Ice shelf collapse could trigger widespread retreat of marine-based portions of the Antarctic ice sheet. However, little is known about the processes that control the stability of ice shelves. Recent observations have revealed that ice shelves have topographic features that span a spectrum of wavelengths, including basal channels and crevasses. Here we use ground-penetrating radar data to quantify patterns of roughness within and between ice shelves. We find that roughness follows a power-law with scaling exponent approximately constant between ice shelves. However, the magnitude of roughness varies by over an order of magnitude between different ice shelves. Critically, we find that roughness strongly correlates with basal melt rate, suggesting that increased basal melt not only leads to deeper melt channels, but also increased fracturing, rifting and de-creased ice shelf stability. This hints that the mechanical stability of ice shelves may be more tightly controlled by ocean forcing than previously thought.

The kappa-correction is an easy-to-use method to correct for residual ionospheric errors in radio occultation (RO) data. It is a simple empirical model term that only depends on readily available data. While its basic utility was well proven in previous studies, including a recent predecessor study on RO climatologies under solar cycle variations, its performance for individual RO profile correction under diverse and extreme ionization conditions is unclear so far. Here we tackle this gap and focus on investigating (extremely) low and high solar activity and ionization conditions of individual RO events, including inspection of ionospheric symmetry between inbound and outbound raypaths. Using a global multi-year ensemble of MetOp-A and GRACE-A RO events over 2008 to 2015 as basis, we applied a sampling approach leading to six characteristic condition cases. These cases also relate to day and night time variations and geographic variations from the equatorial to the high latitude region. We inspected the kappa-correction and its performance relative to the standard bending angle correction for RO-retrieved stratospheric profiles and found mean deviations in temperature of near -0.3K in the upper stratosphere 40-45km for high ionization conditions, with extreme deviations exceeding -2K for strong inbound/outbound asymmetry. The kappa-correction term itself reaches a mean value near 0.05μrad under these high conditions. Low solar activity and ionization conditions lead to a mean correction smaller than 0.005μrad and mean temperature deviations smaller than 0.02K. An intercomparison to other quality datasets, predominantly showed a decrease in mean temperature difference when applying the kappa-correction.

With the rapid development of wireless communication technology and the increasing demand for communication quality in various fields, spread spectrum communication (SSC) and multiple input multiple output (MIMO) technology have become crucial research directions in the field of military communication, and space-time block coding (STBC) is an indispensable key technology in MIMO systems. This paper combined the excellent instrument interaction ability of LABVIEW and the data processing ability of MATLAB to build a direct sequence spread spectrum-space time block coding (DSSS-STBC) model based on circular mapping (CM) spread spectrum code, aiming at realizing multi-domain joint transmission of information in space, time, and power domains. The results demonstrated that the joint simulation platform of LABVIEW and MATLAB/Simulink successfully confirmed the superior spread spectrum performance of chaotic spreading codes based on circular mapping compared to traditional spreading codes. In addition, the multi-domain joint coding combining DSSS and STBC significantly enhanced the reliability and interference resistance of the communication system.

Tree water source variation in semi-arid ecosystems is important to understand because climatic shifts towards lower snowpack and increased drought affect water availability in subalpine forests of the western US. Here, we use daily in situ measurements of stable isotopes (2H) in soil and tree water, soil matric potential and sap flow to study tree water uptake dynamics. We instrumented three soil profiles down to 90 cm, as well as three Aspen and Engelmann Spruce trees near Gothic, Colorado, in the East River watershed. We observed the fate of natural 2H variations in rainfall, soil, and plants from June to October 2022, and in August 2023 we conducted a 2H labeled water irrigation experiment. Our observations showed that transpiration was reduced by all trees, but partially compensated by shifting the dominant water source from 60 to 90 cm within days of a dry period. Intense rainfall quickly shifted the plant water uptake partially to top soil layers. Changes in water uptake depths were similar between aspen and spruce, but rainfall infiltration was low in the spruce stand due to high canopy interception. Therefore spruce transpiration was lower and relied more on snowmelt. However, both species relied on snowmelt to sustain transpiration and groundwater recharge from monsoonal rains was not observed. These findings highlight the important role of snowmelt stored in the deep soil layers for subalpine forest drought response and the dominant fate of monsoonal rainfall to become transpiration rather than recharging groundwater and streams in the Upper Colorado River.

In this paper, we examine the solar wind energy input (expressed by −Vx × Bs, where Vx is the x component of the solar wind velocity and Bs is the southward component of the interplanetary magnetic field IMF Bz) for an onset of magnetic reconnection in the near-Earth magnetotail. There are 41 events in which in situ observations of magnetic reconnection were made by Geotail. Magnetic reconnection in the postmidnight (premidnight) sector of the plasma sheet occurred under strong (weak) solar wind energy input conditions. Furthermore, we study temporal variations in the solar wind energy input with two different approaches using ground magnetic field observations and proton injections at geosynchronous altitude. These two analyses confirmed the preference of the postmidnight sector for the onset of magnetic reconnection under the strong solar wind energy input conditions. It is also found that the medium and weak solar wind energy input moves the onset location to earlier magnetic local times. The onset location of magnetic reconnection in the near-Earth magnetotail is controlled by the solar wind energy input through the global magnetospheric dynamics during the loading period.

The ocean plays a major role in the moderation of anthropogenically-induced climate change by absorbing roughly a quarter of anthropogenic CO2 (Cant). This absorption of Cant by the ocean leads to ocean acidification, threatening marine’s life. The North Atlantic Ocean encompasses the highest ocean storage capacity of Cant per unit area. The subpolar North Atlantic gyre is subject to a large seasonal to decadal variability that might impact Cant storage. To investigate Cant evolution over the 2011-2021 period and its relationship with ocean dynamics in this region, we use the Argo-O2 array combined with neural networks and a back-calculation method (φCTO method). We compute monthly time-series of Cant in the Labrador and Irminger Seas. We show that Cant concentrations in the first 2000 dbar of the Labrador and Irminger Seas are strongly affected by winter deep convection, especially between winter 2015 and winter 2018. The Cant inventories in the top 2000 dbar of the Labrador and Irminger Seas increase through time, at rates of 1.63±0.32% yr-1 and 1.49±0.30% yr-1, respectively. Our monthly Argo-based Cant estimates complement high-quality ship-based measurements acquired at a biennial or lower frequency. Additionally, this study shows that Cant concentrations and Cant inventories in deep convection areas may depend on the method employed to calculate Cant. As a consequence, we take over the model ensemble idea and propose to use several methods to compute Cant, which would give its methodological uncertainty.

We apply the Backus-Gilbert approach to normal mode center frequency data, to constrain jumps in P, S, bulk-sound speed and density at the “660” discontinuity in the earth’s mantle (~650-670 km depth). Different 1D models are considered to compute sensitivity kernels. When using model PREM (Dziewonski and Anderson, 1981) as reference, with a “660” at 670 km depth , the best-fitting jumps in density, P and S wave-speeds range from (5.1-8.2)%, (5.3-8.0)\%, (5.0-7.0)%, respectively, so the PREM values lie outside the ranges of acceptable density and P wave-speed jumps. When shifting the depth of “660” to 660 km, the density and S wave-speed jumps increase while the P wave-speed jump decreases. Normal mode data do not support a global transition at 650 km depth. The density jumps are closer to those of pyrolite than PREM while our bulk-sound wave-speed jumps suggest a larger garnet proportion at “660”.

In their paper, Le mouël et al, (2019) argued that over the past 150 years “most of the variability of surface temperatures could be natural and primarily controlled by the Sun”. We do not agree with their conclusions for several reasons which are (1) a biased interpretation of the Fourier and SSA spectrum, which show no significant co-variability between sunspot amounts and emperature, (2) the small radiative forcing associated with the long-term sunspot variability, and finally the evidence that the slowly-varying components of the temperature and sunspots time-series show opposite trend in the last 30 years.

The radiolysis of porewaters by uranium, thorium, and potassium in mineral grains is a recognised source of molecular hydrogen in rock- and sediment-hosted fluids. This radiolytic hydrogen is of geomicrobiological interest as a potential energy source (electron donor) for microbial metabolism, especially in energy-limited settings such as the marine deep biosphere or the subsurface of Mars. Previous efforts to predict the production of radiolytic hydrogen from columns of rock and sediment have tended to rely upon analytic models that cannot account for the attenuation of mineral radiation by grains larger than ~30 microns. To address this, we have developed a Monte Carlo method to simulate the physics of mineral radiation and evaluate the production of H2 as a function of mineral grain size and radioisotope composition. The results confirm that grain size is a major control on radiolytic H2 yield. For example, using the standard geological classification of grain sizes, we find that clay can produce up to an order of magnitude more H2 per unit time than sand. The magnitude of this effect is illustrated using compositional data from real geological units in order to demonstrate the dependence of radiolytic hydrogen flux on natural radionuclide concentration and bulk porosity.

To discern spatial and explore possible existence of temporal variations of upper crustal anisotropy in an ~15 km section of the San Jacinto Fault Zone (SJFZ) that is composed of the Buck Ridge and Clark faults in southern California, we conduct a systematic shear wave splitting investigation using local S-wave data recorded by three broadband seismic stations located near the surface expression of the SJFZ. An automatic data selection and splitting measurement procedure is firstly applied, and the resulting splitting measurements are then manually screened to ensure reliability of the results. Strong spatial variations in crustal anisotropy are revealed by 1694 pairs of splitting parameters (fast polarization orientation and splitting delay time), as reflected by the dependence of the resulting splitting parameters on the location and geometry of the raypaths. For raypaths traveling through the fault zones, the fast orientations are dominantly WNW-ESE which is parallel to the faults and may be attributed to fluid-filled fractures in the fault zones. For non-fault-zone crossing raypaths, the fast orientations are dominantly N-S which are consistent with the orientation of the regional maximum compressive stress. A three-dimensional model of upper crustal anisotropy is constructed based on the observations. An apparent increase in the raypath length normalized splitting times is observed after the 03/11/2013 M4.7 earthquake, which is largely attributable to changes in the spatial distribution of earthquakes before and after the M4.7 earthquake rather than reflecting temporal changes of upper crustal anisotropy.

Ultra-low velocity zones (ULVZs) above the core-mantle boundary (CMB) are observed structures that may be related to the liquid outer-core. As ”thin patches” of dramatically low seismic-wave velocity, they are occasionally found near the base of mantle plumes or in/near high seismic-wave speed regions above the CMB. The causes of their morphology and geodynamics remain unclear, and simulation of high-density melts diverge from observations. We introduce a two-dimensional time-dependent Stokes two-phase flow (with melt migration) numerical model to investigate the evolution of high melt-fraction regions affected by CMB-mantle tangential flows, amidst a hot mantle plume and an optional neighboring cold downwelling. We find that (a) the participation of cold sources with temperature differences between ~4000 K at the plume central regions to <~3900 K at the plume-cooling flanks, separated by horizontal distances of approximately 100 ±50 km are necessary for dense melts (fractional mass-density difference >+1–2%, <+10%) to attain total-mass quasi-stability, (b) an enhanced tangential-horizontal flow in reverse circulation within the broad plume base (with speeds >1–3 times the lowermost-mantle characteristic flow speeds); are necessary for high aspect-ratio-morphology melt-lenses to be compatible with seismic observations. Stresses exerted on variable CMB topography may arise from lateral motion of localized outer-core rigidity-zone structures. The CMB-mantle tangential flow and/or outer-core interacting with CMB-topography may help generate mega-ULVZs, particularly if they appear along the edges of large low-shear-wave-velocity provinces (LLSVPs) or in/near high-seismic-speed “cold” zones. A strong link exists between ULVZ morphology-evolution and the dynamic and heterogeneous environment in-around the CMB.

Ab initio molecular dynamics calculations on a carbonate-silicate-metal melt were performed to study speciation and coordination changes as a function of pressure and temperature. We examine in detail the bond abundances of specific element pairs and the distribution of coordination environments over conditions spanning Earth’s present-day mantle. Average coordination numbers increase continuously from 4 to 8 for Fe and Mg, from 4 to 6 for Si, and from 2 to 4 for C from 1 to 148 GPa (4,000 K). Speciation across all pressure and temperature conditions is complex due to the unusual bonding of carbon. With increasing pressure, C-C and C-Fe bonding increase significantly, resulting in the formation of carbon polymers, C-Fe clusters, and the loss of carbonate groups. The increased bonding of carbon with elements other than oxygen indicate that carbon begins to replace oxygen as an anion in the melt network. We evaluate our results in the context of diamond formation and of metal-silicate partitioning behavior of carbon. Our work has implications for properties of carbon and metal-bearing silicate melts, such as viscosity, electrical conductivity, and reactivity with surrounding phases.

Carbonyl sulfide (OCS) is an important atmospheric sulfur species that plays a dominant role in the formation of (non-volcanic) stratospheric sulfate aerosol in the middle stratosphere. Major uncertainties in surface sources and sinks and inconsistent model representation of vertical transport limit understanding of OCS distribution, particularly in the sparsely sampled upper atmosphere. During the 2022 Asian Summer Monsoon Chemical & CLimate Impact Project (ACCLIP) campaign in-situ measurements of OCS in the Upper Troposphere and Lower Stratosphere (UTLS) at the eastern edge of the Asian Summer Monsoon anticyclone (ASM), showed significant OCS enhancements (>750 ppt) near the tropopause from convectively influenced air parcels. Here we compare these novel Asian UTLS measurements with long term satellite observations and regional measurements to broaden understanding of OCS trends and its transport by the ASM. Trajectory analysis identifies the main source regions for deep convective lofting and demonstrates ASM entrainment of OCS enriched parcels in the UTLS, allowing evaluation of global model predictions for OCS’s stratospheric influence. The ACCLIP dataset provides vital in-situ validation of limited vertically resolved OCS data in a region of significant anthropogenic emissions, which serves to enhance our understanding of the global sulfur budget.

Metal grade, as a critical property, is used during mineral exploration, ore sorting and mineral processing. Geochemical bore core data is the primary source of determining pay and deleterious metal grades. The pay metal grade receives more attention than the deleterious metal grade due to its economic value in determining the profitability and viability of mining projects. However, estimating deleterious metal grades is also crucial for optimising mine planning, ore sorting, stockpiling, and mineral processing. Metal grade usually contains extrema, or “outliers” due to measurement error, latent geological features, and spatial heterogeneity of mineral distribution. The outliers of deleterious metal grades can produce significant regression bias as the outliers are overweighted in traditional regression model. This will further complicate decision-making for ore sorting optimisation and mineral processing resulting in excessive chemical dosage, water, and energy expense. We present a Bayesian linear regression model with Gaussian mixture likelihood (BLR-GML) to identify deleterious Fe grade outliers in the relationship with pay metals of Cu in a porphyry Cu deposit. Results show that the BLR-GML model dramatically reduces mean square error and provide more accurate inference than maximum likelihood estimation. We also illustrate how outliers are crucial during mine planning and can be used as a cost function when selecting block size and orientation. BLR-GML model offers a reliable way to capture outliers in the linear relationship of metal grades. This is particularly valuable for mineral inference that supports decision-making through the minerals value chain and our goal of sustainable metal supply.

Temperature is the principal driver of global HCHO and its primary oxidation precursor biogenic volatile organic compounds (BVOCs). We revisit such a temperature (T-) dependency globally, leveraging TROPOMI HCHO column data. We find substantial variations in the T-dependency of biogenic HCHO across plant functional types (PFTs), with the highest over Broadleaf Evergreen Tropical Trees (doubling every 6.0 K ± 2.1 K) and lowest over Arctic C3 Grass (doubling every 30.8 K ± 9.6 K). The GEOS-Chem model interprets HCHO columns’ T-dependency at the PFT level (r = 0.87), with a 16% discrepancy on average. The discrepancy can be explained by BVOC emissions T-dependency for Broadleaf Evergreen Tropical Trees and Warm C4 Grass and can be attributed to the insensitivity of HCHO columns to BVOC emissions for other PFTs. Our findings underscore a potentially magnified variation of BVOC emissions by GEOS-Chem and MEGAN therein, particularly in regions experiencing greater temperature variations.

The dawn–dusk confinement of magnetic reconnection site in the near-Earth magnetotail is established on the basis of Geotail observations. Geotail has made more than 50 encounters with magnetic reconnection in association with the onset of substorms in the near-Earth magnetotail at radial distances of 20–30 RE in the period of 1994–2019. Ground magnetic field observations are examined for these events, and geosynchronous spacecraft observations are investigated for a limited number of cases. The magnetic reconnection site is located in the upward (from the ionosphere to the tail) field-aligned current part of large-scale substorm current system derived from ground mid-latitude magnetic variations. The site is confined to the localized dawn–dusk extent of the 1-h local time, just west of the center of the large-scale substorm current system. The short dawn-dusk length of the X-line implies that magnetic reconnection inherently proceeds as the two-dimensional dynamics in the magnetotail meridional plane. Rapid dipolarization with upward field-aligned currents occurs at geosynchronous altitude near the meridian of the magnetic reconnection site. This study demonstrates that rapid dipolarization in the inner magnetosphere is produced with earthward outflows from magnetic reconnection and that intense upward field-aligned currents are a direct consequence of magnetic reconnection.

Biogenic emission models are developed on the foundation of leaf physiological processes and driven by a set of physical and biological factors. To estimate emissions online, many studies used weather forecasting models coupled with simple biogenic emission algorithms, in which the canopy physiological parameters were neglected or oversimplified. In this study, the land surface scheme CLM4 (Community Land Model version 4) coupled in the advanced Weather Research and Forecasting model (WRF) was used to determine canopy physiological parameters. The MEGAN (Model of Emissions of Gases and Aerosols from Nature) algorithms embedded in CLM4 scheme used these parameters to estimate biogenic emissions. The emission estimated by using leaf temperature in our study were about 23% higher than that based on air temperature as in the previous methods. Compared with studies neglecting shaded canopy, the separate treatments of sunlit and shaded leaves in this study lowered the estimations by a factor of 2 through decreasing diffuse radiaton absorbed by sunlit canopy. Dynamic weather history was used in our study to replace the fixed values in the original MEGAN-CLM4 code. An emission inventory of isoprene and monoterpenes in China was established for the year 2018. The estimates were evaluated against field measurements. Generally, the coupled model produced a reasonable simulation in both emission budgets and spatiotemporal distribution of biogenic emissions.

Weak Temperature Gradient (WTG) modeling using a small cloud-resolving model (CRM) admits multiple equilibria depending upon the initial model conditions. A new kind of equilibrium is presented here which undergoes a periodic and steady-state oscillation that is emergent from static boundary conditions. The periodic oscillation is shown to be a moisture mode with an oscillating vertical motion profile shape generated by the interaction between vertical motion and radiation. A simple two-mode model based on decomposing the vertical motion profile and associated radiative cooling variations can describe the oscillation.