Geophysical Research Letters

Modeling the short‐term (<50 years) evolution of glaciers is difficult because of issues related to model initialization and data assimilation. However, this timescale is critical, particularly for water resources, natural hazards, and ecology. Using a unique record of satellite remote‐sensing data, combined with a novel optimisation and surface‐forcing‐calculation method within the framework of the deep‐learning‐based Instructed Glacier Model, we are able to ameliorate initialization issues. We thus model the committed evolution of all glaciers in the European Alps up to 2050 using present‐day climate conditions, assuming no future climate change. We find that the resulting committed ice loss exceeds a third of the present‐day ice volume by 2050, with multi‐kilometer frontal retreats for even the largest glaciers. Our results show the importance of modeling ice dynamics to accurately retrieve the ice‐thickness distribution and to predict future mass changes. Thanks to high‐performance GPU processing, we also demonstrate our method's global potential.

Solar radiation‐topography interaction plays an important role in surface energy balance over the Tibetan Plateau (TP). However, the impacts of such interaction over the TP on climate locally and in the Asian regions remain unclear. This study uses the Energy Exascale Earth System Model (E3SM) to evaluate the regional and teleconnected impacts of solar radiation‐topography interaction over the TP. Land‐atmosphere coupled experiments show that topography regulates the surface energy balance, snow processes, and surface climate over the TP across seasons. Accounting for solar radiation‐topography interaction improves E3SM simulation of surface climate. The winter cold bias in air temperature decreases from −4.57 to −3.79 K, and the wet bias in summer precipitation is mitigated in southern TP. The TP's solar radiation‐topography interaction further reduces the South and East Asian summer precipitation biases. Our results demonstrate the topographic roles in regional climate over the TP and highlight its teleconnected climate impacts.

Previous studies suggested that tropical sea surface salinity (SSS) can influence tropical Pacific sea surface temperature (SST) through mixing and entrainment and thus it may be a signal for El Niño‐Southern Oscillation (ENSO) prediction. This paper explores the influence of SSS on ENSO spring predictability barrier (SPB) using an empirical dynamic model ‐ Linear Inverse Model (LIM). By coupling and decoupling SSS in the LIM, we find that tropical Pacific SSS plays a significant role in weakening both Central‐Pacific and Eastern‐Pacific ENSO SPB. The evolution of optimal initial structure also shows the importance of SSS dynamics in ENSO. We found an SSS mode that plays the dominant role in SSS impacting ENSO prediction. By the analysis of lead‐lag correlation, we find that this mode can induce easterlies during the spring, which finally leads to a La Niña‐like SST pattern in the winter through zonal advective and thermocline feedbacks.

Solid organic matter (OM) is a biogeochemically relevant constituent of soils and sediments. It also affects sediments' geophysical properties, but is often overlooked in hydro‐ and biogeophysical approaches for the characterization of the shallow subsurface. Here, we explore the potential of spectral induced polarization (SIP) to delineate OM‐rich zones in the subsurface and provide insights into the mechanisms that drive OM‐polarization using measurements on both field cores and artificial OM‐sand mixtures. Both, field samples and artificial mixtures showed a linear relationship between the total organic carbon (TOC) content and charge storage (imaginary conductivity). The high cation exchange capacity of OM drives the increase in polarization and can help in delineating potentially microbially active OM‐rich zones in cores or field surveys. To avoid misinterpretation of SIP data in unconsolidated media, we strongly suggest quantifying TOC content in sediment samples to accompany the interpretation of field surveys.

Increasing the model resolution is expected to be one way for improving air quality forecasts in urban areas. In this study, we evaluate the model performance in a large city at various resolutions to examine the best resolution for air pollution simulations. The comparison with measurements at a station near the traffic emissions shows the advantage of using high resolutions for capturing the extreme values. The statistical evaluation indicates that the highest model resolution (33 m) provides the best results for NO X concentration distributions near the traffic roads, while the improvement for roadside O 3 with decreasing grid spacing stops at a certain point. The best model performance for the areas with a distance to the pollution sources is with the resolution of 100–300 m, at which the transport errors are equivalent to the emission biases.

In December 2021, Super Typhoon Rai caused significant devastation to the South Philippines and East Malaysia. In the meantime, an unprecedented flood event occurred in Peninsular Malaysia at 2,000 km west of the typhoon's path, causing comparable socioeconomic impacts as Rai. Record‐breaking 3‐day precipitation was received by Peninsular Malaysia during 16–18 December. Based on the storm tracking results, this study identified two mesoscale convective systems (MCSs) that were directly responsible for the flooding. The two MCSs were directly initiated by a tropical depression and sustained by an elongated easterly water vapor corridor originating from the Super Typhoon Rai. The return period and joint frequency analysis of key drivers indicate that the 3‐day downpour was more severe than a “once‐in‐a‐century” event. Historical records suggest such anomalous moisture channel has become more frequent in Southeast Asia, which alarms heightened attention in forecasting winter flood.

Greenhouse gases and aerosols play a major role in controlling global climate change. Greenhouse gases drive a radiative imbalance which warms the ocean, while aerosols cool the ocean. Since 1980, the effective radiation felt by the planet due to anthropogenic aerosols has leveled off, global ocean cooling due to aerosols has decelerated, and greenhouse gas‐driven ocean warming has accelerated. We explore the deceleration of aerosol‐driven ocean cooling by quantifying a time‐ and spatially varying ocean heat uptake efficiency, defined as the change in the rate of global ocean heat storage per degree of cooling surface temperature. In aerosol‐only simulations, ocean heat uptake efficiency has decreased by 43 ± 14% since 1980. The tropics and sub‐tropics have driven this decrease, while the coldest fraction of the ocean continues to sustain cooling and high ocean heat uptake efficiency. Our results identify a growing trend toward less efficient ocean cooling due to aerosols.

In this study, we differentiate wet processes from dry processes in shaping the extratropical thermal stratification during the Last Glacial Maximum. Our findings indicate that even during the dry glacial period the influence of wet processes on thermal stratification cannot be overlooked. The applicability of dry and wet baroclinic adjustment theory strongly depends on the seasonality rather than the glaciation as the warm season is characterized by a weaker meridional temperature gradient and increased precipitation than the cold season. Despite that the baroclinic adjustment theory based on effective static stability can be proficiently applied to all seasons, the classical dry baroclinic adjustment theory may be better suited for use during relatively cold seasons. These findings have important implications for understanding processes governing the extratropical thermal stratification, particularly in the context of cold climate.

Atmosphere‐ocean general circulation models (AOGCMs) struggle to reproduce recently observed sea surface temperature (SST) trend patterns. Here, we quantify the relevance of this SST pattern uncertainty to global‐mean temperature projections through convolving Green's functions with SST pattern scenarios that differ from the ones AOGCMs produce by themselves. We find that future SST pattern uncertainty has a significant impact on projections, such as increasing total model uncertainty by 40% in a high‐emissions scenario by 2085. A reversal of the current cooling trend in the East Pacific over the next few decades could lead to a period of global‐mean warming with a 60% higher rate than currently projected. SST pattern uncertainty works through a destabilization of the shortwave cloud feedback to affect temperature projections. It is critical for climate change impact, adaptation, and mitigation assessments to incorporate this previously unaccounted for uncertainty until we trust the evolution of SST patterns in AOGCMs.

The differential axial rotation of the solid inner core (IC) is suggested by seismic observations and expected from core dynamics models. A rotation of the IC by an angle α takes its degree 2, order 2 topography (peak‐to‐peak amplitude δh ) out of its gravitational alignment with the mantle. This creates a gravity variation of degree 2, order 2 proportional to δh and to α . Here, we use gravity observations from Satellite Laser Ranging, the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On to reconstruct the time‐variable S 2,2 Stokes coefficient. We show that for δh = 90 m, S 2,2 provides upper bounds on α of 0.09°, 0.3°, and 0.4° at periods of ∼4, ∼6, and ∼12 years, respectively. These are overestimates, as our reconstructed S 2,2 signal likely remains polluted by hydrology, although viscous relaxation of the IC can permit larger amplitudes.

The western North Pacific Subtropical High (WNPSH) in boreal summer is a major atmospheric player affecting East Asian climate, but its simulation in state‐of‐the‐art climate models is still largely biased. Here we use a multi‐objective optimization strategy, the Pareto optimality, to incorporate multiple physical constraints in processing multi‐model simulations provided by the Coupled Model Intercomparison Project Phase 6. We aim to improve the simulation of WNPSH by this practice. Sea surface temperatures from three tropical oceanic basins are found highly related to WNPSH, and thus used as constraints. We also present an ameliorated strategy, which takes a subset of the raw Pareto optimality by imposing conditions of smallest errors. Results show that the overestimate of WNPSH is effectively corrected. The two multi‐objective optimization schemes both perform better than the traditional approach, revealing the importance of implementing physically based links in processing multi‐model ensemble simulations.

In many applications of data assimilation, especially when the size of the problem is large, a substantial assumption is made: all variables are well‐described by Gaussian error statistics. This assumption has the advantage of making calculations considerably simpler, but it is often not valid, leading to biases in forecasts or, even worse, unphysical predictions. We propose a simple, but effective, way of replacing this assumption, by making use of transforming functions, while remaining consistent with Bayes' theorem. This method allows the errors to have any value of the skewness and kurtosis, and permits physical bounds for the variables. As such, the error distribution can conform better to the underlying statistics, reducing biases introduced by the Gaussian assumption. We apply this framework to a 3D variational data assimilation method, and find improved performance in a simple atmospheric toy model (Lorenz‐63), compared to an all‐Gaussian technique.

The inversion of remote sensing signatures of internal solitary waves (ISWs) can retrieve dynamic characteristics in the ocean interior. However, the presence of ubiquitous large‐amplitude ISWs poses challenges to the commonly used weakly nonlinear methods for parameter retrieval. Through laboratory experiments, we establish a relationship between surface features and internal characteristics of ISWs by the remote sensing imaging mechanism. The results demonstrate that strong nonlinearity significantly influences the retrieval of ISWs, primarily manifested in the calculation of wave‐induced velocities and the applicability of ISW solutions. A fully nonlinear model Dubreil–Jacotin–Long equation is used in the retrieval and has been tested under different conditions. Mooring observations indicate that the determination of ISW parameters from satellite images is affected by the complexity of in situ stratification, but additional remote sensing information such as surface velocities enables us to perform retrievals even if the real‐time measurement of pycnocline depth is not available.

Seismic anisotropy in the upper mantle reveals geodynamic processes and the tectonic evolution of the Earth. The two most powerful methods, surface wave tomography, and shear-wave splitting observations, cannot investigate the deep local anisotropy with good vertical and lateral resolution, resulting in poor constraints on plate deformation processes of the complex plate boundary beneath the Southern California region. Here, we show that the amplitude ratio of translational displacement and rotation makes it possible to retrieve the local anisotropy in the upper mantle. Azimuthal anisotropy in the asthenosphere is well determined and resolved in lateral and vertical directions. The fast axis retrieved from amplitude observations indicates the local rapid changes in plate deformation and complex pattern of mantle flow, which is compatible with the distributions of horizontal mantle flow illuminated by geodetic measurements, providing new insights on geodynamic processes of the Southern California region.

Plain Language Summary In mixed‐phase clouds, the coexistence of liquid and ice has significant impacts on the cloud lifecycle and radiative properties, but the phase partitioning in mixed‐phase cloud is still not fully understood. In cumulus clouds, one of the major factors controlling the microphysics across cloud edges is the entrainment of dry air into cloud. During the mixing process, the liquid‐ice partitioning is determined by the mixing type (homogeneous or inhomogeneous), the evaporation (growth) of liquid, and sublimation (growth) of ice. Currently, there is a lack of observational evidence for the main mixing mechanism that controls the phase partitioning. In this study, the liquid‐ice mass partitioning across the edge of shallow to moderately deep cumulus clouds are analyzed using airborne in situ measurements. The results show the liquid mass fraction remains similar across the cloud, and inhomogeneous mixing dominates the phase partitioning. The results improve our understanding on the role of entrainment, and are useful in evaluating model simulations.

Plain Language Summary Tectonic events and solar insolation are the two important factors impacting variations of the climate system in the geological past. Regional climate responses to variations in the radiation from the sun over 10⁴–10⁵ years were often magnified or dampened by tectonic events. Cretaceous sedimentary records in East Asia suggest that East Asian climate was influenced by the solar insolation. Geological evidence showed that a mountain range existed along the East Asian coast then. Would this mountain range modulate impacts of solar insolation on East Asian climate? Our modeling results show that the influence of solar insolation on East Asian climate can be amplified by the coastal mountain range, depending on the mountain elevation. When the coastal mountain range is ∼2 km high, the amplification effects become significant. When its altitude reaches ∼4 km, the response of East Asian climate to solar insolation is considerably strengthened, and such a condition is supported by the rhythm induced by the climate variation due to solar insolation archived in the Cretaceous strata in the Songliao Basin. Thus, we speculate that the East Asian coastal mountains might have reached an altitude more than 2 km in the Late Cretaceous.

Plain Language Summary Polar region clouds play a key role in Earth's climate. Knowledge of the cloud phase (i.e., liquid water, ice, or mixed) is important for determining the surface heat budget because the reflection of solar radiation at the cloud top depends on cloud phase. Although the development of numerical climate models allows the investigation of clouds globally, there still is a cloud phase (water or ice) bias in the models. Therefore, an observational study is required to investigate cloud formation environments. During a cruise in the SO by a research ship, ice clouds were observed at relatively high temperatures in the mid‐troposphere at high‐latitudes. Analysis of the trajectory of the air mass at the ice formation height indicated that the air mass had traveled from the surface in the mid‐latitudes to the mid‐troposphere over high‐latitudes. Biogenic material emitted from the ocean under strong wind and high wave conditions was transferred to the air mass near the surface in the mid‐latitudes and eventually reached the mid‐troposphere at the observation point. These results suggest that marine biogenic material transported from the mid‐latitudes influenced ice cloud formation under relatively high temperatures.

Plain Language Summary The natural gas (NG) system is an important source of carbon dioxide (CO2) emissions. Rising U.S. NG production and international energy demand led to a rapid growth of liquefied natural gas (LNG) exports. This makes it increasingly important to assess the CO2 emissions along the LNG supply chain, especially during gas liquefaction at LNG export terminals. However, existing inventories only provide annual/monthly data for some major LNG terminals from operators, which lack measurement‐based in situ validation. Here we introduce a top‐down CO2 measuring method using remote sensing imaging spectroscopy, which can provide an independent third‐party data source above the detection threshold with uniform measuring technology across all infrastructure. Additionally, the independent measurements from this method would help evaluate the magnitude and variation of existing emission inventories. When combined with remote sensing methane detection, it can further monitor the carbon emissions more efficiently along the NG supply chain. This could be achieved by retrieving atmospheric CO2 and CH4 simultaneously from the same remote sensing campaign. This study also shows the mapping and quantification capability of imaging spectroscopy on the plumes with emission rate of 100–3,000 t CO2/hr, implying a broader application potential in CO2 top‐down detection.

Field Line Resonances (FLRs) are a critical component in Earth's magnetospheric dynamics, associated with the transfer of energy between Ultra Low Frequency waves and local plasma populations. In this study we investigate how the polarisation of FLRs are impacted by cold plasma density distributions during geomagnetic storms. We present an analysis of Van Allen Probe A observations, where the spacecraft traversed a storm time plasmaspheric plume. We show that the polarisation of the FLR is significantly altered at the sharp azimuthal density gradient of the plume boundary, where the polarisation is intermediate with significant poloidal and toroidal components. These signatures are consistent with magnetohydrodynamic modeling results, providing the first observational evidence of a 3D FLR associated with a plume in Earth's magnetosphere. These results demonstrate the importance of cold plasma in controlling wave dynamics in the magnetosphere, and have important implications for wave‐particle interactions at a range of energies.

Plain Language Summary California winter weather can alternate between very wet conditions from atmospheric rivers making landfall along the Pacific coast to hot, dry, and windy conditions brought by Santa Ana winds blowing in from the Southwest interior. Atmospheric rivers are important for water resources while also causing flooding, whereas Santa Ana winds are often associated with wildfire, especially following prolonged dry periods. Preparing for these types of weather events is important for managing resources and protecting life and property, yet reliable forecasts beyond about 7–10 days remain a challenge. We have developed a new prediction system that combines information about approaching atmospheric weather patterns from weather forecast models along with historical information relating those patterns to impacts over California to predict the likelihood of impactful weather at 1–4 weeks lead time. By extending the window of opportunity to take management action, this new approach should aid in resource and emergency planning in water, land, and fire sectors as well as protecting residents through improved warning systems.

Seasonal‐to‐decadal climate prediction is crucial for decision‐making in a number of industries, but forecasts on these timescales have limited skill. Here, we develop a data‐driven method for selecting optimal analogs for seasonal‐to‐decadal analog forecasting. Using an interpretable neural network, we learn a spatially‐weighted mask that quantifies how important each grid point is for determining whether two climate states will evolve similarly. We show that analogs selected using this weighted mask provide more skillful forecasts than analogs that are selected using traditional spatially‐uniform methods. This method is tested on two prediction problems using the Max Planck Institute for Meteorology Grand Ensemble: multi‐year prediction of North Atlantic sea surface temperatures, and seasonal prediction of El Niño Southern Oscillation. This work demonstrates a methodical approach to selecting analogs that may be useful for improving seasonal‐to‐decadal forecasts and understanding their sources of skill.

Plain Language Summary Current state‐of‐the‐art climate models do not reproduce the total area of Antarctic sea ice and its trends as observed. This impedes the use of climate models to understand changes in Antarctic sea ice over the past decades and to project its future. Separating how much of the simulated sea ice change is due to freezing and melting, and how much is due to ice transport allows us to identify physical causes for model biases, which helps us to optimize models. We examined the climate models that have simulated near‐realistic sea ice areas between 1991 and 2009 and found significant improvements in their simulation of sea ice processes in the latest generation of models compared to the previous generation, although there is still much room for further improvement. As sea ice thickness and velocity interact, a key limitation of the state‐of‐the‐art Antarctic sea ice simulation may stem from the general underestimation of ice thickness. This could be a critical issue to be targeted on the way toward increasingly skillful climate projections.

Plain Language Summary The Deccan volcanism occurred around 65 Ma ago when India and Seychelles, moving northward, interacted with the Reunion plume, leading to increased temperature and hence melting at the upper mantle. The buoyant magma moved upward and ponded toward the crust‐mantle boundary. When the overlying crust failed due to high overpressure and/or magma buoyancy, the magma ascended via dikes and assimilated into a shallow crust. The process is expected to produce significant crust and upper mantle modifications due to increased heat transfer and chemical transformation during magma ascent. Existing geophysical knowledge of the Deccan traps does not provide the signature of a magma ascent path and evidence for crustal transformations. Using data from a recent 160 km‐long broadband seismological experiment, we construct a detailed model of the crust and uppermost mantle, showing a complete magma plumbing system. The result shows evidence for lithospheric thinning and well‐preserved deformation in the shallow mantle in the form of sulfide melt, magma ponding at the crust‐mantle boundary beneath the coastal basin, an extensive low‐velocity layer in the upper/mid crust possibly representing the horizontally elongated frozen magma reservoir, and a densified high‐velocity layer in the shallow crust (4–8 km depth) representing basaltic mafic intrusions.

Plain Language Summary The large‐scale overturning circulation in the tropical Pacific known as the Pacific Walker circulation is the heart of the general circulation of the atmosphere. Most of the future climate projections by climate models suggest that the Walker circulation weakens with surface warming. However, observations show that the circulation has strengthened over the past decades despite ongoing global warming. We show, using atmosphere model simulations for 1979–2013 that the Walker circulation strengthening is well reproduced and it weakens when a hypothetical uniform surface warming trend was imposed on the sea surface temperature (SST) data that force the model. The weakening of the Walker circulation occurs at a rate of about 8% per degree warming, but this effect cannot overcome the SST pattern effect that intensifies the circulation. Further attribution simulations show that the past strengthening is explained directly by the SST warming pattern in the narrow equatorial band, about one‐third of which is induced by the warming of the Indian Ocean.

Plain Language Summary Understanding the subduction process and how the mantle flows is pivotal in understanding the planetary evolution of Earth. Yet, several subduction characteristics remain unsolved, and the angle of plate subduction, which is often categorized into <30° (shallow), ∼30–35° (normal), >35° (steep), is one of those. Subduction of an oceanic ridge on a plate has been proposed as a cause of a shallow subduction angle since the thick crust of the ridge is less dense than the surrounding mantle. However, normal angles have been observed in some cases where oceanic ridges are subducting. In this study, we compare the Nazca Ridge and the Iquique Ridge, on the Nazca Plate subducting beneath South America. The subduction angles of the Nazca and Iquique Ridges are shallow and normal, respectively. When we incorporate directional variations in seismic wave velocities, which are produced by mantle flow, in seismic tomographic imaging, we find that the subducting oceanic ridge may not be a primary factor producing shallow angle subduction. Instead, the warm mantle beneath the Nazca Ridge may provide the buoyancy to support the Nazca Plate. Comparably, since the mantle beneath the Iquique Ridge is not warm, the subduction angle would stay normal.