Explosive mafic eruptions are among Earth’s most hazardous volcanic phenomena due to the rapid ascent rates of mafic magma limiting time for early detection and warning systems. To date, work on explosive mafic eruptions has primarily been in the context of conduit and mafic magma fragmentation processes. Our work uses geochemistry and numerical modeling to establish magma source and system dynamics that led to an explosive mafic eruption at Llaima volcano, Chile. This study compares major and trace elements of 70 whole rock ignimbrite samples collected from 17 different outcrops of the Curacautin ignimbrite, including four extensive outcrops sampled vertically every 1-3 m to examine chemical variations and changes in magma source prior to and during the eruption. The bases and tops of the four stratigraphic sections and four additional samples with unique chemical signatures were analyzed for Sr-Nd-Pb isotopes to investigate mantle source variation. Eruptive products of the Curacautin eruption define a medium-K calc-alkaline suite of basalt to andesite (SiO2 50-58 wt. %). Both regionally and stratigraphically, trace element patterns produced remarkably similar, parallel patterns with the most enriched sample in the west where the base of the ignimbrite is exposed (LaN/SmN = 1.63). The Curacautín ignimbrite is chemically heterogeneous [e.g., MgO=2.5-6 wt. %, Ce = 11-39 ppm, and Ba/Th= 170-263], but Pb isotopes are homogeneous (207Pb/204Pb = 15.59-15.61), indicating the magma source was influenced by slab inputs or secondary process (e.g., AFC). However, Sr-Nd isotopes still need to be collected. To constrain mantle source heterogeneity, we utilize hierarchical clustering analysis (HCA). HCA results indicate four chemically distinct groups in the north, two in the east, and two in the west. To explore secondary processes, Magma Chamber Simulator (MCS; Bohrson et al., 2014) modeling will be used to produce thermodynamic models to constrain the chemical variability resulting from fractional crystallization (FC) processes.

The dynamics of slab detachment and associated geological fingerprints have been inferred from various numerical and analogue models. These invariably use a setup with slab-pull-driven convergence in which a slab detaches below a mantle-stationary trench after the arrest of plate convergence due to arrival of continental lithosphere. In contrast, geological reconstructions show that post-detachment plate convergence is common and that trenches and sutures are rarely mantle-stationary during detachment. Here, we identify the more realistic kinematic context of slab detachment using the example of the India-Asia convergent system. We first show that only the India and Himalayas slabs (from India’s northern margin) and the Carlsberg slab (from the western margin) unequivocally detached from Indian lithosphere. Several other slabs below the Indian Ocean do not require a Neotethyan origin and may be of Mesotethys and Paleotethys origin. Additionally, the still-connected slabs are being dragged together with the Indian plate forward (Hindu Kush) or sideways (Burma, Chaman) through the mantle. We show that Indian slab detachment occurred at moving trenches during ongoing plate convergence, providing more realistic geodynamic conditions for use in future numerical and analogue experiments. We identify that the actively detaching Hindu Kush slab is a type-example of this setting, whilst a 25-13 Ma phase of shallow detachment of the Himalayas slab, here reconstructed from plate kinematics and tomography, agrees well with independent, published geological estimates from the Himalayas orogen of slab detachment. The Sulaiman Ranges of Pakistan may hold the geological signatures of detachment of the laterally dragged Carlsberg slab.

The Glass Window Bridge Located in Eleuthera, The Bahamas, is the only bridge connecting Eleuthera’s northern and southern mainland, facing the Atlantic Ocean to the east and the Great Bahama Bank to the west. This bridge is under constant threat from hurricanes and large swells in the Atlantic Ocean. The existing bridge has been subject to severe damage arising from wave impact forces since its construction. In addition, severe overtopping of the cliffs near the Glass Window Bridge causes damage to the roads and severe erosion, that over the years has created unique geologic features. As the global climate warms and sea level rises (SLR), coastal areas will be subject to more extreme flooding and intense hurricanes. Therefore, assessing the impact of potential SLR on the GW bridge and guiding bridge wave mitigation measures are of crucial need. A 3D Digital Terrain Model (DTM) of the bridge site and adjacent ocean bathymetry is constructed from satellite data. This study develops a multiphase computational fluid dynamics (CFD) model based on the DTM to study the impact of wave-breaking for three major historical storm events, and for three different estimates of SLR for the year 2100. Our results suggest that, due to SLR, the islands are subjected to increased overtopping, which occurs even during normal wave conditions. Notably, nonlinear increases in wave splash extent and wave-induced bridge loads are observed as SLR increases. Our results indicate that SLR additionally magnifies the erosional energy, accelerating further changes in the geological features of the island.

This work constructs multiple regression equations of surface ozone concentration based on non-linear combinations of high temporal frequency and multi-year measurements of air pollutant concentrations (PM2.5, CO, NO2, SO2) and remotely sensed ultraviolet Index (UVI) in nine different urban regions in China. These nine regions all have different emissions profiles, economic drivers, and climatology, allowing a more rigorous investigation of the factors most responsible to local surface ozone. The results show a good fit of ozone can be made temporally (including many peaks and troughs), under conditions ranging from relatively clean through polluted, with minimum and maximum bounds on the goodness of the fit usually in the range from 5 to 130 ug/m3. Overall, the results demonstrate significant differences in terms of the most important driving factors in the different cities, with UV radiation being most important in all cities, followed by CO, PM2.5, and NO2 or a combination, depending on each individual city. The performance of the ozone prediction and real measurements under both clean and polluted conditions of PM2.5 or CO mass concentrations are further explored and found to match very well in Xi’an and Beijing. Discussion is presented and supported to quantify insights into why solar ultraviolet radiation coupled with easier to measure longer-lived air pollutants contribute a significant amount to surface ozone is possible, all without needing to necessarily at first order wade into the extremely complex chemistry and physics involved with boundary layer meteorology and VOC chemistry.

Five of California’s ten largest wildfires occurred in 2020, with the largest complex shattering the previous record by more than 100 %. The year follows a decade containing extraordinary fire activity. Trend investigations focused on changes in human activities and atmospheric thermodynamics, while the impacts of changing atmospheric dynamics are largely unknown. Here we identify extreme weather types (XWTs) associated with historically large daily burned areas in eight Californian regions. These XWTs characterize dominant fire weather regimes varying in fire behavior types (plume-driven vs. wind-driven fires) and seasonality. 2020’s exceptional fires partly occurred during previously unrecognized XWTs, whose characteristics and recurrence intervals were largely unknown. Most of the strongly large-scale forced XWTs such as Santa Ana and Diablo events increased in frequency during the 20th century particularly in the Sand Diego and Bay Area region. These changes are likely not anthropogenically caused and predominantly due to climate internal variability. However, raising greenhouse gas concentrations significantly decrease thermal low XWTs in southern and increase them in central California. These XWTs occur during the hottest time in the year and will alter fire risk in the summer season.

Several geological evidences, such as tidal rhythmites and bivalve shells, allow to track back the evolution paths of both the major semiaxis of the Moon's orbit and the Earth's spin rate. However, the data is scarce and with large uncertainty and the orbital evolution of the Moon is still controversial. The aim of this work is to evaluate how significant could have been the effect of bodily tides on the Earth's mantle thermal evolution. To this end, different thermal models of the Earth's interior were proposed. We explore plate tectonics and stagnant lid regimes. These models take into account both tidal and radiogenic heat sources. In order to compute tidal dissipation, we made use of three realistic rheological models of Earth mantle and proposed three different dynamical evolution paths for the lunar major semiaxis and terrestrial length of day. It was found that the impact of tidal interaction could have been specially appreciable on the first hundreds million of years of the Earth's history, provided that the mantle was at a higher temperature. In addition, we found that thermal evolution of Earth's interior is mainly controlled by the rheological behavior of the mantle, which controls the amount of tidal heat produced, and by the dynamical evolution of the Earth-Moon system.

Understanding the complex interplay between erosional and depositional processes, and their relative roles in shaping landscape morphology is a question at the heart of geomorphology. A unified framework for examining this question can be developed by simultaneously considering terrain elevation statistics over multiple scales. We show how a long-standing tool for landscape analysis, the elevation-area or hypsometry, can be complemented by an analysis of the elevation scalings to produce a more sensitive tool for studying the interplay between processes, and their impact on morphology. We then use this method, as well as well-known geomorphic techniques (slope-area scaling relations, the number of basins and basin size as a function of channel order) to demonstrate how the complexity of an experimental landscape evolves through time. Our primary result is that the complexity increases once a flux equilibrium is established as a consequence of the role of diffusive processes acting at intermediate elevations. We gauge landscape complexity by comparing results between the experimental landscape surfaces and those produced from a new algorithm that fixes in place the elevation scaling statistics, but randomizes the elevations with respect to these scalings. We constrain the degree of randomization systematically and use the amount of constraint as a measure of complexity. The starting point for the method is illustrated in the figure, which shows the original landscape (top-left) and three synthetic variants generated with no constraints to the randomization. The value quoted in these panels is the root-mean-squared difference in the elevation values for the synthetic cases relative to the original terrain. This value is greatest where the original ridge becomes a valley. All these landscapes contain the same elevation values (i.e. the same probability distribution functions), and the same elevation scalings at a point. The differences emerge because the elevations themselves are distributed randomly across the surface.

The separation of contributions from different sources in the magnetic field signal measured at satellite altitude is an open challenge. An approach to this problem, using Principal Component Analysis, is here applied to geomagnetic external field series at Virtual Observatories (VO). These series are computed from an enlarged dataset of Swarm data covering all local times and all geomagnetic activity levels between January 2014 and December 2019. For each 30-days time window, the Equivalent Source Dipole technique is used to reduce all measurements inside a cylinder to one single ‘observation’ at its axis and 500 km altitude. Our results reveal a first principal mode with dipolar geometry and time variation following very closely the RC-index of geomagnetic activity. They display a resolved second principal mode with annual periodicity and of approximately zonal quadrupolar radial pattern, reminiscent of results in a previous study using VO series from a filtered satellite dataset and with lower time resolution. We resort to the recent comprehensive model CM6 to identify a possible source for this second mode. We propose that the dipolar mode is the expression of the magnetospheric ring current dynamics, at 30-day time resolution, and the quadrupolar mode is the expression of the annual asymmetry between local summer and winter Sq current vortices. Two fainter modes could be related to the equinoctial amplification of Sq vortices and the ionospheric dynamo modulation by nonmigrating tides. We show that a more uniform local time sampling could contribute to better resolve ionospheric structures.

The relationship between aerosol concentration and lightning is complex. Aerosols can act as cloud condensation nuclei, contributing to the formation of cloud droplets, cloud electrification and lightning, while high concentrations of aerosols can contribute to a decrease in lightning due to radiative effects. Meteorology plays a dominant role in lightning activity, distorting the effect of aerosols. More measurements, as presented here, are needed to establish the complex relationship between aerosols and lightning. The Po Valley, a heavily industrialized region, was highly affected by the COVID-19 lockdown. The reduction of non-essential activities and mobility coincided with a significant drop in pollutant concentrations and lightning. We investigate the relationship between lightning, meteorology and aerosols. We find that the variation in lightning during the lockdown cannot be fully attributed to meteorology. $\sim$60\% of the observed decrease can be attributed to meteorology, and $\sim$40\% to the reduction in aerosol emissions.

Because rocks and ices viscosities strongly depend on temperature, planetary mantles and ice shells are often thought to be animated by stagnant-lid convection. Their dynamics is further impacted by the release of internal heat either through radioactive isotopes decay or tidal dissipation. Here, we quantify the impact of internal heating on stagnant-lid convection. We performed numerical simulations of convection combining strongly temperature-dependent viscosity and mixed (basal and internal) heating in 3D-Cartesian and spherical geometries, and used these simulations to build scaling laws relating surface heat flux, Φsurf, interior temperature, Tm, and stagnant lid thickness, dlid, to the system Rayleigh number, heating rate, H, and top-to-bottom viscosity ratio, Δη. These relationships show that Tm increases with H but decreases with Δη, while Φsurf increases with H and Δη. Importantly, they also describe heterogeneously heated systems well, provided that the maximum dissipation occurs in hottest regions. For H larger than a critical value Hcrit, the bottom heat flux turns negative and the system cools down both at its top and bottom. Two additional interesting results are that 1) while the rigid lid stiffens with increasing H, it also thins; and 2) Hcrit increases with increasing Δη. We then use our scaling laws to assess the impact of tidal heating on Europa’s ice shell properties and evolution. Our calculations suggest a shell thickness in the range 20-80 km, depending on viscosity and dissipated power, and show that internal heating has a stronger influence than the presence of impurities in the sub-surface ocean.

Pulsating auroras (PsAs) are considered to be caused by energetic (~10 keV) electron precipitations. Additionally, soft electron precipitations (~1 keV) have often been observed in PsAs. These soft electron precipitations enhance the electron density in the ionospheric F region. However, to date, the relationship between PsAs and soft electron precipitation has not been well understood. In this study, using the data taken by the European incoherent scatter radar and the auroral all-sky imager at Tromso;, we conducted two case studies to investigate, in detail, the relationship between the electron density height profile and the type of aurora. Additionally, we conducted statistical studies for 14 events to elucidate how often F region electron density enhancement occurs with a PsA. We consequently found that 76% of electron density height profiles showed a local peak in the F region, with electron temperature enhancements. It was also found that 89% of the F region peak altitudes were above the peak altitude of the ionization rate produced by electrons of characteristic energy below 100 eV. The occurrence rate of these profiles in the hourly magnetic local time (MLT) exceeded 80% in the 22–3 MLT sectors. We suggest that the electron density enhancement in the F region would have been caused by electrostatic electron cyclotron harmonic waves in the magnetosphere. Another candidate would have been polar patches that had traveled from the dayside ionosphere.

Well integrity failure resulting in migration of natural gas outside of the surface casing can cause atmospheric greenhouse gas emissions and groundwater quality impacts from existing and historic energy wells. Spatial and temporal variability in gas migration can result in errors in detection (i.e., presence/absence) and efflux estimations. This field-based case study used automated dynamic closed chambers to record repeated (~ every 18 minutes) CO2 and CH4 efflux measurements over a two-week period around a single petroleum production well in Alberta, Canada. Long-term efflux measurements supplemented soil gas compositional and isotopic characterization, along with surface concentration measurements. Effluxes were spatially concentrated around the wellhead and only occasionally detectable more than a few meters away. Estimated total emissions attributable to gas migration ranged from 48 - 466 g CH4 d-1 (or 0.07 - 0.7 m3 CH4 d-1). Methane effluxes and concentrations were temporally variable on second-to-hourly and diel scales. Multivariate stepwise regression analysis indicates that multiple meteorological factors, particularly wind speed and air temperature, were related to the temporal variability. Despite temporal variability, elevated concentrations and effluxes were consistently detectable around the well. Major soil gas composition suggests that gas migration near the wellhead causes advective displacement of soil gas, while more distal measurements are indicative of episodic and diffusion-dominated transport. Values of 13C-CO2 and 13C-CH4 samples were consistent with CH4¬ oxidation within the unsaturated zone. Although these results reflect a single well, the findings are salient to gas migration detection and emission estimation efforts.

A new augmented Ensemble of Data Assimilations (EDA) technique to estimate background error covariances (B-matrix) has been developed for the Copernicus European Regional Re-Analysis (CERRA). The B-matrix is modelled on a bi-Fourier limited area model. Background errors are assumed isotropic, homogeneous and non-separable. Linearised geostrophic and hydrostatic balances are incorporated as multivariate relationships, coupling vorticity and geopotential extended to mass-wind and specific humidity fields via the f-plane approximation. The B-matrix is estimated by a new 10-member CERRA-EDA system, temporally tethered to real-time meteorological situations. The EDA forecast differences comprise two main pools: seasonal and daily. The seasonal component is pre-prepared at reanalysis-resolution (5.5km). The new augmentation governs real-time mixture of winter and summer differences. The daily component is an 11km moving 2.5 day average. B-matrix re-estimation occurs every 2 days, with a fixed split of 80-20\% seasonal-daily. We consider a case study to illustrate the potential of CERRA-EDA to estimate weather regime change. The most influential factors are temporal evolution of spatial observation coverage, and varying the seasonal-daily split. Background error statistics, improvements in analysis and forecast skill scores and overall assimilation system performance are shown and discussed.

We report on the relationship between pulsating aurora and relativistic electron microburst using simultaneous observations of ground-based fast auroral imagers with the FIREBIRD-Ⅱ CubeSat for the first time. We conducted a detailed analysis of an event on October 8, 2018 and found that the occurrence of a pulsating aurora with internal modulations corresponds to the flux enhancement of electrons with energy ranging from 219.7 to 984.95 keV detected with Flight Unit 4, one of FIREBIRD’s CubeSat, with a time delay of 525 ms. Assuming that the pulsating aurora was produced by 10-keV electrons, we suggest that this time difference of 525 ms is consistent with the theory by Miyoshi et al. (2020) that a pulsating aurora and microburst occur due to the chorus waves at different latitudes along the same field line.

Understanding of the tropical atmosphere is elaborated around two elementary ideas, one being that density is homogenized on isobars, which is referred to as the weak temperature gradient (WTG), the other being that the vertical structure follows a moist-adiabatic lapse rate. This study uses simulations from global storm-resolving models to investigate the accuracy of these ideas. Our results show that horizontally the density temperature appears to be homogeneous, but only in the mid- and lower troposphere (between 400 hPa and 800 hPa). To achieve a homogeneous density temperature, the horizontal absolute temperature structure adjusts to balance the horizontal moisture difference. Thus, water vapor plays an important role in the horizontal temperature distribution. Density temperature patterns in the mid- and lower troposphere vary by about 0.3 K on the scale of individual ocean basins, but differ by 1K among basins. We use equivalent potential temperature to explore the vertical structure of the tropical atmosphere and we compare the results assuming pseudo-adiabat and the reversible-adiabat (isentropic) with the effect of condensate loading. Our results suggest that the tropical atmosphere in saturated convective regions tends to adopt a thermal structure that is isentropic below the zero-degree isotherm and pseudo-adiabatic above. However, the tropical mean temperature is substantially colder, and is set by the bulk of convection which is affected by entrainment in the lower troposphere.

Eastern Asia is a prime location for the study of intracontinental tectono-magmatic activity. For instance, the origin of wide-spread intraplate volcanism has been one of the most debated aspects of East Asian geological activity. Measurements of attenuation of teleseismic phases may provide additional constraints on the source regions of volcanism by sampling the upper mantle. This study uses data from three seismic arrays to constrain lateral variations in teleseismic P-wave attenuation beneath the Central Orogenic Belt and the North China Craton. We invert relative observations of attenuation for a 2-D map of variations in attenuation along with data and model uncertainties by applying a Hierarchical Bayesian method. As expected, low attenuation is observed beneath the Ordos block. High attenuation is observed beneath most of the volcanoes (e.g., the Middle Gobi volcano, the Bus Obo volcano and the Datong volcano) in the study area, and estimated asthenospheric Qp values span from 95 to 200. These values are within the range of globally average asthenosphere. We infer that these volcanoes may tap melt from ambient asthenosphere and occur where the lithosphere is thin, which is consistent with previous petrologic studies. More complex mantle drivers of volcanism are not rejected but are not needed to explain eruptions in this area. In contrast, at the Xilinhot-Abaga volcanic site, the observed low attenuation (as low as beneath the Ordos block) excludes a typical shallow melting column. Fluids from the subducted Pacific plate may initiate the deep melting and would be consistent with petrological constraints.

The Upper and Lower Quinn River subbasins (HUC-8 16040201,16040202) comprise one of the largest single drainages in northwest Nevada. The sub-basins cover approximately 1.7 million hectares. The Quinn river originates in the Montana Mountains and Santa Rosa Range and drains to the Black Rock Desert Playa. The elevational gradient ranges from 2000 m to 1100 m. Sagebrush and perennial grasses dominate the higher elevations, with the lowlands being dominated by greasewood, saltbrush, and desert scrub. This presentation examines the human habitation in the sub-basins over the past 13,000 years in context to the palaeoclimatic records from the sub-basins and adjoining areas. Over 1100 prehistoric sites exist in the study area, with 19 sites having been excavated and yielding 108 radiocarbon dates. Palaeoclimate proxies from the study area include the Mud Meadows and Summit Lake pollen cores, and the Jackson Mountain tree ring widths. While the radiocarbon record shows numerous gaps between 13 kBP and 5 kBP, the summed probability distribution of calibrated radiocarbon dates suggests continuous occupation from 5 kBP to 1 kBP with exponential growth. Based on the abundance of Chenopodiaceae pollen in the Summit Lake core, the study area is drier than today during the Late Holocene Drought (LHD, ca. 2.5 to 1.9kBP). During the LHD, sites south of 41N are abandoned or see no growth; northwards, sees site growth. Despite contrasting climatic conditions, the Late Antique Little Ice Age (LALIA) and the Medieval Climatic Anomaly (MCA) are both periods of site occupation and growth across the sub-basins. Occupied sites are found throughout the sub-basins during the LALIA, and during the MCA site occupation is focused at Trego hot springs and at higher elevations. As evidenced by the three palaeoclimate proxies from the sub-basins, the Little Ice Age is a period of cooler temperatures and increased moisture. Despite the ameliorated conditions, the number of dated sites significantly decreases. This may reflect a more dispersed settlement pattern with lower numbers of residents during the Terminal Prehistoric period.

Most countries around the world took actions to control COVID-19 spread that included social distancing, limiting air and ground travel, closing schools, suspending sports leagues, closing factories etc., leading to economic shutdown. The reduced traffic and human movement compared to Business as Usual (BAU) scenario was tracked by Apple and Android cellphone use; the data showed substantial reductions in mobility in most metropolitan areas. For example in Washington D.C., average distance traveled by people was ~13 km and by April when lockdown was in full effect, the distance reduced to ~5 km. Consistent with reduced mobility, air quality as indicated by satellite observations decreased substantially. Granted that year to year variability in weather patterns can have influence on observed NO2 and aerosol concentrations, but the drop in tropospheric nitrogen dioxide (NO2) observed by Sentinel 5P Tropospheric Ozone Monitoring Instrument (TROPOMI) and Suomi NPP Ozone Mapping Profiling Suite (OMPS) observations of NO2 was significant; reductions in observed NO2 were between 15% to 50% between February and April 2020 depending on location and similar reductions in NO2 amount in March and April 2020 compared to March and April 2019. Further, the changes in NO2 across the continental U.S. between 2020 and 2019 correlated well with on-road emissions but did not correlate with changes in emissions from power plants. In the first quarter of 2020, the total amount of NOx emitted on road were 200 times and 7 times larger than that from power plants in LA and NYC, respectively. These findings confirm that power plants are no longer the major source of NO2 in the United States. We also found positive correlation between NO2 and Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS) aerosol optical depth measurements in these urban regions indicating common source sectors for NO2 and aerosols/aerosol precursors.