Oceanography

Oceanography (compound of the Greek words ὠκεανός meaning "ocean" and γράφω meaning "write"), also known as oceanology, is the study of the physical and biological aspects of the ocean. It is an important Earth science, which covers a wide range of topics, including 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

Gulf stream map
Map of the Gulf Stream by Benjamin Franklin, 1769–1770. Courtesy of the NOAA Photo Library.

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.[1][2]

Rennel map 1799
1799 map of the currents in the Atlantic and Indian Oceans, by James Rennell

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, (now known as Rennell's Current).[3]

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 1831–1836. Robert FitzRoy published a four-volume report of 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 (1842–1861), 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.[4]

Modern oceanography

Despite all this, 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 British 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.

Challenger
HMS Challenger undertook the first global marine research expedition in 1872.

The seminal event in the founding of the modern science of oceanography was the 1872–1876 Challenger expedition. As the first true oceanographic cruise, this expedition laid the groundwork for an entire academic and research discipline.[5] 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. Challenger, leased from the Royal Navy, was modified for scientific work and equipped with separate laboratories for natural history and chemistry.[6] Under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical miles (130,000 km) surveying and exploring. On her journey circumnavigating the globe,[6] 492 deep sea soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature observations were taken.[7] 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.[8] 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 (as did private individuals and institutions). The first purpose built oceanographic ship, 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.

In 1881 the geographer John Francon Williams published a seminal book, Geography of the Oceans.[9][10] Between 1907 and 1911 Otto Krümmel published the Handbuch der Ozeanographie, which became influential in awakening public interest in oceanography.[11] 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, Johnson and Fleming published The Oceans in 1942,[12] which was a major landmark. The Sea (in three volumes, covering physical oceanography, seawater and geology) 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 Program started in 1966. Deep-sea vents were discovered in 1977 by Jack Corliss and Robert Ballard in the submersible DSV Alvin.

In the 1950s, Auguste Piccard invented the bathyscaphe and used the bathyscaphe 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 (Floating Instrument Platform), a 355-foot (108 m) 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 (WOCE) 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 (and solar insolation). 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.

Further understanding of the worlds oceans permit scientists to better decide weather changes which in addition guides to a more reliable utilization of earths resources. [13]

Branches

Antarctic frontal-system hg
Oceanographic frontal systems on the Southern Hemisphere

The study of oceanography is divided into these four branches:

Biological oceanography

Biological oceanography investigates the ecology of marine organisms in the context of the physical, chemical and geological characteristics of their ocean environment and the biology of individual marine organisms.

Chemical oceanography

Chemical oceanography is the study of the chemistry of the ocean. Whereas chemical oceanography is primarily occupied with the study and understanding of seawater properties and its changes, ocean chemistry focuses primarily on the geochemical cycles. The following is a central topic investigated by chemical oceanography.

Ocean acidification

Ocean acidification describes the decrease in ocean pH that is caused by anthropogenic carbon dioxide (CO
2
) emissions into the atmosphere.[14] 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 (now below 8.1[15]) through ocean acidification.[16][17][18] The pH is expected to reach 7.7 by the year 2100.[19]

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.[20] 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,[21][22] 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,[23] in turn adversely impacting other reef dwellers.[19]

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.[24] 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.[25]

Geological oceanography

Geological oceanography is the study of the geology of the ocean floor including plate tectonics and paleoceanography.

Physical oceanography

Physical oceanography studies the ocean's physical attributes including temperature-salinity structure, mixing, surface waves, internal waves, surface tides, internal tides, and currents. The following are central topics investigated by physical oceanography.

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 (THC) (thermo- referring to temperature and -haline referring to salt content) connects the ocean basins and is primarily dependent on the density of sea water. It is becoming more common to refer to this system as the 'meridional overturning circulation' because it more accurately accounts for other driving factors beyond temperature and salinity.

Ocean heat content

Oceanic heat content (OHC) 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.[26]

Paleoceanography

Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the reconstruction of past climate at various intervals. Paleoceanographic research is also intimately tied to palaeoclimatology.

Oceanographic institutions

The first international organization of oceanography was created in 1902 as the International Council for the Exploration of the Sea. In 1903 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 (an institute of the Natural Environment Research Council) is the successor to the UK's Institute of Oceanographic Sciences. In Australia, CSIRO Marine and Atmospheric Research (CMAR), is a leading centre. In 1921 the International Hydrographic Bureau (IHB) was formed in Monaco.

Related disciplines

See also

References

  1. ^ 1785: Benjamin Franklin's 'Sundry Maritime Observations' Archived 2005-12-18 at the Wayback Machine
  2. ^ Wilkinson, Jerry. History of the Gulf Stream 1 January 2008
  3. ^ Lee, Sidney, ed. (1896). "Rennell, James" . Dictionary of National Biography. 48. London: Smith, Elder & Co.
  4. ^ Williams, Frances L. Matthew Fontaine Maury, Scientist of the Sea. (1969) ISBN 0-8135-0433-3
  5. ^ Then and Now: The HMS Challenger Expedition and the 'Mountains in the Sea' Expedition, Ocean Explorer website (NOAA), accessed 2 January 2012
  6. ^ a b Rice, A. L. (1999). "The Challenger Expedition". Understanding the Oceans: Marine Science in the Wake of HMS Challenger. Routledge. pp. 27–48. ISBN 978-1-85728-705-9.
  7. ^ Oceanography: an introduction to the marine environment (Peter K. Weyl, 1970), p. 49
  8. ^ "Sir John Murray (1841–1914) – Founder Of Modern Oceanography". Science and Engineering at The University of Edinburgh. Archived from the original on 28 May 2013. Retrieved 7 November 2013.
  9. ^ Williams, J. Francon (1881) The Geography of the Oceans: Physical, Historical, and Descriptive George Philip & Son.
  10. ^ Geography of the Oceans by John Francon Williams, 1881, OCLC 561275070
  11. ^ Otto Krümmel (1907). "Handbuch der Ozeanographie". J. Engelhorn.
  12. ^ Sverdrup, Harald Ulrik; Johnson, Martin Wiggo; Fleming, Richard H. (1942). The Oceans, Their Physics, Chemistry, and General Biology. New York: Prentice-Hall.
  13. ^ "Oceanography | science". Encyclopedia Britannica. Retrieved 2019-04-13.
  14. ^ Caldeira, K.; Wickett, M. E. (2003). "Anthropogenic carbon and ocean pH" (PDF). Nature. 425 (6956): OS11C-0385. Bibcode:2001AGUFMOS11C0385C. doi:10.1038/425365a. PMID 14508477.
  15. ^ "Ocean Acidity". EPA. 13 September 2013. Retrieved 1 November 2013.
  16. ^ Feely, R. A.; et al. (July 2004). "Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans". Science. 305 (5682): 362–366. Bibcode:2004Sci...305..362F. doi:10.1126/science.1097329. PMID 15256664.
  17. ^ Zeebe, R. E.; Zachos, J. C.; Caldeira, K.; Tyrrell, T. (4 July 2008). "OCEANS: Carbon Emissions and Acidification". Science. 321 (5885): 51–52. doi:10.1126/science.1159124. PMID 18599765.
  18. ^ Gattuso, J.-P.; Hansson, L. (15 September 2011). Ocean Acidification. Oxford University Press. ISBN 978-0-19-959109-1. OCLC 730413873.
  19. ^ a b "Ocean acidification". Department of Sustainability, Environment, Water, Population & Communities: Australian Antarctic Division. 28 September 2007. Retrieved 17 April 2013.
  20. ^ Pinet, Paul R. (1996). Invitation to Oceanography. West Publishing Company. pp. 126, 134–135. ISBN 978-0-314-06339-7.
  21. ^ "What is Ocean Acidification?". NOAA PMEL Carbon Program. Retrieved 15 September 2013.
  22. ^ Orr, James C.; et al. (2005). "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms" (PDF). Nature. 437 (7059): 681–686. Bibcode:2005Natur.437..681O. doi:10.1038/nature04095. PMID 16193043. Archived from the original (PDF) on 25 June 2008.
  23. ^ Cohen, A.; Holcomb, M. (2009). "Why Corals Care About Ocean Acidification: Uncovering the Mechanism" (PDF). Oceanography. 24 (4): 118–127. doi:10.5670/oceanog.2009.102. Archived from the original (PDF) on 2013-11-06.
  24. ^ Hönisch, Bärbel; Ridgwell, Andy; Schmidt, Daniela N.; Thomas, E.; et al. (2012). "The Geological Record of Ocean Acidification". Science. 335 (6072): 1058–1063. Bibcode:2012Sci...335.1058H. doi:10.1126/science.1208277. hdl:1983/24fe327a-c509-4b6a-aa9a-a22616c42d49. PMID 22383840.
  25. ^ Gruber, N. (18 April 2011). "Warming up, turning sour, losing breath: ocean biogeochemistry under global change". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 369 (1943): 1980–96. Bibcode:2011RSPTA.369.1980G. doi:10.1098/rsta.2011.0003. PMID 21502171.
  26. ^ IPCC (2013). Climate Change 2013: The Physical Science Basis (PDF) (Report). Cambridge University Press. p. 8.

External links

Acoustical oceanography

Acoustical oceanography is the use of underwater sound to study the sea, its boundaries and its contents.

Arctic Ocean

The Arctic Ocean is the smallest and shallowest of the world's five major oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Sea. It is classified as an estuary of the Atlantic Ocean, and it is also seen as the northernmost part of the all-encompassing World Ocean.

Located mostly in the Arctic north polar region in the middle of the Northern Hemisphere, besides its surrounding waters the Arctic Ocean is surrounded by Eurasia and North America. It is partly covered by sea ice throughout the year and almost completely in winter. The Arctic Ocean's surface temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major oceans, due to low evaporation, heavy fresh water inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the ice has been quoted at 50%. The US National Snow and Ice Data Center (NSIDC) uses satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years.

Fetch (geography)

The fetch, also called the fetch length, is the length of water over which a given wind has blown. Fetch is used in geography and meteorology and its effects are usually associated with sea state and when it reaches shore it is the main factor that creates storm surge which leads to coastal erosion and flooding. It also plays a large part in longshore drift as well.

Fetch length, along with the wind speed (wind strength), determines the size (sea state) of waves produced. The wind direction is considered constant. The longer the fetch and the faster the wind speed, the more wind energy is imparted to the water surface and the larger the resulting sea state will be.

Littoral zone

The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal environments, the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. The littoral zone always includes this intertidal zone, and the terms are often used interchangeably. However, the meaning of littoral zone can extend well beyond the intertidal zone.

The term has no single definition. What is regarded as the full extent of the littoral zone, and the way the littoral zone is divided into subregions, varies in different contexts. (Lakes and rivers have their own definitions.) The use of the term also varies from one part of the world to another, and between different disciplines. For example, military commanders speak of the littoral in ways that are quite different from marine biologists.

The adjacency of water gives a number of distinctive characteristics to littoral regions. The erosive power of water results in particular types of landforms, such as sand dunes, and estuaries. The natural movement of the littoral along the coast is called the littoral drift. Biologically, the ready availability of water enables a greater variety of plant and animal life, and particularly the formation of extensive wetlands. In addition, the additional local humidity due to evaporation usually creates a microclimate supporting unique types of organisms.

The word littoral may be used both as a noun and as an adjective. It derives from the Latin noun litus, litoris, meaning "shore". (The doubled tt is a late-medieval innovation, and the word is sometimes seen in the more classical-looking spelling litoral.)

Marine geology

Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.

Marine geological studies were of extreme importance in providing the critical evidence for sea floor spreading and plate tectonics in the years following World War II. The deep ocean floor is the last essentially unexplored frontier and detailed mapping in support of both military (submarine) objectives and economic (petroleum and metal mining) objectives drives the research.

Mooring (oceanography)

A mooring in oceanography is a collection of devices connected to a wire and anchored on the sea floor. It is the Eulerian way of measuring ocean currents, since a mooring is stationary at a fixed location. In contrast to that, the Lagrangian way measures the motion of an oceanographic drifter, the Lagrangian drifter.

National Institute of Oceanography, India

The National Institute of Oceanography, founded on 1 January 1966 as one of 37 constituent laboratories of the CSIR, is an autonomous research organization in India to undertake scientific research and studies of special oceanographic features of the Northern Indian Ocean. Headquartered in Goa, it has regional centres in Kochi, Mumbai and Vizag.

NIO (oceanography) as well as ASI (archaeology), BSI (botany), FSI (forests), FiSI (fisheries), GSI (geology), IIEE (ecology), RGCCI (Census of India), SI (cartography) and ZSI (zoology) are key national survey organisations of India.

Naval Meteorology and Oceanography Command

The Naval Meteorology and Oceanography Command (COMNAVMETOCCOM) or CNMOC, serves as the operational arm of the Naval Oceanography Program. Headquartered at the Stennis Space Center in Mississippi, CNMOC is an echelon three command reporting to United States Fleet Forces Command (USFLTFORCOM). CNMOC's claimancy is globally distributed, with assets located on larger ships (aircraft carriers, amphibious ships, and command and control ships), shore facilities at fleet concentration areas, and larger production centers in the U.S.

CNMOC is focused on providing critical environmental knowledge to the warfighting disciplines of Anti-Submarine Warfare; Naval Special Warfare; Mine Warfare; Intelligence, Surveillance and Reconnaissance; and Fleet Operations (Strike and Expeditionary), as well as to the support areas of Maritime Operations, Aviation Operations, Navigation, Precise Time, and Astrometry.

The Oceanographer of the Navy works closely with the staff of CNMOC to ensure the proper resources are available to meet its mission, to act as a liaison between CNMOC and the Chief of Naval Operations, and to represent the Naval Oceanography Program in interagency and international forums.

Neritic zone

The neritic zone is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately 200 meters (660 ft) in depth.

From the point of view of marine biology it forms a relatively stable and well-illuminated environment for marine life, from plankton up to large fish and corals, while physical oceanography sees it as where the oceanic system interacts with the coast.

Ocean

An ocean (from Ancient Greek Ὠκεανός, transc. Okeanós) is a body of water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word "ocean" is often used interchangeably with "sea" in American English. Strictly speaking, a sea is a body of water (generally a division of the world ocean) partly or fully enclosed by land, though "the sea" refers also to the oceans.

Saline water covers approximately 361,000,000 km2 (139,000,000 sq mi) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface and 90% of the Earth's biosphere. The ocean contains 97% of Earth's water, and oceanographers have stated that less than 5% of the World Ocean has been explored. The total volume is approximately 1.35 billion cubic kilometers (320 million cu mi) with an average depth of nearly 3,700 meters (12,100 ft).As the world ocean is the principal component of Earth's hydrosphere, it is integral to life, forms part of the carbon cycle, and influences climate and weather patterns. The World Ocean is the habitat of 230,000 known species, but because much of it is unexplored, the number of species that exist in the ocean is much larger, possibly over two million. The origin of Earth's oceans is unknown; oceans are thought to have formed in the Hadean eon and may have been the impetus for the emergence of life.

Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of the moon Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.

Ocean gyre

In oceanography, a gyre () is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity along with horizontal and vertical friction, determine the circulation patterns from the wind stress curl (torque).The term gyre can be used to refer to any type of vortex in the air or the sea, even one that is man-made, but it is most commonly used in oceanography to refer to the major ocean systems.

Physical oceanography

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Physical oceanography is one of several sub-domains into which oceanography is divided. Others include biological, chemical and geological oceanography.

Physical oceanography may be subdivided into descriptive and dynamical physical oceanography.Descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precisely as possible.

Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and numerical models. These are part of the large field of Geophysical Fluid Dynamics (GFD) that is shared together with meteorology. GFD is a sub field of Fluid dynamics describing flows occurring on spatial and temporal scales that are greatly influenced by the Coriolis force.

RISE project

The RISE Project (Rivera Submersible Experiments) was a 1979 international marine research project which mapped and investigated seafloor spreading in the Pacific Ocean, at the crest of the East Pacific Rise (EPR) at 21° north latitude. Using a deep sea submersible (ALVIN) to search for hydrothermal activity at depths around 2600 meters, the project discovered a series of vents emitting dark mineral particles at extremely high temperatures which gave rise to the popular name, “black smokers”. Biologic communities found at 21° N vents, based on chemosynthesis and similar to those found at the Galapagos spreading center, established that these communities are not unique. Discovery of a deep-sea ecosystem not based on sunlight spurred theories of the origin of life on Earth.

Salinity

Salinity (/səˈlɪnəti/) is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). This is usually measured in (note that this is technically dimensionless). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water.

A contour line of constant salinity is called an isohaline, or sometimes isohale.

Scripps Institution of Oceanography

The Scripps Institution of Oceanography (sometimes referred to as SIO, Scripps Oceanography, or Scripps) in La Jolla, California, founded in 1903, is one of the oldest and largest centers for ocean and Earth science research, public service, undergraduate and graduate training in the world. Hundreds of ocean and Earth scientists conduct research with the aid of oceanographic research vessels and shorebased laboratories. Its Old Scripps Building is a U.S. National Historic Landmark. SIO is a division of the University of California San Diego (UCSD). The public explorations center of the institution is the Birch Aquarium at Scripps. Since becoming part of the University of California in 1912, the institution has expanded its scope to include studies of the physics, chemistry, geology, biology, and climate of Earth.

Dr. Margaret Leinen took office as Vice Chancellor for Marine Sciences, Director of Scripps Institution of Oceanography, and Dean of the Graduate School of Marine Sciences on October 1, 2013.Scripps publishes explorations now, an e-magazine of ocean and earth science.

Seawater

Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 599 mM). This means that every kilogram (roughly one litre by volume) of seawater has approximately 35 grams (1.2 oz) of dissolved salts (predominantly sodium (Na+) and chloride (Cl−) ions). Average density at the surface is 1.025 kg/L. Seawater is denser than both fresh water and pure water (density 1.0 kg/L at 4 °C (39 °F)) because the dissolved salts increase the mass by a larger proportion than the volume. The freezing point of seawater decreases as salt concentration increases. At typical salinity, it freezes at about −2 °C (28 °F). The coldest seawater ever recorded (in a liquid state) was in 2010, in a stream under an Antarctic glacier, and measured −2.6 °C (27.3 °F). Seawater pH is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units.

Thermocline

A thermocline (also known as the thermal layer or the metalimnion in lakes) is a thin but distinct layer in a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) in which temperature changes more rapidly with depth than it does in the layers above or below. In the ocean, the thermocline divides the upper mixed layer from the calm deep water below.

Depending largely on season, latitude, and turbulent mixing by wind, thermoclines may be a semi-permanent feature of the body of water in which they occur, or they may form temporarily in response to phenomena such as the radiative heating/cooling of surface water during the day/night. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude, and local environmental conditions, such as tides and currents.

Undertow (water waves)

In physical oceanography, undertow is the under-current that is moving offshore when waves are approaching the shore. Undertow is a natural and universal feature for almost any large body of water: it is a return flow compensating for the onshore-directed average transport of water by the waves in the zone above the wave troughs. The undertow's flow velocities are generally strongest in the surf zone, where the water is shallow and the waves are high due to shoaling.In popular usage, the word "undertow" is often misapplied to rip currents. An undertow occurs everywhere underneath shore-approaching waves, whereas rip currents are localized narrow offshore currents occurring at certain locations along the coast. Unlike undertow, rip currents are strong at the surface.

Zooplankton

Zooplankton (, ) are heterotrophic (sometimes detritivorous) plankton (cf. phytoplankton). Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word zooplankton is derived from the Greek zoon (ζῴον), meaning "animal", and planktos (πλαγκτός), meaning "wanderer" or "drifter". Individual zooplankton are usually microscopic, but some (such as jellyfish) are larger and visible to the naked eye.

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