Ocean water is salty because it contains high concentrations of dissolved minerals, collectively known as salts. About 3.5% of ocean water is salts, depending on where it is found; equatorial waters tend to be saltier, while northern waters are slowly becoming cooler. There are several factors that make the ocean salty, and scientists are very interested in the salt content of the ocean as it contributes to the flow of currents through the ocean, in a process known as thermohaline circulation.
Salt comprises about 3.5% of ocean water.
One of the reasons the ocean is salty has to do with the ocean floor, which contains a huge variety of minerals and dissolved organic matter that is slowly eroded and stirred up by the ocean’s movements. As the ocean erodes the ocean floor, the salt content increases. The ocean floor is also constantly renewing, another way to make the ocean salty, as seafloor propagation releases even more dissolved minerals into the water in the form of emissions from hydrothermal vents and seafloor cracks.
The salt content of the ocean increases as the ocean floor erodes.
Another thing that makes the ocean salty is the runoff that flows into the ocean. This might seem counterintuitive to you, as rivers, streams, and lakes are likely to taste fresh to you. However, this water also contains dissolved salts, although the concentration is lower than that of the ocean. These salts reach the ocean with river water, which eventually evaporates from the ocean to fall back to Earth as rain, repeating the process.
The reason these salts don’t accumulate in things like lakes is because inland bodies of water have an outlet. What makes the ocean salty is the slow concentration of salts over time, because salts in the ocean have nowhere to go. Lakes and streams, on the other hand, are constantly recirculating their water. To find out what happens when a lake has no runoff, you can look at the Dead Sea, which has a notoriously high concentration of salts.
Now that you know what makes the ocean salty, you might be interested in experimenting with your own personal limit to tasting salt. If you drink a glass of tap water, you will likely perceive it as “fresh”. In fact, tap water has a number of dissolved salts, and it is these salts that give tap water its flavor. If you think water is tasteless, try drinking a glass of distilled water, which will taste incredibly stale and bland in comparison. If you add a pinch of common salt to distilled water, it will taste significantly fresher; the same pinch added to fresh water can make it a little too salty for you.