A set of MHD equations is developed for multiple ion species in the limit of small Larmor radius. The derivation proceeds to explicitly calculate the Lorentz force resulting from the small ion drift velocities. The net effect is that in this limit all the ions move perpendicular to the magnetic field with the same E×B speed, but are free-streaming relative to one another in the parallel direction. The ions couple one to another in the parallel direction from changes in the magnetic field direction, leading to a collision-like term that, however, maintains a constant total kinetic energy. The equations governing parallel (centrifugal) acceleration, which may be an important process for ionospheric outflow, are then derived. The dispersion relation for a two-species, isotropic fluid with arbitrary mass and charge fractions, as well as electron pressure, is derived and the resulting wave modes are analyzed. A planar Alfvén mode separates from other, generally compressible, modes. It becomes unstable when the ram pressure of the streaming exceeds the firehose limit. The remaining modes satisfy a sixth order equation in the phase speed when counterstreaming and electron pressure are allowed. Without counterstreaming, three stable modes always exist, with two counter-propagating waves each, regardless of the presence of electron pressure. For the streaming case there are three modes, with two asymmetrically propagating waves each, whose behavior can be quite complicated, especially near the firehose instability limit. An example global magnetosphere simulation of a geomagnetic storm is presented using the derived multifluid formalism.

Proxy-based reconstructions of the Last Interglacial peak indicate changes in precipitation characteristics in the Levant. These reconstructions suggest that precipitation occurred in brief and intense events, particularly in the region’s southern parts. Some studies have offered conflicting paradigms for explaining hydroclimate variability. However, these have yet to be consistently tested in a modeling framework. Indeed, the modeling approach can undoubtedly enhance the combined interpretation of proxy records and our understanding of hydroclimate processes in the past. We used simulations from the Paleoclimate Model Intercomparison Project 4th phase (PMIP4) to evaluate and reconstruct the precipitation characteristics of the Levant. First, we identified the Alfred Wagner Institute Earth System Model to largely resemble proxy reconstructions. Then we used it to understand the variability of hydroclimate. We examined changes in the frequency, seasonality, and persistence of the Levant’s rain-bearing weather types, including Cyprus Lows and Red Sea Troughs. We further decomposed the dynamic and thermodynamic contributions to changes in the water balance of precipitation minus evaporation, comparing the Last Interglacial peak with preindustrial time. Based on differences in daily mean precipitation, we provide evidence that the rain-bearing weather types yielded significantly more precipitation (≈ +20%) during the Last Interglacial peak. This increase is most evident in the southern Levant, with higher precipitation during Red Sea Trough days, resulting primarily from thermodynamic changes. Minor differences in these weather types’ characteristics were found. Our research provides insights into historical hydroclimate changes in the Levant, extending our perspective on future climate impacts driven by natural variability.

Magnetic holes have been studied for decades, but their three-dimensional structure has not been thoroughly investigated until now. We have identified solar wind magnetic holes observed simultaneously by the four Cluster spacecraft. By transforming the observations into a local coordinate system and identifying a principal axis, we fit the results to a three-dimensional Gaussian model to estimate their scales. We present four events that highlight the various aspects of this method, emphasizing the critical role of coordinate system selection in the analysis. The principal axis of the holes varied, and in three out of four cases, were not aligned with the magnetic field, instead forming angles between 50 and 80 degrees, suggesting that magnetic holes are not necessarily oriented along the magnetic field. Finally, our analysis reveals that the scale of the holes along one direction is significantly longer than along the other two, suggesting an elongated ellipsoid as a typical shape for their morphology.

Land surface models struggle to accurately and precisely predict evapotranspiration (ET) and streamflow. We hypothesize this is partially due to poor representation of the spatial variability of relevant land surface model parameters. For example, land surface models parameterize the slope of the Medlyn stomatal conductance equation (g1) by plant functional type (PFT), but g1 varies widely within PFTs. We developed a parameterization scheme based on trait-environment relationships that predicts grid cell-specific g1 within the Catchment-CN4.5 land surface model as a function of local mean precipitation and canopy height. Although the functional form of this relationship was prescribed, its parameters were updated within Catchment-CN4.5 using particle swarm optimization constrained by observed ET and streamflow. We compared this model to a version of Catchment-CN4.5 that optimized PFT-based g1 values under the same optimization function and to one that used default parameters. We found that trait-environment-based g1 had significant within-PFT variability in forests. Furthermore, the trait-environment-based Catchment-CN4.5 outperformed the default Catchment-CN4.5 for mean absolute error by 11.8% for ET and 20.1% for streamflow. It also outperformed the PFT-based optimization of Catchment-CN4.5 for streamflow, decreasing mean absolute error by as much as 80% in some basins and by 5.4% across all basins. The PFT-based optimization, however, performed better for ET predictions by 1.2%. When extrapolating beyond where the trait-environment relationship was fit, the trait-environment-based model outperformed the default model by 7.8% and was outperformed by the PFT-based optimization by 2.8%. Our work demonstrates that trait-environment-based parameterization can improve land surface model performance.

A document by Willington Renteria. Click on the document to view its contents.

Volatiles are critical for understanding their delivery to the Moon and as a resource for sustained lunar exploration. Water ice and potentially other volatiles exist in and proximal to permanently shadowed regions (PSRs). However, little is known of the form, distribution, abundance, and stratigraphy of ice within the regolith. Lunar Trailblazer and the Volatiles Investigating Polar Exploration Rover (VIPER) aim to fill these knowledge gaps with observations at different scales. In this study, we replicated three different ice stratigraphies in a cryogenic, vacuum environment akin to that of PSRs, and measured the UV-Vis-NIR reflectance spectra before and after laser weathering the sample. Our findings reveal that near surface stratigraphy and weathering phenomena greatly affect detectability. Hence, results from our combined spectra and constructed regolith ice stratigraphy lays the groundwork for interpreting Lunar Trailblazer and VIPER results.

A document by Justin Kuropas. Click on the document to view its contents.

Space-weather forecasting requires advanced prediction of the arrival time and properties of coronal mass ejections (CMEs) in near-Earth space. Kinematic properties of CMEs close to the Sun – such as speed, direction and angular width – are routinely estimated from coronagraph images by using three-dimensional geometric models, such as the ‘cone model’. These are used to characterise a time-dependent perturbation at the inner boundary of a numerical solar-wind model, enabling a forecast of the CME arrival time and speed at Earth. The inner-boundary CME perturbation is typically spheroidal in shape. In this study we show that spheroidal CMEs exhibit four features inconsistent with observations that may limit the accuracy of space-weather forecasts: 1, Slower spheroidal CMEs intersect the model inner boundary for a longer duration and hence resist acceleration by the ambient solar wind. Thus slow spheroidal CMEs produce longer transit times than observed; 2, The radial extent of a spheroidal CME is directly related to its angular width. Observations of CMEs at 1 AU do not display any relation between angular width and radial extent; 3, Fast-and-wide CMEs cannot be sufficiently decelerated by the ambient solar wind and arrive with higher speeds than observed; 4, Spheroidal CMEs show different interplanetary accelerations for different angular widths, contrary to observations. We show that fixing the CME duration at the inner boundary – which mimics observed CME expansion – alleviates these problems. The choice of fixed duration is a free parameter that needs to be calibrated against observations, but 8 hours works reasonably well.

Understanding the impacts of high-resolution ocean model provides valuable insights for future research. However, the outcomes of sea surface state changes in both the tropics and mid-latitudes remain unclear, and initialized seasonal forecasts have not been studied extensively. This study investigates the impact of ocean model resolution with the first long-term hindcast experiment of an eddy-resolving (0.1°) ocean model used for global seasonal forecasting. We show that using the high-resolution ocean model significantly changes boreal winter jet streams in the atmosphere, based on the comparison of 30-year hindcasts with ocean resolutions ranging from 1° to 0.1° for the Japan Meteorological Agency/Meteorological Research Institute Coupled Prediction System version 3. In boreal winters, the cold sea surface bias in the equatorial Pacific is significantly reduced, leading to an equatorward shift in the intertropical convergence zone and enhanced convective activity in the western equatorial Pacific. The subtropical jet shifts southward due to the intertropical convergence zone shift and the weakening of equatorward propagation of mid-latitude atmospheric eddies. The enhanced convective activity in the tropics has a remote influence in the mid-latitudes, significantly reducing the upward eddy propagation of zonal wavenumber 1. Sea surface warm-up in the mid-latitudes partially cancels the reduction impact by enhancing the zonal wavenumber 2. Overall, the polar night jet accelerates due to the reduced supply of eddy forcing.

• Wildfire smoke alters local atmospheric conditions by causing surface cooling, midtropospheric warming, and reducing PBL height and wind speed • Smoke aerosols reduce shortwave radiation, stabilizing the atmosphere and limiting vertical mixing, which enhances localized weather impacts • Fires primarily influence local weather rather than regional circulations, emphasizing the need for improved smoke representation in weather models

Site-level uncertainty quantification is essential for Earth system modeling before scaling up to regional simulations. This study introduces a novel computational framework designed to enhance model predictability by reducing parametric uncertainty and assessing site and observable heterogeneity using various observational constraints. The framework integrates five components: Model Simulation, Statistical Emulation, Global Sensitivity Analysis (GSA), Model Calibration, and Model Prediction. Using the Energy Exascale Earth System Model (E3SM) land model (ELM), we simulated site-level land-atmosphere carbon and energy fluxes from 2003 to 2007 across five evergreen needleleaf FLUXNET sites, perturbing 26 vegetation-related model parameters. Gaussian Process emulators were employed to expedite GSA and model calibrations. Four critical parameters were identified by GSA that strongly influence selected land-atmosphere fluxes. Bayesian approaches were used to infer parameter probability distributions leveraging synthetic data and FLUXNET observations. The results reveal that posterior parameter distributions vary significantly across different sites and observables within the same Plant Functional Type. Probabilistic predictions indicate that parameters calibrated at one site can enhance predictive accuracy at other sites, although site heterogeneity may sometimes outweigh parametric uncertainty. Additionally, the probabilistic predictions demonstrate that calibration for one variable can also improve predictability for other variables, maximizing predictive capabilities with limited observation. This framework provides a powerful approach for reducing parametric uncertainty in Earth system models while deepening our understanding of carbon dynamics and energy cycles. Its adaptability makes it a valuable tool for broader applications in Earth system modeling.

In Northwestern South America (NWSA) kinematic data point to a consistent northeastward displacement of blocks, while the geological record shows a predominant shortening in NW-SE direction suggesting a clear pattern of strain partitioning. This type of deformation has been extensively studied in the context of two convergent plates, but not in the context of multiple tectonic elements, such as in our study area, where NWSA interacts with the Caribbean and Farallon/Nazca plates and the Panama-Choco Arc. We integrate the plate convergence evolution with evidence in the geological record to propose a tectonic reconstruction that accounts for the deformation distribution during the Cenozoic. Our results indicate that deformation was neither spatially homogeneous nor did it occur continuously. The main drivers of the distribution of deformation were variations of convergence obliquity, heterogeneous lithospheric strength, geometry of the subducting slabs and the transition from subduction to collisional tectonics of the Panama-Choco Arc against NWSA. Our block motion model reproduces a strain evolution that is consistent with the different episodes of deformation reported in literature. Our reconstructed velocity and strain vectors agree well with recent kinematics observed by space-based geodesy. Furthermore, the integration of our reconstruction with existing paleoenvironmental interpretations, allowed us to construct restored paleogeographic maps that agree well with the deformation and exhumation history of the Northern Andes.

Seismic diffraction imaging along the north-south oriented TRANSALP seismic line across the Eastern Alps reveals hitherto unresolved seismic stratigraphy in the eastern (German) Molasse Basin as well as details of fault and fracture networks along the front of the Alpine orogenic wedge. The method derives its theoretical foundation from the field of optics and utilizes the diffracted seismic wavefield, which is orders of magnitude weaker than seismic reflections but provides superior illumination of the traversed medium. Contrary to the common notion that diffraction imaging is only feasible in modern, more regular acquisition geometries such as in marine seismic data, our results show that it can also be applied successfully to less favorable datasets along TRANSALP. South of the Molasse Basin, diffractivity allows us to better distinguish the S-dipping foliation and bounding thrusts of the folded Subalpine Molasse, the Helvetic and Penninic Nappes and the Northern Calcereous Alps.

Yuhao Dai1,2†, Rebecca Pickering1, †, Lucie Cassarino1,3, Seunghee Han4, and Daniel Conley11Department of Geology, Lund University, Lund, Sweden2Research School of Earth Sciences, Australian National University, ACT, Australia3LEMAR laboratory, Institut Universitaire de la Mer, Université de Bretagne Occidental, Plouzané, 29280, France4School of Environmental Science and Technology, Gwangju Institute of Science and Technology, Gwangju, South KoreaCorresponding authors: Yuhao Dai (yuhao.dai@anu.edu.au), Rebecca Pickering (rebecca.pickering@geo.su.se)†These authors contributed equally to this work.Key Points:New downcore measurements show substantial negative apparent silicon isotope fractionation between authigenic clay and pore fluidsSilicon isotope fractionation between authigenic clays and pore fluids appears to depend on supplies of lithogenic materialsAbstractFormation of authigenic clays at sediment-seawater interface and their subsequent burial has recently been recognized as a key process removing silicon from the ocean. However, the effect of authigenic clay formation on isotopic mass balance of silicon in the ocean has been debated. Here, we constrain the apparent silicon isotope (δ30Si) fractionation associated with authigenic clay formation by measuring δ30Si signatures of co-existing pore fluids and reactive authigenic clays in a South Atlantic sediment core. The δ30Si gradients between reactive authigenic clays and pore fluids vary between -2.9 and -0.4‰, supporting a substantial negative δ30Si fractionation associated authigenic clay formation. The variable apparent δ30Si fractionation may be attributable to kinetic effects dependent on availability of lithogenic materials. Overall, our data show that formation and burial of authigenic clay likely preferentially remove isotopically light silicon from the ocean, with important implications on the isotopic mass balance of the marine silica cycle.

The deployment of photovoltaic (PV) systems in northern climates faces signifi cantchallenges due to snow accumulation, which reduces operational effi ciency. Withclimate change causing extreme weather conditions to occur more frequently(IPCC, 2021), this challenge is exacerbated. Our study focuses on single-axistrackers (SATs) and bifacial panels, introducing a pioneering snow measurementsystem that integrates laser-based sensors and digital image capture on movingpanels. The objective is to enhance snow shedding capabilities and optimize wintereffi ciency through advanced tracker control systems.Our methodologyencompasses power generation metrics, plane-of-array solar irradiation,meteorological data, and ultrasonic snow depth measurements, supplemented byvisual observations for empirical classifi cation of panel conditions. Experimentsinvestigate extreme and horizontal tilting, considering wind-induced shedding todetermine optimal snow shedding angles. Baseline data from March 2023 informexperiments planned for the 2024 winter season.The signifi cance of SATs isunderscored by their dominance in the US utility-scale PV market, accounting for94% of new installations in 2022. Bifacial panels, leveraging the high albedo ofsnow-covered ground, enhance performance in snowy environments. The IPCC AR6emphasizes the urgent need to transition away from fossil fuels. Integrating solarenergy, particularly in the global north where snowfall is common, is crucial. Ourproject aims to increase the effi ciency of solar plants during winter months,enhancing system resilience and robustness against extreme weather.Thedevelopment of an advanced snow mitigation algorithm shows considerablepromise. Preliminary experimentation indicates its effectiveness, suggesting it canbe easily adopted by the industry without major modifi cations. This algorithm hasthe potential to establish a new standard for snow management in PV systems. Byleveraging controlled tilting and innovative snow measurement techniques, ourresearch aims to signifi cantly improve the effi ciency and reliability of PV systems inwinter conditions. This will facilitate broader adoption and optimization of solarAbstract content goes here energy in northern climates, addressing a key barrier to year-round renewableenergy generation.

We present a statistical study of large magnetic field vector residuals between Swarm observations and the 13th generation International Geomagnetic Reference Field (IGRF-13) model under quiet to weakly disturbed geomagnetic conditions. Since the vast majority of data are taken during relatively quiet geomagnetic conditions, statistics of these large residuals are important for estimating potential errors for satellite operation when using IGRF-13 as reference, as well as for magnetosphere-ionosphere-thermosphere (MIT) studies. Residuals with magnitude of vector differences between Swarm observations and IGRF-13 estimations larger than 300 nT under Dst >-50 nT are studied from 2014 to 2020. All large residuals appear in the high-latitude auroral zone region peaking around 70° (-70°) magnetic latitude (MLAT) in the northern hemisphere (southern hemisphere) but there is also a secondary occurrence peak just below 80° (-80°) MLAT. However, the two hemispheres show clear asymmetries in the magnetic longitude (MLON) distribution where both hemispheres show high concentration of large residuals around the geographic poles. Since the two geographic poles are located at different geomagnetic locations and polar satellite’s orbits give rise to highly biased number of observations around the geographic poles, it results in high occurrence of large residuals around the geographic poles but a decrease in occurrence rate with respect to the total number of measurements. Identifying the interhemispheric asymmetries resulting from the asymmetry of the geographic poles with respect to the magnetic poles under relatively quiet geomagnetic conditions is helpful for a better understanding of interhemispheric asymmetry for the MIT system.

Seismic ambient noise has revolutionized regional crust and upper mantle imaging for broadband ocean-bottom seismometer (BBOBS) studies. However, the ocean poses unique challenges including tilt and compliance noise and presence of interface waves with considerable water-column sensitivity. Transfer function (TF) noise removal techniques enable separation of fundamental Scholte waves from overtone Rayleigh waves. However, such noise removal strategies do not always provide the expected signal improvement. Here, we leverage data from recent U.S.-led BBOBS deployments to evaluate variability in ambient-noise surface-wave quality and efficacy of TF corrections across different oceanic environments and instrumentation. We examine the 15-30 s and 3-10 s period bands to represent typical ranges for lithospheric imaging. We find that water depth, instrument design, sediment thickness, and ocean basin are the most important factors controlling ambient-noise data quality and effectiveness of TF corrections. At 3-10 s, enhancement of higher-mode Rayleigh waves is most successful in deep water with thin sediments. At 15-30 s, signal is improved both in shallow water due to infragravity wave removal and in instances of high tilt noise. Our results provide new insights into the environmental conditions and instrument designs that shape ambient noise tomography performance, offering strategies for optimizing future BBOBS studies as well as novel seafloor-sensing technologies.

The volume-integrated pH of seawater can be determined from the frequency and depth dependence of wind-generated ambient noise in the ocean. Over the 1 − 10 kHz frequency band, three main processes contribute to the acoustic attenuation in seawater: the chemical relaxation of boric acid and magnesium carbonate (< 3 kHz, related to pH), and magnesium sulfate (> 3 kHz, unrelated to pH). When local winds are strong (> 10 m/s), the ambient noise is dominated by locally generated surface noise, which exhibits a depth-independent directionality, and weak frequency and depth-dependent intensity. By measuring the depth-dependence of the spectral slope, the pH may be estimated from a comparison of the experimental data with an analytical model of ambient noise. Measurements of the depth-dependent ambient noise field were carried out in the Philippine Sea, Mariana Trench, and Tonga Trench from 2009 to 2021. The wideband (5 Hz - 30 kHz) acoustic data were recorded with untethered, free-falling, autonomous instrument platforms known as Deep Sound, equipped with two or four hydrophones. In all the data collected, the power spectral slopes became steeper with depth due to the stronger attenuation of high frequencies compared to low frequencies. Depth-averaged pH values, ranging from 7.68 to 8.35, were obtained from eight instrument drops. The noise spectral method, which has the potential for determining the depth-averaged value of pH, with the averaging depth being adjustable, could be suitable for the long-term passive acoustic monitoring of ocean acidity.