bluuebunny/crossref_metadata_2025 huggingface dataset:
Time dependent slab temperatures, metamorphism, and mechanical properties: Insights from dynamic subduction models
Authors: Holt Adam , Condit Cailey , Turino Valeria , Epstein Gabe , Stoner Ryan , Guevara Victor
Published: February 2023

The thermal structure of subduction zones enacts a first-order control on many geological processes and properties, including the locus and degree of slab devolatilization, and the associated densities and strengths of subducting material. Modeling studies with fixed subduction geometries and plate velocities have been used to map out how various subduction parameters affect the pressure-temperature conditions of slabs and, in turn, the depths of major dehydration reactions. However, there is abundant geological evidence that slab properties, and the associated temperatures, evolve over few-Myr timescales. In this study, we use numerical subduction models to target this time dependence. Specifically, we focus on the styles and drivers of thermal transience and the imprint of this on subducting slab dehydration and slab strength.Specifically, we have developed 2-D and 3-D subduction models that enable slab properties to evolve through time in a dynamically consistent fashion using the ASPECT finite element code1-3. We use these models to investigate: i) the extent to which slab thermal conditions – and the associated metamorphic reactions and slab strength – evolve throughout the lifetime of a subduction zone, ii) the effects of first-order subduction zone properties on this evolution, and iii) the degree to which three-dimensionality (i.e., the presence of a slab edge) impacts this evolution. Regardless of imposed basic subduction parameters (e.g., plate ages, crustal strengths), our model subduction zones exhibit highly time-dependent thermal evolutions. The slab top, for example, exhibits rapid cooling during initiation and slower cooling subsequently, with along-strike temperature variations of up to ~40°C in the 3-D models. This thermal transience has fundamental implications for the geophysical and geochemical evolution of subduction zones; it manifests in a strong time dependence of dehydration depths and magnitudes and, in turn, substantial variability in slab strength.  1: Bangerth, W., Dannberg, J., Gassmoeller, R., & Heister, T. (2020). ASPECT v2.1.0, Zenodo. https://doi.org/10.5281/ZENODO.39246042: Heister, T., Dannberg, J., Gassmöller, R., & Bangerth, W. (2017). High accuracy mantle convection simulation through modern numerical methods - II: Realistic models and problems. Geophys. J. Int., 210(2), https://doi.org/10.1093/gji/ggx1953: Holt, A. F., & Condit, C. B. (2021). Slab temperature evolution over the lifetime of a subduction zone. Geochem., Geophys., Geosys., 22, doi:10.1029/2020GC009476.
Resolving the discrepancy betweenthe seasonal oscillation of Earth's fluid envelope estimated with SLR and that assumed in GRACE
Authors: Argus Donald , Landerer Felix , Wiese David , Blewitt Geoffrey
Published: February 2023

For 25 years, geodesists have inferred that the displacement of the "geocenter" estimated from (SLR) satellite laser ranging represents fluctuation of Earth's fluid envelope relative to solid Earth.  However, SLR determines the displacement of the (CN) center of network of geodetic sites relative to the (CM) center of mass of Earth, consisting of solid Earth, the oceans, the atmosphere, and continental water, snow, and ice. Because solid Earth's surface is deforming in elastic response to the changing load of continental water, atmosphere and oceans, CN only roughly approximates the (CE) center of mass of solid Earth.  In this study, estimate the velocity of CM relative to the (CE) center of mass of Earth by first correcting SLR site displacements (estimated by the International Laser Ranging Service 2020) for their elastic response relative to CE produced by fluctuations of continental water, atmosphere and oceans.  We maintain that by correcting for loading displacements relative to CE, we arrive at an estimate of the displacement of CE.  We find that transforming the SLR series from CN to CE reduces the discrepancy between the seasonal oscillation of Earth's fluid envelope estimated by SLR and that assumed by GRACE (using the technique of Sun et al. 2017) by 40 per cent.  In both SLR and GRACE, a total of 0.5 x 1016 kg of mass moves between hemispheres from southern oceans in August to snow-covered areas in North America and Europe (in particular in Canada and Siberia).  The primary remaining difference between the two techniques is that mass in the northern hemisphere is maximum on February 5 in SLR, 20 days before it is maximum on Feb 25 in GRACE.  Knowing the total transfer of the mass of between hemispheres places a boundary constraint on global models of circulation of water on land and in the oceans and atmospheres (that may be applied to forecasting extreme events such as flooding and drought).
How Do Extreme Summer Precipitation Events Over Eastern China Subregions Change?
Authors: Hao Xin , He Linqiang , Li Hua , Han Tingting
Published: February 2023

Spatiotemporal features of summertime extreme precipitation occurrences (EPEs) over eastern China subregions were captured by using observations from the CN05.1 daily data set and K-means clustering from 1961 to 2018. Five subregions including South China (SC), the Yangtze River Basin (YRB), the HeTao Area (HTA), North China (NC), and Northeast China (NEC) are identified, which is distinct from previous studies. The accompanying evolution of synoptic development are discussed, including the high rates of EPEs transfer from the YRB-type to the SC-type (18%), the HTA-type to the YRB-type (16%), the HTA-type to the NC-type (22%), and the NC-type to the NEC-type (25%). Intrinsic relationships that exist within these types of regional EPEs have not been recorded by previous studies. The intraseasonal evolution of summer EPEs shows a northward migration of the rainbelt influenced by the East Asian summer monsoon system. Moreover, temporal variations of regional EPEs from interannual timescales to long-term trends are examined. 
Orbital variations in the Cenomanian-Turonian, paleoclimatic implications and their relationship with the accumulation of organic-rich intervals in the Middle Magdalena Valley basin, Colombia.
Authors: Valencia Arias Cristian
Published: February 2023

The geometry of the Earth's orbit, and the movements around its axis, result in periodic changes in the solar radiation received by the Earth's surface. These cyclic variations throughout geologic time cause climatic changes that manifest in the hydrologic cycle and atmospheric and oceanic circulation. In turn, these processes result in sedimentary cycles that, although masked by diagenetic processes, record the Earth's orbital rhythm.In the Middle Magdalena Valley Basin (VMM), the Cenomanian-Turonian interval is represented by the rocks of the La Luna Formation, which has a cyclic lithological character, since it consists of intercalation of limestones and shales rich in organic matter. This work seeks to understand the mechanisms that control cyclic sedimentation and organic matter accumulation in the Middle Magdalena Valley basin, as well as to calculate the temporal duration of stratigraphic cycles and determine whether these are related to eccentricity, obliquity, or precession. Also, We will compare with intervals in the tropical belt where previous studies have been carried out to determine whether the observed pattern is local (controlled by basin geometry) or regional (changes in the hydrological cycle caused by orbital parameters).We present lithologic information from the Cenomanian-Turonian interval at Pozo la Luna-1, which has a thickness of 573 ft and consists of a succession of limestones with wackestone texture, locally with foraminiferal packstones, interbedded with thin to medium layers of marls and bentonites (<1cm).Results from the δ13Corg content suggest that OAE2 is recorded in this section and is 69.18 ft thick with δ13C values between -27.18 and -23.94. Four phases of the OAE2 are interpreted: 1) build-up 2) Trough 3) Plateau and 4) Recovery. The time series analyses are developed in the "Astrochron" package (22). They are run on 1146 data of K/Th and Th/K ratios, distributed every 0.5ft. The methods "multi-taper method spectrogram of evolutive harmonic analysis", and "Evolutive average spectral misfit (eASM)" will be applied to detect the presence of cycles along the stratigraphic profile and to estimate their statistical significance compared to a noise level at different confidence intervals.
A three-channel thermal dissociation cavity ring-down spectrometer for the continuous measurement of ambient NO2, total peroxy nitrates and total alkyl nitrates
Authors: Lin Chuan , Hu Renzhi , Xie Pinhua , Zhang Guoxian , Tong Jinzhao , Liu Wenqing
Published: February 2023

A newly constructed thermal dissociation cavity ring-down spectrometer (TD-CRDS) for simultaneous measuring NO2, total peroxy nitrates (ΣPNs) and total alkyl nitrates (ΣANs) was presented. NO2 is detected directly at around 405.46 nm, ΣPNs and ΣANs are detected as NO2 after thermal decomposition at 180℃ and 360℃. The influences of the recombination reaction of RO2 radicals in two different types of heated inlets were discussed and compared, and the thermal decomposition efficiency of PNs was found to be higher with the value of 96% at the heated inlet filled with glass beads than the other (72%). Possible interferences, mainly O3 (including reactions of O3 via NO and O3 via NO2) and NOx (such as the recombination reactions of NOx and peroxy radicals at different thermal temperatures), were quantitatively characterised. The effects were found to be much weaker in the heated inlet filled with glass beads. Thus, a calibration method for measuring ΣPNs and ΣANs was established, especially to solve the accurate measurement of ΣPNs and ΣANs under high amounts of ambient NOx and O3 in China. At the time resolution of 20 s, the detection limits of the TD-CRDS instrument for NO2, ΣPNs and ΣANs are 6 pptv (1σ), 15 pptv (1σ) and 15 pptv (1σ), respectively. Finally, we applied the instrument to the Hefei field campaign, obtaining the concentration distribution and variation characteristics of ΣPNs and ΣANs.  
Assessing spatiotemporal resolution of variables in landscape-scale species distribution models
Authors: Anselmetto Nicolò , Betts Matthew , Weldy Matthew , Tosa Marie , LaManna Joseph , Kim Hankyu , Leismeister Damon , Epps Clinton , Bell David , Schulze Mark , Daly Christopher , Garbarino Matteo
Published: February 2023

The strategic importance of biodiversity conservation is increasing all over the world to face the threats that the global change bring to forest ecosystems. To accomplish that, Species Distribution Models (SDMs) stand as the most employed statistic models in ecological conservation. Nevertheless, explanatory predictors in these correlative models usually consist in free-air climate variables with coarse spatial (>1 km) and temporal (average of several years) resolution. This approach neglects the real habitat conditions experienced by most of the organisms on their life span. Hence, improving the reliability of these ecological models is crucial for biologists, land managers, and policymakers.Our aim was to compare microclimate temperatures derived from 13 years (2010-2022) of below-canopy hourly data loggers to free-air macroclimate derived from a mechanistic downscaling of global reanalysis data at 30 arcsec (CHELSA). We also tested the role of LiDAR-derived vegetation metrics to improve fine-scale SDMs. We developed three sets of predictors based on their temporal resolution: 1) an average across the years of observation based on the general presence or absence of the species, 2) an ensemble of year models (i.e., the average of the probability for each year weighted on its accuracy), and 3) a random year of observation.Using Bayesian Additive Regression Tree (BART) algorithms, we built SDMs for different species of birds, plants, insects, and mammals in a temperate rainforest landscape of the Pacific Northwest (HJ Andrew Experimental Forest, Oregon, United States). We built 12 different modeling frameworks based on the combination between climate input data (microclimate vs macroclimate), vegetation (with vs without), and temporal resolution (average vs ensemble vs random).We measured the distance between the probability distribution obtained from the different combinations using the Kolmogorov-Smirnov distance. We evaluated and compared three accuracy metrics of the models (AUC, TSS, MCS) through a 5-fold spatial block cross-validation. We tested for differences in distance and accuracy both at the taxa level and on ecological traits of the different species (mobility, prevalence, specialization).Preliminary results for bird species showed that temporal resolution was more important than climate datasets when including vegetation variables in the models. Some insect species showed a greater improvement in accuracy for models trained with microclimate compared to models trained with CHELSA.
The Effects of Magnetopause Motion and Substorm Stretching and Dipolarization on Magnetic Fields in the Inner Magnetosphere
Authors: Hsieh Syau-Yun , Sibeck David
Published: February 2023

Increases in the solar wind dynamic pressure compress the magnetosphere, enhance magnetic field strengths and push the magnetopause inward.  Enhanced reconnection on the magnetopause, as might be expected during southward IMF conditions, launches rarefaction waves into the magnetosphere, decreases magnetic field strengths, and erodes the magnetopause inward.  Nightside magnetotail magnetic fields stretch tailward during erosion events and ultimately snap back to dipolar orientations at substorm onset.  The effects can be seen clearly in geosynchronous orbit.  We present a statistical survey of the effects of magnetopause motion and substorm stretching and dipolarization on magnetic fields deep inside both the dayside and nightside magnetosphere using observations from NOAA’s GOES satellites.
Plasma pressure distribution of ions and electrons in the inner magnetosphere during CIR driven storms observed during Arase satellite era
Authors: Kumar Sandeep , Miyoshi Yoshizumi , Jordanova Vania Koleva , Kistler Lynn M , Park Inchun , Shreedevi Porunakatu Radhakrishna , Asamura Kazushi , Yokota Shoichiro , Kasahara Satoshi , Kazama Yoichi , Wang Shiang -Yu , Tam Sunny W. Y. , Mitani Takefumi , Higashio Nana , Keika Kunihiro , Hori Tomo , Jun Chae-Woo , Matsuoka Ayako , Imajo Shun , Shinohara Iku
Published: February 2023

Geomagnetic storms are the main component of space weather. Enhancement of the ring current is a typical feature of the geomagnetic storm and a global decrease in the H component of the geomagnetic field is observed during the main phase of the geomagnetic storm.  The ring current represents a diamagnetic current driven by the plasma pressure in the inner magnetosphere. The plasma pressure is mainly dominated by protons in an energy range of a few to a few hundred keVs during quiet times. The O+ contribution is also important, and sometimes dominates more than H+ during intense geomagnetic storms. However, electron contribution to the ring current is not studied well. Recently, we showed that the electron pressure also contributes to the depression of ground magnetic field during the November 2017 CIR-driven storm by comparing Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. Arase satellite observed 26 geomagnetic storms driven by Corotating Interaction Regions (CIR) during 2017-2021. In this study, we examine statistically the spatial and temporal distribution of ions (H+, He+, O+) and electrons pressure as a function of magnetic local time, L shell and wide range of energies during prestorm, main phase, early recovery and late recovery phase for 26 CIR storms using in situ plasma/particle data obtained by Arase. The results indicate that the electrons (20-50 keV) contribution to the ring current pressure is non-negligible.
A rate-, state-, and temperature-dependent friction law with competing healing mechanisms
Authors: Barbot Sylvain
Published: February 2023

The constitutive behavior of faults is central to many interconnected aspects of earthquake science, from fault dynamics to induced seismicity, to seismic hazards characterization. Yet, a friction law applicable to the range of temperatures found in the brittle crust and upper mantle is still missing. In particular, rocks often exhibit a transition from steady-state velocity-strengthening at room temperature to velocity-weakening in warmer conditions that is poorly understood. Here, we investigate the effect of competing healing mechanisms on the evolution of frictional resistance in a physical model of rate-, state-, and temperature-dependent friction. The yield strength for fault slip depends on the real area of contact, which is modulated by the competition between the growth and erosion of interfacial micro-asperities. Incorporating multiple healing mechanisms and rock-forming minerals with different thermodynamic properties allows a transition of the velocity- and temperature-dependence of friction at steady-state with varying temperatures. We explain the mechanical data for granite, pyroxene, amphibole, shale, and natural fault gouges with activation energies and stress power exponent for weakening of 10-50 kJ/mol and 55-150, respectively, compatible with subcritical crack growth and inter-granular flow in the active slip zone. Activation energies for the time-dependent healing process in the range 90-130 kJ/mol in dry conditions and 20-65 kJ/mol in wet conditions indicate the prominence of viscoelastic collapse of micro-asperities in the absence of water and of pressure-solution creep, crack healing, and cementation when assisted by pore fluids. 
Evaluation of Trade Wind Mesoscale Morphology Evolution and Transitions
Authors: McCoy Isabel L. , Zuidema Paquita , Baidar Sunil , Vogel Raphaela , Eastman Ryan , Schulz Hauke , Brewer Alan
Published: February 2023

Mesoscale cloud morphology patterns in the trade-winds can be grouped by their distinct appearance, size, and radiative properties into four categories: Sugar, Gravel, Flowers, and the synoptically driven Fish. Two occurrence pathways for the larger boundary-layer cloud organization structures were observed during the wintertime 2020 EUREC4A-ATOMIC joint campaign: i) regional Gravel persistence and ii) transitions to Gravel and Flowers from smaller Sugar clouds. Understanding the contributions to larger cloud structure occurrence under pathways of persistence vs. transitions from smaller clouds has utility in predicting their occurrence under climate change. Two EUREC4A-ATOMIC case studies are developed for these respective pathways during multi-day periods when observational platforms were longitudinally distributed across the ocean in parallel with Barbados. A Lagrangian analysis framework is developed by using for/backward 30-hr boundary layer trajectories initialized every 3-hr from the RV Ronald H. Brown (i.e., the mid-evolution reference platform) to connect upwind (e.g., the Northwest Tropical Atlantic Station buoy) and downwind (e.g., the Barbados Cloud Observatory) platforms. This synergistic, multi-platform campaign dataset is supplemented with satellite observations and reanalysis. Motion-stabilized Doppler-lidar observations at the RV Ronald H. Brown and the Barbados Cloud Observatory allow us to examine characteristics of cloud and plume dynamics in addition to the impact of environmental conditions expected to influence cloud organization and development (e.g., surface wind speeds, energy and moisture fluxes, stability, entrainment, large- and meso-scale subsidence, and aerosols). Eulerian differences between key platforms over the campaign period are evaluated and campaign findings are further extended using multi-year Lagrangian analysis.
Characterizing landscape influences on hydrological flow pathways in a peri-urban Mediterranean catchment
Authors: Carneiro Marques Amanda , Ferreira Carla Sofia Santos , Martínez-Carreras Núria , Kalantari Zahra , Guzman Christian David
Published: February 2023

Stable isotopes are an important tool to describe the movement of water through the hydrosphere. They are used as tracers to characterize hydrograph properties. In field studies, stable isotope analyses using hourly and bulk end-member calculations can be used to estimate baseflow/precipitation contributions and to relate hydrograph response to land cover across a watershed. To enable proper planning of paved surface expansions and the nature of storm drainage systems, advanced understanding of the influences of spatial land-use patterns on Mediterranean streamflow regimes are needed to support water management in peri-urban catchments. This study focuses on Ribeira dos Covões, a small peri-urban catchment (around 6 km2), located in central continental Portugal. The catchment is composed of sandstone in the west portion (56%) and limestone in the east portion (41%), with some alluvial deposits (3%) in the main valleys. Flow and precipitation data were collected every five minutes during storms for several years. In 2018, sampling campaigns also included the collection of pre-event, event, and post-event water stable isotopes in different seasons of the year for streamflow at four sites, representing distinct land coverage and lithological landscape combinations. Preliminary results using precipitation and baseflow fraction calculations based on oxygen-18 measurements show that the catchment outlet provides a 49% baseflow contribution (old water fraction) at the beginning of the dry season and 36% in the wet season. An 85% baseflow contribution was estimated for Quinta (mainly forest area in sandstone) during the dry season, and 64-74% for Espírito Santo (largely urban in sandstone) during the wet season. The baseflow contribution at Porto Bordalo (urban area in limestone) is not significant because the flow is controlled by precipitation. Further investigation will involve connecting the results of most recent stable isotope data analyses to the approaches that were used in the past (e.g. separation of baseflow based on low-pass digital filters). Such connection will clarify streamflow response from distinct peri-urban pattern and lithological landscape combinations and their contributions to catchment runoff, aiming to explore the similarities and differences among these methods and quantify the effects of hydrological regime and land use changing patterns over time.
North Atlantic carbon uptake modulates warming rate of the future Northern Hemisphere
Authors: Park In-Hong , Yeh Sang-Wook
Published: February 2023

The North Atlantic is a pacemaker of global climate through the Atlantic meridional overturning circulation (AMOC) and a large anthropogenic carbon uptake. Removal of anthropogenic carbon in the atmosphere by the ocean is key mechanism for modulating warming rate of globe. But, there is a large uncertainty in climate models for simulating AMOC and anthropogenic carbon uptake. To reduce the uncertainties in anthropogenic carbon uptake and its associated Northern Hemisphere surface warming, here we apply an emergent constraint. Sea surface salinity is often used to represent ocean circulations through its strong relationship with ocean density. The results suggest that the present-day sea surface salinity in the North Atlantic subpolar region constrains the future warming of the Northern Hemisphere by modulating anthropogenic carbon uptake in the North Atlantic. Models that generate a present-day higher SSS in the North Atlantic subpolar region systematically tend to a greater uptake of anthropogenic carbon, resulting in a slower warming in the Northern Hemisphere.
Deposition and mineralogy of atmospheric dust at Sierra Nevada and Granada (Andalusia, SE Spain): A single particle perspective
Authors: Sudharaj Aryasree , Orza Jose A.G. , Gomez-Cascales Pedro J. , Suarez Victor M.E. , Milena-Perez Abel , Ferro-Garcia Maria.A. , Kandler Konrad
Published: February 2023

The transport of Saharan dust to the mountain range of Sierra Nevada occurs recurrently as well as episodically and represents an important source of nutrients for its ecosystem. At the same time, the mountain range is also vulnerable to the radiative effects, changing albedo and reduced snow covers attributed to the deposited particles from various natural and anthropogenic sources. A two-year campaign was conducted from June 2018 to August 2019 in the Sierra Nevada at 2500 m MSL (site: Albergue Universitario de Sierra Nevada) and simultaneously samples were also taken from Granada, a city lying in the foothills of Sierra Nevada (site: Faculty of Sciences, University of Granada, 670m MSL). The aim was to deduce the various sources acting over two distinct environments within a short-range distance (22 km). Deposition samples were collected on a carbon substrate using a flat plate sampler (passive method) with a sampling period of 40-72 hours. An average of 10 samples were collected per month from both sites and the current study focuses mainly on the summer months of June, July, and August when episodic dust events were observed. Along with the dust episodes, control days samples were also taken when no rain event or dust event occurred.Single particle microscopy coupled with energy-dispersive X-ray analysis was utilized to get the chemical information on approx. 100,000 single particles over the size range of 0.5- 50 µm projected area diameter. The particles were classified according to a definite set of rules, and the main chemical classes as dust-like, sulphates, and salts-like and their mixtures were derived. Particles which didn’t fit into any of these classes were named ‘other’ classes. The focus of the results includes the relative abundance of these classes and their particle morphology (size and shape) over the two locations affected by different aerosol sources. Furthermore, the characteristics of iron-rich particles and iron content in the other dust particles were also studied given their importance in absorption properties and bioavailability for ecosystems. During the dust event days, the relative number abundance of chemical composition at Sierra Nevada showed >98 % of dust particles enriched in silicate type in the particle size range >1 µm while the <1 µm had a significant percentage in sulphates (>20%). Meanwhile at Granada, even though the dust events had an influence on the composition with higher dust content (>90%) for diameter >5µm modes, the lower size range presented higher fractions of anthropogenic particles consisting of sulphates and other particle types.
Botany on The Moon
Authors: Smith Heather
Published: February 2023

We propose a suite of instruments, Botany on The Moon, designed to investigate the feasibility of plant growth on the Moon. Botany is composed of two single-species plant growth modules (Arabidopsis, & radish) plus two environmental monitoring instruments that record (1) direct and scattered sunlight in the photosynthetically active radiation or wavelengths (termed PAR), and (2) level of cosmic radiation and induced lunar neutrons. Together these four investigations contribute to our understanding of how plants can be grown on the Moon.The core perspective in Botany is that physical experiments are needed to understand plant growth on the Moon. Little is known about plant behavior in reduced (fractional) gravity environments (less than the nominal 1g that occurs on Earth). How biology responds to partial gravity (in combination with radiation effects) remains unexplored.Botany’s primary science goals can be achieved during the sunlit timeframe of a Lunar Day. However, significantly more data and knowledge is gained by extending the growth duration window to approximately 45 Earth days. Hence, Botany is proposing to take advantage of the CLPS provided Survive-the-Night service.  If the CLPS provider is able to provide power for Botany to survive the night, our secondary science goal to determine the feasibility of transitioning the plants from a normal growth phase (at 22oC during the sunlit time) to a slow growth phase (at 5oC during the nighttime), returning to normal growth phase (at 22oC during the second sunlit time) can be achieved. However, all of Botany’s primary science goals can be achieved during the lunar sunlit timeframe, albeit with the loss of data due to the shorter growth duration. The Botany instrument suite including the LPX plant chambers are designed for a 45 Earth-day mission on the Lunar surface, including surviving the 354 hours of the Lunar night. The Botany on The Moon proposed project has a payload mass of ~ 12kg and estimated cost of ~ $11.5 Million U.S. dollars.The 20-person Botany payload team is led by a mid-career women scientist and involves a gender diverse science and engineering team at various stages in their career from 10 institutions located within three countries. The Botany team includes NASA ARC, KIPR (a long-term NASA ARC contract organization), SDL, UNC-G (a minority serving institution (MSI)), a Canadian instrument provided by McMaster University, and a science team from various institutions. Our team combines complimentary skills, mission management experience, and expertise in plant science.
A call to a greater understanding of the magnetic properties of the titanomagnetite series
Authors: Roberts Andrew
Published: February 2023

I have had several surprises in preparing my upcoming book, Mineral Magnetism. One is that knowledge of the magnetic properties of the most important solid solution series in rock magnetism, the titanomagnetite series, is so limited. In this presentation, I provide a perspective on the known magnetic properties of the titanomagnetite series and outline briefly what magnetic properties remain unknown. Much work on the titanomagnetites seems to have been driven by the assumption that magnetite and TM60 are the most important members of this series. Even though this assumption is justified, the full range of titanomagnetite compositions is encountered in igneous rocks and sediments derived from them, which makes it important to develop a modern, comprehensive magnetic property framework for the full titanomagnetite series. The future work suggested here is not limited by the ability to produce stoichiometric powder, polycrystalline, or single crystal samples for any part of the titanomagnetite series. Thus, producing an extensive composition- and particle-size-dependent magnetic property framework for the titanomagnetite series using the full range of modern magnetic methods ought not to be as difficult a task as it would be for many other minerals. Such work is much needed to constrain interpretation of the magnetic properties of natural samples.
Phase field method to model mixed-mode fracturing in fluid saturated porous reservoir
Authors: Kar Swapnil , Chaudhuri Abhijit
Published: February 2023

                                        Hydraulic fracturing is a useful stimulation technique to create cracks in unconventional reservoirs and enhance the effective fluid transmissivity to recover gas from natural gas reservoirs or heat from geothermal reservoirs. However, due to fracturing the overall strength and load bearing capacity of the reservoir is compromised. This may be a serious concern if the reservoir is below a dam or any other massive structures. In such case significant settlement can take place as the result of mixed mode fracturing inside the reservoir which might already have natural fractures. Phase field method based on the formulation of mixed-mode fracturing has been adopted in the present work for modeling fracture propagation in a saturated porous medium when subjected to fluid pressure and increasing overburden load. A numerical method has been developed using Finite element method (FEM) for solving the displacement and damage field, and Finite volume method (FVM) for solving flow field due to its flux conservative nature which is automatically satisfied for each FVM cell. Our FEM code alone has been first validated for modelling mixed mode fracturing considering a single fracture as a notch against the published experimental and numerical results for elastic medium subjected to compressive load. In this method, the notch does not have any material and computational mesh is refined around the notch as commonly done by others. We have later developed an alternative method where the pre-existing crack is modelled as a fully damaged zone. In this method, a structured and uniform grid can be used to obtain same fracturing pattern and load-deflection curve. The alternative method has a few advantages such as it can be easily applied for reservoir with many cracks without any grid refinement around the pre-existing cracks, and it can be easily coupled with FVM code for modeling fluid flow. Our numerical modelling code is capable to simulate fracturing along with the branching and merging effects. We have simulated load-bearing capacity of a fractured reservoir subjected to increasing overburden load. The reservoir is considered to consists of many randomly oriented but poorly connected natural fractures. The load-bearing capacity and load-deflection curves are compared for reservoirs with and without hydraulic fracturing. The simulations have been performed for different set of natural fractures to understand the effect of fracture density and other fracture network properties on the load-deflection curves.
Shifting fire season: who has it worse resprouters, or obligate seeders?
Authors: Thomsen Alexandria , Ooi Mark
Published: February 2023

Fire is a major factor shaping plant communities, and plant species have evolved to persist through a fire regime, broadly characterised by the frequency, intensity, and season of burns typical of their region. However, historical fire regimes are shifting with changing climate and other factors, including increased ignition sources, and implemented fires, producing more frequent burns of varying intensity. As such, seasonality of fire is shifting and despite the effects of fire on plant persistence being well studied, there is still little understanding on the effects of fire season. In this study, we set up two sites with five treatment areas, an early autumn burn, late autumn burn, early spring burn, late spring burn and a control. We surveyed multiple shrub species for impacts of seasonal burns on resprouting vigour and post-fire flowering in the mediterranean region of South Australia. Fire severity was also measured using soil temperatures, canopy cover consumption and minimum twig diameter. We found that fire response to fire season varied between trait type included seed storage type and seed dormancy type. This study highlights the impact of season of fire and that it should be considered when making species management decisions for plant species persistence.
Causes and Consequences of the Prolonged 2020-2023 La Niña
Authors: McPhaden Michael J. , Hasan Nahid , Chikamoto Yoshimitsu
Published: February 2023

The tropical Pacific has witnessed three successive years of unusually cold sea surface temperatures, with peak anomalies in late 2020, 2021 and 2022.  These conditions represent the first "triple dip" La Niña of the 21st century with major climatic impacts felt around the world.  Three year La Niña events are rare but not unprecedented; similar events occurred in 1998-2001 and in 1973-76.  A leading hypothesis for multi-year La Niñas is that they occur on the rebound from preceding extreme El Niños which, through recharge oscillator dynamics, drain the equatorial band of upper ocean heat content leaving a large heat deficit that takes multiple years to recover. The current multi-year La Niña does not conform to this scenario--antecedent conditions in the tropical Pacific in 2019 were characterized by a borderline El Niño that did not lead to a large upper ocean heat content discharge. What caused the this La Niña is thus a topic of considerable interest.  In this presentation we hypothesize that tropical inter-basin interactions were instrumental in initiating and prolonging the event. In particular, we suggest that the event was triggered from the Indian Ocean by a record Indian Ocean Dipole in late 2019, then boosted in 2021 by unusually warm conditions in the tropical Atlantic involving the strongest Atlantic Niño since the 1970s. Whether climate change may have played a role in these developments will be discussed.
Study of morphodynamic change caused by wing dams at large spatio-temporal scale
Authors: Török Gergely T. , Parker Gary
Published: February 2023

Low water depth can be a problem for navigation on large rivers. Since the last century, a frequently-used method of river regulation has been the installation of wing dams (wing dikes, spur dikes, groins). With their help, the riverbed narrowed during low water, which created a greater water depth and a higher water level. However, the narrowed flow also generated a higher bed shear stress, which, due to bed erosion, simultaneously increased the water depth and lowered the water level.
From a flood protection point of view, questions arise as to how wing dam fields change flood levels as a result of the bed change caused by such intervention. The complexity of the answer increases if we examine the problem not only in a cross-section (or short reach scale), but at long scale, as in the case of the Mississippi River, USA, where a system of wing dams hundreds of kilometers long was installed.
We analyzed the problem in two steps: we apply a 3D sediment transport model on a local scale, and the results are then upscaled and implemented in a 1D model to enable study of the problem at large spatio-temporal scale (hundreds of km, several centuries).
Non-uniform Breach Evolution of Landslide Dams during Overtopping Failure
Authors: Lu Xueqiang , Zhou Gordon G.D. , Xie Yunxu , Cui Kahlil F.E. , Tang Hui
Published: February 2023

When natural dams formed by landslides and other mass flow events are breached by the impounded water, soil materials on the surface of the dam are eroded and entrained, creating erosional features that compromise its stability. The failure of landslide dams due to breaching often results in floods and debris flow downstream. Dam breach models often assume that surface erosion is uniform (surface gradient is constant) along the breach channel, despite observations from dam breach experiments that dam surface evolution is more complex. A thorough understanding of dam surface evolution during breaching is essential for assessing flood or debris flow risk, and hence for hazard mitigation. In this study, we use experiments and numerical modelling to investigate the mechanisms that influence the non-uniform morphological evolution of landslide dam breaches. Analog landslide dam models made from poorly sorted, unconsolidated soils are subjected to various inflow discharges. It is found that although the erosion along the bed and sidewalls both affect the evolution of the breach discharge, the bed erosion is what ultimately determines how the dam profiles change during the dam breach. Breaching flow scours the breach channel resulting in erosion rates, described as a function of the difference between the flow shear stress and apparent erosion resistance, that vary at different points along the dam surface. It is found that the soil erodibility remains constant while the apparent erosion resistance increases linearly along the dam surface. The complex dam failure process is numerically modeled using depth-averaged equations which assume that the evolution of the dam profiles results from the coupled effects of erosion, entrainment, and channel bed collapse. Good agreement between the observed and modeled dam profiles demonstrates that the gradual saturation of the breach flow with entrained sediment is responsible for the linear variation of the apparent erosion resistance, which in turn contributes to the formation of the surface non-linear scouring. Our work attempts to understand the mechanisms that control the breach morphology evolution of landslide dams during breaching. A new perspective on the dam erosion process and its relationship with the sediment concentration and the apparent erosion resistance is presented here, making it possible to provide more accurate physically-based outburst flood and debris flow predictions.
3-Year Observation of the CH4 across the sea surface in the Western Arctic Ocean
Authors: Rhee Tae Siek , Kwon Young Shin , Kim Mi-Seon , Dalimore Scott , Paull Charles , Hong Jong Kuk , Jin Young Keun
Published: February 2023

Methane (CH4) is one of the most important greenhouse gases on Earth. Recent finding of the strong CH4 emissions in the Arctic Seas with shrinking the sea ice may amplify the Arctic warming leading to the positive feedback in the Arctic climate. Korea Polar Research Institute (KOPRI) has ongoing interest in Arctic environmental conditions including the potential release of the CH4 from the seabed to the water column and finally, further to the atmosphere. During the last 13 years throughout a series of campaigns on the Korean ice-breaker, R/V Araon, we measured CH4 concentrations at the surface ocean and overlying air in summer season to estimate the emissions from the western arctic seas including the Chukchi Sea, the Beaufort Sea, and the East Siberian Sea. We compare each of these seas and the Central Arctic Ocean covering the deep Arctic Ocean basin. The surface ocean showed super-saturation almost everywhere with respect to the CH4 in the overlying air. Nonetheless, we have insufficient regional coverage to assess any possible saturation anomaly trend in each sea. Flux densities of outgassing CH4 are modestly larger than the global mean value of the continental shelf except for the Central Arctic Ocean where the CH4 emission is slightly lower. Our estimate of CH4 emission in the East Siberian Sea is far larger than other Arctic Seas abiding by the previous observations, but its magnitude is far lower due likely to the distance from the hot spot area. Future methane flux studies should be extended to shallow, nearshore environments where rate of permafrost degradation should be greatest in response to ongoing marine transgression.
Dynamic processes require appropriate methods to capture them: Why in-situ water stable isotope monitoring needs to become a standard method in forest hydrological research
Authors: Beyer Matthias , Kuehnhammer Kathrin , van Haren Joost , Kuebert Angelika , Birkel Christian , Sanchez-Murillo Ricardo , Marshall John
Published: February 2023

As a consequence of global change, forests worldwide are undergoing a restructuring process. The expectations for forests of the future are ambitious: Providing resilient forest ecosystems that capture large amounts of carbon but also provide stable groundwater recharge rates. To balance the interests of both forestry and water management authorities, scientists and practitioners need to be able to investigate and predict which forest types and combinations of tree species are most likely to fulfill these needs.Methods based on the analysis water stable isotopes have been used extensively for studying water uptake depths of vegetation, groundwater recharge, transit times, and water sources in general. Despite being arguably the superior tool when not only amounts but also knowledge of the sources of an (eco-)hydrological flux are needed, the highly dynamic nature of water transport processes within the soil-plant-atmosphere continuum (SPAC) could hardly be captured in the past. With the advent of  laser spectroscopy in the last decade, we are now able to measure water stable isotopes continuously and in all compartments of the SPAC.In this keynote, we present and review the most recent advances (2016-now) of combined soil and plant in-situ water isotope measurements carried out in different ecosystems worldwide. We then critically discuss the gain in process-understanding of in-situ monitoring approaches and demonstrate how in-situ methods could be integrated with traditional and novel methods to advance forest hydrology.In-situ and semi-in-situ (i.e., sampling of water vapor) water stable isotope methods have been greatly improved within the last five years. Initial disadvantages (e.g., comparability to traditional methods, complicated & laborious setup & maintenance, expensive) have been carefully addressed, and improvements have been implemented. Recent research has proven that i.) highly dynamic and heterogenous processes (e.g., stem flow, groundwater recharge through preferential pathways, change of uptake depths in response to rainfall/drought, disentangling water use of different tree species in mixed forests) can be captured exceptionally well using in-situ isotope methods; ii.) water-vapor equilibration methods represent the isotope composition of mobile water better compared to destructive methods, and iii.) using continuous water isotope data reduces parameter uncertainties in SPAC modeling.In summary, we state that the benefits of using in-situ or semi in-situ techniques outweigh the disadvantages by far and strongly encourage the water stable isotope community to integrate them regularly into studies of dynamic soil-plant-atmosphere feedbacks.
Do the statistical properties of aftershocks change in fluid-induced settings?
Authors: Khajehdehi Omid , Davidsen Joern
Published: February 2023

Fluid-induced earthquakes are an adverse effect of industrial operations like hydraulic fracturing (e.g., 4.7 Mw in Alberta, Canada), and enhanced geothermal systems (e.g., 5.5 Mw in Pohang, South Korea). Identifying all underlying physical processes contributing to fluid-induced seismicity presents an open challenge. Recent work reports signatures of event-event triggering or aftershocks --- common for tectonic settings --- within the context of fluid-induced seismicity. In particular, the statistical properties including the productivity relation and the Omori-Utsu relation appear to hold for fluid-induced seismicity as well. Here, we investigate the underlying potential cause of these field observations from a modelling perspective. By extending a novel conceptual model by integrating (non-)linear viscoelastic effects with a combination of fluid diffusion and invasion percolation associated with a point source, we are able to capture the essential characteristics of crustal rheology and stress interactions in a porous medium. We show that this gives rise to realistic aftershock behaviour with statistical properties indistinguishable from the case of seismicity resulting from tectonic loading. This is even true if the loading due to fluid injections occurs at time scales much faster than the tectonic loading. In our model framework, such tectonic loading can be mimicked by a spatially uniform drive replacing the point source of the fluid injection and its propagation to initiate slips and earthquakes. This indicates that the emergence of the Omori-Utsu relation is independent of how the system is loaded or driven and it is indeed only controlled by the viscoelasticity of the medium. Similarly, the scaling exponent of the productivity relation --- which quantifies how the number of aftershocks increases with the magnitude of the main shock --- is independent of how the system is driven. At the same time, the spatial footprint of fluid-induced events and its dependence on the permeability field are primarily unaltered by the presence of aftershocks. Finally, within our model framework, we systematically investigate the impact of varying fluid injection rates during the viscoelastic stress redistribution on the detection of aftershocks and event-event triggering sequences. When the injection rate is sufficiently high, the aftershock detection and recovery of the Omori-Utsu and productivity relations is only feasible when the internal stress redistribution is directly accessible. 