Salinity refers to the saltiness or salt content in a body of water and has a dramatic affect on ocean circulation or currents. Increased salt concentration in water effects its density, so that fresh water is less dense and floats to the surface while saltier water is denser and tends to sink. Salinity and temperature both influences seawater density and buoyancy thereby driving ocean stratification, mixing, and water mass formation. Greater seawater density is usually found in colder temperatures which results in a depression of the sea surface height. In warmer water the temperature is higher and the seawater less dense, resulting in an increase of surface sea height. These height and density differences also drive the circulation of the ocean. The changes in density bring warm water poleward on the surface to replace the sinking water driving the global thermohaline circulation within the ocean called the Global Conveyor.