Presented at the 2016 Ocean Sciences MeetingThe expansive archipelago stretching from Southeast Asia to Australia is comprised of a network of seas of varied dimensions. Freshwater enters the region through precipitation and river discharge, leaving a unique spatial and temporal thumbprint. Here we use Aquarius data to investigate the evolution of sea surface salinity in the Southeast Asian seas. Ocean processes including the inflow of more saline surface water from the western Pacific and inter-sea advection redistribute this freshwater signal throughout the Southeast Asian seas as it spreads towards the Indian Ocean. We conclude that the observed sea surface salinity annual and inter-annual variability of the Southeast Asian seas points to the importance of ocean processes, particularly inter-sea advection.