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# Simulating the Global Ocean

Complex equations representing the physical, biological, and chemical properties of the ocean make up the computer models oceanographers use to learn how massive amounts of ocean water move and influence the rest of the world.

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### Subjects

Earth Science, Meteorology, Oceanography

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The United Kingdom, Scotland, and Ireland are known for their chilly weather, but their coasts, much like those of other Western European countries, tend to be warmer compared to other regions at similar latitudes. Western Europeans can thank the ocean for that. The Gulf Stream, a major ocean current, transports enormous amounts of warm water from the Gulf of Mexico into the seas of Western Europe.

The ocean contains several major currents similar to the Gulf Stream. These currents impact weather, ecosystems, and life all over the world. Because of the importance of ocean circulation for the planet, oceanographers devote themselves to improving computer programs that can simulate the ocean’s circulation. Given the complexity of the oceanic environment, computer models are essential tools for scientists who seek to explore the deepest secrets of ocean circulation.

Computer models of the ocean are programmed to solve complex mathematical equations that simulate the motion (currents) of a fluid (water) on Earth. Known as numerical simulations, these calculations represent the behaviors of a dynamic system like the ocean, where components, such as temperature and salinity, are constantly changing and interacting.

The ocean is an extremely challenging system to model and simulate. Modeling the ocean requires scientists to consider irregular physical features, including changing coastlines, depths, and surrounding land. In their calculations, ocean modelers also consider the temperature and density of water as it moves around the globe. Further, the complex mathematics in ocean circulation models account for influences, such as energy received from the sun, Earth’s rotation, and wind.

Using ocean circulation models, scientists continue to learn about the global ocean as part of a larger complex system. Exploring the complexity of the ocean helps scientists achieve a better understanding of Earth’s atmosphere and climate, as the transport of ocean water around the planet is a key mechanism for regulating the climate. Therefore, ocean models provide simulations that combine, or couple, oceanic and atmospheric features. These kinds of models are essential for predictions of how both natural variability and human-caused changes will influence climate and life on Earth. The models seek to answer various questions, such as: How are ocean temperatures related to local weather? How does the ocean help control the global climate? These are just a couple of the questions that ocean circulation models can help address.

Oceanography, the scientific field that studies the physical and biological properties and phenomena of the ocean, can trace its origins back hundreds of years. However, it was by no means the well-organized field that it is today. As with most other sciences, progress has been incremental. In the early 19th century, scientists did not know much about the circulation of the ocean, and it took oceanographers a century to trace the general patterns of ocean circulation.

In the 1940s, oceanographers began to describe ocean circulation in detail. The first accurate description of ocean circulation described the way in which cold and dense water sinks near Iceland and Greenland and then flows south. Oceanographers were creating the basis for the information scientists use today to develop ocean circulation models. In the 1950s, research in nuclear physics measured radioactive waste from radioactive-bomb tests and industrial byproduct particles dissolved in the ocean. These measurements helped oceanographers to track currents more accurately. Combined with early oceanography theory, this work paved the way for the earliest ocean circulation models. Starting in the 1960s, Earth scientists and computer scientists have worked together to improve ocean models.

Increased concern over climate change was a major impetus for adopting more advanced numerical models of general ocean circulation. Scientists anticipated that the ocean was the major stabilizer of global climatic changes. At the time, oceanographers lacked the data and computer power to simulate the continuous physical, biological, and chemical processes going on in the ocean. Even nowadays, it is not uncommon to hear oceanographers say that we have better maps of places like the moon or Mars than of the ocean.

Ocean modeling advanced as United States government research began contributing to the field. The first ocean circulation models were produced in the late 1960s. During this time, Kirk Bryan and Michael Cox, scientists from the U.S. National Oceanic and Atmospheric Administration (NOAA), developed the first prototype computer model simulating the entire ocean.

At the time, Bryan and Cox had limited computer power to develop and carry out their simulations, but with advances in computing, they and other researchers were able to create more realistic ocean models in the 1980s and 1990s. The rise of supercomputers, in addition to oceanic data gathered by satellites, research vessels, and floating sensors deployed all over the ocean, helped scientists develop models with more realistic oceanic features.

Ocean models generate different outcomes based on the data that is fed into them. But in the actual world, there is only one reality. As an often-quoted statistician, George Box, used to say, “All models are wrong.” This means that computer models are just approximations of the real world. Nonetheless, scientists work hard to make their approximations correspond as closely as possible to reality. For oceanographers, computer models—whatever their limitations—have become an indispensable tool for investigating the dynamics of the ocean.

###### Media Credits

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###### Director
Tyson Brown, National Geographic Society
###### Author
National Geographic Society
###### Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
###### Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
Clint Parks
Roza Kavak

October 19, 2023