The ocean is Earth’s largest network of salt water covering more than three-quarters of the planet. Its name is derived from the Greek god Oceanus, who was personified as an enormous river circling the world.
When we speak of the ocean, we usually mean one of the four major areas of global seas: the Pacific, Atlantic, Indian and Arctic Oceans. But we also use the term to describe larger landlocked bodies of salt water called lakes, seas or ponds. These are not as large as the oceans, but they can still contain life and be influenced by the same forces that influence the larger oceans.
Oceans are an incredibly important part of the Earth’s ecosystems. They provide food, shelter and transportation to millions of ocean animals and marine plants. They are also critical to the carbon cycle — how carbon (as carbon dioxide and calcium carbonate) moves between air, land and the sea. Oceans are the biggest natural reservoirs of carbon in the world.
There are more than 500,000 miles (680,000 km) of coastline in the world’s oceans. This coastline is home to many coastal cities, ports and fishing villages. It is also the source of much of the world’s most valuable natural resources — minerals, fuel, food and other commodities that are crucial to the global economy.
The oceans are the source of some of our most essential medicines. The chemical compounds that make up the hormones and steroids found in seawater help regulate human and animal bodies, as well as control the body’s temperature, blood pressure and blood sugar levels. The oceans also help create and recycle the oxygen we breathe.
In addition to being a major source of food and medicine, the oceans are also the great storehouse of the planet’s most abundant mineral — calcium carbonate. This is the building block of a wide variety of shells – from tiny, microscopic foraminifera and pteropods to giant oysters and mussels. These shells play an extremely important role in the global ocean food webs, and are critical to the movement of carbon between Earth’s atmosphere, land and sea.
Ocean currents are powerful and long-lasting movements of seawater. They shape Earth’s global climate patterns by redistributing heat, and move huge amounts of nutrients around the globe — including the carbon that humans release into the atmosphere.
The motion of ocean water is mainly driven by four factors: the Sun’s radiation, wind, gravity and the Earth’s rotation. The radiation influences prevailing wind patterns that cause ocean water to bunch up in hills and valleys, while wind drives currents. Gravity pulls the ocean waters toward the equator, and the Earth’s rotation steers them.
The most important thing you can do to save the oceans is learn about their complex, vital ecosystems and how your everyday actions affect them. You don’t need to be a captain of a ship to have an impact on the ocean: everything from single-use plastic containers to fertilizers and pesticides can harm sea creatures and reef systems.