A document by Kristian Strommen. Click on the document to view its contents.

Fluid production from dehydration reactions and fluid migration in the subducting slab impact various subduction processes, including intraslab and megathrust earthquakes, episodic slip and tremor, mantle wedge metasomatism, and arc-magma genesis. Quantifying those processes requires a good knowledge of the location and amount of fluid outflux at the top of the slab. Previous models of fluid migration indicate that compaction-pressure gradients induced by the dehydration reactions could drive updip intraslab fluid flow (Wilson et al., 2014). However, how the initial hydration in the oceanic mantle prior to subduction impacts the updip fluid flow has not been investigated. Here, we use a 2-D two-phase flow model to investigate this effect under various initial slab-mantle hydration states and slab thermal conditions, both of which impact the depth extent of the stability of hydrous minerals. We focus on the lateral shift between the site of dehydration reactions and the location of fluid outflux at the top of the slab due to intraslab-updip migration. Our results indicate that major updip fluid pathways form along the antigorite and chlorite dehydration fronts sub-parallel to the slab surface. This, in turn, promotes slab-fluid outflux at the slab surface as shallow as 30–40 km depths. This mechanism is more likely in young slabs (< ~30 Ma), in which the thickness of the hydrated mantle in the incoming oceanic mantle that is required to form the slab-parallel dehydration fronts is relatively small (< ~20 km) because of its warm condition and thus a relatively thin antigorite stability zone.

Given that more than half of the world’s population currently resides in cities, further understanding of the potential impact of future climate change on urban areas is needed. In this regard, we project recent heatwave (HW) episodes in the Metropolitan Area of Barcelona (AMB) with future climate conditions until 2100 using the pseudo global warming (PGW) method. First, we determine all the HWs that occurred in the AMB during the last climatological period of 30 years (1991-2020) and simulate each individual event using the Weather and Research Forecasting (WRF) model at high-resolution. Then, these historical HW events are re-simulated with the modified atmospheric conditions of the mid-century (2041-2070) and the end-of-the-century (2071-2100) according to the scenario SSP370, in which CO2 emissions are projected to almost double from current levels by 2100 following a low emission reduction scenario. HW intensity is expected to increase by 2.5 °C and 4.2 °C in the mid- and end-of-the-century periods, respectively. Higher temperatures are related to stationary and stable synoptic patterns, which are projected to experience the greatest intensification in the future. The geopotential height at 500 hPa could increase up to 100 geopotential meters (gpm) by the end of the century, leading to values up to 6050 gpm, which indicates changes in thermodynamic and dynamic effects resulting in potentially warmer HW episodes. The results obtained can aid in understanding the expected changes for this century, which could facilitate the formulation of heat mitigation and adaptation strategies, particularly for the most exposed areas.

The Io plasma torus in Jupiter’s magnetosphere, dominated by sulfur and oxygen ions from Io’s volcanism, exhibits complex radial structures and significant temporal variability. This study analyzes ground-based optical emission data from the Dual Imaging Spectrograph on the 3.5m telescope at Apache Point Observatory (APO). By combining 30 nights of observations from 2013 to 2018 and co-adding dawn and dusk profiles, we reduce variability and determine steady-state radial conditions. The results of a ”Cubic-cm” spectral emission model are compared with forward modeling techniques to account for projection effects and line-of-sight (LOS) integration. This study provides the first detailed characterization of local conditions within the ribbon, gap region, and cold torus from remote sensing of all major Io plasma torus species (S$^{+}$, S$^{++}$, and O$^{+}$). We find that electron and ion densities in the cold torus are significantly lower than previous Voyager 1 PLS measurements, consistent with later studies. Electron temperatures in the cold torus align with Voyager PLS data, while those in the warm torus are lower than expected from Cassini UVIS and more consistent with contemporaneous Hisaki observations. Key findings include a shift of the cold torus towards Jupiter and a larger gap region, with ribbon locations remaining stable. The electron density profiles show a shallower decline with radial distance in the warm torus than previously reported, highlighting the variability within the Io plasma torus and the challenges of non-uniqueness in fitting plasma parameters determined via remote sensing.

Urban environments are increasingly impacted by heavy metals pollution originating from traffic emissions, solid waste burning, and other anthropogenic sources (i.e., foundries, smelters, oil refineries, petrochemical plants, pesticide production, and chemical industries). Suspended particulate matter (SPM) serves as a carrier for heavy metals, posing a potential risk to vegetation and human health. This study aimed to investigate the levels and distribution of heavy metals, including Ag, Cd, Co, Mo, V, As, Cr, Ni, Pb, Cu, Mn, Zn, and Fe, accumulated on the surface and inside the leaves of six plant species (Ficus benghalensis, Ficus religiosa, Polyalthia longifolia, Azadirachta indica, Ficus benjamina, and Bougainvillea glabra) during the pre-and post-monsoon at Okhla Phase-2 and Siri Fort in the Delhi, India. Leaves samples were collected from both sites during the pre- and post- monsoon and analyzed for heavy metals content using Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). Results revealed that the pre-monsoon exhibited about 9 % higher levels of heavy metals concentration than post-monsoon, possibly because of washout effects due to rainfall during the monsoon and seasonal variations in atmospheric deposition. Moreover, among all plant species the average of accumulated heavy metals in the both seasons inside the leaves has been observed in the following pattern: F. benjamina (55.51 mg/kg) > B. glabra (43.77 mg/kg) > F.benghalensis (40.55 mg/kg) > A. indica (34.23 mg/kg) > P. longifolia (34.00 mg/kg) > F. religiosa (31.51 mg/kg). The study highlighted F. benjamina and B. glabra as potential bioindicators of heavy metal pollution due to their higher metal’s uptake. The findings of this research contribute to understanding heavy metals pollution in urban areas, emphasizing the importance of monitoring, and mitigating the impact of atmospheric deposition on vegetation. Furthermore, identifying plants with varying metals accumulation capabilities can aid in developing phytoremediation strategies to combat metallic pollutants.Keywords: Heavy metals, Bougainvillea glabra, Atmospheric deposition

The North Icelandic Jet (NIJ) is a significant contributor to the lower limb of the Atlantic Meridional Overturning Circulation, supplying one-third to one-half of the overflow water transport through Denmark Strait, including the densest portion. Dense water produced in the Nordic Seas is banked up along the slope north of Iceland and can flow relatively unimpeded across the Denmark Strait sill as part of the NIJ. Major uncertainties remain regarding the mechanisms contributing to the emergence of the NIJ northeast of Iceland. This study investigates these mechanisms using a novel setup with a high-resolution, idealized model for the north Icelandic slope. Initially, we set up a channel model along the slope north of Iceland with differing slope geometry, no external forcing, and horizontally uniform initial and boundary conditions based on observations. Subsequently, we iteratively impose highly idealized inflows and outflows as boundary conditions in the west, emulating the North Icelandic Irminger Current (NIIC) inflow and dense NIJ outflow through Denmark Strait. The model consistently replicates key features of the NIJ, such as its mid-depth intensified core associated with diverging isopycnals away from the slope. Our results corroborate that a steeper slope, a stronger NIIC-like current, and stronger cross-slope density gradients promote instabilities closely related to the emerging NIJ-like current. Furthermore, the variability of the models’ NIJ-like current is largely associated with passing eddies, which might explain some of the observed occupations where the NIJ features a double-core structure.

Distributed Acoustic Sensing (DAS) is increasingly being explored for passive acoustic monitoring of many phenomena, including earthquakes, storms and detecting and tracking ships and whales. It has recently been reported that DAS may also be used to communicate acoustically underwater from low-power submerged sources to shore using incoherent frequency-hopped modulated packets. This new mode of underwater communication to shore could be of significant interest to smart sensors and autonomous vehicles that need to report compact bursts of time-critical information. It is therefore important to understand the conditions under which such communication packets might be well received, as a function cable construction, burial in sediment, acoustic frequency and angle of incidence of the acoustic wave to the cable. This paper reports a preliminary investigation into the latter factors, using data from a recent experiment conducted in Trondheim Fjord, described in a previous paper. We find that suitable conditions extend over a wide range of incidence angles between 30-75 degrees grazing angle to the cable used in that experiment over at least a bandwidth of several kHz. The results suggest that this new mode of underwater communication could offer significant benefits to teams of smart systems monitoring, inspecting or patrolling near or around pipelines, power cables, offshore wind or other installations that have fibre optic cables.

The martian tropical water ice spatial and temporal distribution was characterized using impact crater ejecta type, location, size, and age in one of two epochs, <=3.4 Ga and $>3.4 Ga, using statistical models designed for spatial and temporal correlation structures. The indicator thought to identify the presence of ice is craters with layered ejecta, while the indicator thought to identify no ice is craters with radial ejecta. These indicators imply the location (longitude and latitude) and, potentially, depth (crater diameter as a proxy) of ice, and when the ice was present. The spatial and temporal distribution of layered ejecta versus radial ejecta may inform on the geography and evolution of ice. A statistical spatial point analysis was conducted on a 54-sample data set (craters with diameters 2.77 km to 10.00 km) for an equatorial region (0o to -30o S, and 10o E to 340o W. The analysis shows there is insufficient evidence to support a non-random spatial and temporal distribution of tropical ice.

Local vortex-structured auroral spiral and a large-scale transpolar arc (TPA) were contemporaneously observed by the Polar ultraviolet imager (UVI), when a substorm almost recovered. The TPA grew along the dawnside auroral oval from the nightside to the dayside (oval-aligned TPA), and a chain of multiple auroral spots and spiral were located azimuthally near the poleward edge of the nightside auroral oval. Contemporaneous appearances of the TPA and the auroral spiral can be seen after the spiral appeared alone. Polar also detected the oval-aligned TPA and another dawnside TPA with the nightside end distorted toward the premidnight sector (J-shaped TPA) before and after the spiral’s formation, respectively. To examine these associated magnetotail structures, we performed global magnetohydrodynamic (MHD) simulations, based on two different types of code, BAT-S-RUS and improved REPPU, and examined how the field-aligned current (FAC) profiles varied in association with changes of the auroral form to TPA and/or auroral spiral. Global MHD simulations with the two different types of code can reproduce the TPAs and the associated FAC structures in the magnetotail. The auroral spiral and its nightside FAC profile, however, were not formed in both simulations, suggesting that its formation process cannot be treated within an MHD framework but is closely related to some kinetic process. When the J-shaped TPA and the auroral spiral contemporaneously appeared, the two MHD simulations could not reproduce the TPA, spiral and their associated magnetotail FAC structures, also advocating that a kinetic effect related to the spiral formation might prevent the TPA occurrence.

The F10.7 solar radio flux is a critical quantity for operational space weather nowcasting and forecasting, where it is routinely used as a driver for coupled atmospheric models to estimate a variety of important quantities such as the neutral atmospheric density. Although there have been several successful developments in the way of parametric modeling to ensure F10.7 coverage during outages (often using the sunspot number or radio flux observations at neighboring wavelengths), these developments refrained from employing comprehensive cross-validation schemes to ensure model generalizability, and can stand to benefit from recently-developed techniques for modeling nonlinear phenomena. We present an approach that uses Feature Ordering by Conditional Independence (FOCI) to identify favorable surrogates for the F10.7 index through a series of distance computations, and combines this with modeling of F10.7 with linear models and Generalized Additive Models (GAM). We find that this approach offers notable improvements in reconstructing F10.7 over gaps of various lengths, with GAMs yielding mean error of ∼2.7%, compared to polynomial methods that yield mean errors of ∼3.1%. We additionally demonstrate the effect of reconstruction error on neutral densities modeled by the NRLMSISE2.0 thermosphere model.

Clouds are crucial to Earth’s climate system, influencing radiation and contributing to climate projection uncertainties. Here, the simulated cloud fraction by the sixth version of the Canadian Regional Climate Model (CRCM6/GEM5) was evaluated using CALIPSO lidar retrievals and the second version of the Cloud Feedback Intercomparison Project (CFMIP) Observation Simulator Package (COSP2) for the years 2014 and 2015. Horizontal and vertical distributions of clouds in the CRCM6/GEM5 model were evaluated using cloud profiles and four cloud categories (total, high-, mid- and low-level clouds) derived directly from the CRCM6/GEM5 model and treated using the COSP2 satellite simulator. A seasonal analysis was conducted across specific regions in North America. Results showed that the use of COSP2 is essential for comparing CRCM6/GEM5 outputs against satellite data to account for variable definitions and signal attenuation of active instruments (e.g., Cloud-Aerosol Lidar with Orthogonal Polarization: CALIOP). Spatial and vertical cloud distributions and seasonal patterns were generally well represented by the CRCM6/GEM5 for both winter (December-February) and summer (June-August). High- and low-level clouds were particularly well-represented, especially in winter. The CRCM6/GEM5 model demonstrated some difficulty producing enough clouds to accurately represent those at mid-level. Cloud fraction representation was systematically better during winter than summer. The CRCM6/GEM5 generally performed well over the whole North American domain for the four cloud categories and COSP2 was confirmed to help mitigate discrepancies in variable definitions. These results contribute to a better understanding of the CRCM6/GEM5 cloud representations and the use of COSP2 with high-resolution models.

Solar flares are major manifestations of solar activity, characterized by intense radiation and particle emissions that affect the entire solar system. High-accurate prediction of solar flare events for solar cycle 25 is crucial for understanding and mitigating these effects. In this work, we used soft X-ray flux from the GOES satellites and the chromospheric flare index to predict solar flare activity for solar cycle 25. Our results show that: (1) There is a temporal and intensity asymmetry between the northern and southern hemispheres, with the southern hemisphere showing greater flare activity during solar cycle 25. (2) Flare activity exhibits Gnevyshev peaks, and the double-peak structures are more prominent than other atmospheric layers. The Gnevyshev peaks may be related to the different timescales of the solar flare responses to the geomagnetic field and the interplanetary magnetic field. (3) Chromospheric flare activity lags behind photospheric sunspot activity. This phase lag phenomenon may be related to the magnetic energy storage in the corona, indicating that changes in sunspot activity occur before flare activity. (4) The activity level of solar cycle 25 will be more pronounced than that of solar cycle 24. This phenomenon may be related to the modulation effect of the Gleissberg cycle, which has been validated by geomagnetic precursor indices. Our results provide valuable insights into the temporal and spatial distribution of solar flare activity during solar cycle 25.

Climate models often face challenges in accurately simulating the daily precipitation cycle over tropical land areas, particularly in the Amazon. One contributing factor may be the incomplete representation of the diurnal evolution of shallow cumulus (ShCu) clouds. This study aims to enhance the understanding of the diurnal cycles of ShCu clouds—from formation to maturation and dissipation—over the central Amazon (CAMZ). Using observational data from the Green Ocean Amazon 2014 (GoAmazon) campaign and large-eddy simulation (LES) modeling, we analyzed the diurnal cycle of six selected pure ShCu cases and their composite behavior. Our results reveal a well-defined cycle, with cloud formation occurring between 10-11 local time (LT), maturity from 13-15 LT, and dissipation by 17-18 LT. The vertical extent of the liquid- water mixing ratio, and the intensity of updraft mass flux were closely associated with increases in turbulent kinetic energy (TKE), enhanced buoyancy flux within the cloud layer, and reduced large-scale subsidence. We further analyzed the diurnal cycles of convective available potential energy (CAPE), convective inhibition (CIN), the Bowen ratio (BR), and vertically integrated TKE in the mixed layer (ITKE-ML), exploring their relationships with cloud base mass flux (Mb) and cloud depth across six ShCu cases. ITKE-ML and Mb exhibited similar diurnal trends, peaking at approximately 14-15 LT. However, no consistent relationships were found between CAPE (or BR) and Mb. Similarly, comparisons of cloud depth with CAPE, BR, ITKE-ML, CIN, and Mb revealed no clear relationships. Smaller ShCu clouds were sometimes linked to higher CAPE and lower CIN. It is important to emphasize that these findings are preliminary and based on a limited sample of ShCu cases. Further research involving an expanded dataset and more detailed analyses of the TKE budget and synoptic conditions is necessary. Such efforts can yield a more comprehensive understanding of the factors influencing ShCu clouds’ vertical development.

Typhoon Saola’s (2023) anti-clockwise loop track was monitored by six spaceborne synthetic aperture radar (SAR) images, offering a unique opportunity to investigate the physical factor known as steering flow, a widely accepted concept for studying tropical cyclone (TC) movement and storm surges. Despite its importance, direct observations of steering flows are limited. To address the complex movements observed during the loop track, we propose a novel method to decompose the SAR-derived high-resolution surface wind field into: 1) symmetric rotational winds, 2) general steering flow across three consecutive SAR cases within ~24 hours, and 3) the remaining steering flow. Our analysis reveals that the newly determined remaining steering flows from north effectively explain the loop track associated with two general steering flows, identified as the western North Pacific summer monsoon (WNPSM) from southeast and Indian summer monsoon (ISM) from southwest.

The 2022 eruption at Mauna Loa, Hawai‘i, marked the first extrusive activity from the volcano after 38 years of quiescence. The eruption was preceded by several years of seismic unrest in the vicinity of the volcano’s summit. Characterizing the structure and dynamics of seismogenic features within Mauna Loa during this pre-eruptive interval may provide insights into how pre- and co-eruptive processes manifest seismically at the volcano. In particular, the extent to which seismicity may be used to forecast the location and timing of future eruptions is unclear. To address these questions, we construct a catalog of relocated seismicity on Mauna Loa spanning 2011-2023. Our earthquake locations image complex, sub-kilometer-scale seismogenic structures in the caldera and southwest rift zone. We additionally identify a set of streaks of seismicity in the volcano’s northwest flank that are radially oriented about the summit. Using a rate-and-state friction model for earthquake occurrences, we demonstrate that the seismicity rate in this region can be modeled as a function of the stressing history caused by magma accumulation beneath the summit. Finally, we observe a mid-2019 step change in the seismicity rate in the Ka‘oiki region that may have altered the stress state of the northeast rift zone in the three years before the eruption. Our observations provide a framework for interpreting future seismic unrest at Mauna Loa.

A document by Aymeric Fleury. Click on the document to view its contents.

A document by Jennifer K McWhorter. Click on the document to view its contents.

A knowledge gap in our understanding of the global carbon and water cycle, which in turn impacts climate science insights and earth systems model development, is the relative dominance of the drivers of vegetation productivity and subsequently the atmospheric carbon-dioxide growth rates (CGR). There is a lively debate in the literature based on correlation or bivariate causal methods, on whether the primary driver(s) is (are) temperature (T) or water availability, specifically, precipitation (P), soil moisture (SM), and/or terrestrial water storage (TWS). Our data-driven causal analyses, which rely on Granger Causality (GC) and the Peter and Clarke Momentary Conditional Independence (PCMCI) tests, consider all potential causal variables holistically, and reveal two primary atmospheric drivers for net ecosystem exchange and CGR: vapor pressure deficit (VPD) and photosynthetically active radiation (PAR). Our findings challenge recent literature, underscore the critical role of evaporative demand and vegetation dynamics in atmospheric carbon sensitivity, and highlight the need for more robust causal testing methods.