We simulated tsunami propagation for several scenario slip distributions for the 1938 MW 8.3 earthquake along the Alaska Peninsula, and compared these to the observed records at Unalaska/Dutch Harbor and Sitka. The Sitka record is sensitive to the depth of slip but not the along-strike location, and is fit best by slip at shallow depth. The Unalaska record is sensitive mainly to the along-strike location of slip, and is fit best by slip that is concentrated in the eastern part of the presumed 1938 rupture zone. The tsunami data show that the actual 1938 earthquake rupture zone was smaller than previously thought, likely ~200 km in length, and had no slip near the Shumagin Islands or in the 2020 Simeonof earthquake’s rupture zone. The rupture models that best predict the 1938 tsunami lie within the region of high present day slip deficit inferred from GPS.

Launched in October 2018, the ESA/JAXA BepiColombo mission is currently in cruise to reach Mercury in late 2025. The Mercury Orbiter Radioscience Experiment (MORE) is one of the 16 instruments hosted on board the spacecraft. Testing general relativity is among the primary objectives of MORE. Superior conjunction experiments (SCE) will be performed during the interplanetary trajectory, with the aim of obtaining an accurate estimate of the post-Newtonian parameter γ. This is allowed by MORE advanced radio tracking system which provides precise range and Doppler data almost at all solar elongation angles, thus enabling an accurate measure of the relativistic time delay and frequency shift undergone by the signal when the spacecraft is in a superior solar conjunction (SSC). The rst BepiColombo SCE will take place in March 2021, and others will follow during the cruise phase. The nal objective is to place new limits to the accuracy of the general relativity as a theory of gravity in the weak eld limit, improving previous result from the Cassini SCE (Bertotti et al. 2003), which was able to determine that γ-1=(2.1±2.3)×10-5. Because of the proximity to the Sun, the spacecraft will undergo severe solar radiation pressure acceleration, and the effect of the random uctuations of the solar irradiance may become a major concern. We address the problem of a realistic estimate of the outcome of the SCE of BepiColombo, by including the effects of solar irradiance random variations in the dynamical model. We analyzed the experiment under different assumptions on the ranging system performances, observation coverage and solar activity showing their impact on the attainable result. We propose a numerical method to mitigate the impact of the variable solar radiation pressure on the scienti c result. Our simulations show that, exploiting data from multiple SSCs, the accuracy obtainable in the relativistic time delay measurement is 13×10-6 for a strong solar activity, and 6×10-6 for weak irradiance uctuations. We found that the latter result can be obtained by the rst SSC alone if the plasma noise calibration works until the impact parameter reaches 6 solar radii.

Previous studies of freshwater lenses in saline aquifers adjoining gaining rivers (“riparian lenses”) have so far considered only rivers that fully penetrate the aquifer, whereas in most cases, rivers are only partially penetrating. This paper presents a new methodology for obtaining the saltwater discharge and the shape of a steady-state, non-disperive riparian lens, where the river is partially penetrating, combining two previous analytical solutions. The resulting analytical solution is compared to numerical modelling results to assess assumptions and the methodology adopted to approximate the “turning effect”, which is the change in groundwater flow direction (horizontal to vertical) near the partially penetrating river. A range of conditions are analysed, constrained by parameters adopted previously for River Murray floodplains (Australia). Consistency between analytical and numerical results highlight the capability of the proposed analytical solution to predict the riparian lens geometry and saltwater discharge into partially penetrating rivers. The sensitivity analysis indicates that larger riparian lenses are produced adjacent to the deeper and wider rivers, as expected. The change in width or depth of the river has more influence on the saltwater discharge and the horizontal extent of the riparian lens (and less effect on the vertical extent of the lens adjacent to the river) for shallower and narrower rivers. This research highlights the utility of the new method and demonstrates that the assumption of a fully penetrating river likely leads to significant overestimation of the saltwater discharge to the river and the riparian lens horizontal extent and vertical depth.

On 30 December 2021, the Marshall Fire devastated the Boulder, Colorado region. The fire initiated in fine fuels in open space just southeast of Boulder and spread rapidly due to the strong, downslope winds that penetrated into the Boulder Foothills. Despite the increasing occurrence of wildland-urban interface (WUI) disasters, many questions remain about how fires progress through vegetation and the built environment. To help answer these questions for the Marshall Fire, we use a coupled fire-atmosphere model and Doppler on Wheels (DOW) observations to study the fire’s progression as well as examine the physical drivers of its spread. Evaluation of the model using the DOW suggests that the model is able to capture general characteristics of the flow field; however, it does not produce as robust of a hydraulic jump as the one observed. Our results highlight limitations of the model that should be addressed for successful WUI simulations.

The summer atmospheric river (AR) frequency over East Asia and Western North Pacific (EA-WNP) is investigated by multiple AR detection algorithms based on the Atmospheric River Tracking Method Intercomparison Project (ARTMIP) Tier2 reanalysis dataset. The results show that AR frequency during the recent four decades experienced opposite interdecadal shifts, greatly contributing to the interdecadal equatorward trends of EA ARs and poleward trends of WNP ARs with a boundary around 135°E. The opposite variations are mainly influenced by a zonal dipole of integrated water vapor transport with cyclonic and anticyclonic anomalies centered over Taiwan and the ocean to the southeast of Japan, respectively. A major impact of the Pacific Decadal Oscillation and a reinforcement effect due to a zonal wave train from the North Atlantic jointly modulate the pattern. Considering ARs may curve their pathway over EA-WNP, the algorithms based on historical AR shapes should be cautiously used during AR detection.

Majority of currently applied environmental models relay on linear relations between environmental endmembers. In this research, a detailed and comprehensive comparison between linear (L) and non-linear (NL) models are presented. The L and NL models are realized in a framework of Artificial Neural Networks (ANN). The evolution process of the ANN-L and ANN-NL models is based on estimation of fractional snow cover through data-fusion between high resolution (IKONOS) and medium resolution (Landsat TM/ETM+) remotely sensed images. The statistical measure values of R2, RMSE, MAE, Accuracy, Precision, Recall, and Specificity indicate better performance of the ANN-NL model in comparison to the ANN-L in estimation of ANN Landsat-FSC. The presented results, strongly indicate that to fully capture, untangle, and characterize internal environmental relations high-sensitivity non-linear models are required. Non-linear relations are particularly visible the complex in alpine-forested environments.

By difference treatment of the rate of change of the radial distance, the interchange relationship between the Doppler shift and the path difference is obtained, so that the Doppler shift can be used to obtain the path difference in an equivalent way. On this basis, by using the linear solution of the double-base linear array and constructing a virtual double-base array, a Doppler direction finding method using only the single-base array is obtained. Because the transformation method based on frequency shift and path difference avoids the direct comparison of phase, and the equivalence of transformation is mainly related to the accuracy of frequency shift measurement, the new method is likely to lay a theoretical foundation for the application of Doppler direction finding method in higher frequency bands.

In this study, we apply causal discovery to analyse causal links among key processes that contribute to Arctic-midlatitude teleconnections. First, we calculate the causal dependencies from observations. We then evaluate climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) via a comparison of their causal graphs for the period of 1979-2019 with those derived from observations. Based on observations, we show that the increase (decline) of near-surface Arctic temperature is associated not only with the reduction (increase) of sea ice over the Barents and Kara seas, but also with the strengthening (weakening) of atmospheric blocking over central Asia. We show that the near-surface westerly winds are strongly associated with the phase of the North Atlantic Oscillation (NAO). Observations show that the phase of NAO is connected with the polar vortex (PV), which is affected by the strengthening of the poleward eddy heat flux at 100 hPa. The analysis of CMIP6 historical simulations is in good agreement with the observations but reveals a negative connection between near-surface Arctic temperature and sea ice over Barents and Kara seas, which was not found in observations during December-January-February 1979-2019. Moreover, climate models simulate a more robust link between Arctic temperature and Barents and Kara sea ice towards the end of the century. The analysis of future changes in the Arctic-midlatitude teleconnections during cold seasons 2059-2099 also reveals that the connection between the Aleutian Low and the poleward eddy heat flux is expected to become more robust than in the analysed past.

Dissolved Oxygen (DO) plays a key role in reactive processes and microbial dynamics in the critical zone. While the general view is that oxygen is rapidly depleted in soils and that deeper compartments are anoxic, recent observations showed that fractures can provide rapid pathways for deep oxygen penetration, triggering unexpected biogeochemical processes. As it is transported in the subsurface, DO reacts with electron donors, such as $Fe^{2+}$ coming from mineral dissolution, hence influencing rock-weathering. Yet, little is known about the factors controlling the spatial heterogeneity and distribution of oxygen with depth. Here we present analytical expressions describing the coupled evolution of DO and $Fe^{2+}$ as a function of fluid travel time in crystalline rocks. Our model, validated with reactive transport simulations, predicts a linear decay of DO with time, followed by a rapid non-linear increase of $Fe^{2+}$ concentrations up to an equilibrium state. Relative effects of the reducing capacity of the bedrock and of transport velocity are quantified through a Damkohler number, capturing key hydrological and geological controls of $Fe^{2+}$ and DO distributions in the subsurface. This framework is used to investigate contrasted DO and $Fe^{2+}$ concentrations observed in two crystalline catchments. These differences are explained by the Damkohler number: one system is reaction-limited while the second is transport-limited. We show that hydrological and geological drivers can be discriminated by analyzing both O$_2$ and $Fe^{2+}$. These findings provide a new conceptual framework to understand and predict the evolution of DO in the subsurface, a key element in the critical zone.

Valles Caldera was formed by large rhyolitic eruptions at ~1.6 and 1.23 Ma and it hosts post-caldera rhyolitic deposits as young as ~70 ka, but the contemporary state of the magmatic system is unclear. Local seismicity beneath Valles Caldera is rare and shear-velocity (Vs) structure has not been previously imaged. Here, we present the first local Vs tomography beneath Valles Caldera using ambient noise Rayleigh dispersion from a ~71 km transect of nodal seismographs with mean spacing of ~750 m. An ~6 km wide low-Vs anomaly (Vs<2.1 km/s) is located at ~3-10 km depth within the 1.23 Ma caldera’s ring fracture. Assuming magma in textural equilibrium, the new tomography suggests that melt fractions up to ~17-22% may be present within the upper crustal depth range where previously erupted rhyolites were stored.

Planetary wind streaks are common aeolian features that have been studied primarily on Mars, Venus and Earth for several decades. They appear in imagery as distinctive albedo patterns on planetary surfaces. Most studies used remote sensing observations as the key means of investigation and lacked field validation. Although wind streaks are known on Earth, they have barley been studied in the field, with merely six published field investigations in the last forty years that were identified. This study presents an in-depth field study at eight sites in the Mojave and Atacama deserts with wind streaks conducted during three campaigns. The purpose was to investigate the spatial variability of surface properties responsible for the wind streak visibility in remotely sensed imagery in a way that will help better understand streaks on other planets. Data obtained from the surface includes field and satellite spectroscopy, and sampling for x-ray diffraction and particle size distribution analyses. The results show that for each wind streak, variations in the same surface settings lead to different appearances, even if the mineralogical and lithological settings of the sites are similar. Generally, wind streaks on Earth are composed of fine to medium sand particles, comparable to grain sizes observed in dark Martian wind streaks. The lack of finer fractions indicates on an active erosional environment. This supports previous studies suggesting that Earth wind streaks are likely to be presently active and are aligned in accordance to the modern prevailing winds.

Mars 2020 Mars Environmental Dynamics Analyzer (MEDA) instrument data acquired during half of a martian year (Ls 13º-180º), and modeling efforts with the Mars Regional Atmospheric Modeling System (MRAMS) and Mars Climate Database (MCD) allow us to study the seasonal evolution and variability of nocturnal atmospheric turbulence at Jezero crater. Nighttime conditions in Mars’s Planetary Boundary Layer are highly stable because of strong radiative cooling that efficiently inhibits convection. However, MEDA nighttime observations of simultaneous, rapid fluctuations in horizontal wind speed and air temperatures suggest the development of nighttime turbulence in Jezero crater. Mesoscale modeling with MRAMS also shows a similar pattern and enables us to investigate the origins of this turbulence and the mechanisms at play. As opposed to Gale crater, less evidence of turbulence from breaking mountain/gravity wave activity was found in Jezero during the period studied with MRAMS. On the contrary, the model suggests that nighttime turbulence at Jezero crater is explained by mechanical turbulence produced by increasingly strong wind shear related to the development of a bore-like disturbance at the nocturnal inversion interface. The enhanced wind shear leads to a reduction in the Ri and an onset of mechanical turbulence. Once the critical Richardson Number is reached (Ri ∼< 0.25), shear instabilities can mix warmer air aloft down to the surface.

We examined soft X-ray emission by the solar wind charge-exchange process around the Earth’s magnetosphere using a global magnetohydrodynamic simulation model. The dayside magnetopause reconnection heats and accelerates the plasma whereby the X-ray emission becomes as bright as $\sim 6 \times 10^{-6} {\rm\ eV}\ {\rm cm}^{-3}\ {\rm s}^{-1}$ under the southward interplanetary magnetic field conditions. In particular, under low plasma-$\beta$ solar wind conditions, we found that the X-ray intensity reflects the bulk motion of outflows from the reconnection region. We propose that this particular solar wind condition would allow visualization of the mesoscale magnetopause reconnection site, as observed in the solar corona.

The risk of floods has increased in South Asia due to high vulnerability and exposure. The August 2022 Pakistan flood shows a glimpse of the enormity and devastation that can further rise under the warming climate. The deluge caused by the Pakistan floods in 2022, which badly hit the country’s southern provinces, is incomparable to any recent events in terms of the vast spatial and temporal scale. The 2022 Pakistan flood ranked third in human mortality, while this was the top event that displaced about 32 million people. Using observations and climate projections, we examine the causes and implications of the August 2022 flood in Pakistan. Multiday (~ 15 days) extreme precipitation on wet antecedent soil moisture conditions was the primary driver of the flood in August 2022. The extreme precipitation in August was caused by two atmospheric rivers that passed over southern Pakistan. Streamflow simulations from the multiple hydrological models show that extreme precipitation was the primary driver of floods as several stations in the flood-affected regions experienced anomalously higher flow than the stations located upstream. The frequency of similar multi-day extreme precipitation events is projected to rise four-fold under the high emission scenario. The 2022 Pakistan flood highlights the adaptation challenges that South Asia is facing along with the substantial need for climate mitigation to reduce the risk of such events in the future.

Extremely halophilic archaea are microbes that thrive under very high salinities (>20% NaCl) and are almost exclusively placed in the class Halobacteria. In addition to their characteristic preference for high salinity and moderately high temperatures, many species of this class are resistant to desiccation, vacuum, and radiation, making them interesting targets for Astrobiological studies as model organisms and particularly relevant for the study of Mars, as highlighted by several authors. This class has a wide environmental range and includes species that live in salty biotopes such as salterns, salted foods, subterranean halite, lakes, or even in deep-sea brines in a list that includes several analogue sites. One current bottleneck of research with this group is the dispersed nature of data associated with its species. Our study partly addresses this by compiling phenotypic information and records of astrobiological experiments for all Halobacteria. We have established a database (HAPIE- Halophilic Archaea Phenotypic Information Explorer) that allows us to quickly compare different species as well as analyse trends and identify knowledge gaps and research opportunities. Our study identified gaps in coverage and knowledge (both at the level of taxonomy and range of tested parameters) and assisted us in defining new testing priorities.

Martian atmospheric dust is a major driver of weather, with feedbacks between atmospheric dust distribution, circulation changes from radiative heating and cooling driven by this dust, and winds that mobilize surface dust and distribute it in the atmosphere. Wind-driven mobilization of surface dust is a poorly understood process due to significant uncertainty about minimum wind stress, and whether saltation of sand particles is required. This study utilizes video of six Ingenuity helicopter flights to measure dust lifting during helicopter ascents, traverses, and descents. Dust mobilization persisted on take-off until the helicopter exceeded 3 m altitude, with dust advecting at 4-6 m/s. During landing, dust mobilization initiated at 2.3-3.6 m altitude. Extensive dust mobilization occurred during traverses at 5.1-5.7 m altitude. Dust mobilization threshold friction velocity of rotor-induced winds during landing are modelled at 0.4-0.6 m/s (factor of two uncertainty in this estimate), with higher winds required when the helicopter was over undisturbed terrain. Modeling dust mobilization from >5 m cruising altitude indicates mobilization by 0.3 m/s winds, suggesting non-saltation mechanisms like mobilization and destruction of dust aggregates. No dependence on background winds was seen for the initiation of dust lifting, but one case of takeoff in 7 m/s winds created a track of darkened terrain downwind of the helicopter, which may have been a saltation cluster. When the helicopter was cruising at 5-6 m altitude, recirculation was seen in the dust clouds.

High-resolution passive seismic imaging of shallow subsurface structures is often challenged by the scarcity of coherent body-wave energy in ambient noise recorded at surface stations. We show that autocorreleation (AC) of teleseismic P-wave coda extracted from just 1-month of continuous recording at 5 Hz geophones can overcome this limitation. We apply this method to investigate the longitudinal subsurface structure of Unaweep Canyon, a paleovalley in western Colorado (US) with complex evolution. Both fluvial and glacial processes have been proposed to explain the canyon’s genesis and morphology. The teleseismic P-wave coda AC retrieves zero-offset reflections from the shallow (200 – 500 m depth) basement interface at 120 stations along a 5 km long profile. Additionally, we invert interferometrically retrieved surface wave dispersion for the shear-wave structure of the sedimentary fill. Combined interpretation of these results and other geophysical and well data suggests an overdeepened basement geometry due to glacial processes.

Some observations of repeating earthquakes show an unusual, non self-similar scaling between seismic moment and corner frequency, a source property related to rupture size. These observations have been mostly reported in regions at the transition from stable to unstable slip, in geothermal reservoirs and subduction zones. What controls the non self-similarity of these ruptures and how this is linked to the frictional stability of the interface are still open questions. Here we develop seismic cycle simulations of a single unstable slipping patch to investigate the mechanics underlying this behavior. We show that temporal changes of normal stress on a fault can produce ruptures that exhibit the observed anomalous scaling. Our results highlight the role of fault zone fluid pressure in modulating the effective normal stress and contributing to the sliding stability of the fault.