It is well-established that positive feedbacks between permafrost degradation and the release of soil carbon into the atmosphere impacts land-atmosphere interactions, disrupts the global carbon cycle, and accelerates climate change. The widespread distribution of thawing permafrost is causing a cascade of geophysical and biochemical disturbances with global impact. Currently, few earth system models account for permafrost carbon feedback mechanisms. This research identifies, interprets, and explains the feedback sensitivities attributed to permafrost degradation and terrestrial carbon cycling imbalance with in situ and flux tower measurements, remote sensing observations, process-based modeling simulations, and deep learning architecture. We defined and formulated high-resolution polymodal datasets with multitemporal extents and hyperspatiospectral fidelity (i.e., 12.4 million parameters with 13.1 million in situ data points, 2.84 billion ground-controlled remotely sensed data points, and 36.58 million model-based simulation outputs to computationally reflect the state space of the earth system), simulated the non-linear feedback mechanisms attributed to permafrost degradation and carbon cycle perturbation across Alaska with a process-constrained deep learning architecture composed of cascading stacks of convolutionally layered memory-encoded recurrent neural networks (i.e., GeoCryoAI), and interpreted historical and future emulations of freeze-thaw dynamics and the permafrost carbon feedback with a suite of evaluation and performance metrics (e.g., cross-entropic loss, root-mean-square deviation, accuracy). This framework introduces ecological memory components and effectively learns subtle spatiotemporal covariate complexities in high-latitude ecosystems by emulating permafrost degradation and carbon flux dynamics across Alaska with high precision and minimal loss (RMSE: 1.007cm, 0.694nmolCH4m-2s-1, 0.213µmolCO2m-2s-1). This methodology and findings offer significant insight about the permafrost carbon feedback by informing scientists and the public on how climate change is accelerating, strategies to ameliorate the impact of permafrost degradation on the global carbon cycle, and to what extent these connections matter in space and time.

Previous workers have used stratigraphic studies to identify three potential marine gateways that connected the Atlantic and Mediterranean during the Messinian salinity crisis (MSC): the Strait of Gibraltar that remains a 300-900-m-deep channel to the present-day and the Betic and Rifian corridors now exposed on-land in southern Spain and northern Morocco, respectively. Comparison of deepsea cores from the Atlantic and Mediterranean have shown that there was no significant or sea-level rise during the Messinian leaving a tectonic or climate control as the most likely cause for Messinian drying of the Mediterranean and that was followed in the early Pliocene by the re-flooding of Atlantic waters in the dessicated and evaporite-filled Mediterranean basin. In this study, we integrate bathymetric, GPS data from the Tangier Peninsula and its offshore areas with paleostress measurements at 25 sites ranging in age from Jurassic to Miocene. Offshore data from the Strait of Gibraltar indicates that the main ENE-lineament on the seafloor is a major right-lateral strike-slip fault whose sense is consistent with: 1) WNW-trending GPS vectors; 2) the arrangement of positive restraining and negative releasing bends; 3) formation of a 15-20-km-wide syncline within the Strait that deepened with continued compression; and 5) the right-lateral offset of the Mesozoic Calcaire Dorsale Ridge by ~7 km. Paleostress sites on-land in rocks of Oligocene to early Pliocene age indicate three events: 1) east-west compression of Miocene age inferred to record the formation and eastward motion of the Gibraltar arc; 2) NW-SE compression inferred to record the closure of Nubia and Iberia with compression of the Gibraltar arc; and 3) NE-SW compression inferred to represent continued compression of the Gibraltar arc that accompanied continued formation of the large syncline within the strait. We postulate that the offset of the highly resistant and 1-km-thick Calcaire Dorsale allowed the initial deep channels to open between the Atlantic and Mediterranean. We see no evidence for north-south-striking normal faults as postulated in strait-opening models based on roll-back of the Gibraltar slab.

Ice shelves flex in response to surface ocean waves, which imposes stresses and strains on the shelves that promote iceberg calving. Previous modelling studies of ice shelf responses to ocean waves have focussed on highly idealised geometries with uniform ice thickness and flat seabeds. This study leverages on a recently developed mathematical model that incorporates spatially varying geometries, combined with measured ice shelf thickness and seabed profiles, to conduct a statistical assessment of how fifteen Antarctic ice shelves respond to ocean waves over a broad range of relevant wave periods, from swell to infragravity waves to very long period waves. The results show the most extreme responses at a given wave period are generated by features in the ice shelves and/or seabed geometries, depending on the wave regime. Relationships are determined between the median ice shelf response and the median shelf front thickness or the median cavity depth. The findings provide further evidence of the role of ocean waves in large-scale calving events for certain ice shelves (particularly the Wilkins), indicate a possible role of ocean waves in calving events for other shelves (Larsen C and Conger), and the relationships determined provide a method to assess how ice shelf responses are evolving with climate change and project future scenarios.

Ongoing efforts to characterize underwater dunes have led to a considerable number of freely available tools that identify these bedforms in a (semi-)automated way. However, these tools differ with regard to their research focus and appear to produce results that are far from unequivocal. We scrutinize this assumption by comparing the results of five recently published dune identification tools in a comprehensive meta-analysis. Specifically, we analyse dune populations identified in three bathymetries under diverse flow conditions and compare the resulting dune characteristics in a quantitative manner. Besides the impact of underlying definitions, it is shown that the main heterogeneity arises from the consideration of a secondary dune scale, which has a significant influence on statistical distributions. Based on the quantitative results, we discuss the individual strengths and limitations of each algorithm, with the aim of outlining adequate fields of application. Yet, the concerted bedform analysis and subsequent combination of results have another benefit: the creation of a benchmarking data set which is inherently less biased by individual focus and therefore a valuable instrument for future validations. Nevertheless, it is apparent that the available tools are still very specific and that end-users would profit by their merging into a universal and modular toolbox.

The Cameroon Volcanic Line (CVL) and other tectonic features in Cameroon remain enigmatic, prompting ongoing debates about their detailed structure, composition, and geodynamic evolution. To shed light on these complexities, we leverage the ambient noise tomography (ANT) method to invert shear wave velocity (Vs) and image subsurface structures, providing crucial insights into both subsurface geology and deep crustal processes. Specifically, we employed two different methods: Markov chain Monte Carlo (MCMC) and Evolutionary Algorithm (EA) inversions to robustly constrain the Vs velocity structure, Vp/Vs ratio, and density beneath the CVL and its surrounding area.Our results reveal a prominent high-velocity structure at depths of 25 to 35 km, which precisely aligns with the CVL. Within this region, Vs velocities reach up to 4.0 km/s, accompanied by a Vp/Vs ratio ranging between 1.85 and 1.88 and density varying from 2.9 to 3.1 g/cm3. These characteristics suggest the presence of cooled mafic material that has intruded the crust. Our 2D depth cross-sections along the CVL indicate that these cooled mafic intrusions are ubiquitous along the entire volcanic line. However, they are spatially separated from the upper crust's volcano-plutonic structure by a thin intermediate structure exhibiting a Vp/Vs ratio of 1.68 to 1.71 and an average Vs velocity of 3.8 km/s, indicative of felsic to intermediate crust, which may be linked to the Pan-African Orogeny.The high Vp/Vs ratio and Vs velocity structures are found closer to the surface in the recently active volcanic provinces, accompanied by a thinner low Vp/Vs structure. We posit that this thinned low Vp/Vs structure may have facilitated the ascent of mafic material, contributing to recent volcanic activity in the region. Conversely, beneath the Oubanguides belt and Congo craton, these low Vp/Vs structures appear thicker, with mafic intrusions present at depth > 35 km. This observation suggests a dynamic process involving the pushing and exhumation of lower crustal material by the mafic material.Our crustal imaging results hold significant implications for our understanding of the region's geodynamic evolution, suggesting an interaction with deeper structures, may be responsible for the crustal intrusions and volcanism observed along the CVL.

“Pressure and time.” A momentous quote in a compelling movie from a few decades ago interestingly pointed at some of the ingredients that contributed to shaping the Earth. The movie set off from how to seep through masses that appeared just too vast to be shakable or vulnerable – if not by deciphering their inner core. The planetary size and time frame of the Earth may have elicited a perception of a durable, unbuckling living environment – just because “pressure and time” to really affect it would have been out of human reach – supposedly. However, the Earth and environmental sciences have long striven to alert contemporary societies that this is just not the case, as humans have been well exerting scattered yet ubiquitous, planetary-scale pressure over a relatively brief time – with consequential, durable effects. Rising global population, long-term migration shifts of continental extents – due to risks, climate, resources – and unpredicted factors – from vulnerabilities to instabilities – pressure on the environment (natural and built) in unprecedented scale throughout human history. The Earth sciences were born out of deciphering ancient life forms teeming in an aboriginal environment, unfolding on a planet that could be explained only by looking at the Solar system – and at the inception of the Universe.Cross-disciplinary by nature, the Earth and environmental sciences offer crucial tools to gauge location, economic turnout, and societal costs of those very resources and fragilities. They also are pivotal co-actors of intellectual stewardship bridging the gulf with sister disciplines well beyond the remits of the physical sciences. From economics to philosophy, and from history to literature, multiple, diverse and concurring threats call for resourceful, multi-faceted mind- and skill-sets where no single hazard may be really treated apart – not on societal terms.Adapting a famous statement from the 20th century, evolution in a time of poly-crises, multiple hazards, and accrued vulnerabilities is not going to be a dinner party for contemporary societies – especially as they dwell a world perceived as increasingly richer in risks and poorer in resources, with a growing population and across instabilities. Human Earth sciences offer a bridge towards our collective future – as societies, continents, planets.Earth-prints @ INGV  

Mohamed Hamdy Eid a,b*,  Attila Kovácsa and Péter Szűcs aaInstitute of Environmental Management, Faculty of Earth Science, University of Miskolc, 3515, Hungary; [email protected]; [email protected]; [email protected]. bGeology Department, Faculty of Science, Beni-Suef University, Beni-Suef, 65211, Egypt* Corresponding author: Mohamed Hamdy Eid a,b*; [email protected] ORCID: 0000-0002-3383-1826Final Paper Number: H31U-1778  Presentation Type: Poster Session Number and Title: H31U: Frontiers in Water Quality I Poster Session Date and Time: Wednesday, December 13th; 8:30 AM - 12:50 PM PST Location: MC, Poster Hall A-C – South Abstract The current study evaluates the different factors threatening the sustainability of Siwa Oasis including soil salinization, water quality deterioration, water logging, depletion of non-rechargeable water resources and providing water management plan. GIS and remote sensing supported with machine learning were used for change detection in the land cover from 1990 to 2020. The hydrodynamic condition in the deep Nubian sandstone aquifer (NSSA) was investigated using pressure-depth pro le. The groundwater salinity was monitored from 1998 to 2022. Geochemical model using PHREEQC was conducted to detect the types of minerals that have the ability to precipitate in the soil from irrigation water and decrease its permeability. The change detection in the land cover showed rapid increase in the surface area of the salt lakes from 22.6 km2 in 1990 to 60.6 km2 in 2020. The soil salinization increased in the central Siwa Oasis due to evaporation of water logged in the soil. Monitoring the water salinity from 1998 to 2022 showed rapid deterioration in groundwater quality of the Tertiary carbonate aquifer (TCA). The pressure-depth pro le showed that the water in NSSA is over hydrostatic pressure in the eastern and western part of the study area and the central part is under hydrostatic pressure indicating pressure decrease. Chadha diagram and piper diagram showed that the water type changed upward from Ca-Mg-HCO3 in the rst stage in NSSA to Na-Cl type in the last stage in TCA and surface water. The saturation index revealed that the majority of water samples were supersaturated with respect to calcite, dolomite, talc, Ca-montmorillonite, chlorite, gibbsite, illite, K-mica, hematite, chrysotile and kaolinite, while the samples were undersaturated with halite, anhydrite, gypsum, and CO2. The irrigation water quality indices showed that NSSA is suitable for irrigation purposes while TCA is not suitable for irrigation regarding magnesium hazards (MH) and potential salinity (PS). The water quality regarding sodium adsorption ratio (SAR) and sodium percent (Na%) range from good to poor and good according to residual sodium carbonate (RSC). Application of subsurface drip irrigation, and mixing water of TCA and NSSA could be the best management of the water resources in Siwa Oasis. 

Here we present a dissemination method that combines science and art to visualize a seismic experiment conducted in northern Chile. Through the expertise of an illustrator using digital watercolor techniques and a science journalist who contributed her expertise in creating plain-language keynotes, we created six visually compelling art pieces to summarize the progress and results of the first year of a project funded by Fondecyt-ANID. The artwork, called “Images of Silence” (Imágenes del Silencio, originally in spanish), plays with the concepts of silence and images. Here, the quitness of the desert is often interrupted by the loudness of seismic activity. Additionally, the illustrations - images to tell a story - offers a narrative for a seismic experiment that aims to image the Earth's interior. This artwork creatively incorporates indigenous pictograms found in regional rock formations, making a meaningful connection between seismology and the region's rich cultural heritage. Finally, Images of the Silence is an transdisciplany work with scientifics, journalists and artists to develop an unconventional approach to better communicate our results and remind us that science and art always go together.

Anthropogenic activities such as fluid injection, fluid extraction, mining, and hydraulic fracturing can all cause induced seismicity which can in turn result in land subsidence. This latter phenomenon is devastating to local infrastructure as well as underlying aquifers. It is for this reason that monitoring and predicting land deformation is of utmost importance. We relied on Interferometric Synthetic Aperture Radar (InSAR) images captured by Sentinel-1 to monitor deformation in the line-of-sight of the satellite. The Geysers geothermal field, where injection plays a direct role in induced seismicity, was used as the area of study and a deformation time series was built using LiCSBAS [1]. Two machine learning models (model A and model B) that included Long Short-Term Memory (LSTM) and Convolutional Neural Network (CNN) layers were built to predict future deformation maps. The only difference between the models was the incorporation of geothermal injection and production data in model B. While both models outperformed a baseline linear model, it was model B that performed the best based on a mean squared error metric.

Mars experienced a dynamo process that generated a global magnetic field ~4.3–3.6 Ga. The cessation of this dynamo strongly impacted Mars’ history and is expected to be linked to thermochemical evolution of Mars’ iron-rich liquid core, which is strongly influenced by its thermal conductivity. Here we directly measured thermal conductivities of solid iron-sulfur alloys to pressures relevant to the Martian core and temperatures to 1023 K. Our results show that a Martian core with 16 wt% sulfur has a thermal conductivity of ~19 to 32 W m-1 K-1 from its top to the center, much higher than previously inferred from electrical resistivity measurements. Our modelled thermal conductivity profile throughout the Martian deep-mantle and core indicates a ~4 to 6-fold discontinuity across the core-mantle-boundary. The core’s efficient cooling resulting from the depth-dependent, high conductivity diminishes thermal convection and forms thermal stratification, significantly contributing to cessation of Martian dynamo.

• A physics-informed neural network trained without ground truths can provide accurate initial fields for numerical prediction. • The system's kinetic features are embedded into the model through our four-dimensional variational form loss function. • We show on Lorenz96 that the proposed method can be used directly for accurate data assimilation at a low computational cost.

Large amounts of gas hydrates exist on continental slopes, and pose a significant risk of triggering submarine landslides, subsequently impacting offshore infrastructures. While the infinite slope model is widely used for submarine slope stability analysis, it overlooks the potential for initial small failures to develop into large landslides. Our study integrates slip nucleation with excess pore pressure during gas hydrate dissociation, establishing a model for progressive slope failure triggered by hydrate dissociation. Focusing on the Shenhu hydrate site GMGS3-W19, our results show that even 1% gas hydrate dissociation contributing to about 1 MPa overpressure can induce progressive landslides. Notably, deeper failure surfaces with gentler slopes and collapsible sediments require higher pore pressures to induce progressive failure, reducing the risk of developing into catastrophic landslides. The results indicate that the infinite slope model may overestimate slope stability, and that submarine landslides caused by progressive failure may occur on slopes previously considered stable, such as the Ursa Basin in the northern Gulf of Mexico. This extension of the infinite slope model sheds light on potential limitations in current stability assessments, providing crucial insights for submarine landslide studies and offshore infrastructure development.

The exploration of multi-layer coupling mechanisms between earthquakes and the ionosphere is crucial for utilizing ionospheric precursors in earthquake prediction. A significant research task involves continuously tracking the spatio-temporal changes in ionospheric parameters, acquiring comprehensive seismic anomaly information, and capturing “deterministic” precursor anomalies. Building upon previous research on seismic ionospheric signal characteristics and data from the China Seismo-Electromagnetic Satellite (CSES), we have enhanced the Pattern Informatics(PI) Method and proposed an Improved Pattern Informatics(IPI) Method. The IPI method enables the calculation of the spatio-temporal dynamics of electronic density anomalies detected by the CSES satellite. Taking the 2021 Maduo Mw7.3 earthquake as a case study, we analyzed the seismic signals potentially contained in the electronic density anomaly disturbances. The results show that: 1) Compared to original electronic density images, the IPI method-derived models extracted distinct electronic density anomaly signals, regardless of the data collected whether during descending (daytime) or ascending (nighttime) orbits, or across different time scales of change window. 2) The electronic density anomalies appeared about 40 days prior to the Maduo Mw7.3 earthquake. The evolution of these anomalies followed a pattern of appearance, persistence, disappearance, re-emergence, and final disappearance. Moreover, the evolution trends of the IPI hotspot images calculated from descending and ascending orbit data were similar. These results suggest that the IPI method can capture the spatio-temporal trends of ionospheric parameters and effectively extract electronic precursors related to strong earthquakes.

The maximum information entropy production model (MaxEnt), the relative humidity at equilibrium approach (ETRHEQ), and the Surface Flux Equilibrium model (SFE) are the three effective parsimonious models to estimate evapotranspiration. No attempts have been made to investigate their congruence, distinctions, or potential complementarity. Our mathematical analysis demonstrates that minimizing the dissipation function of energy fluxes in MaxEnt is equivalent to minimizing the vertical variance of RH in ETRHEQ. The effectiveness of both MaxEnt and ETRHEQ lies in the fact that far-from-equilibrium ecosystems progress toward a steady state (the SFE state) by minimizing dissipation. This tendency is manifested through the vertical variance of RH. The connection between MaxEnt, ETRHEQ, and SFE is independent of Monin-Obukhov similarity theory (MOST)’s extremum solution, and MOST’s extreme solution can be viewed as equivalent to introducing a constant correction factor to account for atmospheric stability. While MaxEnt and ETRHEQ share a common physical foundation, they diverge in their approaches to modeling evapotranspiration, particularly in how they address the roles of vegetation and land surface heterogeneity. More importantly, the unified hydrometeorological framework suggests that turbulence fluxes within the atmospheric boundary layer adhere to the principles of maximum information entropy production. The way in which dissipation, along with its associated entropy production, is established using information entropy theory deviates from traditional thermodynamic entropy formulations. Delving into the precise computation of dissipation and entropy production for energy fluxes at different temporal and spatial scales presents an appealing avenue for prospective research.

Magnetic hysteresis measurements are routinely made in the Earth and planetary sciences to identify geologically meaningful  magnetic recorders, and to study variations in present and past environments. Interpreting magnetic hysteresis data in terms of domain state (particle size)  and paleomagnetic stability are major motivations behind undertaking these measurements, but the interpretations remain  fraught with challenges and ambiguities. To shed new light on these ambiguities, we have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room-temperature magnetite as a function of particle size (50-195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant); our models span uniformly magnetized single domain (SD) to non-uniformly magnetized single vortex (SV) states. Within our models the reduced magnetization  marks a clear boundary between SD (≥0.5) and SV (<0.5) magnetite. We further identify particle sizes and shapes with unexpectedly low coercivity and coercivity of remanence. These low coercivity regions correspond to magnetite particles that typically have multiple possible magnetic domain states, which has been previously linked to a zone of unstable magnetic recorders. Of all hysteresis parameters investigated, transient hysteresis is most sensitive to particles that exhibit such domain state multiplicity, leading us to suggest that transient behavior be more routinely measured during rock magnetic investigations.

The ability of rocks to hold a reliable record of the ancient geomagnetic field depends on the structure and stability of magnetic domain-states contained within the rock’s magnetic particles. In paleomagnetic studies, the Day plot is an easily constructed graph of magnetic hysteresis parameters that is frequently used (and mis-used) to estimate the likely magnetic recording stability of samples. Often samples plot in the region of the Day plot attributed to so-called pseudo-single-domain (PSD) particles with little under standing of the implications for domain-states or recording fidelity. Here we use micromagnetic models to explore the hysteresis parameters of magnetite particles with idealized prolate and oblate truncated-octahedral geometries containing single domain (SD), single-vortex (SV) and occasionally multi-vortex (MV) states. We show that these do main states exhibit a well-defined trend in the Day plot that extends from the SD region well into the multi-domain (MD) region, all of which are likely to be stable remanence carriers. We suggest that although the interpretation of the Day plot and its vari33 ants might be subject to ambiguities, if the magnetic mineralogy is known, it can still provide some useful insights about paleomagnetic specimens’ dominant domain state, average particle sizes and, consequently, their paleomagnetic stability.

Accurate assessments of glacier velocity are essential for understanding ice flow mechanics, monitoring natural hazards, and projecting future sea-level rise. However, the most commonly used method for deriving glacier velocity maps, known as feature tracking, relies on empirical parameter choices that rarely account for glacier physics or uncertainty. The GLAcier Feature Tracking testkit (GLAFT) aims to assess velocity maps using two statistically and physically based metrics. Velocity maps with metrics falling within our recommended ranges contain fewer erroneous measurements and more spatially correlated noise than velocity maps with metrics that deviate from those ranges. Consequently, these metric ranges are suitable for refining feature-tracking workflows and evaluating the resulting velocity products. GLAFT provides modulized workflows for calculating these metrics and the associated visualization, facilitating the velocity map assessments. To ensure the package is available, reusable, and redistributable to the maximum extent, GLAFT adopts several open science practices including the narrative documentation and demos using Jupyter Book and cloud access using Ghub. By providing the benchmarking framework for evaluating the quality of glacier velocity maps procedure, GLAFT enables the cryospheric sciences and natural hazards communities to leverage the rich glacier velocity data now available, whether they are sourced from public archives or made through custom feature-tracking processes.

Glaciers and ice sheets lose their mass by ablation (the output term of their surface mass balance) and discharging into a water body (dynamic loss). The latter is associated with multiple physical characteristics such as bed geometry, inland thinning, terminus stability, and basal conditions. Better assessing the dynamic loss, especially its spatiotemporal variability within a drainage basin, will help improve our understanding of the underlying processes and quantify the future contribution of sea level rise. We propose a new inverse model to decompose glacier elevation change and optimize the dynamic mass loss components for each pixel of the elevation data grid. The model unmixes the observed elevation change from remote sensing data using the modeled surface mass balance and the ice flux as constraints. We use two approaches to design the ice flux term; one is based on glacier surface velocity and the conservation of mass, and the other builds on the flow law and the Shallow Ice Approximation. We test the model for selected marine-terminating glacier outlets in the Greenland ice sheet. If the surface velocity can be decomposed into short-term (seasonal) and multi-year signals, our model may be able to further resolve the dynamic loss components of different physical processes.

We examined the effect of snow-ice formation on SnowModel-LG snow depth and density products. We coupled SnowModel-LG, a modeling system adapted for snow depth and density reconstruction over sea ice, with HIGHTSI, a 1-D thermodynamic sea ice model, to create SnowModel-LG_HS. Pan-Arctic model simulations spanned from 1 August 1980 through 31 July 2022. In SnowModel-LG_HS, domain average snow depth decreased by 20%, and snow density increased by 2% when compared to SnowModel-LG, with largest differences in the Atlantic sector. Averaged across the CryoSat-2 era (2011–2022), domain average April sea ice thickness retrievals from CryoSat-2 decreased by 7.7% when snow-ice was accounted for. Evaluation of SnowModel-LG HS against snow depth, snow-ice, and sea ice thickness observations highlighted the importance of snow redistribution over deformed sea ice. The findings suggest that neglecting snow and sea ice interactions in models can lead to substantial overestimation of snow depth over level ice.

A document by Kyungguk Min. Click on the document to view its contents.

Mantle plumes arising from deep sources in the Earth are thought to have played a critical role in determining the planetary geodynamics. The plumes originate mostly from gravitational or thermochemical instabilities at the core-mantle boundary, triggered by density fluctuations due to thermal or chemical variations. Understanding the initiation mechanics of such instabilities is key to comprehending the formation of these deep-mantle plumes, reflected from hotspots scattered around the globe. Previous studies have explained their growth within a theoretical framework of Rayleigh-Taylor (RT) instabilities. However, a critical aspect that has been largely overlooked is the potential influence of layer-parallel global flows on the dynamics and initiation processes of instabilities. The present study combines 2D finite element particle-in-cell numerical simulations with a linear stability analysis to show the impact of global flows on the growth kinematics of RT instabilities in a thermal boundary layer at the core-mantle boundary. The simulation results indicate that the global flow acts as a counter factor to dampen their growth rates. At a threshold global flow velocity the dampening effects completely suppress the instabilities, allowing the entire system to advect in the horizontal direction. The stability analysis also predicts a non-linear increase in the instability wavelength with increasing global flow velocity. These new findings imply that the spatial frequency of plumes can drop remarkably in kinematically active regions of Earth's mantle. This study finally offers a possible explanation for unusually large spacing between major hotspots in the light of instability mechanics under global flows.

A document by Roshan Raj Bhattarai. Click on the document to view its contents.

Icefalls are steep ice flow features that form over steps in bedrock elevation. With their high driving stresses, icefalls have long been assumed to have a constant ice flowspeed. This assumption has not been thoroughly tested as methods using satellite feature tracking rapidly loose coherence and long-term GPS installations on the ground are unlikely to be retrievable. In this study, we test the hypothesis that the Vaughan Lewis Icefall in Southeast Alaska experiences daily velocity variations with daily variations in subglacial hydrology. Using high resolution tiltmeters, we observe change in ice surface tilt across eight days at two sites near the glacier centerline. We find daily variation in ice surface tilt, suggesting there are variations in daily ice flowspeed velocity. A weak and lagged correlation with air temperature suggests that velocity variations may be due to daily variations in subglacial hydrology. Future modeling efforts focused on describing ice flow over icefalls should consider adding daily or seasonal velocity variations. These results additionally have implications for theoretical models of ogive formation, which could result from seasonal flow speed variations across icefalls.

A document by Saman Aryana. Click on the document to view its contents.