Unlocking the Mystery of the Ocean's Saltiness - Woods Hole Oceanographic Institution

Introduction:

Have you ever wondered why the water in the ocean tastes so salty, while freshwater bodies like lakes and streams taste fresh? The answer is much more complicated than you might think. Let's dive in and explore the science behind it all.

I. Sources of Salt in Water:

When it rains, water falls from the sky and reacts with carbon dioxide in the air to form carbonic acid. This slightly acidic rainwater then falls onto rocks on land, dissolving tiny bits of salts and minerals. These washed into streams, lakes, and rivers which carry salt and minerals into the ocean water. However, freshwater bodies like streams, lakes, and rivers do not become too salty because rainwater regularly replenishes them.

II. Salt in the Ocean:

Water from different sources flows into the ocean with varying salinity levels. The freshwater from the streams and rivers entering the ocean carries a lot of salts and minerals which make the water salty. Additionally, seafloor vents add more salts and minerals to the ocean, and hot water seeping into cracks in the Earth’s crust dissolves salts and minerals from the rock. Believe it or not, the ocean's saltiness varies across oceans. However, the area between the equator and the poles tends to be saltier than the rest of the ocean.

III. Ocean Life:

Iron, zinc, and copper are some of the many salts and minerals found in the ocean's waters. Ocean life makes use of most of these minerals, but not sodium and chloride, which are the main ingredients in table salt. Because these elements are left behind, the sodium and chloride levels in the ocean have built up over time, causing the water to become saltier. While some seas and lakes are saltier than the ocean, the saltiness of the ocean is on average about 3.5%.

IV. Salinity Variations:

The salinity of ocean water varies depending on its location. Ocean water that is closer to the equator and the poles tends to be less salty than the areas between them. Some lakes, such as Mono Lake in California and the Caspian Sea in Asia, are even saltier than the ocean, possibly due to limited rainfall and high temperatures causing water to evaporate. As water evaporates from these land-locked bodies of water, salts are left behind. Over time, salt levels continue to go up.

Conclusion:

The salinity of ocean water is determined by the various sources of salt and minerals that dissolve into it, including rainwater, seafloor vents, and hot water seeping into cracks in the Earth's crust. Ocean life uses many of these minerals, but the ocean's sodium and chloride levels keep building up, causing the water to become saltier. The salinity of the ocean varies depending on its location, with some seas and lakes even being saltier. The science behind the ocean's saltiness is truly fascinating, and there's always more to discover.