A long-term volume transport time series estimated by combining in situ observation and satellite altimeter data in the northern South China Sea

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We deployed five pressure-recording inverted echo sounders (PIES) along a satellite altimeter track across the continental slope of the northern South China Sea (NSCS) from October 2012 to July 2014, and obtained a time series of volume transport (VT PIES ) across the sec- tion from their records. Applying the empirical relation- ship between VT PIES and the satellite altimeter sea surface height anomaly difference across the section, we obtained a time series of volume transport (VT NSCS ) over 22 years from 1992 to 2014. The VTNSCS shows a small mean value of −1.6 Sv (1 Sv = 10 6 m 3 s −1 ) (i.e., toward the south- west), but a significant seasonal reversal and mesoscale eddy induced fluctuations ( −11.8 to 19.7 Sv). The monthly mean of VTNSCS over 22 years shows a maximum (3.6 Sv) in July and a minimum (−7.3 Sv) in December. This is the first long time series of volume transport for the NSCS based on in situ data.