Long-term soil moisture datasets at high spatial resolution are important in agricultural, hydrological, and climatic applications. The soil moisture estimates can be achieved using satellite remote sensing observations. However, the satellite soil moisture data are typically available at coarse spatial resolutions (~ several tens of km), therefore require further downscaling. Different satellite soil moisture products have to be conjointly employed in developing a consistent time-series of high resolution soil moisture, while the discrepancies amongst different satellite retrievals need to be resolved. This study aims to downscale three different satellite soil moisture products, the Soil Moisture and Ocean Salinity (SMOS, 25 km), the Soil Moisture Active Passive (SMAP, 36 km) and the SMAP-Enhanced (9 km), and to conduct an inter-comparison of the downscaled results. The downscaling approach is developed based on the relationship between the diurnal temperature difference and the daily mean soil moisture content. The approach is applied to two sub-catchments (Krui and Merriwa River) of the Goulburn River catchment in the Upper Hunter region (NSW, Australia) to estimate soil moisture at 1 km resolution for 2015. The three coarse spatial resolution soil moisture products and their downscaled results will be validated with the in-situ observations obtained from the Scaling and Assimilation of Soil Moisture and Streamflow (SASMAS) network. The spatial and temporal patterns of the downscaled results will also be analysed. This study will provide the necessary insights for data selection and bias corrections to maintain the consistency of a long-term high resolution soil moisture dataset. The results will assist in developing a time-series of high resolution soil moisture data over the south-eastern Australia.

Using the Global-scale Observations of the Limb and Disk (GOLD) and the Global Ultraviolet Imager (GUVI), we examine the impact of sudden stratospheric warmings (SSWs) on the changes of thermospheric composition during the 2018-2019 and 2020-2021 Arctic SSWs and the 2019 Antarctic SSW. Contributions of planetary waves, gravity waves, and migrating tides are assessed by performing numerical experiments with the NSF National Center for Atmospheric Research (NCAR) vertically extended version of the Whole Atmosphere Community Climate Model (WACCM-X). The wind evolution simulated in WACCM-X aligns well with the quasi-geostrophic wind derived from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) geopotential height measurements during Arctic and Antarctic SSWs. The variations in column integrated O and N2 density ratio (∑𝑂/N2) are generally similar among WACCM-X, GOLD, and GUVI observations. Following the onset of SSWs, ∑𝑂/N2 is reduced by ~10% over 50°S-50°N and enhanced by ~20% at higher latitudes. The ∑𝑂/N2 changes are associated with the reversals of the mean meridional circulation in the lower thermosphere, mainly driven by westward-travelling planetary waves. The results highlight that planetary wave activity during SSWs can significantly impact the mean state of the thermosphere.

This work presents 30-year observations of dust chemical composition by the IMPROVE network in the United States. Analysis of 1,253 large dust storms detected at the IMPROVE sites shows that dust PM2.5 (particles less than 2.5 micrometers in fresh dust plumes) crustal materials (64%), organic matter (13%), sulfate (7%), nitrate (2%), Cl, Br, and heavy metals. Dust composition stays relatively stable during near source transport. There are distinct spatial variations in dust composition, including high carbon and sulfate in Oklahoma, high Cl in Washington, and high fractions of heavy metals in Arizona. Compared to the Earth’s crust, dust PM2.5 contains less crustal elements but more OC, EC, sulfate, nitrate, and halogen elements due to influence by human activities and biogeochemical processes. This rich pool of dust composition data provides useful information to study the roles played by dust in the Earth system and its effects on human society.

Organic matter (OM) sulfurization can enhance the preservation and sequestration of carbon in anoxic sediments, and it has been observed in sinking marine particles from marine O2-deficient zones. The magnitude of this effect on carbon burial remains unclear, however, because the transformations that occur when sinking particles encounter sulfidic conditions remain undescribed. Here, we briefly expose sinking marine particles from the eastern tropical North Pacific O2-deficient zone to environmentally relevant sulfidic conditions (20C, 0.5 mM [poly]sulfide, two days) and then characterize the resulting solid-phase organic and inorganic products in detail. During these experiments, the abundance of organic sulfur in both hydrolyzable and hydrolysis-resistant solids roughly triples, indicating extensive OM sulfurization. Lipids also sulfurize on this timescale, albeit less extensively. In all three pools, OM sulfurization produces organic monosulfides, thiols, and disulfides. Hydrolyzable sulfurization products appear within ≤ 200-m regions of relatively homogenous composition that are suggestive of sulfurized extracellular polymeric substances (EPS). Concurrently, reactions with particulate iron oxyhydroxides generate low and fairly uniform concentrations of iron sulfide (FeS) within these same EPS-like materials. Iron oxyhydroxides were not fully consumed during the experiment, which demonstrates that organic materials can be competitive with reactive iron for sulfide. These experiments support the hypothesis that sinking, OM- and EPS-rich particles in a sulfidic water mass can sulfurize within days, potentially contributing to enhanced sedimentary carbon sequestration. Additionally, sulfur-isotope and chemical records of organic S and iron sulfides in sediments have the potential to incorporate signals from water column processes.

A document by Evi Wubben. Click on the document to view its contents.

The discipline of informatics, generically cast as the science and engineering of information system within a socio-technical framework, originating in the middle of last century has undergone generational adaptations as computer hardware, networks and software have evolved. Within the “eScience” era of the last two decades, discipline-specific fields of informatics have flourished, such as geoinformatics, mineral informatics and many more. In fact even in geosciences, there may be few fields of study that have not added an informatics sub-field. Over the same time, efforts at systematizing the common (or core, i.e. discipline neutral) aspects of informatics have been successful: use cases, human-centered design, iterative approaches, information models and more are some of the key elements. However new pressures are being placed on functional and non-functional requirements of information systems: with the now somewhat routine underlying data that are high dimensional, heterogeneous, sparse and with uncertain quality. However, demands have arisen from renewed attention to hub/ server/ cloud-based provision of the application of machine learning, neural networks and artificial intelligence in general. Those methods as implemented in software libraries producing results to be assessed and interpreted (often leading to decisions made) by “humans-in-the-loop”. Informatics, revisited is a possible answer. This presentation features some history of informatics, recent disruptions that need to be addressed, and offers ideas for new directions, with the goal of advancing geoscience in general.

A document by Christian Voigt. Click on the document to view its contents.

The Underwater Vision Profiler (UVP) provides abundant in situ data of the marine particle size distribution (PSD) on global scales and has been used for a diversity of applications, but the uncertainty associated with its measurements has not been quantified. Here we use a global compilation of UVP (version 5) observations of the PSD to assess the sampling uncertainty associated with the UVP’s sampling characteristics. We model UVP sampling uncertainty using Bayesian Poisson statistics and provide formulae for the uncertainty associated with a given sampling volume and observed particle count. We also model PSD observations using a power law with an exponential cutoff to better match the low concentration associated with rare large particles as seen by the UVP. We use the two shape parameters from this statistical model to describe changes in the PSD shape across latitude band, season, and depth. The UVP sampling uncertainty propagates into an uncertainty for modeled carbon flux exceeding 50%. The statistical model is used to extend the size interval used in a PSD-derived carbon flux model, revealing a high sensitivity of the PSD-derived flux model to the inclusion of small particles (80-128 microns). We close with recommendations on how to revise the carbon flux model, and we provide avenues to address additional uncertainties associated with UVP-derived carbon flux calculations.

Earthquakes are commonly modeled as shear cracks, where the slip profile of an earthquake rupture is the spatial distribution of relative displacement between fault surfaces. It is an accumulated result of all the processes during the earthquake: nucleation, propagation, and arrest. Understanding the characteristics of a slip profile gives insight into the associated stress changes, which is generally immeasurable on natural faults, and is useful for understanding the underlying friction law. Most models focus on simplicity for application purposes. For instance, the elastic crack model (Bilby & Eshelby, 1968) established that a perfect crack with uniform shear stress drop leads to an elliptical slip profile; Cowie and Scholz (1992) proposed a crack model with constant-stress cohesive zones at the crack tips, which results in “bell-shaped” slip profiles. However, the elliptical model results in unphysical stress singularities at crack tips, and the plateau in stress drop distribution near crack tips in the “bell-shaped” model is infeasible for friction dominated ruptures because it is commonly believed that slip is always accompanied by shear stress drop, e.g. slip-weakening friction law (Andrews, 1976). ­ We present results from recent large-scale laboratory experiments where all the rupture processes are contained in a 3-meter long saw-cut granite fault (Ke et al., 2018) and slip local fault slip and shear stress changes are measured at 16 locations along the fault. Guided by the laboratory experiments, we derived an analytical model to faithfully represent measured slip profiles δ(x), and shear stress changes Δτ(x), resulting from laboratory earthquakes. Field measurements of slip profiles revealed that slip profiles are commonly tapering roughly linearly toward the tips. The proposed model includes this feature, and thus fits slip profiles measured from natural earthquakes on isolated faults better than other idealized analytical models. For more complex natural earthquakes, our model can be used as a basis function. Our results suggest that inelastic earthquake processes can be solely originated from friction, and the shape of an earthquake rupture is likely between the elliptical and bell-shaped idealized models.

The response of critically stressed dormant faults to fluid perturbation, by oil and gas production, has been a major public concern because of its link to induced seismicity. In this paper, we study the hydrogeological factors that affect a nearby fault response, during and after hydraulic fracturing (HF) operations, evaluated by the change in Coulomb Failure Stress (CFS) through coupling solid deformation and fluid flow. We take the Duvernay formation in Alberta, Canada as a base study case for our analysis. Our results show that the injection rate and the fault’s distance to HF operations play an important role in increasing the CFS and hence the probability of fault reactivation. When the fault is far from the operations, its damage zones allow lateral diffusion and prevent pore pressure build up in its upper part, which stabilizes it. The lower part, however, will be under a lower normal stress and its failure may be triggered by an increase in shear stress. This is not the case for close faults where the damage zones act as conduits for pressure diffusion and the possible triggering failure mechanism will be the increase in pore pressure. Moreover, we show that the width of the HF zone does not affect the activation mechanisms or the stability of the fault unless it is hydraulically connected to its damage zone. Therefore, serious attention should be given to the fault position, its architecture, and the volume of fluid injected to help reduce the potential for induced seismicity from HF.

Hydrogen cyanide (HCN) is a widely available molecule in planetary and interplanetary environments. It has been observed that the polymerization of HCN can lead to the formation of nucleobases and proteins (Matthews & Minard 2006). Thus, HCN and its reactivity are considered to be very important for prebiotic chemistry. Our evaluation covers several molecules and oligomers, most of which have been discussed in the literature (Ruiz-Bermejo et al., 2021), and ranks them based on thermodynamic preference. In our study, we compute the relative energies of a series of HCN-derived materials relative to HCN in liquid water. We perform an automated search with semi-empirical methods to extract the lowest energy conformers for each compound. Our work relies on density functional theory (DFT) calculations with thermal corrections coupled to an implicit solvation model to better emulate the polymerization environments. These methodologies allow us to discuss the impact of our results at relevant environments such as that of Saturn’s Moon Titan or the early Earth conditions. The most stable HCN-derived material in our set is the nucleobase adenine, computed to lie ~26 kcal mol-1 below HCN in a water solution. Our enumeration of thermodynamically plausible reaction products and the reaction routes for the abiotic formation of organic macromolecules starting from simple units of HCN offers extensive insights into the chemical and the physical limitations of suspected key prebiotic processes (Sandström & Rahm 2021). 1. C. N. Matthews, R. D. Minard, Faraday Discuss. 2006, 133, 393. 2. M. Ruiz-Bermejo, J. L. de la Fuente, C. Pérez-Fernández, E. Mateo-Martí, Processes 2021, 9, 597. 3. H. Sandström, M. Rahm, ACS Earth Space Chem. 2021, 5, 2152–2159.

This work introduces the results of an intensive 15-day surface observation campaign of methane (CH4) and adapts a new analytical method to compute and attribute CH4 emissions. The selected area has a high atmospheric concentration of CH4 (campaign-wide minimum/mean/standard deviation/max observations: 2.0, 2.9, 1.3, and 16 ppm) due to a rapid increase in the mining, production, and use of coal over the past decade. Observations made in concentric circles at 1km, 3km, and 5km around a high production high gas coal mine were used with the mass conserving model free emissions estimation approach adapted to CH4, yielding emissions of 0.73, 0.28, and 0.15 ppm/min respectively. Attribution used a 2-box mass conserving model to identify the known mine’s emissions from 0.042-5.3 ppm/min, and a previously unidentified mine’s emission from 0.22-7.9 ppm/min. These results demonstrate the importance of quantifying the spatial distribution of methane in terms of control of regional-scale CH4 emissions.

Recent developments in satellite processing tools allow noncost, fast and automatic processing of a large amount of information from Earth observation, enhancing the capability of detecting coastal changes from space at different temporal scales. However, these automatic procedures are usually based on processors calibrated with information from a limited set of beaches, and the application of these tools to areas with different conditions may lead to significant errors in coastal change assessment. In this work, we evaluate the capability to monitor changes in coastal morphology at various temporal and spatial scales using 1D (coastlines) and 3D (bathymetry) satellite-derived data obtained from site-specific processing methods. Local characteristics were included in several phases of the development of the satellite products used here: i) VHR images from each pilot site were used in the coregistration process to guarantee high geolocation accuracy in images from different missions, ii) different spectral indices were tested at each pilot site to guarantee reliable detection of the coastline at all sites and iii) measured topobathymetry data were used to obtain datum-based satellite shorelines and bathymetry. The accuracy and skill of those satellite products were assessed at several pilot sites in Spain. The results indicated high horizontal accuracy, with errors on the order of half of the pixel size. Time-series analysis using satellite-derived shorelines showed that coastal change processes can be detected at several temporal and spatial scales, such as short-term erosion and accretion events on a small beach, seasonal beach rotation, and long-term trends at local and regional scales. However, the results from satellite-derived bathymetry indicated that the quantitative assessment of the coastal morphology with 3D products is still limited. Some in situ measurements are necessary to obtain satellite data that represent site-specific conditions. However, the quantity of required data measured in situ is significantly lower than the quantity required by traditional monitoring methods.

We present the first investigation of subsidence due to sediment compaction and consolidation in two laboratory-scale river delta experiments. Spatial and temporal trends in subsidence rates in the experimental setting may elucidate behavior which cannot be directly observed at sufficiently long timescales, except for in reduced scale models such as the ones studied. We compare subsidence between a control experiment using steady boundary conditions, and an otherwise identical experiment which has been treated with a proxy for highly compressible marsh deposits. Both experiments have non-negligible compactional subsidence rates across the delta-top, comparable in magnitude to our boundary condition relative sea level rise of 250 μm/h. Subsidence in the control experiment (on average 54 μm/h) is concentrated in the lowest elevation (<10mm above sea level) areas near the coast and is likely due to creep induced by a rising water table near the shoreface. The treatment experiment exhibits larger (on average 126 μm/h) and more spatially variable subsidence rates controlled mostly by compaction of recent marsh deposits within one channel depth (_10 mm) of the sediment surface. These rates compare favorably with _eld and modeling based subsidence measurements both in relative magnitude and location. We find that subsidence “hot spots” may be relatively ephemeral on longer timescales, but average subsidence across the entire delta can be variable even at our shortest measurement window. This suggests that subsidence rates in a given decade or century may exceed thresholds for marsh platform drowning, even if the long term trend does not.

Using the method of process-oriented hydrodynamic modelling, this work investigates the dispersal of particles in stratified fluids on continental margins. The focus is placed on steady-state density distributions that are governed by an advective-diffusive balance. In this case, particles can still be advected across isopycnal surfaces, given that turbulent fluctuations do generally not offset the advective displacement of a particle. The validity of this fundamental principle is demonstrated here with the diapycnal upslope sediment transport in a bottom Ekman layer that forms under a stratified geostrophic slope current. Similarly, this study demonstrates that interaction between slope currents with a submarine channel can facilitate a continuous diapycnal upslope flux of particles, confined to the lowermost 10-20 m of the water column. Velocity anomalies that facilitate this upslope sediment flux are the signature of standing topographic Rossby waves, that can only develop for slope currents that are left-bounded (right-bounded) by shallower water in the northern (southern) hemisphere. Findings of sensitivity studies confirm the existence of up-channel flows for a wide range of parameter values. Under the assumption that particles remain suspended in the water column, the inclusion of gravitational settling significantly increases the up-channel sediment flux. Sediment settling operates to trap particles close to the seafloor within the core of bottom-intensified up-channel flow. The author postulates that this mechanism plays an important role in biogeochemical cycles at continental margins.

Ganymede is the only Solar System moon known to generate a permanent magnetic field. Jovian plasma motions around Ganymede create an upstream magnetopause, where energy flows are thought to be driven by magnetic reconnection. Simulations indicate Ganymedean reconnection events may be transient, but the nature of magnetopause reconnection at Ganymede remains poorly understood, requiring an assessment of reconnection onset theory. We present an analytical model of steady-state conditions at Ganymede’s magnetopause, from which the first Ganymedean reconnection onset assessment is conducted. We find that reconnection may occur wherever Ganymede’s closed magnetic field encounters Jupiter’s ambient magnetic field, regardless of variations in magnetopause conditions. Unrestricted reconnection onset highlights possibilities for multiple X-lines or widespread transient reconnection at Ganymede. The reconnection rate is controlled by the ambient Jovian field orientation and hence driven by Jupiter’s rotation. Future progress on this topic is highly relevant for the JUpiter ICy moon Explorer (JUICE) mission.

We use densely spaced campaign GPS observations and laboratory friction experiments on fault rocks from one of the world’s most rapidly slipping low-angle normal faults, the Mai’iu fault in Papua New Guinea, to investigate the nature of interseismic deformation on active low-angle normal faults. GPS velocities reveal 8.3±1.2 mm/yr of horizontal extension across the Mai’iu fault, and are fit well by dislocation models with shallow fault locking (above 2 km depth), or by deeper locking (from ~5-16 km depth) together with shallower creep. Laboratory friction experiments show that gouges from the shallowest portion of the fault zone are predominantly weak and velocity-strengthening, while fault rocks deformed at greater depths are stronger and velocity-weakening. Evaluating the geodetic and friction results together with geophysical and microstructural evidence for mixed-mode seismic and aseismic slip at depth, we find that the Mai’iu fault is most likely strongly locked at depths of ~5-16 km and creeping updip and downdip of this region. Our results suggest that the Mai’iu fault and other active low-angle normal faults can slip in large (M > 7) earthquakes despite near-surface interseismic creep on frictionally stable clay-rich gouges.

Libraries are local community centers and hubs for learning, with increasing numbers of public libraries responding to the need to increase science literacy and support 21st century skills by adding STEM programs and resources for patrons of all ages. The Institute for Global Environmental Strategies (IGES), through the NASA Earth Science Education Collaborative (NESEC) cooperative agreement, is working with several libraries to pilot and implement collaborative models for engaging their local communities in STEM and citizen science. During spring and summer 2019, eight public library systems across the United States piloted activities and programs related to NASA’s GLOBE Observer citizen science app, which enables citizen scientists to contribute observations that complement NASA Earth observations. These include activities related to citizen scientist observations of Clouds (photographing clouds and recording sky observations), Mosquito Habitat Mapper (identifying water sources that are potential mosquito habitat and the presence of mosquito larvae; sampling and counting larvae; and using a clip on magnifier to identify the type of mosquito), and Land Cover (photographing the landscape and classifying land cover). Examples include the Pioneer Library System in Oklahoma, Southwest Oklahoma City Public Library, that is implementing GO Oklahoma! a citizen science campaign to collect GLOBE Observer Mosquito Habitat Mapper observations to support research by partner scientists at University of Oklahoma-Norman and Southern Nazarene University. The Los Angeles Public Library System has been field testing GLOBE Observer activities as part of its Neighborhood Science Program and will be incorporating these resources into circulating kits the library is developing for citizen scientists related to GLOBE Clouds and Mosquito Habitat Mapper that they will be piloting with Los Angelenos during fall 2019. Insights from the library pilot testing and programs include promising practices, requested resources, programming ideas and approaches, and particularly approaches to leveraging NASA subject matter experts and networks, to support local library programming.