While it remains debated if the mineral deposits mined for phosphorus fertilizer are running out, phosphorus insecurity is an emerging global issue. We explore how it is linked to the current linear phosphorus economy (LPE) and the historic and current implications. The problems are multifold: there are geopolitical concerns over phosphorus deposits held only by a few nations, sharply rising costs of phosphorus fertilizers, heavy metal contaminants affecting soil and food, problematic phosphorus mining wastes, and the widespread environmental degradation caused by fertilizer inefficiencies. A new phosphorus economy can resolve these problems. Transitioning to a sustainable use of phosphorus demands a circular phosphorus economy (CPE). A CPE supports several Sustainable Development Goals and enables countries without phosphorus deposits to achieve greater phosphorus autonomy. We illustrate current problems with case studies and outline opportunities for change. The CPE will feature phosphorus recovery facilities, waste valorisation technologies, and improved fertilizer formulations that are customised to crop systems. We highlight examples of the rapidly advancing CPE that forms an integral part of the bioeconomy and the circular economy.

The cascade hazard, heat stress (preconditioned) and heavy rainfall (response) in close succession have become frequent in several areas of the globe, causing critical infrastructure failures. Although some regions of South Asia witness deadly humid heat stress, little is known about the linkage of humid heat stress (HHS; high temperature compounded by humidity) versus record rainfall and cascade hazard due to compound (same or lagged-day) occurrences of both extremes. We leverage ground-based meteorological records from 1970-2018 to analyze the risk of extreme precipitation preceded by heat stress over selected urban locations of India using a multivariate conditional-probability approach. We show that humid heat is likely to intensify the extreme rainfall, especially during the core monsoon (June-September) season. This phenomenon is associated with moisture convergence and large upper tail distributions of peak precipitation over several sites. Our insights to compound flood hazard would benefit (re)-insurance and flash flood forecast, devising adaptations.

Accurately tracing the sources and fate of excess PO43- in waterways is necessary for sustainable catchment management. The natural abundance isotopic composition of O in PO43- (δ18OP) is a promising tracer of point source pollution, but its ability to track diffuse agricultural pollution is unclear. We tested the hypothesis that δ18OP could distinguish between agricultural PO43- sources by measuring the integrated δ18OP composition and P speciation of contrasting inorganic fertilisers (compound v rock) and soil textures (sand, loam, clay). δ18OP composition differed between the three soil textures sampled across six working livestock farms: sandy soils had lower overall δ18OP values (21 ± 1 ‰) than the loams (23 ± 1 ‰), which corresponded with a smaller, but more readily leachable, PO43- pool. Fertilisers had greater δ18OP variability (~8‰) driven by both fertiliser type and manufacturing year. Upscaling these values showed that ‘agricultural soil leaching’ δ18OP signatures could span from 18 – 25 ‰, and are influenced by both fertiliser type and the time between application and leaching. These findings emphasise the potential of δ18OP to untangle soil-fertiliser P dynamics under controlled conditions, but that its use to trace catchment-scale agricultural PO43- losses is limited by uncertainties in soil biological P cycling and its associated isotopic fractionation.

Hydrologic sciences depend on data monitoring, analyses, and simulations of hydrologic processes to ensure safe, sufficient, and equal water distribution. These hydrologic data come from but are not limited to primary (lab, plot, and field experiments) and secondary sources (remote sensing, UAVs, hydrologic models) that typically follow FAIR Principles (FAIR Principles - GO FAIR (go-fair.org)). Easy availability of FAIR data has become possible because the hydrology-oriented organizations have pushed the community to increase coordination of the protocols for generating data and sharing model platforms. In addition, networking at all levels has emerged with an invigorated effort to activate community science efforts that complement conventional data collection methods. However, it has become difficult to decipher various complex hydrologic processes with increasing data. Machine learning, a branch of artificial intelligence, provides more accurate and faster alternatives to better understand different hydrological processes. The Integrated, Coordinated, Open, Networked (ICONs) framework provides a pathway for water users to include and respect diversity, equity, and inclusivity. In addition, ICONs support the integration of peoples with historically marginalized identities into this professional discipline of water sciences. This article comprises three independent commentaries about the state of ICON principles in hydrology and discusses the opportunities and challenges of adopting them.

The Blackfoot Reservoir volcanic field (BRVF), Idaho, USA, is a bimodal volcanic field that has hosted explosive silicic eruptions during at least two episodes, as recently as 58 ka. Using newly collected terrestrial and marine gravity data, two large negative anomalies (−16 mGal) are modeled as shallow (<1 km) laccoliths beneath a NE-trending alignment of BRVF rhyolite domes and tuff rings. Given the trade-off between density contrast and model volume, best-fit gravity inversion models yield a total intrusion volume of 50−120 km3; a density contrast of −600 kg m-3 results in model intrusion volume of 63 km3. A distinctive network of 340°−360° trending faults lies directly above and on the margins of the mapped gravity anomalies. Most of these faults have 5−10 m throw; one has throw up to ∼50 m. We suggest that the emplacement of shallow laccoliths produced this fault zone and also created a ENE-trending fault set, indicating widespread ground deformation during intrusion emplacement. The intrusions and silicic domes are located 3−5 km E of a regional, 20 mGal step in gravity. We interpret this step in gravity as a change in the thickness of the Upper Precambrian to lowermost Cambrian quartzites in the Meade thrust sheet, part of the Idaho-Wyoming Thrust Belt. Silicic volcanism in the BRVF is a classic example of volcanotectonic interaction, influenced by regional structure and creating widespread deformation. Exogeneous and endogenous domes are numerous in the region. We suggest volcanic hazard assessments should account for potentially large-volume silicic eruptions in the future.

The outgoing longwave radiation (OLR), which consists of the thermal radiation from both the atmosphere and surface, is of critical importance to the Earth radiation energy budget. To understand the global OLR distribution, it is important to quantify the varying atmospheric and surface contributions. In this work, we present such a quantification using radiative transfer computations based on global reanalysis atmospheric data. By dissecting the OLR simulated following the radiative transfer equation, we quantitatively measure the layer-wise atmospheric contributions to OLR and compare it to the surface contribution in different spectral bands. One focus of this study is on the OLR in the far-infrared, for which new satellites are expected to provide unprecedented measurements. We find that around 45% of the global mean OLR is radiated in the far-infrared and in polar regions the far-infrared contribution can increase to 60%. Our vertical decomposition of OLR discloses that the enhanced far-infrared contribution in the polar regions mainly results from a stronger surface (as opposed to atmosphere) contribution. Our analysis also reveals that the tropopause layer makes a minimum contribution to the OLR, which may be a unique spectroscopic feature of the Earth atmosphere. Clouds are found to reduce the atmospheric contribution in the far-infrared while enhancing it in the mid-infrared.

We conducted dynamic viscoelastic measurements of three clay minerals in a solid–liquid two-phase state: kaolinite, illite, and smectite with water. These constituents of concentrated (dense) suspensions were investigated using a high-temperature and high-pressure rheometer, to understand tectonic and non-tectonic phenomena in the shallow part of a fault system, such as shallow slow slip events in subduction zones, and landslides on fault or bed planes. We observed shear strain rate dependencies of phase angles of both dynamic stress and strain waveforms on the rheometer at varying temperature and pressure. The pressure and temperature dependence of the viscoelastic properties of the system can be qualitatively understood by applying the Zwanzig–Mountain theory. The local packing fraction change owing to dynamic oscillations affects the changing viscoelastic properties in systems such as shallow fault systems.

As a preliminary step to install the First Magnetic Observatory of Honduras, the local geomagnetic components are being computed in Tegucigalpa, Honduras (TEG), for the temporal interval 2010 –2013, using the Tsyganenko and Sitnov 2005 (J. Geophys. Res. 110, A03208, 2005: TS05) semi-empirical magnetospheric model. The diurnal variation of H (Sq) is obtained from the Chiripa Observatory (Costa Rica) data, using the International Quiet Days and the Normal Orthogonal Component Analysis. Pearson’s correlation coefficients are calculated between the H-component computed with the TS05 model in the Tegucigalpa coordinates and the Chiripa Observatory (CRP) data. The best correlations are obtained in days with Kp < 4, when the Sq and the quiet daily variation are removed from the CRP-H data and the TEG-H-component respectively. Seven TS05 magnetospheric currents are obtained in order to evaluate their contribution to the Sq. Using the Normal Orthogonal Component Analysis, the Chapman-Ferraro current fits better in the 0.00–12.00 local time interval, and the Birkeland currents fit better in the 12.00–24.00 local time interval.

Solar wind electrons play an important role in the energy balance of the solar wind acceleration by carrying energy into interplanetary space in the form of electron heat flux. The heat flux is stored in the complex electron velocity distribution functions (VDFs) shaped by expansion, Coulomb collisions, and field-particle interactions. We investigate how the suprathermal electron deficit in the anti-strahl direction, which was recently discovered in the near-Sun solar wind, drives a kinetic instability and creates whistler waves with wave vectors that are quasi-parallel to the direction of the background magnetic field. We combined high-cadence measurements of electron pitch-angle distribution functions and electromagnetic waves provided by Solar Orbiter during its first orbit. Our case study is based on a burst-mode data interval from the Electrostatic Analyser System (SWA-EAS) at a distance of 112 RS (0.52 au) from the Sun, during which several whistler wave packets were detected by Solar Orbiter’s Radio and Plasma Waves (RPW) instrument. The sunward deficit creates kinetic conditions under which the quasi-parallel whistler wave becomes unstable. We directly test our predictions for the existence of these waves through solar wind observations. We find whistler waves that are quasi-parallel and almost circularly polarised, propagating away from the Sun, coinciding with a pronounced sunward deficit in the electron VDF. The cyclotron-resonance condition is fulfilled for electrons moving in the direction opposite to the direction of wave propagation, with energies corresponding to those associated with the sunward deficit. The quasilinear diffusion of the resonant electrons tends to fill the deficit, leading to a reduction in the total electron heat flux.

Working with airborne electromagnetic (AEM) data acquired in the Kaweah Subbasin in the Central Valley of California, U.S.A., we developed a new approach for imaging the top of the bedrock and the confining Corcoran Clay layer. Our approach included multiple L2-norm and Lp-norm inversions as well as an interpolation process. The major improvement in imaging the two targets was made in the Lp-norm inversion step by incorporating prior knowledge. For the Corcoran Clay, pairs of resistivity and driller’s logs at two wells guided the selection of the best resistivity model and were used to increase the accuracy of the estimated Clay thickness. The bedrock surface was poorly constrained by well data in the existing groundwater model, appearing as a flat surface. We had good AEM data coverage in the area so had higher confidence in the obtained map of the bedrock surface at depths ranging from 15 m to 160 m. There was relatively good agreement between the location of the Corcoran Clay in the AEM data (depth ranging from 50 to 130 m and thickness ranging from 3 to 25 m) and the existing groundwater model, with both depth and thickness showing ~15% relative difference. The AEM data provided information about the continuity of the Corcoran Clay that is challenging to capture in the well data. The locations of the bedrock and Corcoran Clay were used in a structurally-constrained inversion to improve the imaging of the smaller-scale resistivity structure.

Projection of the global monsoon (GM) system is essential for water resource management, food security, and policymaking. Here we investigate projected changes in global monsoon area (GMA) and global monsoon intensity (GMI) with specific global warming levels, using two datasets of large-ensemble simulations. Both datasets project quasi-linear increases in GMA and GMI with global warming. The GMI over Northern-Hemisphere continents is consistently enhanced, while the GMI over Southern-Hemisphere continents are dominated by opposite changes in the GMI over South America. In addition, both datasets show enhanced monsoon intensity over most parts of regional monsoon domains, except for the North American monsoon. The different changes of the North American monsoon are up on projected temperature differences between the equatorial eastern Pacific and the tropical Atlantic. Moisture budget shows that the thermodynamic component always makes a large positive contribution to the increase in monsoon precipitation, while evaporation has a smaller positive contribution, except for the East Asian monsoon. The contribution of the dynamic component shows large differences for different regional monsoons. Therefore, the different changes in regional monsoon precipitation are mainly caused by the dynamic component.

Tsunami Squares is a computationally lightweight tsunami and inundation simulator which utilizes a unique cellular automata technique. We make modifications to the underlying algorithm which result in increased accuracy and enhanced waveform resolution. These improvements leave Tsunami Squares well suited for machine learning applications where large pre-computed tsunami simulation databases are required. Previous implementations relied heavily on a smoothing algorithm which acts as a moving average applied to the water surface heights and velocities to eliminate anomalies at every time step. Although this allowed the simulation to function properly, it brings several unwanted effects such as reduced wave detail and lowered energy. A solution is found by shifting the location at which the water surface gradient is calculated, reducing the amount of anomalies in the simulation, and thus lowering the amount of smoothing needed by a factor of $\sim 10$. Also introduced is a new method to conserve energy locally, compared to previous methods which reference a simulation-wide energy calculation. We make comparison tests were made using the 2011 Tohoku tsunami along with the 2010 Maule tsunami to demonstrate the improvements made.

Two oceanographic cruises were completed in September 2016 and August 2017 to investigate the distribution of particulate organic matter (POM) across the northeast Chukchi Shelf. Both periods were characterized by highly stratified conditions, with major contrasts in the distribution of regional water masses that impacted POM distributions. Overall, surface waters were characterized by low chlorophyll fluorescence (Chl Fl<0.8 mg m-3) and particle beam attenuation (cp<0.3 m-1) values, and low concentrations of particulate organic carbon (POC<8 mmol m-3), chlorophyll and pheophytin (Chl+Pheo<0.8 mg m-3), and suspended particulate matter (SPM~2 g m-3). Elevated Chl Fl and Chl+Pheo (~2 mg m-3) values measured at mid-depths below the pycnocline defined the subsurface chlorophyll maxima (SCM), which exhibited moderate POC (~10 mmol m-3), cp (~0.4 m-1) and SPM (~3 g m-3). In contrast, deeper waters below the pycnocline were characterized by low Chl Fl and Chl+Pheo (~0.7 mg m-3), high cp (>1.5 m-1) and SPM (>8 g m-3) and elevated POC (>10 mmol m-3). POM compositions from surface and SCM regions of the water column were consistent with contributions from active phytoplankton sources whereas samples from bottom waters were characterized by high Pheo/(Chl+Pheo) ratios (>0.4) indicative of altered phytoplankton detritus. Marked contrasts in POM were observed in both surface and mid-depth waters during both cruises. Increases in chlorophyll and POC were measured in mid-depth waters during the September 2016 cruise following a period of downwelling-favorable winds, and in surface waters during the August 2017 cruise following a period of upwelling-favorable winds.

Australian fires are a primary driver of variability in Australian atmospheric composition and contribute significantly to regional and global carbon budgets. However, biomass burning emissions from Australia remain highly uncertain. In this work, we use surface in situ, ground-based total column and satellite total column observations to evaluate the ability of two global models (GEOS-Chem and ACCESS-UKCA) and three global biomass burning emission inventories (FINN1.5, GFED4s, and QFED2.4) to simulate carbon monoxide (CO) in the Australian atmosphere. We find that emissions from northern Australia savanna fires are substantially lower in FINN1.5 than in the other inventories. Model simulations driven by FINN1.5 are unable to reproduce either the magnitude or the variability of observed CO in northern Australia. The remaining two inventories perform similarly in reproducing the observed variability, although the larger emissions in QFED2.4 combined with an existing high bias in the southern hemisphere background lead to large CO biases. We therefore recommend GFED4s as the best option of the three for global modelling studies with focus on Australia or the southern hemisphere. Near fresh fire emissions, the higher resolution ACCESS-UKCA model is better able to simulate surface CO than GEOS-Chem, while GEOS-Chem captures more of the observed variability in the total column and remote surface air measurements. We also show that existing observations in Australia can only partially constrain global model estimates of biomass burning. Continuous measurements in fire-prone parts of Australia are needed, along with updates to global biomass burning inventories that are validated with Australian data.

Little is known about Southern Ocean under-ice phytoplankton, despite their suspected potential-ice and stratification conditions permitting-to produce blooms. We use a distributional approach to ask how Southern Ocean sea ice and under-ice phytoplankton characteristics are related, circumventing the dearth of co-located ice and phytoplankton data. We leverage all available Argo float profiles, together with freeboard (height of sea ice above sea level) and lead (ice fractures yielding open water) data from ICESat-2, to describe co-variations over time. We calculate moments of the probability distributions of maximum chlorophyll, particulate backscatter, the depths of these maxima, freeboard, and ice thickness. Argo moments correlate significantly with freeboard variance, lead fraction, and mixed layer depth, implying that sea ice dynamics drive plankton by modulating how much light they receive. We discuss ecological implications in the context of data limitations, and advocate for diagnostic models and field studies to test additional processes influencing under-ice phytoplankton.

As the sea-ice modeling community is shifting to advanced numerical frameworks, developing new sea-ice rheologies, and increasing model spatial resolution, ubiquitous deformation features in the Arctic sea ice are now being resolved by sea-ice models. Initiated at the Forum for Arctic Modelling and Observational Synthesis (FAMOS), the Sea Ice Rheology Experiment (SIREx) aims at evaluating current state-of-the-art sea-ice models using existing and new metrics to understand how the simulated deformation fields are affected by different representations of sea-ice physics (rheology) and by model configuration. Part I of the SIREx analysis is concerned with evaluation of the statistical distribution and scaling properties of sea-ice deformation fields from 35 different simulations against those from the RADARSAT Geophysical Processor System (RGPS). For the first time, the Viscous-Plastic (and the Elastic-Viscous-Plastic variant), Elastic-Anisotropic-Plastic, and Maxwell-Elasto-Brittle rheologies are compared in a single study. We find that both plastic and brittle sea-ice rheologies have the potential to reproduce the observed RGPS deformation statistics, including multi-fractality. Model configuration (e.g. numerical convergence, atmospheric forcing, spatial resolution) and physical parameterizations (e.g. ice strength parameters and ice thickness distribution) both have effects as important as the choice of sea-ice rheology on the deformation statistics. It is therefore not straightforward to attribute model performance to a specific rheological framework using current deformation metrics. In light of these results, we further evaluate the statistical properties of simulated Linear Kinematic Features (LKFs) in a SIREx Part II companion paper.

Sentinel-3 A&B radar altimeters yield sea surface height measurements in both a high-precision Synthetic Aperture Radar Mode (SARM), and a Pseudo-Low Resolution Mode (PLRM). We stacked repeat cycles from both missions and in both modes to compare their resolution of small seamounts. Stacking entailed removing non-geoidal heights and height errors, testing for consecutive measurements over ocean, aligning to common locations at 1 km intervals along a synthetic track, and forming a median height profile. These profiles are available from the National Centers for Environmental Information (NCEI) data repository. Global maps show that, over the oceans, the median height is usually derived from more than 49 cycles, and the typical error in an individual PLRM measurement is approximately 1.9 times greater than an individual SARM measurement. We applied a seamount detection bandpass filter to the median profiles and compared their spectral resolution to that of the Satellite for ARgos and AltiKa (SARAL) AltiKa mission. Small seamounts are similarly resolved by Sentinel-3 A&B SARM data and by the SARAL/AltiKa data.

This article is composed of two independent commentaries about the state of ICON principles (Goldman et al. 2021) in cryosphere science and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (Section 2) Observational and modelling data research and application in cryosphere sciences and (Section 3) Expanding undergraduate research experiences in cryosphere science. We found that many cryosphere-related research projects and data sharing initiatives engage in integrated, coordinated, open, and networked research. These efforts should be continued and improved. Specifically, we recommend standardizing methodologies and data, and removing existing barriers to data access and participation in our field. We acknowledge that such ICON-FAIR-aligned efforts are cost- and labor-intensive. They require leadership and accountability but they also have the potential to increase the diversity and knowledge of the cryosphere research community in the future.