• GISS-E2.1 accurately simulates variations of precipitation 𝛿 18 O and d-excess but slightly underestimates d-excess values at low latitudes. • GISS-E2.1 overestimates 17 O-excess in polar regions, possibly due to inaccuracy in representing the supersaturation effect. • In tropical regions, the spatiotemporal distributions of d-excess and 17 O-excess are sensitive to rain evaporation.

A document by Heather L Wander. Click on the document to view its contents.

Mineral precipitation in geological formations occurs when reactive fluids of varying compositions mix, altering the porous microstructure of the rock. Basalt rocks are of particular interest for long-term CO2 storage due to their potential to rapidly mineralize CO2 into stable carbonate minerals. We investigated reactive fluid mixing and subsequent carbonate mineralization in porous basalt using time-lapse three-dimensional neutron and X-ray imaging. Two flow-through experiments with different injection rates were performed on basalt cores, where co-injected CaCl2 and Na2CO3 solutions were mixed within the porous network, leading to calcium carbonate precipitation. Time-lapse neutron imaging distinguished the two injected fluids and tracked their mixing. X-ray imaging was used to separate the solid matrix from the pore space to enable fluid analysis in the neutron images. A first experiment with a high flow rate induced a steady transverse mixing pattern, captured by a decay of the concentration variance through the sample, as measured by neutron imaging. A second experiment at a lower flow rate promoted more temporal fluctuations in the fluid distribution due to the multiphase flow of water and air in the rock. The analysis of neutron images showed a significant mixing of reactive fluids driven by these temporal fluctuations. Furthermore, a higher-resolution, synchrotron X-ray image of one of the sample rocks acquired after the experiment showed the formation of additional calcite resulting from long-term diffusive mixing. The results highlight the great potential and challenges of neutron and X-ray imaging in characterizing pore-scale mixing and precipitation in rocks.

High latitudes are predicted to continue warming at higher rates than the global average, with major implications for northern basins where concomitant deglaciation, permafrost thaw and vegetation shifts are expected. The Mackenzie River Basin, a globally significant basin, drains headwaters in the glaciated Canadian Rockies to the Arctic Ocean and is mostly underlain by permafrost. Here, we present scenarios of future change using the MESH distributed hydrological-cryospheric land surface model. MESH was forced with bias-corrected, downscaled RCM forcings and parameterized with a deep subsurface profile, organic soils, and glaciers. The model was validated against discharge, snowpack, and permafrost observations and used to simulate the hydrology and permafrost dynamics over the 21st century under the RCP8.5 climate change scenario with projected land cover change. The results show rapidly increasing rates of permafrost thaw; most of the basin will be permafrost-free by the 2080s. By late century, river discharges shift to earlier and higher peaks in response to projected increases in precipitation, temperature, snowmelt rates, despite increases in evapotranspiration from longer snow-free seasons. Baseflow discharges increase in winter, due to higher precipitation and increased basin connectivity from permafrost thaw resulting in enhanced groundwater flow. Subsurface moisture storage rises slightly but the liquid water fraction increases dramatically, increasing sub-surface runoff and river discharge. Canadian Rockies deglaciation reduces summer and annual discharge in the Athabasca and Peace headwaters. Downstream and northward of the mountain headwaters the direct impacts of climate change on river discharge dominate over those of changing land cover and glaciers.

This paper uses energy flux data from the DMSP F6 thru F19 satellites to construct a new equatorward auroral boundary model. This method of processing the data allows one to easily extend boundary detections to different instrument generations because it is based on a standard deviation value instead of hard thresholds. Using this method, the paper provides statistics from just under 1 million auroral boundaries between 1986 and 2014. These statistics are based on normal distribution fits for each Kp/Hp and MLT bin, which allows one to specify the boundary for an arbitrary distribution percentile. The paper compares how the model performs for driving by Hp30, Hp60, and Kp and finds that Hp30 is the best representation of the data. Finally, the paper provides specifications to recreate the model for the 50th and 95th percentiles for Kp and Hp30.

The Solar Wind Magnetosphere Ionosphere Link Explorer (SMILE) is a future spacecraft mission supported by the European Space Agency and the Chinese Academy of Science. It is expected that the mission will be launched in 2025 by ESA. SMILE will target the magnetopause, cusp, and bow shock regions. To investigate magnetosphere-ionosphere coupling, the spacecraft will take auroral images using an ultraviolet imager (UVI). For scientific support and analysis of data collected by the UVI, a numerical model of the ionosphere and UV emission has been developed, which is presented in the poster presentation. The photoelectron transport module of the model is described in the poster. The SMILE UV-imager will take global auroral images that for calibration, require specification of the changing state of the ionosphere. We demonstrate progress in meeting this goal and showcase using an example how the model works. 

Fine particulate matter (PM2.5), with a diameter of 2.5 micrometers or smaller, presents a significant health risk due to its ability to penetrate deeply into the lungs and enter the bloodstream. Conventional exposure assessments often overlook critical factors such as individual movement patterns and spatial variability in pollution, leading to less accurate exposure estimates and masking disparities in vulnerable populations. This study introduces an innovative spatial-temporal agent-based modeling (ABM) approach to capture detailed exposure dynamics within urban airsheds, using the Pleasant Run Airshed in Indianapolis, IN, as a case study. By integrating data from 23 PM2.5 sensors, meteorological variables, and land use data, we modeled PM2.5 concentrations over 50 weeks and simulated exposure for 10,000 virtual agents grouped by susceptibility, reflecting varying levels of health vulnerability. Our results reveal marked exposure disparities across sociodemographic groups, with high-susceptibility agents experiencing significantly greater health impacts. The spatial analysis identifies high-exposure zones near industrial areas and transportation corridors, underscoring the urgent need for targeted environmental justice interventions. This study demonstrates ABM’s potential to capture spatial-temporal exposure variability and illuminate inequities in pollutant exposure, offering critical insights for public health policy to reduce environmental health risks. Future research should explore combining ABM with multi-pollutant analysis to comprehensively address complex urban air quality challenges and promote equitable health outcomes.

The motion of the Adriatic microplate is thought to be highly sensitive to the surrounding subduction zones and the convergence of Africa and Eurasia. However, our understanding of the mantle dynamics in the Mediterranean region and its effect on plate motion remains incomplete. Here, we present a large set of 3D thermomechanical models of the entire Mediterranean region over the last 35 Myr to understand what controls the motion of the Adriatic microplate. The simulations take the convergence of the African and Arabian plates with the Eurasian plate into account, along with the dynamics of the subduction systems in the western (Apennines-Calabria), central (Dinarides-Hellenides) Mediterranean and in the Alpine-Carpathian region. Our results demonstrate that the subduction systems around Adria are highly coupled, which gives rise to complex asthenospheric flow in the central Mediterranean. We find that the plate motion of the Adriatic microplate over the last 35 Myr is controlled by interplay of three main factors: 1) the convergence between the African and Eurasian plates, 2) the retreat of the Alpine subduction zone to the north of Adria, and 3) the distance between the Calabrian and Hellenic subduction zones around Adria. Furthermore, in a system characterized by active convergence between Africa and Eurasia, the slab pull exerted by nearby subduction zones can only notably influence the motion of the Adriatic microplate if these subduction zones are located within a few hundred kilometers of Adria.

This work introduces a physically-based modeling framework to capture the spatio-temporal dynamics of dune vegetation under stochastic environmental disturbances. In analogy with other transitional disturbed environments, the model evaluates vegetation cover, within a cross-shore dimensionless framework, in response to random wind speed and runup. The wind speed is modeled as a compound Poisson process with Gamma-distributed properties, facilitating the computation of up-crossing times for various thresholds. The dune topography is represented by a swash zone with a Gaussian shape and a monotonic landward increase, parameterized by slope, wavelength, and height. Key disturbance conditions affecting vegetation---runup-induced flooding in the swash zone and wind-induced scour on the backshore and crest---are addressed through threshold-based analysis. The model uses a state-dependent dichotomic process for vegetation dynamics, where growth and decay are influenced by external forcing and vegetation state. Analytical solutions of the master equation for the vegetation distributions reveal the impact of stochastic factors on vegetation growth and stability. Sensitivity analysis identifies dune steepness, forcing magnitude and variability, and relative roughness as critical parameters. These factors significantly affect vegetation distribution, with increased steepness leading to higher vegetation density at the backshore and reduced density at the shorefront. Also, a Suitability Index to assess analytically dune stability based on disturbance and topographic features is introduced. Validation against satellite imagery and high-resolution real elevation data from the U.S. coastline confirms robustness and accuracy of the proposed approach. The results enhance understanding of dune vegetation dynamics and offer a framework for coastal restoration strategies.

The incapability of processing flow velocities under low tracer density conditions is one of the limitations of the traditional Large-Scale Particle Image Velocimetry (LSPIV). This study developed a new LSPIV algorithm, Time Frequency Analysis (TiFA), to overcome such a limitation, enhance computational efficiency, and improve the accuracy of derived velocities. TiFA investigates the temporal joint distribution pattern of two velocity components at each location. By assuming that the valid velocities follow a quasi-normal distribution in the velocity time series, TiFA can quickly and accurately separate the valid velocities from background noise and outliers. The performance of TiFA was evaluated by comparing with other algorithms including Traditional LSPIV, Ensemble Correlation (EC), Large-Scale Particle Tracking Velocimetry (LSPTV), and Seeding Density Index (SDI) in an experimental hydraulic model and two field cases. TiFA showed the highest overall accuracy and lowest computation cost in data analysis, especially under low tracer density conditions. In addition, TiFA showed its unique ability of automatically filtering out velocity data from low-quality zones such as no-tracer zones and surface glare zones. TiFA also showed its potential in processing turbulent flow. In summary, the newly-developed algorithm, TiFA, has demonstrated strong capability and competence in various flow and tracer scenarios, making it a valuable candidate for future applications.

Stream obstacles, naturally formed like boulders or engineered like weirs, are the major source of flow resistance; however, to quantify their flow resistance, a resistance formula needs to be selected in accordance with the specific obstacle type, i.e. obstacle type dependency. So far, whether a unified resistance formula that adequately characterizes the roughness of distinctive obstacle types is elusive. Here, we conduct flume experiments with various natural and engineered submerged obstacles, including boulders, weirs, log jams, and transverse stones. We combine them with existing datasets containing rigid vegetation, step-pool, and riffle-pool to identify a unified metric for a general resistance relation. We test three roughness metrics, the widely used roughness metrics D84 (84th percentile of bed grain size distribution), a bathymetric-line-based metric σz,centerline (the standard deviation of bed centerline elevation), and the new metric σz,bed (the standard deviation of elevation of the entire bed) as bed roughness, respectively. σz,bed is proposed to incorporate the roughness inhomogeneity in the transverse direction which widely exists in both natural and engineered channels, complementing the insufficiency of line-based metric σz,centerline. We show that the resistance equation based on σz,bed demonstrated a more consistent and superior velocity prediction capacity than D84 and σz,centerline throughout almost all types of obstacles. Interestingly, when applied to vegetated channels, the resistance formula based on only σz,bed can compare with those based on multiple parameters related to vegetation characteristics. This study shows the viability of unifying the flow resistance formula in open-channels with submerged obstacles, avoiding obstacle-type dependency.

Deposition on floodplains delays the downstream movement of particles transported by rivers, increasing the time required to improve water quality in downstream receiving waters following watershed restoration schemes designed to reduce upstream sediment loading. We present equations to assess whether floodplain storage is likely to influence the timing of sediment delivery, for estimating mean travel times, and for determining complete travel time distributions. We use a step reduction in upstream sediment supply to represent expected effects of best management practices, and present an analytical solution for the time needed to deliver restoration benefits downstream. Parameters required by these equations can be extracted from sediment budgets and estimates of the ages of floodplain deposits. Illustrative computations for the mid-Atlantic region predict that only 15% of the sediment load can be transported 200 km without being stored on a floodplain. Once deposited, particles remain in place for ~300 years, leading to average transport velocities of only ~100 m/yr. For distances of 20-75 km, average travel times range from ~500 to ~750 years. These results suggest that Best Management Practices employed in the headwaters of large watersheds will not benefit downstream estuaries within the decadal timescales typically considered by watershed managers. Precise predictions, however, will require accurately measuring floodplain deposition, erosion, and sediment chronologies throughout watersheds, data that are currently unavailable.

Fluid production from dehydration reactions and fluid migration in the subducting slab impact various subduction processes, including intraslab and megathrust earthquakes, episodic slip and tremor, mantle wedge metasomatism, and arc-magma genesis. Quantifying those processes requires a good knowledge of the location and amount of fluid outflux at the top of the slab. Previous models of fluid migration indicate that compaction-pressure gradients induced by the dehydration reactions could drive updip intraslab fluid flow (Wilson et al., 2014). However, how the initial hydration in the oceanic mantle prior to subduction impacts the updip fluid flow has not been investigated. Here, we use a 2-D two-phase flow model to investigate this effect under various initial slab-mantle hydration states and slab thermal conditions, both of which impact the depth extent of the stability of hydrous minerals. We focus on the lateral shift between the site of dehydration reactions and the location of fluid outflux at the top of the slab due to intraslab-updip migration. Our results indicate that major updip fluid pathways form along the antigorite and chlorite dehydration fronts sub-parallel to the slab surface. This, in turn, promotes slab-fluid outflux at the slab surface as shallow as 30–40 km depths. This mechanism is more likely in young slabs (< ~30 Ma), in which the thickness of the hydrated mantle in the incoming oceanic mantle that is required to form the slab-parallel dehydration fronts is relatively small (< ~20 km) because of its warm condition and thus a relatively thin antigorite stability zone.

We conduct a high-resolution seismic tomography for the crustal P and S-wave velocities of Yunnan region in southwestern China. Waveforms recorded at 128 broadband stations from 131 regional earthquakes of moment magnitudes 3.9−5.5 occurring between 2009 and 2021 are used to obtain traveltime residuals by the cross-correlation between records and synthetics. Using the regional community velocity model SWChinaCVM‐1.0 as the initial model, we carry out a three-stage iterative adjoint tomography, progressing from the longer period band of 50–20 s to shorter-period bands of 30–10 s and 30–5 s. The final model shows general consistency in the spatial patterns of P- and S-wave velocity anomalies. Widespread low-velocity anomalies with high-Vp/Vs ratios in the mid and lower crust in the region suggest a mix of weak materials of the mid-lower crustal flow from under the Tibetan Plateau with hot materials of the upwelling from the deep mantle plume that led to the Emeishan Large Igneous Province. Localized velocity and Vp/Vs ratio anomalies also reveal that the Lijiang-Xiaojinhe Fault Zone appears to be confined in the upper crust, while the Anninghe-Zemuhe Fault Zone and the Xiaojiang Fault Zone are both whole-crust structures reaching the Moho interface. The Red River Fault Zone, a whole-crust fault, separates the Yangtze Craton to the northeast from the Indo-China Block to the southwest. The main fault zones, the decoupling between the crustal and uppermost mantle parts, and the wide-spreading weak mid-lower crustal materials mutually interact, all contributing to the tectonic evolution of the entire region.

The Aurora vent field (82°53.83’ N, 6°15.32’ W) is located in the weakly stratified Arctic Ocean under perennial ice cover at the western edge of the ultraslow-spreading Gakkel Ridge, the slowest spreading mid-ocean ridge on Earth. Here, we report data on the dispersal of the proximal hydrothermal plume in this extreme environment. The hydrothermal plume is of unusual dimensions, with a small horizontal, but large vertical extent, which is caused by the hydrography of the Arctic Ocean. Water column parameters such as turbidity and redox potential show a highly variable but horizontally confined non-buoyant plume. Dissolved iron (dFe), manganese (dMn), δ3He, and methane (CH4) all show distinct enrichments in the hydrothermal plume relative to background deep-water, but relatively low peak concentrations due to the dilution over a vertical extent of over 500 m. Plume particle samples exhibit elevated Fe/Al ratios consistent with Fe-oxyhydroxide precipitation close to the vent, whereas particulate Mn/Al ratios do not reveal any complementary pMn enrichments in the proximal plume. Positive correlation between Fe/Al, and several other element/Al ratios (e.g. P, V, As) are consistent with scavenging of these elements onto Fe-hydroxide plume particles and removal into the underlying sediments. Surface sediment samples collected close to Aurora reveal highly elevated concentrations of hydrothermally-sourced elements in the immediate vicinity of the vent-site. For example, proximal surface sediments contained up to 8222 mg kg-1 Cu, whereas Cu concentrations in core tops a few kilometers away from the site were much lower (<50 mg kg-1).

Temperature proxies such as clumped isotope (Δ47) thermometry on biogenic carbonates are applied to the past with greatest confidence when the proxy-temperature relationship is shown to be robust within natural temperature conditions of the ocean. Especially well-suited for this purpose are biogenic carbonates sampled from well-constrained production period and oceanographic conditions of sediment traps. Since coccolithophorids have a cosmopolitan distribution and are major biogenic carbonate producers in the surface ocean, their coccoliths usually dominate the inorganic carbon flux in sediment traps and are sufficiently abundant in most traps for clumped isotope analysis. Here, we measured Δ47 in the coccolith size fraction of 18 sediment trap samples across a 75° latitudinal gradient and three ocean basins. To identify the upper ocean provenance region of the coccoliths in each trap, a simple model of coccolith transport by ocean currents was constructed. The coccolith Δ47 strongly follows the upper ocean temperatures, in particular the average temperatures from the maximum production depths of living coccolithophores from their provenance areas. There is no evidence for a coccolithophore species-specific effect on the Δ47-temperature relationship. Applying the recent coccolith-specific Δ47-temperature calibration (Clark et al., 2024a) to estimate calcification temperatures shows that inferred calcification depths match the depth of maximum coccolithophore production in the provenance area. Compared to other calibrations for biogenic carbonates, the coccolith-specific Δ47-temperature calibration yields the best agreement with the depth of maximum coccolithophore abundance and the expected depth of coccolith production.

Gratteri crater is a young Martian crater which still retains secondary craters, and some of them have unique ejecta deposits similar to mudflows splattered by impacts, suggesting that they might have been formed on wet sand-like material. Interestingly, the morphologies of Gratteri secondary craters vary among regions. We conducted crater formation experiments onto wet sand targets with different water contents and observed that the crater size and morphology changed with target water content. We established a crater size scaling law for wet sand which can account for water content change. Our scaling law suggests that the region 103 km away from the Gratteri crater might have had a higher water content than the region 32 km away (≥4.6 wt.% vs. <2.0 wt.%, respectively), judging from the sizes and morphologies of its secondary craters in each region.

Cloud optical property retrievals from passive satellite imagers tend to be most accurate during the daytime due to the availability of visible and near-infrared solar reflectances. Infrared (IR) channels have a relative lack of spectral sensitivity to optically thick clouds and are heavily influenced by cloud-top temperature making accurate retrievals of cloud optical depth, cloud effective radius, and cloud water path more difficult at night. In this work, we examine whether the use of spatial context—information about the local structure and organization of cloud features—can help overcome these limitations of IR channels and provide more accurate estimates of nighttime cloud optical properties. We trained several neural networks to emulate the Advanced Baseline Imager (ABI) NOAA Daytime Cloud Optical and Microphysical Properties (DCOMP) algorithm using only IR channels. We then compared the neural networks to the NOAA operational daytime and nighttime products, and the Nighttime Lunar Cloud Optical and Microphysical Properties (NLCOMP) algorithm, which utilizes the low-light visible band on VIIRS in collocated imagery. These comparisons show that the use of spatial context can significantly improve estimates of nighttime cloud optical properties. The primary model we trained, U-NetCOMP, can reasonably match DCOMP during the day and significantly reduces artifacts associated with day/night terminator. We also find that U-NetCOMP estimates align more closely with NLCOMP at night compared to the nighttime NOAA operational products for ABI.