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Abstract Understanding internal variability of the climate system is critical when isolating internal and anthropogenically forced signals. Here, we investigate the modes of Atlantic Meridional Overturning Circulation (AMOC) variability using perturbation experiments with the Institut Pierre‐Simon Laplace's (IPSL) coupled model and compare them to Coupled Model Intercomparison Project Phase 6 (CMIP6) pre‐industrial control simulations. We identify two characteristic modes of variability—decadal‐to‐multidecadal (DMD_var) and centennial (CEN_var). The former is driven largely by temperature anomalies in the subpolar North Atlantic, while the latter is driven by salinity in the western subpolar North Atlantic. The amplitude of each mode scales linearly with the meanAMOCstrength in the IPSL experiments. TheDMD_varamplitude correlates well with theAMOCmean strength across CMIP6 models, while theCEN_varmode does not. These findings suggest that the strength ofDMD_vardepends robustly on the North Atlantic mean state, while theCEN_varmode may be model‐dependent. 

Abstract Vanadium Dioxide (VO₂) is a material that exhibits a phase transition from an insulating state to a metallic state at ≈68 °C. During a temperature cycle consisting of warming followed by cooling, the resistivity of VO₂changes by several orders of magnitude over the course of the hysteresis loop. Using a focused laser beam (λ = 532 nm), it is shown that it is possible to optically generate micron‐sized metallic patterns within the insulating phase of a VO₂planar junction which can be used to tune, on demand, the resistance of the VO₂junction. A resistor network simulation is used to characterize the resulting resistance drops in the devices. These patterns persist while the base temperature is held constant within the hysteretic region while being easily removed totally by simply lowering the base temperature. Surprisingly, it is also observed that the pattern can be partially erased using an atomic force microscope (AFM) tip on the submicron scale. This erasing process can be qualitatively explained by the temperature difference between the VO₂surface and the tip which acts as a local cooler. This optical and AFM resistive fine‐tuning offers the possibility of creating controllable synaptic weights between room‐temperature VO₂neuristors. 

Abstract The models that participated in the Coupled Model Intercomparison Project (CMIP) exhibit large biases in Arctic sea ice climatology that seem related to biases in seasonal atmospheric and oceanic circulations. Using historical runs of 34 CMIP6 models from 1979 to 2014, we investigate the links between the climatological sea ice concentration (SIC) biases in September and atmospheric and oceanic model climatologies. The main intermodel spread of September SIC is well described by two leading EOFs, which together explain ∼65% of its variance. The first EOF represents an underestimation or overestimation of SIC in the whole Arctic, while the second EOF describes opposite SIC biases in the Atlantic and Pacific sectors. Regression analysis indicates that the two SIC modes are closely related to departures from the multimodel mean of Arctic surface heat fluxes during summer, primarily shortwave and longwave radiation, with incoming Atlantic Water playing a role in the Atlantic sector. Local and global links with summer cloud cover, low-level humidity, upper or lower troposphere temperature/circulation, and oceanic variables are also found. As illustrated for three climate models, the local relationships with the SIC biases are mostly similar in the Arctic across the models but show varying degrees of Atlantic inflow influence. On a global scale, a strong influence of the summer atmospheric circulation on September SIC is suggested for one of the three models, while the atmospheric influence is primarily via thermodynamics in the other two. Clear links to the North Atlantic oceanic circulation are seen in one of the models. 

Abstract Convective gravity waves are important for the forcing of the quasi biennial oscillation (QBO). There is a wave component that is stationary with respect to the convective cells that is triggered by convection acting like a barrier to the background flow (moving mountain mechanism). Waves from this mechanism have only been observed in a few case studies and are not parameterized in climate models. However, the representation of the whole spectrum of gravity waves is crucial for the simulation of the QBO, especially in the lowermost stratosphere (below 50 hPa) where the QBO amplitudes are under‐estimated in current global circulation models. In this study, we present analysis of convective gravity wave observations from superpressure balloons in boreal winter 2019 and 2021, retrieving phase speeds, momentum fluxes, and drag. We also identify waves generated by the moving mountain mechanism using the theory of the Beres scheme as a basis. These waves do not have a specific period, but are of smaller horizontal scale, on average around 300 km, which is similar to the scale of convective systems. Our results show that gravity waves contribute up to 2/3 to the QBO forcing below 50 hPa and waves from the moving mountain mechanism are responsible for up to 10% of this forcing. 

Abstract In a recent work, Baladi and Demers constructed a measure of maximal entropy for finite horizon dispersing billiard maps and proved that it is unique, mixing and moreover Bernoulli. We show that this measure enjoys natural probabilistic properties for Hölder continuous observables, such as at least polynomial decay of correlations and the Central Limit Theorem. The results of Baladi and Demers are subject to a condition of sparse recurrence to singularities. We use a similar and slightly stronger condition, and it has a direct effect on our rate of decay of correlations. For billiard tables with bounded complexity (a property conjectured to be generic), we show that the sparse recurrence condition is always satisfied and the correlations decay at a super‐polynomial rate. 

ABSTRACT This study focuses on investigating the conformational structure and zinc(II) affinity of a zinc finger‐like motif (ZFM) peptide with the sequence acetyl‐His₁‐Cys₂‐Gly₃‐Pro₄‐Gly₅‐His₆‐Cys₇, where bold highlights the potential zinc(II) binding sites. Zinc fingers are crucial protein motifs known for their high specificity and affinity for zinc ions. The ZFM peptide's sequence contains the 2His‐2Cys zinc‐binding sites similar to those in natural zinc finger proteins but without the hydrophobic core, making it a valuable model for studying zinc(II)–peptide interactions. Previous research on related peptides showed that collision cross sections and B3LYP modeling predicted that the His‐2Cys‐carboxyl terminus coordination of zinc(II) was more stable than the 2His‐2Cys. Employing a comprehensive approach integrating ion mobility–mass spectrometry and theoretical modeling techniques, various zinc(II) binding modes of the ZFM have been thoroughly compared to ascertain their influence on the competitive threshold collision‐induced dissociation method for measuring the relative gas‐phase Zn(II) affinity of the ZFM peptide. The measured Zn(II) affinity of ZFM is greater than those measured recently for two peptides with similar primary structures, acetyl‐His₁‐Cys₂‐Gly₃‐Pro₄‐Gly₅‐Gly₆‐Cys₇and acetyl‐Asp₁‐His₂‐Gly₃‐Pro₄‐Gly₅‐Gly₆‐Cys₇, indicating the preference for the His₁‐Cys₂‐His₆‐Cys₇side groups for coordinating zinc(II) over the His‐2Cys‐carboxyl terminus or Asp‐His‐Cys‐carboxyl terminus in these related heptapeptides. 

Abstract Mesozooplankton is a very diverse group of small animals ranging in size from 0.2 to 20 mm not able to swim against ocean currents. It is a key component of pelagic ecosystems through its roles in the trophic networks and the biological carbon pump. Traditionally studied through microscopes, recent methods have been however developed to rapidly acquire large amounts of data (morphological, molecular) at the individual scale, making it possible to study mesozooplankton using a trait‐based approach. Here, combining quantitative imaging with metabarcoding time‐series data obtained in the Sargasso Sea at the Bermuda Atlantic Time‐series Study (BATS) site, we showed that organisms' transparency might be an important trait to also consider regarding mesozooplankton impact on carbon export, contrary to the common assumption that just size is the master trait directing most mesozooplankton‐linked processes. Three distinct communities were defined based on taxonomic composition, and succeeded one another throughout the study period, with changing levels of transparency among the community. A co‐occurrences' network was built from metabarcoding data revealing six groups of taxa. These were related to changes in the functioning of the ecosystem and/or in the community's morphology. The importance of Diel Vertical Migration at BATS was confirmed by the existence of a group made of taxa known to be strong migrators. Finally, we assessed if metabarcoding can provide a quantitative approach to biomass and/or abundance of certain taxa. Knowing more about mesozooplankton diversity and its impact on ecosystem functioning would allow to better represent them in biogeochemical models. 

Abstract We investigate the impact of Arctic sea ice loss on the Atlantic meridional overturning circulation (AMOC) and North Atlantic climate in a coupled general circulation model (IPSL‐CM5A2) perturbation experiment, wherein Arctic sea ice is reduced until reaching an equilibrium of an ice‐free summer. After several decades we observe AMOC weakening caused by reduced dense water formation in the Iceland basin due to the warming of surface waters, and later compensated by intensification of dense water formation in the Western Subpolar North Atlantic. Consequently, AMOC slightly weakens in deep, dense waters but recovers through shallower, less dense waters overturning. In parallel, wind‐driven intensification and southeastward expansion of the subpolar gyre cause a depth‐extended cold anomaly ∼2°C around 50°N that resembles the North Atlantic “warming hole.” We conclude that compensating dense water formations drive AMOC changes following sea ice retreat and that a warming hole can develop independently of the AMOC modulation. 

Abstract Submesoscale turbulence in the upper ocean consists of fronts, filaments, and vortices that have horizontal scales on the order of 100 m to 10 km. High-resolution numerical simulations have suggested that submesoscale turbulence is associated with strong vertical motion that could substantially enhance the vertical exchange between the thermocline and mixed layer, which may have an impact on marine ecosystems and climate. Theoretical, numerical, and observational work indicates that submesoscale turbulence is energized primarily by baroclinic instability in the mixed layer, which is most vigorous in winter. This study demonstrates how such mixed layer baroclinic instabilities induce vertical exchange by drawing filaments of thermocline water into the mixed layer. A scaling law is proposed for the dependence of the exchange on environmental parameters. Linear stability analysis and nonlinear simulations indicate that the exchange, quantified by how much thermocline water is entrained into the mixed layer, is proportional to the mixed layer depth, is inversely proportional to the Richardson number of the thermocline, and increases with increasing Richardson number of the mixed layer. The results imply that the tracer exchange between the thermocline and mixed layer is more efficient when the mixed layer is thicker, when the mixed layer stratification is stronger, when the lateral buoyancy gradient is stronger, and when the thermocline stratification is weaker. The scaling suggests vigorous exchange between the permanent thermocline and deep mixed layers in winter, especially in mode water formation regions. Significance StatementThis study examines how instabilities in the surface layer of the ocean bring interior water up from below. This interior–surface exchange can be important for dissolved gases such as carbon dioxide and oxygen as well as nutrients fueling biological growth in the surface ocean. A scaling law is proposed for the dependence of the exchange on environmental parameters. The results of this study imply that the exchange is particularly strong if the well-mixed surface layer is thick, lateral density gradients are strong (such as at fronts), and the stratification below the surface layer is weak. These theoretical findings can be implemented in boundary layer parameterization schemes in global ocean models and improve our understanding of the marine ecosystem and how the ocean mediates climate change. 

Abstract Male lizards often display multiple pigment‐based and structural colour signals which may reflect various quality traits (e.g. performance, parasitism), with testosterone (T) often mediating these relationships. Furthermore, environmental conditions can explain colour signal variation by affecting processes such as signal efficacy, thermoregulation and camouflage. The relationships between colour signals, male quality traits and environmental factors have often been analysed in isolation, but simultaneous analyses are rare. Thus, the response of multiple colour signals to variation in all these factors in an integrative analysis remains to be investigated.Here, we investigated how multiple colour signals relate to their information content, examined the role of T as a potential mediator of these relationships and how environmental factors explain colour signal variation.We performed an integrative study to examine the covariation between three colour signals (melanin‐based black, carotenoid‐based yellow–orange and structural UV), physiological performance, parasitism, T levels and environmental factors (microclimate, forest cover) in male common lizardsZootoca viviparafrom 13 populations.We found that the three colour signals conveyed information on different aspects of male condition, supporting a multiple message hypothesis. T influenced only parasitism, suggesting that T does not directly mediate the relationships between colour signals and their information content. Moreover, colour signals became more saturated in forested habitats, suggesting an adaptation to degraded light conditions, and became generally brighter in mesic conditions, in contradiction with the thermal melanism hypothesis.We show that distinct individual quality traits and environmental factors simultaneously explain variations of multiple colour signals with different production modes. Our study therefore highlights the complexity of colour signal evolution, involving various sets of selective pressures acting at the same time, but in different ways depending on colour production mechanism.