How salinity and temperature affects the seawater?
Salinity and temperature are conservative properties of seawater that directly affect the density of seawater. This is an extremely important property because it in turn directly affects upwelling and downwelling of oceans and some major oceanic currents. This is because if a denser body of water is sitting on top of a less dense body of water, the denser part of the water column will turn over (sink) to get to a more stable water column state. This leads to water mixing of nutrients and oxygen for organisms living in the water column. Typically the saltier the water, the higher the density and also the colder the water, the higher the density. So because of this, cold and salty water (Antarctic and Arctic) are the most dense bodies of water and typically stay towards the bottom of the ocean floor.