What leads to the variation in the salinity of the sea water?

The amount of salt present in sea water is influenced by various factors. Following factors leads to the variation in the salinity of the sea water:

1. Salinity increases in area where evaporation is more.
2. Salinity increases in land locked areas.
3. Salinity decreases if there is more rainfall.
4. Salinity is less where the river meets the sea.
5. Salinity is less where the ice melts in large quantity.