About Oceanography

The science of the sea; including physical oceanography (the study of the physical properties of sea water and its motion in waves, tides, and currents), marine chemistry, marine geology, and marine biology. The need to know more about the impact of marine pollution and possible effects of the exploitation of marine resources, together with the role of the ocean in possible global warming and climate change, means that oceanography is an important scientific discipline.

Improved understanding of the sea has been essential in such diverse fields as fisheries conservation, the exploitation of underwater oil and gas reserves, and coastal protection policy, as well as in national defense strategies. The scientific benefits include not only improved understanding of the oceans and their inhabitants, but important information about the evolution of the Earth and its tectonic processes, and about the global environment and climate, past and present, as well as possible future changes.
The modern discipline. The traditional basis of modern oceanography is the hydrographic station. Hydrographic studies are still carried out at regular intervals, with the research vessel in a specific position. Seawater temperature, depth, and salinity can be measured continuously by a probe towed behind the ship.

The revolution in electronics has provided not only a new generation of instruments for studying the sea but also new ways of collecting and analyzing the data they produce. Computers are employed in gathering and processing data in all fields, and are also used in the creation of mathematical models to aid in understanding. Much information can also be gained by remote sensing using satellites, which are also a valuable navigational aid. These provide data on sea surface temperature and currents, and on marine productivity. Satellite altimetry gives information on wave height and winds and even bottom topography (because this affects sea level). Scientists look forward to a day when observations can be made in the deep sea by autonomous vehicles. However, the ship remains a fundamental tool for many observations.

Physical oceanography. Physical oceanography, and in particular ocean circulation studies, forms the core of oceanographic research. The movements of seawater—ocean currents—are powerful agents in the distribution of heat throughout the world, influencing both weather and climate. The continual renewal of water bearing dissolved nutrients is essential to most marine organisms, which will be abundant only where such supplies are available.
Twentieth-century dynamical oceanographers have shown how the deflecting effect of the Earth's rotation influences water movements. Geostrophic forces are responsible for the intensification of surface currents, such as the Gulf Stream, on the western sides of oceans (western boundary currents).

In the 1950s the existence of a southward-flowing counter current under the Gulf Stream was predicted. Neutrally buoyant floats, to be tracked by radio signals picked up by hydrophones on board ship, were deployed to confirm this prediction. However, further out in the Atlantic the floats moved unexpectedly fast, with frequent changes in direction. This was the first indication of vigorous eddies in the ocean that have since been shown to be comparable to atmospheric weather systems. Further investigations of these phenomena, studies of equatorial currents and undercurrents, and transport between oceans are the principal topics occupying physical oceanographers in the latter part of the twentieth century. The World Ocean Circulation Experiment, a large-scale international program of cooperation on research projects and data-collecting expeditions, was designed to throw further light on the ocean's influence on world climate. Among the techniques being employed are the use of Swallow floats, arrays of current meters, that can be moored to the sea bed for a period of time to measure deep-water movements and then released for retrieval by acoustic signals, and the use of geochemical tracers, including chlorofluorocarbons, to obtain data on the distribution and age of water masses.

Marine biology. Biologists seek to classify the great diversity of life, from microscopic bacteria and phytoplankton to the great whales. To learn how the food web operates, they must examine the constraints on marine productivity and the distribution of species in the surface and mid water layers, and the vertical migrations between them, and in the bottom-living (benthic) fauna. Deep-sea cameras and submersibles now permit visual evidence of creatures in these remote depths to be obtained. Marine geology. Since the early 1900s, all recorded ocean depths have been incorporated in the General Bathymetric Chart of the Ocean. The amount of data available increased greatly with the introduction of continuous echo sounders; subsequently, side-scan sonar permitted very detailed topographical surveys to be made of the ocean floor. The features thus revealed, in particular the mid ocean ridges (spreading centers) and deep trenches (subduction zones), are integral to the theory of plate tectonics. An important discovery made toward the end of the twentieth century was the existence of hydrothermal vents, where hot mineral-rich water gushes from the Earth's interior. The deposition of minerals at these sites and the discovery of associated ecosystems make them of potential economic as well as great scientific interest. Possibly life on Earth began in similar situations in the remote past. Investigation of such areas can be made directly by scientists using submersibles and by underwater cameras, as well as by instrumentation. Even the sediments and other rocks of the sea floor are being sampled by the international deep-sea drilling program to provide information on how the present oceans evolved and on past climate change.
Reference : McGraw - Hill Encyclopedia of Science and Technology


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