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By analyzing 22 years (1993By analyzing 22 years ( -2015 of daily eddy data, statistics of surface eddy properties were refreshed in the South China Sea. More than 7,000 of historical Argo profiles were collocated into eddy-centered coordinates to reveal the composite mean three-dimensional structure of eddies. The results indicate that eddies of both polarities have long conical shape, with a maximum (minimum) density anomaly of 0.55 kg/m 3 (À0.51 kg/m 3 ) at 60 m (90 m) in the composite cyclonic (anticyclonic) eddy. Temperature and salinity anomalies also peak at eddy cores, with values of À1.5°C and 0.15 psu in the cyclonic eddy and 1.4°C and À0.16 psu in the anticyclonic eddy. The temperature and density anomalies extend vertically to 400-500 m, while the salinity anomalies are apparent only in the upper 150 m. The temperature anomalies contribute about 90% of the density anomalies. Mixed layer depths in cyclonic eddies are on average 15 m shallower than those in anticyclonic eddies. The rotation of the composite cyclonic (anticyclonic) eddy generates meridional heat transport of 1.4 × 10 12 W (À3.1 × 10 12 W) and salt transport of À4.0 × 10 4 kg/s (5.6 × 10 4 kg/s). More than 90% of the heat and salt transports are concentrated in the upper 300 and 100 m, respectively. Compared to the meridional transports, the westward propagation of eddies results in zonal heat and salt transports on the same orders of magnitudes. The westward propagation of eddies also generates a basin-scale westward water transport of 1.4 Sv, equivalent to about 30% of the annual-mean Luzon Strait transport. HE ET AL.4906

Silurian marine shale in Sichuan Basin is the most significant target zone for shale gas resources in China. In this work, a combined experimental and molecular simulation study was conducted to characterize the thermodynamic and structural properties of the organic matter in Silurian shale. Organic geochemistry experiments and Fourier transform infrared (FTIR) spectroscopy were performed to provide structural parameters for the main skeleton of the organic matter. A realistic molecular model of the organic matter under typical reservoir conditions was generated by molecular dynamics simulations based on the experimental results and documented analytic data. The thermodynamic and structural properties of the organic matter model were discussed in detail. Clear correlations are found among geochemistry properties and structural parameters of organic matter, independent of organic matter type and maturity. Aromatic units in the organic matter are highly condensed, and the interunit linkages are mainly short methylene groups. Ether groups are the dominant oxygenated compounds, while aromatic sulfur is the main form of organic sulfur. Reasonable consistencies are found on results of compositions of the organic matter fractions and physical density between simulated and available experimental data. The isothermal compressibility and thermal expansion coefficient correspond to the general range of a liquid. In addition to micropores, the organic matter contains a large amount of ultramicropores, which contribute a lot to the high porosity and specific surface area. The porous network is highly connected with few dead pores. Interestingly, the introduction of bitumen fractions has little effect on the spacing of polyaromatic units, but it aggravates the relative slippage of polyaromatic units. Also, separation of lighter compounds is observed in the structure. The carbon dioxide molecules are closer to the oxygenated groups, while the nitrogen molecules and methane molecules are closer to the sulfur functional groups and nitrogen functional groups. This proposed organic matter model can serve as a starting point for further theoretical investigations on gas adsorption and transport mechanisms, representative of the organic matter in Silurian shale at molecular scale.

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