Glacial lake outburst floods (GLOFs) are a natural hazard that affects a number of communities around the world. GLOFs affect a number of downstream communities directly in Alaska, with a variety of different impacts. This research looks into the impact of two GLOFs in Alaska on two downstream communities: releases from Suicide Basin adjacent to Mendenhall Glacier which affect Juneau, Alaska as well as releases from the glacial dammed lake at Snow Glacier, which affect the Kenai Peninsula in Alaska. Specifically, this work analyzes GLOF impacts from a multidisciplinary perspective. For example, novel monitoring campaigns have been undertaken in recent years to better understand and estimate water levels in Suicide Basin. From using drone imagery to analyzing time lapse camera images, these new approaches have allowed for a deeper understanding of, and better preparation for, these flood events. In addition, the GLOF impacts in both Juneau and Kenai Peninsula affects a wide range of stakeholders. From federal and state agencies, to local actors and emergency responders, to homeowners and businesses operating in the floodplain, GLOFs impact these communities through different lenses. This work delved into understanding how hydrological information and other available GLOF informational resources are understood and utilized by the wide range of affected stakeholders. The goal of this work was to understand stakeholder comprehension of these scientific information and how this information is - or is not - used for decision-making regarding GLOFs. Findings from this work were provided to information providers to improve their understanding of stakeholder needs as well as to refine and develop new products to address unmet needs and gaps. This work shows the importance of cross-cutting, multi-discipline approaches to help ensure scientific information is understood and used by a wide variety of stakeholders but to also create avenues and pathways for the integration of stakeholder feedback in scientific products, particularly as they pertain to cryospheric hazards.

The South China Sea (SCS) is one of the largest marginal sea in southeast Asia. The northern continental margin of the SCS has been considered an intermediate between the magma-poor and magma-rich end members. Baiyun sag is located in the deep water area where the northern continental crust had been hyper-thinned to < 12km. The syn-rifting deposition in the Baiyun sag shows distinct features to a classic rift basin at the shallow water area. Based on the high-resolution 3D seismic data interpretation and drilling logging analysis, we interpret a structural sequence corresponding to the hyper-thinning process before the final breakup of the continent. This sequence is bounded by a classic breakup unconformity and a regional transgression surface in the syn-rift strata of the Baiyun Sag; within the sequence, a set of foreset reflectors suggesting a prograding shelf-margin delta. Analog to the Iberia margin of North Atlantic, we use the definitions of Lithospheric Breakup Surface (LBS) and Breakup sequence (BS) and determine the distributions of the LBS and BS in the Baiyun sag. Based on the logging results, we apply subsidence back stripping to recover the palaeogeomorphology background with the development of BS. Finally, based on isostasy, we restore the basin structure using the balanced section technique and analyze the controlling factor of coarse-grained deposition distribution. Our results refine the deposition process related to the hyper-extension and the final breakup of the continental margin.

The diurnal cycle of precipitation over the Central Himalaya is governed by a complex interaction between the diurnal cycle of tropical convection and local orographic flow. Understanding this interaction is crucial for model evaluation, where the simulation of such processes is highly sensitive to model resolution and choice of parameterisation schemes. In this study, the mean diurnal cycle is computed using GPM-IMERG data and is shown to be bimodal, with one peak in the late afternoon (1700 LT) and a stronger one in the early morning (0200 LT). This structure is an artefact of compositing, as individual days are typically associated with single peaks. The late afternoon ‘convective’ peak is shown to be linked to the diurnal cycle of tropical convection, whereas the early morning ‘katabatic’ peak is shown to be triggered by nocturnal downslope flow converging with the background monsoon circulation. As such, the katabatic peak is strongly favoured by an active monsoon trough, which provides greater southeasterly moisture flux to the foothills, resulting in increased low-level moisture flux convergence upon interaction with the katabatic northerlies. In contrast, when the trough is less active, precipitation is brought to the region by mesoscale convective systems, ranging in scale from tens to thousands of kilometres, resulting in convective peaks. We hypothesise that these peaks may be enhanced by anabatic flow. It is shown that the BSISO does not play a significant role in modulating either the timing or amplitude of the diurnal cycle; however, low-pressure systems do: either by intensifying the trough (and hence the katabatic peak), or, when further north, by providing deep convection (hence supporting the convective peak). Reanalyses and a 17-km model with parameterised convection capture both peaks, but overestimate the magnitude of the convective peak and underestimate the magnitude of the katabatic peak.

Recent studies have demonstrated that the difference in sea surface temperature anomalies (SSTAs) between the tropical Atlantic main development region (MDR) and the tropical Pacific (Niño 3) modulates Atlantic tropical cyclone activity. This study further explores the seasonality of Pacific and Atlantic contributions to Atlantic hurricane activity. Our analysis shows that while MDR and Niño 3 SSTAs are equally important for late-season (September-November) activity, early-season (June-August) activity is largely modulated by MDR SSTAs. This reflects the increased (reduced) variance of MDR (Niño 3) SSTAs in the early-season due to their phase locking to the seasonal cycle. Further analysis yields skillful forecasts using an MDR-Niño 3 interbasin index derived from hindcasts of the North American Multi-Model Ensemble with May initial conditions. However, the prediction skill for MDR SSTAs is lower than that of Niño 3 SSTAs, suggesting that increasing the prediction skill for MDR SSTAs is key to improving seasonal outlooks.

The short-term statistics of wave conditions in coastal waters around the UK have been investigated using over 40,000 half-hour long sea state records with significant wave height greater than 3 m. The extensive data set facilitates an assessment of various wave height and period distribution models in shallow and intermediate waters. The results reveal that the relative wave height Hs/D (where Hs is the significant wave height and D the water depth) can serve as a key indicator in choosing the distribution with least error in a given sea state. The Naess model is found to be the most accurate in describing the tail of the wave height distribution in a sea state for low relative wave heights (Hs/D < 0.2), and the depth-dependent van Vledder model for high relative heights (Hs/D > 0.4). In between these sea states, a transition in the performance of the deep-water and the depth-dependent models is visible. When details of the spectrum are not available, the Weibull distribution is the most accurate amongst applicable models, in spite of considerable variability in its parameter values. While the spectral bandwidth appears to have minimal impact on the distribution of wave heights in a sea state, it does appear to influence the distribution of wave periods. Wave period relationships based on measurements are found to deviate from empirical relationships proposed, for example, by the US Army Coastal Engineering Manual. Improved formulas that incorporate the spectral width are therefore proposed.

A novel challenge faced by the water scientists and water managers today is the efficient management of the available water resources for meeting crucial demands such as drinking water supply and irrigation at the same time ensuring sufficient water is available for other critical activities such as hydro-power generation. Modeling of optimal operation polices is imminent for better management of reservoir systems especially under competing multiple objectives such as irrigation, flood control, water supply etc., with decreasing reliability of these systems under climate change. This study compares six different state-of-the-art modeling techniques namely; Deterministic Dynamic Programming (DDP), Stochastic Dynamic Programming (SDP), Implicit Stochastic Optimization (ISO), Fitted Q-Iteration (FQI), Sampling Stochastic Dynamic Programming (SSDP), and Model Predictive Control (MPC), in modeling pareto-optimal operational policies considering two competing reservoir operational objectives of irrigation and flood control for the Pong reservoir system in Beas River, India. Pareto-optimal (approximate) set of operation policies were derived using the six methods mentioned above based on different convex combinations of the two objectives and finally the performances of the resulting sets of pareto-optimal operational solutions were compared with respect to resilience, reliability , vulnerability and sustainability indices. Modeling results suggests that the optimal-operational solution designed via DDP attains the best performance followed by the MPC and FQI. The performance of Pong reservoir operation assessed by comparing different performance indices suggest that there is high vulnerability (~0.65) and low resilience (~0.10) in current operations and the development of pareto-optimal operation solutions using multiple state-of-the-art modeling techniques might be crucial for making better reservoir operation decisions.

River bathymetry is an important parameter for hydrodynamic modeling; however, it is associated with large bias because direct large-scale measurements are impractical. Recent studies adjusted river bathymetry data based on assessment of the difference between modeled and observed water surface elevation (WSE); however, river discharge model uncertainties can lead to unintended errors in the correction. In this study, we propose a simple but robust correction method using the WSE bias, based on stage–discharge rating curves rather than time series data. The rating curve represents only the characteristics of the river section, and is not sensitive to instantaneous errors. Our results showed that the “corrected river bathymetry” converged among discharge experiments driven by noise-corrupted runoff forcing. Given the difficulty of eliminating discharge errors, a method for correcting river bathymetry that is free from discharge errors is important for improving hydrodynamic modeling.

Whether and where recycled oceanic crusts melt in the deep mantle are fundamentally important questions for understanding the evolution and dynamics of the Earth's mantle, and they currently remain unclear. Here, we find compelling evidence for the wide distribution of eclogite melting around a depth of 300 km by investigating the origins of the X-discontinuity. We show that both the transformation of orthopyroxene into high-pressure clinopyroxene and the coesite-stishovite transition are dominant mechanisms. The degree of partial melting of oceanic crust is crucial for the X-discontinuity mechanisms since melting promotes the enrichment of orthopyroxene by consuming solid silica. The silica phase transition dominates in the relatively low-temperature region, while the orthopyroxene phase transition in the high-temperature region results in the indistinguishable seismological Clapeyron slope of the X-discontinuity, with both transitions presenting a large positive Clapeyron slope. The X-discontinuity provides a key method for identifying partial melting of recycled oceanic crust.

Global ocean oxygen loss - deoxygenation - is projected to persist in the future. Previous generations of Earth system models (ESMs) have, however, failed to provide a consistent picture of how deoxygenation will influence oxygen minimum zones (OMZs; O2<= 80 μmol/kg), in particular the largest OMZ in the tropical Pacific Ocean. The expansion of the Pacific OMZ would threaten marine ecosystems and ecosystem services such as fisheries and could amplify climate change by emitting greenhouse gases. Here, we use the latest generation of ESMs (CMIP6) and a density framework that isolates oxygen changes in the thermocline and intermediate waters. We show that the Pacific OMZ expands by the end of the century in response to high anthropogenic emissions (multi-ESM median expansion of 2.4 * 10^15 m^3m, about 4% of the observed OMZ volume). The expansion is driven by a reduction of the shallow overturning circulation in the thermocline and a robust weakening of the oxygen supply to the upper OMZ in all ESMs. The magnitude of this expansion is, however, uncertain due to the less constrained balance between physical and biological changes in the lower OMZ. Despite uncertainties in the biological response, our results suggest that models with more complex biogeochemistry project weaker changes in the lower OMZ, and therefore stronger overall OMZ expansion. The fact that the OMZ largely expands in the upper ocean maximizes its ecological, economic, and climatic impacts (release of greenhouse gases).

Europa likely contains an iron-rich metal core. For it to have formed, temperatures within Europa reached ≳1250 K. At that temperature, accreted chondritic minerals - e.g., carbonates and phyllosilicates - would partially devolatilize. Here, we compute the amounts and compositions of exsolved volatiles. We find that volatiles released from the interior would have carried solutes, redox-sensitive species, and could have generated a carbonic ocean in excess of Europa’s present-day hydrosphere, and potentially an early CO2 atmosphere. No late delivery of cometary water was necessary. Contrasting with prior work, CO2 could be the most abundant solute in the ocean, followed by Ca2+, SO42-, and HCO3-. However, gypsum precipitation going from the seafloor to the ice shell decreases the dissolved S/Cl ratio, such that Cl>S at the shallowest depths, consistent with recently inferred endogenous chlorides at Europa’s surface. Gypsum would form a 3 - 10 km thick sedimentary layer at the seafloor.

Recent insights into the spatial organization of atmospheric convection have emphasized the importance of its correct representation in Earth System Models (ESM). This study explores new opportunities created when combining a thermal population model on a horizontal microgrid with a decentralized vertical transport model. To this purpose the recently proposed BiOMi population model (Binomials on Microgrids) is used. BiOMi mimicks a population of independent but interacting convective thermals, with their birth, movement and life cycle described as Bernoulli processes. Simple rules of interaction are introduced to reflect observed physical behavior in single cumulus clouds, such as pulsating growth and environmental deformation. Under these rules, thermals can congregate and form longer-lived coherent clusters or chains that resemble cumulus clouds. The formation and evolution of these clusters is a form of self-organization that retains convective memory. Through an online clustering method the microgrid is coupled to a spectral EDMF convection scheme, providing the cluster size distribution it needs as input. This way, the inherently 3D structure of organized convection can in principle be captured in reduced but efficient form. The system is fully decentralized in that central top-down bulk closures are avoided. The main science objective of this study is to provide proof of concept of decentralized frameworks of this kind. To this purpose the BiOMi-EDMF scheme as implemented in the DALES circulation model is tested for various LASSO cases of shallow convection at the ARM SGP site. We find that the scheme achieves stable and realistic diurnal quasi-equilibria (as shown in the figure), and that the associated self-organizing patterns on the microgrid are realistic. Impacts of spatial organization and convective memory on the parameterized transport will be investigated.

Late springtime Arctic mixed-phase convective clouds over open water in the Fram Strait as observed during the recent ACLOUD field campaign are simulated at turbulence-resolving resolutions. The main research objective is to gain more insight into the coupling of these cloud layers to the surface, and into the role played by interactions between aerosol, hydrometeors and turbulence in this process. A composite case is constructed based on data collected by two research aircraft on 18 June 2017. The boundary conditions and large-scale forcings are based on analysis data, while the case is designed to freely equilibrate towards the observed thermodynamic state. The results are evaluated against a variety of independent aircraft measurements. The observed cloud macro- and microphysical structure is well reproduced, consisting of a stratiform cloud layer in mixed-phase fed by surface-driven convective transport in predominantly liquid phase. A 3D volume rendering of the simulated liquid clouds is shown in the Figure. Comparison to noseboom turbulence measurements suggests that the simulated cloud-surface coupling is realistic. A joint-pdf analysis of relevant conserved state variables is then conducted, suggesting that locations where the mixed-phase cloud layer is strongly coupled to the surface by convective updrafts act as “hot-spots” for invigorated turbulence, cloud and aerosol interactions. A mixing-line analysis reveals that the turbulent mixing is similar to warm convective cloud regimes, but is accompanied by hydrometeor transitions that are unique for mixed-phase cloud systems. Distinct fingerprints in the joint-pdf diagrams also explain i) the typical ring-like shape of ice mass in the outflow cloud deck, ii) its slightly elevated buoyancy, and iii) an associated local minimum in CCN. The obtained modeling results advocate the application of this analysis method also to observational datasets.

The RHARM (Radiosounding HARMonization) algorithm is the first to provide homogenized radiosonde-based records of temperature, relative humidity and wind profiles since 1978, alongside an estimation of the observational uncertainty for each observation and pressure level. The algorithm and the dataset are presented in the companion paper. In this paper we assess the performance of the dataset through comparison with some of the most widely used climate data records. The RHARM adjustments reduce the difference with the reanalysis especially in the northern hemisphere for temperature and relative humidity. The study of temperature trends at different pressure levels reveals a good agreement between RHARM, reanalysis and existing radiosounding homogenized datasets (<0.1K per decade above 300 hPa, 0.25 K per decade below). For relative humidity, the discrepancies among the datasets are more significant, although RHARM trends are most similar to the reanalysis. For wind speed, the comparison indicates a good agreement above 300 hPa. Compared to IGRA, RHARM also improves by 50% the agreement with the estimated trends in the lower stratosphere from MSU (Microwave Sounding Unit) deep layer averages. For water vapour, the good performance of post-2004 RHARM data is quantified from the comparison of the 300 hPa monthly means in tropics between RHARM and AURA/MLS, as the absolute mean difference is 0.01 g/kg for RHARM and 0.03 g/kg for IGRA, and correlation increases from 0.95 to 0.99. A validation of the observational uncertainties of RHARM is also presented showing that they provide a good estimate or overestimate the theoretical distribution.

Understanding the driving processes at stake for the Circumpolar Deep Water (CDW) intrusion onto the Amundsen shelf is crucial. We use a multi-decadal ocean simulation at 1/12° to revisit the ocean dynamics at the Amundsen shelf break, distinguishing a western fresh shelf and an eastern warm shelf. While the prevailing presence of the Antarctic Slope Current - fed to the east of Russel Bay through vortex stretching of an outflow of melted waters - blocks CDW intrusions in the west, the contact of Antarctic Circumpolar Current (ACC) branches along the shelf in the east favors this inflow. Of particular importance is a southern ACC branch initiated to the south-east of the Ross Gyre, which interacts with the topography at the entry of the western Pine Island-Thwaites trough. Then, we link the ocean interannual-to-decadal variability at the shelf break with the ice-shelf basal melting and create a Fresh-Warm Boundary Index (FWBI) to follow the oscillation of the fresh-warm shelves limit through time in Russel Bay, which could be a focal point to understand the low frequency fluctuations of the basal melt. We suggest that not only a wind-induced Ekman pumping could favor the CDW inflow at the shelf break, but also topographic interactions, a bottom Ekman transport, a sea-ice–induced Ekman pumping resulting from strong surface currents, and the baroclinicity of the eastward along-shelf current in the west. Finally, we highlight that El Niño-Southern Oscillation has no strong correlation with the ice-shelf basal melt variability, except for the very recent years.

The mobilization and mixing of sediments by the activities of streambed inhabitants, referred to as sediment reworking, constantly modify the physical and hydraulic properties of streambeds. However, limited progress has been made to explore the influence of this sediment-organism interaction on hyporheic exchange. In this work, we advance the understanding of the role of macroinvertebrate sediment reworking in altering the hyporheic exchange flows in clogged streambeds. Laboratory experiments are conducted in re-circulating flumes following a control (clogging) and treatment (clogging + sediment reworking) based design. The experiments involve studying the interaction of model organisms (Lumbriculus variegatus) with fine sediment (clay) deposits, and its subsequent influence on hyporheic flow regime in homogenous model streambeds comprising fine sand, coarse sand, and gravel sediments. We observe that model organisms burrowed extensively into the clogging layer, mixed the clay particles with underlying grains, and eventually eroded or disintegrated the clogging layer at the bed surface in the treatment flumes. As a consequence, the treatment flumes exhibited greater solute penetration depth, shorter median and mean residence times, and higher hyporheic flux compared to their respective control flumes. The results also suggest that the modification of hyporheic exchange flows depends on the overall reworking of the beds including both fine and substrate sediments. The alteration of hydro-physical properties of streambeds and subsequently the hyporheic flow regime due to sediment reworking has direct implications for the biogeochemistry of hyporheic zones and may impact the overall quality of surface and sub-surface waters, particularly in low flow environments.

The advance of the cosmic ray neutron (CRN) sensing method for estimating field scale soil moisture relied largely on simulations of the footprint properties of epithermal neutrons (~0.5 eV - 100 keV). Commercially available CRN probes are usually additionally equipped with a thermal neutron (< 0.5 eV) detector. The potential of these measurements is rarely explored because relevant features of thermal neutrons, such as the footprint and the sensitivity to soil moisture are unknown. Here, we used neutron transport modeling and a river crossing experiment to assess the thermal neutron footprint. We found that the horizontal thermal neutron footprint ranges between 43 and 48 m distance from the probe and that the vertical footprint extends to soil depths between 10 and 65 cm depending on soil moisture. Furthermore, we derived weighting functions that quantify the footprint characteristics of thermal neutrons. These results will enable new applications of thermal neutrons.

Wildland fires involve complicated processes that are challenging to represent in chemical transport models. Recent airborne measurements reveal remarkable chemical tomography in fresh wildland fire plumes, which remain yet to be fully explored using models. Here we present a high-resolution large eddy simulation (LES) model coupled to chemistry to study the chemical evolution in fresh wildland fire plume. The model is configured for a large fire heavily sampled during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign, and a variety of airborne measurements are used to evaluate the chemical heterogeneity revealed by the model. We show that the model captures the observed cross-transect variations of a number of compounds quite well, including ozone (O3), nitrous acid (HONO), and peroxyacetyl nitrate (PAN), etc. The combined observational and modeling results suggest that the top and edges of fresh plume drive the photochemistry, while dark chemistry is also present but in the lower part of the plume. The model spatial resolution is shown to be very important as it may shift the chemical regime, leading to biases in O3 and NOx chemistry. Based on findings in this work, we speculate that the impact of small fires on air quality may be largely underestimated in models with coarse spatial resolutions.

The irregular variation of geomagnetic activity, caused by the solar wind interaction with the magnetosphere/ionosphere, occurs in a wide time interval (from seconds to annual and even larger periods) and amplitude ranges (from few to hundreds of nT). Major variation events (geomagnetic storms) can cause damaging effects and important perturbations to different human activities such as satellite communications, long distance radio broadcasting, navigation, surveying, etc. Furthermore, the induction of electric currents (geomagnetically induced currents – GICs) may affect all grounded conducting networks, in particular electrical power transmission systems. Useful proxies of GIC effects are still under debate; here, we identify the pros and cons of some different candidates. The intensity of geomagnetic activity is usually characterized by geomagnetic indices, among which the 3-hourly indices Kp and local K. In this study we compare 3-hour K and 1-hour K-derived local range indices, using geomagnetic time series from the mid-latitude Coimbra observatory (COI), in Portugal. We also compute smaller time-resolution geomagnetic and GIC indices such as the geomagnetic horizontal field components and their time derivatives, horizontal field magnitude and its time derivative and the LDi/LCi indices [Cid19]. We compare the computed indices with GIC simulations in the Portuguese transmission power grid, to evaluate which of them may be used to nowcast the induced currents. We suggest as a better GIC proxy, an index obtained from geomagnetic field components filtered by convolution with the uniform conductivity Earth filter (new EGIC index). Previous studies have considered the local ground conductivity to be an important factor to determine GIC amplitudes (e.g. [Tri07] and [Rib21]). We then obtain GIC estimations for power grid substations lying at different geological regions. Acknowledgements: This study is funded by national funds through FCT (Portuguese Foundation for Science and Technology, I.P.), under the project MAG-GIC (PTDC/CTA-GEO/31744/2017). FCT is also acknowledged for support through projects UIDB/50019/2020-IDL, PTDC/CTA-GEF/1666/2020 (MN) and PTDC/CTA-GEO/031885/2017 (MN). CITEUC is funded by FCT (UIDB/00611/2020 and UIDP/00611/2020). We acknowledge the collaboration with REN (Redes Energéticas Nacionais).