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Western boundary currents (WBCs) of the Southern Hemisphere transport heat poleward and are regions of rapid ocean warming. However, the mechanisms responsible for the enhanced warming over the Southern Hemisphere WBC extensions are still debated. Here we show that enhanced eddy generation in the WBC extensions through changes in barotropic and baroclinic instabilities results in enhanced ocean warming as the eddies propagate. This results from a poleward shift of the WBCs, associated with changes in the mid-latitude easterly winds. Consequently, the WBCs have penetrated poleward but not strengthened and are now transporting more heat into their extensions. Our study clearly elucidates the dynamic processes driving increased eddying and warming in the Southern Hemisphere WBC extensions and has implications for understanding and predicting ocean warming, marine heatwaves and the impact on the marine ecosystem in the WBC extensions under climate change.Observed warming of the Southern Hemisphere western boundary currents (WBCs) is still under debate. Here poleward shifts, associated with changes in the mid-latitude easterly winds, of the WBCs, not strengthening, are found to drive enhanced eddy generation and ocean warming in their extensions.

Whether the state-of-the-art CMIP5 models have different El Niño types and how the degree of modeled El Niño diversity would be impacted by the future global warming are still heavily debated. In this study, cluster analysis is used to investigate El Niño diversity in 30 CMIP5 models. As the method does not rely on any prior knowledge of the patterns of El Niño seen in observations, it provides a practical way to identify the degree of El Niño diversity in models. Under the historical scenario, most models show a poor degree of El Niño diversity in their own model world, primarily due to the lopsided numbers of events belonging to the two modeled El Niño types and the weak compactness of events in each cluster. Four models are found showing significant El Niño diversity, yet none of them captures the longitudinal distributions of the warming centers of the two El Niño types seen in the observations. Heat budget analysis of the sea surface temperature (SST) anomaly suggests that the degree of modeled El Niño diversity is highly related to the climatological zonal SST gradient over the western-central equatorial Pacific in models. As the gradient is weakened in most models under the future high-emission scenario, the degree of modeled El Niño diversity is further reduced in the future. The results indicate that a better simulation of the SST gradient over the western-central equatorial Pacific might allow a more reliable simulation/projection of El Niño diversity in most CMIP5 models.

Arctic sea ice plays a critical role in modulating our global climate system and the exchange of heat fluxes in the polar region, but its impact on climate varies across different sea ice thickness (SIT) categories. Compared to sea ice cover, the performance of ice models in simulating SIT has been less evaluated, particularly in the sixth Coupled Model Intercomparison Project Phase (CMIP6). Here, we chose 12 CMIP6 models with the Community Ice Code model (CICE) components and compared their SIT simulations with the satellite observations and the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) model between 1980 and 2014. Our results show that the seasonal cycle of the PIOMAS SIT is consistent with satellite observations. Compared to the PIOMAS reanalysis, the multi-model ensemble mean (MME) well represents the sea ice extent in both the thin ice (<0.6 m) and thick ice (> 3.6 m). However, the MME SIT has larger biases in the Chukchi Sea, the Beaufort Sea, the central Arctic, and the Greenland Sea during winter and mainly in the central Arctic during summer. Both the MME and PIOMAS show decreasing trends in SIT over the entire Arctic Ocean in all seasons, but the interannual variability of SIT in MME is smaller than that in PIOMAS. Among the 12 CMIP6 models, the FIO-ESM-2.0 model shows the best simulation of the annual mean SIT, but the SAM0-UNICON and NESM3 models have the largest biases in the climatological mean SIT over the Arctic Ocean. We also demonstrate that the FIO-ESM-2.0 performs the best in the seasonal cycles of SIT. Our study suggests that more attention should be paid to the coupling of the CICE model with ocean and atmosphere models, which is vital to improving the SIT simulation in CMIP6 models and to better understanding the impact of Arctic sea ice on our climate system.

ESG (environment, society and Governance) has leapt from marginal issues to core strategic elements of business. Traditional enterprises used to regard ESG as a compliance burden, but with the capital market, consumers and investors turning to the responsibility profit orientation, ESG is transforming from a “compliance pass line” to a key engine driving enterprise transformation, reshaping competitiveness and creating economic benefits. Resource intensive and high emission enterprises are facing the dual pressure of growth slowdown and sustainable challenges, and it will miss major opportunities to regard ESG as a “cost center”. This review focuses on how ESG practices transcend compliance and open up profit growth space for traditional enterprises. The core is to build and analyze the value creation path with digital transformation (DT) and green transformation (GT) as key levers and in-depth synergy of the two. In addition, although this paper focuses on traditional enterprises under heavy pressure (especially high emissions), the analysis framework and some conclusions are universal.

Marine heatwaves are known to cause severe ecosystem damage and therefore have received attention in recent years. However, the focus has tended to be on global (surface) studies, but not coastal waters. Cyclonic eddies are important and underappreciated components in the eddy-dominated western boundary current system, but their impacts on the path of the western boundary currents have largely been unexplored. Here we show that cold cyclonic eddies can modulate the most intense coastal marine heatwaves on record inshore of the East Australian Current. We show that the marine heatwave was driven and modulated by the lateral movement of the western boundary current jet and cyclonic eddies. This study reveals that the interplay of cyclonic eddies and a western boundary current can drive coastal ocean warming, paving the way for future investigations into eddy interactions and the evolution of coastal marine heatwaves in other western boundary current regions.

The study of Equatorial Undercurrent (EUC) has attracted a broad attention in recent years due to its strong response and feedback to the Indian Ocean Dipole. In this paper, we first produce a high-quality simulation of three-dimensional temperature, salinity and zonal current simulation from 1982 to 2014, using a high-resolution ocean general circulation model. On this basis, with two sensitivity experiments, we investigate the role of temperature and salinity anomalies in driving and enhancing the EUC during the positive IOD events by examining the variation of the EUC seasonal cycle and diagnosing the zonal momentum budget along the equatorial Indian Ocean. Our results show that during January–March, the EUC can appear along the entire equatorial Indian Ocean in all years, but during August–November, the EUC can appear and reach the eastern Indian Ocean only during the positive IOD events. The zonal momentum budget analysis indicates that the pressure gradient force contributes most to the variation of the eastward acceleration of zonal currents in the subsurface. During the positive IOD events, strong negative subsurface temperature anomalies exist in the eastern Indian Ocean, with negative surface salinity anomalies in the central and eastern Indian Ocean, resulting in a large pressure gradient force to drive EUC during the August–November. Further, the results of two sensitivity experiments indicate that the temperature anomalies significantly impact the pressure gradient force, playing a leading role in driving the EUC, while the surface salinity anomalies can secondarily help to intensify the eastward EUC through increasing the zonal density gradient in the eastern Indian Ocean and impacting the vertical momentum advection in the subsurface.

Estuarine outflow can have a significant impact on physical and ecological systems in the coastal ocean. Along southeastern Australia, inshore of the East Australian Current, the shelf is narrow, the coastal circulation is advection dominated, and river estuarine outflow tends to be low, hence river plumes have largely been ignored. For these reasons, we lack an understanding of the spatial and temporal evolution of river plumes during large rainfall events (which are projected to increase in frequency and intensity), and the interaction of the mesoscale circulation with the estuarine outflow remains to be explored. Using a high-resolution (750 m) hydrodynamic model, we simulate idealized plumes from 4 estuaries during three different mesoscale circulation scenarios and investigate the spatial and temporal evolution of the estuarine outflow under two contrasting rainfall events (normal and large). We explore the plume from the largest of the 4 rivers, the Hawkesbury River, to understand the impact of the mesoscale circulation. During the first EAC mode, the plume spreads both northward and southeastward. The offshore spread of the plume is the largest in this scenario (~12.5 km east of the river mouth) in the wet event. In the second EAC mode, this plume dispersal is toward the north and east, driven by the proximity of a cyclonic eddy on the shelf, with an eastward extension of 11 km. In the third EAC mode, most of this river plume spreads southward with some to the north, again dictated by the position of the cyclonic eddy. The cross-shelf dispersal is a minimum of 9.5 km from the river mouth. It takes around 6 days for the freshwater spatial extent of the plume in the wet event to return to the base case. These results show the importance of mesoscale EAC circulation on the shelf circulation when considering river plumes dispersal. Knowledge of the ultimate fate of riverborne material, dilution and cumulative effects will enable better environmental management of this dynamic region for the local government.

Amaryllidaceae alkaloids (AAs) are complex plant secondary metabolites possessing a wide range of biological activities. 4′-O-methylnorbelladine (4OMN) is the branchpoint intermediate for the entire AAs, and was the last common intermediate before AA pathway branches diverge. The cyclization of 4OMN by C-C oxidative coupling, which can afford para-para ′, ortho-para ′, and para-ortho ′ scaffold, was catalyzed by cytochrome P450 96T (CYP96T) family enzymes. To clarify the mechanisms involved in this controversial step, four CYP96T homologs (LauCYP96T1, LauCYP96T1-like-1, LauCYP96T1-like-2 and LauCYP96T1-like-3) were cloned from the full-length transcriptome of Lycoris aurea . All the four LauCYP96T are localized to endoplasmic reticulum. Functional analysis reveals that LauCYP96T1 and LauCYP96T1-like proteins display inverted regioselectivity for oxidative coupling of 4OMN, in which LauCYP96T1 and LauCYP96T1-like-2 dominantly afford para-para ′ scaffold, and LauCYP96T1-like-1 and LauCYP96T1-like-3 are responsible for para-ortho ′ scaffold formation. Using molecular homology modeling and docking studies, we predicted models for the binding of 4OMN to LauCYP96T, and identified two amino acid residues that might be responsible for the dominant changes in generated products of para-ortho ′ and para-para ′ oxidative coupling. Our results highlight the functional diversity and promiscuity of LauCYP96T enzymes and might provide valuable information for Amaryllidaceae alkaloid production.

With the increased interest in studying the sea surface salinity anomaly (SSSA) of the tropical Indian Ocean during the Indian Ocean Dipole (IOD), an index describing the dipole variability of the SSSA has been pursued recently. In this study, we first use a regional ocean model with a high spatial resolution to produce a high-quality salinity simulation during the period from 1982 to 2014, from which the SSSA dipole structure is identified for boreal autumn. On this basis, by further analysing the observed data, we define a dipole index of the SSSA between the central equatorial Indian Ocean (CEIO: 70°E-90°E, 5°S-5°N) and the region off the Sumatra-Java coast (SJC: 100°E-110°E, 13°S-3°S). Compared with previous SSSA dipole indices, this index has advantages in detecting the dipole signals and in characterizing their relationship to the sea surface temperature anomaly (SSTA) dipole variability. Finally, the mechanism of the SSSA dipole is investigated by dynamical diagnosis. It is found that anomalous zonal advection dominates the SSSA in the CEIO region, whereas the SSSA in the SJC region are mainly influenced by the anomalous surface freshwater flux. This SSSA dipole provides a positive feedback to the formation of the IOD events.

So far, the identification and determination of flavor additives in food has gained extensive attention in the area of food safety. However, it remains a big challenge for simultaneous detection of diverse flavor agents. In this work, a novel gas chromatography method coupled with ultrasound-microwave synergistic extraction was developed for simultaneous detection of five flavor compounds, including butyl butyrate, menthol, methyl salicylate, eugenol and vanilline. In this strategy, ultrasound-microwave synergistic extraction was used to extract the five flavoring agents from chewing gum. The effects of extractants, solid-liquid ratio, extraction time and microwave power on extraction yield were researched by using orthogonal test. After the optimization of programme temperature and splitless injection, the five flavoring agents were well separated and simultaneously detected with wide linear ranges, low limits of detection, high accuracy and good repeatability. Therefore, this proposed method would hold great promise for assay application on the food safety.