Cooled water from the poles sinks as a result of both its salinity and temperature profile. Cooler water is denser than warmer water. Cooler water with high amounts of salt is even more dense. So it sinks and is replaced by less dense and less saline (fresher) water. So yes, the salinity of water increases with depth. See this.
his_rotundity_ t1_is1rcg3 wrote
Reply to Does the salinity of ocean water increase as depth increases? by rhinotomus
Cooled water from the poles sinks as a result of both its salinity and temperature profile. Cooler water is denser than warmer water. Cooler water with high amounts of salt is even more dense. So it sinks and is replaced by less dense and less saline (fresher) water. So yes, the salinity of water increases with depth. See this.