We examine the geostrophic pathways of Pacific and Atlantic Waters along isopycnal surfaces of the Arctic Ocean from Montgomery potentials using two observation-based climatologies: the World Ocean Atlas (WOA) and the Monthly Isopycnal & Mixed-layer Ocean Climatology (MIMOC). The decadal mean circulation (2005-2017) shows an anticyclonic circulation for both the summer Pacific Waters (sPW) and winter Pacific Waters (wPW, although somewhat weaker) in the Canada Basin with subduction along the Chukchi plateau for both water masses. On the wPW layer, the diagnostics also highlight a year-long persistent flow from Herald Canyon on Chukchi Shelf to the Canadian Arctic Archipelago around the Canada Basin. Outflows are found at Nares and Fram Sraits at the density of sPW and wPW. These outflowing waters, previously reported as Pacific Waters, are found here to originate from the Eurasian shelf. Deeper, the Atlantic Waters (AW) flow anticyclonically around Northwind Ridge and cyclonically along the Alaskan shelfbreak forming a boundary current. The subduction of warm water along the Alaskan and Chukchi shelves is found to occur in summer on the sPW isopycnal layer, thus contributing to transferring heat into the center of the gyre. Yet, an advection of virtual Lagrangian particles from Pt. Barrow suggests that processes operating on timescales shorter than a month or at interannual time scales are the main contributors to the heat build up observed over the past two decades. This analysis supports the hypothesis that high frequency processes are key in shaping the subsurface heat reservoir of the Canada Basin.

We investigate the relationship between the seismogenic behavior of global megathrusts and various subduction parameters. We performed a parametric approach by implementing three decision tree-based Machine Learning (ML) algorithms to predict the b-value of the frequency-magnitude relationship of seismicity as a non-linear combination of subduction variables (subducting plate age and roughness, slab dip, convergence speed and azimuth, distance to closest ridge and plate boundary). Using the Shapley Additive exPlanations (SHAP) to interpret the ML results, we observe that plate age and subduction dip are the most influential variables. The results suggest that older, shallow-dipping plates contribute to low b-values, indicating higher megathrust stress. This pattern is attributed to the higher rigidity of older plates, increasing flexural strength, and generating a shallow penetration angle, increasing the frictional interplate area and intensifying the megathrust stress. These findings offer new insights into the non-linear complexity of seismic behaviour at global scale.

A document by Yasuo YABE. Click on the document to view its contents.

A document by Manon Gévaudan. Click on the document to view its contents.

Aquaplanet experiments are used to investigate the physical convergence of a Global Storm-Resolving model (GSRM) under successive, two-fold horizontal grid spacing refinements from 160 km to 1.25 km. A methodology based on the Richardson extrapolation method is used with the aquaplanet hemispherical symmetry to quantify convergence. We use the symmetrical and anti-symmetrical solution components to estimate the asymptotic convergence pattern, the asymptotic estimate, and sampling uncertainty. Based on successive refinements, different climate statistics are explored to evaluate if they enter into a convergent regime and, if so, what their convergent value is. Our analysis focuses on global mean statistics related to the general circulation and aspects that influence the climate: the meridional overturning circulation, the tropical structure (the Inter-Tropical Convergence Zone (ITCZ), and the zonal mean thermodynamic state), and the energy and water budget. Our results show a kilometer and hectometer-scale horizontal grid spacing requirement for physical convergence of the meridional overturning circulation structure and global mean statistics. Distinctively, the tropical structure is estimated to be very near their asymptotic values at km-scale grid spacing, but the circulation intensity appears to converge more slowly, as do the storm track and jet-stream. As we increase the horizontal grid spacing, a better representation of clouds and zonal distribution of water vapor drives convergence in the energy and water budget. We conclude that simulations with a resolution of 2.5 km pose a great candidate for multi-decadal simulations within a compromise of the meridional overturning circulation structure convergence and intensity.

A document by Liam Cassidy. Click on the document to view its contents.

The effect of changes in cloudiness parameterization on the equilibrium climate sensitivity (ECS) of the climate model INM-CM4-8 is investigated. The reasonable changes in parameterization of cloudiness amount only lead to variability of ECS in INM-CM4-8 in the interval of 1.8 - 4.1 K, that is more than a half of the interval for CMIP6 models. Two mechanisms are mainly responsible to increase of ECS. The first one is increase of cloudiness dissipation in warmer climate because of increased water vapor deficit in non-cloud fraction of a cell. The second one is decrease atmospheric boundary layer cloudiness generation in warmer climate. The amplitude of natural climate variability change with respect to ECS change was studied. Increase of ECS doesn’t lead to increase of the value of natural climate variability at most time and spatial scales.

A document by Natalie Nelson. Click on the document to view its contents.

First part of the paper is devoted to explanation of unusual WSW-ENE position of High Atlas belt. Explanation is given by permanent action of tides, which create folding of this belt and its permanent uplift up to high over 4000 m. Tidal origin of Marrakesh earthquake 2023 is proven by maximum Moon declination 27° 31.

Linear dipole type DC electric field sensor was newly developed, and continuous observations by means of 3-D sensor system composed of three sensors installed orthogonally with each other have been conducting since 2017. However, their measured intensities have been remained uncertain, because they could not be calibrated from a reason that, at present, there dose not exist any facility for making uniform electric field in a wide area. So, in order to establish a method for obtaining reliable electric field intensity from output voltage of the sensor system, fundamental function of the sensor system has been examined. Since resistor R which is to be connected to input terminals of differential pre-amplifier is a key parameter in the sensor system, it was needed to examine a characteristic curve of the output voltage as a function of R. For this purpose, simultaneous observations of natural electric fields were conducted by means of plural sensor systems installed in parallel. From obtained characteristic curve, an optimum value of R could be decided, and a formula showing a relation between reliable electric field intensity and output voltage of the sensor system was found. Validity of the formula has been verified by results of simultaneous observations of a lightning pulse by means of two vertical sensor systems whose element lengths were different. Their results have shown same electric field intensity. As the result, the linear dipole type DC electric field sensor system with the formula has been perfectly established as a practically useful sensor system.

Use this document to write your peer review. Replace this text with your peer review report. You can use Authorea's editor to include text, figures, equations, and citations. Peer review reports generally include: a summary of the manuscript's claims and findings, its relevance for the journal, an overview of the manuscript’s strengths and weaknesses, a discussion of areas that need improvement (major issues and minor issues), and your recommendation for acceptance or rejection. When you are finished writing, click on Submit Review Report.  

A document by Emily Zawacki. Click on the document to view its contents.

A tidal mixing front in the southern North Sea is analyzed for its spatial and temporal distribution of the near-surface horizontal divergence and vertical velocity to understand the evolution of a tidal mixing front in a highly dynamic, semidiurnal tidal-influenced shallow shelf sea. A multi-sensor synoptic data set with a focus on the upper 10 m consisting of surface drifters, a drifting sensor chain, and an ADCP resolving length scales of , as well as subsequent CTD measurements, revealed a tidal mixing front that consistedof two separate tidal mixing density filaments that differed in 3D structure. In all observations, divergence developed with the accelerating tidal current and convergence evolved out of the deceleration of the tidal current. Vertical velocities ranged between , with divergence coupled to upwelling and convergence to downwelling. For the first tidal mixing density filament, convergence was limited to the upper 4 meters and was suppressed by the uplift of dense water. For the second filament, convergence was built from the bottom, propagating throughout the water column. These observations demonstrate that tidal mixing fronts play a significant role in promoting vertical transport within the water column.

Fine particulate matter (PM2.5), with a diameter of 2.5 micrometers or smaller, presents a significant health risk due to its ability to penetrate deeply into the lungs and enter the bloodstream. Conventional exposure assessments often overlook critical factors such as individual movement patterns and spatial variability in pollution, leading to less accurate exposure estimates and masking disparities in vulnerable populations. This study introduces an innovative spatial-temporal agent-based modeling (ABM) approach to capture detailed exposure dynamics within urban airsheds, using the Pleasant Run Airshed in Indianapolis, IN, as a case study. By integrating data from 23 PM2.5 sensors, meteorological variables, and land use data, we modeled PM2.5 concentrations over 50 weeks and simulated exposure for 10,000 virtual agents grouped by susceptibility, reflecting varying levels of health vulnerability. Our results reveal marked exposure disparities across sociodemographic groups, with high-susceptibility agents experiencing significantly greater health impacts. The spatial analysis identifies high-exposure zones near industrial areas and transportation corridors, underscoring the urgent need for targeted environmental justice interventions. This study demonstrates ABM’s potential to capture spatial-temporal exposure variability and illuminate inequities in pollutant exposure, offering critical insights for public health policy to reduce environmental health risks. Future research should explore combining ABM with multi-pollutant analysis to comprehensively address complex urban air quality challenges and promote equitable health outcomes.

Leigh Stadlera, Songo Anele Benyaa, Gina Ziervogela, Petra Holdena

Recent evidence has revealed that strong coupling between the lower atmosphere and the thermosphere ($>$100 km) occurs on intra-seasonal (IS) timescales ($\sim$30-90 days). The Madden-Julian Oscillation (MJO), a primary source of IS variability in tropical tropospheric convection and circulation, can influence the generation and propagation characteristics of atmospheric tides and has been proposed as a significant driver of thermospheric IS oscillations (ISOs). Despite this progress, the limited availability of satellite observations in the ‘thermospheric gap’ region (ca. 100-300 km) and the inability of numerical models to accurately characterize this region have hindered a comprehensive understanding of this connection and the fundamental processes involved. In this study, an Ionospheric Connection Explorer (ICON)-adapted version of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), incorporating lower boundary tides derived from MIGHTI observations, is utilized to characterize and quantify the impact of the upward-propagating tidal spectrum on thermospheric ISOs and to elucidate connections to the MJO. Thermospheric zonal and diurnal mean zonal winds are shown to exhibit prominent ($\sim$20 m/s) tidally-driven ISOs throughout 2020-2021, largest at low latitudes ($\pm$30$^\circ$) near $\sim$110-150 km altitude. Correlation analyses demonstrate a robust (r$>$0.6) connection between the thermospheric ISOs, tides, and the tropospheric MJO, moreover, Hovm\”oller diagrams indicate eastward tidal propagation consistent with the MJO and concurrent SABER observations. This study demonstrates that vertically propagating tides play a crucial role in linking IS variability from the lower atmosphere to the thermosphere, with the MJO identified as a primary contributor to this significant whole-atmosphere teleconnection.

Geomorphological studies are significant for understanding fault dynamics and assessing their seismic hazard, particularly in offshore regions where direct observation is limited. The North-South Faults (NSF), analyzed using ultra-high-resolution bathymetric data, reveal a complex seafloor expression characterized by multiple fault scarps and pockmarks. Through geometric analysis of morphotectonic parameters along the fault segments, we identified patterns of fault growth and segmentation, with a particular focus on transfer zones and intricate fault linkages. Cumulative vertical displacement varies from centimeters to decameters, with the largest displacements typically observed in the northern sections of the fault segments. These height variations, along with segment lengths and linkage patterns, indicate northward fault propagation, suggesting the NSF is in the early stages of development within a left-lateral transtensional system. Furthermore, our findings support the interpretation of the NSF as the northern extension of the Al-Idrissi Fault, emphasizing its significance for seismic hazard assessment in the region. Finally, we propose that NSF may represent a potential seismic source for a magnitude 6.1 Mw earthquake and suggest it as an alternative source of the 1910 Adra earthquake. This study offers new insights into the early growth and evolution of transtensional fault systems worldwide and their associated seismic potential.

The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration, [CO32-]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based on benthic foraminiferal geochemistry and carbon cycle modelling. Our results indicate a thickening of Atlantic water penetrating into the northern Nordic Seas, forming a subsurface Atlantic intermediate water layer reaching to at least ~2600 m water depth during most of the late glacial period. The recirculating Atlantic layer was characterized by relatively high [CO32-] and low δ13C during the late glacial, and provides evidence for a Nordic Seas source to the glacial North Atlantic intermediate water flowing at 2000–3000 m water depth, most likely via the Denmark Strait. In addition, we discuss evidence for enhanced terrestrial carbon input to the Nordic Seas at ~23.5 ka. Comparing our δ13C and qualitative [CO32-] records with results of carbon cycle box modelling suggests that the total terrestrial CO2 release during this carbon input event was low, slow, or directly to the atmosphere.