Carbon, water, and energy cycles are key processes controlling land-atmosphere interactions. Carbon and energy fluxes are both coupled with soil moisture (SM), leading to water-limited and energy-limited regimes. Functional relationships between carbon, water, and energy are key to understanding feedbacks between the land surface and atmosphere and give an estimate of the land-atmosphere coupling strength. Current carbon, water, and energy coupling relationships are commonly estimated at the point or satellite scale. These coupling relationships are expected to vary across scales. We investigated the carbon, water, and energy coupling relationships and the limiting thresholds from the field to satellite scale. We also investigated the effect of weather, seasons, and land cover on carbon-water-energy coupling strength. Carbon (carbon dioxide: CO2), energy (evapotranspiration: ET), and water (SM) were estimated using Eddy covariance and soil moisture monitoring systems at various FLUXNET sites in the Continental United States. These field measurements were used together with LANDSAT, MODIS, SMAP remote sensing satellites estimates of ET, CO2, and SM, respectively. Weather variables were obtained from Daymet (a gridded daily surface weather data product) and weather monitoring systems at the FLUXNET sites. This analysis provided insights to the spatial and temporal variations of the carbon, energy, and SM at different scales.

The deep roots of subduction megathrusts exhibit aseismic slow slip events, commonly accompanied by tectonic tremor. Observations from exhumed rocks suggest this region of the subduction interface is a shear zone with frictional lenses embedded in a viscous matrix. Here we use numerical models to explore the transient slip characteristics of finite-width frictional-viscous megathrust shear zones. Our model utilizes an invariant, continuum-based, regularized form of rate- and state-dependent friction (RSF) and simulates earthquakes along spontaneously evolving faults embedded in a 2D heterogeneous continuum. The setup includes two elastic plates bounding a viscoelastoplastic shear zone (subduction interface melange) with inclusions (clasts) of varying distributions and viscosity contrasts with respect to the surrounding weaker matrix. The entire shear zone exhibits the same velocity-weakening RSF parameters, but the lower viscosity matrix has the capacity to switch between RSF and viscous creep as a function of local stress state. Results show that for a range of matrix viscosities near the frictional-viscous transition, viscous damping and stress heterogeneity in these shear zones both 1) sets the ‘speed limit’ for earthquake ruptures that nucleate in clasts such that they propagate at slow velocities; and 2) permits the transmission of slow slip from clast to clast, allowing slow ruptures to propagate substantial distances over the model domain. For reasonable input parameters, modeled events have moment-duration statistics, stress drops, and rupture propagation rates that match natural slow slip events. These results provide new insights into how geologic observations from ancient analogs of the slow slip source may scale up to match geophysical constraints on modern slow slip phenomena.

A novel system of Monitoring Vibrations and Perturbations in the Lithosphere, Atmosphere, and Ionosphere (MVP-LAI) was established in Leshan, Sichuan, China in 2021. The system comprises 14 distinct instruments with 22 devices continuously monitoring changes in 14 geophysical parameters ranged between a few meter underground to ~350 km in altitude to examine and/or expose causal mechanisms of the LAI couplings. Note that the ground-based GNSS receivers of the system receive the electromagnetic signals from the geostationary BeiDou satellites that retrieve the total electron content over certain locations 24 × 7 without montage. Significant amplifications of TEC perturbations appear during the night since mid-May 2021. The M6.4 Yunnan and M7.4 Qinghai earthquakes occurred in Mainland China on 21-22 May 2021. The amplifications are related with the two earthquakes due to that the associated TEC perturbations reside over the epicenters. The resident TEC perturbations and ground vibrations close to the epicenters share a frequency of ~0.005 Hz, which can be attributed to the resonant coupling between the lithosphere and ionosphere.

Here we discuss a global ocean surface mixed layer statistical monthly climatology (GOSML) of depth, temperature, and salinity that includes means; variances; 5th, 50th, and 95th percentiles; as well as skewness and kurtosis. Ocean surface mixed layer properties are influenced by a wide variety of factors that operate over a wide variety of time scales and gravity. Mixed layer depths can shoal very quickly as a result of surface heating, precipitation, or “slumping” of horizontal density gradients. However, deepening the mixed layer in the presence of a strong pycnocline requires substantial buoyancy loss or strong wind mixing, which often takes more time. This pattern is clear in the annual cycle monthly mixed layer depth values, with deepening in the fall much slower than shoaling in the spring. The 95th percentile values are chosen as a reasonable indicator of ventilation depth, robust to extreme outliers. Mean mixed layer depths are on average 0.56 of 95th percentile mixed layer depths, with only 1% of values below 0.31 and 1% above 0.81. Over 71% of mixed layer depth distributions are skewed positive, usually when there are more shallow mixed layer depths than not and deep mixed layers tails are strong. Comparing 95th percentile depth conditions to mean values shows in late winter temperatures are generally lower in the subtropics and salinities generally higher in the subpolar regions, consistent with the importance of temperature in the midlatitudes and salinity in the higher latitudes in setting stratification.

Hydraulic roughness is a fundamental property in river research, as it directly affects water levels, flow strength and the associated sediment transport rates. However quantification of roughness is challenging, as it is not directly measurable in the field. In lowland rivers, bedforms are a major source of hydraulic roughness. Decades of research has focused on dunes to allow parameterisation of roughness. This study aims to establish the predictive capacity of current roughness predictors, and to identify reasons for the unexplained part of the variance in roughness. We quantify hydraulic roughness based on the Darcy-Weisbach friction factor calculated from hydraulic field data of a 78 km long trajectory of the Lower Rhine and River Waal in the Netherlands. This is compared to predicted roughness values based on dune geometry, and to the spatial distribution of the local topographic leeside angle, both inferred from bathymetric field data. Results from both approaches show the same general trend and magnitude of roughness values (friction factor f=0.019-0.069, mean 0.035). Roughness inferred from dune geometry explains 42% of the variance, for the best performing predictor. Efforts to explain the remaining variance from statistics of the local topographic leeside angles, which supposedly control flow separation, were unsuccessful. Unexpectedly, multi-kilometer depth oscillations explain 34% of the total roughness variations. We suggest that flow divergence associated with depth increase causes energy loss, which is reflected in an elevated hydraulic roughness. Depth variations occur in many rivers worldwide, which may imply a cause of flow resistance that needs further study.

The transport of methane from deep sediments towards the seafloor is widespread in ocean margins and has important biogeochemical implications for the deep ocean [1]. A significant portion (>80%) of methane entering the shallow sediments from below at present is oxidized by microbially-driven anaerobic oxidation of methane (AOM), which mainly involves a microbial consortium of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria. Isoprenoid Glycerol dialkyl glycerol tetraethers (GDGTs) derived from core lipid membranes of ANMEs are often well preserved in sediment records. Methane Index (MI) is an organic geochemical proxy for methane seepage intensity which weighs in the relative proportion of GDGTs (GDGT-1,-2, and -3) preferentially synthesized by ANMEs with that of non-methane-related biomarker contribution from planktonic and benthic sources (Crenarchaeols) [2]. This study analyzed the GDGT composition of sedimentary core lipids from IODP Site 1230 (Peru Margin) using two silica columns and a high-resolution and accurate mass Orbitrap Fusion Mass Spectrometer. Our results report novel GDGT isomers with concentration peaking at the Sulfate-Methane Transition Zones (SMTZ) with the highest AOM activity around 8 mbsf. Further, these isomers were almost absent above and below the SMTZ. Our observations suggest that these characteristic isomers of GDGT compounds preserved at the SMTZ depth are sourced from ANMEs. Identification of these novel isomers has important implications in refining the MI and additional GDGT based palaeoceanographic proxies like TEX86. 1. Akam et al. (2020), Frontiers in Marine Science 7, 206. 2. Y. G. Zhang et al. (2011), Earth and Planetary Science Letters 307, 525-534.

A robust multi-functional decision support system for widespread planning of nature-based solutions (NBSs) must incorporate components of social equity. NBS systems advance social well-being through enhanced levels of greenspace, which have been shown to improve physical health (e.g., heart disease, diabetes), mental health (e.g., post-traumatic stress disorder, depression), and socio-economics (e.g., property values, aesthetics, recreation). However, current optimization frameworks for NBSs rely on stormwater quantity abatement and, to a lesser extent, economic costs and environmental pollutant mitigation. Therefore, the objective of this study is to explore how strategic management strategies associated with NBS planning may be improved, while considering the tripartite interactions between hydrological, environmental, and societal conditions. Here, a large-scale NBS watershed was calibrated to local conditions using standard hydro-environmental modeling (i.e., EPA’s SWMM) and optimized on the basis of stormwater abatement, pollutant load reduction, and economic efficiency. The spatial allocation of possible NBS features was integrated with properties of social equity through a novel framework involving the Area Deprivation Index (ADI) and a composite Gini coefficient. By embedding social equity into the fabric of the NBS planning process, we provide an opportunity for improving social justice and spurring further community buy-in toward a balanced system. This study demonstrates how the optimal spatial placement of NBSs is location-dependent according to both the physical and human properties of the watershed.

The “dolomite problem” is a long-standing puzzle in sedimentology and mineralogy. Previous studies have shown that some dolostones are formed by microbes or in hydrothermal-burial environments. Here, we provide a different case in which an abiotic and Ca-rich proto-dolomite layer with weak cation ordering precipitated in Lake Sayram, Central Asia, during the Early Holocene. The 12-cm-thick layer, with abundant proto-dolomite (mean 50 wt% and maximum=81 wt%), consists of euhedral and rhombohedral grains. The similarδ18O values of proto-dolomites and ostracods at the same depth demonstrate that the former are authigenic. Morphologic and isotopic features of these proto-dolomites are distinct from those of microbial dolomites, suggesting an abiotic origin. We infer that this proto-dolomite layer is the product of a warming and arid climate, which is supported by regional climatic records. This study provides evidence for previous studies that dolomite can precipitate directly in “dolomite seas” at ambient temperature.

We describe a sampling of over two-dozen sociohydrology case studies that advance our understanding of two-way human-water phenomena. These case studies span broad geographic regions, including over 20 countries, and cover cross-cutting themes such as human behavior, social equity, water security, migration, water resources management, and ecological and environmental phenomena. Collectively, the cases reflect progress within the Panta Rhei decade and suggest new pathways for exciting research in the coming era, in particular by showing how socio-hydrologic modes of study transcend many geographical bounds. We synthesize these insights and describe approaches toward innovative modeling and predictive frameworks that promise to assist in real-world decision-making. We further describe how understanding of diverse and pertinent socio-hydrological phenomena relate to the United Nations’ Sustainable Development Goals (UNSDG) and Environment Programme (UNEP) for addressing climate action in a manner that manifests social well-being and resilient communities.

Areas of Jupiter’s moon, Europa, contain irregular ice floes that are illustrative of the massive disruption, reorientation, and refreezing experienced on Europa’s surface as Jupiter’s gravity imparts immense tidal forces that heat the moon. In recent years, various machine learning programs have been used to detect surface features on planetary bodies. Most commonly, such software works to count craters for estimating planetary surface age or to map sand-filled dune fields whose shapes may indicate wind or weather patterns. Creating software to automatically detect Europa’s jigsaw-like ice floes will accelerate scientific analysis of such terrains once higher resolution images of the moon arrive in the fall of 2022 from the Juno spacecraft and later from the forthcoming Europa Clipper mission. In this project, a U-net, a deep learning semantic segmentation model, was applied to images of the surface of Jupiter’s moon Europa taken by the Galileo spacecraft to detect ice floes in the moon’s Chaos Terrains. To measure the quality of the program developed, the Intersection over Union (IoU), a metric that measures the goodness of fit for semantic segmentation, was calculated. Throughout the course of the project, the IoU increased from a value of 0.0012 to 0.286 by adjusting hyperparameters including learning rate and epochs. Adjusting how the data was labeled also improved performance, functioning best when ice floes were hand-labeled using loose-fitting polygons rather than exact edge-mapping. As Galileo faced transmission issues, the usable dataset was limited to 23 images, 19 of which were used for training and 4 for testing. In the coming months, higher quality augmented data should provide additional training images that should further improve the performance of the U-net. Once the algorithm is sufficiently capable of identifying floes in the Chaos Terrains, it may later assist in selection of regions of interest for further study on Europa or even landing sites for a future proposed lander.

The kinetic ballooning/interchange instability (BICI) was recently found to produce azimutally narrow interchange heads extending into the dipole region from a reversed radial gradient of B$_Z$ in the near-Earth magnetotail. In their nonlinear evolution individual heads were predicted to detach from the reversed B$_Z$ gradient and grow into transient earthward moving northward magnetic field intensifications (dipolarization fronts; DFs). The distinguished signatures of such fronts would be their oblique propagation and cross-tail localization due to the finite k$_y$ structure of the BICI modes. Simultaneous conjugate observations of DFs by THEMIS probes at 11 Earth’s radii (R$_E$) downtail and of sudden brightening and growth of individual auroral beads by the all sky imagers on the ground have been suggested to be ionospheric signature of detached magnetotail interchange heads [Panov et al., 2019]. Here we compare such DFs with a simulated interchange head during later(detachment)-stage BICI head development. The comparison reveals similarly structured leading edges and trailing tails in both the observed DFs and the simulated BICI head. We further identify THEMIS trajectories through the DFs and find that the trajectories were due to oblique (earthward and dawnward) DF propagation. This analysis further supports the idea that BICI indeed releases obliquely propagating azimuthally localized dipolarization fronts in the Earth’s magnetotail.

The hydrologic dynamics and geomorphic evolution of watersheds are intimately coupled – runoff generation and water storage are controlled by topography and properties of the surface and subsurface, while also affecting the evolution of those properties over geologic time. However, the large disparity between their timescales has made it difficult to examine interdependent controls on emergent hydro-geomorphic properties, such as hillslope length, drainage density, extent of surface saturation. In this study, we develop a new model coupling hydrology and landscape evolution to explore how runoff generation affects long-term catchment evolution, and analyze numerical results using a nondimensional scaling framework. We focus on hydrologic processes dominating in humid climates where storm runoff primarily arises from shallow subsurface flow and from precipitation on saturated areas. The model solves hydraulic groundwater equations to predict the water table location given prescribed, constant groundwater recharge. Water in excess of the subsurface capacity for transport becomes overland flow, which generates shear stress on the surface and may detach and transport sediment. This affects the landscape form that in turn affects runoff generation. We show that (1) three dimensionless parameters describe the possible steady state landscapes that coevolve under steady recharge; (2) hillslope length increases with increasing transmissivity relative to the recharge rate; (3) three topographic metrics—steepness index, Laplacian curvature, and topographic index—provide a basis to recover key model parameters from topography (including subsurface transmissivity). These results open possibilities for topographic analysis of humid upland landscapes that could inform quantitative understanding of hydrological processes at the landscape scale.

In situ measurements of ionospheric and thermospheric temperatures are experimentally challenging because orbiting spacecraft typically travel supersonically with respect to the cold gas and plasma. We present O2+ temperatures in Mars’ ionosphere derived from data measured by the SupraThermal And Thermal Ion Composition (STATIC) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We focus on data obtained during nine special orbit maneuvers known as Deep Dips, during which MAVEN lowered its periapsis altitude from the nominal 150 km to 120 km for one week in order to sample the ionospheric main peak and approach the homopause. We use two independent techniques to calculate ion temperatures from the measured energy and angular widths of the supersonic ram ion beam. After correcting for background and instrument response, we are able to measure ion temperatures as low as 100 K with associated uncertainties as low as 10%. It is theoretically expected that ion and electron temperatures will converge to the neutral temperature at altitudes below the exobase region (~180-200 km) due to strong collisional coupling; however, no evidence of the expected thermalization is observed. We have eliminated several possible explanations for the observed temperature difference between ions and neutrals, including Coulomb collisions with electrons, Joule heating, and heating caused by interactions with the spacecraft. Our current study leaves one plausible heating mechanism, the release of internal energy from O2+ that becomes vibrationally excited as a result of atmospheric chemistry, but future work is needed to assess its validity.

Evapotranspiration (ET) is the major component of the hydrology cycle. Satellites provide a convenient way for gathering information to estimate regional ET. The most widely applied method for converting the instantaneous satellite measurement to daily scale assumes that evaporative fraction (EF), defined as the ratio of ET to the available energy, is constant during the daytime. However, this method was proved to underestimate the daily ET. This study implemented a theoretically improved EF algorithm to calculate daily ET with the decoupling factor method based on the Penman-Monteith and McNaughton-Jarvis equations. Seven improved algorithms were developed by assuming that various parameters remain constant during the day. The satellite-based ET estimates were compared with seven local flux tower measurements in China. The results showed that: (1) The original ET method calculated the daily evaporation more accurately than the other algorithms. However, the good fit was based on two compensating inaccuracies. Compared to the flux tower measurement, the original ET method underestimated the daily EF by 26% and overestimated the daily net radiation by 30%. (2) Six of the seven proposed algorithms underpredicted the daily ET by 30-60%, mainly due to the inaccurate daily net radiation. (3) The algorithm that assumed that the instantaneous decoupling parameter Ω* was equal to its daily value method calculated EF and ET with the relative errors of 8% and 10% when the inaccurate estimated daily net radiation was replaced by the observed flux tower data.

We report plasma wave observations of equatorial magnetosonic waves at integer harmonics of the local gyrofrequency of doubly-ionized helium (He++). The waves were observed by Van Allen Probe A on 08 Feb 2014 when the spacecraft was in the afternoon magnetic local time sector near L ≈ 4 inside of the plasmasphere. Analysis of the complementary in-situ energetic ion measurements (1-300 keV) reveals the presence of a helium ion ring distribution centered near 30 keV. Theoretical linear growth rate calculations suggest that the local plasma and field conditions can support the excitation of the magnetosonic waves from the unstable ring distribution. This represents the first report of the generation of magnetosonic equatorial noise via a ring distribution in energetic He++ ions in the near-Earth space plasma environment.

Eight Ml≥7.0 earthquakes have occurred around the Bayan Har block, NW Tibet, China, since 2000, resulting in a large number of casualties and countless economic loss. Near the western boundary of the Bayan Har block, four Ml≥6.0 Yutian earthquakes have occurred from 2008 to 2020. Stress interactions among them are comprehensively investigated by applying the ETAS (Epidemic-Type Aftershock Sequence) model and calculating (Coulomb failure stress change). The viscoelastic induced by proceeding Yutian earthquakes on hypocenters of the 2012, 2014 and 2020 Yutian earthquakes are -1.5004×10-4 , 3.5820×10-3 and 1.4770×10-1 MPa, respectively. The background probabilities of the 2008, 2012, 2014 and 2020 Yutian earthquakes are 0.87, 0.97, 1.5×10-3 and 8.7×10-5, respectively. Combining those two independent approaches, we conclude that the 2008 and 2012 Yutian earthquakes are more like background earthquakes and that the 2014 and 2020 Yutian earthquakes were triggered by the proceeding Yutian earthquakes.

The latitudinal and temporal variation of atomic oxygen (O) is opposite between the empirical model, MSIS and the whole atmosphere model, WACCM-X at 97-100 km. The [O] from WACCM-X has maxima at solstices and summer mid-high latitudes, similar to [O] from SABER. We use the densities and dynamics from WACCM-X to drive the Global Ionosphere Thermosphere Model (GITM) at its lower boundary, and compare it with the MSIS driven GITM. We focus on the differences in the modeling of the thermospheric and ionospheric semiannual oscillation (T-I SAO). Our results reveal that driving GITM with WACCM-X shifts the phase of T-I SAO to maximize around solstices. Nudging the dynamics in GITM towards WACCM-X, reduces the amplitude of the oppositely-phased SAO but does not completely correct its phase. We find that during solstices, WACCM-X driven GITM has a smaller temperature gradient between the hemispheres and weaker meridional and vertical winds in the summer hemisphere. This leads to accumulation of [O] at lower latitudes due to weaker meridional transport, resulting in solstitial maxima in global means. WACCM-X itself has the right phase of SAO in the upper thermosphere but wrong at lower altitudes. The exact mechanisms that can correct the phase of SAO in IT models while using SABER-like [O] in the MLT are currently unknown and warrant further investigation. We suggest mechanisms that can reduce the solstitial maxima in the lower thermosphere, for example, stronger interhemispheric meridional winds, stronger residual circulation, seasonal variation in eddy diffusion, and momentum from breaking gravity waves.

On Venus, relatively young deposits near volcanic and coronal summits with unique radar characteristics have been proposed to be emplaced by pyroclastic density currents (PDCs). The proposed units are laterally extensive, long-runout deposits showing moderate to high radar backscatter and circular polarization ratio in 12.6 cm wavelength synthetic aperture radar data. Previous studies have hypothesized that a recent resumption in volcanism activity in the form of PDC-forming eruptions could have emplaced these deposits. We model the dynamics of dense PDCs using a 2D, depth-averaged framework focusing on regions where stereo-derived topography coverage is available; this includes the flanks of Irnini Mons, Anala Mons, Didilia Corona and Pavlova Corona. Two different mechanisms of initiation— impulsive collapse of an eruption column and sustained pyroclastic fountaining — are considered. The results emphasize the importance of pyroclastic flow fluidization via high pore pressure in emplacing long-runout deposits along gently sloping (< 2°) volcanic flanks. We also show that collapse of columns >1.2 – 1.4 km tall as well as pyroclastic fountains lasting >400 s with fountain heights of 50 m are capable of generating pyroclastic flows that could emplace some of the smaller deposits studied. For the large deposits at Irnini Mons, more energetic flows resulting from taller column heights would be necessary; the dynamics of such flows under Venus’s conditions are not well understood. Distinguishing between the two initiation styles — column collapse and sustained fountaining — is not feasible with currently available datasets and would require higher resolution imagery and topography data.