Solving the problems presented by climate change depends on geospatial technology in great measure. Through shifting pest and disease dynamics, increasing frequency of extreme weather events, and modifying growth circumstances, climate change aggravates problems with plant health. For example, remote sensing data and satellite-based climate models help one to forecast how variations in temperature and precipitation patterns can influence the distribution of plant diseases and pests. This predicting makes proactive adaption tactics possible (Beddington et al., 2012). Geospatial instruments also allow one to track crop performance under the influence of climateinduced stresses including heat waves and drenches. This tracking helps to create strong farming methods. Geospatial technology helps stakeholders to carry focused actions that preserve plant health and guarantee the stability of food systems in a changing environment by offering thorough understanding of how climate interacts with plant life. This capacity is particularly important in sensitive areas where smallholder farmers depend on agriculture for their food security and means of income.

Common representations of seismic faults often fall into two categories. Either the model focuses on clean rough surfaces in sliding contact, or the model focuses on the gouge production and shearing between two smooth surfaces. In this work, we wish to reconcile these two main models by using tribological tools and concepts, in order to pave the way for a more accurate model of geometrically complex faults. A pin-on-disc experimental device is employed to investigate the response of a single asperity to shear sliding, in presence of granular gouge. Co-seismic conditions are applied on Carrara marble samples (contact stress, contact area, sliding velocity) and real time acquisition sensors as well as post-mortem analyses on the contact surfaces provide qualitative and quantitative information on the frictional behaviour of the down-scaled lab fault. The results for low sliding velocity (0,01 m.s-1) tests shows a complex behaviour. Three regimes are underlined, which highlights the interplay between granular gouge and asperities. The last regime is seen as a steady state with rough contact surfaces and the presence of a granular gouge layer. This observation leads to the conclusion that in a model for geometrically complex fault, granular gouge and asperities are not self-excluding and should be considered together. This work is complemented by a numerical model presented in a companion paper.

The Canadian Lake Ice Model has been distributed and adapted to run at a fine spatial resolution (~50 m) for simulating lake ice thickness and phenology on small to medium-sized lakes for this study. The model’s capabilities are extended to simulate the spatial variability of Lake ice thickness (LIT), Ice Cover Duration (ICD), and Lake Ice Phenology (LIP) across 500 predominantly small to medium-sized lakes in the North Slave Region (NSR) of the Northwest Territories (NWT), Canada, from 1984 to 2022. The model utilizes 30 m grid lake surface temperature (LST) data derived from the North Slave LST dataset, along with climate inputs from the European Centre for Medium-Range Weather Forecasts Reanalysis v5 and ECMWF (ERA5), including wind speed, mean air temperature, relative humidity, snow depth, and cloud cover. These inputs provide surface fluxes to the model, driving its unsteady heat equation to produce daily LIT, annual ICD, and annual freeze-up and break-up dates on a ~50 m grid. Validation against in-situ measurements showed a root mean square deviation of 2.7 cm to 7 cm for LIT. Trend analysis revealed a significant decline in LIT (-0.26 cm/year to -0.10 cm/year) and ICD (-0.40 day/year to -0.15 day/year) over the study period. The findings highlight the sensitivity of LIT and freeze-up dates to lake morphometry. In contrast, ice break-up dates are primarily influenced by geographic factors such as latitude and elevation. The distributed model comprehensively assesses lake ice variability and trends across 500 lakes under changing climate and weather conditions.

Hydro-morphodynamic patterns in open channel confluences have been extensively studied, but discrepancies exist between flume experiments and field investigations. A standard analog physical model of river confluences is proposed, featuring smooth downstream junction, a large width-to-depth ratio and downstream widening. Flume experiment is conducted on this model to study the hydrodynamic and morphological features within the confluence, which are compared with previous studies. Results show that hydrodynamic and morphological features align with natural confluences but differ from previous flume experiment findings. For instance, typical features in previous flume experiments such as separation zones, and junction corner scour holes are absent in the proposed standard analog model. Results also suggest that strong turbulent kinetic energy and high shear stress within the shear layer are primarily responsible for the formation of mid-channel scour hole. The findings underscore the necessity of employing the standard analog model in future flume experiments related to confluences.

Onset of reconnection in the magnetotail requires its current sheet (CS) to thin down to the thermal ion gyroradius (or thinner) to demagnetize ions (or even electrons) and to provide their Landau dissipation. However, in isotropic plasma models of the tail the ion-scale CSs inflate too rapidly with the distance from Earth to remain ion-scale beyond 20 Earth’s radii, where most X-lines are observed. A key to solving this problem was recently found due to the discovery of “overstretched” thin CSs (OTCSs): If an ion-scale CS is embedded into a much thicker CS with even a weak field-aligned ion anisotropy, its current density iso-contours can be stretched far beyond the magnetic field lines. Here we investigate onset of reconnection in OTCS with their scales and features closer to the observed geometry and evolution of Earth’s magnetotail: extension beyond 100 ion inertial lengths, magnetic flux accumulation, dipole field effects and weak external driving. 2-D particle-in-cell (PIC) simulations with open boundaries show that OTCSs help explain the observed X-line location in the magnetotail. The reconnection electric field strongly exceeds both the external driving field and the slow convection electric field caused by the latter. The magnetic topology change (onset of reconnection proper) is preceded by divergent plasma flows suggesting that the latter are produced by the ion tearing plasma motions. OTCS are also shown to form in isotropic CS after an even shorter driving period, but their transient nature may question universality of this onset scenario.

Gullies are actively changing landforms on planet Mars. The prevailing hypothesis, supported by a suite of different studies, states that present-day activity in these gullies is caused by fluidised granular flows driven by the sublimation of seasonal CO2 ice. However, the long-term formation process of gully landscapes is a contentious issue as water-driven debris-flow processes could easily explain erosion. In contrast, we do not know if CO2-driven granular flows can cause a significant amount of erosion. In this study, we conducted flume experiments investigating the flow dynamics and erosion capacity of CO2-driven granular flows under different substrate and flow settings. Our experiments show that CO2-driven granular flows under Martian conditions are efficient erosive agents, which can erode and entrain large volumes of unconsolidated material in various environmental (i.e. substrate and flow) settings. In general, erosion and entrainment enhance the mobility of CO2-driven flows. However, the frost and thermal conditions of the slopes and the flow composition determine the erosion efficiency of these flows. Finally, based on terrestrial debris-flow erosion theory we estimate that collisional forces at the base of CO2-driven flows can cause erosion of the underlying bedrock or permafrost.

Mesoscale sea surface temperature (SST) variability influences the marine atmosphere boundary layer (MABL), affecting near-surface winds and turbulent heat fluxes. This study examines precipitation response to mesoscale SST forcing using satellite observations, ERA5 reanalysis, and high- and low-resolution climate models. The results show that high-resolution models produce a precipitation response to mesoscale SST consistent with satellite observations and ERA5. However, partitioning ERA5 and model precipitation into resolved and parameterized convective components reveals that even in high-resolution models, the mesoscale SST-precipitation relationship remains highly dependent on convective parameterization. Further analysis of ERA5 and high-resolution simulations shows a vertical velocity response extending to 500 hPa, suggesting a potential remote influence of mesoscale SST on atmospheric circulation. However, the reliance on convective schemes introduces uncertainties about whether high-resolution models accurately capture these effects.

A robust estimation of how heat stress is changing worldwide is complicated by the variety of heat stress metrics in use. This study compares heat stress changes between 1979–2000 and 2001–2023 calculated from five commonly used metrics based on ERA5 reanalysis. We identify regions where all metrics indicate significant increases in heat stress, underscoring the need for urgent adaptation efforts. Conversely, we also find regions where metrics disagree, even on the direction of change. Substantial inter-metric spread in population heat exposure exceeds the spread from reanalysis choices and is comparable to the spread across an ensemble of CMIP6 climate models. Detailed local examinations suggest these inter-metric discrepancies arise from differing temperature-humidity relative weighting across metrics. Our findings highlight metric choice as a significant source of uncertainty in heat stress projections and emphasize the need for a better understanding of the suitability of different metrics for specific climate regimes and impacts.

The Alaska Peninsula section of the Alaska-Aleutian subduction zone shows significant along-strike variations in seismic activity and inter-seismic plate coupling. This region experienced the 2020 Mw 7.8 Simeonof megathrust, Mw 7.6 Sand Point strike-slip, and 2021 Mw 8.2 Chignik megathrust earthquakes. This study, utilizing deep-learning techniques, presents a high-precision earthquake catalog, providing insights into background seismicity, aftershocks, and slab geometry. An abrupt change in the slab dip angle at 30--40 km depths in the Shumagin segment acted as a barrier to the Simeonof and Sand Point earthquake ruptures. The Simeonof event triggered more aftershocks in the overriding plate than the Chignik event, suggesting the overriding plate is more deformed and hydrated in the Shumagin segment. The Sand Point earthquake triggered numerous aftershocks in the overriding plate, delineating a fault in the overriding plate with similar geometry as the intra-slab mainshock fault, but activated around seven days after the mainshock.

We investigate the internal structure of the Mantle Transition Zone (MTZ) beneath the contiguous U.S. by mapping the 520 km discontinuity (d520) depth and relative amplitude of seismic phases associated with the 520-km, 410-km, and 660-km discontinuities. We analyze short-period reflected waves between 3-10 s from MTZ discontinuities extracted from seismic noise correlations. Our results reveal notable lateral variations in d520 depths, with greater depths mostly found in the western U.S., likely indicating warmer upper MTZ in this region. Analysis of relative phase amplitude between MTZ interfaces highlights strong d520 reflection phase across the central U.S., supporting previous studies that report high velocity contrasts and elevated olivine content. In contrast, the eastern U.S. shows weaker d520 reflection phase, which may be attributed to gradual velocity transition and lower water content. MTZ composition also likely varies across the U.S., with potential basalt accumulation in the southwest due to past subduction events.

The source process of the 2024 Mw 7.1 Hyuganada, Japan, earthquake was investigated using waveform inversion of the onshore strong motion records obtained from the region west of the source area. The main fault rupture occurred 6–12 km south of the hypocenter, with a maximum slip of 4.2 m. The rupture propagated unilaterally in the southern direction and stopped after approximately 12 s. Before and after the mainshock, low seismic activities were detected in the main-slip region. The rate of slow slip events was lower in the main-slip region than in the peripheral region, indicating that the main-slip region was more strongly coupled than the peripheral region before the mainshock. The N-net seafloor seismograms of the mainshock with a frequency of ~0.05 Hz recorded east of the source area were reproduced for several stations using the empirical Green’s function approach based on the estimated source process data.

Ice nucleating particles (INP) capable of nucleating ice crystals via immersion freezing at temperatures above approximately -35oC may strongly influence cloud glaciation, with implications for global precipitation and climate feedback. In addition to mineral and soil dust and marine organics, laboratory and field measurements suggest biomass-burning aerosols (BBA) can act as immersion-mode INP between around -30oC and -15oC. However, the contribution of BBA to the global INP budget remains poorly understood. Large uncertainties mainly stem from poor knowledge of which fuels yield INPs and global coverage of those fuel types. Further uncertainty arises from unknown size distributions of the particles that contain minerals that act as ice nucleants. However, with some understanding of these uncertainties from sensitivity studies, the relative importance of ice nucleation activity of BBA compared to, for example, mineral dust and marine organics, can be quantified. In this work, we investigate the potential global importance of BBA as INP using a global aerosol-climate model, specifically the UK Met Office Unified Model (UM). We evaluate the model using field campaigns over four different regions. We examine potential uncertainties in particle size and fuel type on BBA-based INP concentrations. Averaged over June-September, BBA INP accounts for more than half of annual average total INP in 7% of model grid cells with temperatures between -30oC and -20oC. Our simulations suggest INP concentrations from BBA may be at least as important as mineral dust and marine INP over large regions of the atmosphere in seasons when biomass burning is frequent.

Planetary boundary layer (PBL) structure over the ocean and the model capability to simulate such structure are less well-understood than their counterparts over land. In this study, observations and WRF simulations are examined to study the boundary layer structure over the Southern Ocean, focusing on the coupling between the oceanic boundary layer and the cloud layer above. Based on the lower tropospheric vertical profiles and cross-sections, three cloud-boundary layer coupling modes are identified including a coupled mode with a weak positive surface heat flux (type 1), and two decoupled modes in the presence of either a negative surface heat flux driving a shallow stable boundary layer (type 2) or a strong positive surface heat flux (type 3). Numerical simulations are conducted for representative cases of each mode using the conventional YSU PBL scheme without and with the cloud-induced top-down mixing option (referred to as YSUtopdown), as well as the MYNN and the MYNN eddy-diffusivity mass-flux scheme (MYNN-EDMF) that adopts a holistic treatment of mixed-layer thermals and shallow convective clouds. The MYNN-EDMF scheme offers the best representation of the decoupled type 3 mode where its capability to simulate different vertical extents of local mixing and nonlocal mass flux is found to be essential. Two key parameters in MYNN-EDMF dictating shallow cloud formation are also identified. The YSUtopdown scheme develops deeper boundary layer than the YSU scheme and exhibits more consistency with observations for the coupled type 1 mode. For the decoupled type 2 mode, all four schemes perform similarly well.

Maud Rise, is a seamount in the Southern Weddell Sea where open-ocean polynyas occasionally occur. Polynyas are large openings in sea ice that form in winter in association with deep ocean convection. In winter, freezing waters are found in the mixed layer and warmer deep waters lie below the pycnocline. Destratification of the water column enables the mixing of heat into the mixed layer and is required for the formation and sustenance of polynyas. Open-ocean polynyas are rare formations that can disrupt the conventional abyssal overturning circulation pathways and affect the heat and carbon budget of the region. Maud Rise lies in the path of the eastern limb of the Weddell Gyre, which is the main source of salt and heat in this region. We use satellite-based altimetry and ocean state estimates to study how variability in the eastern Weddell Gyre inflow impacted stratification around Maud Rise via the transport of salt anomalies. Salinity predominantly controls stratification in polar waters. We find that reduction in the eastern inflow induced sub-surface freshening in the years leading to the most recent polynya in 2017. Remotely advected sub-surface salinity anomalies control the region's stratification on interannual time scales, and thus influence how much heat and salt is stored below the pycnocline. The inflowing limb of the eastern Weddell Gyre responds to tropical Pacific and Southern Ocean climate variability via atmospheric teleconnections.

A document by Douglas Johnson. Click on the document to view its contents.

In this study, we developed and implemented a deep learning program to classify the suitability of regions for landing on the Moon's south pole, utilizing data from NASA's Lunar Reconnaissance Orbiter (LRO), launched in 2009. The LRO mission, which included the creation of a three-dimensional map of the Moon using the Lunar Orbiter Laser Altimeter (LOLA) instrument, and high-resolution images from the Lunar Reconnaissance Orbiter Camera (LROC), enabled detailed mapping of lunar topography, with a particular focus on craters in the south polar region. Images with a resolution of 1 - 20 meters per pixel were analyzed and characterized using a Convolutional Neural Network (CNN) to identify terrain features that could indicate safe landing sites. The binary analysis classified the areas as either suitable or unsuitable for landing, considering risks such as explosion or overturning due to the terrain. This approach enhances the identification of secure landing sites, supporting future lunar missions like Artemis 3.

In the inner heliosphere, stream interaction regions (SIR), where fast and slow solar wind streams meet, modulate the intensity of galactic cosmic rays (GCR) on the timescale of a few days. We perform a superposed epoch analysis (SEA) of solar wind, magnetic field, and high-energy particle count rate data from the Advanced Composition Explorer (ACE) to calculate the average bulk and turbulent features of SIRs associated with strong GCR depressions, as well as a mean percentage change profile for the galactic proton flux during these events. In particular, we split the power of nearly-incompressible magnetic turbulence throughout the SIR epoch into the common slab and 2D modes, since these contribute to energetic particle diffusion in different directions relative to the background, time-averaged field. We use the SEA results to compute parallel and perpendicular diffusion coefficients for GCRs during the passage of an average SIR and discuss our findings in the context of the particle observations and prior research. Our results suggest that GCR depletions through an SIR are primarily driven by a sharp decrease in the diffusion coefficients.

Terrestrial ecosystems mitigate CO2 accumulation in the atmosphere by annually absorbing ~30% of anthropogenic emissions. The degrees to which CO2 and climate drive this absorption are uncertain, which presents a challenge for future planning around carbon mitigation scenarios. To reduce this knowledge gap, we use a Bayesian model–data integration framework (CARDAMOM) to build and analyze a global terrestrial biosphere reanalysis that optimally reconciles multiple lines of Earth Observations with mechanistic model processes. The Earth observations informing the model dynamics include satellite- and inventory-based constraints on distributions and change in terrestrial C storage (e.g., live biomass, soil organic C, and net biosphere exchange of CO2) and mechanisms of that change (e.g., photosynthesis, deforestation, water storage anomalies, or fire). We find that the impact of 2001–2021’s atmospheric CO2 increase on terrestrial C storage (+38 PgC) opposes and far outweighs the impact of climate trends over over the same period ($-$8.2 PgC). Globally, CO2-induced carbon gains occurred primarily in living biomass pools, while climate-induced losses occurred primarily in dead organic C pools, but relative gains and losses vary regionally. The fact that live biomass and dead organic C exhibit distinct and often opposing responses indicates that mechanistically resolving ecosystem function underlying the terrestrial C cycle’s emergent behavior is crucial for estimating the strength and resilience of the land C sink over the coming decades.