Can ocean water be saltier in some areas and less salty in others? A customer e-mailed us with a very interesting question. He had vacationed in several warm water destinations and noticed that in some of the areas, the water tasted saltier than other destinations that he had visited. He wondered if this was true and if so, why is there a difference? I had never really thought about this myself, but when I sat back and remembered the various locations where I had either snorkeled or engaged in scuba diving and realized that he was right. Some places do have a higher concentration of salt than others. Why is the ocean salty? I was intrigued with finding out the answers.
There are some excellent articles written about salt water and many do address the fact that salt content in oceans does vary. I guess, that in order to find out why some areas are saltier than others, we would first have to answer the question of why the earth's oceans are salty to begin with. In a US Geological Survey Publication" by Herbert Swenson, it states that all water, whether fresh or salt contain dissolved chemicals of which scientists refer to as "salts". Even rainwater contains these dissolved chemicals. One would think that if all water contains these "salts", our human taste buds should be able to notice. Mr. Swenson states, "Water is fresh or salty according to individual judgment, and in making this decision man is more convinced by his sense of taste than by a laboratory test. It is one's taste buds that accept one water and reject another." Salt as we know it is a by product of the evaporation of water. As the liquid evaporates, it leaves behind the dissolved chemicals. Continued evaporation would in turn leave a more concentrated amount of the chemicals.
There is no one definitive source for the dissolved chemicals found in water, but one of the greatest contributors would have to be from the weathering and erosion of the igneous rock that makes up what is known as the Earth's crust. The wearing down of mountains and the dissolving actions of rain itself also contributes to the saltiness of water. Sources also include both the solid and gaseous materials that escape from the Earth's crust by way of volcanic vents as well as in the very atmosphere in which we live. Water flowing in the form of creeks, streams and rivers also contributes it's share of eroded materials as the fresh water makes it's way to the oceans.
All of these factors are in an essence feeding the raw materials into the ocean but the catalyst involved in actually adding the salt factor is evaporation of the water with the introduction of heat such as the sun. As the water evaporates the salt is left behind. If this is true then ocean areas that are exposed to the suns rays longer such as near the equator would tend to have saltier water than those areas that do not have a high rate of evaporation such as areas near the North and South Poles. So it would seem that the saltier water would be at places where there is a high evaporation factor involved in the area. Evaporation of water from the surface of the ocean is a part of what is called The Hhydrologic Cycle which is our planet's way of recycling water to ensure that the quantity of water on the planet remains constant. You can read more on The Hhydrologic Cycle here.
The Red Sea area has a high water evaporation rate with very little precipitation. There are also no significant fresh water streams or rivers that feed fresh water into the Red Sea and even though it is connected to the Indian Ocean, which is lower in salt content the connection is too limited to effectively lower the Red Sea's salt content. The saltiest body of water which can not sustain marine life is the Dead Sea. There may in fact be other bodies of water that may be saltier but these two are among the most recognized.
And now we have to figure out why the sky is blue.... Thank you Richard!