what factors can cause the salinity of water to rise? and fall?

Answer 1

when water evaporates from salt water, the salt stays behind. When salt water freezes, the salt is concentrated in the remaining liquid. When icebergs melt, they dilute the salt water. When it rains or snows into salt water, it dilutes the salt. When rivers run into saltwater, etc.

Answer 2

Temperature of the water, higher temperature water will hold more salt.