Sea surface salinity (SSS), an essential climate variable that is sensitive to changes in the global water cycle, varies seasonally in many places due to annual variations in rainfall and evaporation, as well as vertical mixing and advection. The seasonal variability of global mean SSS, with maximum/minimum SSS in March/September has been increasing in amplitude since the start of the satellite observation era in 2010. This variability, with a range of 0.03, implies approximately 2 cm of water leaving from and returning to the surface of the ocean over the course of the year, with its 0.01 increase in range since 2011, roughly equating to an additional 0.7 cm of water cycling out and returning to the ocean. This trend is consistent with predictions of an accelerating global water cycle on a warming planet.