Ocean: A vast, continuously moving body of salt water that covers 71 percent of Earth’s surface. Oceans supply the world with half of its oxygen and play an important role in transferring heat from the Equator to the poles. Evaporation from the oceans’ surface also brings rain to many places on the planet.
While oceanographers have a lot to learn from studying the ocean, they’ve already made some incredible discoveries. The ocean contains towering mountain ranges and deep canyons (known as trenches) similar to those on land. For example, the peak of Mount Everest in the Himalayas would not even break the surface of the Pacific Ocean’s Mariana Trench or Philippine Trench. The ocean is also home to an astonishing array of sea life, from the tiny plankton that provides us with food and air to the enormous whales that make up one-third of the Earth’s animal population.
The ocean is also home to the largest single source of heat in our atmosphere, and it is a source of constant temperature change, helping to control the climate on our planet. As a result, the ocean is critical to our very survival.
Scientists know a great deal about the world’s oceans because they are such an immense natural laboratory, but there is still much more to discover. One area of research is the impact of human activities on the environment, particularly the rapid increase in atmospheric carbon dioxide levels. This phenomenon is known as ocean acidification, and it is happening faster than at any time in the last several million years.
Acidification of the ocean occurs when carbon dioxide combines with seawater. This reduces the water’s pH, which is measured on a scale from zero to 14, with seven being neutral and below seven being acidic. For millions of years, the ocean maintained a slightly alkaline state, but since the Industrial Revolution began in the 1800s, carbon dioxide concentrations have increased and the seas have become more acidic.
The current rate of CO2 emissions could bring the atmospheric level to 500 ppm by 2050 and 800 ppm by 2100, which would make the oceans an estimated 30 to 100 times more acidic than they were in pre-industrial times. This increase in acidity will have severe impacts on marine life.
Museum palaeontologist Prof Richard Twitchett explains that ocean acidification changes the balance between hydrogen ions and carbonate ions in seawater, making the water more acidic. This has implications for the growth of coral reefs, for instance, as well as for the ability of some fish to sense predators and to hunt prey.
National Geographic Explorer Marcello Calisti is working to learn more about the ocean floor and its life through a new type of undersea exploration vehicle. Using inspiration from the way an octopus moves, he’s developing a system of legged locomotion that allows the vehicle to traverse underwater surfaces and travel at speeds far higher than any other robot currently on the market.