Oceanography and Studying the Sea

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mooring for scientific devise
Satellite imagery is used to study regions of the ocean. Slight color gradations are used to determine the water’s health and study things like suspended sediments, water depth, seagrass cover and water flow. The deep sea is studied with advanced multi-beam sonar systems used in mapping the sea floor; remotely-operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) like the Remote Environmental Monitoring Units (REMUS); “submersibles” like the Titanic-discovering Alvin which are tethered to mother ships; scientific buoys that bob up and down on the ocean surface, collecting data; and deep diving human occupied vehicles (HOVs).

On studying the ocean, Robert Stewart wrote in the “Introduction to Physical Oceanography”: 1) Ocean processes are nonlinear and turbulent” and “we don’t really understand the theory of non-linear, turbulent flow in complex basins. Theories used to describe the ocean are much simplified approximations to reality. 2) Observations are sparse in time and space. They provide a rough description of the time-averaged flow, but many processes in many regions are poorly observed. 3) Numerical models include much-more-realistic theoretical ideas, they can help interpolate oceanic observations in time and space, and they are used to forecast climate change, currents, and waves. Nonetheless, the numerical equations are approximations to the continuous analytic equations that describe fluid flow, they contain no information about flow between grid points, and they cannot yet be used to describe fully the turbulent flow seen in the ocean. [Source: Robert Stewart, “Introduction to Physical Oceanography”, Texas A&M University, 2008]

By combining theory and observations in numerical models we avoid some of the difficulties associated with each approach used separately. Continued refinements of the combined approach are leading to ever-more-precise descriptions of the ocean. The ultimate goal is to know the ocean well enough to predict the future changes in the environment, including climate change or the response of fisheries to over fishing.


Websites and Resources: National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org


The science of oceanography began in 1872 century when the British government and the Royal Society launched a major oceanic expedition based from the HMS Challenger, a 265-foot converted naval warship. For four years the ship circled the globe and took measurements, collected creatures in nets, examined them with microscopes and preserved them in alcohol. The expedition collected 4,700 species new to science but not before two men went insane, two drowned and one committed suicide.

According to the “Introduction to Physical Oceanography”: The ocean is one part of the earth system. It mediates processes in the atmosphere by the transfers of mass, momentum, and energy through the sea surface. It receives water and dissolved substances from the land. And, it lays down sediments that eventually become rocks on land. Hence an understanding of the ocean is important for understanding the earth as a system, especially for understanding important problems such as global change or global warming.

Trieste — went 10 kilometers deep in the Marianas Trench in 1960

At a lower level, physical oceanography and meteorology are merging. The ocean provides the feedback leading to slow changes in the atmosphere.As we study the ocean, I hope you will notice that we use theory, observations, and numerical models to describe ocean dynamics. None is sufficient by itself. [Source: Robert Stewart, “Introduction to Physical Oceanography”, Texas A&M University, 2008]

Important terms: 1) Geophysics is the study of the physics of the earth. 2) Physical Oceanography is the study of physical properties and dynamics of the ocean. The primary interests are the interaction of the ocean with the atmosphere, the oceanic heat budget, water mass formation, currents, and coastal dynamics. Physical Oceanography is considered by many to be a subdiscipline of geophysics.

3) Geophysical Fluid Dynamics is the study of the dynamics of fluid motion on scales influenced by the rotation of the earth. Meteorology and oceanography use geophysical fluid dynamics to calculate planetary flow fields. 5) Hydrography is the preparation of nautical charts, including charts of ocean depths, currents, internal density field of the ocean, and tides. 6) Earth-System Science is the study of earth as a single system comprising many interacting subsystems including the ocean, atmosphere, cryosphere (places with ice) , and biosphere, and changes in these systems due to human activity.

History of the Study of the Ocean

Robert Stewart wrote in the “Introduction to Physical Oceanography”: Our knowledge of oceanic currents, winds, waves, and tides goes back thousands of years. Polynesian navigators traded over long distances in the Pacific as early as 4000 B.C. Pytheas explored the Atlantic from Italy to Norway in 325 B.C.. Arabic traders used their knowledge of the reversing winds and currents in the Indian Ocean to establish trade routes to China in the Middle Ages and later to Zanzibar on the African coast. And, the connection between tides and the sun and moon was described in the Samaveda of the Indian Vedic period extending from 2000 to 1400 B.C. (Pugh, 1987). Those oceanographers who tend to accept as true only that which has been measured by instruments, have much to learn from those who earned their living on the ocean. [Source: Robert Stewart, “Introduction to Physical Oceanography”, Texas A&M University, 2008]

Modern European knowledge of the ocean began with voyages of discovery by Bartholomew Dias (1487–1488), Christopher Columbus (1492–1494), Vasco da Gama (1497–1499), Ferdinand Magellan (1519–1522), and many others. They laid the foundation for global trade routes stretching from Spain to the Philippines in the early 16th century. The routes were based on a good working knowledge of trade winds, the westerlies, and western boundary currents in the Atlantic and Pacific (Couper, 1983: 192–193).

The early European explorers were soon followed by scientific voyages of discovery led by (among many others) James Cook (1728–1779) on the Endeavour, Resolution, and Adventure, Charles Darwin (1809–1882) on the Beagle, Sir James Clark Ross and Sir John Ross who surveyed the Arctic and Antarctic regions from the Victory, the Isabella, and the Erebus, and Edward Forbes (1815–1854) who studied the vertical distribution of life in the ocean. Others collected oceanic observations and produced useful charts, including Edmond Halley who charted the trade winds and monsoons and Benjamin Franklin who charted the Gulf Stream.

Bathysphere from 1934

From the earliest times to 1873, was a period characterized by systematic collection of mariners’ observations of winds, currents, waves, temperature, and other phenomena observable from the deck of sailing ships. Notable examples include Halley’s charts of the trade winds, Franklin’s map of the Gulf Stream, and Matthew Fontaine Maury’s Physical Geography of the Sea. The period from 1873–1914 has been called the Era of Deep-Sea Exploration, characterized by a few, wideranging oceanographic expeditions to survey surface and subsurface conditions, especially near colonial claims. The major example is the Challenger Expedition, but also the Gazelle and Fram Expeditions. From 1925 to 1940 was an era of national systematic surveys, characterized by detailed surveys of colonial areas.

Slow ships of the 19th and 20th centuries gave way to satellites, drifters, and autonomous instruments toward the end of the 20th century. Satellites now observe the ocean, air, and land. Thousands of drifters observe the upper two kilometers of the ocean. Data from these systems, when fed into numerical models allows the study of earth as a system. For the first time, we can study how biological, chemical, and physical systems interact to influence our environment.

The period between 1947 and 1956 was characterized by long surveys using new instruments. These include seismic surveys of the Atlantic by Vema leading to Heezen’s maps of the sea floor. The period between 1957 and 1978 was characterized by multinational surveys of ocean and studies of oceanic processes. Examples include the Atlantic Polar Front Program, the norpac cruises, the International Geophysical Year cruises, and the International Decade of Ocean Exploration Multiship studies of oceanic processes include mode, polymode, norpax, and jasin experiments. Since 1978 global surveys of oceanic processes from space by satellites such as Seasat, NOAA 6–10, Nimbus–7, Geosat, Topex/Poseidon, and ERS–1 & 2. Since 1995 there has been a greater emphasis on global studies of the interaction of biological, chemical, and physical processes in the ocean and atmosphere and on land using in situ (which means from measurements made in the water) and space data in numerical models.

What Do Oceanographers Do?

An oceanographer studies the ocean. Oceanography covers a wide range of topics, including marine life and ecosystems, ocean circulation, plate tectonics and the geology of the seafloor, and the chemical and physical properties of the ocean. [Source: NOAA]

Several thousand marine scientists are busy at work in the United States dealing with a diversity of important issues — from climate change, declining fisheries, and eroding coastlines, to the development of new drugs from marine resources and the invention of new technologies to explore the sea.

Just as there are many specialties within the medical field, there are many disciplines within oceanography. Biological oceanographers and marine biologists study plants and animals in the marine environment. They are interested in the numbers of marine organisms and how these organisms develop, relate to one another, adapt to their environment, and interact with it. To accomplish their work, they may use field observations, computer models, or laboratory and field experiments.

Chemical oceanographers and marine chemists study the composition of seawater, its processes and cycles, and the chemical interaction of seawater with the atmosphere and seafloor. Their work may include analysis of seawater components, the effects of pollutants, and the impacts of chemical processes on marine organisms. They may also use chemistry to understand how ocean currents move seawater around the globe and how the ocean affects climate or to identify potentially beneficial ocean resources such as natural products that can be used as medicines.

Geological oceanographers and marine geologists explore the ocean floor and the processes that form its mountains, canyons, and valleys. Through sampling, they look at millions of years of history of sea-floor spreading, plate tectonics, and oceanic circulation and climates. They also examine volcanic processes, mantle circulation, hydrothermal circulation, magma genesis, and crustal formation. The results of their work help us understand the processes that created the ocean basins and the interactions between the ocean and the seafloor.

Physical oceanographers study the physical conditions and physical processes within the ocean such as waves, currents, eddies, gyres and tides; the transport of sand on and off beaches; coastal erosion; and the interactions of the atmosphere and the ocean. They examine deep currents, the ocean-atmosphere relationship that influences weather and climate, the transmission of light and sound through water, and the ocean's interactions with its boundaries at the seafloor and the coast.

All of these fields are intertwined, and thus all oceanographers must have a keen understanding of biology, chemistry, geology, and physics to unravel the mysteries of the world ocean and to understand processes within it.

Deployment of oceanographic research vessels

Much of the Ocean Has Not Been Explored

More than eighty percent of our ocean is unmapped, unobserved, and unexplored. Much remains to be learned from exploring the mysteries of the deep from mapping and describing the physical, biological, geological, chemical, and archaeological aspects of the ocean to understanding ocean dynamics, developing new technologies, and unlocking other secrets of the ocean. [Source: NOAA]

The ocean is the lifeblood of Earth, covering more than 70 percent of the planet's surface, driving weather, regulating temperature, and ultimately supporting all living organisms. Throughout history, the ocean has been a vital source of sustenance, transport, commerce, growth, and inspiration. Yet for all of our reliance on the ocean, more than three quarters of this vast, underwater realm remains unmapped, unobserved, and unexplored.

Given the high degree of difficulty and cost in exploring our ocean using underwater vehicles, researchers have long relied on technologies such as sonar to generate maps of the seafloor. Currently, less than ten percent of the global ocean is mapped using modern sonar technology. For the ocean and coastal waters of the United States, only about 35 percent has been mapped with modern methods.

Role of Observations in Oceanography

Observations are essential for understanding the ocean. Accuracy, precision, and linearity are key concepts in the discussion of observations. Robert Stewart wrote in the “Introduction to Physical Oceanography”: Accuracy is the difference between the measured value and the true value. Precision is the difference among repeated measurements. The distinction between accuracy and precision is usually illustrated by the simple example of firing a rifle at a target. Accuracy is the average distance from the center of the target to the hits on the target. Precision is the average distance between the hits. Thus, ten rifle shots could be clustered within a circle 10 centimeters in diameter with the center of the cluster located 20 centimeters from the center of the target. The accuracy is then 20 centimeters, and the precision is roughly 5 centimeters. Linearity requires that the output of an instrument be a linear function of the input. Nonlinear devices rectify variability to a constant value. So a nonlinear response leads to wrong mean values.[Source: Robert Stewart, “Introduction to Physical Oceanography”, Texas A&M University, 2008]

Important Concepts: 1) The ocean is not well known. What we know is based on data collected from only a little more than a century of oceanographic expeditions supplemented with satellite data collected since 1978. 2) The basic description of the ocean is sufficient for describing the timeaveraged mean circulation of the ocean, and recent work is beginning to describe the variability. 3) Observations are essential for understanding the ocean. Few processes have been predicted from theory before they were observed. 4) Lack of observations has led to conceptual pictures of oceanic processes that are often too simplified and often misleading.

5) Oceanographers rely more and more on large data sets produced by others. The sets have errors and limitations which you must understand before using them. 6) The planning of experiments is at least as important as conducting the experiment. 7) Sampling errors arise when the observations, the samples, are not representative of the process being studied. Sampling errors are the largest source of error in oceanography. 8) Almost all our observations of the ocean now come from satellites, drifters, and autonomous instruments. Fewer and fewer observations come from ships at sea.

Use of Ocean Observations and Data

Ocean observations and data help track, predict, manage, and adapt to changes in the marine environment. Coastal communities use ocean observing data to prepare for storms, floods and other natural disasters. NOAA orchestrates the collection of ocean data through a federal, regional, and private-sector partnership called the U.S. Integrated Ocean Observing System, or IOOS®. This system helps the nation track, predict, manage, and adapt to changes in our marine environment. [Source: NOAA]

IOOS data are increasing our understanding of how oceans drive storms to allow meteorologists to develop earlier, more accurate weather predictions. Store managers use these forecasts to decide whether to stock hurricane supplies or beach towels in their stores. Fishermen typically use weather and water data to make informed decisions about when it is safe to head to sea.

Through state-of-the-art high frequency radar systems and other technologies, IOOS scientists can also track ocean currents in near real time. By improving our ability to monitor the speed and direction of surface currents, search and rescue crews can track the probable path of people lost at sea and expedite recovery time.

Surface current maps also support other scientific work including oil spill response, harmful algal bloom monitoring, and water quality assessments. Responders use IOOS data to track oil slicks after a spill because the real-time data shows the movement of the water and therefore the movement of the spill. Data on ocean currents helps forecasters predict both the movement and size of harmful algal blooms, so they can act to decrease health risks to people who might have been affected otherwise.Search Our Facts search

Salt in the Ocean: A Predictor of Rains for Crops?

Michael Hirtzer of Bloomberg wrote: There’s a new indicator that forecasters are using to predict how much rain inland farms like the US Corn Belt will get: Salt. Brinier water on the surface of the ocean can predict heavier rainfall that will fall far from the coasts, according to Boston-based Salient Predictions. The company, whose clients include seed and crop chemical giant BASF SE, is using the technique to forecast precipitation totals and help farmers at a time when drought is hurting food supplies. World food prices hit record highs earlier this year, partially as dryness and extreme heat damaged plants in important growing regions from the European Union to Brazil. “Evaporation from the ocean is the main source of all rainfall, and if some patch of ocean gets saltier than normal, it’s because more water has evaporated,” Ray Schmitt, an oceanographer and co-founder of Salient Predictions, said in an interview. “It’s bound to rain more somewhere else.” [Source: Michael Hirtzer, Bloomberg, September 8, 2022]

That means that if salt content in the Atlantic Ocean along the US East Coast is low, it could be a dry season in the top US corn-growing state of Iowa, and farmers there may decide to plant less or use a more drought-tolerant seed. For China’s Yangtze River Valley, a key farming region in the world’s most populous country, salinity levels in the South China Sea have been correlated with flooding and current drought conditions. Salient, which raised $5.4 million in a funding round earlier in 2022, said that it’s marketing a new suite of weather metrics including ocean salinity to larger agricultural businesses.

Image Sources: Wikimedia Commons; YouTube, NOAA

Text Sources: National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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