This study presents basin-wide, full-depth profiles of nitrate δ15N (vs. Air) and δ18O (vs. Vienna Standard Mean Ocean Water, VSMOW) in the Mediterranean Sea. Our results reveal a consistent 15N depletion across the entire Mediterranean Sea in comparison to the global ocean, with significantly lower nitrate δ15N values in the eastern basin (2.2 ± 0.2‰) than in the western basin (2.9 ± 0.1‰). In contrast, there is no significant difference in nitrate δ18O between the two basins (2.2 ± 0.3‰ and 2.1 ± 0.2‰, respectively). These observations point to an external supply of low-δ15N N to the Mediterranean Sea, accumulating as nitrate. This supply is diluted by the Atlantic inflow, creating an east-to-west gradient in nitrate δ15N. Earlier studies have attributed the external low-δ15N N supply to either N2 fixation or atmospheric deposition of anthropogenic N. A four-box model reveals that, given the water residence time of 120–170-years in the Mediterranean, a modest input rate of 1–3 Tg N yr-1 from either of these two sources or their combination is adequate to produce the observed low δ15N of Mediterranean nitrate. Additionally, partial degradation of dissolved organic nitrogen imported from the Atlantic is another possible source of the low-δ15N nitrate in the Mediterranean. Distinguishing among these sources will be aided by reconstruction of Mediterranean nitrate δ15N through time, using either time-series data of nitrate δ15N or paleoceanographic proxies.

The Amapari Marker Band (AMB) is a layer within the Mount Sharp stratigraphy that has been mapped around Gale crater in orbital images and was recently investigated up close by the Curiosity rover. Symmetric wave ripple marks within the AMB indicate a lacustrine depositional environment in the area investigated along the Curiosity traverse. The wavelength and morphology of the ripples constrain the water depth to a few meters or less. The lateral continuity of the ripple unit defines a minimum extent of the lake during ripple formation. The stratigraphy of the AMB is consistent with an environment of increasing water depth during sedimentation and the lateral correlation of the AMB stratigraphy suggests a transgressive depositional system building upon an eroded surface. The location of the AMB within the surrounding aeolian stratigraphy, coupled with the progression of depositional environments through the Mirador formation, record a pattern of a rising water table relative to sedimentation rates. The potential regional extent of the lacustrine environment, based on orbital mapping of the AMB’s variable elevation, spans at minimum 2.0 km of the lateral AMB deposit in the area around Marker Band Valley and may have extended up to 14 km to the west across northern Gale crater.

The Inflation Reduction Act (IRA) of 2022 represents a landmark legislative effort aimed at accelerating the United States’ transition to a net-zero emissions economy by 2050. Among its key provisions are incentives designed to bolster the deployment of carbon capture and storage (CCS) technologies. However, the efficacy of these incentives remains uncertain, particularly in scenarios where the cost of CCS remains prohibitively high. This study leverages the Global Change Analysis Model-USA (GCAM-USA) coupled with the Environmental Protection Agency’s Co-Benefits Risk Assessment (COBRA) model to conduct a comprehensive regional assessment of economy-wide technological change, deployment of CO2 removal (CDR) technologies, air quality and public health outcomes by 2050 within the framework of the IRA.

Electricity is a basic human necessity. We are highly reliant on continuous access to electricity for our health, well-being, and it remains essential for critical infrastructure, industries, and human development. Yet, there remains a gap in populations with access to electricity across the globe. Mapping where gaps in electrification are currently located is vital to estimate the unmet energy demand to ensure universal access to electricity and modern fuels. To be informative, mapping of electricity access gaps is needed on a global scale but with spatially-disaggregated granularity and it is non-trivial to derive this spatially-explicit data at the global scale. Satellite observations have the unique vantage point of acquiring global observations with frequent updates and are collected in a standardized manner. Specifically, NASA’s Black Marble product derives corrected, global, daily nighttime lights (NTL) that are ideally suited for analyzing urban areas and human settlements with its decade-long records. We utilize this daily dataset to derive neighborhood scale (1km) global maps of electrification using NTL time-series from 2012-2022 and fill in the existing global knowledge gap using highest quality NTL data. We evaluate our analyses with existing global surveys at the national scale and observe high agreement, derive quality flags, and share the results as an open-access dataset. We analyze our dataset to examine the areas with highest access gaps and discuss the potential of the dataset to inform energy transition plans and electricity demand estimations for integrated assessment models that jointly evaluate the effects of climate change and energy transitions.

Finite fault models using satellite radar interferometry data indicate that the Mw 6.4 Puerto Rico earthquake occurred on a N-dipping fault. Focal mechanism solutions of aftershocks show three trends of strike-slip faults including two parallel WNW-ESE left-lateral faults. The parallel strike-slip faults bound a left-stepping pull-apart basin which localizes the most concentrated area of the swarm.

Since the 2011 M9.0 Tohoku-Oki megathrust earthquake, many normal-faulting earthquakes have occurred off northeastern Japan in the upper plate, indicating a trench-normal tensional stress state opposite to that in the inland back-arc area. Determining the spatiotemporal evolution of the stress field is essential for understanding the earthquake occurrence mechanisms in the upper plate of the megathrust. However, the focal depths of normal-faulting earthquakes are not well-constrained due to the lack of observational data directly above the earthquakes. In this study, we first developed a high-frequency waveform modeling method to constrain earthquake depths by reproducing sP depth phases. We then applied the method to M{greater than or equal to}3 earthquakes off southern Tohoku, where intense normal-faulting earthquakes occurred. By comparing the observed waveform envelopes with their synthetic counterparts, we estimated focal depths of 300 events. The estimated focal depths are consistent with those estimated from seafloor seismic observations, supporting the validity of our estimates based solely on inland data. We then conducted relative hypocenter relocation using the events whose focal depths were estimated by sP depth phases as master events to obtain hypocenters of 8,599 events. The results showed that these normal-faulting earthquakes occurred near the surface to a depth of approximately 30 km. This suggests that a tensional stress state prevails from the shallow to deep regions above the megathrust. One possible cause of the tensional stress is gravity force. The effect of plate convergence may not be sufficiently large to make the fore-arc region a compression regime.

This study aimed to evaluate the potential dam breach scenario of the proposed Naumure Dam using the HEC-RAS model. Hydrological and meteorological data from the study area were used to calculate the probable maximum flood, serving as a hydrological input for the model. Geometric data such as reservoir area, inline structure, streamline, riverbank, and flow path were modeled using the HEC-RAS RAS-Mapper tool. Various parametric equations were employed to calculate the breach parameters, which were then input into the HEC-RAS 5.0.7 simulation model along with the input hydrograph. Subsequently, an unsteady flow analysis was conducted to direct the flood through each cross section of the river. The model yielded a maximum flow rate of 141,423.48 m3/s at the dam axis 3.8 hours after the onset of dam failure. The study area, which extended 31.6 km downstream, was analyzed and hydrographs at different cross sections were examined. The results were mapped onto topographic GIS maps to identify affected areas. Approximately 30 km downstream, the settlement area in Bhalubang was inundated with a peak discharge of 48,579.29 m3/s at this location. The research will help relevant authorities devise an emergency response strategy and implement flood mitigation measures.

• Background seismicity rates correlate with geodetic strain rates computed from GNSS velocities in the Apennines • The strain-seismicity relationship is strongly influenced by how the strain rate is computed and how seismic catalogs are declustered • The tectonic moment rate computed from geodetic strain rate maps and seismogenic thickness exceeds the estimated seismic moment release rate

In 2023, the biogeographic Amazon experienced temperature anomalies of 1.5°C above the 1991-2020 average from September to November. These conditions were driven by high sea surface temperature in the Atlantic and Pacific oceans, together with reduced moisture advection from the Atlantic, causing large vapor pressure and water deficits in the second semester of 2023. Here, we evaluate the response of the Amazon carbon cycle to this extreme event across different spatial scales. We combined atmospheric CO₂ mole fractions and eddy covariance flux data from the Amazon Tall Tower Observatory (ATTO), near-real-time simulations by Dynamic Global Vegetation Models (DGVMs), an atmospheric inversion, and remote sensing data. We find that in 2023 the Amazon region was, including fires, a net carbon source of 0.01 to 0.17 PgC. Fire emissions (0.15 [0.13-0.17] PgC) were within typical variability of the 2003-2023 period, thus we attribute the weak carbon source to reduced vegetation uptake during the dry season. A stronger-than-normal vegetation uptake early in the year (January to April), consistent across data streams and spatial scales, mitigated the total carbon losses by the end of the year. We find a shift from carbon sink to source in May and a peak source in October. Our findings show a reduced vegetation carbon uptake over the Amazon region, leading to a weak carbon source that contributed 30% of the net carbon loss in the tropical land in 2023.

After two decades of development, the Surface Water and Ocean Topography (SWOT) mission launched on December 16, 2022, pioneering the use of Ka-band Radar Interferometry (KaRIn) for measuring water surface elevation and achieving wide-swath, two-dimensional altimetry. Rigorous validation against in-situ observations in this study demonstrates that KaRIn achieves enough accuracy to resolve sub-100 km oceanic processes, with measurement errors four times smaller than anticipated. These results confirm SWOT’s transformative capabilities for advancing oceanographic research, validating the high fidelity of the advanced mooring systems and establishing a robust foundation for future applications of the wide-swath altimetry.

A document by Kutalmis Saylam. Click on the document to view its contents.

A document by Hesam Saeidi. Click on the document to view its contents.

To decipher the effects of space-time dynamics of precipitation on the resulting streamflow hydrographs, we herein analyze the controls of timing and shape of the 93,862 hourly streamflow events observed in 199 small German catchments. Using precipitation radar observations, spatially-distributed soil moisture data and landscape properties we derive a comprehensive set of potential controls that apart from standard catchment- and event-averaged precipitation and wetness (i.e., lumped) characteristics represent: the space-time structure and the location of precipitation events within catchments; interaction of precipitation with surface (land use) and subsurface (soil) properties; and interaction of precipitation with antecedent wetness conditions. We find that among considered spatially- and temporally-differentiated controls, particularly the characteristics describing the location of precipitation event relative to catchment outlet and stream network, as well as the interaction of precipitation with the dynamic soil moisture and static soil characteristics have strong effect on the timing of hydrographs. Instead, spatial and temporal structure (i.e., its uniformity or variability in space and time) strongly defines their shapes. We also find that lumped precipitation and wetness characteristics are less relevant for large streamflow events (i.e., magnitudes larger than 95th percentile). Instead, the space-time interaction of precipitation events with antecedent soil moisture is crucial for accurately predicting the timing and shape of large events. The pronounced importance of spatially- and temporally-differentiated precipitation characteristics and their interaction with catchment states for the shape and timing of particularly large events, indicates the need to account for these aspects to improve the accuracy of flood simulations.

To predict the effect of climate and CO2 on vegetation and soils, process-based models require accurate numerical representations of photosynthesis, respiration, turnover rates of below-ground carbon, and plant community change. We add 13C and 14C to the Lund-Potsdam-Jena (LPJ) dynamic global vegetation model (DGVM), which also includes representations of fire, land-use change, agriculture, and vegetation dynamics. Six sets of model simulations CO2 and 13CO2 fluxes are transported using the TM5 atmospheric transport model and evaluated by comparison to observations of CO2 and 13CO2 in measurements obtained from NOAA global monitoring sites. Updating the respiration and photosynthesis formulations in LPJ improves the seasonal cycle of simulated CO2 fluxes but does not improve simulated 13CO2 fluxes. Global annual land 13C photosynthetic fractionation and disequilibrium are similar to previous estimates by other DGVMs. To evaluate model performance for 14C, simulated soil and heterotrophic respiration 14C:C ratios are compared to observations from the International Soil Radiocarbon Database. Simulated soil Δ14C values are significantly higher than measurements as found in previous studies. Soil flux Δ14C values have less of a positive bias than soil Δ14C values indicating that, while soil residence times could be improved, some old soil carbon is very recalcitrant and may not need to be modeled to reproduce fluxes. This study emphasizes the power of using 13C and 14C to test whether model changes that improve bulk C are improving underlying processes such as stomatal conductance or soil turnover rates.

Urban expansion and the increasing frequency and intensity of extreme precipitation events bring new challenges to stormwater collection systems. One underrecognized issue is the occurence of transient flow conditions that lead to adverse multiphase flow interactions (AMFI): essentially, the formation, collapse, and uncontrolled release of air pockets within stormwater system flows. While the fundamental physics of AMFI have been evaluated in laboratory experiments and idealized modeling studies, much less is known about their development in real or simulated stormwater networks, and about the roles played by rainfall and network properties. A necessary precursor to AMFI is the development of pressurized flow conditions within a network. The goal of this study is to understand how spatiotemporal rainfall variability affects the occurrence of pressurized conditions in a stormwater drainage network in the Richmond district of San Francisco, California. High-resolution bias-corrected radar rainfall fields for 24 recent storms were used as the independent variable of EPA-SWMM simulations. Model analyses indicate that the incidence of pressurized flow increases with storm intensity, and is more sensitive to rainfall temporal variability than spatial variability.

Humans are altering coastal regions directly (land-use, drainage) and indirectly (climate change). Alterations potentially create positive climate feedback loops by enhancing production and emission of aquatic greenhouse gasses (CO2, N2O, and CH4). We tested this hypothesis by measuring dissolved CO2, N2O, and CH4 concentrations across the anthropogenic aquatic continuum (farm ponds, ephemeral ditches, irrigation drains, streams, tidal rivers, and estuaries) and continuously during an extreme weather event. Combining measurements with hydrodynamic modelling revealed artificial waterways contributed disproportionately to emissions: ditches and drains cover 5% of water surface area but produced 50% of emissions (4 - 7 Mmol d-1 CO2-equivalents). However, extreme weather inverted this pattern by increasing estuary emissions 16-fold to 18 Mmol d-1 CO2-equivalent. Predicted changes to storm frequencies would alter both sources and magnitudes of coastal emissions. Findings demonstrate the need to include both overlooked artificial drains and hard-to-measure storms in the aquatic offsets of landscape carbon budgets.

The recent installation of new broadband seismic stations in the French Massif Central (FMC) has resulted in the detection of a few ”deep” earthquakes located near the crust-mantle boundary beneath volcanic regions. Analysis of the spectral content of the respective waveforms has shown that the spectra of these ”deep” earthquakes are significantly depleted in high frequencies. Based on these observations of anomalous depth and spectral content, these earthquakes can be classified as Deep Long Period (DLP) events. This is a specific class of volcanic seismicity observed beneath many active volcanoes around the World. While the exact physical origin of this type of earthquakes is still debated, they are often considered as indicators of the presence of magma near the crust-mantle boundary. Therefore, observation of DLP earthquakes can bring new insights into understanding the state and the activity of the recent FMC volcanoes.

Levees are critical infrastructure to mitigate flood hazards worldwide. Despite their importance, current global flood models inadequately account for levees due to the complexity of flow mechanisms involving levees and the lack of comprehensive levee data. This research aims to address these gaps by developing a levee module suitable for global flood modeling and proposing a reach-level parameterization approach to estimate the necessary levee parameters on a global scale. Specifically, we developed a simplified levee module based on the CaMa-Flood global flood model, requiring only two levee parameters: levee unprotected fraction and equivalent levee height. We then identified river reaches globally that are protected by levees and estimated the levee parameters for these reaches using open-access land use and levee standard data respectively. Finally, we evaluated the model’s performance by comparing changes in river hydrodynamics and flood hazard maps, with and without levees, against observed data or official flood records from representative case studies. The results showed that (1) the proposed approach successfully identified globally protected reaches with a high hit rate of 91.3%; (2) the levee unprotected fraction can be accurately estimated based on open-access land-use data, and equivalent levee height can be derived from flood defense data using the global flood model; and (3) The enhanced CaMa-Flood model, incorporating the levee module, accurately simulated both river hydrodynamics and flood hazard mapping, improving the mean Nash-Sutcliffe efficiency of water levels from 0.68 to 0.84 and increasing the mean accuracy of flood hazard mapping from 76% to 87%.