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

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Global climate change and human activities have important effects on the water discharge and sediment load of the Pearl River. In this study, the water discharge and sediment load were investigated by using hydro-meteorological data from 1954 to 2018. The linear regression, Mann–Kendall abrupt test and double mass curve were employed to detect trends and abrupt change-points in water discharge and sediment load and to quantify the effects of climate change and human activities on water discharge and sediment load. The results revealed that the annual sediment load exhibited a significant decreasing trend at a rate of − 2.24 × 104 t/year, regardless of water discharge, and an abrupt change occurred in 1998. Human activities, especially dam construction contributed 96% to this change, while 4% was due to climate change. El Niño/Southern Oscillation (ENSO) events are often associated with low precipitation, resulting in low water discharge and sediment load, indicating that changes in ENSO periodicity could affect the inter-annual periodic variations of water discharge and sediment load. As population and economy boom, more dams are being built in the Pearl River basin, and special attention should be paid to the management and mitigation of the effects of dams on sediment load.