Modelling physical processes such as flow and transport within a fracture network can be challenging, both conceptually and numerically. A typical approach is to upscale the properties of the network onto a regular grid of elements, which is then used to simulate the required physical processes. However, this method can be inaccurate if not carefully applied. For example, when most of the flow passes through a few choke points in the network, upscaling may introduce extra connectivity that is not present in the original network. The ConnectFlow software package has an alternative method for representing fracture networks, whereby the fractures are explicitly modelled as a network of intersecting two dimensional planes. The algorithms within ConnectFlow are very efficient, allowing millions of separate fractures to be simulated, each discretised using hundreds of finite elements. Here we present recent updates to this functionality: 1) to allow the advection-diffusion equation to be solved for multiple solute species (which is fully coupled to the pressure solution via the buoyancy term in Darcy’s equation); 2) to model the diffusion of solutes into the pore space of the surrounding rock (i.e. matrix diffusion); and 3) to carry out chemical reactions between solutes and minerals (which coat the fractures and/or the rock pores) using an interface to the IPhreeqc library. The ConnectFlow algorithms have also been parallelised to improve the tractability of this new functionality. This implementation represents a significant step forward in capability that allows groundwater flow, transport and hydrogeochemical reactions to be properly represented in the context of structurally constrained fractured bedrock. This has a wide range of potential applications, particularly for future safety assessments of nuclear waste facilities. Example calculations are presented for the Onkalo disposal facility in Olkiluoto, Finland, and the proposed Swedish repository for long-lived waste, SFL.

Strain weakening during plastic deformation can be achieved via strain energy reduction due to intragranular boundary development and grain boundary formation. To examine intragranular boundary formation at high temperatures (Th≈0.9), we analysed electron backscatter diffraction (EBSD) data of coarse-grained ice deformed at -30°C. Misorientation and weighted Burgers vector (WBV) statistics were calculated along planar intragranular boundaries. Neighbour-pair and random-pair misorientation distributions intersect at misorientation angles of 10–30°, indicating an upper limit to the misorientation threshold angle at which neighbouring grains begin to interact, e.g., rotate relative to each other. Misorientation angles change markedly along each analysed intragranular boundary, linking low- (<10°) and high-angle (10–38°) segments, with each segment exhibiting distinct misorientation axes and WBV directions. We suggest that these boundaries might be produced by the growth and intersection of individual boundary segments comprised of dislocations with distinct slip systems. This new kinematic model does not require a change in the boundary geometry after its formation, as required by the other models, to modify the crystallographic geometry of a planar boundary. Misorientation axis distributions are fundamentally different between intragranular boundaries (mostly confined to the ice basal plane) and grain boundaries (largely dispersed). This observation suggests a strong crystallographic control of intragranular boundary development via subgrain rotation. The apparent lack of crystallographic control for grain boundaries, on the other hand, suggests that misorientation axes become randomized upon grain boundary formation, likely due to the operation of other mechanisms/processes that can modify misorientation axes.

Despite much field and laboratory research, the origin of calcification in coccolithophores remains indeterminate. While most experiments on living species are not applicable to extinct taxa, long-term morphologic changes in lineages under well constrained oceanographic conditions may help elucidate the primary forcing on coccolithophore evolution if examined in the context of fundamental requirements (e.g., nutrient availability) of the living cell. The Order Discoasterales (66–1.92 Ma) was among the most prolific (>600 species, 16 genera) with greatest abundance and diversity in warm oligotrophic waters. Their coccoliths tell a story of morphologic changes that affected also their constituent elements resulting in lightweight constructions that became increasingly cavernous as oligotrophy increased in the Paleocene ocean, leading to increase in surface/volume ratio in keeping with increase in cell size. This likely constitutes direct evidence that coccoliths were involved in regulating cell physiology, both by maintaining a sufficient surface for nutrient absorption when cell volume increases or when nutrient content in seawater decreases, and by determining sinking rates. The cavernous nature of coccoliths further suggest mixotrophic physiology. Calcification may thus have been the innovation permitting the migration of the ancestral coccolithophore from nutrient-rich coastal waters to the blue ocean.

Undergraduate research internship programs are generally expected to teach interns about research ethics and research misconduct, often using case studies on plagiarism, data falsification/fabrication, and issues around authorship and intellectual property. While these are vital topics to discuss, this approach ignores the fundamental way in which Western science developed in tandem with European imperialistic expansion, and the ethically questionable way in which science historically has been and is often still conducted. For example: 1) How was the ideal of “discovery” in pursuit of knowledge used to justify European imperial expansion, and how did that history shape the current culture of science? 2) When collecting data in the field, do researchers consistently seek permission from the indigenous/international communities that reside on the land? And 3) Do Western scientists tend to disregard Traditional Ecological Knowledge from different cultures as a result of this history? In our 2021 Geosciences REU Workshop Series, we developed an ‘Ethics in the Geosciences Workshop’ that covers the traditional ethics topics, but also shines a light on the dark history of colonialism and racism that underpin Western science. We discussed prominent historical figures such as John Wesley Powell and Captain James Cook. Both men are greatly celebrated in academic/scientific spheres as explorers, cartographers, and scientists . However, their historical contributions reveal blatant racism towards indigenous people, the dismissal of indigenous knowledge and culture as being primitive and delusional, and for Cook, involved brutal slaughters around the world. Their values were aligned with Western imperialism, military expansion, and racism. The workshop included a discussion of examples of ‘parachute’ or ‘helicopter’ science, and the colonial undertones of modern day research in the Geosciences. Examples of racism, sexism, and safety in the field were examined through both a lecture and open-dialogue on a virtual platform. We acknowledged the many identities that we bring to science (race, gender, sexual identity, ability, nationality & citizenship, etc.), the relative privilege and power that these different identities may hold, and discussed addressing slurs and slights by using bystander strategies, as well as finding support in affinity groups. In tandem with this approach of broadening the scope of ethics discussions, it is hoped that intentionally creating safe, inclusive spaces in science for people of various and intersecting identities has the potential to change the ethical framework and social atmosphere in which we do science.

Composition, chemical disorder, and magnetism significantly affect the volume and bulk modulus of iron–silicon (Fe–Si) alloys at ambient pressure. Here, we computed the equations of state for bcc-like (ordered B2 and disordered bcc) Fe–Si alloys available up to the inner-core pressure using the first-principles Korringa–Kohn–Rostoker method. Ferromagnetic (FM) and nonmagnetic (NM) states over a wide composition range, from Fe to FeSi, were investigated. The results revealed that magnetism and chemical disorder increased the volume and decreased the bulk modulus even at high pressures. Comparing the results with the preliminary reference Earth model, we found that an unrealistically large temperature gradient is required if the inner core is composed of a bcc-like Fe–Si alloy.

Water table depth (WTD) is the predominant biophysical control over the occurrence of peat and forest fires in tropical peatlands. In Indonesia, prolonged droughts caused by El-Niño and/or positive Indian Ocean Dipole (IOD), exacerbated by extensive peat drainage for agriculture and plantation establishment, can promote severe peatland fires by lowering WTD and hence desiccating surface and sub-surface peats. The severe drought episode of late 2015 across Indonesia, caused by a strong El Nino and a positive IOD, led to a major and damaging increase in peatland fires, highlighting an urgent need to develop operational systems to forecast potentially severe fire events to mitigate the impacts of fire and haze. The 2002 ASEAN Agreement on Transboundary Haze Pollution, signed and ratified by a total of 10 ASEAN states, including Indonesia, identifies a critical need for such systems based on near-time climate projections. However, such systems have not yet been developed. While an operational early warning system for forecasting dangerous burning conditions in Indonesia is currently within reach using state-of-the-art modelling tools, such as the ECMWF’s System 5 seasonal forecast model (SEAS5), development is still hampered by insufficient knowledge about the influence of fluctuations in peat moisture on fire, particularly during periods of extreme drought. The main objectives of this study were: i) to deploy a process-based ecosystem model “ecosys” to study how WTD and peat moisture profiles change in tropical peatlands across Riau province, Sumatra, in response to drought and land cover change, focusing on the 2015 drought; and ii) to examine whether those changes could have been predicted using SEAS5. Model spin-up from 2008-2014 was driven by inputs from ECMWF’s climate reanalysis data (ERA5), followed by 3 parallel simulations for 2015, driven by ERA5, ERA5 climatology, and SEAS5 hindcasts. Model outputs of peat moisture profiles and WTD showed how peat moisture and WTD were significantly affected by weather and land uses during the dry season of 2015 which were corroborated well against data from Soil Moisture Active Passive satellite and site-level monitoring networks. Our work is a pioneering attempt to perform large-scale process-based modelling to predict seasonal variations in tropical peatland WTD.

To characterize how moderately large impactors might alter the differentiation and internal structure of Mars, we examine the fractional crystallization of intermediate depth magma oceans, and document that residual liquids ultimately become denser than normal Martian mantle, establishing unstable density gradients and inducing extensive magma descent within an evolving Mars. Fractional crystallization of intermediate depth magma oceans on Mars is likely to produce liquids that are dense enough to descend to the core-mantle boundary (CMB) and thus form a stably stratified thermochemical boundary layer at the Martian CMB. If this layer cooled sufficiently to crystallize, its mineralogy would be dominated by garnet and ferropericlase, or stishovite and ringwoodite, with changes in the descending liquid’s bulk composition having relatively minor effects on the resulting phase assemblage. While the size of Mars’ core remains uncertain, the addition of such a thermal boundary layer would impede the stabilization of (Mg, Fe)SiO3-perovskite at depth in Mars, although it would contain modest amounts of CaSiO3-perovskite. Such a compositionally distinct thermal boundary layer at the base of the Martian mantle would substantially elevate the inferred temperature of the Martian core, and also produce markedly lowered heat flow at the top of its core, with a potentially causal relation with the current lack of an internally generated Martian magnetic field. We calculate the seismic velocity anomalies that would be expected to be associated with such a layer, and find that the shift in mineralogy at depth should produce a seismic discontinuity that could prospectively be detectable by Martian seismic deployments.

Various recent studies have shown that basalt formations have the capacity for long-term secure CO2 storage through carbon mineralization. Many of these studies have demonstrated extremely rapid rates of mineralization, but the underlying mechanism enabling these elevated reaction rates, and their relation to the processes occurring in proposed basaltic reservoirs, remain poorly constrained. In this work, a 3D micro-continuum reactive transport model was designed to investigate the impact of alkalinity on basalt interactions with CO2-rich fluids. Reactive transport models were developed in PFLOTRAN based on 3D imaging data from high-temperature, high-pressure flow-through experiments (Luhmann et al. (2017) Chemical Geology, Water Resources Research). Mineral reactive surface areas in the model were adjusted to produce agreement with chemistry of output fluids sampled during the experiments. The benchmarked model showed that no considerable carbonate was formed during interaction with the relatively low alkalinity, low pH solutions, regardless of the enrichment of basalt-derived Na+, Mg2+, and Fe2+ ions in the reactant fluid. Increasing the alkalinity of the injected fluids consistently yielded higher rates of carbon mineralization. Similarly, introducing a small initial volume fraction of carbonate minerals into the system contributed to increased carbon mineralization, because of the increased fluid alkalinity. These results thus reinforce a conceptual understanding of carbonate mineralization in basalt-hosted CO2 storage reservoirs that emphasizes the importance of aquifer fluid alkalinity, and caution against extrapolating results from elevated-alkalinity CO2 storage reservoirs and experiments to others where this is less likely to be representative.

Increasing awareness of the links between water-energy consumption has seen a strong focus on examining and identifying areas where reductions in greenhouse gas emissions can be achieved. We are becoming increasingly aware that a truly sustainable water and energy supply in any community must incorporate a systemic approach where community, governance, culture, economics and local environmental context are considered along with improved technological outcomes. This presentation is focussed on giving a snapshot of research projects that have been undertaken in Australia to understand the water-energy nexus through the use of digital technologies such as smart water and energy meters and big data analytics. Topics that will be highlighted will include: • the application of smart metering technology to improve our understanding of peak demand patterns and subsequent network optimization, (e.g. reduce energy demand for pumping), • assessing energy consumption of water heating systems with empirical information (e.g. measured water consumption patterns) • residential rain tank pump performance at an end use level • using smart meter enabled, water end-use data to identify the key indoor and outdoor end-uses that contribute to water-related energy demand; and • the water-energy nexus in remote and Indigenous communities – using water demand management to reduce high energy off-grid water supply costs Projects will cover urban, regional and remote communities and will. The presentation will conclude some provide insights on how using a combination of socio-technical approaches can reveal both barriers and opportunities to reducing water and water-related energy demand.

COSMOS soil moisture sensors provide meso-scale area-averaged soil moisture estimates, presenting a unique opportunity for validating remotely sensed soil moisture data from satellite sensing platforms such as SMAP. New, roving COSMOS sensors can provide greater spatial coverage than their stationary counterparts. However, COSMOS sensors require careful site-specific calibrations, which are not available for roving sensors. As such, it is critically important for researchers to monitor roving COSMOS collection campaigns in near-real-time. However, specialized user interfaces are needed for rapid analysis. Moreover, harmonizing remotely sensed data (such as Landsat, SSURGO, MODIS, SMAP, and SRTM) with a roving COSMOS sensor is non-trivial and requires great care that cannot be accomplished on-the-fly in the field. To address these problems, we are developing the open source SoilMAP (Soil Moisture Analysis and Processing) software, which is a specialized analysis application for COSMOS and SMAP soil moisture data. We are developing this application using PODPAC (https://podpac.org/), a cloud-ready open source Python library for large-scale analysis and on-demand processing of raw earth science data. Our soil moisture analysis application aims to provide (1) customizable, rapid, near-real-time visualization and analysis of COSMOS and SMAP data; (2) unified data access and automated data wrangling to harmonize roving COSMOS measurements and SMAP L3 data; and (3) a streamlined workflow for developing roving COSMOS sensor calibrations with uncertainty estimates. We will demonstrate on-demand processing of raw soil moisture data retrieved from COSMOS sensors and SMAP L3 data using our SoilMAP software framework. We will also show our user workflows specialized for (1) staging data from various remotely-sensed and in-situ sensors, (2) monitoring a COSMOS data collection campaign in near-real-time, and (3) analyzing the resultant data with comparison to SMAP soil moisture. We will outline the steps required to build and customize this application. SoilMAP greatly reduces the burden of analyzing, comparing, and validating soil moisture data using measurements from roving COSMOS sensors.

Improved air quality has been the silver lining of the pandemic since early 2020. The air quality in northern New Jersey was continuously measured during the COVID-19 pandemic and through the three stages of recovery, i.e. the Stay-at-home Stage, Reopening Stage 1 and Reopening Stage 2. A significant change in air quality was observed during the Stay-at-home Stage (March 16 to May 16, 2020) as most people stayed home and industrial activity decreased 60%. Compared to 2019, carbon dioxide (CO2) decreased 17%, carbon monoxide (CO) decreased 7%, and nitrogen oxides (NOx) decreased 51% during the Stay-at-home Stage in 2020. However, the ground-level ozone (O3) increased in 2020 because of the reduced NOx emission and the possibly increased levels of volatile organic compounds (VOCs) due to the warmer weather. With the step-by-step reopening process, the difference in local CO2 levels between 2019 and 2020 was reduced and the NOx concentration returned to its 2019 level. The CO2 concentrations were positively correlated with CO, and the NOx concentrations were negatively correlated with O3 in 2020. However, these correlations are different from those in 2019. The impact of COVID-19 was found to influence the concentration levels of CO2, CO, NOx, and O3 beyond the effects of meteorology parameters on air quality in metropolitan New Jersey. Moreover, our findings provide a reference of air pollution reduction through replacing fossil fuels with electric or renewable energy in the transportation system and industry.

One key question about Mars is whether life has been or still is present on or beneath its surface. For life to flourish, it requires a habitable environment with the appropriate physical and chemical regolith parameters. To better understand the parameters that constitute a habitable environment, leachates of three martian simulants (JSC Mars-1, MMS-1 fine, and MGS-1) were analyzed for their soluble ionic composition, pH, and conductivity in order to determine the presence of any beneficial or toxic elements and their effects on the two bacteria E. coli and Eucapsis. E.coli was cultured in minimal media where acetic acid was the only organic source, and tested its requirements for a carbon source (acetic acid), nitrogen source ((NH4)2SO4) as well as trace elements (Ca, Mn, Zn, Cu, Fe, Co, Mo). In minimal culture media with all nutrients available for healthy growth, E. coli showed substantial growth. In the case of a carbon-only source or nitrogen-only source in MMS-1 soil leachate, E. coli showed limited growth compared to that observed in the full minimal culture media. Assessing Eucapsis growth, among the three leachates tested MMS-1 displayed the best growth. Additionally, we observed that MMS-1+Allen’s minimal and full Allen’s medium groups displayed similar growth curves, indicating that MMS-1 can provide all the trace elements needed for Eucapsis growth. Among all the leachates, MMS-1 showed the most promising results. MMS-1 + Allen’s medium provided the highest Eucapsis growth. MGS-1 + Allen’s minimal media also showed significantly higher growth than MGS-1 alone. However, JSC and JSC + Allen’s minimal did not show any significant difference regarding Eucapsis growth. The results indicated that Eucapsis grew best in both MMS-1 F leachate only and MMS-1 F leachate with Allen’s minimal medium.

Arctic sea ice is a key component of the Arctic hydrologic cycle. This cycle is connected to land and ocean temperature variations and Arctic snow cover variations, spatially and temporally. Arctic temperature variations from historical observations shows an early 20th century increase (i.e. warming), followed by a period of Arctic temperature decrease (i.e. cooling) since the 1940s, which was followed by another period of Arctic temperature increase since the 1970s that continues into the two decades of the 21st century. Evidence has been accumulating that Arctic sea ice extent can experience multi-decadal to centennial time scale variations as it is a component of the Arctic Geohydrological System. We investigate the multi-satellite and sensor daily values of area extent of Arctic sea ice since SMMR on Nimbus 7 (1978) to AMSR2 on GCOM-W1 (2019). From the daily time series we use the first year-cycle as a wave-pattern to compare to all subsequent years-cycles, currently to 30 June 2019, and constitute a derivative time series. In this time series we find the emergence of a multi-decadal cycle, showing a relative minimum during the period of 2007 to 2014, and subsequently rising. This may be related to an 80-year cycle (hypothesis). The Earth’s weather system is principally driven the solar radiation and its variations. If the multi-decadal cycle in Arctic sea ice area extent that we interpret continues, it may be linked physically to the Wolf-Gleissberg cycle, a factor in the variations of terrestrial cosmogenic isotopes, ocean sediment layering and glacial varves, ENSO and Aurora. Our hypothesis and results give more evidence that the multi-decadal variation of Arctic sea ice area extent is controlled natural physical processes of the Sun-Earth system.

During the last century, descriptions of sediment transport on the surface of Earth have been mostly deterministic and strongly influenced by concepts from continuum mechanics. The assumption that particle motions on hillslopes and in rivers satisfy the continuum hypothesis has provided an important foundation for this topic. Recent studies, however, have recognized that bed load and hillslope sediment transport conditions often are rarefied and do not satisfy continuum assumptions, therein pointing to the need for new ways of describing particle motions and transport. The problem of rarefied sediment transport is probabilistic in nature, and emerging methods for describing particle motions hark back to the pioneering work of Einstein (1938), who conceptualized bed load transport as a probabilistic problem. Here we provide a data set of particle travel distances and supplemental high-speed videos of particle-surface collisions collected during laboratory experiments to assess a theoretical formulation of the probabilistic physics of rarefied particle motions and deposition on rough hillslope surfaces. The formulation is based on a description of the kinetic energy balance of a cohort of particles treated as a rarefied granular gas, and a description of particle deposition that depends on the energy state of the particles. Both laboratory and field-based measurements are consistent with a generalized Pareto distribution of travel distances and predicted variations in behavior associated with the balance between gravitational heating and frictional cooling by particle-surface collisions. These behaviors vary from a truncated distribution associated with rapid thermal collapse to an exponential distribution representing approximately isothermal conditions to a heavy-tailed distribution associated with net heating of particles. The transition to a heavy-tailed distribution likely involves an increasing conversion of translational to rotational kinetic energy leading to larger travel distances with decreasing effectiveness of collisional friction. The analysis points to the need for further clarity concerning how particle size and shape in concert with surface roughness influence the extraction of particle energy and the likelihood of deposition.

Carbon isotope (δ13C) records from marine sediments have been extensively used in Cenozoic chemostratigraphy. The early Paleogene interval in particular has received exceptional attention because negative carbon isotope excursions (CIEs) documented in the sedimentary record, e.g. at the Paleocene Eocene Thermal Maximum (PETM), ca ~56 Ma, are believed to reflect significant global carbon cycle perturbations during the warmest interval of the Cenozoic era. However, while bulk-carbonate δ13C values exhibit robust correlations across widely separated marine sedimentary sections, their absolute values and magnitude of CIEs vary spatially. Moreover, bulk-carbonates in open-marine environments are an ensemble of different components, each with a distinct isotopic composition. Consequently, a complete interpretation of the bulk δ13C record requires an understanding of co-evolution of these components. In this study, we dissect sediments, from early Paleogene interval, at ODP Site 1209, Shatsky Rise, Pacific Ocean to investigate how an evolving bulk-carbonate ensemble influences the overall carbon isotope record. A set of 45 samples were examined for δ13C and δ18O compositions, as bulk and individual size fractions. We find a significant increase in coarse-fraction abundance across PETM, driven by a changing community structure of calcifiers, modulating the size of CIE at Site 1209 and thus making it distinct from those recorded at other open-marine sites. These results highlight the importance of biogeography in marine stable-isotope record, especially when isotopic excursions are driven by climate- and/or carbon-cycle changes. In addition, community composition changes will alter the interpretation of weight percent coarse fraction as conventional proxy for carbonate dissolution.

A nearly pole-to-pole survey near 140°E longitude on Europa revealed many areas that exhibit past lateral surface motions, and these areas were examined to determine whether the motions can be described by systems of rigid plates moving across Europa’s surface. Three areas showing plate-like behavior were examined in detail to determine the sequence of events that deformed the surface. All three areas were reconstructed to reveal the original pre-plate motion surfaces by performing multi-stage rotations of plates in spherical coordinates. Several motions observed along single plate boundaries were also noted in previous works, but this work links together isolated observations of lateral offsets into integrated systems of moving plates. Not all of the surveyed surface could be described by systems of rigid plates. There is evidence that the plate motions did not all happen at the same time, and that they are not happening today. We conclude that plate tectonic-like behavior on Europa occurs episodically, in limited regions, with less than 100 km of lateral motion accommodated along any particular boundary before plate motions cease. Europa may represent a world perched on the theoretical boundary between stagnant and mobile lid convective behavior, or it may represent an additional example of the wide variations in possible planetary convective regimes. Differences in observed strike-slip sense and plate rotation directions between the northern and southern hemispheres indicate that tidal forces may influence plate motions.

We investigated the effects of the propagation path and site amplification of shallow tremors along the Nankai Trough. Using far-field S-wave propagation from intraslab earthquake data, the amplification factors at the DONET stations were 5–40 times against an inland outcrop rock site. Thick (~5 km) sedimentary layers with VS of 0.6–2 km/s beneath DONET stations have been confirmed by seismological studies. To investigate the effects of thick sedimentary layers, we synthesized seismograms of shallow tremors and intraslab earthquakes at seafloor stations. The ratios of the maximum amplitudes from the synthetic intraslab seismograms between models with and without thick sedimentary layers were 1–2. This means that the estimated large amplifications are primarily controlled by thin lower-velocity (< 0.6 km/s) sediments just below the stations. Conversely, at near-source (≤ 20 km) distances, 1-order amplifications of seismic energies for a shallow tremor source can occur due to thick sedimentary layers. Multiple S-wave reflections between the seafloor and plate interface are contaminated in tremor envelopes; consequently, seismic energy and duration are overestimated. If a shallow tremor occurs within underthrust sediments, the overestimation becomes stronger because of the invalid rigidity assumptions around the source region. After 1-order corrections of seismic energies of shallow tremors along the Nankai Trough, the scaled energies of seismic slow earthquakes were 10-10–10-9 irrespective of the region and source depth. Hence, the physical mechanisms governing seismic slow earthquakes can be the same, irrespective of the region and source depth.

A document by Xiang Yang. Click on the document to view its contents.