Oceanography, also known as oceanology and marine science, is the branch of Earth science
that studies the ocean. It covers a wide range of topics, including marine organisms and
ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics
and the geology of the sea floor; and fluxes of various chemical substances and physical
properties within the ocean and across its boundaries. These diverse topics reflect multiple
disciplines that oceanographers blend to further knowledge of the world ocean and understanding
of processes within: astronomy, biology, chemistry, climatology, geography, geology, hydrology,
meteorology and physics. Paleoceanography studies the history of the oceans in the geologic
past.
History
Early history Humans first acquired knowledge of the waves
and currents of the seas and oceans in pre-historic times. Observations on tides were recorded
by Aristotle and Strabo. Early exploration of the oceans was primarily for cartography
and mainly limited to its surfaces and of the animals that fishermen brought up in nets,
though depth soundings by lead line were taken. Although Juan Ponce de León in 1513 first
identified the Gulf Stream, and the current was well-known to mariners, Benjamin Franklin
made the first scientific study of it and gave it its name. Franklin measured water
temperatures during several Atlantic crossings and correctly explained the Gulf Stream's
cause. Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769-1770.
Information on the currents of the Pacific Ocean was gathered by explorers of the late
18th century, including James Cook and Louis Antoine de Bougainville. James Rennell wrote
the first scientific textbooks on oceanography, detailing the current flows of the Atlantic
and Indian oceans. During a voyage around the Cape of Good Hope in 1777, he mapped "the
banks and currents at the Lagullas". He was also the first to understand the nature of
the intermittent current near the Isles of Scilly,.
Sir James Clark Ross took the first modern sounding in deep sea in 1840, and Charles
Darwin published a paper on reefs and the formation of atolls as a result of the Second
voyage of HMS Beagle in 1831-6. Robert FitzRoy published a four-volume report of the Beagle's
three voyages. In 1841–1842 Edward Forbes undertook dredging in the Aegean Sea that
founded marine ecology. The first superintendent of the United States
Naval Observatory, Matthew Fontaine Maury devoted his time to the study of marine meteorology,
navigation, and charting prevailing winds and currents. His 1855 textbook Physical Geography
of the Sea was one of the first comprehensive oceanography studies. Many nations sent oceanographic
observations to Maury at the Naval Observatory, where he and his colleagues evaluated the
information and distributed the results worldwide. Modern oceanography
Despite all this, however, human knowledge of the oceans remained confined to the topmost
few fathoms of the water and a small amount of the bottom, mainly in shallow areas. Almost
nothing was known of the ocean depths. The Royal Navy's efforts to chart all of the world's
coastlines in the mid-19th century reinforced the vague idea that most of the ocean was
very deep, although little more was known. As exploration ignited both popular and scientific
interest in the polar regions and Africa, so too did the mysteries of the unexplored
oceans.
The seminal event in the founding of the modern science of oceanography was the 1872-76 Challenger
expedition. As the first true oceanographic cruise, this expedition laid the groundwork
for an entire academic and research discipline. In response to a recommendation from the Royal
Society, The British Government announced in 1871 an expedition to explore world's oceans
and conduct appropriate scientific investigation. Charles Wyville Thompson and Sir John Murray
launched the Challenger expedition. The Challenger, leased from the Royal Navy, was modified for
scientific work and equipped with separate laboratories for natural history and chemistry.
Under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical
miles surveying and exploring. On her journey circumnavigating the globe, 492 deep sea
soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature
observations were taken. Around 4,700 new species of marine life were discovered. The
result was the Report Of The Scientific Results of the Exploring Voyage of H.M.S. Challenger
during the years 1873-76. Murray, who supervised the publication, described the report as "the
greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth
and sixteenth centuries". He went on to found the academic discipline of oceanography at
the University of Edinburgh, which remained the centre for oceanographic research well
into the 20th century. Murray was the first to study marine trenches and in particular
the Mid-Atlantic Ridge, and map the sedimentary deposits in the oceans. He tried to map out
the world's ocean currents based on salinity and temperature observations, and was the
first to correctly understand the nature of coral reef development.
In the late 19th century, other Western nations also sent out scientific expeditions. The
first purpose built oceanographic ship, the Albatros, was built in 1882. In 1893, Fridtjof
Nansen allowed his ship, Fram, to be frozen in the Arctic ice. This enabled him to obtain
oceanographic, meteorological and astronomical data at a stationary spot over an extended
period.
Between 1907 and 1911 Otto Krümmel published the Handbuch der Ozeanographie, which became
influential in awakening public interest in oceanography. The four-month 1910 North Atlantic
expedition headed by John Murray and Johan Hjort was the most ambitious research oceanographic
and marine zoological project ever mounted until then, and led to the classic 1912 book
The Depths of the Ocean. The first acoustic measurement of sea depth
was made in 1914. Between 1925 and 1927 the "Meteor" expedition gathered 70,000 ocean
depth measurements using an echo sounder, surveying the Mid-Atlantic ridge.
Sverdrup and Fleming published The Ocean in 1942, which was a major landmark. The Sea
edited by M.N. Hill was published in 1962, while Rhodes Fairbridge's Encyclopedia of
Oceanography was published in 1966. The Great Global Rift, running along the Mid
Atlantic Ridge, was discovered by Maurice Ewing and Bruce Heezen in 1953; in 1954 a
mountain range under the Arctic Ocean was found by the Arctic Institute of the USSR.
The theory of seafloor spreading was developed in 1960 by Harry Hammond Hess. The Ocean Drilling
Project started in 1966. Deep sea vents were discovered in 1977 by John Corlis and Robert
Ballard in the submersible DSV Alvin. In the 1950s, Auguste Piccard invented the
bathyscaphe and used the Trieste to investigate the ocean's depths. The United States nuclear
submarine Nautilus made the first journey under the ice to the North Pole in 1958. In
1962 the FLIP, a 355 foot spar buoy, was first deployed.
From the 1970s, there has been much emphasis on the application of large scale computers
to oceanography to allow numerical predictions of ocean conditions and as a part of overall
environmental change prediction. An oceanographic buoy array was established in the Pacific
to allow prediction of El Niño events. 1990 saw the start of the World Ocean Circulation
Experiment which continued until 2002. Geosat seafloor mapping data became available in
1995. In recent years studies advanced particular
knowledge on ocean acidification, ocean heat content, ocean currents, the El Niño phenomenon,
mapping of methane hydrate deposits, the carbon cycle, coastal erosion, weathering and climate
feedbacks in regards to climate change interactions. Study of the oceans is linked to understanding
global climate changes, potential global warming and related biosphere concerns. The atmosphere
and ocean are linked because of evaporation and precipitation as well as thermal flux.
Wind stress is a major driver of ocean currents while the ocean is a sink for atmospheric
carbon dioxide. All these factors relate to the ocean's biogeochemical setup.
Ocean acidification
Ocean acidification describes the decrease in ocean pH that is caused by anthropogenic
carbon dioxide (CO 2) emissions into the atmosphere. Seawater
is slightly alkaline and had a preindustrial pH of about 8.2. More recently, anthropogenic
activities have steadily increased the carbon dioxide content of the atmosphere; about 30–40%
of the added CO2 is absorbed by the oceans, forming carbonic acid and lowering the pH
through ocean acidification. The pH is expected to reach 7.7 by the year 2100.
An important element for the skeletons of marine animals is calcium, but calcium carbonate
becomes more soluble with pressure, so carbonate shells and skeletons dissolve below the carbonate
compensation depth. Calcium carbonate becomes more soluble at lower pH, so ocean acidification
is likely to affect marine organisms with calcareous shells, such as oysters, clams,
sea urchins and corals, and the carbonate compensation depth will rise closer to the
sea surface. Affected planktonic organisms will include pteropods, coccolithophorids
and foraminifera, all important in the food chain. In tropical regions, corals are likely
to be severely affected as they become less able to build their calcium carbonate skeletons,
in turn adversely impacting other reef dwellers. The current rate of ocean chemistry change
seems to be unprecedented in Earth's geological history, making it unclear how well marine
ecosystems will adapt to the shifting conditions of the near future. Of particular concern
is the manner in which the combination of acidification with the expected additional
stressors of higher temperatures and lower oxygen levels will impact the seas.
Ocean currents
Since the early ocean expeditions in oceanography, a major interest was the study of the ocean
currents and temperature measurements. The tides, the Coriolis effect, changes in direction
and strength of wind, salinity and temperature are the main factors determining ocean currents.
The thermohaline circulation thermo- referring to temperature and -haline referring to salt
content connects 4 of 5 ocean basins and is primarily dependent on the density of sea
water. Ocean currents such as the Gulf Stream are wind-driven surface currents.
Ocean heat content
Oceanic heat content refers to the heat stored in the ocean. The changes in the ocean heat
play an important role in sea level rise, because of thermal expansion. Ocean warming
accounts for 90% of the energy accumulation from global warming between 1971 and 2010.
Branches
The study of oceanography is divided into branches:
Biological oceanography investigates the ecology of marine organisms in the context of the
physical, chemical, and geological characteristics of their ocean environment. It is closely
aligned with marine biology, though the latter has more emphasis on the biology of individual
marine organisms. Chemical oceanography, or marine chemistry,
is the study of the chemistry of the ocean and its chemical interaction with the atmosphere.
Geological oceanography, or marine geology, is the study of the geology of the ocean floor
including plate tectonics and paleoceanography. Physical oceanography, or marine physics,
studies the ocean's physical attributes including temperature-salinity structure, mixing, surface
waves, internal waves, surface tides, internal tides, and currents.
These branches reflect the fact that many oceanographers are first trained in the exact
sciences or mathematics and then focus on applying their interdisciplinary knowledge,
skills and abilities to oceanography. Data derived from the work of Oceanographers
is used in marine engineering, in the design and building of oil platforms, ships, harbours,
and other structures that allow us to use the ocean safely.
Oceanographic data management is the discipline ensuring that oceanographic data both past
and present are available to researchers. Oceanographic institutions
The first international organization of oceanography was created in 1902 as the International Council
for the Exploration of the Sea. In 1892 the Scripps Institution of Oceanography was founded,
followed by Woods Hole Oceanographic Institution in 1930, Virginia Institute of Marine Science
in 1938, and later the Lamont-Doherty Earth Observatory at Columbia University, and the
School of Oceanography at University of Washington. In Britain, the National Oceanography Centre,
Southampton is the successor to the Institute of Oceanography. In Australia, CSIRO Marine
and Atmospheric Research, is a leading center. In 1921 the International Hydrographic Bureau
was formed in Monaco. Related disciplines
See also
References
Hamblin, Jacob Darwin Oceanographers and the Cold War: Disciples of Marine Science. University
of Washington Press. ISBN 978-0-295-98482-7 Steele, J., K. Turekian and S. Thorpe.. Encyclopedia
of Ocean Sciences. San Diego: Academic Press. ISBN 0-12-227430-X
Sverdrup, Keith A., Duxbury, Alyn C., Duxbury, Alison B.. Fundamentals of Oceanography, McGraw-Hill,
ISBN 0-07-282678-9 Lang, Michael A., Ian G. Macintyre, and Klaus
Rützler, eds. Proceedings of the Smithsonian Marine Science Symposium. Smithsonian Contributions
to the Marine Sciences, no. 38. Washington, D.C.: Smithsonian Institution Scholarly Press
Boling Guo, Daiwen Huang. Infinite-Dimensional Dynamical Systems in Atmospheric and Oceanic
Science, 2014, World Scientific Publishing, ISBN 978-981-4590-37-2. Sample Chapter
External links NASA Jet Propulsion Laboratory - Physical
Oceanography Distributed Active Archive Center. A data center responsible for archiving and
distributing data about the physical state of the ocean.
Scripps Institution of Oceanography. One of the world's oldest, largest, and most important
centers for ocean and Earth science research, education, and public service.
Woods Hole Oceanographic Institution. One of the world's largest private, non-profit
ocean research, engineering and education organizations.
British Oceanographic Data Centre. A source of oceanographic data and information.
NOAA Ocean and Weather Data Navigator. Plot and download ocean data.
Freeview Video 'Voyage to the Bottom of the Deep Deep Sea' Oceanography Programme by the
Vega Science Trust and the BBC/Open University. Atlas of Spanish Oceanography by InvestigAdHoc.
Glossary of Physical Oceanography and Related Disciplines by Steven K. Baum, Department
of Oceanography, Texas A&M University