Sea Water vs. Fresh Water
Seawater Versus Freshwater
A fundamental characteristic of oceans is their saltiness; apart from oxygen and hydrogen, seawater is primarily composed of sodium and chloride, which together form table salt. The salinity of seawater is measured as the concentration of salt (in grams) per liter of water, usually averaging around 35 grams of dissolved salts per liter, represented as 35‰. Salinity in the ocean commonly ranges between 33-37 grams per liter (33‰ – 37‰). However, just as atmospheric pressure varies in different regions, so does ocean salinity. The Atlantic Ocean boasts the highest salinity among the five ocean basins, with a noticeable decrease in salinity observed near the equator and at the poles, occurring for different reasons.
At the equator, the tropical regions face persistent heavy rainfall, which dilutes the surface salinity of the ocean with freshwater. As one moves toward the poles, rainfall diminishes, and with increased sunshine, evaporation rates escalate, leading to higher salinity levels. Conversely, as freshwater evaporates from the ocean into the atmosphere, it raises salinity, whereas melting ice near the poles once again reduces surface salinity. The most saline areas of the ocean are where evaporation rates are highest or in large bodies of water cut off from oceanic outlets. The Red Sea and the Persian Gulf are noted for their highly saline water, with approximately 40‰, due to high evaporation rates and minimal freshwater inflow.
How do these two water types compare? When a cubic foot of seawater evaporates, it leaves behind roughly 2.2 pounds of salt, whereas the same volume of water from North America’s Great Lakes leaves only about 0.01 pounds, or roughly one-sixth of an ounce. Thus, seawater is approximately 220 times saltier than our primary freshwater sources.
Related Links:
- Ground Water High in Salt Content
- Are Salt Levels in Drinking Water a Health Concern?
- Can Seawater Be Made Suitable for Drinking?