Presented at the 2014 AGU Fall MeetingNewly available sea surface salinity (SSS) data from the Aquarius together with in-situ hydrographic data are used to explore the spatial and temporal characteristics of SSS in the South China Sea (SCS). An evaluation of daily Aquarius data indicates that there exists a negative bias of 0.45 psu for the version 3.0 dataset. The root-mean-square differences (RMSD) for daily Aquarius SSS is about 0.53 after correcting the systematic bias, and those for weekly and monthly Aquarius SSSs are 0.45 and 0.29 psu, respectively. Nevertheless, the Aquarius SSS shows a reliable freshening in 2012, especially in the northern SCS, as the in-situ data does. The northern SCS freshening was around 0.40 psu, which is larger than Aquarius uncertainty indicated by the monthly RMSD. This freshening was caused by a combined effect of local freshwater flux and Kuroshio intrusion. By comparing with 2011, we attribute reduced Kuroshio intrusion as the cause for the freshening over the northern SCS in 2012. In the region near the Mekong River mouth, the river discharge during flood season plays an important role.