1. One Big Ocean

The world has ONE BIG OCEAN!

The ocean is all around us. 71% of the planet Earth is covered in water. The ocean is the planet's most prominent feature and holds 97% of the water on Earth. There are 5 major ocean basins: Atlantic, Pacific, Indian, Arctic and Southern. All of these oceans are interacting with the earth, and with each other, in incredible ways that support all life on the planet. Each basin is composed of the sea floor and all of its geological features such as islands, trenches, mid-ocean rifts, and rift valleys. Earth's highest peaks, deepest valleys, and flattest plains are all found in the ocean.


The ocean is all connected through the water cycle. All water starts, and ends, in the ocean. No matter where it is in the world, water can always end up back in the ocean. Water is moved constantly across the planet and through out the ocean as well. Throughout the ocean there is one interconnected circulation system that is powered by the winds, tides, Earth's rotation, sun, and water density differences.


The Coriolis effect is an important contributor to the movement of water across the surface of the Earth. The Coriolis effect is caused when the rotating system (the Earth) experience a force acting perpendicular to the direction of motion and to the axis. In other words, the rotation of the earth causes the water, or air, to curve. Winds and water tend to deflect to the right of the northern hemisphere and to the left of the southern hemisphere.

The Coriolis effect causes large systems of circulating ocean currents. This is called a Gyre, a large system of circular ocean currents that are formed by the Coriolis effect and global wind patterns. This movement of water is essential for the regulating of temperature, salinity, and nutrient flow throughout the ocean. The five major gyres are the North Atlantic, South Atlantic, Indian, North Pacific and South Pacific gyres, but gyres of all sizes are found in the ocean.

It is this circulation of water that connects the ocean. This Global Ocean Conveyor Belt moves water throughout all of the ocean basins. This transports energy (heat), matter, and organisms throughout the ocean. It also means that changes in the ocean circulation may have a large impact on the climate and cause changes to the ecosystem. We will discuss these in later sections.

Just as the movement of water circulates around the planet, the structure of the ocean can shift as well. Sea level is the average height of the ocean relative to the land, taking into account the tides. Sea level changes as plate tectonic cause the volume of the ocean basins and the height of the land to change. It changes as ice camps on land melt or grow. It also changes as sea water expands and contracts when ocean water warms or cools.


Even though the ocean may shift or change, we now know that the ocean is not an infinite structure, and neither are it's resources. Science has managed to measure the volume of the ocean: 1.3 billion cubic kilometers of seawater exist on the planet. While that may feel like a lot, it also means that there is a line drawn in the sand. Since Earth is a closed system, with all of its resources being recycled back into the system, there is no extra water that we can add into the system. So what happens when we cannot use the resources that have been relying on the ocean for since life on the planet began? Knowing that the ocean is finite helps us to understand what a treasure our ocean is to life on earth.

Before moving on to the next session, complete the Properties of Water Assignment. Then you may test your knowledge with the One Big Ocean Quiz and earn your first Ocean Literacy Badge. Once the quiz is complete you may move on to Ocean Shapes Earth.


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