A layer where the density gradient is greatest within a body of water.
An ocean current is generated by the forces such as breaking waves, terms of temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of the Moon and Sun.
Two layers of water with the same salinity, the warmer water will float on top of the colder water. Though, temperature has a greater effect on the density of water than salinity does.