Long period magnetotelluric (MT) data is being collected as a component of the USArray covering the continent of North America at a quasi-regular grid. Data from 250 MT stations were acquired covering the north-western part of the United States of America (USA). Dimensionality analysis was applied using Swift skew, Bahr skew and ellipticity. Results show a 1-D/2-D character for the short periods (< 1 sec) for the shallower structures, while the longer periods (> 1 sec) shows a 3-D character for the deeper structures. Two dimensional Occam inversion was applied for a set of E-W trending profiles to map the regional electrical resistivity distribution to a depth up to crust/mantle transition zone. 2-D resistivity structures were obtained by inverting both the transverse electric (TM) and transverse magnetic (TM) modes. Results show a resistive upper crust with a decreasing resistivity for lower crust. To the west, the subudcting Gorda plate was mapped as a relatively higher resistivity body nearly equal to the Wyoming basin to the east. Thick resistive lithosphere was mapped under Wyoming to the east. The results of this research shows the distribution of the electrical resistivity with adequate details for the shallow depth, while 3D inversion is necessary for the larger depths.

Detailed pathway of wave energy exchange between the Pacific and Indian Oceans through the Indonesian archipelago and associated energy dissipation are investigated by using a reduced gravity model with realistic coastline. The wave energy flux analysis that can be applicable for all latitudes in a linear shallow water system is adopted. The energy fluxes diagnosed from the model outputs for the incoming Rossby waves from the Pacific clearly indicate two major energy pathways to the Indian Ocean; one turning southward in the Halmahera Sea and reaches the Indian Ocean via the Banda Sea and the Timor Passage, the other passing through the Makassar and Lombok Straits. The former route, however, is shifted to the western side of the island chain within the Banda Sea due to energy trapping around the island chain. It is also found that strong energy dissipation occurs along the northern coast of New Guinea when the period of the incoming Rossby wave is shorter than 1.5 year. In the case of the Kelvin waves from the Indian Ocean, it is found that the major energy pathway is through the Lombok and Makassar Straits to the Pacific Ocean. However, there appears another pathway along the eastern side of the Sulawesi Island in the Banda Sea to exit through the Molucca Sea only when the wave period is shorter than about one month. This secondary pathway makes it easier for the wave energy from the Indian Ocean to reach the western Pacific Ocean for the short period waves.

Relativistic electrons in the radiation belts can be transported as a result of wave-particle interactions (WPI) with ultra-low frequency (ULF) waves. Such WPI are often assumed to be diffusive, parametric models for the radial diffusion coefficient often being used to assess the rates of radial transport. However, these WPI transition from initially coherent interactions to the diffusive regime over a finite time, this time depending on the ULF wave power spectral density, and local resonance conditions. Further, in the real system on the timescales of a single storm, interactions with finite discrete modes may be more realistic. Here, we use a particle-tracing model to simulate the dynamics of outer radiation belt electrons in the presence of a finite number of discrete frequency modes. We characterize the point of the onset of diffusion as a transition from separate discrete interactions in terms of wave parameters by using the “two-thirds” overlap criterion (Lichtenberg & Lieberman, 1992), a comparison between the distance between, and the widths of, the electron’s primary resonant islands in phase space. Further, we find the particle decorrelation time in our model system with typical parameters to be on the timescale of hours, which only afterwards can the system be modeled by one-dimensional radial diffusion. Direct comparison of particle transport rates in our model with previous analytic diffusion coefficient formulations show good agreement at times beyond the decorrelation time. These results are critical for determining the time periods and conditions under which ULF wave radial diffusion theory can be applied.

A modified version of the commercially available RheOptiCAD® was developed to examine the conformational changes and break-up of flocs in clay suspensions in microscopic detail, under shearing action. In contrast to the RheOptiCAD®, our device aims to enable the structural observation of suspensions even when coagulation or settling of particles onto the bottom plate of the shear cell occurs. This challenge was met by using an upright modular microscope instead of an inverted one, equipped with a CMOS camera to record the structural evolution of samples as a function of shear. The verification of the design was done by analysing a model system of un-flocculated and flocculated kaolin suspensions. Additional experiments with natural clay (mud) suspensions were performed.

The Mesozoic Dipole Low (MDL) is a period, covering at least ~80 million years, of low dipole moment that ended at the start of the Cretaceous Normal Superchron. Recent studies of Devonian age Siberian localities identified similarly low field values a few tens of million years prior to the Permo-Carboniferous Reverse Superchron (PCRS). To constrain the length and timing of this potential new dipole low, this study presents new paleointensity estimates from Strathmore (~411-416 Ma) and Kinghorn (~332 Ma) lava flows, UK. Both localities have been studied for paleomagnetic poles (Q values of 6-7) and the sites were assessed for their suitability for paleointensity from paleodirections, rock magnetic analysis, and microscopy. Thermal- and microwave-IZZI protocol experiments were used to determine site mean paleointensity estimates of ~3-51 μT (6-98 ZAm²) and 4-11 μT (9-27 ZAm²) from the Strathmore and Kinghorn localities, respectively. These, and all of the sites from 200-500 Ma from the (updated) PINT15 database, were assessed using the Qualitative Paleointensity criteria (Qᴘɪ). The procurement of reliable (Qᴘɪ ≥5), weak paleointensity estimates from this and other studies indicates a period of low dipole moment (median field strength of 17 ZAm²) for ~80 Myrs, from 332-416 Ma. This “Mid-Paleozoic Dipole Low (MPDL)” bears a number of similarities to the MDL, including the substantial increase in field strength near the onset of the PCRS. The MPDL also adds support to inverse relationship between reversal frequency and field strength and a possible ~200 million-year cycle in paleomagnetic behavior relating to mantle convection.

Subsurface remediation of groundwater and soils contaminated by chlorinated ethenes is a challenge as many sites remain with contaminant concentrations above regulatory limits. One issue that prevents site restoration is back diffusion of contaminants from low permeable layers into transmissive layers, which sustains contaminant plumes. In our research, we develop a two-dimensional analytical model of an aquifer-aquitard system which employs temporally variable boundary conditions to investigate the sensitivity of mass discharge across a downgradient control plane (DGCP) to both the mass discharge behavior from dense nonaqueous phase liquid source zones (i.e., the source-strength function or SSF) and contaminant mass stored in the aquitard. Existing models usually assume constant concentration boundary conditions which are not always representative of actual field conditions, especially when those boundary conditions are meant to represent the SSF. Modeling results are used to explore aquitard source functions, defined as the relationship between mass discharge across the DGCP and mass stored in the upgradient aquitard. We also explore the benefits associated with partial removal of DNAPL mass from the source zone, as well as the impacts of when those efforts occur in the lifetime of the source zone by testing the sensitivity of mass stored in the aquitard and mass discharge across a DGCP to different remediation scenarios. In instances where complete remediation is impractical, it is important for remediation managers (and other stakeholders) to know the options and expected results for partial remediation in the short term. Moreover, results are used to assess the relative importance of addressing contaminant mass in the DNAPL source zone versus the aquitard as the contaminant site ages. Finally, we explore a methodology for estimating contaminant mass in the aquitard with time, as a function of the SSF and mass discharge across a DGCP. This methodology complements site characterization efforts, especially at complex sites where detailed sampling of low permeable layers is a challenge.

Soil moisture (SM) analyses and assessments hold significance for numerous applications in the fields of hydrometeorology and agriculture. Throughout history, flux tower sites have been a primary source of data for observationally-based SM examinations and evaluations of landatmosphere interaction. However, these monitoring stations are not evenly distributed worldwide. One of the ways in which the comprehensive understanding of how land and atmosphere interact can be improved is by incorporating remotely sensed SM observations. The Soil Moisture Active Passive (SMAP) satellite is one of the satellite resources which closely aligns with in-site observations. However, the remote sensing nature of SMAP data means that it is prone to unpredictable random distortions. Since variations in SM tend to follow a fundamental Markov process, they typically display a specific "red noise" pattern of variability. On the other hand, satellite data that incorporates random fluctuations exhibits a more uniform "white noise" pattern at higher frequencies, which contrasts with the anticipated red noise pattern. Furthermore, gaps in SMAP data are not randomly distributed; due to its orbital characteristics, the satellite experiences regular instances of missing data during its 8-day orbital cycle, differing depending on the orbital pass. This introduces additional anomalies in the power spectrum, performed through examining correlations in the time series data, leading to recurring spikes at intervals of 8, 4 (half of 8), 2 and 2/3 (one-third of 8), and 2 days (one-fourth of 8). These spectral spikes become broader due to small variations in the satellite's orbit. To make the satellite data most effective for assessing land-atmosphere interactions, which tend to rely on estimates of covariability of SM with other environmental variables, it is crucial to minimize the impact of random distortions and systematic missing data. A technique for adjusting the power spectrum, and thus the time series, of SM has been developed to minimize the influence of orbital harmonic spikes in the gridded Level 3 (L3) SMAP dataset. This is achieved by fitting a catenary function to the power spectrum between the harmonic spikes and then removing their influence. The adjusted spectrum is then aligned with soil moisture data from the surface layer, collected from sites within the AmeriFlux network (in-situ flux tower data). These sites demonstrate relatively minimal distortion and exhibit SM power spectra that closely resemble those generated by offline land surface models (LSMs), which are free of random noise by nature. Using validated spectral data from gridded LSM-based datasets, an improved global L3 SMAP dataset is being generated that accounts for noise and harmonic effects. This presentation will showcase the outcomes of this technique in enhancing SMAP data and its temporal correspondence with observational data.

Mesoscale ocean eddies dramatically impact oceanic material transport, momentum and energy budgets, and large-scale ocean circulation; therefore, reasonably diagnosing their effects is crucial for providing insights into eddy parameterization scheme development. In this work, a Reynolds and coarse-graining hybrid eddy transport diagnostic framework is proposed and applied in the Southern Ocean. Both the isotropic transport coefficient and anisotropic transport tensor are diagnosed and decomposed into contributions from transient and stationary eddies. The tensor can be split into its symmetric and antisymmetric parts, and the symmetric tensor is further diagonalized to analyze the eigenvalues and eigenvectors. We verify that the anisotropic assumption better fits the ocean mesoscale eddy transport process than the isotropic assumption, at least in the Southern Ocean. We place particular emphasis on the transport tensor’s stationary component affected by large-scale topographies, nonconservative processes, and large-scale flow structures and find that its influence is highly anisotropic horizontally and varies vertically. We probe all tensor-related elements that emerge in our hybrid framework, especially the eigenvalues and eigenvectors of the symmetric tensor. We reveal all three configurations of the major and minor eigenvalues that appear in the Southern Ocean, where the one representing vortex filamentation is the most common scenario. In addition, we discover a high randomness of the eigenvectors, which implies the possibility of a semideterministic and semistochastic anisotropic parameterization scheme.

The backflow plume from an electric thruster can lead to the accumulation of electrostatic charge on the spacecraft, leading to a negative charge. Interactions between the plume and solar wind can further influence the charge distribution, resulting in variations in spacecraft potential and interference with sensitive instruments. A 3D Particle-In-Cell (PIC) simulation tool within the Spacecraft Plasma Interaction Software (SPIS) is used to compute spacecraft charging effects from 0.067 to 1 Astronomical unit (AU). The study examines the dynamic behaviour of ambient electrons and ions, thruster electrons, and CEX-ions, as well as photoemission and secondary electrons, and solar photon flux impact on the spacecraft potential. The main finding is the demonstration that the high dominance of CEX-ions and thruster electrons helps to achieve a low and stable negative potential ranging from -2 to -6 V from 0.067 AU to 1 AU when the thruster is on, as opposed to the varying range of -5 to +9 V with the thruster off. Other findings are that the elimination of photoelectrons or secondary electrons has a comparatively greater impact on spacecraft potential when the thruster is off, as opposed to when the thruster is on. Both CEX-ions and thruster electrons significantly contribute to the mitigation and regulation of spacecraft potential towards a less negative potential in situations where photoemission or secondary electrons are absent or relatively unimportant.

A document by Ioannis Georgiou. Click on the document to view its contents.

To effectively reduce CO2 emissions, it’s vital to identify and quantify their sources. While the focus has been on CO2 from fossil fuel combustion, especially coal, the CO2 produced from coal’s other elements, such as sulfur, through chemical reaction, remains an ‘invisible’ carbon source. We analyzed the invisible carbon flux due to coal burning in the Xijiang River Basin, a highly industrialized region in China, using river sulfate fluxes. Dissolved sulfate concentration in the Xijiang River rose by over 300% from 1985 to 2011, largely due to coal combustion. In 2011, this resulted in 3.14 Mt of invisible carbon dioxide. We evaluated the impact of two flue gas desulfurization (FGD) methods on carbon emissions using a predictive model. By enhancing SO2 removal efficiency through these methods, China could cut invisible carbon emissions by 27.8 Mt CO2 annually, paving the way for a sustainable future.

Volcanic eruptions are usually not easily predictable and this poses a significant hazard not only for exposures to the local population but due to possible presence of tephra also for airline traffic. The significant investments of the last years in new monitoring techniques and networks have improved our capabilities to sense volcano health, but the path to automatically recognize signs of potentially hazardous unrest is still long. On the other hand, machine learning is currently living a period of tumultuous growth and it is possible to find its applications practically in all the contexts where there is an overflow of data to be interpreted. Our aim is to exploit the capability of some established algorithms in machine learning to test their reliability in early detecting anomalous signals from the monitoring network before eruption events on Mt. Etna (Italy). In particular, we evaluate the effectiveness of using random forest approaches to learn from the measured signals the complex dynamics of the Etnean volcanic environment without any a-priori information on the data relationships. Such models are then tested against real eruptive cases to assess their performance.

Aerosol type plays a critical role in the relationship between aerosol optical depth (AOD) and particulate matter (PM) mass concentration. Here, we present a mathematical formulation of how PM2.5 is related to AOD; when simplified to a linear equation, it reveals a functional dependence of the slope on aerosol type, hygroscopic growth, and boundary layer height, while the influence of the vertical aerosol profile is embedded in the intercept. We further employed a daily averaged AERONET measurement training dataset to develop a Normalized Gradient Aerosol Index (NGAI) for classifying sub-aerosol-types: mineral dust (MD), urban-industrial pollution (U/I) and biomass burning (BB). By distinguishing the aerosol subtypes beforehand, the derived AOD-PM2.5 linear regressions were significantly improved, demonstrating that NGAI can exploit the difference in aerosol hygroscopicity and improve the surface dry PM2.5 estimations. In addition, the hygroscopic growth factor, f(RH), can be estimated based on the slope (β1) of the AOD-PM2.5 expression.

Mount Early and Sheridan Bluff (87 degrees south) are the above-ice expression of Earth’s southernmost volcanic field and are isolated by more than 1000 km from any other exposed Cenozoic volcano in Antarctica. These monogenetic, Early Miocene volcanoes are constructed mostly of olivine-phyric basaltic pillow lavas and breccias (Mount Early) and pāhoehoe lavas (Sheridan Bluff) whose differentiation is controlled by the fractional crystallization of olivine with lesser quantities of clinopyroxene, plagioclase and magnetite. Fractional crystallization or contamination by crust cannot account for the coexistence of olivine tholeiite and alkaline compositions but their relationship can be explained by change from higher (5-6%) to lower (1.5-2%) degrees of mantle partial melting, respectively, of a source that is heterogeneous on a small-scale. Both alkaline and subalkaline magma types have geochemical and isotopic signatures that differentiate them from volcanism of the West Antarctic rift system. Data trends in Sr-Nd-Pb isotope space along with major and trace element characteristics indicate mixing of at least two-distinct mantle sources; 1) a relatively depleted component similar to sources for mid-ocean ridge basalt from the extinct Antarctic-Phoenix spreading center, and 2) an enriched component similar to sources for mafic magmas of the Jurassic Karoo‒Ferrar large igneous provinces. The availability of these two mantle source types was facilitated by the detachment, sinking and heating of metasomatized continental lithosphere (enriched source) that released volatiles into the surrounding asthenosphere (depleted source) to promote flux melting. Volcanism triggered by lithospheric detachment is therefore uniquely applied to Mount Early and Sheridan Bluff to explain their isolation and enigmatic tectonic setting but can also account for source heterogeneity and the ephemeral change in degree of mantle partial melting recorded in their mafic compositions.

Collisionless shocks in space plasma are regions of heating and acceleration of charged particles and dissipation of kinetic energy. These accelerated particles are the source of electromagnetic emissions from supernova remnants and other astrophysical structures. At high Mach numbers, shocks can be inherently nonstationary and exhibit modulated energy transfer and recurring plasma compression areas in the form of reformation. We use data from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft to study reformation of the Martian bow shock which has a relatively high curvature compared to that at Earth and the upstream solar wind is often mass loaded with a population of pickup ions. We show evidence of ion reflection effects in reformation of a supercritical quasi-perpendicular shock.

There is much discussion in the literature about the need to balance abilities to respond to short-term and long-term risks among water systems. Yet our understanding of what contributes to our ability to respond to acute as well as long-term change is challenged by insufficient empirical work on water systems to date. We begin to fill this gap through an examination of the capacities of community water systems to absorb short-term shocks as well as to learn from them and act to reduce future risks. We investigated these capacities and how they interact using interviews (n=24) and a survey (n=85) of Connecticut community water systems. We found most systems have increased their capacity to respond to short-term risks and most have some (but differing levels) of capacity for learning from those experiences. However, few are preparing adequately for future risks. We present opportunities for reducing this gap.

Ambient air pollution is an increasing threat to society, with rising numbers of adverse outcomes and exposure inequalities across the globe. Reducing uncertainty in health outcomes models and exposure disparity studies is therefore essential to develop policies effective in protecting the most affected places and populations. This study uses the concept of information entropy to study tradeoffs in mortality uncertainty reduction from increasing input data of air pollution versus health outcomes. We study a case scenario for short-term mortality from fine particulate matter (PM2.5) in North Carolina for 2001-2016, employing a case-crossover design with inputs from an individual-level mortality dataset and high-resolution gridded datasets of PM2.5 and weather covariates. We find a significant association between mortality and PM2.5, and the information tradeoffs indicate that in this case increasing information from mortality may reduce model uncertainty at a faster rate than increasing information from air pollution. We also find that Non-Hispanic Black (NHB) residents tend to live in relatively more polluted census tracts, and that the mean PM2.5 for NHB cases in the mortality model is significantly higher than that of Non-Hispanic White (NHW) cases. The distinct distribution of PM2.5 for NHB cases results in a relatively higher information value, and therefore faster uncertainty reduction, for new NHB cases introduced into the mortality model. This newfound influence of exposure disparities in the rate of uncertainty reduction highlights the importance of minority representation in environmental research as a quantitative advantage to produce more confident estimates of the true effects of environmental pollution.

Numerous studies have indicated that mesoscale eddies play an important role in diapycnal mixing and drive global water circulation. Although the relationships between eddy surface features and turbulent mixing have been discussed for individual cases of typical eddies, global studies cannot rely on ship-based microstructural measurements. Fine-scale methods have been developed, wherein either the vertical shear of velocity or density strain is used to estimate turbulent mixing. In this study, the turbulent dissipation rate was estimated using strain information from Argo floats trapped in eddies. Spatially averaged estimates revealed the global distribution patterns of the dissipation rates inside the eddies. In addition, the relationships between eddy features (polarity, radius, vertical extent, and aspect ratio) and turbulent dissipation rates were analyzed. Three main conclusions were made from this study. First, turbulent dissipation rates inside anticyclones were generally larger than those inside cyclones. Second, turbulent dissipation rates inside eddies are related to their vertical extent but not to their horizontal scale. For shallow eddies (with a vertical extent less than 250 m for cyclones and 300 m for anticyclones), the deeper the vertical extent, the larger the turbulent dissipation rate. Finally, the relationship between the eddy aspect ratio and turbulent dissipation rate was characterized by skewness. The average turbulent dissipation rate reached a maximum value when the cyclone aspect ratio was approximately 0.007; conversely, no maximum value was reached for anticyclones. This work establishes a correlation between eddy features and turbulent dissipation rates, which will help guide numerical simulations of mesoscale eddies.