Late monsoon threatens coral refugia in the Andaman Sea

Internal waves (IWs) mitigate thermal stress and provide refugia for corals against increasingly frequent mass bleaching. However, climate events may bring uncertainty regarding the resistance of such refugia. Here, using in situ observation data in the Andaman Sea (AS), we conduct a case study in which a monsoon anomaly associated with El Niño event threatens IW coral refugia. IW cooling in the AS coral reefs is modulated by the thermocline depth variation, which is significantly driven by Kelvin wave signals from the equator. In premonsoon period, distinct variations in IW cooling and surface heating form a time window of quickly-growing cumulative heat exposure. The El Niño induces a typical 2-week delayed summer monsoon, which prolongs the duration of thermal stress growth and brings severe bleaching risk to corals. As global warming increases the frequency of extreme El Niño events, IW coral refugia will face great challenges in the future.

In Situ Observation of Liquid Solder Alloys and Solid Substrate Reactions Using High-Voltage Transmission Electron Microscopy

The complex reaction between liquid solder alloys and solid substrates has been studied ex-situ in a few studies, utilizing creative setups to “freeze” the reactions at different stages during the reflow soldering process. However, full understanding of the dynamics of the process is difficult due to the lack of direct observation at micro- and nano-meter resolutions. In this study, high voltage transmission electron microscopy (HV-TEM) is employed to observe the morphological changes that occur in Cu6Sn5 between a Sn-3.0 wt%Ag-0.5 wt%Cu (SAC305) solder alloy and a Cu substrate in situ at temperatures above the solidus of the alloy. This enables the continuous surveillance of rapid grain boundary movements of Cu6Sn5 during soldering and increases the fundamental understanding of reaction mechanisms in solder solid/liquid interfaces.

Heterogeneous Effects on Chemo-Mechanical Coupling Behaviors at the Single-Particle Level

Understanding and alleviating the chemo-mechanical degradation of silicon anodes is a formidable challenge due to the large volume change during operations. Here, for a comprehensive understanding of heterogeneous effects on chemo-mechanical behaviors at the single-particle level, in-situ observation of single-crystalline silicon micropillar electrodes under the inhomogeneous extrinsic conditions, taken as an example, was made. The observation shows that the anisotropic deformation patterns and fracture starting sites are reshaped with the combination of the inhomogeneous electrochemical driving force for charge transfer at the interface between the silicon micropillar and the electrolyte, and crystal orientation-dependent lithiation dynamics. Also, the numerical simulation unravels the underlying mechanisms of deformation and fracture behaviors, and well predicts the relative depth of lithiation at the time of crack initiation under heterogeneous conditions. The results show that heterogeneities arising from extrinsic conditions may induce inhomogeneous mechanical damage and tailor lithiation degree at an active particle level, offering insights into designing large-volume-change battery particles with good mechanical integrity and electrochemical performance under heterogeneous impacts.

Thermocline Model for Estimating Argo Sea Surface Temperature

Argo has become an important constituent of the global ocean observation system. However, due to the lack of sea surface measurements from most Argo profiles, the application of Argo data is still limited. In this study, a thermocline model was constructed based on three key thermocline parameters, i.e, thermocline upper depth, the thermocline bottom depth, and thermocline temperature gradient. Following the model, we estimated the sea surface temperature of Argo profiles by providing the relationship between sea surface and subsurface temperature. We tested the effectiveness of our proposed model using statistical analysis and by comparing the sea surface temperature with the results obtained from traditional methods and in situ observations in the Pacific Ocean. The root mean square errors of results obtained from thermocline model were found to be significantly reduced compared to the extrapolation results and satellite retrieved temperature results. The correlation coefficient between the estimation result and in situ observation was 0.967. Argo surface temperature, estimated by the thermocline model, has been theoretically proved to be reliable. Thus, our model generates theoretically feasible data present the mesoscale phenomenon in more detail. Overall, this study compensates for the lack surface observation of Argo, and provides a new tool to establish complete Argo data sets.