Consider the following statements:

1. Surface salinity can increase when water is lost through evaporation or freezing.
2. River inflow can reduce surface salinity.
3. Deep-water salinity is comparatively stable because salt is not readily added and water is not readily removed at depth.
4. Lower-salinity water generally rests above denser, higher-salinity water, with a sharp salinity transition called the halocline.

Which of the statements given above are correct?