# Ocean dynamics

Ocean dynamics define and describe the motion of water within the oceans. Ocean temperature and motion fields can be separated into three distinct layers: mixed (surface) layer, upper ocean (above the thermocline), and deep ocean.

Ocean dynamics has traditionally been investigated by sampling from instruments in situ.[1]

The mixed layer is nearest to the surface and can vary in thickness from 10 to 500 meters. This layer has properties such as temperature, salinity and dissolved oxygen which are uniform with depth reflecting a history of active turbulence (the atmosphere has an analogous planetary boundary layer). Turbulence is high in the mixed layer. However, it becomes zero at the base of the mixed layer. Turbulence again increases below the base of the mixed layer due to shear instabilities. At extratropical latitudes this layer is deepest in late winter as a result of surface cooling and winter storms and quite shallow in summer. Its dynamics is governed by turbulent mixing as well as Ekman pumping, exchanges with the overlying atmosphere, and horizontal advection.[2]

The upper ocean, characterized by warm temperatures and active motion, varies in depth from 100 m or less in the tropics and eastern oceans to in excess of 800 meters in the western subtropical oceans. This layer exchanges properties such as heat and freshwater with the atmosphere on timescales of a few years. Below the mixed layer the upper ocean is generally governed by the hydrostatic and geostrophic relationships.[2] Exceptions include the deep tropics and coastal regions.

The deep ocean is both cold and dark with generally weak velocities (although limited areas of the deep ocean are known to have significant recirculations). The deep ocean is supplied with water from the upper ocean in only a few limited geographical regions: the subpolar North Atlantic and several sinking regions around the Antarctic. Because of the weak supply of water to the deep ocean the average residence time of water in the deep ocean is measured in hundreds of years. In this layer as well the hydrostatic and geostrophic relationships are generally valid and mixing is generally quite weak.

## Primitive equations

Ocean dynamics are governed by Newton's equations of motion expressed as the Navier-Stokes equations for a fluid element located at (x,y,z) on the surface of our rotating planet and moving at velocity (u,v,w) relative to that surface:

• the zonal momentum equation:
${\displaystyle {\frac {Du}{Dt}}=-{\frac {1}{\rho }}{\frac {\partial p}{\partial x}}+fv+{\frac {1}{\rho }}{\frac {\partial \tau _{x}}{\partial z}}}$
• the meridional momentum equation:
${\displaystyle {\frac {Dv}{Dt}}=-{\frac {1}{\rho }}{\frac {\partial p}{\partial y}}-fu+{\frac {1}{\rho }}{\frac {\partial \tau _{y}}{\partial z}}}$
${\displaystyle {\frac {\partial p}{\partial z}}=-\rho g}$
${\displaystyle {\frac {\partial u}{\partial x}}+{\frac {\partial v}{\partial y}}+{\frac {\partial w}{\partial z}}=0}$
${\displaystyle {\frac {\partial T}{\partial t}}+u{\frac {\partial T}{\partial x}}+v{\frac {\partial T}{\partial y}}+w{\frac {\partial T}{\partial z}}=Q}$.[2]
${\displaystyle {\frac {\partial S}{\partial t}}+u{\frac {\partial S}{\partial x}}+v{\frac {\partial S}{\partial y}}+w{\frac {\partial S}{\partial z}}=(E-P)S(z=0)}$.[2]

Here "u" is zonal velocity, "v" is meridional velocity, "w" is vertical velocity, "p" is pressure, "ρ" is density, "T" is temperature, "S" is salinity, "g" is acceleration due to gravity, "τ" is wind stress, and "f" is the Coriolis parameter. "Q" is the heat input to the ocean, while "P-E" is the freshwater input to the ocean.

## Mixed layer dynamics

Mixed layer dynamics are quite complicated; however, in some regions some simplifications are possible. The wind-driven horizontal transport in the mixed layer is approximately described by Ekman Layer dynamics in which vertical diffusion of momentum balances the Coriolis effect and wind stress.[3] This Ekman transport is superimposed on geostrophic flow associated with horizontal gradients of density.

## Upper ocean dynamics

Horizontal convergences and divergences within the mixed layer due, for example, to Ekman transport convergence imposes a requirement that ocean below the mixed layer must move fluid particles vertically. But one of the implications of the geostrophic relationship is that the magnitude of horizontal motion must greatly exceed the magnitude of vertical motion. Thus the weak vertical velocities associated with Ekman transport convergence (measured in meters per day) cause horizontal motion with speeds of 10 centimeters per second or more. The mathematical relationship between vertical and horizontal velocities can be derived by expressing the idea of conservation of angular momentum for a fluid on a rotating sphere. This relationship (with a couple of additional approximations) is known to oceanographers as the Sverdrup relation.[3] Among its implications is the result that the horizontal convergence of Ekman transport observed to occur in the subtropical North Atlantic and Pacific forces southward flow throughout the interior of these two oceans. Western boundary currents (the Gulf Stream and Kuroshio) exist in order to return water to higher latitude.

## References

1. ^ "Frontiers of Remote Sensing of the Oceans and Troposphere from Air and Space Platforms". Remote Sensing of Oceanography: Past, Present, and Future. NASA Technical Reports Server. Retrieved 22 September 2011.
2. ^ a b c d DeCaria, Alex J., 2007: "Lesson 5 - Oceanic Boundary Layer." Personal Communication, Millersville University of Pennsylvania, Millersville, Pa. (Not a WP:RS)
3. ^ a b Pickard, G.L. and W.J. Emery, 1990: Descriptive Physical Oceanography, Fifth Edition. Butterworth-Heinemann, 320 pp.

Adrian Edmund Gill FRS (22 February 1937 – 19 April 1986) was an Australian meteorologist and oceanographer best known for his textbook Atmosphere-Ocean Dynamics [1]. Gill was born in Melbourne Australia and worked at Cambridge, serving as Senior Research Fellow from 1963 to 1984 [2]. His father was Edmund Gill, geologist, palaeontologist and curator at the National Museum of Victoria.

Gill was chair of the Tropical Ocean-Global Atmosphere programme. He was elected a Fellow of the Royal Society of London in 1986. His candidacy citation read: "Dr A.E. Gill is internationally recognised for his work in geophysical fluid dynamics and leads a small but highly productive team working on problems in dynamical oceanography and meteorology. He has made outstanding theoretical contributions to a wide range of topics, including the stability of pipe flow, thermal convection, circulation of the Southern Ocean, seasonal variability of the ocean, waves in rotating fluids, wind-induced upwelling, coastal currents and sea-level changes and coastally-trapped waves in the atmosphere, and he is particularly effective in the way he is able to interpret observations and guide the activities of observational workers".

Coastal ocean dynamics applications radar (CODAR) describes a type of portable, land-based, High Frequency (HF) radar developed between 1973 and 1983 at NOAA's Wave Propagation Laboratory in Boulder, Colorado. CODAR is a noninvasive system that permits to measure and map near-surface ocean currents in coastal waters. It is transportable and offers output ocean current maps on site in near real time. Moreover, using CODAR it is possible to measure waves heights and it provides an indirect estimate of local wind direction.

Cooperative Institute for Limnology and Ecosystems Research

The Cooperative Institute for Limnology and Ecosystems Research (CILER) fosters research collaborations between the National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research (OAR) Great Lakes Environmental Research Laboratory (GLERL), Michigan State University (MSU), and the University of Michigan (UM). It is one of 16 NOAA Cooperative Institutes (CIs).The CILER research themes are:

Climate and Large Lake Dynamics

Coastal and Nearshore Processes

Large Lake Ecosystem Structure and Function

Remote Sensing of Large Lake and Coastal Ocean Dynamics

Marine Environmental Engineering

Dol Ammad is a heavy metal band formed in 2000 by Greek keyboard player Thanasis Lightbridge. Dol Ammad is characterizeded with instrumentation which layers conventional metal instrumentation (bass, drums, and electric guitar), synthesizers, and the vocal support of a fourteen-member four-part choir. Lightbridge describes his music as "electronica art metal" and cites electronic music pioneers Jean Michel Jarre and Vangelis as key influences. The band derives its name from a fuel refinery in the computer game Descent 3.

Geophysical fluid dynamics

Geophysical fluid dynamics, in its broadest meaning, refers to the fluid dynamics of naturally occurring flows, such as lava flows, oceans, and planetary atmospheres, on Earth and other planets.Two physical features that are common to many of the phenomena studied in geophysical fluid dynamics are rotation of the fluid due to the planetary rotation and stratification (layering). The applications of geophysical fluid dynamics do not generally include the circulation of the mantle, which is the subject of geodynamics, or fluid phenomena in the magnetosphere.

Gulf of Lion

The Gulf of Lion (French: golfe du Lion, Spanish: golfo de León, Italian: Golfo del Leone, Occitan: golf del/dau Leon, Catalan: golf del Lleó, Medieval Latin: sinus Leonis, mare Leonis, Classical Latin: sinus Gallicus) is a wide embayment of the Mediterranean coastline of Languedoc-Roussillon and Provence in France, reaching from the border with Catalonia in the west to Toulon.

The chief port on the gulf is Marseille. Toulon is another important port. The fishing industry in the gulf is based on hake (Merluccius merluccius), being bottom-trawled, long-lined and gill-netted and currently declining from over-fishing.

Rivers that empty into the gulf include the Tech, Têt, Aude, Orb, Hérault, Vidourle, and the Rhône.

The continental shelf is exposed here as a wide coastal plain, and the offshore terrain slopes rapidly to the Mediterranean's abyssal plain. Much of the coastline is composed of lagoons and salt marsh.

This is the area of the cold, blustery winds called the Mistral and the Tramontane.

Janet Sprintall

Janet Sprintall is an Australian-born oceanographer at Scripps Institution of Oceanography. She specializes in inter-basin exchanges, and in particular in the Indonesian throughflow and dynamics of the Antarctic Circumpolar Current through the Drake passage. Sprintall studied barrier layers for her doctoral research, and as of 2016 is building on that work as a principle investigator with the NASA SPURS II project in the tropical Pacific. As an expert in Pacific Ocean dynamics, she has been highly cited. Sprintall provided plot advice for the TV series Lost.

Kelvin wave

A Kelvin wave is a wave in the ocean or atmosphere that balances the Earth's Coriolis force against a topographic boundary such as a coastline, or a waveguide such as the equator. A feature of a Kelvin wave is that it is non-dispersive, i.e., the phase speed of the wave crests is equal to the group speed of the wave energy for all frequencies. This means that it retains its shape as it moves in the alongshore direction over time.

A Kelvin wave (fluid dynamics) is also a long scale perturbation mode of a vortex in superfluid dynamics; in terms of the meteorological or oceanographical derivation, one may assume that the meridional velocity component vanishes (i.e. there is no flow in the north–south direction, thus making the momentum and continuity equations much simpler). This wave is named after the discoverer, Lord Kelvin (1879).

Leanne Armand

Dr Leanne Armand (born February 1968) is a marine scientist and an expert in the identification of diatoms in the Southern Ocean. She is known for her contributions to the understanding of past Southern Ocean dynamics and sea ice as a result of her knowledge of diatom distributions and ecology.

Her research focuses on the distribution of diatoms, a single-cell microscopic phytoplankton, within the Southern Ocean. Different species of diatoms inhabit different regions of the ocean, depending on the physical characteristics (e.g. temperature, salinity and nutrients) of the water mass. Understanding diatom distributions and how their skeletons are preserved in the fossil record contained within sediment cores taken from the ocean floor can provide information about past climate regimes, including ocean temperatures and sea ice extent. Armand has also recently studied diatoms in the Southern Ocean near Kerguelen and Heard Islands to examine their role in the transport of carbon to the ocean floor after their annual spring bloom.

Margot Gerritsen

Margot Geertrui Gerritsen is a professor of Energy Resources Engineering at Stanford University and a senior associate dean for educational initiatives in the Stanford University School of Earth, Energy & Environmental Sciences. Her research interests include energy production, ocean dynamics, and sailboat design.Gerritsen was born in the Netherlands. She earned a master's degree at Delft University of Technology. She completed her doctorate in 1996 in scientific computing and computational mathematics at Stanford, under the supervision of Joseph Oliger. Gerritsen then worked at the University of Auckland before rejoining Stanford as a faculty member in 2001.She was named a SIAM Fellow in 2018.

Mississippi Sound

The Mississippi Sound is a sound along the Gulf Coast of the United States. It runs east-west along the southern coasts of Mississippi and Alabama, from Waveland, Mississippi, to the Dauphin Island Bridge, a distance of about 145 kilometers (90 mi). The sound is bordered on its southern edge by the barrier islands - Cat, Ship, Horn, West Petit Bois (formerly known as Sand Island), Petit Bois, and Dauphin. Ship, Horn, West Petit Bois and Petit Bois Islands are part of the National Park Service's Gulf Islands National Seashore. Those islands separate the sound from the Gulf of Mexico. The sediment of the islands was created partly by the ancient Mississippi River when the St. Bernard Lobe of the Mississippi Delta was active over two thousand years ago. The expansion of the St. Bernard subdelta slowly isolated the Mississippi Sound from ocean dynamics of the open Gulf of Mexico.Traditional seafood harvests, particularly shellfish, have been curtailed recently due to declines in numbers and quality caused by pollution and weather related events such as hurricanes, flooding, or droughts. Federal and state authorities have various programs and regulations aimed at shellfish restoration and water quality monitoring for beachgoers. After the 2008 and 2011 openings of the floodgates of the Bonnet Carré Spillway the massive freshwater destroyed the oyster and crab populations and the authorities have undertaken cultch plantings to restore the fisheries in the western sound. Sport fishing is year-round on charters as well as the nearshore.Large portions of the Mississippi Sound reach depths of about 6 meters (20 ft). Part of the Gulf Intracoastal Waterway traverses the sound with a project depth of 3.6 meters (12 ft). The waterway, maintained by the US Army Corps of Engineers, is designed for towboat and barge traffic. Most of its route through the sound is merely an imaginary line through water whose depth exceeds the project depth. A section west of Cat Island and the portion north of Dauphin Island rely on dredged channels marked by aids to navigation maintained by the US Coast Guard.

Deepwater ports along the sound include Gulfport and Pascagoula. Dredged ship channels running basically north-south connect those ports to the Gulf of Mexico, running between pairs of the barrier islands. The Bay of St. Louis and Biloxi Bay on the northern side of the sound jut into mainland Mississippi. These bays drain the Wolf and Jourdan Rivers as well as Bernard, Davis, and Turkey bayous

The Pascagoula River and the Pearl River flow into the sound.

Ocean Observatories Initiative

The Ocean Observatories Initiative (OOI) is a National Science Foundation (NSF) Division of Ocean Sciences program that focuses the science, technology, education and outreach of an emerging network of science driven ocean observing systems. It is a networked infrastructure of science-driven sensor systems to measure the physical, chemical, geological and biological variables in the ocean and seafloor as well as the overlying atmosphere, providing an integrated system collecting data on coastal, regional and global scales.

OOI is funded by the National Science Foundation (NSF).

OOI's goal is to deliver data and data products for a 25-year-plus time period within a scalable architecture that can meet emerging technical advances in ocean science. These data are freely accessible online through the OOI cyberinfrastructure.

Office of Ocean Exploration

In the United States the Office of Ocean Exploration (OE) (now Office of Ocean Exploration and Research) is a division of the National Oceanic and Atmospheric Administration (NOAA) run under the auspices of the Office of Oceanic and Atmospheric Research (OAR).

OE facilitates ocean exploration by supporting expeditions, exploration projects, and related field campaigns. The focus of OE is very broad. They act as early explorers of area of the ocean that have not been seen. The goal is to bring information about the ocean that allows scientists to formulate questions that need to be answered about the ocean based on the preliminary information. In essence, OE acts as a scout or vanguard, much as Lewis and Clark did.

The mission of OE has four components:

Mapping the physical, biological, chemical and archaeological aspects of the ocean;

Understanding ocean dynamics at new levels to describe the complex interactions of the living ocean;

Developing new sensors and systems to regain U.S. leadership in ocean technology;

Reaching out to the public to communicate how and why unlocking the secrets of the ocean is well worth the commitment of time and resources, and to benefit current and future generations.

Princeton Ocean Model

The Princeton Ocean Model (POM) is a community general numerical model for ocean circulation that can be used to simulate and predict oceanic currents, temperatures, salinities and other water properties.

Rossby-gravity waves

Rossby-gravity waves are equatorially trapped waves (much like Kelvin waves), meaning that they rapidly decay as their distance increases away from the equator (so long as the Brunt–Vaisala frequency does not remain constant). These waves have the same trapping scale as Kelvin waves, more commonly known as the equatorial Rossby deformation radius. They always carry energy eastward, but their 'crests' and 'troughs' may propagate westward if their periods are long enough.

Self-locating datum marker buoy

A self-locating datum marker buoy (SLDMB) is a drifting surface buoy designed to measure surface ocean currents. The design is based on those of the Coastal Ocean Dynamics Experiment (CODE) and Davis-style oceanographic surface drifters – National Science Foundation (NSF) funded experiments exploring ocean surface currents. The SLDMB was designed for deployment by United States Coast Guard (USCG) vessels in search and rescue (SAR) missions, and is equipped with a Global Positioning Satellite (GPS) sensor that, upon deployment in fresh- or saltwater, transmits its location periodically to the USCG to aid in SAR missions. Additionally, SLDMB are deployed in oceanographic research in order to study surface currents of the ocean. This design has also been utilized by Nomis Connectivity for secure ocean-based communications.

Surface Water and Ocean Topography

The Surface Water and Ocean Topography (SWOT) mission is a future satellite jointly developed by NASA and CNES, the French space agency, in partnership with the Canadian Space Agency (CSA) and UK Space Agency (UKSA). The objectives of the mission are to make the first global survey of the Earth's surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time. While past satellite missions like the Jason series altimeters (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3) have provided variation in river and lake water surface elevations at select locations, SWOT will provide the first truly global observations of changing water levels, slopes, and inundation extents in rivers, lakes and floodplains. In the world's oceans, SWOT will observe ocean circulation at unprecedented scales of 15–25 km, approximately an order of magnitude finer than current satellites. Because it uses wide-swath altimetry technology, SWOT will almost completely observe the world's oceans and freshwater bodies with repeated high-resolution elevation measurements, allowing observations of variations.

Sverdrup balance

The Sverdrup balance, or Sverdrup relation, is a theoretical relationship between the wind stress exerted on the surface of the open ocean and the vertically integrated meridional (north-south) transport of ocean water.

Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

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