Variability of water mass and throughflow transport in the Taiwan Strait are analyzed using strait‐wide conductivity‐temperature‐depth (1985–2003) and sectional acoustic Doppler current profiler (1999–2001) data. Results from a cluster analysis, temperature‐salinity diagrams, and direct transport calculations indicate that the strong northeast monsoon drives the brackish Mixed China Coastal Water into the northern strait and hinders the northward intruded saline Kuroshio Branch Water (KBW) in the southeastern strait from December to January. The mean throughflow transport across the central strait is about 0.1 Sv southward during this period, thus supporting previous observations that there is no persistent northward flowing current throughout the strait in winter. The weakening of the northeast monsoon in February–March, however, emancipates the KBW to intrude northward into the East China Sea (ECS). In June, the increase in this northward transport accompanied by the decrease in the westward intrusion of Kuroshio through the Luzon Strait leads to the replacement of the KBW by the less saline South China Sea Water (SCSW). The northward transports ranging from 1.16 to 2.34 Sv between March and August yield 0.131–0.238 × 1015 W and 53.33–81.74 × 106 kg/s of temperature and salt transports, respectively, toward the ECS. The inception of the northeast monsoon in October marks both the change of water mass from fall to winter patterns and the decrease of the northward throughflow transport. Our results also reveal that the subsurface KBW and SCSW remain consistent throughout the observation periods between 100 and 200 m and below 200 m depths, respectively, in the southeastern strait.

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[1] Comprehensive carbon chemistry data including total alkalinity (TA), dissolved inorganic carbon (DIC), pH, fugacity of CO 2 , and other pertinent data (i.e., temperature, salinity, and levels of nitrate and chlorophyll a) were measured in surface waters of the East China Sea (ECS) shelf in July 2007. The results show that spatial variations in these parameters closely correspond to the distributions of various water types. The Changjiang Diluted Water (CDW) and Yellow Sea Water (YSW) areas are the two major sinks of atmospheric CO 2 ; the Coastal Upwelling Water (CUW) area is the most important CO 2 source, whereas the Kuroshio Water and Taiwan Current Warm Water areas are weak sources. The entire ECS acted as a sink for atmospheric CO 2 , with a flux of À2.4 to À4.3 mmol C m À2 d À1 during the study period. Identification of the CUW source area suggests that previous studies might have overestimated CO 2 uptake by the ECS in summer. Our results further suggest that high biological production might be responsible for the strong sink in the CDW area but that high input of TA from the Huanghe River, which led to an elevated TA/DIC ratio, could have resulted in formation of a significant CO 2 sink in the YSW area. The present data set represents the most comprehensive CO 2 survey in the ECS to date and can thus be used as a baseline for monitoring future changes in the CO 2 system arising from the construction of the Three Gorges Dam in the middle stretch of the Changjiang River.

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