Intense Events Research Articles

How Have Hydrological Extremes Changed over the Past 20 Years?

Abstract Severe floods and droughts, including their back-to-back occurrences (weather whiplash), have been increasing in frequency and severity around the world. Improved understanding of systematic changes in hydrological extremes is essential for preparation and adaptation. In this study, we identified and quantified extreme wet and dry events globally by applying a clustering algorithm to terrestrial water storage (TWS) data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (FO). The most intense events, ranked using an intensity metric, often reflect impacts of large-scale oceanic oscillations such as El Niño–Southern Oscillation and consequences of climate change. The severity of both wet and dry events, represented by standardized TWS anomalies, increased significantly in most cases, likely associated with intensification of wet and dry weather regimes in a warmer world, and consequently, exhibited strongest correlation with global temperature. In the Dry climate, the number of wet events decreased while the number of dry events increased significantly, suggesting a drying trend that may be attributed to climate variability and possible increases in irrigation and reliance on groundwater. In the Continental climate where temperature has risen faster than global average, dry events increased significantly. Characteristics of extreme events often showed strong correlations with global temperature, especially when averaged over all climates. These results suggest changes in hydrological extremes and underscore the importance of quantifying total water storage changes when studying hydrological extremes. Extending the GRACE/FO record, which spans 2002 to the present, is essential to continuously tracking changes in TWS and hydrological extremes.

Influence and characteristics of anticyclonic eddies in active MHW years in the Northwest Atlantic

The Northwest Atlantic contains two subregions, the Gulf of Maine and the Mid-Atlantic Bight. This region is dynamically controlled by the Jet Stream, the Gulf Stream, (GS) and its eddies. Anticyclonic eddies (AEs) (warm core clockwise eddies) and cyclonic eddies (cold core counterclockwise eddies) influence oceanic properties as they are shed by the GS and dissipated in the Northwest Atlantic. Marine Heatwaves (MHWs) are extreme temperature events that cause ecological damage in the Northwest Atlantic where drivers for these events are abundant. This work focuses on four major MHW active years (2012, 2016, 2017, and 2020) and observes the characteristics of MHWs, AEs, and oceanic parameters, such as Ocean Heat Content, Mixed Layer Depth, temperature, and salinity anomalies. Depth profiles, lead-lag covariance and correlations, and comparisons of events reveal dynamics of MHW intensification in these four years. AE radius, amplitude, and eddy kinetic energy (EKE) were less variable in the MHW years of 2012, 2016, and 2017 but have a weak relationship with MHW intensity. The Gulf of Maine had the strongest (above 0.80) correlation between GS eddy heat flux convergence and MHW intensity. The 2012 MHWs were shown to be strongly influenced by the GS in addition to atmospheric forcings, as were the 2017 Gulf of Maine MHWs. The 2020 MHWs experienced a number of forcings from the Jet Stream, the GS, and AEs, with the highest intensity events occurring at depths below 100 m. We conclude that better understanding how regional dynamics and multiple drivers intensify MHWs to form MHW active years is key to modelling and forecasting future extreme events.

Modelling Paroxysmal and Mild-Strombolian Eruptive Plumes at Stromboli and Mt. Etna on 28 August 2019

Volcanic eruptions pose a major natural hazard influencing the environment, climate and human beings at different temporal and spatial scales. Nevertheless, several volcanoes worldwide are poorly monitored and assessing the impact of their eruptions remains, in some cases, challenging. Nowadays, different numerical dispersion models are largely employed in order to evaluate the potential effects of volcanic plume dispersion due to the transport of ash and gases. On 28 August 2019, both Mt. Etna and Stromboli had eruptive activity; Mt. Etna was characterised by mild-Strombolian activity at summit craters, while at Stromboli volcano, a paroxysmal event occurred, which interrupted the ordinary typical-steady Strombolian activity. Here, we explore the spatial dispersion of volcanic sulphur dioxide (SO2) gas plumes in the atmosphere, at both volcanoes, using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) considering the ground-measured SO2 amounts and the plume-height as time-variable eruptive source parameters. The performance of WRF-Chem was assessed by cross-correlating the simulated SO2 dispersion maps with data retrieved by TROPOMI and OMI sensors. The results show a feasible agreement between the modelled dispersion maps and TROPOMI satellite for both volcanoes, with spatial pattern retrievals and a total mass of dispersed SO2 of the same order of magnitude. Predicted total SO2 mass for Stromboli might be underestimated due to the inhibition from ground to resolve the sin-eruptive SO2 emission due to the extreme ash-rich volcanic plume released during the paroxysm. This study demonstrates the feasibility of a WRF-Chem model with time-variable ESPs in simultaneously reproducing two eruptive plumes with different SO2 emission and their dispersion into the atmosphere. The operational implementation of this method could represent effective support for the assessment of local-to-regional air quality and flight security and, in case of particularly intense events, also on a global scale.

Surviving the heat: multiwavelength analysis of V883 Ori reveals that dust aggregates survive the sublimation of their ice mantles

ABSTRACT Investigating the response of icy dust aggregates to water ice sublimation is essential for understanding the formation and properties of planetesimals in protoplanetary discs. However, their fate remains unclear, as previous studies suggest that aggregates could either survive or completely fall apart to (sub)μm-sized grains. Protoplanetary discs around stars undergoing accretion outbursts represent a unique laboratory to study the ice sublimation process, as the water snowline is pushed outward to regions accessible to current observatories. In this work, we aim to understand the aggregates’ response to ice sublimation by focusing on V883 Ori, a system currently undergoing a powerful accretion outburst. We present new analysis of archival high-resolution ALMA observations of the protoplanetary disc of V883 Ori at 0.88, 1.3, 2.0, and 3.1 mm, and derive new radial spectral index profiles, which we compare with predictions from one-dimensional dust evolution simulations. In the region of V883 Ori where water ice has sublimated, we find lower spectral indices than previously obtained, indicating the presence of cm-sized particles. Coupled with our dust evolution models, we find that the only way to explain their presence is to assume that they formed before the outburst and survived the sublimation process. The resilience of dust aggregates to such intense events leads us to speculate that it may extend to other environments with more gentle heating, such as pebbles drifting through the water snowline in quiescent protoplanetary discs. In that case, it may alter the formation pathway of dry planetesimals interior to the snowline.

Investigation of oil emission mechanisms in a marine medium-speed dual-fuel engine

Pilot-ignition Otto marine engines are known for greatly reduced emissions of air pollutants (sulphur oxides, nitrogen oxide, particulates) compared to marine diesel engines. However, lubricating oil emissions still are about one order of magnitude higher than in land-based systems. To identify reduction potentials, a better understanding of oil emission mechanisms has to be gained. For this purpose, mass spectrometric oil emission measurements and fluorescence lubricating film thickness measurements were performed on a medium-speed marine engine. With the fluorescence measuring system, the varying lubricating oil film on the cylinder wall can be visualised and analysed in sub-crank-angle resolution. By applying the developed calibration method to the measurement data, the oil film thickness can be determined in µm. It is shown that the oil film left by the piston rings on the liner as it moves down is almost halved after ignition compared to during intake stroke. The authors have further been able to detect and time operating point dependent ring rotation and investigations show a connection between ring rotation and cylinder liner temperature distribution. Aligning ring gaps allow blow-by to happen. This and other high intensity events such as engine knock, load shedding or the transition from diesel-mode to gas-mode, heavily disturb the oil layer and cause peaking oil emissions.

Rapid attribution of the record-breaking heatwave event in North China in June 2023 and future risks

A record-breaking heatwave event occurred in North China from 22 to 24 June 2023, with temperatures >40 °C at many meteorological stations. This marked the first time that Beijing had reached or exceeded 40 °C for three consecutive days. However, the extent to which such exceptional heatwave events are related to anthropogenic climate change remains unclear. It is also unclear how frequent and intense such strong heatwave events will be in the future. We carried out a rapid attribution analysis to address these questions. Our findings show that the return period of this three-day heatwave event in North China is about 111 years (24.3, +∞) at the 2023 climate state. Both the empirical and coupled model approaches consistently showed that the intensity of 2023-like three-day heatwave events has significantly increased by at least 1.0 °C (range 0.8 °C–1.3 °C) due to anthropogenic climate change. Future projections indicate that 2023-like events in North China are likely to occur at least 1.6 (range 1.3–2.1) times throughout the remainder of this century and be 0.5 °C (range 0.2 °C–0.8 °C) more intense than those under the 2023 climate even if carbon neutrality is achieved based on the very low CO2 emissions scenario simulations. For the intermediate emissions scenario, the occurrence probability of 2023-like events in the North China region by the end of this century will be 5.5 (range 4.9–6.3) times those under the 2023 climate, with an intensity 2.9 °C (range 2.4 °C–3.1 °C) higher than those under the 2023 climate. These findings highlight the need for adaptation measures to address the occurrence of 2023-like three-day heatwaves in North China in June even if carbon neutrality is achieved.

Numerical Prediction of Changes in Atmospheric Chemical Compositions During a Solar Energetic Particle Event on Mars

AbstractPrecipitation of solar energetic particles (SEPs) into planetary atmospheres causes changes in atmospheric chemical composition through ionization, dissociation, and excitation of atmospheric molecules. In contrast to the terrestrial atmosphere, where depletion of ozone in the polar mesosphere has been studied by observations and models for decades, there have been no studies on the effects of SEPs on the neutral chemical composition of Mars' present‐day atmosphere. This study provided the first estimate of the impacts of SEPs on neutral chemical composition in the present‐day Martian atmosphere coupling a Monte Carlo model and a one‐dimensional photochemical model. Our results showed that ozone density in the Martian atmosphere might decrease in the altitude range of 20–60 km with a factor 10 maximum enhancement occurring at 40 km during a Halloween‐class SEP event due to an enhanced concentration of HOx. The depletion of ozone occurred in the altitude range of 20–60 km, corresponding to the penetration of protons with an energy range of 4.6–46 MeV. Such ozone depletion should be detected by Trace Gas Orbiter/Nadir and Occultation for MArs Discovery during intense SEP event. A 75% depletion of the ozone density at 40 km can be expected during SEP events occurring once in every 1 year. Therefore, ozone concentration in the Martian atmosphere might sufficiently decrease during a SEP event as on Earth, but through different chemical pathways driven by CO2 ionization and CO recombination catalytic cycle.

Psychophysiology, Cognitive Function, and Musculoskeletal Status Holistically Explain Tactical Performance Readiness and Resilience.

Thompson, AG, Ramadan, JH, Alexander, JS, and Galster, SM. Psychophysiology, cognitive function, and musculoskeletal status holistically explain tactical performance readiness and resilience. J Strength Cond Res 37(12): 2443-2456, 2023-This study aimed to advance the techniques used in quantifying holistic readiness and resilience within military personnel. Tactical performers, instructors, and applied human performance scientists designed a weeklong competition to reflect realistic operational demands, test specific underlying performance constructs, and elucidate how modernized assessments could drive programmatic action. By placing first in their installation's local preliminary competition, 34 active-duty Marines earned the opportunity to compete in a series of 7 intense events for the title of champion. All inferential statistics were set to a p ≤ 0.05 level of significance. Morning heart rate variability identified top from bottom quartile finishers before a single competition event. By day 3, morning countermovement jump force production (normalized reactive strength index-modified) and cognitive psychomotor vigilance were significant indicators of performance resilience and final competition group rank. Heart rate variability also tracked performer readiness across time, identifying within-group and between-group differences among top, bottom, and field. Collectively, these holistic assessments proved significant markers of acute and chronic tactical performance capabilities. In summary, the incorporation of psychophysiological monitoring, cognitive performance testing, and musculoskeletal force plate evaluations could help inform selection and support needs, drive workload or recovery modulation, and provide critical metrics for evaluating training efficacy and operational readiness. Defense organizations should consider routinely incorporating and actioning similar holistic status monitoring strategies in training and operational settings. Moreover, leveraging other tactical competitions may provide key opportunities for advancing the standard of practice through additional scientific investigation.

Geomagnetically induced potential on pipelines: A probabilistic approach

The paper presents a probabilistic approach for the determination of the potential induced along a pipeline route during a geomagnetic storm; particular emphasis is given to intense events such as 100-year and 10-year storms. By assuming that the induced geoelectric field orientation at the ground level and at a given latitude can be treated as a random variable with normal probability distribution, by means of a Monte Carlo algorithm it is possible to build up the empirical probability distribution of the induced potential along the pipeline. The main result is that, in case of an extreme event such as a 100-year storm, even at middle latitudes, potentials of several tens of Volts have a not negligible probability of being induced, at least one time during the pipeline life, along the plant route with possible consequences of damages to apparatuses and equipment connected to the pipeline itself.

Synergies or trade-offs between surface urban heat island and hot extreme: Distinct responses in urban environments

Hot extremes are among the most damaging climate extremes to human society, with urban areas being particularly vulnerable due to the surface urban heat island (SUHI). Despite the growing frequency and intensity of surface hot extreme (SHX), a comprehensive understanding of the patterns and drivers of SUHI responsiveness to SHX (difference in SUHI intensity [δSUHII] between SHX and non-hot extreme conditions [NSHX]) remains obscure. This study aims to shed light on the spatial-temporal pattern of SHX and the distinct SUHI responses to SHX throughout climatically diverse Chinese urban clusters using the seamless daily land surface temperature (LST) dataset. Our results provided evidence that Chinese urban clusters have experienced increasingly frequent, prolonged, and intensive SHX events regardless of climatic context, with stronger occurrences in summer and fall. Spatially, urban clusters in the northern regions have been subjected to more intensified SHX episodes compared to their southern counterparts. Furthermore, our findings revealed distinct δSUHII responses to SHX across China, demonstrating synergies between SUHI and SHX when SHX events constrained to urban areas whereas trade-offs when SHX isolated within rural settings. The magnitude of δSUHII depended upon the relative intensity of SHX between urban and rural settings, and heightened δSUHII generally associated with more intensified SHX events in urban than rural areas. Additionally, the explainable machine learning-based driver exploration showed that δSUHII was largely controlled by disparities in evaporative cooling (δET) between SHX and NSHX during the daytime, whereas during nighttime, it was predominantly governed by changes in surface heat storage, including urban-rural disparities in surface albedo (δABD) and impervious surface fraction (ISF). Facing the intertwined challenges posed by climate change and urbanization, it is imperative for cities to develop effective cooling strategies that emphasize enhanced evaporative cooling and minimized heat storage. These strategies are essential for safeguarding urban residents from potential synergistic effects between SUHI and SHX towards sustainable cities and human settlements.

Understanding the Magnification of Heatwaves over Spain: Relevant changes in the most extreme events

Heatwaves (HW) are a growing climate change-related risk affecting people's lives every year. A consensus exists about the magnification of this phenomena under climate change; however, less is known about their regional-to-local evolution characteristics' undermining appropriate policy and preparedness actions.This study investigates, from 1951 to 2019, regional changes in the occurrence and characteristics of HWs over peninsular Spain and the Balearic Islands (PSBI), highly exposed to climate change. State-of-the-art high-resolution observations provided by the SPAIN02 gridded data set are used for this purpose. Our results show an indisputable magnification of the HW phenomena but with relevant regional differences in the evolution of their characteristics. HWs occur two times more frequently inland, while most intense events take place in coastal areas. More extreme HWs in terms of frequency, maximum intensity, duration, and spatial extent are identified, rather than a progressive intensification in time affecting all HWs population. In the last decades, high frequencies are 8 times more likely, unprecedented high intensities are registered, the yearly maximum spatial extent is larger than ever and the probability to have a long-duration event has doubled. All of this is in the context of a longer HW season, increasing at a rate of about 4 days/decade, particularly in its onset. About 75% of the most severe and impactful HWs occurred after 1985. The most severe HWs, generally, are found not to be the most harmful to human health. This study highlights the importance of detailed knowledge of the spatiotemporal characteristics of HWs to accurately inform local practice for the effective design and implementation of adaptation plans.

Does the spatial configuration of urban parks matter in ameliorating extreme heat?

Extreme heat challenges the liveability of cities. Urban parks are popular as an efficient mitigative solution; however, uncertainties remain regarding whether and how the spatial configuration affects the effectiveness in practice. This paper tackles this issue by comparing the microclimatic amelioration potential of urban parks with the same green ratio in different spatial configurations. The study was conducted using microscale climate simulation in ENVI-met within three highly developed urban settings in Melbourne City, Australia, on 30th January 2009, during one of the most intense heatwave events. Hourly simulated data were extracted from all outdoor grids, encompassing nine heat-related indices, including meteorological variables, thermal comfort variables, and energy balance components. Linear mixed models were used to assess the effect of spatial configuration on improving outdoor thermal conditions. The results highlight a significant influence of spatial configuration in microclimate amelioration, and that these effects were context-specific, and no universally effective design emerged across locations, even within the same city. The findings underscore the necessity of considering other factors, such as surface cover characteristics and building configurations, and emphasise the importance of conducting site-specific simulations when introducing green infrastructure for heat mitigation.

A new European coastal flood database for low–medium intensity events

Abstract. Coastal flooding is recognized as one of the most devastating natural disasters, resulting in significant economic losses. Therefore, hazard assessment is crucial to support preparedness and response to such disasters. Toward this, flood map databases and catalogues are essential for the analysis of flood scenarios, and furthermore they can be integrated into disaster risk reduction studies. In this study and in the context of the European Coastal Flood Awareness System (ECFAS) project (GA 101004211), which aimed to propose the European Copernicus Coastal Flood Awareness System, a catalogue of flood maps was produced. The flood maps were generated from flood models developed with LISFLOOD-FP for defined coastal sectors along the entire European coastline. For each coastal sector, 15 synthetic scenarios were defined focusing on high-frequency events specific to the local area. These scenarios were constructed based on three distinct storm durations and five different total-water-level (TWL) peaks incorporating tide, mean sea level, surge and wave setup components. The flood model method was extensively validated against 12 test cases for which observed data were collated using satellite-derived flood maps and in situ flood markers. Half of the test cases represented well the flooding with hit scores higher than 80 %. The synthetic-scenario approach was assessed by comparing flood maps from real events and their closest identified scenarios, producing a good agreement and global skill scores higher than 70 %. Using the catalogue, flood scenarios across Europe were assessed, and the biggest flooding occurred in well-known low-lying areas. In addition, different sensitivities to the increase in the duration and TWL peak were noted. The storm duration impacts a few limited flood-prone areas such as the Dutch coast, for which the flooded area increases more than twice between 12 and 36 h storm scenarios. The influence of the TWL peak is more global, especially along the Mediterranean coast, for which the relative difference between a 2- and 20-year return period storm is around 80 %. Finally, at a European scale, the expansion of flood areas in relation to increases in TWL peaks demonstrated both positive and negative correlations with the presence of urban and wetland areas, respectively. This observation supports the concept of storm flood mitigation by wetlands.

Dynamics of Atmospheric-Driven Surface Currents on The Gulf of Cadiz Continental Shelf and its link with The Strait of Gibraltar and The Western Alboran Sea

Several studies about the coastal circulation over the continental shelf of the Gulf of Cadiz have been published in the last twenty years. One of the most studied features in these papers are the so-called Coastal Counter Currents (CCCs) which are located roughly between the 100 m isobath and the coastline and are directed westwards. Despite the considerable number of articles devoted to the analysis of this phenomenon, the actual along-coast extension and origin of these CCCs currently remain unclear.In the present study, different mechanisms are proposed to explain the development of these CCCs. They have been revised and discussed taking into account the latest findings from a recent analysis that utilized surface currents derived from High Frequency Radar (HFR) as well as numerical model simulations. The most interesting finding is that the most intense CCCs events are initiated on the coastal margin of the westernmost side of the Strait of Gibraltar, and they are extended further west of Cape Santa Maria. Furthermore, these intense and extensive CCCs seem to be triggered by the joint action of local winds over the Gulf of Cadiz and additional remote effects which are coming from (i) the wind forcing over the Alboran Sea and the easternmost side of the Strait of Gibraltar, and (ii) the Sea Level Atmospheric Pressure forcing over the Ligurian Sea (western Mediterranean Sea). In addition, the same forcing mechanisms are valid to explain the eastward intensification of the coastal currents.The most relevant feature of the hydrodynamic pattern originated by this combination of forcing agents is its quasi-geostrophic adjustment against the coast in the whole spatial dominion. In addition, these results offer a clear example of how important the effects of forcing in rather remote regions may be in defining the hydrodynamic patterns of certain oceanographic regions.

Back analysis of a building collapse under snow and rain loads in a Mediterranean area

Abstract. At the end of February 2018 the Mediterranean area of Montpellier in France was struck by a significant snowfall that turned into an intense rain event caused by an exceptional atmospheric situation. This rain-on-snow event produced pronounced damage to many buildings of different types. In this study, we report a detailed back analysis of the roof collapse of a large building, namely Irstea Cévennes. Attention is paid to the dynamics of the climatic event, on the one hand, and the mechanical response of the metal roof structure to different snow and rain loads, on the other hand. The former aspect relies on multiple sources of information that provide reliable estimates of snow heights in the area before the rain came into play and substantially modified the load on the roof. The latter aspect relies on detailed finite-element simulations of the mechanical behavior of the roof structure in order to assess the pressure due to snow and rain loading, which could theoretically lead to failure. By combining the two approaches, it is possible to reconstruct the most probable scenario for the roof failure before its full collapse. As an example of building behavior and vulnerability to an atypical rain-on-snow event in the Mediterranean area of France, this detailed case study provides useful key points to be considered in the future for a better mitigation of such events in non-mountainous areas.

Accumulation and migration of particulate trace metals by artificial flood event of the Yellow River: From Xiaolangdi reservoir to estuary

Reservoir construction increasingly alters the natural transport of riverine water and sediment to the sea, including the trace metals and other pollutants. In 2018, an intensive flood event and 412 million tons of sediment were released from the Xiaolangdi dam during the water-sediment regulation of Yellow River, one of the world's largest sediment releases. During the artificial flood event, the surface sediments in Xiaolangdi Reservoir (XLD) and the Yellow River estuary, suspended sediments at Lijin Station were collected. The concentration and speciation of particulate Cr, Ni, Cu, Zn, Cd and Pb, as well as the major geochemical composition were analyzed, to characterize the behaviors of the metals from the reservoir to estuary mixing zone, and elucidate the controlling mechanisms. The results showed that for exogenous phases, Cr, Ni, Cu and Zn were likely bound to the FeMn oxides, whereas Pb and Cd were mainly adsorbed in the carbonates. The trace metals in XLD were stably combined with fine-grained bottom sediments at high concentrations before dam release. During the delivery from reservoir to downstream channel, the binding of Cr, Ni and Cu with FeMn oxides was markedly enhanced. Pb and Cu showed obvious migration from carbonates to FeMn oxides, and Cd and Pb were even released into the water. The accumulation and migration of trace metals were controlled by the adsorption of fine-grained components, especially FeMn oxides and carbonates, and influenced by the oxidizing processes. After entering the estuary, the trace metals were greatly scavenged by reservoir-sourced fine particles, tended to bound to organic matter affected by the reducing environment. Our results suggest that dam regulation and artificial flood events will likely alter the existing forms and redox state of trace metals and the potential environmental effects should be considered.

Drought characteristics projections based on CMIP6 climate change scenarios in Syria

Study regionSyria Study focusThis study delves into predicting drought characteristics in Syria, focusing on their duration, frequency, and intensity. It utilizes a set of 13 models sourced from the latest CMIP6 dataset, encompassing two distinct SSP scenarios. To evaluate how well CMIP6 represents drought attributes in Syria, the research conducts a comparison with observed monthly climate data from CRU TS v4.06 and ERA 5, as well as the CMIP6 model ensemble outputs for the reference period (1970–2000). New hydrological insights for the regionThis study provides new hydrological insights for Syria. It reveals robust projections of increasing drought severity, frequency, and duration, particularly in the north and northeast arid and semi-arid regions, even under aggressive climate mitigation scenarios. Additionally, the study highlights that higher emissions scenarios are associated with more prolonged and intense drought events, potentially impacting even less vulnerable areas. These findings emphasize the urgent need for drought adaptation and mitigation measures, as well as improved water resource planning, in order to address the changing hydrological landscape of the region. Furthermore, it underscores the long-lasting effects of drought on ecosystem recovery, which may span several decades.

Effects of freshet events on early life stages of fish and macroinvertebrates in a highly turbid estuary of Iberian Peninsula

The present study investigates effects of three different types of freshet events (varying in intensity, duration, and period of discharge) on the early life stages of fish, macroinvertebrates inhabiting in the water column, and the environmental conditions within the hiperturbid estuary of the Guadalquivir River. Freshet events compressed the salinity gradient and increased turbidity; during the most intense freshet event, the oxygen concentration also decreased. These environmental changes had significant effects on the abundance and distribution of aquatic organisms, reducing the nursery area from 40 km upstream to 20 or 10 km, depending on the freshet. Recovery of physicochemical conditions was relatively rapid (within one or two weeks) for less intense freshets, while the most intense event showed only partial recovery even one month later. Biological responses varied among species and time periods. Pelagic species (e.g., anchovies) were flushed out of the estuary. The populations of these species can show a posterior reintroduction and a recovery to levels similar to before the freshet, or a nonrecovery, probably depending on larval supplied from the offshore stock. In contrast, benthic and estuarine species (e.g., gobies, mysids), were just displaced downstream during the freshets. In the most intense freshet event, which occurred before the high recruitment period of these species (early spring), their abundances increased significantly, exceeding the levels of normal years (without freshets). This suggests that, depending on the intensity and the period in which the freshet occur, they could act as attraction signals for certain species. In general, estuarine and benthic species, such as gobies and other macroinvertebrates, coped better with freshets than pelagic marine migrant species, such as anchovies. However, the estuary and its estuarine organisms showed high resilience to environmental fluctuations.

Irish surface water response to the 2018 drought

Intense weather events are projected to increase as a consequence of climate change. The summer 2018 drought in Europe impacted human health, ecosystems, and economic prosperity. Even locations with an abundance of fresh water, like Ireland, faced water restrictions due to depleted supplies. To characterize the effect of the 2018 drought on Irish rivers, we collected surface water samples from rivers across the island at the drought onset and termination. We analyzed samples for stable water isotopes δ18O and δ2H and calculated the fraction of evaporation from river groundwater and precipitation inflow (E/I) of rivers. We extended river δ18O and δ2H analysis to 2020 for rivers in two catchments, Corrib and Shannon, to investigate how Irish river systems respond to high precipitation events, and the role of loughs (lakes) in the system. River δ18O and δ2H values showed progressive depletion from west to east in response to precipitation depletion from airmasses arriving off the Atlantic Ocean. From onset to termination of the 2018 drought, river δ18O and δ2H values were enriched and the calculated E/I value increased for most rivers. D-excess were negatively correlated with E/I value, providing support for E/I calculations. Extended analysis of loughs along the Corrib and Shannon river systems showed that lough Corrib consistently induced isotopic enrichment, while loughs in the Shannon catchment inconsistently caused isotopic enrichment. Both systems exert control over river isotopic composition in hydrologic extremes. Findings promote additional research in hydrologic patterns in response to increasing frequency of floods and droughts.

Groundwater recharge sources and processes in northwest India: Evidence from high frequency water isotope observations

Study regionBist-Doab, Punjab, northwest India. Study focusWater isotopes and specific electrical conductivity (SEC) are used in this paper to investigate groundwater recharge sources and processes in a catchment with a history of high groundwater abstraction for irrigation and canal irrigation. High frequency (every 10 days) samples for water stable isotope analysis (δ18O and δ2H) were sampled from a dense network of shallow (<50 m) and deep (>100 m) hand pumps and tube wells in Bist-Doab, northern Punjab between 2009 and 2014. New hydrological insights for this regionThe study indicates that groundwater recharge is dominated by meteoric sources from high intensity events. However, in a small proportion of sites located in close proximity to some canals and rivers have significant surface water inputs. Isotope observations indicate rapid changes in groundwater recharge sources linked to post-monsoon pumping and seasonal connectivity to surface water inputs, even at some deep sites. Rapid changes are likely linked to poor well integrity, highlighting the risk to groundwater sources from surface water ingress. Shallow groundwaters had significantly higher SEC compared to deeper groundwater observations (p = 0.0002). Overall groundwater SEC is still relatively low (<2000 μS/cm). However, based on previously published mean residence time of (<50 years) in shallow groundwater the high rate of change in salinity at some sites (2.5–10% per year) is of potential concern.