Oceanography, alternately known as oceanology or marine science, is a branch of science that studies the open oceans, coastal regions, and seas. The science of oceanography covers a wide variety of topics and scientific disciplines. Some examples are the movement of water as currents, influences of environmental factors on the direction and strength of currents, marine life including its diversity and threats to that diversity, the generation and dynamics of waves, and the interaction of the ocean and the atmosphere.
Given this diversity, oceanography is a varied science and includes physicists, microbiologists, biologists, ecologists, computer scientists, mathematicians, modelers, and chemists. Research often involves teams of scientists at facilities such as Woods Hole Oceanographic Institution, a large research and educational facility in the eastern United States.
Oceanography has taken on more importance since the 1970s, with the recognition that human activities are altering the ocean. Only a few decades ago, the notion that the chemistry and biology of the global ocean could be altered was dismissed, as the ocean was assumed to be so vast and its volume so great that any influence would be accommodated. However, changes in parameters, including water temperature and pH, have been verified. Some of these changes could be affecting the atmosphere.
Historical Background and Scientific Foundations
The roots of oceanography date back to the fourth century BC, when the Greek philosopher Aristotle made observations on tides. In the eighteenth century, James Cook included observations of the South Pacific Ocean in the chronicles of his voyages. By then, it had been recognized that knowledge of ocean patterns of wind and storms was essential to a safe voyage and exploitation of ocean currents as trade routes.
In addition to his observations that provided the underpinnings for his treatise on evolution, another aspect of Charles Darwin’s voyages on the HMS Beagle in the 1830s was his work on the formation of reefs. Such information proved valuable to seafarers, since collisions with reefs have claimed countless ships and many lives throughout recorded history.
Darwin and his contemporaries were true oceanographers, who were conducting research on the oceans. In Darwin’s time, more was being learned about ocean currents and the variation in ocean depth. The steep drop-off in depth beyond continental shelves was discovered in 1849; the upwelling of colder water from the deeper ocean at the edge of continental shelves brings nutrients closer to the surface, providing food for huge numbers of fish. Knowing where continentals shelves ended was key in increasing the productivity and reliability of the global fishery.
The first oceanography textbook was published in 1855, and oceanography emerged as a scientific discipline in 1871, with the first dedicated oceanography expedition funded by the British government.
By the beginning of the twentieth century, oceanographic research was flourishing around the world. In the United States, the Scripps Institution of Oceanography was established in San Diego in 1903, followed in 1930 by Woods Hole Oceanographic Institute in Woods Hole, Massachusetts.
A few examples of dedicated oceanographic facilities around the globe are the Bedford Institute of Oceanography (Canada), Ocean University of China, Institute of Oceanography and Fisheries (Croatia), National Institute of Oceanography (India), Institute of Marine Research (Norway), P. P. Shirov Institute of Oceanography (Russia), and the National Oceanography Centre (United Kingdom).
By the time Woods Hole was formed, explorations of the ocean were becoming more sophisticated. For example, the technique of echo sounding—in which pulses of sound energy are directed down into the water and the time and pattern of the returning reflected sound waves are used to measure depth and the presence of objects on the seabed—had been used to measure the Atlantic Ocean to depths of 70,000 ft (21,300 m).
By the 1970s, the use of unmanned robots to explore the ocean was accompanied by vehicles capable of carrying researchers. A famous example occurred in 1977, when the manned submersible Alvin was piloted by two Woods Hole researchers to the hydrothermal vents located at the Galápagos Rift, a volcanically active region in the Pacific. Subsequently, vents have been discovered at many locations around the globe, and the unique forms of life in the vicinity of the vents have been well-characterized.
Alvin and the other manned vehicles are termed “human-occupied vehicles” (HOVs) to distinguish them
WORDS TO KNOW
HYDROSPHERE: The total amount of liquid, solid, and gaseous water present on Earth.
IRON FERTILIZATION: A proposal to seed the ocean with iron to stimulate the growth of microorganisms, in order to trap carbon and so lessen the release of carbon dioxide to the atmosphere.
MARIANAS TRENCH: A canyon almost 36,000 ft (11,000 m) in depth located in the floor of the Pacific Ocean; it is the deepest point in the ocean.
SALINITY: Measurement of the amount of sodium chloride in a given volume of water.
from unmanned vehicles that are tethered to a ship, which are termed “autonomous undersea vehicles” (AUVs), and vehicles that can move independently, which are called “remotely operative vehicles” (ROVs).
Echo sounding is just one of many scientific techniques that contribute to oceanography. Classical techniques of physics, chemistry, and biology have been joined by modern computational methods including modeling. Some of the data are collected from instruments that are deployed from ships. There are many designs of unmanned probes that are tethered to a ship by a cable that can be thousands of feet long. The cable also joins the AUV to the command computer aboard ship, allowing the probe to be guided remotely.
The supporting cable once hindered the depth to which a probe could be sent. The weight of a cable tens of thousands of feet in length would be more than could be supported by a ship’s winch and by the ship itself without capsizing. However, in 2006, researchers at Woods Hole completed development of fiber-optic cables that housed the electrical connection to the remote shipboard computer. The fiber-optic cable is a fraction of the weight of the old version, making it feasible to manufacture a tethering cable capable of sending unmanned probes to the Marianas Trench, which at 7 mi (11 km) is the deepest part of the ocean.
ROVs operate independently, “flying” underwater while being remotely controlled onboard ship. Samples of water can be collected during flight of these vehicles for real-time analysis or can be stored for collection upon return of the probe to the ship.
Since 1964, Woods Hole has operated the National Deep Submergence Facility—a fleet of HOVs, AUVs, and ROVs for the benefit of the entire U.S. oceanographic research community.
Still other probes have been designed that are stationary. Whether deployed as buoys on the surface of the
IN CONTEXT: FUTURE CHALLENGES FOR OCEANOGRAPHERS
According to the Intergovernmental Panel on Climate Change (IPCC), climate change already impacts the oceans and seas. The research and monitoring of Earth’s marine systems provide important challenges for current and future oceanographers.
“At continental, regional and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.”
SOURCE: Solomon, S., et al, eds. “IPCC, 2007: Summary for Policymakers.” In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.
ocean or on the seabed, these probes can carry an array of instruments that permit a great deal of data to be gathered simultaneously. As well, buoys can be deployed to drift with a current, collecting data over time to assess the current conditions at different locations.
In 2005, the University of Victoria in Canada deployed a series of seabed instruments in the Pacific Ocean off Canada’s west coast. The project, dubbed VENUS (Victoria Experimental Network Under the Sea) linked the probes via fiber-optic cable to create an undersea observatory that is connected to the Internet. Chemical data including temperature, salinity, turbidity, dissolved gas concentration, current speed and direction, sounds, and both video and still images are collected and sent in real time to labs, classrooms, science centers, and homes around the world. As of 2008, another array is being readied for deployment in the region.
Molecular biology techniques have also been harnessed for oceanographic research and can be used to detect target sequences of bacteria to allow one type of bacterium to be distinguished from another. This gives researchers the ability to analyze water samples to determine the diversity of microbial life in the ocean. In one example, a 2004 cruise to the Sargasso Sea by molecular biologist Craig Venter (1946–) revealed evidence of over one million new genes and thousands of previously unknown species of bacteria. In a second example, a team of Woods Hole researchers published a 2007 study documenting the discovery of a previously unknown bacterium that is able to use gases, such as butane (C4H10) and ethane (C2H6), as food in the absence of oxygen (O). Such research is establishing that a huge diversity of microbial life exists in the ocean.
Impacts and Issues
Oceanography has revealed the huge diversity of life that exists in the ocean, with much still left to discover. New studies are reinforcing the view that the ocean, which covers about 70% of Earth’s surface, is under threat from human activity.
Climate change that is being driven by human activity is altering the world’s oceans by increasing the temperature and the acidity of seawater, and altering the global circulation patterns of water. Studies conducted from virtually all regions of the globe, including both poles, are showing that marine life is being stressed by the changing oceans.
There are few areas of the ocean that have not been affected, according to a 2008 study published in the journal Science. Over 80% of the ocean has been affected by human activities, including overfishing, runoff of agricultural pesticides, pharmaceuticals, and sewage from coastal regions, with more than 40% of the ocean being in need of remediation. Regions of most concern include the North Sea, South and East China Seas, Caribbean Sea, Mediterranean Sea, Red Sea, Persian Gulf, Bering Sea, the western Pacific Ocean, and the east coast of North America.
As well, studies conducted since the 1990s have shown that the ability of the ocean to trap carbon (C) is diminishing, perhaps due to the increasing acidity of the water. As a result, more carbon has been escaping to the atmosphere, where it has contributed to atmospheric warming.
Among the proposals to deal with the diminishing carbon-trapping capacity of the ocean is the seeding of regions of the ocean with iron (Fe), which would stimulate the explosive growth of microorganisms such as algae. These algal blooms could sequester carbon. This approach, which has been termed “iron fertilization,” is controversial, with some critics arguing of the potential harm that could result from the deliberate manipulation of the ocean environment.
In February 2008, the private company Planktos indefinitely shelved its plans for iron fertilization. The initiative had been intended to generate carbon credits that would have been sold to countries and industries seeking to offset their greenhouse-gas emissions without as rigorous an emissions control program as would otherwise have been necessary.
Garrison, Tom S. Oceanography: An Invitation to Marine Science. New York: Brooks Cole, 2007.
Parsons, Tim. The Sea’s Enthrall: Memoirs of an Oceanographer. Victoria, British Columbia, Canada: Trafford Publishing, 2007.
Sverdrup, Keith A. An Introduction to the World’s Oceans. New York: McGraw-Hill, 2008.
Halpern, B. S., et al. “A Global Map of Human Impact on Marine Ecosystems.” Science 319 (2008): 948–952.
Kniemeyer, O., et al. “Anaerobic Oxidation of Short-chain Hydrocarbons by Marine Sulphate-reducing Bacteria.” Nature 449 (2007): 898-901.
Venter, J. C., et al. “Environmental Genome Shotgun Sequencing of the Sargasso Sea.” Science 304 (2004): 66-174.
Victoria Experimental Network Under the Sea (VENUS). April 8, 2008. http://www.venus.uvic.ca (accessed April 21, 2008).
Brian D. Hoyle
OCEANOGRAPHIC SURVEY. Surveys are conducted by the U.S. Navy and civilian government agencies. By their nature, surveys are systematic examinations of the oceans' condition. Although the methods used to conduct these studies have evolved over the last two centuries, expressions such as "sailing in uncharted waters" and "seizing the weather gauge" still attest to their importance.
All mariners know that accurate information about winds, tides, currents, and ocean bottom depth raise the likelihood of a safe passage. In naval terms, superior "environmental intelligence" can allow one side to gain advantage over the other. In the nation's early years, this knowledge was held by individual seafarers and naval officers, or published, with varying degrees of accuracy, by foreign countries and private commercial operations. In 1807, Congress authorized the creation of a Survey of the Coast to obtain and map basic information about the nation's islands, shoals, and anchorages. The U.S. Navy established the Depot of Charts and Instruments in 1830 to supply accurate nautical charts, books, and navigational instruments to the Navy and American shipping interests. The navy published its first charts in 1837, four maps of the fishing banks off the coast of Massachusetts.
In the 1840s, the practice of oceanographic surveying took a significant step forward on both the naval and civilian sides. Recognizing the need to keep all hydro-graphic (pertaining to nautical surveys and charts) materials in one place, in 1842 Congress authorized building a central repository for the Depot's collections. The Depot's superintendent, navy officer Matthew Fontaine Maury, made several key advances in the science of hydrography. First, he and his staff reviewed all of the hundreds of ships' logs in their care. By systematically comparing conditions for the same location in different seasons, Maury could suggest navigational routes that maximized speed and safety. The resulting Wind and Current Charts were soon the reference of choice worldwide. Maury also created a template for a standardized log that all navy captains were required to complete for every voyage and to submit to the Depot. Merchant and foreign vessels received copies of Wind and Current Charts as well in exchange for keeping Maury's logs. Within five years the Depot had received 26 million reports.
Meanwhile, Alexander Dallas Bache took the helm of the U.S. Coast Survey in 1843. Bache raised the level of scientific inquiry in the name of more accurate charts and navigation. His study of the gulf stream, begun in 1845, sought new measures to determine the dynamics of what he suspected was an ever-changing current. For more than a decade, survey ships repeatedly measured temperature at the surface and varying depths, described the bottom depth and character, recorded direction and speed of the currents and the surface and at varying depths, and examined plant and animal life along the way.
Maury and Bache had laid the groundwork for American scientific exploration of the ocean. Their principle of repeated, systematic observation remains the guiding philosophy; only the tools have changed. In some instances, surveys have supported the deployment of new technologies. For example, entrepreneurs who wanted to set up a telegraph connection across the Atlantic required information about the ocean floor. The resulting survey produced the first published depth chart of the Atlantic Ocean, and in 1858 the first telegraphic messages were sent across the ocean via cable lying on the seabed.
New missions sometimes required new technologies. In the 1870s, Coast Survey officer Charles Sigsbee modified a prototype invented by Sir William Thomson (later Lord Kelvin) to construct a machine that used wire instead of rope to take depth soundings. Sigsbee's sounding machine was used to produce a bathymetric (deep-water depth) chart of the Gulf of Mexico in 1874–1875, the first modern and accurate map of any portion of the deep ocean. Sigsbee and biologist Alexander Agassiz collaborated to replace the rope used to raise and lower equipment with lines made of steel wire. Following this idea, Coast Survey officers developed steel wire lines that allowed vessels to anchor at abyssal depths.
By the 1870s, fish and shellfish stocks showed signs of decline and disputes arose among fishermen over the fairness of some of the new netting and dredging techniques. The Coast Survey worked with the newly created U.S. Fish Commission (1871) to conduct dredging operations of their own to survey fish populations. Coast Survey and Fisheries Commission ships discovered hundreds of marine species on their biological research expeditions crossing the world. In 1878, the Coast Survey merged with the Geodetic (size and shape of the earth) Survey to become the U.S. Coast and Geodetic Survey (C&GS), which began to produce the most complete and accurate maps yet of the United States.
During the last quarter of the nineteenth century, Navy oceanographers turned their attention to Central America, where they assisted in locating suitable sites for a canal linking the Gulf of Mexico and the Pacific Ocean, sparing ships the long and dangerous trip around the tip of South America. Nor had the government given up the idea of a Northwest Passage—a route linking the Atlantic and Pacific via the Arctic Sea. Several expeditions were sent to explore the ice; navy civil engineer Robert Peary reached the North Pole in 1909. The disastrous sinking of the Titanic in 1912 also focused new attention on monitoring ice from the polar sea.
During World War I (1914–1918), German submarines posed a new and frightening threat, sinking forty-five U.S. ships while cruising in American waters. American researchers pursued the idea of underwater listening devices as a way to track the U-boats, although the first workable system was not built until after the war. Sonar, the use of sound echoes to locate underwater features and submerged objects, revealed the sea bottom's topography in much greater detail than possible before. In the 1920s, C&GS vessels began to use echo-sounding equipment alongside the traditional wire line to determine accurate values for the velocity of sound in seawater. Survey ships mapped the terrain of the continental shelf, information that would prove valuable for hunting German submarines during World War II (1939–1945). On the eve of World War II, the navy explored the effects of water temperature and salinity on sound transmission underwater, further refining its ability to locate underwater targets.
World War II, and the renewed threat of submarine warfare, spurred more innovative firsts, including deep-sea cameras and electronic navigation systems that used reflected radio waves (radar). Intended originally as a tool in precision aerial bombing, radar was being used by the C&GS to conduct hydrographic surveys by the war's end. Demand for accurate charts had skyrocketed in the wake of Pearl Harbor. The navy's Hydrographic Office dispatched survey ships with onboard printing equipment to accompany the Pacific fleet—43 million charts were printed and issued in one year.
The decades after World War II were notable for collaboration between civilian government agencies, the C&GS, the navy, and academic institutions. One landmark expedition took place in 1955, when the C&GS ship Pioneer was engaged by the navy to survey the West Coast out to several hundred miles offshore. The Scripps Institute of Oceanography attached a newly designed tow to the Pioneer that would measure magnetic properties of the seabed. The project mapped previously unknown long, magnetic stripes that lay along the ocean floor. This discovery, along with the identification of the Mid-Atlantic Ridge Rift Valley in 1959, and C&GS scientists' studies of underwater earthquakes, ultimately led Princeton University professor Harry H. Hess to outline a theory of plate tectonics in the early 1960s.
The 1960s were a time of rapid advancement in oceanographic surveys. The C&GS built a fleet of new survey ships and spent more than a decade mapping large areas of the North Pacific basin for the Seamap Project. New technical advances included the Deep Tow instrument system, which takes multiple measures of the deep sea environment; multibeam sounding systems, which can take simultaneous readings of a swath of ocean floor to generate a map almost instantly; and the submersible re-search vessel Alvin, which can take scientists to unprecedented ocean depths. Research also focused on the inter-action between ocean and atmosphere, which was reflected in the creation of the National Oceanic and Atmospheric Administration (1970) that now encompasses the C&GS as well as the National Weather Service.
Technological advances of the late twentieth century included satellite communication and observation, global positioning, microchip technology, computers small enough to be taken into the field, and more sophisticated modeling techniques. One widely used practical application is the navy's Optimum Track Ship Routing program that uses meteorological and oceanographic data to create a near-real-time forecast of the safest and most efficient passage across the seas. Future surveys are likely to take advantage of microchip technology and satellite communication to obtain large-scale, real-time maps that use remote sensors to transmit data from a vast expanse of ocean. For instance, passive acoustic monitors positioned in the water all over the globe already have been used to detect deep-sea volcanic eruptions and the migratory paths of the blue whale. These technologies, along with even greater computer processing capability, may take oceanographers ever closer to obtaining a pulse of the planet.
Charts from the U.S. Coast Survey. Available from http://chartmaker.ncd.noaa.gov.
Labaree, Benjamin W., et al. America and the Sea: A Maritime History. Mystic, Conn.: Mystic Seaport Museum, 1998.
National Oceanic and Atmospheric Administration. Home page at http://oceanexplorer.noaa.gov.
Naval Oceanographic Office Home page at http://www.navo.navy.mil.
Pinsel, Marc I. 150 Years of Service on the Seas: A Pictorial History of the U.S. Naval Oceanographic Office from 1830 to 1980. Washington, D.C.: Department of the Navy, Oceanographic Office, 1982.
U.S. Department of Commerce, National Oceanic and Atmospheric Administration. Discovering Earth's Final Frontier: A U.S. Strategy for Ocean Exploration, The Report of the President's Panel on Ocean Exploration. Washington, D.C.: October 2000.
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 oceanographic 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 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 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 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 Niño-La Niña, 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.
Float Research: Athletic Shoe and Rubber Duck Spills
A major area of research for physical oceanographers is understanding how currents flow throughout oceans. There are two major ways that they study currents. The flow method involves putting a piece of equipment in the water that measures the speed and direction of the current. By using this equipment to record the flow of water in many different places in the ocean, maps of the currents can be constructed.
A second method of studying currents is called the float method. This method depends on dropping an object that floats into the water and tracking its movement. Usually special instruments called drogues are released into the water, where they float along with currents. These drogues have transmitters that send radio or satellite signals back to scientists identifying their location.
Not all float studies are as technical as drogue studies, however. In May 1990, a terrible storm hit a freighter traveling from Korea to Seattle, Washington. The ship lost 21 cargo containers during the storm, some of which contained more than 30,000 pairs of Nike gym shoes. About six months later, the shoes began washing up on beaches along the northwest coast of the United States and the west coast of Canada. Physical oceanographers asked people who found the shoes to notify them and they used the data to adjust their models of currents in the North Pacific Ocean. In January 1992, another storm hit a cargo ship, which lost a container carrying nearly 30,000 bath toys including rubber ducks and turtles. A number of these toys were studied and recovered along a 500-mile (800-kilometer) stretch of the Alaskan coast.
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.
Juli Berwald, Ph.D.
For More Information
Littlefield, Cindy A. Awesome Ocean Science: Investigating the Secrets of the Underwater World. Charlotte, VT: Williamson Publishing, 2002.
Thurman, Harold, and Alan P. Trujillo. Essentials of Oceanography, 7th ed. Upper Saddle, NJ: Prentice Hall, 2001.
"History of Oceanography." About.com.http://inventors.about.com/library/inventors/bloceanography.htm (accessed on April 7, 2004).
"Oceanography." SeaGrant: MarineCareers.net.http://marinecareers.net/ocean.htm (accessed on August 26, 2004).
"Polynesian History and Origin." PBS: Wayfinders: A Pacific Odyssey.http://www.pbs.org/wayfinders/polynesian2.html (accessed on August 26, 2004).
Shaner, Stephen W. "A Brief History of Marine Biology and Oceanography." University of California Extension Center for Media and Independent Learning.http://www.meer.org/mbhist.htm (accessed on August 26, 2004).
OCEANOGRAPHY. Although oceanography is a twentieth-century scientific discipline forged from European roots, several American developments in the nineteenth century contributed to its modern formation. First, federal interests in mapping the coastlines, charting seaports, and exploring the vast expanse of the United States inspired the work of the U.S. Coast Survey and the Navy's Depot of Charts and Instruments and the U.S. Exploring Expedition (1838–1842). Second, American educational reformers and intellectuals, with their gaze firmly set upon Europe, embarked on an overhaul of the American university system, adding comprehensive curricula in the sciences to colleges and universities for the first time.
In the nineteenth century, concerns had been voiced about the valuable European North Sea fishery and the cod fishery in New England leading to a new federal agency to investigate this resource. The U.S. Fish Commission gained support in 1871,and centered its activities in a laboratory at Woods Hole (Cape Cod) and on two ships dedicated for open-ocean fisheries work. Thus, when an international meeting was held in 1888 at Plymouth, England, to investigate the collapse of the North Sea fishery and when the International Council for the Exploration of the Sea (ICES) was formed in 1902, American scientists were prepared to participate.
Federal support for oceanography at this time was limited. Indeed, when Alexander Agassiz explored the Pacific and Atlantic at the end of the nineteenth century, he did so aboard Coast Survey and Fish Commission vessels but financed the work with his own personal resources. Thus, by the beginning of the twentieth century, Americans lagged behind the British, Germans, and Scandinavians.
American interests in the sea changed, however, first with the sinking of the Titanic (1912), and then from the American experiences in World War I (1914–1918). Both disasters illustrated the need to better understand the oceanic conditions in the North Atlantic and to develop underwater listening devices to protect the country from the new submarine warfare. Lacking a permanent scientific advisory group, President Woodrow Wilson transferred the wartime National Research Council (NRC) to the National Academy of Sciences (NAS) following the war. Continuing its work after 1919, the NRC sponsored re-search that led in the 1920s to the development and refinement of the sonic depth finder and sonar, acoustical devices that greatly improved navigation and enabled surface ships to detect submarines. With its newfound interest in the sea, the NAS established its Committee on Oceanography in 1927, charged with recommending federal oceanic policy.
By the early twentieth century, Americans already established a research presence alongside the ocean, at marine laboratories on both coastlines. The Marine Biological Laboratory (MBL) enhanced the research objectives of the Fish Commission laboratory at Woods Hole. On the West Coast, William Emerson Ritter established the Scripps Institution of Biological Research in La Jolla (near San Diego) in 1903. But neither Woods Hole nor Scripps had an extensive oceanic research program; indeed, American oceanography was barely in its infancy.
In 1924, Thomas Wayland Vaughan, a geologist, was appointed to direct the Scripps Institution of Oceanography (SIO). Three years later, he was named a member of the NAS's oceanographic committee. By the end of 1927, the committee began to support Vaughan's notion that the country needed "oceanographic stations" scattered along the American Pacific and Atlantic coastlines. Then in 1930, the Rockefeller Foundation announced the establishment of three oceanography centers, Scripps Institution in La Jolla, the Oceanographic Laboratories at the University of Washington, and a large new research center at Woods Hole, Woods Hole Oceanographic Institution (WHOI). Thus, by 1930, the institutional framework for the development of American oceanography was set.
The new scientific field developed rapidly, especially with the infusion of research money from philanthropic, federal, and military sources. The U.S. Navy encouraged developments in marine acoustics and related aspects of physical oceanography as it attempted to develop more sophisticated means to monitor the subsurface environment and to build deterrent devices for submarine warfare. This work led to more sophisticated sonar devices and the invention of hydrophones for submarine sound detection. Geological oceanography received attention especially as it offered a means to direct exploration of shallow oceanic basins for oil. Meteorological research continued at most oceanographic laboratories, attempting to understand the relationship between oceanic currents, open ocean wind patterns, and continental weather.
With the outbreak of World War II (1939–1945), oceanography's centrality to the American war effort was demonstrated once again. Of course, much attention focused on the development of submarine warfare. While at the outset of the war, the Allies lost an inordinate number of vessels, wartime matériel, and manpower to the German submarines, oceanographic developments led to dramatic improvements in submarine detection and, ultimately, to the production of submarines and submarine warfare that exacted an even greater toll from the Germans and Japanese. Not surprisingly, therefore, when the war ended in 1945, the federal government established the Office of Naval Research (ONR), which served to ensure funding for oceanographic centers throughout the United States. In addition, the presence of surplus Navy vessels created a surfeit of oceanic research platforms for American oceanographers.
Following the war, the emergence of the Cold War maintained the U.S. Navy patronage for oceanographic research. In addition to its traditional concerns, the Navy became interested in studying the deep ocean basins. This interest involved an extensive hydrophone system, connected by submarine cables to monitor the movement of Soviet submarines, so the deep basins in the Atlantic and Pacific posed potential problems. These same regions attracted increasing attention from oceanographers in the 1950s and 1960s as ideas of seafloor spreading and continental drift began to be discussed again. The existence of mid-ocean ridges and deep-sea trenches gave these notions added credence, but oceanographers needed new technological tools to investigate the bottom of the sea to validate the mechanism for any movement.
Water sampling, temperature measurements, and bottom sediments were soon the target of many research expeditions. Increasingly, this type of research became more expensive, multidisciplinary, and technological, requiring greater financial resources, larger groups of collaborating researchers, and, in many cases, international cooperation from oceanographic experts scattered worldwide.
With multiple partners, oceanography entered its current phase. Continuing to pursue deep ocean research, oceanographers worked to develop a new technological device, the deep-sea submersible. Following dramatic explorations of the earth's deepest marine trenches in the Trieste, American oceanographers argued for the creation of a highly maneuverable submersible that could withstand the demanding conditions of the oceanic depth. The Navy, too, was interested; after all, the hydrophone network it planned would need to be maintained. Then, the loss of the attack submarine Thresher in 1963 under-scored the Navy's interests. Working closely with engineers at Woods Hole and other oceanographers with sub-marine experience, the Alvin was commission in 1964 and the era of submersible research in oceanography entered its most dramatic phase.
By the 1970s, the Navy modified submersibles for its own purposes and Alvin and its successors were pressed into basic oceanographic research. In the late 1970s, oceanographers soon discovered sea vents adjacent to oceanic ridges worldwide. Even more dramatic, however, were the faunal forms inhabiting these vents. For the first time, luxuriant "gardens" of deep-sea animals, all new to science, were described. Plate tectonics was not just con-firmed, but the physical, chemical, and biological aspects of the vents opened a new era for oceanographic research. By the close of the century, new ideas concerning the origin of life, conditions for the emergence of life, sources for the chemical composition of seawater, and deep ocean sources for thermal conductivity created fresh perspectives for oceanographic work. Coupled with exciting extensions of the century-long work to study open-ocean currents, including work on the longitudinal oscillations of large masses of warm and cold water in the central gyres of the oceans that seem to affect the earth's climate, oceanography at the beginning of the twenty-first century promised to maintain its prominent role in scientific research.
Benson, Keith R., and Philip F. Rehbock, eds. Oceanographic History: The Pacific and Beyond. Seattle: University of Washington Press, 2002.
Mills, Eric. Biological Oceanography, An Early History, 1870–1960. Ithaca, N.Y.: Cornell University Press, 1989.
Oreskes, Naomi, ed. Plate Tectonics: An Insider's History of the Modern Theory of the Earth. Boulder, Colo.: Westview Press, 2001.
Oceanography, the study of the oceans , is a combination of the sciences of biology, chemistry, geology, physics , and meteorology .
Ancient explorers of the ocean were sailors and fishermen who learned about marine biology by observing the sea life and discovering when it was most plentiful. They observed the effects of wind , currents, and tides , and learned how to use them to their advantage or to avoid them. These early humans discovered that salt could be retrieved from seaweed and grasses.
Polynesians combined what they knew about the weather , winds, and currents to investigate the Pacific Ocean, while the Phoenicians, Greeks, and Arabs explored the Mediterranean Sea. The early Greeks in general and Herodotus (484–428 b.c.) in particular believed that the world was round. Herodotus performed studies of the Mediterranean, which helped sailors of his time. He was able to take depth measurements of the sea floor by using the fathom as a unit of measure, which was the length of a man's outstretched arms. Today the fathom has been standardized to measure 6 ft (1.8 m) in length.
Aristotle (384–322 b.c.) also studied marine life. One of his contemporaries, a geographer by the name of Poseidarius, studied the tides and their relationship to the phases of the Moon .
Pliny the Elder a.d.23–79) was a Roman naturalist who discovered, by studying marine biology, that some organisms had medicinal uses. One of his predecessors, Seneca (4 b.c.–a.d.65) predicted that interest in the oceans would fade and "a huge land would be revealed," foreshadowing the age of exploration and discovery of the New World. A period of about 1,000 years followed when no new studies were done until the fifteenth century. Christopher Columbus performed oceanographic studies on his voyages.
Captain James Cook , the explorer, was one of the first scientists to study the oceans' natural history. A surge in scientific studies took place in the seventeenth century, during which scientists tried for the first time to combine the scientific method with sailors' knowledge.
U.S. Navy lieutenant Matthew Fontaine Maury (1806–1873) is considered the father of modern oceanography. It was during the nineteenth century that the name was given to the science.
In December 1872, the British ship HMS Challenger began a four-year journey, which lasted until May of 1876. This was the first major study of the ocean approached from a scientific viewpoint, and since that time significant strides have been made. The advent of submersible vehicles allowed for first-hand study of the ocean floor and the water above it. In 1900, Prince Albert of Monaco established two institutes to study oceanography.
Two areas of focus within oceanography today are physical and chemical oceanography. Physical oceanography is the study of ocean basin structures, water and sediment transportation, and the interplay between ocean water, air and sediments and how this relationship affects processes such as tides, upwellings, temperature , and salinity. Findings aid oceanic engineers, coastal planners, and military defense strategists. Current areas of research also include oceanic circulation, especially ocean currents and their role in predicting weather-related events, and changes in sea level and climate.
Chemical oceanography investigates the chemical make-up of the oceans. Many studies in this area are geared to understanding how to use the oceans' resources to produce food for a growing population.
Even though the study of the oceans has entered the technological age, there is much still unexplored and unknown. Oceanographers of the 1990s use satellites to study changes in salt levels, temperature, currents, biological events, and transportation of sediments. Deep-sea studies are underway using unmanned robotic submersible craft to study ocean floor hydrothermal vents, sea-floor spreading , and subduction zones that lie beneath the ocean floor. As scientists develop new technologies, the future will open new doors to the study of oceanography.
See also Bathymetric mapping; Beach and shoreline dynamics; Continental drift theory; Continental shelf; Convergent plate boundary; Coral reefs and corals; Delta; Depositional environments; Desalination; Douglas sea scale; Dunes; Earth (planet); Earth science; Earth, interior structure; El Nino and La Nina phenomena; Geothermal deep ocean vents; Global warming; Gulf of Mexico; Gulf stream; Guyots and atolls; Hawaiian Island formation; History of exploration II (Age of exploration); Hydrogeology; Hydrologic cycle; Hydrothermal processes; Icebergs; Land and sea breeze; Latitude and longitude; Marine transgression and marine regression; Mid-ocean ridges and rifts; Ocean circulation and currents; Ocean trenches; Oceans and seas; Offshore bars; Petroleum; RADAR and SONAR; Red tide; Saltwater encroachment; Seawalls and beach erosion; Tides; Wave motions
Oceanography from Space
Oceanography from Space
The use of space satellite data for ocea n observations allows marine scientists to view biological, chemical, and physical interactions within the oceans on regional and global scales. Satellite studies have revolutionized our ideas of how the ocean works. Satellite sensors measure a myriad of different phenomena including: sea surface temperature, surface wind, ocean color and productivity, ocean height, tides, and currents.
Several different in struments are used to collect oceanographic measurements. For example, the TOPEX/Poseidon satellite measures the height of the sea surface using an altimeter . The altimeter flies aboard the satellite at approximately 1,335 kilometers (830 miles) above Earth and emits a radar pulse that reflects off the sea surface. Because the speed of the pulse and location of the satellite are known, scientists can calculate the height of the sea surface.
In addition, the strength of the radar signal depends on the size of the surface ripples, which are in turn related to the wind speed, allowing the wind speed to be calculated. Because currents are detectable as slopes in the sea surface, the world's ocean currents can also be identified and monitored.
Altimeter data is also used for identifying the topography of the seafloor. For example, when there is a topographic high, such as a mountain on the seafloor, then there is a related topographic high or "mountain" in the sea level. This seafloor feature can be a subsurface seamount , or it may be a local increase in density in the Earth's crust.
A radiometer can be used to collect surface temperature data and ocean color data. A radiometer measures the amount of the Sun's visible light and infrared radiation reflected off the ocean. Examples of radiometers include the Coastal Zone Color Scanner (CZCS) and SeaWiFS (Sea-viewing Wide Field-of-view Sensor).
The temperature of the sea surface can be calculated using the infrared portion of the data. Because currents and water masses vary considerably in temperature, this data is particularly useful in observing currents and circulation processes.
Eddies are one feature in particular that can be identified using an infrared radiometer. These are generated by large-scale currents, such as the Gulf Stream. Eddies can affect the distribution of marine life and can last for many years before dissipating. Locating such eddies and studying their dynamics can help researchers track pollution such as oil spills and determine where marine life may be located.
Ocean color can be determined by measuring the portions of the visible spectrum reflected from the ocean surface. It can indicate a number of things to an oceanographer, such as amount of plankton and amount of vegetation. The color of the ocean changes slightly, from a bright blue to a dark blue or black when plankton float freely or concentrate in areas. These concentrations are called blooms. These colors can indicate to scientists the productivity of the oceans and potential for greater amounts of wildlife since plankton are the basis of the marine food web and without plankton all marine life would suffer.
Satellite data have become accurate and dependable enough that they is now integrated with other forms of marine data collection. In addition, satellite data provide a large-scale view of ocean dynamics that otherwise would be unavailable. What has emerged is exciting new information about vast areas of previously unstudied open water.
see also Algal Blooms in the Ocean;Ocean Currents; Ocean-Floor Bathymetry; Ocean Mixing; Weather and the Ocean.
Alison Cridland Schutt
Mellor, George L. Introduction to Physical Oceanography. New York: Springer Verlag, 1996.
Ross, David A. Introduction to Oceanography, 5th ed. New York: HarperCollins College Publishers, 1995.
Sandwell, David T. "Geophysical Applications of Satellite Altimetry." Reviews of Geophysics. supplement (1990):132-137.
This encyclopedia contains several photographs taken from satellites. Entries with notable images include:
- "Algal Blooms in the Ocean"
- "Bays, Gulfs, and Straits"
- "Geospatial Technologies"
- "Marginal Seas"
- "Microbes in the Ocean"
- "Ocean Mixing"
- "Ocean-Floor Sediments"
Oceanography, the study of the oceans, is a combination of the sciences of biology , chemistry , geology , physics , and meteorology .
Ancient explorers of the ocean were sailors and fishermen who learned about marine biology by observing the sea life and discovering when it was most plentiful. They observed the effects of wind , currents , and tides , and learned how to use them to their advantage, or to avoid them. These early humans discovered that salt could be retrieved from seaweed and grasses .
Polynesians combined what they knew about the weather , winds, and currents to investigate the Pacific Ocean, while the Phoenicians, Greeks, and Arabs explored the Mediterranean Sea. The early Greeks in general and Herodotus (484-428 b.c.) in particular believed that the world was round. Heroditus performed studies of the Mediterranean, which helped sailors of his time. He was able to take depth measurements of the sea floor by using the fathom as a unit of measure, which was the length of a man's outstretched arms. Today the fathom has been standardized to measure 6 ft (1.8 m) in length.
Aristotle (384-322 b.c.) also studied marine life. One of his contemporaries, a geographer by the name of Poseidarius, studied the tides and their relationship to the phases of the moon .
Pliny the Elder (a.d. 23-79) was a Roman naturalist who discovered, by studying marine biology, that some organisms had medicinal uses. One of his predecessors, Seneca (4 b.c.-a.d. 65)predicted that interest in the oceans would fade and "a huge land would be revealed." We know, of course, that this prediction came true with the discovery of North America . A period of about 1,000 years followed when no new studies were done until the fifteenth century. Christopher Columbus performed oceanographic studies on his voyages.
Captain James Cook, the explorer, was one of the first scientists to study the oceans' natural history. A surge in scientific studies took place in the seventeenth century, during which scientists tried for the fist time to combine the scientific method with sailors' knowledge.
U.S. Navy lieutenant Matthew Fontaine Maury (1806-1873) is considered the "father" of modern oceanography. It was during the nineteenth century that the name was given to the science.
In December 1872 the British ship HMS Challenger began a four-year journey, which lasted until May of 1876. This was the first major study done from a purely scientific viewpoint, and since that time significant strides have been made. The advent of submersible vehicles allowed for first-hand study of the ocean floor and the water above it. In 1900, Prince Albert of Monaco established two institutes to study oceanography.
Two areas of focus within oceanography today are physical and chemical oceanography. Physical oceanography is the study of ocean basin structures, water and sediment transportation, and the interplay between ocean water, air and sediments and how this relationship effects processes such as tides, upwellings, temperature , and salinity. Findings aid oceanic engineers, coastal planners, and military defense strategists. Current areas of research include oceanic circulation—especially ocean currents and their role in predicting weather-related events—and changes in sea level and climate.
Chemical oceanography investigates the chemical make-up of the oceans. Many studies in this area are geared to understanding how to use the oceans' resources to produce food for a growing population. In addition, the oceans may contain future sources of medicine, provide us with alternative energy , and help us to better protect our environment.
Even though the study of the oceans has entered the technological age, there is much we still do not know. Oceanographers of the 1990s use satellites to study changes in salt levels, temperature, currents, biological events, and transportation of sediments. As scientists develop new technologies, the future will open new doors to the study of oceanography.
See also Ocean.
Mid-Ocean Ridges and Rifts
Mid-ocean ridges and rifts
The ocean floor is mountainous and uneven, much like Earth's surface. As oceanographers began mapping the ocean bottom, they discovered that the sea floor is full of vast rising slopes, or ridges, and dramatic open valleys, or rifts. During World War II, oceanographer William Maurice Ewing began mapping the complex ocean bottom with sophisticated instruments such as sonar depth finders and underwater cameras that helped trace the contours of the ocean bottom. Ewing set out to measure and record a massive chain of undersea mountains called the Midatlantic Ridge. When Ewing and his crew began mapping the massive ridge, they encountered a problem: the sonar beams were bouncing back. This problem led to another great discovery. They realized that there were frequent oceanic earthquakes occurring along the ridge. This was an exciting discovery because it opened up the possibility that oceanic earthquakes might be connected to ridges and rifts. Using data from other expeditions, Bruce Charles Heezen (b. 1924) more accurately measured the Midatlantic Ridge as he began mapping the ocean floor. The Ridge measured up to 1.9 miles (3 km) high and 45,954 miles (73,940 km) long. Interestingly, however, he detected a gully in the ridge that led to the Heezen-Ewing theory in 1958, which formally recognized the Midatlantic Ridge as containing a rift. Their discovery sparked interest in other scientists and explorers who questioned the existence of other rifts in ocean ridges.
In the late 1950s, American and Soviet oceanographic vessels began mapping the ocean floor so that their nuclear submarines could navigate deep underwater. The ensuing data provided maps that revealed extraordinary natural phenomena. Submerged peaks and undersea ridges form a continuous mountain chain that reaches up to 10,000 feet (3,048 m) and measures 40,000 miles (64,360 km). This mid-ocean ridge system circles the earth several times and is now known as one of Earth's dominant features, extending over an area greater than all the major land mountain ranges combined. Along a great deal of its length, the ridge system is sliced down its middle by a sharp gully, a rift that is the outlet of powerful heat flows. Temperature surveys demonstrate that heat seeps out of the earth in these mountainous regions of the middle Atlantic, adding to the complexity of the ocean floor. This evidence of heat emitting from Earth's giant cracks and faults helped reveal the existence of earthquakes and volcanic eruptions beneath the ocean. Most of this heat and movement take place in the Atlantic Ocean where the ridge is steeper and more jagged than in the Pacific or Indian Oceans .
In some of the most active volcanic areas another unusual natural phenomenon takes place, discovered by Harry Hammond Hess . Hess studied the isolated mountains rising from the ocean floor and discovered "sea-mounts," which he named guyots in honor of the Swiss-American geographer Arnold Henry Guyot (1807–1884). Hundreds of these strange undersea protrusions lie under the Pacific Ocean, all of which were probably sunken islands created from volcanic lava . Some of these guyots broke away and gradually wandered further away from the volcanoes. Before oceanographers studied the floor of the great oceans, there was little evidence to support the continental drift theory , which assumed that all the great landmasses were once joined in one supercontinent. Hess's discovery of guyots and other studies of seafloor movement helped reveal the spreading movement of the ocean floor. Hess proposed that hot rock swelled from deep within the earth, constantly forcing the ridges and rifts to part and spread. Later these discoveries of seabed movement helped build on the findings of Alfred L. Wegener's thoery of continental drift.
See also Sea-floor spreading
Oceanography is the scientific study of the oceans, which cover more than 71 percent of Earth's surface. It is divided into four major areas of research: physical, chemical, biological, and geological.
Physical oceanography is the study of basic activities of the oceans such as currents, tides, boundaries, and even evaporation. Chemical oceanography is the study of the chemical parts of the sea and the presence and concentration of chemical elements such as zinc, copper, and nitrogen in the water. These two fields are the main focus of oceanography today. Current areas of research include oceanic circulation—especially ocean currents and their role in weather-related events—and changes in sea level and climate. Also, as the population of the planet continues to increase, oceanographers have begun to conduct research on using the oceans' resources to produce food.
Biological oceanography is the study of all life in the sea, including plants, animals, and other living organisms. Since the oceans provide humans with vital food, biological oceanographers look for ways to increase these yields to meet growing populations.
Geological oceanography is the study of the geological structure and mineral content of the ocean floor. This includes mineral resource extraction (removal), seafloor mapping, and plate tectonics activities that offer clues to the origin of Earth. (Earth's crust is made up of large plates that fit together loosely. The study of these plates and their movement, especially their ability to cause earthquakes, is called plate tectonics.)
Ocean research vessels
The era of modern oceanography was opened with the four-year ocean exploration expedition of the H.M.S. Challenger, beginning in 1872. The Challenger was the first vessel used to systematically record information about all the oceans except the Arctic, including their depths, circulations, temperatures, and organic life.
Sophisticated sonar and magnetic technology on subsequent voyages by other vessels have greatly increased scientists' knowledge of the oceans, helping them make such important geological discoveries as
seafloor spreading (by which new oceanic crust is created) and plate tectonics. All ocean research ships are essentially floating laboratories. Many are operated and financed by the U.S. Navy, often in conjunction with a university or other institution.
Oceanographers of the twenty-first century use satellites to study changes in salt levels, temperature, currents, biological events, and transportation of sediments. As scientists develop new technologies, new doors will open on the study of the world's oceans.
[See also Ocean ]
Oceanography is the study of the oceans. Oceanography is an example of a science that involves diverse approaches; it is a combination of the sciences of biology, chemistry, geology, physics, and meteorology.
Physical oceanography is the study of ocean basin structures, water and sediment transportation, and the interplay between ocean water, air, and sediments and how this relationship effects processes such as tides, upwellings, temperature, and salinity. Findings aid oceanic engineers, coastal planners, and military defense strategists. Current areas of research include oceanic circulation—especially ocean currents and their role in predicting weather-related events—and changes in sea level and climate.
Chemical oceanography investigates the chemical make-up of the oceans. Many studies in this area are geared to understanding how to use the oceans’ resources to produce food for a growing population. In addition, the oceans may contain future sources of medicine, provide us with alternative energy, and help us to better protect our environment.
Even though the study of the oceans has entered the technological age, there is much we still do not know. Modern-day oceanographers use satellites to study changes in salt levels, temperature, currents, biological events, and transportation of sediments.
Biological oceanography involves the study of the known life forms in the ocean, and the constant discovery of new life forms. Oceanographers at institutions such as Woods Hole Oceanographic Institution realize that the ocean life we know of likely represents a fraction of the ocean’s life. The deep ocean, once thought to be devoid of life, in fact harbors a variety of life.