Excessive freshwater (rain) flowing into a shallow sea can change the salinity.
You could increase the salinity of the ocean by adding salt or removing water (ie: by evaporation).
The lowest areas of salinity in an ocean are near where fresh water rivers empty into them. This is because the influx of fresh water creates an area of lower salinity compared to the remainder of the ocean.
There are a number of things that could happen to the salinity of an ocean if it's depth increased. The salinity would likely also increase.
rain, snow, and melting ice add fresh water to the ocean, lowering the salinity there. Salinity is also lower near the mouths of large rivers. These rivers empty great amounts of fresh water into the ocean.
some areas have a higher and lower elivation witch causes it to be deep or shallow
ocean because the ocean or you could say the sea is filled with salt water. :)
Lower rates of evaporation so more water to dilute it.
A river flowing into the sea is causing the decrease in salinity
The continental shelf is the shallow part of the ocean.
In open ocean evaporation affects the salinity of the oceans, in closed oceans the lack of sunrays cause greater salinity levels.
Rainfall does not directly affect ocean salinity, as rainwater is freshwater and dilutes the salt content in the ocean. Other factors such as evaporation, ice formation, and river input can influence ocean salinity levels.