By general definition, oceanography is a science that explores the oceans, and includes their extent and depth, physics, chemistry, biology, as well as the exploitation of their resources. This is a rather concise definition and aptly outlines the major fields of the discipline, with the exception of history and the current state of the seafloors, the foundations where the ocean resides. As this book primarily covers applied research related to oceanography, it makes sense to take a look at the big picture first, from the history of the ocean, to the history of ocean research, to the subdisciplines of ocean science.
In the solar system’s planets, Earth is in the perfect position. Its size and mass, distance from the Sun, orbit around the Sun, and its rotation cycle all intervene to form an ideal condition that produces an average temperature of approximately 15°C in most regions of its surface. This allows the coexistence of all three states of water: liquid, solid, and gaseous. As we know, the most abundant state is liquid water, which forms a watery blanket covering the majority of Earth’s surface—the world’s oceans. Therefore, our planet is also commonly known as the water planet.
The total area of the world’s oceans is about 360 million square km, accounting for 72% of the total area of the surface. The average depth of the global ocean is about 3800 m, with a maximum depth of 11,033 m, deeper than the highest peak on Earth (the peak of Mount Everest is 8848 m). The total volume of the world’s oceans is approximately 1.37 billion cubic km, accounting for 97% of the total amount of water on Earth. Another way to look at this number is that the amount of water in the ocean would give us a thick “water blanket” of 2600 m in depth, if Earth were a perfect sphere.
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