our petrographic investigation proposes a first high temperature stage (ΔTliq = +10 °C) followed by a slow cooling.

To test this thermal history, experiments are performed to determine degree of superheating and cooling rate effect (i) on nucleation rate and (ii) on morphology of olivines formed during cooling. Preliminary results seem to confirm that macro-porphyritic olivine chondrules result from the slow cooling of a superheated initial chondritic liquid (Varela et al., 2006). Then these results allow to precise the beginning of the igneous processes (minimum thermal temperature and cooling rate) and to discuss the complete thermal evolution of the chondrule, by considering all other reaction textures observed in this chondrule: peritectic and oxidation reactions, quench texture and aqueous alteration.

 

References:

Gooding et al., (1981) Meteoritics, 16, No. I; Hewins et al., (1988) Meteoritics, 25, 309-318; Lofgren, (1988) Geochim. & Cosmochim. Ada, 50, 1715-1726; Varela et al., (2006) Icarus, 178 (2), 553–569.
Himalayan-Tibetan Erosion is not the Cause of Neogene Global Cooling
Authors: Clift Peter , Jonell Tara
Published: March 2021

Does uplift and erosion of the Himalaya-Tibetan Plateau drive Cenozoic global cooling? We test this classic hypothesis put forward by Raymo and Ruddiman (1992) that suggests enhanced erosion in the Himalaya-Tibetan Plateau drove long-term Cenozoic global cooling through the chemical weathering of siliciclastic sediment. Here we examine three Asian marginal drainage systems (the Indus, Mekong and Pearl) where marine scientific drilling has yielded detailed seismic surveys and geochemical datasets that critically permit sediment mass flux and therefore chemical weathering flux budgets to be made. By compiling suitable bedrock endmember compositions for the fresh bedrock sources, it is possible to calculate the chemical weathering flux and relative CO2 consumption rates for each drainage system into the early Miocene. We correct for evolving provenance of sediment delivered to the offshore and test the sensitivity of our calculations to selected bedrock endmembers, in light of the abundant mafic bedrock exposed Indus and Mekong systems. Appropriate Upper Continental Crust endmembers were further validated using data compiled from the GEOROC database. Regardless of which endmembers were used, calculations demonstrate that the total rate of CO2 consumption decreased by 50% between ~16 and 5.3 Ma, especially within NW Himalaya as onshore erosion slowed and provenance shifted away from mafic arc units in the suture zone. This direct test of the uplift-erosion-weathering hypothesis establishes that chemical weathering fluxes did not increase during the Neogene and cannot be responsible for the drawdown of atmospheric CO2 during that time period. Either additional mechanisms have been driving global cooling since 16 Ma or CO2 consumption via chemical weathering is taking place in other areas outside the Himalaya-Tibetan Plateau.
Incorporation and evaluation of the CRI v2.2 chemical mechanism in UKESM1: An alternative mechanism with updated isoprene chemistry for investigating the influence of BVOCs on atmospheric composition and climate. 
Authors: Weber James , Archer-Nicholls Scott , Abraham N. Luke , Shin Youngsub M. , Bannan Thomas , Schwantes Rebecca , Jenkin Michael , Khan Anwar , Archibald Alexander T.
Published: March 2021

We present the first incorporation and evaluation of the Common Representative Intermediates version 2.2 chemistry mechanism, CRI v2.2, for use in the United Kingdom Earth System Model (UKESM1). Tuned against the MCM v3.3.1, the CRI v2.2 mechanism builds on the previous CRI version, CRI v2.1, in UKESM1 (Archer-Nicholls et al., 2020) by updating isoprene chemistry and offers a more comprehensive description of tropospheric chemistry than the standard chemistry mechanism STRAT-TROP (ST).

CRI v2.2 adds state-of-the-art isoprene chemistry with the introduction of HOx-recycling via the isoprene peroxy radical isomerisation pathway, making UKESM1 one of the first CMIP6 models to include this important chemistry. HOx-recycling has noticeable effects on oxidants in regions with large emissions of biogenic volatile organic compounds (BVOCs). Low altitude OH in tropical forested regions increases by 75-150% relative to ST, reducing the existing model low bias compared to observations. Consequently, isoprene surface mixing ratios decrease considerably (25-40%), significantly improving the model high bias relative to ST. Methane lifetime decreases by 2% and tropospheric ozone burden increases by 4%.

Aerosol processes also differ between CRI v2.2 and ST, resulting in changes to the size and number distributions. Relative to ST, CRI v2.2 simulates an 8% decrease in the sulphate aerosol burden with 20% decreases in the nucleation and Aitken modes. By contrast, the secondary organic aerosol (SOA) nucleation mode burden increases by 11%. Globally, the average nucleation and Aitken mode aerosol number concentrations decrease by 20%.

The differences in aerosol and gas phase chemistry between CRI v2.2 and ST are likely to have impacts on the radiation budget. We plan to use CRI v2.2 and ST to investigate the influence that the chemical mechanism has on the simulated chemistry-climate feedbacks from BVOCs. In addition, CRI v2.2 will serve as the basis for the addition of a scheme describing the formation of highly oxygenated organic molecules (HOMs) from BVOCs, facilitating a semi-explicit mechanism for new particle formation from organic species.
Ombrotrophic peatlands: natural, holistic, integrated, long-term monitoring systems for atmospheric deposition of environmental contaminants to terrestrial and aquatic ecosystems
Authors: Shotyk William , Barraza Fiorella , Belland Rene , Butt Sundas , Chen Na , Devito Kevin , Cuss Chad , Dennett Jacqueline , Frost Lukas , Grant-Weaver Iain , Javed Muhammad , Nielsen Scott , Noernberg Tommy , Oleksandrenko Andrii
Published: March 2021

Sphagnum moss and age-dated peat cores from bogs have long been used to study contemporary and past atmospheric deposition of trace elements (TEs). However, other components of bog ecosystems represent additional scientific opportunities. Snowpack sampling, for example, represents a chance to study winter deposition while providing the perfect matrix for ICP-MS analyses of TEs. The berries that grow in bogs, including blueberry (Vaccinium myrtilloides), cloudberry (Rubus chaemomorus), cranberry (Vaccinium oxycoccus) and lingonberry (Vaccinium vitisidaea), provide insight into the bioavailability of micronutrients (and contaminants) at the surface of the bog, as well as an index of dust deposition onto the fruits themselves. Labrador Tea (Rhododendron groenlandicum) provides similar information, but with greater relevance for Indigenous Peoples, as this is an important medicinal plant for them, along with the Pitcher Plant (Sarracenia purpurea). The acidic, organic-rich waters which represent > 90 % of the mass of these ecosystems, presents an even greater opportunity: the chance to quantify the extent to which aerosols and dusts dissolve, subsequent to deposition from the air. In this study, we present data for TEs in all of these media, with a view to exploring the broader potential of ombrotrophic peatlands as natural, holistic, integrated, long-term monitoring systems. The approach presented here not only addresses our need for information regarding  atmospheric deposition of environmental contaminants to terrestrial ecoystems, but also insight into their release, or potential release, to downstream aquatic ecosystems.
Variability of the atmospheric electric field in the South Atlantic marine boundary layer from the SAIL campaign
Authors: Barbosa Susana , Camilo Mauricio , Almeida Carlos , Amaral Guilherme , Dias Nuno , Ferreira António , Silva Eduardo
Published: March 2021

The marine boundary layer offers a unique opportunity to investigate the electrical properties of the atmosphere, as the effect of natural radioactivity in driving near surface ionization is significantly reduced over the ocean, and the concentration of aerosols is also typically lower than over land. This work addresses the temporal variability of the atmospheric electric field in the South Atlantic marine boundary layer based on measurements from the SAIL (Space-Atmosphere-Ocean Interactions in the marine boundary Layer) project. The SAIL monitoring campaign took place on board the Portuguese navy tall ship NRP Sagres during its circumnavigation expedition in 2020.  Two identical field mills (CS110, Campbell Scientific) were installed on the same mast but at different heights (about 5 and 22 meters), recording the atmospheric electric field every 1-second. Hourly averages of the atmospheric electric field are analyzed for the ship’s leg from 3rd to 25th March, between Buenos Aires (South America) and Cape Town (South Africa). The median daily curve of the electric field has a shape compatible with the Carnegie curve, but significant variability is found in the daily pattern of individual days, with only about 30% of the days exhibiting a diurnal pattern consistent with the Carnegie curve.
The Lagrangian divergence of heat and salt: A new method to determine water mass transformations
Authors: Berglund Sara , Döös Kristofer
Published: March 2021

Water mass transformation is an important part of the Ocean circulation. Lagrangian trajectories can be used to connect pathways with water mass properties such as temperature and salinity. Here, we will introduce the Lagrangian divergence of heat and salt that can be computed using Lagrangian trajectories. This is a new method that can be used to determine where water masses are changing temperature or salinity geographically.
Further, the following two examples on how to use the Lagrangian divergence will be given:

(1) In the Atlantic Ocean water flows northward and transform from warm and saline to cold and fresh. The Lagrangian divergence has been used to show that this cooling and freshening is confined to the North Atlantic Subtropical Gyre.

(2) Waters in the upper limb of the Southern Hemisphere Conveyor Belt circulation converts from cold and fresh to warm and saline as it travels from the Southern Ocean to the tropics. The Lagrangian divergence shows that this warming and salinification are confined to the Antarctic Circumpolar Current, the southern subtropical gyres, and the equator. In this study, the Lagrangian divergence are separated by the mixed layer depth, which distinguishes if a change in heat and salt is driven by internal mixing or air--sea interactions.
Cultivated floodplains of the Cambodian Mekong delta: understanding the changing balance between the flow regime and the agricultural practices
Authors: Orieschnig Christina Anna , Belaud Gilles , Venot Jean-Philippe , Massuel Sylvain
Published: March 2021

On the floodplains of the Cambodian Mekong Delta, rainfed and irrigated dry-season agriculture is a crucial source of revenue for the local population. Traditional rice production is being progressively complemented by the cultivation of higher-value crops like maize, fruit trees and vegetables. Fundamentally, the annual monsoon regime and the resulting flood dynamics determine the framework for these agricultural practices, with a wet season lasting from June to November and a peak high flow reached in September. Rice is cultivated after flood recession in lower-lying areas. On higher terrain, fruit trees and vegetables are widely irrigated by farmers using individual pumps to lift water from large-scale communal channels.

However, in recent years, various drivers of change have impacted these long-established dynamics. Climate change is causing shifting precipitation patterns and a modification of annual flow regimes in the Mekong river and its deltaic distributaries. In addition, the irrigation channel infrastructure is being largely rehabilitated by both local initiatives and international development agencies. These measures are rapidly changing the conveyance network for inundation, drainage, and irrigation on the floodplains, with proportions and consequences which are yet unknown. Finally, land use changes driven by market forces - such as the shift to cash crops like mango trees - are modifying the crop water demand in the area. 

In this context, the present study aims to provide a thorough understanding and quantification of the effects of these changes with regard to crop water requirements, irrigation efficiency, and agricultural productivity. Extensive fieldwork was carried out on a 44-km² area to gather knowledge of agricultural practices (especially irrigation) and to identify the main local hydrological objects and drivers. The land use and seasonal inundation extents were characterized through remote sensing analyses, using optical Sentinel-2 and synthetic aperture radar (SAR) Sentinel-1 images. On that basis, an eco-hydrological model is being developed on the generic software platform OpenFLUID, explicitly representing the hydraulic connections and irrigation decisions. This tool will be used to highlight possible salient control factors for hydrological processes, and to simulate the direct and indirect effects of climate change scenarios, irrigation and water power infrastructure development, and land use changes on local hydrology, irrigation, and agricultural productivity. 