Oceanography, also called marine science, is the study of the ocean. Its goal is to discover unifying principles that can explain data measured in ocean waters, in the organisms that live in the ocean, and on the land surrounding the ocean. Oceanography is a broad subject, drawing on techniques and theories from biology, chemistry, physics, mathematics, geology, and engineering.

Oceanography is usually divided into four different areas of research. Marine biology or biological oceanography focuses on life (animals, plants, and bacteria) in the ocean. Chemical oceanography studies the substances that are dissolved in the ocean.

Physical oceanography attempts to understand the movement of water and the relationships between oceans and the atmosphere (mass of air surrounding Earth). Marine geology is directed at understanding geological features of the ocean floor, such as the composition of the seafloor and the movement of tectonic plates (moving plates of Earth’s crust).

History of oceanography

Oceanography as an academic subject is relatively young, probably dating from the 1950s. But interest and study of the ocean has existed for thousands of years. Fifth century Greek historian Herodotus recorded the first documented ocean exploration. He wrote that the Phoenicians sailed from the Mediterranean Sea through the Red Sea and along the coast of Africa before 600 b.c.e. As early as 2000 b.c.e. the Phoenicians may have sailed as far as England.

The Polynesians were also great ocean explorers, crossing the Pacific as early as 1500 b.c.e. in order to colonize many Pacific islands. Much of this early exploration was associated with trade, however in the process of sailing the oceans, sailors accumulated knowledge of navigation, currents (the movement of water), tides, and geography.

European ocean exploration blossomed in the 1400s when Christian armies invading Spain discovered Greek and Arab writings and maps of the oceans in Islamic libraries. This stimulated a period of oceanographic exploration by the Portuguese, Dutch, English, and Spanish.

Many of the oceano-graphic advancements made during this time were aimed at solving practical problems, such as sailing faster, navigating more accurately, and avoiding nearshore obstacles. With the skills they developed, the Europeans dominated ocean exploration for nearly 400 years.

The first expedition focused entirely on collecting scientific data of the ocean took place from 1872 to 1876 and was funded by The Royal Society of London. The H.M.S. Challenger was a war ship that was remodeled to accommodate scientific research.

The Challenger expeditions explored the biology and physics of every ocean except the Arctic during a journey of 68,000 miles (109,000 kilometers). The data from the expedition took 23 years to analyze and fills 50 volumes.

In the 1800s, the United States began establishing government agencies to improve the safety of sailing vessels, protect fisheries, and defend its coasts. The Naval Depot of Charts and Instruments was established in 1830, followed by the Fish Commission in 1871.

Two important oceanographic institutions were founded on Cape Cod: the Marine Biological Laboratory in 1888 and the Woods Hole Oceanographic Institute in 1930. Both of these institutions are still active places of research today.

In the 1950s, government support of oceanographic research and education increased. Universities became involved in competing for government and international grants to study various aspects of oceanography. This cooperative effort between educational institutions and governments is what drives oceanographic research in modern day.

Biological oceanography

Biological oceanographers (or marine biologists) focus on the patterns and distribution of marine organisms. These scientists work to understand why certain animals, plants, and microorganisms are found in different places and how these organisms grow.

A variety of factors influence the success of a certain species in any location, including the chemistry and physical properties of the water. In turn, the biological organisms in the ocean affect the oceans on a global and local level.

Biological oceanographers study all types of organisms that live in the ocean, from the very small to the very large. They investigate patterns and distributions of the microscopic organisms including viruses (which are not really organisms, but genetic material such as DNA that do have the ability to reproduce), bacteria, and plankton (free-floating animals and plants). They also study the larger animals and plants, like kelp, seaweed, marine invertebrates (animals without a backbone), fish, and marine mammals.

They incorporate information and techniques from a broad range of disciplines including chemistry, physics, remote sensing (the use of specialized instruments, such as satellites, to relay information about one location to another location for analysis), paleontology (study of fossils), and geography (study of Earth’s surface) for their research.

Chemical oceanography

Chemical oceanographers study the chemicals that are dissolved in the ocean waters. Different parts of the ocean contain varying concentrations of gasses, salts, and other chemical components. These variations are due to the impact of the atmosphere, surrounding lands, seafloor, and biological organisms in the ocean water. Chemical oceanographers work to develop theories that explain the various patterns throughout the oceans.

One of the more important problems facing chemical oceanographers today is understanding the concentration of and changes in carbon dioxide in the ocean. Carbon dioxide is a major greenhouse gas, meaning it holds a lot of heat when it is found as a gas in the atmosphere.

Burning fossil fuels for industry and in cars releases carbon dioxide into the atmosphere, where it contributes to global warming. The ocean, however, can remove a lot of carbon dioxide from the atmosphere. Carbon dioxide readily combines with seawater. It then goes through a series of complex chemical reactions before it becomes a solid material called calcium carbonate.

Calcium carbonate can be buried in the sediments (particles of gravel, sand, and clay) at the bottom of the ocean. This means that the ocean has the potential to act as a "sink" for a lot of the carbon dioxide in the atmosphere. Chemical oceanographers are working to determine just how large the sink is and how quickly it can act.

Physical oceanography

Physical oceanographers study the physical properties of the ocean. These include temperature, salinity, density, and ability to transmit light and sound. In turn, these fundamental physical characteristics affect the way that ocean currents move, the forces associated with waves, and the amount of energy absorbed by the ocean.

The temperature and salinity of the water affect the density of the water. Cooler and saltier water sinks while warmer and fresher water floats. This seemingly simple property of the ocean drives much of the water circulation throughout the globe. Density also affects the way that sound travels through water and the buoyancy (ability to float) of marine organisms.

Some of the projects that physical oceanographers are studying include understanding trends in climate. Satellites measure ocean temperatures over the whole globe to try to discriminate between local changes in ocean temperature, like the El Nino-La Nina, a cycle that brings warm water and storms to the Eastern Pacific every 5 to 7 years, from more large scale changes, like global warming.

Marine geology

Marine geologists study the geological features of the ocean. These scientists try to determine the composition of the inner Earth by looking at special places on the seafloor where the tectonic plates are moving away from each other. In these places, called spreading centers, material from the inner Earth rises to the seafloor.

Marine geologists analyze the chemical and physical makeup of this material to gain an understanding on how the Earth was formed. The shifting of tectonic plates also can cause earthquakes. Marine geologists also study the movements of the tectonic plates in the ocean to try to predict where and when earthquakes will occur.

Another focus for marine geologists is the sediments found on the seafloor. These sediments are made up of particles from the land, dead marine plants and animals, precipitates (solid material) from chemical reactions, and even material from space. Studying the chemical and physical composition of sediments provides information on how the Earth’s climate has changed over time and where valuable resources, like oil and minerals, can be found.