Sunlight warms sea surface temperature (SST) under calm winds, increasing atmospheric surface buoyancy flux, turbulence, and mixed layer depth in the afternoon. The diurnal range of SST exceeded 1 °C for 24% of days in the central tropical Indian Ocean during the Dynamics of the Madden Julian Oscillation experiment in October-December 2011. Doppler lidar shows enhancement of the strength and height of convective turbulence in the atmospheric mixed layer over warm SST in the afternoon. The turbulent kinetic energy dissipation of the marine atmospheric mixed layer scales with surface buoyancy flux like previous measurements of convective mixed layers. The time of enhanced mixed layer dissipation is out of phase with the buoyancy flux generated by nocturnal net radiative cooling of the atmosphere. Diurnal atmospheric convective turbulence over the ocean mixes moisture from the ocean to the lifting condensation level and forms afternoon clouds.

Very-long-period (VLP) volcano seismicity often represents subsurface magma movement, and thus provides insight into magma system geometry and magma properties. We develop a fully automated signal processing workflow using wavelet transforms to detect and assess period, decay rate, and ground motions of resonant VLP signals. We then generate and analyze a catalog of VLP seismicity over the 2008-2018 open-vent summit eruptive episode at Kilauea Volcano, Hawaii USA. VLP seismicity occurred throughout this eruption that involved a persistent lava-lake, multiple intrusions and rift zone eruptions, and a climactic caldera collapse. We characterize trends in two dominant magma resonances: the fundamental eigenmode of the shallow magma system is a vertical oscillation of the magma column in the conduit and lava-lake, and higher frequency eigenmodes largely consist of lateral lava-lake sloshing. VLP seismicity was mainly triggered by lava-lake surface perturbations, and less commonly from depth. Variation in periods and quality factors occurred on timescales from hours to years. VLP seismicity exhibited varying correlations over time with other datasets such as ground tilt, SO2 emissions, and lava-lake elevation. Variation in VLP properties also occurred over days to months preceding and following intrusions and rift zone eruptions. Changes in VLP ground motions over various timescales indicate evolution of shallow magma system geometry, which contributed to the variation in resonance. However much of the variation on timescales less than months is likely from changing magma density and viscosity, reflecting a variable shallow magmatic outgassing and convective regime within the open conduit over the ten year eruption.

Ambient noise surface wave tomography is an environmentally friendly and cost-effective seismic technique for subsurface imaging. However, noise sources acting from preferential azimuths may introduce bias in the Green’s function reconstruction and in the resultant velocity models. This study, focused at the deposit scale, investigates how to correctly merge the different phase velocity measurements at various frequencies, in order to fill the gap between natural and anthropogenic noise sources while adjusting the bias caused by changes in the azimuth of the source. The target is the Marathon PGE-Cu deposit (Ontario, Canada), an alkaline intrusion containing gabbros and syenites (ø = 25 km). Mineralisation is hosted by gabbros close to the inward-dipping footwall of the intrusion. The country rocks are Archaean volcanic breccias. 1024 vertical-component receivers were deployed for 30 days in two overlapping grids: a 200 m x 6040 m dense array with node spacing of 50 m, and a 4000 m x 2500 m sparse array with node spacing of 150 m. Beamforming analysis of the recorded data indicates variations in the distribution of noise. Below 5 Hz, the Lake Superior (SSW) is the dominant source of noise, while above 12 Hz, noise from the Canadian Pacific Railway and Trans-Canada highway (SW) is prominent. In the 5 - 12 Hz frequency band, surface-wave energy is dominant, and it comes from the Lake Superior and vehicle traffic. Between 12 Hz and 20 Hz, the signal is characterized by body-wave energy combined with less energetic surface waves, while above 20 Hz the imprint of body waves is dominant. We retrieved the fundamental mode of Rayleigh wave propagation from the recorded data set. The signal was down-sampled to 50 Hz, divided into segments of 30 minutes, cross-correlated and stacked. Surface wave dispersion curves were extracted from 2-km-long arrays. Besides, various phase velocity measurements were applied. Phase-velocities were inverted to S-wave velocity structures using different probabilistic approaches. The overall results show a high-velocity shallow anomaly, probably related to the gabbro intrusion hosting the mineralization, as well as other structures consistent with the geological model inferred from surface mapping and drill logs.

Sun–Jupiter decade-scale magnetic entanglement emerges from Wilcox Solar Observatory 1975-2021 N–S ≲150 μT mean-field data, as a global response of solar magnetic fields to the magnetar-type evolution of Jupiter ~2001–onward global magnetoactivity discovered recently in the 1–6 month (385.8–64.3 nHz) band of Rieger resonance. At extreme ≲20% field variance, the sudden Jovian deviation is so high it forced solar magnetoactivity devolution into inverse-matching response, at effectively moderate ≲1.5% mean-field variance. Thus as Jupiter magnetoactivity evolved sinusoidally, the Sun began mirror-compensating ~2002 (the epoch of Abbe number drop), reducing its magnetoactivity in decreasingly sinusoidal fashion to solar cycle 24 extreme minimum. For check, 2004-2021 WIND mission data revealed <0.5-var% (<5-dB) calm ≲50 nT interplanetary magnetic field at L1, slightly undulated by the Jupiter evolution impulse, thus excluding solar wind and Sun as impulse sources (confirmed by statistical fidelity waning down Jupiter–L1–Sun diffusion vector spaces, as 10^7–10^3–10^2). Magnetic tangling of stars and hot (<0.1 AU) Jupiters was blamed previously for observed star superflaring 10^2–10^7 times more energetic than the strongest solar flare. Accordingly, the Sun ante-impulse locking is a shock-absorbing mechanism — routine shutter-response to Jupiter recurrent phasing into the flare-brown-dwarf state — with which the Sun enters a grand minimum (sleep mode). As Jupiter intermittently becomes an indirect driver of Earth’s climate, the Sun prepares to discharge stored energy as a non-extinction ~10^32-erg superflare (currently overdue). The mechanism, in which warm/cold Jupiters too trigger (mild) superflares, possibly defends stars against incoming Jupiters.

• Two fresh anomalies observed in the eastern subpolar North Atlantic upper ocean during 1992-2017 share similar spatial characteristics. • Salt budget analysis shows the 2012-2016 fresh anomaly in the upper 200 m occurs due to transport of anomalous salinity by mean currents. • In contrast, the fresh anomaly in the 1990s is due to anomalous circulation of the mean salinity field.

Climate models have long-standing difficulties simulating the South Pacific Convergence Zone (SPCZ) and its variability. For example, the default Zhang-McFarlane (ZM) convection scheme in the Community Atmosphere Model version 5 (CAM5) produces too much light precipitation and too little heavy precipitation in the SPCZ, with this bias toward light precipitation even more pronounced in the SPCZ than in the tropics as a whole. Here, we show that implementing a recently developed convection scheme in the CAM5 yields significant improvements in the simulated SPCZ during austral summer and discuss the reasons behind these improvements. In addition to intensifying both mean rainfall and its variability in the SPCZ, the new scheme produces a larger heavy rainfall fraction that is more consistent with observations and state-of-the-art reanalyses. This shift toward heavier, more variable rainfall increases both the magnitude and altitude of diabatic heating associated with convective precipitation, intensifying lower tropospheric convergence and increasing the influence of convection on the upper-level circulation. Increased diabatic production of potential vorticity in the upper troposphere intensifies the distortion effect exerted by convection on transient Rossby waves that pass through the SPCZ. Weaker distortion effects in simulations using the ZM scheme allow waves to propagate continuously through the region rather than dissipating locally, further reducing updrafts and weakening convection in the SPCZ. Our results outline a dynamical framework for evaluating model representations of tropical–extratropical interactions within the SPCZ and clarify why convective parameterizations that produce ‘top-heavy’ profiles of deep convective heating better represent the SPCZ and its variability.

Barrovian-grade pelites in the Greater Himalayan Crystallines and Lesser Himalayan Formations exposed in the Himalayan core are separated by the Main Central Thrust (MCT). This fault system accommodated a significant amount of India-Asia convergence and is the focus of several models that explore ideas about the development of the range and collisional belts in general. Units separated by the MCT provide critical information regarding the mechanisms of heat transfer within collisional belts. Garnets collected across the MCT record their growth history through changes in chemistry. These chemical changes can be extracted and modeled using a variety of thermodynamic approaches. Here we describe and apply particular thermobarometric techniques to decipher the metamorphic history of several garnet-bearing rocks collected across the MCT in central Nepal, the Sikkim region, and NW India. Comparisons are made between the results of previously-reported conventional rim P-T conditions and P-T paths extracted using the Gibb’s method to isopleth thermobarometry and high-resolution P-T path modeling using the same data and assemblages. Regardless of calibrations used, the P-T conditions and paths, along with previously-reported timing constraints, are consistent with an imbrication model that suggest the MCT shear zone developed as rock packages within the LHF were progressively transferred. In this model, samples within the LHF travel along the MCT at a 5 km/Ma speed rate from 25 to 18 Ma. The hanging wall speed rate is 10 km/Ma, and topography progressively accumulates until a maximum height of 3.5 km. Once the topography is achieved at 18 Ma, a period of cessation is applied to the MCT between 18 and 15 Ma, and topography is reduced at a rate of 1.5 km/Ma. The model returns to activity within the MCT shear zone with the activation of the MCT footwall slivers from 8 to 2 Ma. P‐T changes recorded by the footwall garnets result from thermal advection combined with alterations in topography. For most MCT footwall samples, the P-T paths match the model predictions remarkably well. The P-T paths for some samples in central Nepal are also consistent high exhumation rates (>12mm/year) within the MCT shear zone since the Pliocene, a scenario predicted by this imbrication model.

The spatial patterns of earthquake ground motion amplitudes are commonly represented using a double couple model that corresponds to shear slip on a planar fault. While this framework has proven successful in explaining low-frequency seismic recordings, at higher frequencies the wavefield becomes more azimuthally isotropic for reasons that are not yet well understood. Here we use a dense array of nodal seismometers in Oklahoma to study the radiation patterns of earthquakes in the near-source region where wavefield scattering effects are limited. At these close distances, the radiation pattern is predominantly double couple at low frequencies (<15Hz). At higher frequencies, the recorded wavefield contains significant isotropic and residual components that cannot be explained as path or site effects, implying complexity in the rupture process or local fault zone structure. These findings demonstrate that earthquake source complexity can drive variability in the ground motions that control seismic hazard.

Deformation characteristics of sedimentary rocks significantly changed with the water content during drying. In tunnel construction, extremely small displacements such as geological disposal, are allowed. Therefore, the proper evaluation of such drying deformation phenomena is critical. In such scenarios, it is also essential to accurately assess water content changes in the rock masses. Furthermore, the excavation disturbed zone (EDZ) spreads around the tunnel owing to the excavation process. EDZ has a higher hydraulic conductivity than an intact rock mass. Therefore, it is essential to predict water content changes in EDZ within the scope of the drying deformation phenomena. In this study, we derived the exact solution to the Richards’ equation at the Neumann boundary, which can be used to describe the drying phenomena in sedimentary rocks. Using Japanese tuff, we conducted a permeability test and a mercury intrusion porosimetry test to obtain the water diffusion coefficient and verify whether their drying behavior can be described using the exact solution. Using the verified exact solution, we proposed a new stochastic differential equation that could be used to explain the local decrease in permeability and the increase in variations in EDZ, and applied the stochastic differential equation to 2D tunnel problem.

Defining a baseline for the frequency of off-normal occurrences at underground natural gas storage facilities is critical to maintaining safe operation and to the development of appropriate risk management plans and regulatory approaches. Currently used frequency-estimation methods are broadened to include critical factors of cause, severity, and uncertainty that contribute to risk. A Bayesian probabilistic analysis characterizes the aleatoric historical occurrence frequencies given imperfect sampling. Occurrence frequencies for the three main storage facility types in the United States (depleted oil-and-gas field storage, aquifer storage, solution-mined salt cavern storage) are generally on the order of 3 to 9 x 10–2 occurrences, of all causes (surface, well integrity, subsurface integrity) and severities (nuisance, serious, catastrophic), per facility-year. Loss of well integrity is associated with many, but not all, occurrences either within the subsurface or from there up to the surface. The probability of one serious or catastrophic leakage occurrence to the ground surface within the next 10 years, assuming constant number of facilities, is approximately 0.1–0.3% for any facility type. Storage operators and industry regulators can use occurrence frequencies, their associated probabilities and uncertainties, and forecasts for severity magnitudes to better prioritize resources, establish a baseline against which progress toward achieving a reduction target is measured, and develop more effective mitigation/monitoring/reduction programs in a risk management plan.

The thermal response of the martian subsurface due to solar forcing lacks direct measurements. The InSight mission provides the best opportunity to detect the thermal behavior of the subsurface since it was equipped with both air temperature sensors and a subsurface heat flow probe. Here, we model heat conduction under the InSight landing site based on the measured subsurface thermal parameters and air temperature records, which provide insights into heat flow in the martian subsurface. Daily temperature variation over 1 K occurs only within 25 cm under the ground surface. The highest absolute rate of temperature change appears around sol 440, which coincides closely with the season of the dominant number of marsquakes observed around sunset. Thermal-mechanical finite-element method simulations indicate that more potential afternoon marsquakes might exist but be covered by the wind noise. Our results indicate that most high-frequency and low-magnitude marsquakes are likely thermal in origin.

It is typically assumed that dinitrogen (N2) fixation and denitrification are mutually exclusive processes in riverine ecosystems because N2 fixation is favored in high light, low nitrogen (N) environments but denitrification is favored under anoxic, high N conditions. Yet recent work in marine and lake ecosystems has demonstrated that N2 fixation can happen under high N conditions and in sediments, challenging this assumption. We conducted a cross-ecoregion study to test the hypothesis that N2 fixation and denitrification would co-occur in streams and rivers across a range of reactive N concentrations. Between 2017 and 2019, we sampled 30 streams in 13 ecoregions, using chambers to quantify N2 flux using membrane inlet mass spectrometry, N2 fixation using acetylene reduction, denitrification using acetylene block, and microbial diversity using 16S gene sequencing. 25 of the study streams were part of the National Ecological Observatory Network or the StreamPULSE network, which provided data on water temperature, light, nutrients, discharge and metabolism. We found that N2 fixation rates were detectable in half of the streams surveyed, and were most frequently detected on rock, wood, and/or macrophyte substrates. Denitrification potential was detected in all streams, with rates 1-2 orders of magnitude higher than N2 fixation rates and the highest rates measured in sediments. Substrate heterogeneity, and associated variation in environmental conditions, appeared to facilitate the coexistence of N2 fixation and denitrification in the study streams. Rates of denitrification were significantly positively related to streamwater nitrate concentrations (r2 = 0.35), but N2 fixation rates were not, despite the common simplifying assumption that denitrification dominates the N2 flux in streams under high N and N2 fixation only occurs under low N conditions. Additional analyses are exploring reach to watershed characteristics, and metabolic regimes as drivers of cross-ecoregion patterns in processes.

Martian ice likely holds the key to interpreting Mars’ past climate, but much is still unknown regarding the distribution and properties of Mars’ ice deposits. It is well known that Mars has extensive polar ice caps the size of Greenland. Included in these large polar caps are the north and south polar layered deposits (NPLD and SPLD, respectively), that are composed of kilometers-thick deposits of water ice. In addition, surveys by Conway et al. (2012) and Sori et al. (2019) identified craters in the surrounding terrains that contain “outlying” deposits of ice, which may or may not have formed concurrently with the polar caps. There are many differences between the NPLD and SPLD, including higher dust content and sequestered CO2 within the SPLD, a younger surface age of the NPLD, and properties in some locations of the SPLD that causes a ‘fog-like’ scattering in radar observations. These differences between the NPLD and SPLD may or may not be shared in these outlying deposits, and may provide clues to the climate conditions under which the PLDs and outlier deposits formed. We have analyzed a total of 517 SHARAD radar tracks across 24 ice deposits within craters. For the northern population, we detected subsurface layers in 3 out of 4 crater deposits. In the southern population, we detected subsurface layers in 4 of the 20 crater deposits. Of the 4 southern crater deposits that exhibited subsurface layers, 3 were contiguous with the SPLD. We also found deposits with radargrams that contain fog, and one that contains a low reflectance zone. After examining the subsurface radar observations, we determined that the northern outlier deposits share many common characteristics with the NPLD, and thus may have a shared depositional history or at least were emplaced under similar environmental conditions. The southern outlying crater deposits exhibit a variety of subsurface characteristics, and likely represent 2 or more populations that may have differing depositional histories.

Department of Water Resources (DWR), in partnership with the Merced Irrigation District (MID), is conducting a reconnaissance level study to assess the potential of implementing Flood-MAR in the Merced River watershed within the San Joaquin Valley. One aspect of the Flood-MAR study focuses on reservoir operations using synthetic hydrology generated based on the Paleoclimate (Tree-Ring) Study methodology. The MID HEC-ResSim model was calibrated to simulate water supply and flood control operations over the water year. The model was modified to estimate water available for Flood-MAR based on flow at a downstream location, conveyance capacity and groundwater recharge capacity. Results include changes in storage at Lake McClure, flow in Merced River, water supply deliveries, and Flood-MAR deliveries due to Flood-MAR implementation. The study also assesses the vulnerability of reservoir operations due to changing hydrology by evaluating the effects of climate change on flood management, water supply reliability, and drought resiliency. The flood management aspect of the vulnerability analysis assesses change in peak flow, flow volume, and duration of flooding events. The water supply reliability assesses change in carryover storage and deliveries for irrigation demands. The drought resiliency assessment includes change in magnitude and duration of the historical and synthetic drought events. The results of the reservoir operations vulnerability analysis will be used to determine the multiple benefits of Flood-MAR implementation.

Dissolved iron (dFe) transported by the Amur River greatly contributes to phytoplankton growth in the Sea of Okhotsk. Nevertheless, there has been little research on the dFe source of rivers, especially in the Amur-Mid Basin which is situated in a sporadic permafrost area. In the Amur-Mid Basin, permafrost generally exists under wetlands in the flat valley, and these permafrost wetlands could be a dFe source of rivers. To asess the importance of the permafrost wetlands as a dFe source, first we made a landcover map with high resolution of 30 m using Landsat-8 data and a machine learning technique (decision tree analysis). As a result of decision tree analysis, three normalized indices (normalized diference vegetation index, normalized difference soil index, and normalized difference water index) and slope enabled us to classify landcovers into three vegetation types: wetland, forest, and grassland. Using this landcover map, we investigated the coverages of the permafrost wetland in the sampled watersheds and examined the correlation with river water chemistry (dFe, dissolved organice carbon: DOC, and electrical conductivity: EC). As a result, dFe and DOC concentrations showed a clear positive correlation (dFe: r2 = 0.66, DOC: r2 = 0.46) with the coverage of permafrost wetlands, while EC showed a negative correlation with those (r2 = 0.45). These findings are the first to demonstrate the direct evidence about the importance of permafrost wetlands to supply dFe and DOC to rivers in the Amur-Mid Basin.

The spatial separation of macroscopic rheological behaviours has led to independent conceptual treatments of frictional failure, often referred to as brittle, and viscous deformation. Detailed microstructural investigations of naturally deformed carbonate rocks indicate that both, frictional failure, and viscous mechanisms might operate during seismic deformation of carbonates. Here, we investigate the deformation mechanisms that were active in two carbonate fault zones in Greece by performing detailed slip-system analyses on data from automated crystal-orientation mapping transmission electron microscopy and electron backscatter diffraction. We combine the slip system analyses with interpretations of nanostructures and predictions from deformation mechanism maps for calcite. The nanometric grains at the principal slip surface should deform by diffusion creep but the activation of the (0001)<-12-10> slip system is evidence for a contribution of crystal plasticity. A similar crystallographic preferred orientation appears in the cataclastic parts of the fault rocks despite exhibiting a larger grain size and a different fractal dimension, compared to the principal slip surface. The cataclastic region exhibits microstructures consistent with activation of the (0001)<-12-10> and {10-14}<-2021> slip systems. Post-deformational, static recrystallisation and annealing produces an equilibrium microstructure with triple junctions and equant grain size. We propose that repeated introduction of plastic strain and recrystallisation reduces the grain size and offers a mechanism to form a cohesive nanogranular material. This formation mechanism leads to a grain-boundary strengthening effect resulting in slip delocalisation which is observed over six orders of magnitude (μm–m) and is expressed by multiple faults planes, suggesting cyclic repetition of deformation and annealing.

The MAVEN mission has measured an electron temperature spike at altitudes where the Martian atmosphere becomes optically thick and changes occur in the atmospheric chemistry. The temperature spike is consistent from orbit to orbit, but changes in location based on solar zenith angle (SZA) and has only been observed for SZA <80o. This letter presents the conditions under which it is observed and discusses possible sources. The electron temperature spike seems to be co-located with a temperature dip in the neutral atmosphere. The observed temperature spike/dip might be indicative of an inversion layer in the Martian atmosphere. The altitude location of the electron temperature spike is in the lower dynamo region where the electrons start to be unmagnetized. The observations are unlikely to be significant for overall Martian plasma dynamics, but are a clear indication that the large-scale Martian atmosphere is still not completely understood.

The polar summer mesosphere is the Earth’s coldest region, allowing the formation of mesospheric ice clouds. These clouds produce strong polar mesospheric summer echoes (PMSE) that are used as tracers of mesospheric dynamics. Here we report the first observations of extreme vertical drafts (±50~m/s) in the mesosphere obtained from PMSE, characterized by velocities more than five standard deviations larger than the observed vertical wind variability. Using aperture synthesis radar imaging, the observed PMSE morphology resembles mesospheric bores, i.e., narrow along propagation (3–4~km) and elongated (>10~km) transverse to propagation direction. Additionally, our event presents a large vertical extent (± 3–4~km), resembling a “super bore”. Powerful vertical drafts, intermittent in space and time, emerge also in direct numerical simulations of stratified flows, predicting non-Gaussian statistics of vertical velocities. This evidence suggests that our event, and perhaps previous bores, might result from the interplay of gravity waves and turbulent motions.