Search Results (228)

Fluvial terraces represent important geomorphological archives for reconstructing the effects of climatic fluctuations, tectonic activity, and base-level changes during Quaternary times. This study investigates the geomorphological and stratigraphic evolution of the Bradano, Basento, and Salandrella River systems within the Bradanic Foredeep of southern Italy, by means of field observations, geomorphological mapping, aerial-photo interpretation, and GIS analyses. Four relative morphostratigrafic orders of Pleistocene fluvial terraces (T₁–T₄) have been identified and correlated across the three drainage basins. No absolute ages are available for these surfaces. The terraced deposits consist of alternating sandy and conglomeratic bodies recording multiple episodes of incision and/or aggradation overlaying erosional surfaces developed on Pre-Quaternary bedrock. Morphometric analyses revealed significant differences in terrace elevation and relative height above the modern channels, among the three investigated basins. The Salandrella basin preserves some of the highest terraced remnants, a pattern compatible with a possible tectonic contribution related to its proximity to the Apennine mountain front. Conversely, the Basento and Bradano basins evidenced a greater influence of lithological conditions, sediment supply, and climate-controlled variations in fluvial dynamics. The results indicate that the evolution of the staircase fluvial terraces reflects the combined influence of glacio-eustatic sea-level fluctuations, Quaternary climatic oscillations, local geological controls, and a possible contribution from regional tectonic deformation. The regional correlation of terraced surfaces highlights the role of the external forcing in shaping landscape evolution, while local differences emphasize the importance of catchment-scale controls within the Bradanic Foredeep. Full article

The obligate mixotroph Mesodinium rubrum significantly impacts coastal ecosystems, yet its population control in oligotrophic waters remains unclear. Integrating field observations from Coast of Sanya (South China Sea) with laboratory nutrient manipulation, we investigated how dissolved inorganic nutrients and prey availability regulate cell cycle progression, using biovolume as a proxy for cycle transitions. Nutrient starvation arrested cells at the small (newly divided) stage. Inorganic replenishment triggered rapid somatic growth and consistent diel biovolume oscillations, expanding in light and shrinking in darkness. However, without cryptophyte prey, cells failed to progress beyond the medium (actively growing) stage and could not accumulate into the large (pre-division) size class, revealing a decoupled regulatory mechanism. Dissolved inorganic nutrients drive cell size expansion (somatic growth), whereas prey-derived organelles serve as a critical prerequisite for division. Field data confirmed that the virtual absence of cryptophytes in Sanya waters restricts M. rubrum to consistently low levels. Our findings demonstrate that population dynamics of this specialist mixotroph transcend traditional nutrient-driven paradigms, underscoring the irreplaceable role of prey in sustaining photosynthetic metabolism and triggering population expansion in oligotrophic systems. Full article

Tsunami hazards in the Bay of Naples are primarily driven by submarine landslides, intense seismic activity, and volcanic phenomena from nearby systems like Vesuvius and the Campi Flegrei caldera. While localized historical tsunamis have occurred, they are generally rare events. Key tsunami sources include submarine landslides, volcanic eruptions, and seismicity. In this paper we provide a review of the tsunamis in Naples Bay within a general framework of Mediterranean tsunamis based on a literature review. Underwater avalanches, particularly around the steep slopes of the Dohrn Canyon and Ischia, are considered a primary localized threat. Scientific models indicate that a major collapse (like past events like the Ischia debris avalanche) could generate significant waves that could cross the bay in minutes. Explosive eruptions where magma meets seawater (such as PDCs—pyroclastic density currents) can displace water violently. This was famously documented during the AD 79 eruption of Mount Vesuvius, which created submarine ash fans and tsunami waves in the gulf. Earthquakes related to bradyseism in the Campi Flegrei or regional faults can also trigger sea level oscillations or localized tidal waves. Among the historical modeled events, we focus on the A.D. 79 eruption and on the 1343 Naples tsunami. The numerical simulations are revised. Depending on the source, the modeled waves vary from minor oscillations to heights of up to 6 m in canyon areas or over 20 m in nearby islands like Ischia. Full article

This study presents a multivariate spatio-temporal clustering framework to characterise joint wind–wave regimes across European seas using the fifth-generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5; 1979–2014). Seasonal and annual statistics of significant wave height, mean wave period, wind speed, and wave/wind direction were computed at 0.5° resolution. Principal component analysis was used to reduce dimensionality, retaining 30 components that captured 99% of the variance. K-means clustering was then used to identify nine coherent dynamical regimes with persistent spatio-temporal signatures. These regimes were grouped into open-ocean, transitional, and enclosed/semi-enclosed categories based on internal variability, directional spread, and geographic exposure. Open-Atlantic regimes are found to be energy-rich, exhibiting clear December–February maxima in significant wave height ($H_s$), mean wave period ($T_{02}$), and 10 m wind speed ($W_{s10}$); enclosed and semi-enclosed basins show lower amplitudes and reduced variability, while transitional shelves and the southern Mediterranean display intermediate conditions, characterised by moderate $T_{02}$ levels and seasonal rotation of wave and wind directions, reflecting a mixed influence of locally generated seas and remotely forced swell. Dispersion analysis highlights a clear Atlantic–Mediterranean partition, with transitional shelves forming a dynamical bridge between open-ocean and enclosed basins. Teleconnection analysis shows that the North Atlantic Oscillation and Arctic Oscillation dominate Atlantic regimes, while the Scandinavia, East Atlantic, and Polar/Eurasia patterns modulate variability and directional persistence in transitional and enclosed seas. The classification defines a climatological framework of European wind–wave conditions and establishes a practical basis for renewable energy assessment, engineering design, and long-term change analysis, with methods transferable to other basins. Full article

East China is a global hotspot for landfalling tropical cyclones (TCs). While previous studies have extensively examined the influence of El Niño–Southern Oscillation (ENSO) on TC activity, whether and how ENSO alters the spatial organization of precipitation in landfalling TCs remains insufficiently understood. Using high-resolution satellite precipitation observations and ERA5 reanalysis data, this study investigates the heterogeneous responses of landfalling TC precipitation over East China to different ENSO phases. Composite analyses indicate ENSO-associated differences in TC precipitation at both regional and storm-relative scales. At the regional scale, positive composite precipitation differences occur over Fujian, southern Zhejiang, and Taiwan during El Niño years, whereas negative differences occur in parts of northern East China relative to La Niña years. At the storm-relative scale, mean outer-rainband precipitation was estimated to be 26.02% higher during El Niño years; however, the storm-level bootstrap 95% confidence interval included zero, indicating uncertainty associated with the limited number of independent TC events. Precipitation during La Niña years was relatively more concentrated within the inner-core region. Mechanistic diagnostics show that the El Niño composite is associated with differences in thermodynamic and dynamic conditions, including higher low-level cyclonic vorticity, upper-level divergence, ascent, and anomalous steering flows over southern East China and adjacent seas. TC-centric analysis further indicates that higher moisture supply and dynamic lifting coincide with the outer-rainband precipitation contrast during El Niño years. These findings suggest that ENSO is associated with spatially heterogeneous and structurally distinct responses of landfalling TC precipitation over East China, providing a diagnostic basis for understanding ENSO-related differences in regional TC precipitation risk. Full article

Regional sea-level trends derived from satellite altimetry deviate substantially from the global mean, but the relative roles of externally forced change and internally generated climate variability remain difficult to separate from the short satellite record. Here, we examine the 32-year Data Unification and Altimeter Combination System (DUACS) gridded multi-mission satellite altimetry product (January 1993–December 2024) together with 100 100-year samples from an unforced Community Earth System Model (CESM) pre-industrial control simulation. Empirical orthogonal function (EOF) analysis of satellite sea-level anomalies reveals a leading mode explaining 10.9% of total variance, with an Interdecadal Pacific Oscillation (IPO)-like dipolar pattern and high correlation with the IPO index (r = 0.92). A similar IPO-like mode appears consistently in the unforced CESM samples. Because previous large-ensemble studies indicate that the externally forced sea-level response is generally broader and structurally distinct from this dipolar internal mode, this agreement supports the interpretation that the satellite-observed leading pattern is strongly consistent with internally generated variability, although a partial forced contribution, particularly in the tropical Pacific, cannot be excluded. Based on CESM simulations, the empirical contribution of internal variability to regional trend uncertainty decreases approximately inversely with record length. The resulting location-specific estimate can be scaled by the local EOF amplitude and is largest in regions where the dominant internal-variability mode has large amplitudes, including the western tropical Pacific and Indian Ocean. However, this estimate represents only the internally generated component inferred from a single unforced CESM simulation. It does not include DUACS mapping errors, inter-mission calibration uncertainty, geophysical correction uncertainty, glacial-isostatic-adjustment-related bias, or uncertainty in the forced sea-level response. Thus, this study provides a model-based framework for estimating the internal-variability contribution to regional sea-level trend uncertainty, rather than a formal detection-and-attribution separation or a complete uncertainty bound for satellite-altimeter-derived regional sea-level trends. Full article

The Atlantic Meridional Overturning Circulation (AMOC), as the core component of the global thermohaline circulation, exerts a profound influence on the Northern Hemisphere climate. Recent observations show that AMOC intensity has weakened by approximately 15% over the past 40 years, yet the traditional theoretical framework dominated by the North Atlantic Oscillation (NAO) cannot fully explain its spatial heterogeneity. This study systematically quantifies the independent driving mechanism of the Arctic Oscillation (AO) on AMOC decline for the first time by integrating multi-source reanalysis data (ERA5, ORAS5) and CMIP6 model output. Theoretical analysis shows that the AO positive phase regulates the stability of AMOC through two coupled pathways: (1) anomalous wind stress curl leads to the weakening of Ekman suction in the subpolar seas (contribution: 42 ± 6%), inhibiting deep-water formation in the Labrador Sea; and (2) increased freshwater flux through the Fram Strait triggers a negative salinity advection feedback, which leads to shoaling of the North Atlantic high-latitude mixed layer by up to 30 m. The cross-scale interaction reveals that the AO interannual variability amplifies the modulation of the AMOC interdecadal trend. This amplification occurs through the positive feedback of sea-ice albedo. When AO and NAO are locked in opposite phases (AO+/NAO−), the AMOC weakening rate increases to 1.8 Sv/decade (1 Sv = 10⁶ m³/s), whereas the same-phase negative condition (AO−/NAO−) yields a moderate decline of 0.5 Sv/decade. This mechanism corrects the underestimation of the traditional wind-driven circulation theory for high-latitude processes and provides a physical attribution for the CMIP6 models’ systematic underestimation of AMOC sensitivity. The study further constructs the “Arctic Oscillation–subpolar basin–AMOC” three-pole coupling theoretical model and confirms that the Arctic amplification effect enhances the AO–AMOC coupling strength by a factor of 2.3 over the full study period (1979–2020; R² = 0.71, p < 0.01), with an even more pronounced enhancement of 2.1 times during the recent two decades (2000–2020; R² increased from 0.28 to 0.59). These findings have direct implications for coastal risk assessment, as AMOC weakening may accelerate sea-level rise along the North American East Coast and increase the frequency of extreme winter storm surges in European coastal areas. The results provide a dynamic basis for IPCC climate risk assessment and have practical application value for the early warning of extreme cold-wave events. Full article

Arctic shipping lanes are gradually opening, creating an urgent demand for unmanned surface vehicles (USVs) capable of safe and efficient navigation in drifting-ice environments. However, dense, highly dynamic sea ice poses significant challenges for existing obstacle-avoidance approaches. This study proposes a dynamically weighted hybrid obstacle avoidance algorithm integrating an improved VO module and an enhanced APF module. The optimized VO method refines the velocity sampling strategy and incorporates DCPA/TCPA-based risk screening to eliminate high-risk candidate velocities. The improved APF method introduces adaptive parameter regulation, virtual-target-based local minimum escape, and historical-velocity-driven oscillation suppression. Furthermore, a real-time dynamic weighting mechanism is designed to balance the contributions of the VO and APF modules according to the instantaneous environmental risk level. Extensive simulation experiments demonstrate that the proposed algorithm achieves reliable collision avoidance performance, high navigation efficiency, and strong environmental adaptability for USVs operating in dynamic Arctic drifting-ice environments. Full article

In the boreal winter of the Northern Hemisphere, a weakening of the surface Indonesian throughflow (ITF) is commonly observed. The intraseasonal mechanism of the weakening, namely, the impact of the atmospheric Madden–Julian Oscillation (MJO), is well-known and has been extensively studied. However, a significantly low volume transport of ITF (<100 m in depth) was also observed in the Makassar Strait during the traverse of tropical cyclones (TCs). The observed transport decrease is 0.31 Sv (1 Sv = 10⁶ m³/s) on average, which is ~70% of the estimated influence of the MJO. The time scale of the incurred variation is up to 30 days, comparable to the time of 20–90 days caused by the MJO. The winds in the TC circulation have a major impact on the Makassar Strait’s ITF transport reduction. Numerical experiments reveal that the reduction is due to the along-strait sea level anomaly (SLA) variability that is forced by the winds from the upstream region. The mechanism involves the propagation of coastal Kelvin waves along the Sulawesi Sea generated by the TCs and is confirmed by theoretical analysis. Based on the numerical experiments, this mechanism contributes ~40% to the total ITF transport reduction, while the large-scale guiding circulation surrounding the TCs may contribute to the remaining ITF transport reduction. These results support that TCs are also important forcing components in the intraseasonal variation in surface ITF. Full article

The crushing failure of sea ice is a critical design issue for polar offshore structures and ship structures because ice-induced loads may generate pronounced local damage and dynamic responses. Accurately modelling this process remains challenging because ice crushing involves localized fragmentation, crack propagation, rubble accumulation, and repeated contact release. This paper presents a controlled numerical sensitivity study of level-ice crushing against a vertical structure using a coupled LS-DYNA framework that combines the Structured Arbitrary Lagrangian–Eulerian (S-ALE) formulation with the Cohesive Element Method (CEM). The study focuses on a benchmark-scale indentation configuration and examines how mesh topology, mesh size, and imposed indentation velocity affect the predicted fracture morphology and load-time histories. The results show that random triangular meshes better reproduce stochastic fragmentation and lateral flaking than regular triangular or quadrilateral meshes, while finer meshes reduce excessive load oscillations and provide more stable force histories. The velocity study indicates a transition from gradual crushing and fragment retention at lower velocities to more rapid brittle chipping and stronger dynamic fluctuations at higher velocities. A benchmark-level comparison with published ice-indentation simulations shows that the predicted peak line load is of the same order of magnitude as reference results. The proposed framework is therefore useful for investigating numerical sensitivities and failure-mode trends in ice-crushing simulations, although final design-load application requires further calibration and formal mesh-independence assessment. Full article

The “New Arctic” regime represents a prominent climatic feature of the Arctic Ocean under global warming, characterized by persistently low summer sea ice extent, a marked reduction in sea ice thickness, and an expansion of open water areas at high latitudes. As a key indicator of the Arctic sea ice system, the spatiotemporal evolution of sea ice thickness and its underlying driving mechanisms remain incompletely understood. Using reanalysis datasets and remote sensing observations, this study identifies major abrupt shifts in Arctic sea ice thickness under the New Arctic regime, reveals the spatiotemporal distribution characteristics of winter sea ice thickness, and examines the driving factors from both thermodynamic and dynamic perspectives. The results show that the evolution of Arctic sea ice thickness can be divided into three phases: a high-level period during the “Traditional Arctic” (1979–1992), a rapid thinning period during the New Arctic transition (1993–2012), and a low-level stabilization period in the New Arctic regime (2013–2023). The first EOF mode of winter sea ice thickness depicts a spatially consistent thinning pattern across the entire Arctic, with the most significant reduction occurring in the multi-year ice regions north of the Canadian Arctic Archipelago and Greenland. The second EOF mode exhibits an out-of-phase variation between the Atlantic and Pacific sectors of the Arctic, accompanied by a shrinking amplitude and weakened regional oscillations. The coupling between surface air temperature and sea ice thickness displays distinct phase dependence: their negative correlation is strongest during the transition period (r = −0.78, p < 0.001) but becomes statistically insignificant in the New Arctic regime. Sea ice motion speed exhibits an overall accelerating trend, which extends from the marginal seasonal ice zones toward the high-latitude multi-year ice regions, accompanied by a notably enhanced sensitivity of sea ice motion to wind forcing. Sea ice volume flux through the Fram Strait is primarily controlled by ice motion speed, whose contribution to the flux is approximately 2.6 times that of ice thickness. The recovery of ice drift speed offsets the thinning of sea ice cover, leading to a partial rebound in volume flux during the New Arctic steady state. This study identifies the evolutionary patterns and drivers of Arctic sea ice thickness under the New Arctic regime, providing a scientific basis for further understanding the changes in the Arctic climate system and associated air–sea ice interactions. Full article

The significant interannual variability in Madden–Julian Oscillation (MJO) intensity remains incompletely understood. Empirical orthogonal function (EOF) analysis reveals that the first three leading EOF modes of the annual mean MJO intensity are significantly correlated with the Quasi-Biennial Oscillation (QBO), Eastern Pacific El Niño-Southern Oscillation (ENSO), and Central Pacific ENSO. Focusing on the distinct EOFs related to three key tropical interannual variabilities, we conduct an investigation into the potential governing processes through which the changes in background mean states impact MJO intensity based on the MJO moisture mode theory. Observations suggest that the accumulation of moist static energy (MSE) during MJO moistening phases and its dissipation during drying phases play a crucial role in regulating MJO amplitude. At the interannual timescale, regions characterized by positive EOF values display positive (negative) MSE tendency anomalies during MJO moistening (drying) phases, leading to amplified MSE accumulation (dissipation) throughout the MJO lifecycle and subsequently facilitating an increase in MJO amplitude. Conversely, regions with negative EOF values exhibit opposing trends. Further analysis reveals that these MSE tendency anomalies are mainly associated with the zonal advection term, which is influenced by interannual changes in the background mean MSE and low-level winds. The spatial pattern of the background mean MSE is strongly linked to sea surface temperature (SST) anomalies, with low-level background winds aligning well with the horizontal gradients of SST anomalies. Full article

Interannual variability of sea level anomalies (SLA) in the South China Sea (SCS) is significantly influenced by large-scale climate modes; however, their temporal evolution and interdecadal modulation mechanisms remain insufficiently understood. Based on observational records and ERA5 reanalysis data spanning 1980–2022, this study employs a Bayesian Dynamic Linear Model (DLM) to quantify the time-varying impacts of El Niño-Southern Oscillation (ENSO) on interannual SLA variability across different subregions of the SCS and further investigates the modulation effect of the Pacific Decadal Oscillation (PDO) background state. The results indicate that ENSO is a key climatic driver of interannual SLA variability in the SCS; nevertheless, its influence exhibits pronounced non-stationarity, with dynamic regression coefficients showing clear phase-dependent fluctuations throughout the study period. The northern and eastern subregions display stronger responses to ENSO forcing, whereas the southern and western subregions exhibit relatively weaker signals. The negative phase of the PDO enhances the ENSO-SLA relationship, while the positive phase weakens it, with sign reversals occurring in certain subregions. Correlation analyses further suggest that ENSO influences SLA primarily through wind stress anomalies induced by sea level pressure (SLP) gradients, which regulate Ekman transport, whereas the PDO exerts an indirect effect mainly by modifying the large-scale background circulation structure. Full article

Escalating climate volatility, particularly the El Niño/Southern Oscillation (ENSO), poses severe operational and financial risks to corporate sustainability in the energy sector. However, quantitative evidence regarding how macro-level climate shocks transmit to micro-level operational performance remains scarce. Integrating dynamic capability and social network theories, this study analyzes a panel of 103 Chinese listed energy firms (2005–2022) using System GMM, mediation, and moderation models. The results indicate that ENSO intensity significantly impairs performance; specifically, a 1 °C rise in sea surface temperature anomalies decreases firms’ return on assets (ROAs) by 0.142%. We identify supply chain resilience as a critical strategic mechanism for climate adaptation, where response capacity acts as the dominant mediating channel, while recovery capacity functions as an independent compensatory mechanism. Conversely, supply network complexity—across horizontal, vertical, and spatial dimensions—amplifies the negative impact of climate disruptions by hindering resource mobility. Heterogeneity analysis reveals that state-owned enterprises exhibit stronger institutional resilience, and firms in southern regions partially offset impacts through hydropower advantages. This study bridges climate science with operations management, offering strategic guidance for managers to configure resilient, sustainable supply chains capable of withstanding environmental turbulence. Full article

Oil and gas exploration conducted in the main fault zone of the Fuman Oilfield has yielded large-scale and high-production results. Against this background, the non-fault zone has emerged as a new domain for oil exploration endeavors. Nevertheless, the establishment of a unified sequence division scheme for the study area remains unachieved, primarily constrained by two key factors: first, the high costs associated with ultra-deep high-density coring operations; and second, the inconspicuous response characteristics exhibited by logging curves. This absence of a standardized scheme has further impeded the progress of oil and gas exploration in the non-main fault inter-region within the study area. Consequently, the present study is based on multi-source data, including seismic data, logging data, and field outcrop data. Magnetic susceptibility measurements from the cement plant section and natural gamma-ray logging data from the Yangjikan section were systematically analyzed to establish cyclostratigraphic frameworks. A sedimentary noise model (SNM) was employed to reconstruct Holocene sea-level fluctuations, enabling precise sequence stratigraphic subdivision within the Fuman Area. Results demonstrate that the Middle-Lower Ordovician Yijianfang–Penglaiba Formations retain robust astronomical cyclicity, validated by high-fidelity orbital forcing signals. Notably, the DYNOT (Dynamic Noise After Orbital Tuning) model effectively decouples orbital-driven sea-level oscillations from local depositional noise, offering a novel approach for sequence boundary identification. This methodology reveals a hierarchical sequence architecture comprising four third-order sequences and 11 fourth-order sequences within the Yijianfang–Penglaiba Formations. Such a framework provides critical insights into facies distribution patterns and non-fault-controlled exploration potential in the Fuman Basin. Full article