Anomalous Increase Research Articles

Relation among Oxygen Stoichiometry, Structure, and Co Valence and Spin State in Single-Layer La2-xAxCoO4±δ (A = Ca, Sr) Perovskites.

We have investigated the role of oxygen stoichiometry and structural properties in the modulation of Co valence and spin state in single-layer La2-xAxCoO4±δ (A = Sr, Ca; 0 ≤ x ≤ 1) perovskites as well as the interplay between their local structural properties and the magnetic and charge-ordering phenomena. We show the results of high angular resolution powder X-ray diffraction and Co K-edge X-ray absorption and emission spectroscopy experiments on polycrystalline and single-crystal samples. The different doping-induced changes in the Co valence and spin state by Ca (or Sr) substitution can be understood in terms of the evolving oxygen stoichiometry. For Ca doping, the interstitial oxygen excess around the La/Ca atoms in underdoped samples is rapidly lost upon increasing the Ca content. The creation of oxygen vacancies leads to the stabilization of a mixed-valence Co2.5+ independently of the Ca content. In contrast, Sr substitution leads to almost stoichiometric samples and a lower oxygen vacancy concentration, which allows higher mixed-valence states for Co up to Co2.9+. The Co mixed-valence state along the two series is fluctuating between two valence states, Co2.4+ as in La2CoO4.2 and Co2.9+ as in LaSrCoO3.91, that become periodically ordered for the charge-ordered phases around the half-doping. The X-ray emission derived spin states agree well with the Co fluctuating mixed-valence state derived from X-ray absorption spectroscopy on consideration of a distribution of high-spin Co2+ and low-spin Co3+. Furthermore, there is no quenching of the orbital contribution for the high-spin Co2+, as concluded from a comparison with macroscopic magnetization measurements. Doping holes are mainly located in the ab plane and have a strong oxygen 2p character. The major lattice distortions, which are different for Sr and Ca doping, occur along the c axis, where changes in the oxygen stoichiometry take place. Moreover, charge-order transitions are clearly shown from the anomalous increase of the c lattice parameter with an increase in the temperature above 500 K but there is no signature for a temperature-dependent spin-state transition.

Dynamic flow stress of pure polycrystalline aluminum: Pressure-shear plate impact experiments and extension of dislocation-based modeling to large strains

The dynamic thermo-mechanical behavior of pure aluminum has attracted renewed interest lately due to experimental observations of an anomalous increase in Hugoniot Elastic Limit (HEL) at incipient plasticity and elevated temperatures in polycrystalline pure metals. In context of current dislocation-mediated plasticity models for metals, this increase in dynamic strength is indicative of a transition in the rate controlling mechanism for dislocation glide from being thermally assisted to phonon-drag restricted due to increase in phonon viscosity at elevated temperatures. Though these studies have helped to shed light on these important mechanisms operative in FCC metals at incipient plasticity, the extent to which they contribute to flow stress, particularly at larger strains, remains unclear. In the present study, we address these questions through a combined experimental and modeling effort focused on investigating the evolution of dynamic flow stress in polycrystalline aluminum using experimental data gathered from a series of combined pressure-and-shear plate impact (PSPI) experiments designed to reveal the flow stress of pure aluminum at strain rates ~ 105/s, plastic strains of up to 40% and temperatures ranging from room to 866 K. In all cases, the flow stress of aluminum, as inferred from the measured transverse particle velocity histories at the free surface of an elastic tungsten carbide target plate, reveals saturation with increasing plastic strains at stress levels that decrease with increasing test temperatures. Numerical simulations are performed to correlate the experimentally observed temperature and strain rate dependence of flow stress at small and large plastic strains using the Austin-McDowell dislocation-mediated plasticity model parametrized to normal plate impact experiments conducted in an earlier study by Zaretsky and Kanel (2012). Extensions to the model are made to better represent dynamic behavior of pure aluminum at larger plastic strains as observed in elevated temperature split Hopkinson Pressure bar (SPHB) experiments of Samanta (1971) and Lindholm and Yeakly (1965), and the combined pressure-and-shear plate-impact experiments conducted in the present study. The main theoretical extension to the Austin-McDowell model made in this paper is the introduction of a new rate- and temperature- dependent dynamic recovery function, which can potentially allow for an effective reduction in the rate of accumulation of dislocations at large plastic strains. The numerical predictions of the revised and re-calibrated plasticity model are brought into agreement with the experimental observations, correlating sufficiently well with dynamic yield stress at incipient plasticity and the flow stress levels at larger plastic strains, plastic strain rates in the range 103 – 106 /s, and elevated temperatures up to near melt. The model, in concert with the experimental measurements, suggests that at incipient plasticity the rate governing mechanism for plastic flow is phonon-drag restricted dislocation glide, whereas, at higher magnitudes of plastic strain, it transitions to stress-assisted thermally activated glide. The transition between these two rate governing mechanisms is controlled by the evolution of dislocations throughout the deformation process.

Study of the low and mid-latitude ionospheric response to the geomagnetic storm of 20th December 2015

The ionospheric response over the low and mid-latitudes along the $78^{\circ}\pm 3^{\circ}$ E longitude sector is studied for the 20th December 2015 geomagnetic storm. The global positioning system (GPS) derived total electron content (TEC) over mid & low-latitude stations and also an ionosonde observation of the F2 layer critical frequency over a mid-latitude station are analyzed. On the day of storm (20th December) the interplanetary magnetic field turned southward around 0330 UT and reached to its minimum value around −20 nT. SYM-H index started to decline at the same time and attained to its minimum value of about −180 nT at around 2330 UT after a very long main-phase duration (∼20 hours). During the storm’s main phase, a large TEC variation is observed for both the locations which have been attributed to the prompt penetration electric field (PPEF). The uniqueness of the observed TEC variation lies in the fact that while over the mid-latitude the TEC returned to its quiet time variations after the recovery phase, the enhancement in TEC over low-latitude has been observed even after two days (anomalous increase on 22nd December) of the storm which indicates the absence of disturb dynamo electric field (DDEF) for low-latitude over 78°E longitude. The thermospheric O/N2 data obtained both from, observations as well as CTIPe model simulation are in good agreement with the observed TEC variation except for the 22nd December over the mid-latitude location. This anomalous behavior on 22nd December over low-latitude could be due to some local dynamics or the transport of plasma by the background seasonal and storm time meridional winds over the studied region.

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In the frequency range from 30 Hz to 1 MHz, the dielectric properties of polycrystalline fullerite films with a thickness of about 300 nm, which are part of p-type Si / C60 / InGa structures, were studied under the influence of constant electric fields with a strength of up to 33 MV / m. It was found that at negative polarity of the InGa electrode, when the injection of electrons from the metal into the fullerite is facilitated, at frequencies less than 1000 Hz, an anomalous increase in the electrical capacity of the sample is observed, while the capacitance at a low frequency exceeds the capacitance at a high frequency by more than 1000 times. An explanation for this effect is proposed.

Failure of Jet Engine Fuel Control Unit Originated by Corrosion of Cadmium Coating

Since 2015 the barometric fuel units of the aircraft jet trainer fleet were featured by an anomalous increase in the rate of failures, all caused by the presence of debris in the jet fuel system. Cadmium and sulfur based composition of debris observed in the fuel control unit revealed that they were originated by a reaction of jet fuel’s sulfur compounds with cadmium protection coating of few components in the unit. Analysis carried out on jet fuel samples did not find any value out of the specification and therefore further investigations were conducted on the cadmium coating process. Two fuel pumps were examined: a degradation of cadmium coating was observed on every components of both pumps, proportionally to their flight hours.A brown-yellow gelatinous deposit was found into the pumps components, mainly composed by hydrocarbons, cadmium, sulfur and carboxylic salts. The investigation on the cadmium surface treatment process revealed the anomalous absence of the chromate conversion coatings: it was responsible of cadmium availability in the fuel flow, causing the cadmium plating detachment that finally resulted in the solid particles production.

Understanding how water models affect the anomalous pressure dependence of their diffusion coefficients

The self-diffusion coefficient of water shows an anomalous increase with increasing hydrostatic pressure up to a broad maximum (PmD) near 1 kbar at 298 K, which has been attributed to pressure effects on the tetrahedral hydrogen bond network of water. Moreover, the ability of a water model to reproduce anomalous properties of water is a signature that it is reproducing the network. Here, water was simulated between 1 bar and 5 kbar using three water models, two four-site (with all charges in the molecular plane) and one single-site multipole (which accounts for out-of-molecular plane charge), that have reasonable pressure-temperature properties. For these three models, the diffusion coefficients display a maximum in the pressure dependence and the radial distribution functions show good agreement with the limited experimental structural data at high pressure that are available. In addition, a variety of properties associated with the network are examined, including hydrogen bond lifetimes and occupancies, three-body angle distributions, and tetrahedral order parameters. Results suggest that the initial increasing diffusion with pressure is because hydrogen bonds are distorted and thus weakened by pressure, but above PmD, the hydrogen bonds are weakened to the point it behaves more like a normal liquid. In other words, the PmD may be a measure of the angular strength of hydrogen bonds. In addition, since the four-site models over-predict the values of PmD while the multipole model under-predicts it, out-of-plane charge may improve four-site models.

Electrical Conductivity and Dielectric Permittivity of Directly Doped LiNbO3:Zn,Mg Crystals in the Temperature Range 450–900 K

The electrical conductivity σ of a series of multidomain LiNbO3:Zn,Mg crystals prepared via direct doping in the composition ranges ~1 ± 0.02 mol % MgO and ~2.8–4.6 mol % ZnO has been shown to undergo a sharp increase at T* ≈ 800 K, accompanied by anomalies in temperature dependences of their dielectric permittivity, e(T). The largest increase in their static bulk conductivity near T* has been observed in a narrow composition range (≈1 ± 0.02 mol % MgО and ≈3.9–4.3 mol % ZnO). Above T*, the LiNbO3:Zn,Mg crystals have an activation enthalpy for ionic conduction (Ha ≈ 1.76–2.15 eV) and enthalpy of transport (Hm ≈ 1.66–2.06 eV) unusually high for cation conductors, whereas below T* both quantities are characteristic of Li+ ion conduction in LiNbO3 crystals (На ≈ 1.15–1.35 eV and Нm ≈ 1.0–1.1 eV). The anomalous increase in Ha and Hm is caused by the formation of associated vacancies (divacancies) and correlated pair hopping of Li+ ions above T*.

Development of the Vortex Flow Structure on the Leeward Side of an Axisymmetric Body in Supersonic Free Stream at an Angle of Attack

The results of the numerical investigation of supersonic flow past a sharp slender body at an angle of attack are given with reference to the example of an axisymmetric cylindrical body with a conical nose. Separated and vortex structures developed at various angles of attack are identified. The effect of anomalous increase in pressure on the leeward side is explained.

Defect-free metallization of through-glass vias with engineered geometry in additive-free electrolyte

Defect-free metallization of through-glass vias (TGVs) with copper using an additive-free electrolyte is presented in this communication. Engineered vias with an X-shape in the middle were electroplated in the kinetic-limited regime (Thiele modulus, μ ≤ 1) to achieve pinching of the vias at the waist, after which continued conformal plating ensured void-free filling. Thiele modulus analysis and an 1D steady-state model predicted that the deposition front moves uniformly within the via when plating is carried out in the kinetic-limited regime. It was hypothesized that engineering the via geometry to an X-shape could enable pinching in the middle. However, neither of the two conditions are enough on their own to achieve defect-free filling. Combining these two allows conformal movement of the plating front and pinching in the middle, which results in complete filling of the via. While additive-based bath is required and will continue to be used to optimize between plating speed, low stress and roughness of plated copper, the objective of this article is to demonstrate the advantage of engineered vias in which even an additive-free bath could provide defect-free metallization. At very low current densities, an anomalous increase in thickness in the middle compared to the top of the via was observed. This cannot be explained by a simple 1D model and is an interesting next step in understanding additive-free electroplating.

Evolution of grinding energy and particle size during dry ball-milling of silica sand

The energy efficiency of dry fine grinding process of powders dramatically declines with decreasing particle size, and represents a growing concern in various cutting-edge technical applications for pharmaceutical and cosmetic products, advanced-ceramics, and food industry. In this paper, we report on a detailed experimental analysis of the long-term grinding behavior of silica sand as a model material in an oscillatory ball mill for a broad range of the values of vibration frequency and amount of powder. We show that the re-agglomeration of fine particles unambiguously explains the anomalous increase of grinding power consumption. We also find that the agglomeration phenomena are correlated with the volume fraction of the class of finest particles. A nonlinear comminution model is shown to capture this effect for the prediction of the evolution of the specific surface area.

Structural disorder, sublattice melting, and thermo-elastic properties of anti-perovskite Li3OBr under high pressure and temperature

In situ synchrotron x-ray diffraction experiments were conducted in the system Li-O-Br at pressures up to 6.5 GPa and temperatures up to the melting points. The thermal equation of state determined from the P–V–T measurements indicates that crystalline anti-perovskite Li3OBr exhibits similar thermo-elastic properties to common salts. At temperatures that are 50–75 °C below the crystal melting, a pre-melting behavior was inferred based on weakened Bragg intensity and a substantial increase in the diffuse scattering. Concurrent with the onset of pre-melting, an anomalous increase in the lattice volume was observed and is interpreted as anion sublattice disorder. These findings support previous ab initio molecular dynamics simulations based on a simple anion interchange mechanism, indicating that structural disorder below crystal melting temperature can be a main driving force for Li-sublattice melting and superionic transition in the Li3OBr anti-perovskite.

Coating Effect on the 1H-NMR Relaxation Properties of Iron Oxide Magnetic Nanoparticles.

We present a 1H Nuclear Magnetic Resonance (NMR) relaxometry experimental investigation of two series of magnetic nanoparticles, constituted of a maghemite core with a mean diameter dTEM = 17 ± 2.5 nm and 8 ± 0.4 nm, respectively, and coated with four different negative polyelectrolytes. A full structural, morpho-dimensional and magnetic characterization was performed by means of Transmission Electron Microscopy, Atomic Force Microscopy and DC magnetometry. The magnetization curves showed that the investigated nanoparticles displayed a different approach to the saturation depending on the coatings, the less steep ones being those of the two samples coated with P(MAA-stat-MAPEG), suggesting the possibility of slightly different local magnetic disorders induced by the presence of the various polyelectrolytes on the particles’ surface. For each series, 1H NMR relaxivities were found to depend very slightly on the surface coating. We observed a higher transverse nuclear relaxivity, r2, at all investigated frequencies (10 kHz ≤ νL ≤ 60 MHz) for the larger diameter series, and a very different frequency behavior for the longitudinal nuclear relaxivity, r1, between the two series. In particular, the first one (dTEM = 17 nm) displayed an anomalous increase of r1 toward the lowest frequencies, possibly due to high magnetic anisotropy together with spin disorder effects. The other series (dTEM = 8 nm) displayed a r1 vs. νL behavior that can be described by the Roch’s heuristic model. The fitting procedure provided the distance of the minimum approach and the value of the Néel reversal time (τ ≈ 3.5 ÷ 3.9·10−9 s) at room temperature, confirming the superparamagnetic nature of these compounds.

Groundwater radon precursor anomalies identification by decision tree method

Radon in groundwater has long been recognized as a sensitive indicator of crustal stress. Significant changes in groundwater radon concentration before earthquakes have been documented in many studies. However, the radon concentration in groundwater may be affected by many interference factors. The anomalies before seismic activities may not be large enough to be clearly identified by the conventional statistical method. Therefore, new methods are needed to identify the possible pre-seismic anomalies. In this study, we investigated 38 years’ worth of radon time series data (1977–2015) in a hot spring to identify the possible precursor anomalies. We first identify the factors that may affect the radon fluctuations by wavelet coherence analysis, spring discharge, water temperature, rainfall and barometric pressure. All are found to be closely related to the radon fluctuation. The time series (1980–2008) were used for further decision tree analysis as a high correlation in the duration. Following this, we constructed the decision tree models based on these factors to model the “background” radon fluctuation and identify the anomalies by comparing the difference between the observed radon changes and the “background” fluctuations. The modeled “background” fluctuation is closely related to the observed data during the non-seismic activity period, with the correlation coefficient of 0.8. Following this, we compared the modeled “background” fluctuation of the radon time series with the observed one during the seismic activities period. The decision tree could identify 15 possible radon anomalies among the 24 chosen earthquakes. The identified anomalies are also supported by the anomaly changes in water temperature and spring discharge. Therefore, we believe that the decision tree method could be an efficient way to identify the possible precursor anomalies in future studies. Additionally, we explore the mechanism of radon anomalies. The plausible mechanism for the anomalous increase is that radon is continuously supplied from newly formed internal surfaces of the crack to the aquifer system. For the anomalous decrease, it might be related to radon partitioning into the gas phase and the change of mixing ratio of shallow and depth water.

Groundwater oxygen anomaly related to the 2016 Kumamoto earthquake in Southwest Japan.

Here, we report the groundwater oxygen isotope anomalies caused by the 2016 Kumamoto earthquake (MJMA7.3) that occurred in Southwest Japan on April 16, 2016. One hundred and seventeen groundwater samples were collected from a deep well located 3 km to the southeast of the epicenter in Mifune Town, Kumamoto Prefecture; they were drinking water packed in PET bottles and distributed in the area between April 2015 and March 2018. Further, the oxygen and hydrogen isotopes were evaluated via cavity ring-down spectroscopy without performing any pretreatment. An anomalous increase was observed with respect to the δ18O value (up to 0.51‰) soon after the earthquake along with a precursory increase of 0.38‰ in January 2016 before the earthquake. During these periods, there was no noticeable change in the hydrogen isotopic ratios. Rapid crustal deformation related to the earthquake may have enhanced the microfracturing of the aquifer rocks and the production of new surfaces, inducing δ18O enrichment via oxygen isotopic exchange between rock and porewater without changing δ2H.

Structural characterization, dielectric, and magnetic properties of Ti-doped YFeO3 multiferroic compound

Crystal structure, and magnetic and dielectric properties were studied in Ti-doped YFeO3 polycrystalline samples. The crystal structure and chemical state of the Fe/Ti cations were characterized by a combination of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It is found that a narrow solid-solubility limit is achieved (~ 6%) and the d0–ness of Ti4+ is not favored in the YFeO3 matrix. A change in the valence states of Fe and Ti cations explains not only the low solubility limit but also the anomalous increase of the volume cell. Soft magnetic hysteresis curves in the M vs H curves indicate that the weak ferromagnetic contribution prevails for all the studied samples. Furthermore, by means of differential calorimetry (DSC) it was possible to identify the AFM transition which decreases with increasing Ti content. On the other hand, the change of the step-like anomaly to a broad peak in the permittivity (e′) and loss tangent (tan δ) as Ti content increases resemble to a relaxor ferroelectric transition. The endothermic peak (DSC) around the magnetic transition and the broad peaks in the e′(T) data seem to indicate the existence of a local polarization coupled with AFM transition at ~ 650 K. Two types of charge carriers were found in the doped systems, oxygen vacancies at high temperatures, and small polarons at low temperatures, respectively. Besides, it is found that the introduction of those charge carriers in the YFeO3 matrix occurs by the change of oxidation state from Fe3+ to Fe2+ through Ti3+.

Microstructural stability and mechanical behavior of a Co–20Ni–7Al–7W–4Ti at.% superalloy

The temporal evolution of the microstructure and microhardness of a polycrystalline L12-strengthened Co-based superalloy (Co–19.6Ni–7.6Al–7.4W–4.1Ti, at.%) was investigated for an aging temperature of 900 °C. The γ(f.c.c.)/γ′(L12) structure remained stable throughout aging to the longest aging time of 2000 h (83 days), with no additional phases present. While the volume fraction of γ′(L12)-precipitates reached an almost constant value of 64% at 16 h, the temporal evolution of the γ′(L12)-precipitates’ mean-radius and their number density (temporal exponent of p = 3.49 ± 0.18 for the equivalent radius, and q = −0.74 ± 0.04 for the volumetric number density) deviated somewhat from the Lifshitz-Slyozov (LS) predictions (p = 3 and q = −1), suggesting that the alloy had not achieved a true stationary-state at 2000 h. At ambient temperature, a peak Vickers microhardness of 3.80 ± 0.10 GPa was achieved after 240 h of aging. As the testing temperature was increased, an anomalous increase in flow-stress was also observed, with a peak flow-stress value of 705 MPa measured at 750 °C, 30 MPa higher than an archival literature value with about half the Ni concentration (10 at.%). Creep resistance at 850 °C was greater than an archival literature value for a ternary Co–9Al–9W alloy. After 200 h of compressive creep at 850 °C the microstructure evolved as follows: (i) the volume fraction of the γ′(L12)-phase increased from 64% to 79%; and (ii) some grains exhibited rafts of γ′(L12)-precipitates along ⟨100⟩-directions. While the first change is expected to improve creep resistance, the second one is deleterious, as evidenced by a comparison with the creep resistance of a sample without rafts of γ′(L12)-precipitates tested for the same conditions.

Anomalous Increase in Spectral Intensity of Soft-Mode Raman Scattering near the Temperature of the Ferroelectric Phase Transition in Lithium Tantalate Crystals

Reported are the results of studying the sharp increase in the spectral intensity at the lattice soft mode near the temperature of the phase transition in the lithium tantalate crystal. The Raman scattering spectra are recorded in the x(zz)y polarization geometry corresponding to manifestation of the soft mode responsible for the ferroelectric phase transition in lithium tantalate at 898 K. The recording is performed at fixed temperatures T ( $$I(\omega {\kern 1pt} ',T)$$ , T = const) and at fixed spectrometer frequencies ( $$I(\omega {\kern 1pt} ',T)$$ , $$\omega {\kern 1pt} ' = {{\omega }_{0}} - T = {\text{const}}$$ ) under slow (1 deg./min) crystal temperature variation. Strong increase (by three orders of magnitude) is observed in the peak of the reduced spectral intensity i0(Ω) of the isofrequency temperature dependence at the fixed spectrometer frequency shift relative to the exciting radiation $$\Omega = {{\omega }_{0}} - \omega {\kern 1pt} ' = 10$$ cm–1 similar to the one earlier observed in quartz crystals.

Anomalous refraction of optical spacetime wave packets

Refraction at the interface between two materials is fundamental to the interaction of light with photonic devices and to the propagation of light through the atmosphere at large. Underpinning the traditional rules for the refraction of an optical field is the tacit presumption of the separability of its spatial and temporal degrees-of-freedom. We show here that endowing a pulsed beam with precise spatio-temporal spectral correlations unveils remarkable refractory phenomena, such as group-velocity invariance with respect to the refractive index, group-delay cancellation, anomalous group-velocity increase in higher-index materials, and tunable group velocity by varying the angle of incidence. A law of refraction for `space-time' wave packets encompassing these effects is verified experimentally in a variety of optical materials. Space-time refraction defies our expectations derived from Fermat's principle and offers new opportunities for molding the flow of light and other wave phenomena.

Measurement of ambient gamma dose rate in Metro Manila, Philippines, using a portable NaI(TI) scintillation survey meter.

Radiological data such as ambient dose equivalent rate obtained from radiation monitoring in Metro Manila are useful for the detection of any anomalous increase of radiation dose rate levels due to nuclear or radiological emergencies. In this study, ambient dose equivalent rates were measured in different locations in Metro Manila using a portable NaI(Tl) scintillation survey meter to determine the background radiation levels within the capital. Ambient dose equivalent rates measured range from 32.7 ± 2.2 to 59.3 ± 8.7 nanosieverts per hour (nSv/h) with computed mean and median values of 41.7 and 39.6nSv/h, respectively. These values were lower than the Philippines' average dose rate which is 52 nanograys per hour (nGy/h). No significant trend was also observed in the monthly variation of ambient dose equivalent rate for most locations, with the dose rates being relatively consistent throughout a year. No significant trend was further observed in the monthly variation of ambient dose equivalent rate for the whole Metro Manila. Data obtained in this study were used to develop a dose rate distribution map of Metro Manila which could be used as a baseline reference of emergency responders for environmental radioactivity monitoring during nuclear or radiological emergencies that may affect Metro Manila.

El Niño as a predictor of round sardinella distribution along the northwest African coast

The El Niño Southern Oscillation (ENSO) produces global marine environment conditions that can cause changes in abundance and distribution of distant fish populations worldwide. Understanding mechanisms acting locally on fish population dynamics is crucial to develop forecast skill useful for fisheries management. The present work addresses the role played by ENSO on the round sardinella population biomass and distribution in the central-southern portion of the Canary Current Upwelling System (CCUS). A combined physical-biogeochemical framework is used to understand the climate influence on the hydrodynamical conditions in the study area. Then, an evolutionary individual-based model is used to simulate the round sardinella spatio-temporal biomass variability. According to model experiments, anomalous oceanographic conditions forced by El Niño along the African coast cause anomalies in the latitudinal migration pattern of the species. A robust anomalous increase and decrease of the simulated round sardinella biomass is identified in winter off the Cape Blanc and the Saharan coast region, respectively, in response to El Niño variations. The resultant anomalous pattern is an alteration of the normal migration between the Saharan and the Mauritanian waters. It is primarily explained by the modulating role that El Niño exerts on the currents off Cape Blanc, modifying therefore the normal migration of round sardinella in the search of acceptable temperature conditions. This climate signature can be potentially predicted up to six months in advance based on El Niño conditions in the Pacific.