Buzz
Many well-known facts about the world's oceans are familiar to all. For example, anyone who's felt the force of a wave at the beach has also experienced the ocean's signature taste: salt. Whether you're at Queensland's shores or the Jersey Shore, seawater always has that salty flavor. The salinity of the ocean is one of the main features that distinguishes it from freshwater bodies such as rivers and lakes. But what exactly is responsible for making the ocean saltier than a plate of boardwalk fries?
To understand the ocean's saltiness, it helps to know what salt is and where it originates. In chemical terms, salt is a compound made up of two types of oppositely charged ions. When an atom has more protons than electrons, it becomes a positively charged ion. Atoms with more electrons than protons become negatively charged ions, or anions. Ions with opposite charges attract each other to form chemical compounds.
Table salt is made of sodium chloride, where sodium is the positive ion and chloride is the negative one. While sodium and chloride are the primary components of ocean salt, they aren't the only minerals responsible for the sea's salinity. 'Ocean salt isn't just sodium and chloride—it's a blend of ions like magnesium and calcium too, most of which come from rocks on land,' says Dr. Morgan Raven, an organic geochemist and geobiologist, and assistant professor of earth science at the University of California Santa Barbara, in an interview with Mytour.
The majority of the ocean's salt originates from rocks. Rainwater, which contains dissolved carbon dioxide, has a slight acidity, and when it falls, it erodes land-based rocks. The minerals from these rocks flow into rivers and streams, which then transport the salts to the ocean. Sodium and chloride make up around 85 percent of the ocean's ions, while magnesium and sulfate contribute about 10 percent.
Not all the salt that reaches the ocean remains there. Since salt is vital for life, much of it is absorbed by marine animals. However, with a constant influx of runoff from the land, the salt levels in the ocean stay relatively stable. Another source of ocean salt comes from hydrothermal fluids. Deep-sea vents, heated by magma beneath the Earth's crust, trigger chemical reactions between seawater and nearby minerals. Underwater volcanoes also play a role in adding more salt to the ocean.
While the entire ocean contains salt, the exact saltiness varies by location. 'One reason oceanographers rely on salinity to study the ocean is that there are only a few ways it can change, all of which happen at the surface or the seafloor,' explains Raven. 'For instance, surface waters in the Mediterranean Sea are saltier than those in the equatorial Pacific due to higher evaporation in dry areas, which concentrates salt, while rain in the Equator dilutes it.'
Salinity doesn't naturally belong to seawater—it's the result of a continuous exchange of ions entering and leaving the ocean. This process occurs in other bodies of water as well, but their ion intake often isn't enough to make the water noticeably salty. That's why rivers and streams that bring salt to the ocean are still considered freshwater: Rainwater dilution typically balances out the ions. In contrast, the ocean acts as the world's salt sink, and no level of dilution can alter that fact.
