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Original velocity measurements at 15 m depth from Surface Velocity Program drifters are used to calculate the circulation in the South China Sea during the Winter Monsoon. The Ekman currents are computed with a new method and subtracted from drifter's velocity to calculate the residual circulation, which is approximately in geostrophic balance. The Ekman flow is nearly zonal and comparable to the zonal geostrophic flow in the northern basin. The geostrophic flow is cyclonic and extends into the southern Luzon Strait. Strong jets occur south of Hainan, off Vietnam and, to the south, off peninsular Malaysia. The Vietnam jet is concentrated inshore of the 200 m isobath, with mean speeds in excess of 1 m s−1. The onshore Ekman transport and pumping velocity computed from the wind stress curl offer a qualitative explanation of the existence and behavior of such jets.

As part of the Dokdo East Sea Time Series Studies (DETS) in the East/Japan Sea, a DETS buoy system was moored on the 130 m deep continental shelf off the Dok Islets in the central part of the East Sea. Chlorophyll a concentrations in the surface water observed by the DETS buoy system exhibited low-frequency bimodal variations in the annual chlorophyll a concentration due to a spring phytoplankton bloom and a smaller fall bloom. In addition, between late spring and early fall when the water column is stratified, frequent low-concentration maxima occurred, which appear to have been triggered by the injection of nutrient-rich subsurface water to the sunlit surface water. The primary productivity in the nutrient-depleted surface ocean was found to be enhanced by subsurface water upwelling where the wind and water move in the same direction as the mesoscale eddy. New observations in the East/Japan Sea based on time-series measurements of chlorophyll a, wind, and other oceanographic variables at fixed sites in the center of the sea and using satellite measurements reveal that the vertical movement of water caused by wind-eddy interactions depends on the relative angle between the wind and the water current. The wind-eddy interaction appears to contribute to the unusually high primary productivity in the region where it was often sustained by the long-lived warm and cold eddies

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