Oceans get their salt from minerals and sand. Rivers pick up minerals, and dump them, along with water, in the ocean. Water evaporates from the ocean, leaving the minerals behind. Over a long period of time, more and more minerals are left in the ocean, making up the salinity. Salinity of the ocean is measured in parts per thousand.
The ocean is comprised of almost every element in the system, however, the most common elements in seawater are the major gases: nitrogen, oxygen, and carbon dioxide. In addition, chlorine ions, sodium ions, sulfur oxide ions, magnesium ions, calcium ions, and potassium ions are quite common in seawater.
Density difference in water makes the water layer. Heat makes water less dense because the water expands as it heats up. Cold water sinks because it is more compact and dense than warmer water. This can cause a phenomenon quite similar to cold and hot air fronts. High oxygen is usually found in a deeper layer because warmer water carries less oxygen.
Surface water is found at a depth average of about 0-200 meters deep. Intermediate water is from 200m-1500m. Deep water can be found from 1500m-4000m, while bottom water rests at 4000m and below since nobody is quite sure how deep the ocean is.
Antarctic Bottom Water is the densest water in the ocean. Its salinity constantly changes because when ice forms on the surface, it leaves salt and minerals behind, leaving the water much more saline. This happens because when water freezes, it forms a lattice structure which excludes salt because salt is too big to fit through it. The water freezes, turning to ice, and leaving the salty water behind even more concentrated. Despite the fact that the bottom waters are the coldest, no ice is found there because ice floats. Although the Antarctic bottom water salinity varies constantly, it is the most constant of the Antarctic waters. This is because the upper waters are affected before it is. The bottom water is about -0.5° Celsius....