Bed material abrasion is a major control on the partitioning of basin-scale sediment fluxes between coarse and fine material. While abrasion is traditionally treated as an exponential function of transport distance and a lithology-specific abrasion coefficient, experimental studies have demonstrated greater complexity in the abrasion process: the rate of abrasion varies with clast angularity, transport rate, and grain size. Yet, few studies have attempted to assess the importance of these complexities in a field setting. Here, we develop a new method for rapidly quantifying baseline abrasion rate in the field via Schmidt Hammer Rock Strength (SHRS). We use this method, along with measurements of gravel bar lithology, to quantify abrasion in the Suiattle River, a basin in the North Cascades of Washington State dominated by a single coarse sediment source: recurrent, debris flows from a tributary draining Glacier Peak stratovolcano. Rapid downstream strengthening of river bar sediment and a preferential loss of weak, low-density vesicular volcanic clasts relative to non-vesicular ones suggest that abrasion is extremely effective in this system. The standard exponential model for downstream abrasion fails to reproduce observed downstream patterns in lithology and clast strength in the Suiattle, despite accounting for the heterogeneity of source material strength and systematic underestimate of abrasion rates by tumbler experiments. Incorporating transport-dependent abrasion into our model largely resolves this failure. While a simplified approach to characterizing abrasion is tempting, our findings show that sediment heterogeneity and transport-dependent abrasion are important controls on the downstream fate of coarse sediment in fluvial systems.

Planar magma intrusions such as dykes and sills are major magma transport features and the main feeders of volcanic eruptions. Among planar intrusions, sheet intrusions are fracture-like continuous conduits, which are assumed to form by tensile opening and dominantly elastic deformation of the host. However, numerous planar intrusions are not continuous, and consist of aligned finger-shaped or more lobate conduits. Field observations show that the emplacement of these fingers is associated with inelastic, shear failure of the host rock, suggesting that the Mohr-Coulomb properties of crustal rocks play a significant role in the emplacement of fingers. In this study, we test the effects of the Mohr-Coulomb properties of crustal rocks on the emplacement of sheet-shaped and finger-shaped intrusions through quantitative 2-dimensional laboratory experiments. The model magma is viscous Golden Syrup, and the model rock is made of mixtures of dry granular materials of variable cohesion. A sideview camera allows monitoring the shape of the propagating intrusions and the associated deformation in the host, and a pressure sensor monitors the pressure of the syrup. Our experiments show that sheet intrusions form in high-cohesion hosts whereas finger-shaped intrusions form in low-cohesion hosts. Deformation analysis of the host and pressure data show that the sheets and fingers result from drastically distinct dynamics: sheets dominantly propagate as a fracture, whereas fingers are emplaced as viscous indenters. All in all, our experiments highlight that the cohesion of the Earth’s crust and the associated shear damage play a major role on planar intrusion emplacement.

We present a characterization of large amplitude, short-timescale geomagnetic disturbances that we refer to as transient induced current (TIC) events. TIC events are defined as one or more short-timescale (< 60 seconds) dB/dt signature with magnitude ≥ 6 nT/s. We identified 40 TIC events that occurred at six stations of the Magnetometer Array for Cusp and Cleft Studies throughout 2015 and we demonstrate the existence of large-amplitude dB/dt with timescale less than 10 seconds in nine of the events. The association of these events to sudden commencements is weaker than expected, rather the events are more likely to occur in relation to substorm onsets. However, 15% of TIC events show no direct association to geomagnetic storms, substorms or nighttime magnetic impulse events. Our findings suggest that the TICs have different properties than typical geomagnetically induced currents and may be hazardous to conductive components of the Internet of Things network.

Large-scale co-variations of freshwater fluxes and storages on land can critically regulate green (vegetation) and blue (hydrosphere) water balances, land-atmosphere interactions, and hydroclimatic hazards. Such essential co-variation patterns still remain largely unknown over large scales and in different climates around the world. To contribute to bridging this large-scale knowledge gap, we synthesize and decipher different data time series over the period 1980-2010 for 6405 hydrological catchments around the world. From observation-based data, we identify dominant large-scale co-variation patterns between main freshwater fluxes and soil moisture (SM) for different world parts and climates. These co-variation patterns are also compared with those obtained from reanalysis products and Earth System Models (ESMs). The observation-based datasets robustly show the strongest large-scale hydrological co-variation relationship to be that between SM and runoff (R), consistently across the study catchments and their different climate characteristics. The predominantly strongest large-scale SM-R co-variation relationship, however, is also the most misrepresented by ESMs and reanalysis products, followed by that between precipitation and R. Comparison between corresponding observation-based and ESM results also shows that an ESM may perform well for individual hydrological variables, but still fail in representing the patterns of large-scale co-variations between variables.

Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Electron-Proton Telescope (REPT) instruments on-board the Radiation Belt Storm Probes (RBSP) versus the measurements of the Extremely High Energy Electron Experiment (XEP) unit on-board Arase (ERG) mission is presented. The performed analysis demonstrates a remarkable agreement between the majority of MagEIS and XEP measurements and suggests the re-scaling of MagEIS HIGH unit and of REPT measurements for the treatment of flux spectra discontinuities. The proposed adjustments were validated successfully using measurements from ESA Environmental Monitoring Unit (EMU) on-board GSAT0207 and the Standard Radiation Monitor (SREM) on-board INTEGRAL. The derived results lead to the harmonization of science-class experiments on-board RBSP (2012-2019) and Arase (2017- ) and propose the use of the datasets as reference in a series of space weather and space radiation environment developments.

The total fish production in India is estimated to be 13.42 million metric tons (Mt) of which nearly 3.71 Mt are contributed by marine fisheries. The fisheries sector provides direct livelihood support to approximately 16 million people, of which marine fishers constitute a dominant subset and almost double the number along the value chain. In the past, the fisheries community in India had relied on traditional indicators of fish abundance such as the congregation of birds, colour of sea water, bubble breaking in the sea water and muddy/oily water on the sea surface in their traditionally known fishing grounds. The increased frequency of extreme weather events observed in recent times, have been related to major losses in marine ecosystem services. Further, the livelihoods of Small Scale Fisheries (SSF) communities are endangered not only by their limited understanding of the magnitude of the risks associated with natural hazards but also by the diminishing returns of relying on traditional knowledge for accurate prediction of the fishing stock at their usual locations. Therefore, the Government of India has launched several programs to use geospatial technologies for the benefit of marine pelagic fisheries in India for the sustainable development of the SSF communities. However, the lives of SSF communities are also challenged by complex, inter-linked socio-economic factors. In this paper, we focus on the maritime state of Odisha which is affected by several extreme weather events (cyclones) in the Bay of Bengal. We describe the socio-economic and technological factors which determine the degree of assimilation of the Potential Fishing Zone (PFZ) and Ocean State Forecast (OSF) advisories provided by the Indian National Centre for Ocean Information Services (INCOIS) with a focus on the threads linking natural and anthropocentric factors that produce significant changes in the Catch Per Unit Effort (CPUE) and net profit for pelagic fisheries of Odisha. More importantly, we identify the research and implementation gaps that must be addressed so that science, technology, and societal interactions can be used to enhance the sustainable development of the SSF communities. Keywords: Potential fishing zone, Catch per unit effort, Ocean state forecast, Geospatial technology.

We examine the historical and projected hydrography in the deep basin of the Arctic Ocean in 23 climate models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The comparison between historical simulations and observational climatology shows that the simulated Atlantic Water (AW) layer is too deep and too thick among the majority of the models and in the multi-model mean (MMM). Moreover, the halocline is too fresh in the MMM. These issues indicate that there is no visible improvement in the representation of Arctic hydrography in the CMIP6 compared to the CMIP5. The climate projections reveal that the sub-Arctic seas are outstanding warming hotspots, supplying a strong warming trend in the Arctic AW layer. The MMM temperature increase averaged in the upper 700 m till the end of the 21st century in the Arctic Ocean is about 40% and 60% higher than the global mean in the SSP245 and SSP585 scenarios, respectively. Comparing the AW temperature in the present day with its future change among the models shows that the temperature climate change signals are not sensitive to the model biases in the present-day simulations. The upper-ocean salinity is projected to become fresher in the Arctic deep basin in the MMM. However, the salinity spread is rather large and the tendency toward stronger upper ocean stratification in the MMM is not shared among all the models. The identified hydrography biases and spread call for a collective effort for systematic improvements of coupled model simulations.

Embayed beaches separated by irregular rocky headlands represent 50% of global shorelines. Quantification of inputs and outflows via headland bypassing is necessary for evaluating long-term coastal change. Bypassing rates are predictable for idealised headland morphologies; however, it remains to test the predictability for realistic morphologies, and to quantify the influence of variable morphology, sediment availability, tides and waves-tide interactions. Here we show that headland bypassing rates can be predicted for wave-dominated conditions, and depend upon headland cross-shore length normalised by surf zone width, headland toe depth and spatial sediment coverage. Numerically modelled bypassing rates are quantified for 29 headlands under variable wave, tide and sediment conditions along 75km of macrotidal, embayed coast. Bypassing is predominantly wave-driven and nearly ubiquitous under energetic waves. Tidal elevations modulate bypassing rates, with greatest impact at lower wave energies. Tidal currents mainly influence bypassing through wave-current interactions, which can dominate bypassing in median wave conditions. Limited sand availability off the headland apex can reduce bypassing by an order of magnitude. Bypassing rates are minimal when cross-shore length > 5 surf zone widths. Headland toe depth is an important secondary control, moderating wave impacts off the headland apex. Parameterisations were tested against modelled bypassing rates, and new terms are proposed to include headland toe depth and sand coverage. Wave-forced bypassing rates are predicted with mean absolute error of a factor 4.4. This work demonstrates wave-dominated headland bypassing is amenable to parameterisation and highlights the extent to which headland bypassing occurs with implications for embayed coasts worldwide.

This study explores a new concept of Martian differential absorption lidar operating at the 2-m CO2 absorption band for its atmospheric CO2 and pressure observations. For the considered system, closely-spaced two or more wavelengths are selected so that environmental impacts such as surface reflection, atmospheric scattering, and absorptions from other trace gases on the lidar return signals are very similar for all selected wavelengths, but the difference in CO2 absorption is substantial. Thus, Martian CO2 amount and air pressure could be retrieved from the measured CO2 differential absorption optical depth at the selected wavelengths. Simulations based on Mar’s environmental conditions and technically available lidar systems show that lidar returns from the surface with horizontally 5 km averaging could have sufficient signal strengths that allow air barometry and CO2 amount measurements with a noise induced random error (NIRE) smaller than 1% when the optical depth due to dust scattering, the dominant scatter in the Martian atmosphere, is 3 or less. In the presence of moderate dust aerosol loads and with the optimal selection of offline and online wavelengths, atmospheric CO2 and pressure profiles could also be retrieved from the surface up to ~10 km altitude with the NIRE smaller than 1% for a horizontal resolution of 100 km and a vertical resolution of 100 m during night or 400 m during day. When a second online wavelength is use, the lidar would provide invaluable measurements of Martian CO2 and pressure fields from surface up to about 13 km altitude.

Rakov and Uman pointed out (Lightning: Physics and Effects, 2003) that despite 5000 published reports of ball lightning (BL) and a scientific literature comparable in volume to the literature on conventional lightning, we still have no idea of what mechanisms create or power BL. Lightning characterization technology advances can and should be applied to BL studies. Keul and Diendorfer (2018) have correlated BL reports with European lightning-detection network data, but no such attempt has been made for US BL reports up to now. Using 31 BL reports from a now-defunct US website, we have attempted correlations with National Lightning Detection Network (NLDN) and radar data archived at the National Climactic Data Center. Of the 31 reports, 5 objects were indoors and 25 were reported to coincide with thunderstorms. Time information accurate to 30 minutes (1 sigma) and location information accurate within one to ten km was available from nine of the reports, and for these we obtained both NLDN and composite radar data covering the time frames indicated by the reports. For three of the nine reports, we found NLDN located strikes plausibly within the distance and time frames of the observer reports – thus qualifying as nearby (possibly causal) lightning. However, for the report for which the location of the ball was known within meters, the nearest lightning was 2.3 km away. 23 reports only associate BL with a storm within 25 km. Should it continue to hold in the face of more evidence, the relative lack of correlation of BL and nearby lightning suggests that the production of BL is associated more with static or changing electric fields in the vicinity of thunderstorms, than with the lightning plasma channel itself. While these results by themselves are limited, we are optimistic that one can learn more about the link between natural and ball lightning by fusing more precise eyewitness reports with lightning location and other archival meteorological data. To this end, we have launched a website to guide citizen scientists in future ball lightning reports. The site may be reached via https://tinyurl.com/BLReport.

The metastatistical extreme value approach proved promising in the frequency analysis of daily precipitation from ordinary events, outperforming traditional methods based on sampled extremes. However, sub-daily applications are currently restrained as it is not known if ordinary events can be consistently examined over durations, and it is not clear to what extent their entire distributions represent extremes. We propose here a unified definition of ordinary events across durations, and suggest the simplified metastatistical extreme value formulation for dealing with extremes emerging from the tail, rather than the entire distributions, of ordinary events. This unified framework provides robust estimates of extreme quantiles (≤10% error on the 100-year from a 26-year long record), and allows scaling representations in which ordinary and extreme events share the scaling exponent. Future applications could improve our knowledge of sub-daily extreme precipitation and help investigating the impact of local factors and climatic forcing on their frequency.

Prolonged volcanic activity can induce surface weathering and hydrothermal alteration that is a primary control on edifice instability, posing a complex hazard with its challenges to accurately forecast and mitigate. This study uses a frequently active composite volcano, Mt Ruapehu, New Zealand, to develop a conceptual model of surface weathering and hydrothermal alteration applicable to long-lived composite volcanoes. The rock samples were classified as non-altered, supergene argillic alteration, intermediate argillic alteration, and advanced argillic alteration. The first two classes have a paragenesis that is consistent with surficial infiltration and circulation of the low-temperature (40 degree C) neutral to mildly acidic fluids, inducing chemical weathering and formation of weathering rims on rock surfaces. The intermediate and advanced argillic alterations are formed from hotter (100 degree C) hydrothermal fluids with lower pH, interacting with the andesitic to dacitic host rocks. The distribution of weathering and hydrothermal alteration has been mapped with airborne hyperspectral imaging through image classification, while aeromagnetic data inversion was used to map alteration to several hundred meters depth. The joint use of hyperspectral imaging complements the geophysical methods since it can numerically identify hydrothermal alteration style. This study established a conceptual model of hydrothermal alteration history of Mt Ruapehu, exemplifying a long-lived and nested active and ancient hydrothermal system. This study highlights the need to combine mineralogical information, geophysical techniques and remote sensing to distinguish between current and ancient hydrothermal and supergene alteration systems, to indicate the most likely areas of future debris avalanche initiation.

Marine oxygen deficient zones (ODZs) are dynamic areas of microbial nitrogen cycling. Nitrification, the microbial oxidation of ammonia to nitrate, plays multiple roles in the biogeochemistry of these regions, including production of the greenhouse gas nitrous oxide (N2O). We present here the results of two oceanographic cruises investigating nitrification, nitrifying microorganisms, and N2O production and distribution from the offshore waters of the Eastern Tropical South Pacific (ETSP). On each cruise, high-resolution measurements of ammonium ([NH4+]), nitrite ([NO2-]), and N2O were combined with 15N tracer-based determination of ammonia oxidation, nitrite oxidation, nitrate reduction and N2O production rates. Depth-integrated inventories of NH4+ and NO2- were positively correlated with one another, and with depth-integrated primary production. Depth-integrated ammonia oxidation rates were correlated with sinking particulate organic nitrogen flux but not with primary production; ammonia oxidation rates were undetectable in trap-collected sinking particulate material. Nitrite oxidation rates exceeded ammonia oxidation rates at most mesopelagic depths. We found positive correlations between archaeal genes and ammonia oxidation rates and between -like 16S rRNA genes and nitrite oxidation rates. N2O concentrations in the upper oxycline reached values of greater than 140 nM, even at the western extent of the cruise track, supporting air-sea fluxes of up to 1.71 umol m-2 d-1. Our results suggest that a source of N2O other than ammonia oxidation may fuel high rates of nitrite oxidation in the offshore ETSP and that air-sea fluxes of N2O from this region may be higher than previously estimated.

Large scale flood risk analyses are fundamental to many applications requiring national or international overviews of flood risk. While large-scale climate patterns such as teleconnections and climate change become important at this scale, it remains a challenge to represent the local hydrological cycle over various watersheds in a manner that is physically consistent with climate. As a result, global models tend to suffer from a lack of available scenarios and flexibility that are key for planners, relief organizations, regulators, and the financial services industry to analyze the socioeconomic, demographic, and climatic factors affecting exposure. Here we introduce a data-driven, global, fast, flexible, and climate-consistent flood risk modeling framework for applications that do not necessarily require high-resolution flood mapping. We first use statistical and machine learning methods to examine the relationship between historical (from the Dartmouth Flood Observatory) flood occurrence and impact, and climatic, watershed, and socioeconomic factors at over 4700 watersheds globally. Using bias-corrected output from the NCAR CESM Large Ensemble from 1980 to 2020, and the fitted statistical relationships, we simulate one million years of events worldwide along with the population displaced. We discuss potential applications of the model and present global flood hazard and risk maps. The main value of this global flood model lies in its ability to quickly simulate realistic flood events at a resolution that is useful for large-scale socioeconomic and financial planning, yet we expect it to be useful to climate and natural hazard scientists who are interested in socioeconomic impacts of climate.

Scientific ocean drilling through the International Ocean Discovery Program (IODP) and its predecessors, has a far-reaching legacy. They have produced vast quantities of marine data, the results of which have revolutionized many geoscience subdisciplines. Meta-analytical studies from these efforts exist for micropaleontology, paleoclimate, and marine sedimentation, and several outstanding resources have curated and made available elements of offshore drilling data, but much of the data remain heterogeneous and dispersed. Each study, therefore, requires reassembling a synthesis of data from numerous sources; a slow, difficult process that limits reproducibility and slows the progress of hypothesis testing and generation. A computer programmatically-accessible repository of scientific ocean drilling data which spans the globe will allow for large-scale marine sedimentary geology and micropaleontologic studies and may help stimulate major advances in these fields. The eODP project, funded through the NSF’s EarthCube program, seeks to facilitate access to and visualization of these large microfossil and stratigraphic datasets. To achieve these goals, eODP will be linking and enhancing three existing database structures: Open Core Data (OCD), the Paleobiology Database (PBDB), and Macrostrat. Over the next three years, eODP will be accomplishing the following goals: (1) enable construction of sediment-grounded and flexible age models in an environment that encompasses the deep-sea and continental records; (2) expand existing lithology and age model construction approaches in this integrated offshore-onshore stratigraphically-focused environment; (3) adapt key microfossil data into the PBDB data model from OCD; (4) develop new API-driven web user interfaces for easily discovering and acquiring data; and (5) establish user working groups for community input and feedback. This project is targeting shipboard drilling-derived data, but the infrastructure will be put in place to allow the addition of other shore-based information. The success of eODP hinges upon interaction, feedback, and contribution of the scientific ocean drilling community, and we invite anyone interested in participating in this project to join the eODP team.

A mathematical model is considered for Rayleigh-Benard convection of mantle whose viscosity depends strongly both on temperature and pressure defined in an Arrhenius form. The model is solved numerically for extremely large viscosity variations across a unit aspect ratio cell, and steady solutions are obtained. To improve the efficiency of numerical computation, a modified viscosity law with a low temperature cut-off is used. The aim is to investigate the convection pattern with internal heating at a very high viscosity variation in the presence of high Rayleigh number. The study also investigates the relation between temperature-dependent parameter and pressure dependent parameter. The numerical simulation is done using the finite element method based PDE solver and the results are presented through figures, tables and graphs.

Segregation of liquid metal from solid silicate is a necessary pathway for core formation in a large rocky planetary body during the planet growth. The mechanism and extent of such process have an important effect on the geophysical and geochemical properties of the planetary body. Percolative flow of core forming melts through a silicate mantle has been ruled out as a possible mechanism of core formation by hydrostatic annealing experiments at pressures less than 50 GPa. However, an evolving mantle is not static, but continually deforming. Here, using element migration in the melts as an effective indicator for melt connectivity, we conclusively demonstrated that iron alloy melts could form an interconnected network in a solid bridgmanite matrix under deformation, even at a small total strain of ~0.1. Depending on the grain size of bridgmanite, percolation as a core formation mechanism could leave mantle disequilibrium/equilibrium with the core. The result showed that ~0.4 vol.% liquid metal was trapped in the silicate mantle and the stranded metal alloy could explain the highly siderophile elements (HSE) chondritic abundance in the Earth’s mantle without late veneer. Plain Language Summary We use element migration as an indicator of melt interconnection to demonstrate that core-forming melt can form an interconnected network in a bridgmanite matrix under deformation. The fast segregation velocity of melts in silicate makes the stress-induced percolation a feasible core formation mechanism. The melts left in the mantle after draining could explain the highly siderophile elements abundance in the Earth mantle.

Coral reefs are widely recognised for providing a natural breakwater effect that modulates erosion and flooding hazards on low-lying sedimentary reef islands. Increased water depth across reef platforms due sea-level rise (SLR) can compromise this breakwater effect and enhance island exposure to these hazards, but reef accretion in response to SLR may positively contribute to island resilience. Morphodynamic studies suggest that reef islands can adjust to SLR by maintaining freeboard through overwash deposition and island accretion, but the impact of different future reef accretion trajectories on the morphological response of islands remain unknown. Here we show, using a process-based morphodynamic model, that, although reef growth significantly affects wave transformation processes and island morphology, it does not lead to decreased coastal flooding and island inundation. According to the model, reef islands evolve during SLR by attuning their elevation to the maximum wave runup and islands fronted by a growing reef platform attain lower elevations than those without reef growth, but have similar overwash regimes. The mean overwash discharge across the island crest plays a key role in the ability of islands to keep up with SLR and maintain freeboard, with a value of (10 l m s) separating island construction from destruction. Islands, therefore, can grow vertically to keep up with SLR via flooding and overwash if specific forcing and sediment supply conditions are met, offering hope for uninhabited and sparely populated islands. However, this physical island response will negatively impact infrastructure and assets on developed islands.