The different olivine fabrics in ultramafic rocks have been widely used to discuss past tectonic settings, given that the olivine fabrics vary with pressure, temperature and water content. However, there are no researches that whether and how the olivine fabrics transform at different metamorphic stages in a natural rock during the process of deep subduction and exhumation. Yinggelisayi garnet lherzolites from South Altyn have experienced deep continental subduction and exhumation. The garnet lherzolites contain well-preserved residual protolith minerals, and near-peak (M1), granulite-facies retrograde (M2), and amphibolite-facies retrograde (M3) metamorphic mineral assemblages. Olivine grains in M1 formed at P–T conditions of 2.52–3.08 GPa, 1095–1136°C and low water contents (183–213 ppm H/Si), and showed [010] axes sub-normal to the foliation and [001] axes subparallel to the lineation, which is characteristic of B-type fabric ((010)[001]). Olivine grains in M2 formed at P–T conditions of 1.31–1.80 GPa, 851–893°C and also low water contents (93–139 ppm H/Si), and exhibited [010] axes sub-normal to the foliation and [100] axes subparallel to the lineation, which is characteristic of A-type fabric ((010)[100]). These observations suggest that olivine fabrics in HP-UHP metamorphosed ultramafic rocks are different in the near-peak and retrograde metamorphic stages, and also that the olivine fabrics can be transformed during deep continental subduction and exhumation. Therefore, the dispersed or no clear olivine fabric probably caused by multi-stage deformation and metamorphism, and the distinct olivine fabrics can be used as a clue to identify geological processes and better understand metamorphism and deformation during subduction and exhumation.

The preliminary information about the muon tracking by means of the GEANT4 simulations is summarized in accordance with the physics reference manual of GEANT4 10.7.

The 8.2 ka event has been extensively studied, whereas its structure is ambiguous in North China. Here we present a high-resolution (~1 year) δ18O record of annual laminated speleothem from Beijing to characterize the detailed variability across this event in North China. Our record indicates a dry 8.2 ka event spanning 8.254‒8.107 ka BP with a two-stage structure superimposed by three prominent positive excursions. The identical structure of speleothem δ18O records between North and central China during the event suggests a common forcing/response in East China, whereas the progressively increased offset between their average values may reflect changes in moisture source or rainout effect. A close comparison with the Greenland ice core records suggest a strong linear response of the Asian summer monsoon to the North Atlantic climate changes across the early and middle stages of the event, but a different mechanism in the termination process.

In this study, we apply the three-dimensional Stockwell Transform (3DST) to a novel dataset, namely airglow imager data from Rothera (68S, 68W). We use this approach to investigate small-scale high-frequency gravity waves (GWs) in the hydroxyl (OH) airglow layer, at a height $\sim$87 km in the mesosphere and lower thermosphere (MLT). MLT GWs are often underrepresented in models, being parameterised due to their small scale size and as such, the significant quantities of momentum and energy transferred by these small waves are missed. Better quantification of these waves is thus needed to support future model development. We find that the 3DST can identify waves and extract wave properties and their locations. Horizontal wavelengths are observed ranging from 10 to 40 km and vertical wavelengths of 15 to 40 km, with wave periods of 5 to 9 minutes, peaking at 7.5 minutes. These values are consistent with previous studies. Group speeds are found to be non-zero and large, implying that these GWs travel horizontally and fast. This case study demonstrates that the 3DST can be applied to airglow imager data and can successfully extract GW parameters. This is an important step in automating GW analysis in airglow.

Fine particulate matter smaller than 2.5 micrometers (PM2.5) at the surface presents large health risks to the public. Providing long-term, spatially continuous data set of PM2.5 surface concentrations can support decision making by health departments, air agencies, as well as other stakeholders interested in public health. In this work, a website-based decision support tool will be shown. The tool includes two main parts. The first part is a multi-year, daily, 3-km database for PM2.5 concentrations in California from 2006 to present in both map and tabulate formats. The second part is a daily, 3-km, near real-time update of PM2.5 surface concentrations in California in the last seven days. The near real-time data are generated within 24 hours after the NASA A-train satellite swath. For both products, PM2.5 surface estimates are generated based on a fusion of EPA ground-based monitored data and satellite-derived PM2.5 data from the NASA Aqua/MODIS satellite sensor. This decision support tool can be used to provide quick and easy visualization of certain episodic events (such as California wildfires) on a daily basis. It can also be used to conduct multi-year statistical analysis, such as identifying the higher PM2.5 concentration days above 95th percentile as the days being impacted by wildfires. These datasets and the decision support tool is publicly available and can be accessed via the SJSU HAQAST website: http://www.met.sjsu.edu/weather/HAQAST/home.html

Anthropic interventions at catchment level modify the hydrological morphology and fluxes, especially in the last 50-60 years. In the North-Eastern Romania hilly area for various reasons (the dry conditions - 400-500 mm multiannual rainfall amount – and the need for water, for wetland to arable land conversion and for flooding control), especially in the last 60 years, a big number of reservoirs were built (about 1000 in an 8000 km2 area). These reservoirs were mostly shallow (under 5 m depth) and small in volume (under 10 mil m3) and were filled in 10 to 30 years. The decommissioning of these reservoirs was made mainly through dam breaching in the median part in order to recover the filed reservoir bottom for pastures. This intervention created the conditions of channel incision of these flat surfaces and the development of gully system which tend to evolve toward continuous channels. In the present study we present a database of gullies affecting the dry bottom of decommissioned anthropic lakes from Jijia Hills, north-eastern Romania. The gullies were manually extracted from a Digital Terrain Model (DTM) with 0.5 m cell size. The extraction was performed using shading maps, with support from contour lines maps, slope maps and maps with the edge detection of slope. The gully delineation was also verified through 3D perspective view and through topographic sections, in order to obtain good delineation. We delineated more than 500 gullies, which are predominantly found on dry bottom reservoirs of 2d and 3rd Strahler order catchments. The morphometry of the gullies (length, depth, volume) is directly related to the dimension of the filled reservoir. Thus, there are lengths of 1-2 m for newly created gullies, and up to 800-1000 m for the most developed ones, with big variations of the width as a function of the shape of the gully channel and the evolution stage of gully (newly incised, evolving, fully developed). The depth of gullies ranges from 20-30 cm to 4-5 m and depends on the initial size of the reservoir, the depth of sediment fill and on the dam height. The volume of eroded sediments varies from 20 m3 to up to 70 000 m3 for individual gullies, with a total volume of eroded deposits over 1,000,000 m3. Considering the resulted volumes these types of gullies are one of the most important sediment sources in Jijia Hills region. The bottom reservoir gullies inventory and the estimated sediment volumes provide a database of hot-spots of sediment sources in the north-eastern Romania lowland. This aspect has a great practical importance considering that the majority of these gullies are not fully developed, and their further evolution implies the production of important quantities of sediments in the fluvial system. Furthermore, the same study area is defined by the presence of many dry abandoned reservoirs where the studied types of gullies can appear in the near future in the context of climate change that will increase the torrential rainfall. The presented study is a case of anthropic induced morphology and sediments accumulation (the filled reservoirs) which, through further induced anthropic decommissioning, generated gully morphology and produced sediments through erosion.

We investigate the structure and evolution of multiphase ice-ocean interfaces (‘mushy layers’) and the implications for the geophysics and habitability of ice-ocean worlds. Understanding the potential diversity of these multiphase layers across solar system bodies provides insight into the potential rates and mechanisms of heat and solute transport between their respective oceans and ice shells - which remain largely unconstrained. Additionally, variations in mushy layer properties may drive diverse geophysical processes unique to individual bodies or that may vary regionally on an individual icy world. We explore mushy layer evolution by analytically solving for the thickness of a simplified ice-ocean mushy layer system. We investigate two dynamic regimes, one driven by molecular diffusion and one driven by convection of brine within the mushy layer. We analyze the impact of gravity, thermal gradient, and ocean composition on the thickness of mushy layers. Additionally, a perturbation analysis is carried out to investigate the existence of mushy layer steady states. We show that stable mushy layers exist when ice shells are thickening, suggesting that mushy layers are likely persistent and common features of growing ice shells and accretionary regions of ice-ocean worlds.

Mechanistic representations of biogeochemical processes in ecosystem models are rapidly advancing, requiring advancements in model evaluation approaches. Here we quantify multiple aspects of model functional performance to evaluate improved process representations in ecosystem models. We compare semi-empirical stomatal models with hydraulic constraints against more mechanistic representations of stomatal and hydraulic functioning at a semi-arid pine site using a suite of metrics and analytical tools. We find that models generally perform similarly under unstressed conditions, but performance diverges under atmospheric and soil drought. The more empirical models better capture synergistic information flows between soil water potential and vapor pressure deficit to transpiration, while the more mechanistic models are overly deterministic. Additionally, both multilayer canopy and big-leaf models were unable to capture the magnitude of canopy temperature divergence from air temperature. Lastly, modeled stable carbon isotope fractionation differed under canopy water stress which illustrates the value of carbon isotopes in helping to characterize ecosystem function and elucidate differences attributable to model structure. This study demonstrates the value of merging underutilized observational data streams with emerging analytical tools to characterize ecosystem function and discriminate among model process representations.

Although the nature of the early Martian climate is a matter of considerable debate, the presence of valley networks (VN) provides unambiguous evidence for the presence of liquid water on Mars’ surface. A subaerial fluvial origin of VN is at odds with the expected phase instability of near-surface water in the cold, dry Late Noachian climate. Furthermore, many observed geomorphometric properties of VN are inconsistent with surface water flow. Conversely, subglacial channels exhibit many of these characteristics and could have persisted beneath ice sheets even in a cold climate. Here we model basal melting beneath a Late Noachian Icy Highlands ice sheet and map subglacial hydrological flow paths to investigate the distribution and geomorphometry of subglacial channels. We show that subglacial processes produce enough melt water to carve Mars’ VN; that predicted channel distribution is consistent with observations; and corroborate geomorphometric measurements of VN consistent with subglacial formation mechanisms. We suggest that subglacial hydrology may have played a key role in the surface modification of Mars.

We report the results of an extensive experimental campaign dedicated to the analysis of turbulent dispersion owing to the circulations in tidal environments, characterized by a tidal inlet and a channel with lateral tidal flats. We focus on weakly-convergent and weakly-dissipative estuaries or tidal embankments, where the internal waters communicate with the open sea through an inlet mouth. Tides are reproduced as single or multiple harmonics waves. Particle Image Velocimetry is employed to measure two-dimensional surface velocity field. Large scale macro-vortices, generated by vortex shedding during the flood phase from the inlet barrier, tend to occupy the entire tidal flats width and are completely flushed out during the ebb phase. In all experiments an intense residual current, with shape influenced by the large-scale flood vortices, is observed. The presence of large-scale vortices and of a residual current strongly influences the Lagrangian auto-correlation functions and the corresponding absolute dispersion time evolution. Looping auto-correlations are the signature of both periodic forcing and vortices, ultimately, leading to super diffusive regimes. An asymptotic Brownian regime is always found for the investigated range of parameters allowing for an estimate of the horizontal dispersion coefficients which turn out to decrease with the friction parameter and tend to be enhanced when the semi-diurnal constituents prevail. Finally, multiple particle statistics show multiple regimes depending on particle separations, compared to a typical injection length scale that seems to coincide with the inlet mouth dimension.

High pressures, along with thermal processes and irradiation, have a measurable effect on carbonaceous compounds which are found throughout the solar system. High pressure environments, such as those generated by impacts, occur frequently during the evolution of the solar system, and the effects of pressure on the carbonaceous materials present can influence the subsequent chemistry of the body. In situ high pressure synchrotron source Fourier Transform Infrared (FTIR) spectroscopy coupled with computational models has been used to directly study the effects of pressure on carbonaceous materials. Our work using these techniques investigates the specific case of structural sugars, where ribose and deoxyribose have differing responses to high pressures. These particular carbonaceous materials play a key role in the prebiotic chemistry of the early Earth as constituents of the bioinformational molecules ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) respectively. Ribose is substantially less stable than deoxyribose at pressures exceeding 14 GPa and shows less recovery on decompression. Our results imply that the modest impacts experienced throughout the solar system could substantially alter the carbonaceous payload of many bodies, with consequences for any prebiotic chemistry.

Mapping Titan’s surface albedo is a necessary step to give reliable constraints on its composition. However, even after the end of the Cassini mission, surface albedo maps of Titan, especially over large regions, are still very rare, the surface windows being strongly affected by atmospheric contributions (absorption, scattering). A full radiative transfer model is an essential tool to remove these effects, but too time-consuming to treat systematically the ~50000 hyperspectral images VIMS acquired since the beginning of the mission. We developed a massive inversion of VIMS data based on lookup tables computed from a state-of-the-art radiative transfer model in pseudo-spherical geometry, updated with new aerosol properties coming from our analysis of observations acquired recently by VIMS (solar occultations and emission phase curves). Once the physical properties of gases, aerosols and surface are fixed, the lookup tables are built for the remaining free parameters: the incidence, emergence and azimuth angles, given by navigation; and two products (the aerosol opacity and the surface albedo at all wavelengths). The lookup table grid was carefully selected after thorough testing. The data inversion on these pre-computed spectra (opportunely interpolated) is more than 1000 times faster than recalling the full radiative transfer at each minimization step. We present here the results from selected flybys. We invert mosaics composed by couples of flybys observing the same area at two different times. The composite albedo maps do not show significant discontinuities in any of the surface windows, suggesting a robust correction of the effects of the geometry (and thus the aerosols) on the observations. Maps of aerosol and albedo uncertainties are also provided, along with absolute errors. We are thus able to provide reliable surface albedo maps at pixel scale for entire regions of Titan and for the whole VIMS spectral range.

The crystal orientation fabric of glacier ice severely impacts its strength and flow. Crystal fabric is therefore an important consideration when modelling ice flow. Here, we show that shear wave splitting (SWS) of glacial microseismicity can be used to invert for seismic anisotropy and ice fabric at Rutford Ice Stream (RIS). RIS is a fast-flowing Antarctic ice stream, a setting crucial for informing flow models. We present ~2000,000 SWS measurements from glacial microseismicity, registered at a 38-station seismic network located ~40 km upstream the grounding line. A representative subset of this data is inverted for ice fabric. Due to the character of SWS, which accumulates along the ray path, our method works best if additional information on the depth structure of the ice is available, which are radar measurements in our case. We find that the following three-layer model fits the data best: a broad vertical cone near the base of RIS (500 m thick), a thick vertical girdle, orientated perpendicular to flow, in the middle (1200 m thick) and a tilted cone fabric in the uppermost 400 m. Such a fabric causes a depth-dependent strength profile of the ice with the middle layer being ~3.5 times harder to deform along flow than across flow. At the same time, the middle layer is a factor ~16 softer to shear than to compression or extension along flow. If such a configuration is representative for fast-flowing ice streams, it would call for a more complex integration of viscosity in ice sheet models.

The subpolar North Atlantic is a site of significant carbon dioxide, oxygen, and heat exchange with the atmosphere. This exchange, which regulates transient climate change and prevents large-scale hypoxia throughout the North Atlantic, is thought to be mediated by vertical mixing in the ocean's surface mixed layer. Here we present observational evidence that waters deeper than the conventionally defined mixed layer are affected directly by atmospheric forcing. When northerly winds blow along the Irminger Sea's western boundary current, the Ekman response pushes denser water over lighter water and triggers slantwise convection. We estimate that this down-front wind forcing is four times stronger than air--sea heat flux buoyancy forcing and can mix waters to several times the conventionally defined mixed layer depth. Slantwise convection is not included in most large-scale ocean models, which likely limits their ability to accurately represent subpolar water mass transformations and deep ocean ventilation.

We report the first Terrestrial Electron Beam detected by the Atmosphere‐Space Interactions Monitor. It happened on 16 September 2018. The Atmosphere‐Space Interactions Monitor Modular X and Gamma ray Sensor recorded a 2 ms long event, with a softer spectrum than typically recorded for Terrestrial Gamma ray Flashes (TGFs). The lightning discharge associated to this event was found in the World Wide Lightning Location Network data, close to the northern footpoint of the magnetic field line that intercepts the International Space Station location. Imaging from a GOES‐R geostationary satellite shows that the source TGF was produced close to an overshooting top of a thunderstorm. Monte‐Carlo simulations were performed to reproduce the observed light curve and energy spectrum. The event can be explained by the secondary electrons and positrons produced by the TGF (i.e., the Terrestrial Electron Beam), even if about 3.5% to 10% of the detected counts may be due to direct TGF photons. A source TGF with a Gaussian angular distribution with standard deviation between 20.6° and 29.8° was found to reproduce the measurement. Assuming an isotropic angular distribution within a cone, compatible half angles are between 30.6° and 41.9°, in agreement with previous studies. The number of required photons for the source TGF could be estimated for various assumption of the source (altitude of production and angular distribution) and is estimated between 1017.2 and 1018.9 photons, that is, compatible with the current consensus.

Hydroclimate variability of the southwest United States (SWUS) is influenced by the tropical Pacific Ocean, particularly the phase of the El Niño/Southern Oscillation (ENSO), via teleconnections, which are expected to be altered by climate change. However, natural variability in this teleconnection has not been robustly quantified, complicating the detection of anthropogenic climate change. Here, we use a linear inverse model (LIM) to quantify natural variability in the ENSO-SWUS teleconnection. The LIM yields realistic teleconnection patterns with century-scale variability in teleconnection strength comparable to simulations from the Last Millennium Ensemble project and the Coupled Model Intercomparison Project Phases 5 and 6. The variability quantified by the LIM illuminates two aspects of our understanding of ENSO and its impacts: the inherent statistics of the observable system can produce century-long periods of nonsignificant correlation, and detecting changes in ENSO-related hydroclimate variability is challenging in a changing climate.

We investigate the rare events of sudden appearances of relativistic electrons (>700 keV), which are normally confined to the Van Allen belts, in the slot region. The frequency of occurrence of these events are on average 1-2 per year. To cope with the scarcity of events, in this study we examine 21 years of trapped relativistic electron fluxes available from the POES and MetOp Space Environment Monitor (SEM‐2). Our statistical analysis show that these events can occur even during moderate geomagnetic activity. Occurrence of these events correlates with high speed solar winds or ICMEs depending on the phase of the solar cycle. Most importantly, we show that ULF wave activity plays a significant role in causing these events and the events could be predicted in 75% of the cases.

Mass-extinction with instantaneous and short-term effects on extreme climate and deteriorated ocean environment across the Cretaceous/Paleogene boundary (K/PgB) has been verified by an array of geological records, however, a longer-term (~100−1000 Kyr) post-K/PgB variation remain poorly understood, particularly due to the scarcity of terrestrial records. This study presents carbon isotope analyses of pedogenic carbonates in the Nanxiong Basin, South China to reconstruct carbon cycles and atmospheric CO2 concentrations (pCO2) spanning 70.0–62.0 Ma. Combined with data from Songliao Basin (China) and Tornillo Basin (USA), δ13C displays a post-K/PgB (66.0-64.5 Ma) vibration that is correlative to the surface ocean but mirroring to the bottom ocean. The vibration shows a pattern of collapse and smooth towards rebound, constituting a process of ~400 Kyr (millennia) deterioration, ~300 Kyr stabilization and ~800 Kyr recovery for the longer-term ecosystem and environment. A similar pattern is observed for the reconstructed pCO2, correlating to changes of sea surface temperature (SST) but contrasting bottom water temperature (BWT). With the discrepancy of longer-term proxy variations, it is proposed that ecosystems and environments in terrestrial and surface ocean had experienced a more unstable, difficult and erratic recovery process and were much more sensitive to climatic changes than in deep ocean for ~1.5 million years in the aftermath of the end-Cretaceous mass extinction. In addition, the decoupling of proxy variations from expected effects implies Deccan volcanism and Chicxulub impact may not have played a key role in the longer-term CO2 perturbation and environmental change following the K/PgB.