Abstract Fire plumes are rising columns of heated air masses, consisting of gaseous and particulate matter generated by combustion, affecting air quality, climate and public health. The chemical species released undergo secondary reactions and participate in chemical and physical interactions, altering the properties of the fire plume. The ability of the plume to be transported across short and long distances, depending on the atmospheric conditions, reveals the high importance of unraveling the chemical pathways influencing its inner and outer pollutants. Fresh plumes, close to the fire source, typically exhibit high temperatures and rapid reactions. In contrast, aged plumes differ in composition due to shifts in chemical regimes. The presence of sunlight influences oxidative reactions, while its absence favors oxidation paths driven by NO x chemistry. The complexity of fire plume chemistry presents challenges in efficient characterization of species formation and decomposition. It also directly influences gas‐phase species chemical pathways, in‐plume evolution and formation of secondary air pollutants, as well as particulate matter composition and fate. This review provides a detailed description of the chemical mechanisms and pathways inside fresh and aged fire plumes and discusses the implications of critical parameters influencing plume composition. Main tracers are identified, and key processes are described, with information reviewed from laboratory, field, and satellite studies. Unaddressed aspects and emerging opportunities are discussed to provide potential future directions of investigation.
Abstract Concerted exploration and a ten‐fold increase in Martian meteorites reveal a mostly ancient (>4 Ga), lithologically diverse mafic crust (igneous SiO 2 ranging from ∼40%–70%), commonly exhibiting alkaline affinities and with felsic compositions restricted to ancient crust. Most crustal growth (∼80%) took place during the pre‐Noachian, resulting from magma ocean processes. Later crustal additions continued at diminishing rates to the latest Amazonian (<200 Ma). Data from the first fully operational seismometer (InSight mission) indicate the crust is 49 7 km thick on average (∼4 1% of the primitive mantle), with an intracrustal discontinuity, of possible global extent, at about 20–30 km depth. InSight results also suggest a ∼150 km‐thick molten silicate layer (MSL) at the base of the mantle, a possible remnant of the early magma ocean. The MSL represents a distinctive, incompatible (including heat producing) element‐enriched geochemical reservoir, comparable in physical size to the crust. A model for Martian crustal composition indicates a mildly incompatible and heat‐producing element‐enriched basaltic composition (e.g., SiO 2 = 48%, K 2 O = 0.5%, La N /Yb N ∼ 1.8) that becomes less incompatible element‐enriched over geological time. The petrological nature of the crust likely varies in a complex way with depth that may explain the intracrustal seismic discontinuity. The crust contains ∼45 10% of the most incompatible elements in the primitive mantle and this composition is consistent with a mass balance model among crust, MSL, “depleted” mantle and primitive mantle. A geodynamic model for Mars can be constructed that is consistent with geophysical and geochemical constraints currently available.
Abstract River sand and gravel are mined worldwide at volumes that now rival their natural replenishment, yet quantitative knowledge of this mining activity and its consequences lags far behind many other global environmental pressures. We synthesize 411 peer‐reviewed studies published since 1974 within a new Driver‐to‐Management Pathway for Sustainable Sand and Gravel Mining framework that links socio‐economic demand, spatial‐temporal extent of extraction, hydrogeomorphic change, socio‐ecological disruption, and management response. Evidence shows a pronounced scale mismatch: regional‐to‐global drivers fuel largely unreported local extraction, while impacts propagate well beyond mining sites. In most documented cases, annual removal exceeds bed‐material supply several‐fold, producing channel incision, bank collapse, declining groundwater tables, deteriorating water quality, and inland migration of saline water in coastal areas. These physical changes cascade into habitat loss, infrastructure damage, and livelihood insecurity, especially across rapidly developing regions of Asia and Africa. Despite the proliferation of impact studies (69% of the literature), research is dominated by hydrogeomorphic perspectives, with ecological and socio‐economic impacts far more often treated as secondary or co‐occurring components rather than primary foci; meanwhile, only 27% of studies quantify extraction extent and 24% analyze demand drivers, hampering the design of effective interventions. Together, these findings highlight the need for basin‐scale monitoring, cross‐boundary governance, and demand‐side interventions that explicitly link extraction limits to sediment budgets.
Abstract The lightning return stroke is the most impactful aspect of a lightning flash. It has a transformative effect on the Earth system by igniting wildfires and by fixing nitrogen oxides in the atmosphere. It also has important detrimental impacts on societal infrastructure by causing billions of dollars in losses every year to power transmission and communications industries. The impacts of a lightning return stroke are due to its intense electrical current, which surges when lightning channels connect to a ground structure, and travels rapidly through those channels toward the cloud. The intense energy deposition in the atmosphere results in emissions across the entire electromagnetic spectrum. In this work, we present an overview on how to calculate the lightning return stroke electrical current using the Telegrapher's Equations, which describe the propagation of electrical signals guided by a conductor. This article has three main goals. First, it presents a tutorial overview on how to assemble a basic model of the lightning return stroke. Second, the article explains from basic principles the dominant features of the current wave, including: the genesis of channel‐base current, and the subsequent propagation, attenuation, and dispersion. Third, it also serves as a literature review by drawing parallels between the return stroke properties inferred from the Telegrapher's Equations and those established in previous theoretical and experimental research.
Abstract Propagating waves on the ocean surface can be represented as a stochastic process whose statistics are characterized by a spectrum. This paper reviews methods for measuring the wave spectrum and related quantities. Observations begin by sensing fluid dynamical properties of the sea surface over space and/or time. Visual observations, collected routinely since the mid‐18th century, comprise the longest‐running wave record. Nearshore measurement methods continue to advance, including traditional pressure and acoustic sensing as well as newer technologies like distributed acoustic sensing and LiDAR. Detailed small‐scale wave physics can now be explored with measurement techniques using light, including stereo‐imaging and polarimetry. Reductions in the size, cost, and power consumption of microelectronics have propagated through ocean wave instrumentation, most notably in wave buoys. Global networks of freely drifting miniature wave buoys offer novel observational capabilities. Remote sensing techniques based on radar and LiDAR continue to evolve and are widely deployed from land, ships, aircraft, autonomous vehicles, and satellites. Spaceborne altimeters form one of the most important records of wave height, and new spaceborne sensors now observe directional spectra globally with sampling akin to traditional altimetry. Aircraft and autonomous systems provide strategic sampling capabilities for detailed process studies and access to extreme storm environments. The quality and quantity of ocean wave measurements have never been greater. This review aims to help make sense of it all.
Abstract Accurately predicting the atmospheric dispersion of volcanic ash and gases is crucial for both scientific understanding and hazard mitigation. Estimating Eruption Source Parameters (ESP), such as mass eruption rate, plume height, duration, and particle size distribution and properties, remains challenging due to the complex nature of volcanic processes and measurement uncertainties. This review examines recent advancements in assessing ESPs from the perspective of modeling, evaluating current limitations and potential future improvements. We overview how current models quantify crucial ESPs, either directly from observations or indirectly from proxies or modeling strategies, and address the inherent uncertainties. We identify critical areas needing further research and emphasize the importance of developing more robust and widely applicable methodologies. Finally, we propose innovative strategies to enhance ESPs estimations, ultimately improving volcanic hazard assessments and our understanding of eruption dynamics and their atmospheric interactions.
Abstract Rock physics models link geophysical measurements with subsurface petrophysical properties, such as porosity, mineral composition, and fluid saturation. While originally developed for hydrocarbon exploration, these models are increasingly applied in the near surface for quantitative interpretation of geophysical data. This review focuses on their application to the subsurface component of the critical zone, which extends from soil to the base of weathered bedrock and controls key hydrological, geomorphological, and ecological processes. Its structure and heterogeneity remain difficult to characterize due to limited direct subsurface observations. As a result, critical zone studies of the subsurface have relied on indirect geophysical measurements, which are spatially extensive and are used to interpret structural variations, property heterogeneity, and physical processes. However, geophysical measurements alone do not yield petrophysical properties. Rock physics models combined with geophysical inversion provide a tool to translate geophysical data into subsurface petrophysical properties. In this review, we present a synthesis of rock physics models for the prediction of geophysical properties of unsaturated and saturated porous media, focusing on their formulations and assumptions in near‐surface applications involving seismic, electrical, electromagnetic, and nuclear magnetic resonance methods. We then discuss their integration in geophysical inversion studies for the petrophysical characterization of the critical zone. We assess the capabilities, strengths, and limitations of rock physics models and inversion methods in critical zone applications, illustrated with case studies from the Southern Sierra and Laramie Range, and show how the resulting quantitative estimates of petrophysical properties inform hydrogeological studies and reduce uncertainty in model predictions.
Abstract The United States Magnetotelluric Array (USMTArray) data set, collected in the years 2006–2024, consists of more than 1,700 long‐period magnetotelluric stations covering the entirety of the contiguous United States on a quasi‐regular 70 km grid. Funding across multiple federal agencies was critical to sustaining this effort to its completion. Important components of the project included active guidance and participation from the MT community, the open and timely availability of all data, and the application of consistent instrumentation and robust data processing. Together with parallel advancement in the development of publicly available three‐dimensional (3D) inversion codes, the USMTArray has revitalized the US magnetotelluric community and increased the visibility of magnetotellurics within the Earth‐science community. Taken as a whole, these data are visualized as the National Impedance Map, which, together with a 3D synthesis conductivity model of the nation, reveals the electrical architecture of the contiguous US. USMTArray data are used by researchers worldwide for fundamental and applied studies, including investigations of continental architecture and evolution, estimation of hazards to critical infrastructure due to geomagnetic storms, and assessment of the nation's undiscovered geothermal and mineral resources. We here review the history and development of the project, discuss the challenges and successes in its execution, present the National Impedance Map and synthesis conductivity model, and highlight the breadth of research stemming from this rich data set.
Abstract We evaluate hydrothermal heat loss from 11 volcanic‐arc segments (∼6,000 km of arc length, ∼10% of the global total), motivated by the observation that much magmatic heat ultimately crosses the land surface as heated aqueous fluid. Heat loss takes place by volcanic eruption, geothermal heat conduction to the surface, fumarolic (vapor) discharge, thermal springs, and discharge of groundwater that has been heated by only a few degrees. Heat loss by extrusion of volcanic products ranges from 0.1 to ∼4 MW/km. For some arc segments, the hydrothermal heat loss is dominated by “slightly thermal” springs (maximum ∼10 MW/km arc length) or thermal springs (maximum ∼21 MW/km), but more commonly by hydrothermal steam vents and volcanic fumaroles (maximum ∼7 MW/km). Total hydrothermal heat‐loss rates range from <2.5 MW/km (Southwest Japan, Cascade Range, Northeast Japan, Kurils) to ≥8 MW/km (Ryukyu, Apennines, Taupo Volcanic Zone). We use these hydrothermal heat losses to estimate rates of magma supply, and combine these estimates of magma supply with existing estimates of eruption rates to obtain intrusion:extrusion ratios. Potential causal influences include state‐of‐stress and the abundance of silicic magma in the midcrust. Likely causes of along‐arc variations range from the near‐surface (0–5 km) hydraulic architecture (Cascade Range) to the nature of the subducting plate (Ryukyu vs. the rest of southwest Japan). Inferred intrusion: extrusion ratios are generally between 0.5 and 9. Whole‐arc comparisons between heat‐flow‐based intrusion rates and those based on volatile fluxes and petrologic models are complicated by the wide range of along‐arc behavior and the fact that we sometimes rely on volatile fluxes (e.g., SO 2 ) to help calculate hydrothermal heat losses, so that the data sets are not fully independent. However, reasonable agreement can be demonstrated in some examples of arc subsections.
Abstract Sea ice is situated close to the termini of many outlet glaciers in the Arctic and Antarctic and has the potential to influence their dynamics and, therefore, their contribution to sea level rise. However, the nature, prevalence, and ice‐dynamic significance of sea ice‐glacier interactions remains subject to several open questions. This paper reviews existing research on this critical topic in order to assess the extent to which sea ice influences glacier dynamics, focusing on recent developments while highlighting complexities and uncertainties. Evidence suggests that sea ice can directly influence outlet glacier dynamics through mechanical interactions and/or indirectly via the modulation of ocean‐driven basal melting, either alone or as part of ice mélange. Key knowledge gaps include the influence of mélange‐ocean interactions on glacier melting, and a comprehensive understanding of variations in Antarctic outlet glacier sensitivity to sea‐ice conditions. Current knowledge is skewed toward Arctic outlet glaciers, where the seasonal expansion of sea ice forms a compact mélange which can suppress calving and potentially buttress ice flow. A growing number of studies also suggest that sea ice can influence Antarctic glacier behavior, with observed correspondence between the growth/calving of glacier tongues and ice shelves, and the presence/absence of multi‐year landfast sea ice. However, there is considerable spatial variability in glacier‐dynamic responses to sea‐ice conditions, both within and between the Arctic and Antarctic, predominantly attributed to glacier‐specific factors. Given that recent reductions in sea‐ice extents are likely to contribute to glacier retreat in both polar regions, addressing current knowledge gaps is crucial.
Abstract Material transport and air‐sea coupling dynamics associated with monsoon‐related mesoscale and submesoscale processes in the Indian Ocean significantly modulate biogeochemical cycles, the large‐scale energy balance, and both regional and global climate change. A thorough understanding of mesoscale and submesoscale variability in the Indian Ocean is therefore crucial for elucidating the physical mechanisms governing complex interactions among the ocean, ecosystems, and climate. However, substantial challenges remain in accurate observations, diagnoses, and simulations of such variability in the Indian Ocean, which hinders our ability to quantify their impacts on large‐scale processes. This synthetic paper presents an interdisciplinary review on key characteristics of the unique mesoscale and submesoscale processes in the Indian Ocean. We first synthesize current understanding of the generation of bidirectional energy cascades, feedback mechanisms between mesoscale/submesoscale dynamics and the atmosphere, and physical‐biogeochemical interactions mediated by horizontal and vertical transport induced by mesoscale/submesoscale motions. We then highlight outstanding knowledge gaps and uncertainties related to small‐scale physical properties, and provide recommendations for observational, modeling, and theoretical strategies to advance future research on air‐sea interactions and climate change. This review aims to complement existing global ocean process syntheses. Future directions are outlined with an emphasis on short‐term (e.g., dedicated observational campaigns), long‐term (e.g., improved modeling, climate integration) goals, and the emerging applications of machine learning and artificial intelligence in small‐scale parameterization and data assimilation.
Abstract On behalf of the authors and readers of Reviews of Geophysics (RoG), the American Geophysical Union, and the broader scientific community, the editors wish to wholeheartedly thank those who reviewed manuscripts for RoG in 2025.
Abstract The collisionless shock research started in the late 1950s. Since then, plenty of data have been accumulated due to the large number of missions in the heliosphere, providing in situ measurements of the fields and particles. The quality of these measurements has vastly improved, especially in the last two decades. Much more data is available for analysis than is already analyzed. Theoretical studies received a push in 1966, when it was shown that shocks are formed due to the interplay between the nonlinear steepening and dispersive broadening of the magnetic field profile. At present, it is a common point of view that shocks are essentially shaped by the kinetics of ions. So far, we achieved a good semi‐quantitative understanding of the ion heating in low‐Mach number shocks and the relation of this process to the magnetic profile, and a qualitative understanding of the ion reflection and the nature of the well‐structured magnetic field. Rippled and nonstationary quasi‐perpendicular shocks have been observed, and theory is being developed.
Abstract Air‐sea gas exchange regulates the exchange of climatically important gases between the ocean and the atmosphere, shaping both climate and ocean biogeochemistry. Bubbles beneath the sea surface enhance this exchange by introducing an additional transfer pathway in parallel to the interfacial transfer route. Although the role of bubbles in gas flux has been debated since the 1980s, recent advances in laboratory experiments, field observations, and modeling have provided new insights. Bubble‐mediated gas transfer differs from interfacial transfer in three key ways: (a) it shows strong nonlinearity with wind speed due to its link with wave breaking; (b) it depends on gas solubility because of the finite volume and short lifetime of bubbles; and (c) it shifts the equilibrium toward slight oversaturation through the overpressure of submerged bubbles. These characteristics make bubble‐mediated gas transfer complicated to quantify, and existing observations and models indicate a wide range of bubble contributions to air‐sea carbon dioxide and oxygen exchange. Three critical knowledge gaps are identified: (a) limited understanding of near‐surface (0–1 m) bubble dynamics, including volume flux, size distribution, and evolution, which directly control the solubility and diffusivity dependence of bubble‐mediated gas exchange; (b) the absence of consistent field constraints spanning the full range of gas solubilities; and (c) the lack of knowledge to scale laboratory results to oceanic conditions. Addressing these gaps will require integrated efforts combining near‐surface bubble measurements and simulations, field observations of gas transfer across diverse solubilities using complementary techniques, and improved modeling frameworks.
As climate models become increasingly complex, there is a growing need to comprehensively and systematically assess model performance with respect to observations. Given the increasing number and diversity of climate model simulations in use, the community has moved beyond simple model intercomparison and toward developing methods capable of benchmarking a large number of simulations against a suite of climate metrics. Here, we present a detailed review of evaluation and benchmarking methods and approaches developed in the last decade, focusing primarily on scientific implications for Coupled Model Intercomparison Project (CMIP) simulations and CMIP6 results that contributed to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6). Based on this review, we explain the resulting contemporary philosophy of model benchmarking, and provide clear distinctions and definitions of the terms model verification, process validation, evaluation, and benchmarking. While significant progress has been made in model development based on systematic evaluation and benchmarking efforts, some climate system biases still remain. The development of open‐source community software packages has played a fundamental role in identifying areas of significant model improvement and bias reduction. We review the key features of several software packages that have been commonly used over the past decade to evaluate and benchmark global and regional climate models. Additionally, we discuss best practices for the selection of evaluation and benchmarking metrics and for interpreting the obtained results, the importance of selecting suitable sources of reference data and accurate uncertainty quantification.
Abstract Understanding the coastal zone of the Antarctic Ice Sheet (AIS), where it interacts with the Southern Ocean and warmer air masses, is crucial for predicting Antarctica's influence on the global climate and sea level. This region has multiple tipping mechanisms that could trigger large, rapid, and potentially irreversible changes in the AIS, the Southern Ocean and their global connections in the coming centuries. The AIS remains the largest source of uncertainty in future sea‐level projections. Bed topography beneath the ice shelves and the coastal ice sheet is not yet well documented, and is a major source of this uncertainty. This review assesses current knowledge of the coastal zone and highlights methods to investigate it, including aerogeophysical surveys, ground‐ and ship‐based measurements, satellite observations, and computer modeling. An ensemble analysis of published bed topography data sets identifies significant data gaps and their regional distribution, framed in the context of current ice‐sheet behavior and potential instability. We propose scientific priorities and guidelines for future aerogeophysical surveys, advocating for a comprehensive, coordinated international effort to build a next‐generation data set of Antarctic bed properties. Such an initiative would significantly advance understanding of the role of coastal processes in ice‐sheet dynamics, reducing uncertainties in sea‐level rise projections and improving predictions of future ocean and climate changes.
Saturn's moon Titan exhibits remarkable parallels to the Earth in many geophysical and geological processes not found elsewhere in the solar system at the present day. These include a nitrogen atmosphere with a condensible gas - methane - replacing the Earth's water, leading to an active meteorology with rainfall and surface manifestations including rivers, lakes and seas, and the dissolution of karstic terrain. Other phenomena such as craters, dunes, and tectonic features are found elsewhere - e.g. on Mars and Venus - but their continuing alteration by pluvial, fluvial and lacustrine processes can be studied only on Earth and Titan. Meanwhile Titan also hosts an interior liquid water ocean with similarities to the Earth as well as to ocean worlds such as Europa and Enceladus. Our focus in this review paper is twofold: to describe the geophysical and geological parallels between Earth and Titan, and to evaluate the yet-underexploited possibilities for field analog research to gain new knowledge about these processes. To date, Titan's much colder temperature and different atmospheric and crustal materials have led to a skepticism that useful analogs can be found on Earth. Our conclusion, however, is that a much larger range of useful analog field work is possible and this work will substantially enhance our knowledge of both worlds. Such investigation will supplement the existing sparse data for Titan returned by space missions, will greatly enhance our understanding of such datasets, and will help to provide science impetus and goals for future missions.
The Meiyu-Baiu-Changma (MBC) is a critical rainy season in East Asia. The MBC rainfall is a vital water source but also causes devastating flooding, profoundly impacting agriculture, water resource management, and socio-economy across East Asia. The El Niño–Southern Oscillation (ENSO) plays a critical role in modulating the interannual variability of MBC. The response of MBC to ENSO is, however, complex, nonlinear, and stochastic, influenced by various ENSO characteristics including the phase, intensity, location, and decay pace. This review synthesizes recent advances in understanding the ENSO–MBC linkage, by incorporating existing literature and our new analyses, to elucidate the underlying mechanisms, model performance, and future projections regarding ENSO's impacts on the MBC under climate change. In this review, an increased correlation between ENSO and MBC over past decades is revealed. The two main paths of ENSO impacting the MBC via modulating the anomalous western North Pacific anticyclone, and the changes in the influence of these paths under climate change, are synthesized and analyzed. Seasonal prediction of ENSO-driven MBC anomalies remains challenging, despite the advances of climate models in simulating and predicting the ENSO-related large-scale ocean and atmospheric circulation anomalies. In the future, intensified global warming may lead to a further strengthened impact of ENSO on MBC and increased ENSO-driven MBC extremes. Exploring greenhouse gas forcing's influence, improving high-resolution coupled models, refining representation of key dynamic processes, and utilizing artificial intelligence techniques are essential to advance understanding, simulation, prediction, and climate adaptation strategies related to ENSO-MBC connection.
Mountain glaciers are among the natural systems most vulnerable to climate change. However, their interactions with the atmosphere are complex and not fully understood. These interactions can trigger rapid adjustments and climate feedbacks that either amplify or attenuate atmospheric signals, influencing both glacier response and large-scale atmospheric circulation. Observing this functional coupling in nature is challenging because the key processes occur over a wide range of spatial and temporal scales. However, recent advances in observational techniques and modeling have provided new insights into these interactions. In this review, we summarize the current state of knowledge on glacier-atmosphere interactions in high-mountain regions at different scales, and highlight recent advances in observational and numerical modeling. We also highlight important knowledge gaps and outline future research directions to improve the prediction of glacier change in a warming world.
Frozen soils, including seasonally frozen ground and permafrost, are rapidly changing under a warming climate, with cascading effects on water, energy, and carbon cycles. We synthesize recent advances in the physics, observation, and modeling of frozen-soil hydrology, emphasizing freeze–thaw dynamics, infiltration regimes and preferential flow, groundwater–permafrost interactions (including talik development and advective heat), and resulting shifts in streamflow seasonality. Progress in in situ sensing, geophysics, and remote sensing now resolves unfrozen water, freezing fronts, and active-layer dynamics across scales, while land-surface and tracer-aided hydrological models increasingly represent phase change, macropore bypass, and vapor transport. Thaw-induced activation of subsurface pathways alters recharge and baseflow, influences vegetation and biogeochemistry, and modulates greenhouse-gas emissions. Key uncertainties persist in scaling micro-scale processes, parameterizing ice-impeded hydraulics, and representing abrupt thaw and wetland dynamics. We outline a tiered modeling framework, priority observations, and integration of vegetation–hydrology–carbon processes to improve projections of cold-region water resources and climate feedbacks.
