The Earth’s ocean makes up about 97 percent of the planet’s surface. It is an enormous body of water that plays a vital role in the survival of every living organism on Earth. It is also responsible for most of the world’s weather, temperature, and food supply. The ocean is so vast, in fact, that only about 80 percent of it has ever been mapped or explored by humans.
Oceans are divided into different zones based on their physical and biological characteristics. The first, the photic zone, includes all open water at or near the surface and is defined by the depth at which light intensity is less than 1 percent of its surface value. This is the only area of the ocean where photosynthesis takes place.
Photosynthesis is the process by which plants and microscopic algae use sunlight, water, carbon dioxide, and nutrients to produce organic matter or “food”. This process also produces oxygen, which ocean organisms need to breathe. The photic zone is also the area where ocean life gathers to form large groups called schools.
This swarm of organisms provides the raw material for larger ocean life, such as fish and whales. It is also the source of energy for many of the processes that create and shape the ocean, such as water circulation, tidal movements, and temperature changes.
Other important aspects of the ocean include its rich supply of oxygen, which comes from plankton and dead organisms that drift down from above. The ocean also provides a constant supply of nutrients that are vital to ocean life. Elements like nitrogen, phosphorus, and potassium are continuously recycled through the ocean food chain.
Ocean currents, which flow through the ocean, are influenced by a variety of factors, including temperature variations, wind, and the Coriolis effect. These currents transport heat from the tropics toward the poles, while moving cooler deep water back to the Equator. This keeps the oceans from becoming extremely hot or cold and allows the recycling of nutrients.
In addition to these processes, the movement of ocean water is influenced by its gravity and the rotation of the Earth. The Coriolis effect causes the paths of large systems, such as winds and ocean currents, to veer to the right in the northern hemisphere and to the left in the southern hemisphere.
The Ocean is divided into regions based on geographic features, the amount of solar radiation it receives, and the temperature differences of its surface waters. It is further divided into two areas based on its distance from land: the neritic zone, which covers coastal waters; and the oceanic zone, which encompasses all open seawater. Within each region, the ocean is divided into several different zones based on its temperature, salinity, and other physical characteristics. Distinct boundaries, called thermoclines (temperature), haloclines (salinity), and chemoclines (chemistry) separate the different zones of the ocean. These boundaries are important to ocean scientists, as they provide the information needed for studying how the oceans function and interact with other parts of the Earth system.