The Primary Reason for Ocean Salinity
The ocean is salty primarily because of runoff from land. As rainwater falls and flows over rocks and soil, it dissolves various minerals, including salts. These dissolved salts are then carried by rivers and streams into the oceans, accumulating over geological timescales.
Sources of Ocean Salt
Beyond continental runoff, salts are also introduced to the ocean through hydrothermal vents on the seafloor. These vents release mineral-rich fluids from the Earth's crust into the water. Volcanic eruptions, both on land and underwater, also contribute gases and solids that eventually dissolve into seawater. The most abundant salt is sodium chloride, which is common table salt.
How Salts Accumulate in the Ocean
Imagine a continuous cycle: rivers constantly deliver dissolved salts to the sea. When ocean water evaporates, it leaves the salts behind, increasing their concentration. This process has been ongoing for billions of years. While some salts are removed by marine organisms or absorbed into sediments, the input consistently exceeds removal, maintaining the ocean's overall salinity.
Importance and Effects of Salinity
Ocean salinity is crucial for marine ecosystems, affecting everything from buoyancy to the types of life that can thrive. It also plays a significant role in ocean currents, as denser, saltier water tends to sink, driving global thermohaline circulation. This contributes to climate regulation and the distribution of heat around the planet.