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Snellius Expedition
An oceanographic expedition taking place in 1929-1930 in the southwest Pacific Ocean.

Snellius II Expedition
See van Aken (1988).

See Southern Oscillation.

Acronym for Satellite Ocean Analysis for Recruitment, a OSLR project.

Acronym for the School of Ocean and Earth Science and Technology at the University of Hawaii at Manoa. It was established in 1988 and currently has approximately 700 faculty and staff. It consists of departments in Geology and Geophysics, Meteorology, Oceanography, and Ocean Engineering, as well as three institutes:


1. Acronym for Sound Fixing and Ranging channel, another name for the sound channel. 2. Acronym for SOund Fixing And Ranging floats, subsurface floats used since the mid 1970s that freely drift at prescribed pressures. These provide direct measurements of the ocean circulation by sending acoustic pulses, typically at 300 MHz, once a day which can be used to calculate their positions from their Times of Arrivals (TOAs) at listening stations moored near the SOFAR channel depth at known geographical positions. See Rossby and Webb (1970).

Acronym for Southern Ocean Iron (Fe) Experiment. The original name for this was IronEx III.

Acronym for Surface of the Ocean, Fluxes and Interactions experiment. See Dupuis et al. (1993).

soft tissue pump
See organic matter pump.

See Southern Oscillation Index.

Acronym for Southern Ocean Iron RElease Experiment, an experiment taking place from January 31 to March 1 1999 on the R.V. Tangaroa in the Southern Ocean. A patch of seawater was enriched with iron to test the hypothesis that iron limits the primary production of phytoplankton.

The iron and sulphur hexafluoride (as a tracer) were initially released on Feb. 10 at a site with a mixed layer depth of about 65 m and with low chlorophyll $ \alpha$ levels. The dissolved iron concentration was considerably elevated over the 50 square kilometer area, although the levels quickly decreased leading to three more iron infusions during the 13-day experiment. The patch moved about 40 nautical miles eastward and expanded to about 150 square kilometers during the experiment.

Five days after the initial release significant increases in algal photosynthetic competence were observed, followed by elevated algal biomass. Chlorophyll $ \alpha$ and upper ocean dimethylsulfide levels increased significantly by the end of the experiment, while macronutrient levels, the partial pressure of carbon dioxide, and the contnet of total dissolved inorganic carbon decreased. See Boyd et al. (2000) and Boyd and Law (2001).


solitary wave
See soliton.

A fundamentally nonlinear wave that propagates undistorted over great distances. The soliton or solitary wave was discovered by Scottish engineer John Scott Russell (1808-1882) in 1834 while conducting experiments to determine the most efficient design for canal boats. He describes his first observations of what he called a ``Wave of Translation'' ():
I was observing the motion of a boat which was rapidly drawn along a narrow channel by a pair of horses, when the boat suddenly stopped - not so the mass of water in the channel which it had put in motion; it accumulated round the prow of the vessel in a state of violent agitation, then suddenly leaving it behind, rolled forward with great velocity, assuming the form of a large solitary elevation, a rounded, smooth and well-defined heap of water, which continued its course along the channel apparently without change of form or diminution of speed. I followed it on horseback, and overtook it still rolling on at a rate of some eight or nine miles an hour, preserving its original figure some thirty feet long and a foot to a foot and a half in height. Its height gradually diminished, and after a chase of one or two miles I lost it in the windings of the channel. Such, in the month of August 1834, was my first chance interview with that singular and beautiful phenomenon which I have called the Wave of Translation.

See Bullough (1988) and Sander and Hutter (1991) for the historical development of the concept of solitary waves, which weren't wholly appreciated until the advent of digital computers made it possible to much more thoroughly investigate their characteristics and use them to model physical situations. Today solitons or solitary waves are used as a constructive element to formulate the complex dynamical behavior of wave systems in almost all facets of science, e.g. hydrodynamics, nonlinear optics, plasmas, shock waves, tornados, the Great Red Spot of Jupiter, etc.


Acronym for Sounding Oceanographic Langrangian Observer, a second-generation ALACE float designed to correct the design flaws of the latter. The SOLO uses a single-stroke hydraulic pump allowing full up-down control, and eliminates the internal oil bladder. See Davis et al. (2001).

Solomon Sea
More later.

solubility pump
The process by which the ocean maintains a vertical gradient in DIC (CO2 plus bicarbonate and carbonate ions) - such that DIC is concentrated in the deep ocean - as a result of gas exchange. Surface water at equilibrium with a given CO2 concentration will increase its DIC concentration (uptake CO2) when the water temperature decreases since the solubility and dissociation of CO2 increase in cold water. The regions of deep water formation are located in high latitudes so the deep ocean is filled with cold water with relatively high DIC concentration. It is estimate that about 50% of the vertical DIC gradient can be accounted for by this process. See Najjar (1991) and Chisolm (1995).

solution drift
See climate drift.

Somali Current
A current near the western boundary of the Indian Ocean that flows southward during the boreal winter and northward during the summer. The southward flow during the northeast monsoon is limited to south of 10$ ^\circ$N. It occurs first in early December near the equator and expands rapidly north in January with velocities from 0.7-1.0 m/s. The surface flow reverses in April during the inter-monsoon period, and develops into an intense jet during the southwest monsoon with velocities reaching 3.5 m/s in June. During the southwest monsoon a two gyre system develops in the region - the Great Whirl between 5-10$ ^\circ$N with clockwise rotation and a secondary eddy towards its south. This two gyre system is stable until August or September, when the southern gyre propagates northward and merges with the Great Whirl. This has also been called the East Africa Coast Current. See Schott (1983) and Schott and Fischer (2000).

Somali Jet
See Halpern and Woiceshyn (1999).

Acronym for Sampling, Observations and Modeling of Atlantic Regional Ecosystems, a program whose overall goal is to unify the diverse European research groups investigating the functioning, effects and responses of the regional ecosystems of the Atlantic Ocean and shelf seas to anthropogenically forced and climate related changes. The scientific goals of SOMARE include improving knowledge of:


Abbreviation for Ship of Opportunity Program, an IOC project that uses merchant and other volunteer ships that transit a series of tracklines over existing trade routes. These ships deploy XBTs and other sampling instrumentation to obtain upper ocean thermal and salinity data. The primary goal of SOOP is the fulfill upper ocean data requirements established by GOOS and GCOS, which can be met at present by measurements from ships of opportunity.


Soret effect
In fluid mechanics, mass diffusion caused by a temperature gradient. See Hurle and Jakeman (1971).

Acronym for Sound Surveillance System, a component of the U.S. Navy's Integrated Undersea Surveillance Systems (IUSS) network used for deep ocean surveillance during the cold war. SOSUS consists of bottom-mounted hydrophone arrays connected by undersea communication cables to onshore facilities. The arrays are primarily installed on continental slopes and seamounts at locations optimized for undistorted long range acoustic propagation. Beginning around 1990, the Navy allowed SOSUS to be used for various research activities. See Nishimura and Conlon (1994).


sound channel
A narrow channel in which sound waves can be effectively trapped. A region of minimum sound speed is created where the bottom of the thermocline meets the top of the deep isothermic layer. The velocity of sound slows as water temperatures decrease approaching the thermocline from above. The temperature is relatively constant below the thermocline, but increasing pressure causes the speed of sound to increase downwards. This causes obliquely traveling horizontal sound waves to vertically bend back and forth within the sound channel and travel great distances with relatively minor energy loss. This is also known as the SOFAR channel.

source water type
In physical oceanography, a point on a T-S diagram indicative of a water mass. In practice, few if any water masses have T-S values identical to that of their source water types due to transformation by atmosphere-ocean interface processes and/ mixing, but they are almost inevitably within the theoretical standard deviation and as such readily identifiable as to their origin. See Tomczak and Godfrey (1994).

South Atlantic Bight
See Boicourt et al. (1998).

South Atlantic Central Water (SACW)
A variety of Central Water found in the Atlantic Ocean south of about 15$ ^\circ$N. It shows uniform properties throughout its range, with the T-S curve well described by a straight line between the points 5$ ^\circ$C, 34.3 and 20$ ^\circ$C, 36.0. Part of the SACW is thought to be Indian Central Water (ICW) brought into the Atlantic by Agulhas Current intrusions. See Stramma and England (1999).

South Atlantic Current
The current band of increased zonal speeds associated with the Subtropical Front (STF) in the South Atlantic Ocean. It originates in the western Atlantic as the STF becomes clearly distinguished from the Brazil Current front somewhere between 40 and 45$ ^\circ$ W. It then flows eastward typically to the north of the STF and closes the circulation in the South Atlantic subtropical gyre by becoming its southern limb. The SAC is clearly separated from the ACC by a region of weak flow just to the south of the STF, and is seen to not follow the STF exactly in some observations. It is recognizable as an enhanced current core at depths of 800-1000 m and has an average volume transport of about 30 Sv in the upper 1000 m in the western Atlantic (reaching as high as 37 Sv). The transport diminishes to less than 15 Sv in the vicinity of southern Africa where it turns northward to feed the Benguela Current. See Stramma and Peterson (1990) and Peterson and Stramma (1991).

South China Sea
A regional sea in the western Pacific Ocean centered at about 115$ ^\circ$ E and 12$ ^\circ$ N that includes the Gulf of Thailand and the Gulf of Tonkin. It is bordered to the west by Vietnam, Thailand and the Malay Peninsula, to the south by a line joining the southern tip of the Malay Peninsula to Borneo, to the east by Borneo, the Phillipines and Taiwan, and to the north by the Taiwan Strait and China. It covers an area of 3,685,000 km$ ^2$, has a volume of 3,907,000 km$ ^3$, a mean depth of 1060 m, and a maximum depth of 5016 m.

It is connected to the East China Sea via the Taiwan Strait, the Andaman Sea via the Strait of Malacca, the Java Sea via the Karimata Strait, and to the Philippine Sea via Luzon Strait, and the Sulu Sea via the Balabar Strait and the Mindoro Channel. The main freshwater input from rivers is from the Red and Mekong Rivers of Vietnam and the Si Kiang River of southern China. See Qu et al. (2000).

Southeast Indian Subantarctic Mode Water (SEISAMW)
A type of Subantarctic Mode Water formed in the southeastern Indian Ocean south of Australia. It is the dominant mode of ventilation for the Indian Ocean, leading to a subsurface oxygen maximum layer extending northward into the tropical and northern Indian Ocean.

Southeast Pacific Deep Water (SPDW)
The SPDW flows through the Drake Passage with the ACC south of the Polar Front, at which point it is identifiable by its potential temperature ( $ {0.2^\circ}C\,<\,\theta\,<\,{0.6^\circ}C$), salinity (34.703 $ <$ S $ <$ 34.710), and its silicate maximum (reaching 140 $ \mu$mol kg$ ^{-1}$). It is the densest water mass of the ACC system in the Drake Passage.

When crossing the Scotia Sea, it is drastically cooled (by 0.14$ ^\circ$C) and freshened (by 0.018) along isopycnals via mixing with WSDW and WDW in the Weddell-Scotia Confluence. This results in the SPDW south of the Southern ACC Front being transformed into WDW and becoming incorporated into the ACC, while north of the front two cores carrying modified SPDW exit the Sea. One of these is on the northern flank of the Southern ACC Front south of South Georgia, having followed the front from Drake Passage. The other overflows the North Scotia Ridge through Shag Rocks Passage and can be found just south of the Polar Front skirting the Falkland Plateau. See Siecers and Nowlin Jr. (1984).

South Equatorial Countercurrent
An eastward current in the Atlantic and Pacific that flows between 5 and 10$ ^\circ$ S., the limited evidence for which shows it to be much less well developed than the North Equatorial Countercurrent (NECC). In the Indian Ocean the SECC is almost totally confined between the equator and the northern boundary of the South Equatorial Current (SEC) at 4$ ^\circ$ S. This was first described by Reid (1959) and the evidence is later reviewed by Leetmaa et al. (1981).

South Equatorial Current
A westward flow in the Atlantic and Pacific located south of the North Equatorial Countercurrent (NECC) generally below 5$ ^\circ$ N. It flows between about 3$ ^\circ$ N and 10$ ^\circ$ in the Pacific with speeds estimated at around 50 to 65 cm s$ ^{-1}$ and an average mean transport of 17 SV, although this latter quantity annually varies by about 10 Sv about the mean. The SEC is strongest during July and August and usually vanishes during the northern winter and spring. This is also seen in the Indian Ocean south of 4$ ^\circ$ S. See Leetmaa et al. (1981) and Stramma (1991).

South Equatorial Current Bifurcation
The phenomenon wherein the Atlantic South Equatorial Current (SEC) - upon approaching the easternmost tip of South America - splits into the Brazil Current flowing to the south and the North Brazil Current flowing northwestward along the northern coastline of Brazil.

South Equatorial Undercurrent
An eastward flow in the Atlantic Ocean whose core is located near 200 m depth a few degrees south of the Equator. A satisfactory dynamical explanation for this is as yet nonexistent. See Tomczak and Godfrey (1994), p. 260.

South Java Current
See Tomczak and Godfrey (1994).

South Subtropical Front (SSTF)
The southern boundary of the Subtropical Frontal Zone (STFZ).

South Tropical Countercurrent
See Donguy and Henin (1975).

Southern ACC Front
A front in the Southern Ocean that separates the Antarctic Zone (AZ) to the north from the Continental Zone (CZ) to the south. The position of the SACCF is usually indicated by a distinct temperature gradient along the $ \sigma$-maximum of the Upper Circumpolar Deep Water (UCDW) as it shoals southward to near 500 m. The property indicators of the SACCF are $ \theta\,>$ 1.8$ ^\circ$ along $ \theta$-maximum at Z $ >$ 500 m, $ \theta\,<$ 0$ ^\circ$ along $ \theta$-minimum at Z $ <$ 150 m, S $ >$ 34.73 along S-maximum at Z $ >$ 800 m, and O$ _2$ $ <$ 4.2 ml/l along O$ _2$ minimum at Z $ >$ 500 m. The SACCF is one of three fronts found in the Antarctic Circumpolar Current (ACC), the others being (to the north) the Polar Front (PF) and the Subantarctic Front (SAF). See Orsi et al. (1995).

Southern Ocean
In oceanography, an unofficial term used to describe the oceans surrounding the continent of Antarctica, which comprise approximately 22% of the world's ocean area. The northern limit is the broad zone of transition where the permanent thermocline reaches the surface at the Subtropical Convergence (STC). The southern limit is the continent of Antarctica. It is distinguished from the other oceans by the relative uniformity of its hydrography and circulation, and that it influences more than it is influenced by the others.

The Southern Ocean bathymetry consists of three major basins where the depth exceeds 4000 m separated by three major ridges that reach at least to the 3000 m level. These are (proceeding from the Pacific sector west): (1) the Amundsen, Bellingshausen, and Mornington Abyssal Plains, sometimes called the Pacific-Antarctic Basin, (2) the Macquarie, Pacific-Antarctic, and Southeast Indian Ridge sytem, (3) the Australian-Antarctic Basin, (4) the Kerguelan Plateau, (5) the Ender and Weddell Abyssal Plains, also known as the Atlantic-Indian Basin, and (6) the Scotia Ridge. See Belkin and Gordon (1996).

Southern Oscillation
The name given to the atmospheric component of the El Nino/Southern Oscillation (or ENSO) phenomenon. The SO is a large-scale shift in atmospheric mass between the western and eastern Pacific, monitored by computing the SOI. An SOI indicating El Nino conditions means that there is reduced rainfall over the Indonesian region and that the west Pacific convective center is displaced eastward along the equator.

Southern Oscillation Index
An index that is calculated to monitor the ENSO phenomenon. It is defined as the pressure anomaly at Tahiti minus the pressure anomaly at Darwin, Australia. Anomalously high pressure at Darwin and low pressure at Tahiti are indicative of El Nino conditions.

Southern South Equatorial Current (SSEC)
One of three distinct branches into which the South Equatorial Current splits in the western South Atlantic. See Stramma (1991).

Southern Subsurface Countercurrent (SSCC)
An eastward flowing countercurrent that flows beneath the surface east of 155$ ^\circ$ in the South Pacific Ocean. It flows between the eastward flowing South Equatorial Countercurrent (SECC) to the north and the westward flowing South Equatorial Current to the south. See Gouriou and Toole (1993).

South Pacific Equatorial Water (SPEW)
In physical oceanography, a water mass partly formed by convective sinking of surface water at SSTs of 26$ ^\circ$ C and above in the tropics in the area of Polynesia. It is identified at temperatures greater than 20$ ^\circ$ C by a higher salinity than WSPCW, although below 20$ ^\circ$ C it seems to be a mixture of WSPCW and ESPCW. See Tomczak and Godfrey (1994), p. 166.

South Pacific Tropic Water (SPTW)
A water mass identified as a salinity ($ >$35.25 psu) maximum with homogeneous oxygen concentration (about 3.3 ml l$ ^{-1}$) around 25 $ \sigma_\theta$. it is found in the equatorial region south of 5$ ^\circ$N. See Qu et al. (1999).

South Trench Current
See North Sea.

Southwest Area Monsoon Project (SWAMP)
A NSSL project begun in 1990 to measure the central Arizona thunderstorm environments, examine the local monsoon structures and moisture fluxes, and study Mexican convective systems. The field operations for SWAMP began in 1990 and included scientists and technicians from several institutes and laboratories. See the SWAMP Web site.

Southwest Monsoon Current
See Vinayachandran et al. (1999).

Acronym for Southern Ocean Waves Experiment, an international collaborative air-sea interaction experiment in which a specially instrumented meteorological research aircraft simultaneously gathered atmospheric turbulence data in the marine boundary layer and sea surface topography data over the Southern Ocean for a wide range of wind speeds. The aim was to increase present knowledge of severe sea state air-sea interaction. SOWEX was carried out from June 10-16, 1992 over the Southern Ocean off the southwest coast of Tasmania, Australia at 42-45$ ^\circ$S, 143-147$ ^\circ$E. See Banner et al. (1999) and Chen et al. (2001).

Soya Current
An extension of the Tsushima Current that flows northward from the Japan Sea into the Okhotsk Sea via the Soya Strait. It is a fairly rapid curent with velocities reaching 1 m/s and traveles close to the coast with the character of a boundary current.

Soya Strait
See Okhotsk Sea.

Abbreviation for Salinity-Profiling ALACE float.

Spanish Basin
See Iberia Basin.

Abbreviation for South Pacific Convergence Zone, an atmospheric convergence zone in the southwestern Pacific Ocean that is characterized more by a convergence in wind direction than as a wind speed minimum. It extends from east of Papua New Guinea in a southeastward direction towards 120$ ^\circ$ E and 30$ ^\circ$ S. See Philander and Rasmusson (1985).

specific heat
A thermodynamic quantity indicating the rate of change of heat content with temperature. More specifically, this is the heat required to raise the temperature of a unit mass of a given substance by one degree. It is normally expressed in units of calories/gm $ ^\circ$K. The specific heat of water is 1.00 cal/gm $ ^\circ$K (although this varies about 1% with temperature), and the specific heat of dry air at constant pressure (C$ _p$) is 0.240 cal/gm $ ^\circ$K and at constant volume (C$ _v$) 0.171 cal/gm $ ^\circ$K. For water vapor the constant pressure (C$ _{pv}$) value is 0.441 and the constant volume (C$ _{vv}$) value 0.331 cal/gm $ ^\circ$K.

For seawater, the specific heat at surface pressure is calculated in two stages. First, the value in joules per kilogram per degree Kelvin for fresh water is calculated as:

$\displaystyle {c_p}(0,t,0)\,=\,4217.4 - 3.720283t + 0.1412855{t^2} -
2.654387 \times {10^{-3}}{t^3} + 2.093236 \times {10^{-5}} {t^4}$

. Then, the value at a given salinity is calculated with:

$\displaystyle {c_p}(S,t,0)\,=\,{c_p}(0,t,0) + S(-7.64444 + 0.107276t - 1.3839 \...
...) + {S^{3/2}}(0.17709 - 4.0772 \times {10^{-3}}t +
5.3539\times {10^{-5}}{t^2})$

. The standard deviation of the algorithm fit is 0.074, and a check on the formula is given by $ {c_p}(40,40,0)\,=\,3981.050$. See Millero et al. (1973) for the derivation and details. Values at nonzero pressures are found using the following relation:

$\displaystyle {{\left({{\partial{c_p}} \over {\partial p}}\right)}_T}\,=\,-T\,
{{\left({{{\partial^2}{v_s}} \over {\partial {T^2}}}\right)}_p}$

where $ v_s$ is the specific volume. See also Cox and Smith (1959).

specific humidity
The ratio of the mass ($ m_v$) of water vapor to the mass ($ m_v$ + $ m_a$) of moist air in which $ m_v$ is contained, where $ m_a$ is the mass of dry air, or

$\displaystyle q\,=\,{{m_v}\over{{m_v}\,+\,{m_a}}}$


specific volume
The reciprocal of density. In the determination of the specific volume of sea water, the specific volume $ \alpha_{S,T,p}$ is decomposed as

$\displaystyle \alpha_{S,T,p}\,=\,\alpha_{35,0,p}\,+\,{\delta_S}\,+\,{\delta_T}\,+\,

where the second through seventh terms on the right-hand-side are called the specific volume anomaly and the second through fourth terms the thermosteric anomaly.

specific volume anomaly
The portion of the specific volume differing from a standard specific volume determined at a salinity of 35 ppt, a temperature of 0$ ^\circ$ C, and the pressure at the depth at which the sample was taken. This has also been known as the steric anomaly and the anomaly of specific volume.

spectral element method
A method for approximating solutions to the governing equations of fluid motion in the ocean. It was developed to combine the geometrical flexibility of the traditional low-order finite element methods with the accuracy and high convergence rates of spectral methods. See Iskandarani et al. (1995).

spectral nesting
See nested modeling.

spectral signature
This refers to the particular form or shape evinced by the power spectrum calculated from the data comprising the time series of a process. For example, if the spectrum shows peaks at around 20, 40 and 100 thousand years it might be said to have the spectral signature of Milankovitch orbital variations.

See South Pacific Equatorial Water.

spherical approximation
The fundamental geometric approximation in oceanography. It maps the approximate oblate spheroidal shape of the geoid on a sphere and introduces spherical polar coordinates $ (\phi , \theta , r)$ where $ \phi$ is longitude, $ \theta$ is latitude, and $ r$ radial distance. This approximation also assumes that the metric coefficients do not vary with radial distance, and that gravitational acceleration is constant.

This approximation represents the lowest order in an expansion of the metric with respect to two small parameters $ {d^2}/4{r_0^2}$ and $ {H_0}/{r_0}$ where $ d$ is the half distance between the foci of the geoid, $ r_0$ the mean radius of the Earth, and $ H_0$ the ocean depth. A vertical coordinate $ z\,=\,r\,-\,{r_0}$ is also introduced. See Stommel and Moore (1989) and Muller (1995).

Spice Experiment
An exploratory experiment to observe spiciness in the upper ocean, including the mixed layer, at horizontal scales of 10 m to 1000 km. The objectives of the Spice Experiment are:

The data for the experiment were taken from a cruise in the eastern North Pacific between 25 and 35$ \deg$ N from Jan. 24 to Feb. 20, 1997. Measurements were made using a SeaSoar equipped with a CTD and a fluorometer.


The variability of temperature and salinity along a surface of constant density due to air-sea fluxes, turbulent mixing and advection.

Spilhaus, Athelstan (1912-1998)
Inventor of the bathythermograph and possibly the only oceanographer to have ever authored a regular comic strip.

According to his obituary in The Economist, Spilhaus can also apparently be blamed for the Roswell Incident that's spawned an entertainment industry:

In 1947 the Americans were working on ways to monitor nuclear tests in the Soviet Union. One plan was to put aloft balloons equipped with the necessary detection equipment. The first experiments were failures. The balloons all blew away. Mr Spilhaus, then a professor of meteorology at New York University, was brought in. As a weather man, so the reasoning went, surely he would know how to ensure that the balloons stayed quite steady in the stratosphere.

On June 4th 1947 the Spilhaus prototype was launched. On July 7th it came down with a bump, disintegrating on a ranch near Roswell in New Mexico. The rancher phoned the local sheriff. He thought the debris might have come from "a flying disc". By the time the story got into the newspapers the "disc" had become a flying saucer. A neighbour of the rancher later said that in the debris there was "something like aluminium, something like satin, something like well-tanned leather in its toughness, yet was not precisely like any one of those materials". Could this have been a dead alien, or possibly several? Many people came to think so.

An air force team removed every scrap of debris, assuring reporters that it was just an ordinary balloon, nothing to be bothered about; and compounding suspicions that the federal government was trying to cover up the fact that aliens had landed, fearing panic by the public. It was not until 1994 that it disclosed the background to the incident. Even now, the government version is widely disbelieved. The myth was much more interesting. Mr Spilhaus could say little: this was a secret of the cold war. But the fact that he was known to be associated with the incident only added to public speculation about it. Mr Spilhaus enjoyed playing the role of a slightly dotty scientist, a bit of a dreamer, or, as he called himself in later life, a "retired genius".


spin up
In numerical modeling, this refers to the transient initial stages of a numerical ocean simulation when the various fields are not yet in equilibrium with the boundary and forcing functions. Three techniques are generally used to initialize and spin up the ocean components of coupled models: (1) initializing with climatological values of temperature and salinity (typically using the Levitus climatology) throughout the volume of the ocean; (2) start with the aforementioned Levitus ocean and then spin it up for about 100 years using surface climatological forcing; (3) run the ocean to equilibrium by either combining surface forcing terms with atmospheric model fluxes or just using the surface forcing (and perhaps using an acceleration method with either option). The entire ocean is not in equilibrium using the first two methods, although the second method does allow the thermocline to adjust to equilibrium. This is due to both systematic errors and other shortcomings in the Levitus data. The third method may produce and ocean in equilibrium, but it may differ considerably from the observed ocean and the circulation may be distorted. For example, the deep ocean is often too warm using this method.

Abbreviation for subpolar mode water.

spring retardation
See age of tide.

spring tide
The high tides of greatest amplitude caused by the Earth, Sun and Moon being almost co-linear. This causes the gravitational pulls of both the Sun and Moon to reinforce each other. The high tide is higher and low tide is lower than the average, and spring tides occur twice a month at the times of both new moon and full moon. See also neap tide.

Abbreviation for South Pacific Tropical Water.

Acronym for Self-Propelled Underwater Research Vehicle. See Widditsch (1973).

Acronym for SeaWiFS Quality Monitor. See Hooker and Aiken (1998).

A violent wind that begins suddenly, lasts for a short time, and dies suddenly. It is sometimes associated with a temporary change of direction.

squall line
One of the most severe kinds of storms in the tropics. The system is typically hundreds of miles long and consists of a line of active thunderstorms. The cumulonimbus clouds representing individual storms have lifetimes on the order of an hour or less, but new ones replace dying cells allowing the system as a whole to last from hours to days. They form preferably over land and move with speeds from 10-20 m/s.

In a squall line warm moist air enters the base of the cloud at its leading edge and rises in a convective updraft with accompanying condensation. An extensive cloud anvil forms to the rear of the convective tower with precipitation falling from both the main cloud column and the anvil. The evaporation of this precipitation into dry mid-tropospheric air leads to cooling and downdrafts concentrated in the region of intensive convection although extending to the rear of the squall line. This downward rushing cold air causes a pseudo cold front or gust front at the leading edge. This front undercuts the warm moist air ahead, causing more convection and new cumuliform clouds ahead of the line and fostering the propagation of the convective region. See Hastenrath (1985).

See Singular Spectrum Analysis.

Acronym for the single-frequency solid-state radar altimeter flow flown as an experimental instrument on the TOPEX/POSEIDON mission (with this being known as the POSEIDON instrument). The SSALT, a solid-state Ku-band (13.65 GHz) altimeter, was developed by the French (CNES) as a demonstration project for a low-power, low-weight altimeter for future Earth-observing missions. It shares the same antenna with ALT, the operational altimeter, and thus cannot be operated at the same time. The SSALT was operated 12.5% of the time during the 6 month verification phase of the mission, and thereafter for one (10 day) cycle approximately every 10 cycles.

1. Abbreviation for Southern Subsurface Countercurrent. 2. Abbreviation for subsurface countercurrent.

Abbreviation for SouthernSouthEquatorialCurrent.

Abbreviation for sea surface temperature.

Abbreviation for South Subtropical Front Zone.

Abbreviation for Sargasso Sea Water.

Abbreviation for Seismic Sea-Wave Warning System.

1. See numerical stability. 2. In physical oceanography, a measure of the tendency of a water parcel or particle to move vertically in comparison with its surroundings. Neglecting adiabatic effects, the stability is defined (over short vertical distances) by

$\displaystyle E\,=\,{1\over \rho}{{d\rho}\over{dz}}$

where $ \rho$ is the density and $ z$ the vertical coordinate. There is a correspondingly more complicated expression for the stability when adiabatic effects are taken into account as is usually necessary at great depths. Typical values of $ E$ in the upper 1000 m range from 100 to 1000 x $ 10^{-8}$/m, with the largest values generally occurring in the upper few hundred meters. Below 1000 m values decrease to less than 100 x $ 10^{-8}$/m and can get as small as a hundredth of that in deep trenches.

stability frequency
See buoyancy frequency.

Acronym for Stable Antarctic Boundary Layer Experiment.

Acronym for Subtropical Atlantic Climate Study, a NOAA project directed at increased understanding of the role of western boundary currents of the Atlantic ocean in meridional heat flux and development of strategies to monitor important western boundary features. See Molinari (1989).

staggered grid
In numerical analysis this refers to a computational grid in or on which separate dependent variables are represented on alternate or staggered grid points. For example, a 1-D equation set for pressure and velocity would be solved on a grid where the pressure is represented at points n, n+2, n+4, etc. while the velocity is represented at n+1, n+3, n+5, etc. This procedure can confer numerical advantages and is also used for problems with more than one spatial dimension. See Kowalik and Murty (1993).

stagnant film model
The simplest of several models developed to understand the processes that determine the gas flux in and near the liquid boundary layer that is the air-sea interface. It assumes that the boundary layer is a discrete, stagnant layer in which only molecular diffusion takes place. This stagnant layer sits on top of a well-mixed, purely turbulent layer. The flux across the interface is assumed to be equal to the flux in the stagnant film which, using Fick's law, gives a linear concentration profile within the film. This leads, with the additional use of Henry's law, to an expression for the flux involving the gas concentration at the base of the film ($ C_w$), the partial pressure of the gas in the atmosphere ($ p_a$), the solubility of the gas in seawater ($ \alpha$), and the piston velocity ($ K_w$), i.e. $ F = {K_w}({C_w}-\alpha {p_a})$. See Najjar (1991).

Standard Atmosphere
An idealized, dry, steady-state approximation of the atmospheric state as a function of height that has been adopted as an engineering reference. It was not computed as a true average but rather approximates average atmospheric conditions at mid-latitudes. It is a piecewise continuous curve consisting of straight-line segments with breaks at 11, 20, 32, 47, 51 and 71 km. The surface temperature is $ {15}^\circ$ C and the gradients, starting from the surface, are -6.5, 0.0, 1.0, 2.8, 0.0,-2.8, and -2.0 K/km. Pressure variations can be found from this by combining the hydrostatic equation with the equation of state for dry air and integrating the result, i.e.

$\displaystyle {1\over p}\,{{dp}\over{dz}}\,=\,{{-g}\over{RT}}$

with respect to height. See Minzner (1977).

standard density
A conventional value for the density of mercury, adopted for the sake of uniformity in the conversion of pressure readings from units of pressure to units of height (or the converse). The value adopted by the WMO is the density at 0$ ^\circ$ C, i.e. 13.5951 gm/cm$ ^3$.

standard gravity
A conventional value for the acceleration due to gravity, adopted for the sake of uniformity. The value adopted by the WMO is 980.665 cm/sec$ ^2$.

standard seawater
See Culkin and Smed (1979), Culkin and Ridout (1998) and Bacon et al. (2000).

Acronym for Southern Tropical Atlantic Regional Experiment, a project within BIBEX. STARE is an aircraft- and ground-based measurement program initiated in May 1990 by a committee of scientists from Europe, Brazil and the U.S. to investigate the sources of trace gases, their atmospheric transport, and the chemical processes in the atmosphere which lead to elevated levels of O$ _3$, CO, and other trace gases over the southern tropical Atlantic Ocean. The field campaigns conducted under STARE were TRACE-A, SAFARI, and SA'ARI. See Andreae et al. (1996).

The property requiring that certain statistical properties of a stochastic process be invariant with respect to time. As some have noted, the strict satisfaction of this requirement is impossible if one lends creedence to the Big Bang theory of universal origin, although inroads can be made towards satisfaction on less strict and more pragmatic grounds.

stationary planetary wave
Departures of the time average of the atmospheric circulation from zonal symmetry. They result from east-west variations in surface elevation and temperature associated with the continents and oceans. See Hartmann (1994).

statistical downscaling
A procedure wherein local or regional climate characteristics are inferred from the output of GCMs that don't explicitly resolve such scales. Statistical relationships between observed local climate variables, e.g. surface air temperature, precipitation, etc., and observed large-scale predictors are developed and then applied to the same large-scale predictors in the GCM output to predict the local climate variables. This method has been shown to produce local temperature and precipitation change fields that were significantly different and had a finer spatial scale structure than those generated by directly interpolating large-scale GCM fields. See Houghton and Filho (1995).

statistically robust
Statistical results which are relatively insensitive to the presence of a moderate amount of bad data or to inadequacies in the statistical model being used, and that react gradually rather than abruptly to perturbations of either. See Chave et al. (1987) for a discussion of this in relation to geophysical data.

1. See Subtropical Convergence. 2. See South Trench Current.

Abbreviation for Salinity-Temperature-Depth. See CTD.

A temperature profiler for measuring the oceanic thermal boundary layer at the ocean-air interface. See Mammen and von Bosse (1990).

steric anomaly
Another name for the specific volume anomaly.

steric height
In oceanography, a quantity introduced to determine the distance or depth difference between two surfaces of constant pressure. The steric height $ h$ is defined by

$\displaystyle h({z_1},{z_2})\,=\,{\int_{z_1}^{z_2}}\,\delta (T,S,p)\,{\rho_0}dz$

where $ z_1$ and $ z_2$ are the depths of the pressure surfaces, $ \delta$ the specific volume anomaly, $ T$ the temperature, $ S$ the salinity, $ p$ the pressure, and $ \rho_0$ a reference density. It has the dimension of height and is expressed in meters.

STERNA Expedition
A two-ship study carried out in the Bellingshausen Sea, Southern Ocean from October to December, 1992. The STERNA project, carried out aboard the Royal Research Ships James Clark Ross and Discovery, was the final field-work phase of the NERC-funded BOFS (the major U.K. contribution to the IGBP JGOFS over the period 1989-1993). The study was originally developed to also include an investigation of biogeochemical fluxes during the spring ice-melt in the Greenland Sea, and was named STERNA after the migrations carried out by the tern Sterna paradisea, during which individual commonly spend alternate summers in each polar region. The northern component was cancelled because of major refitting work on the research ships, but the name was retained.

The objectives of the STERNA Expedition were:

See Turner and Owens (1995).

Abbreviation for Subtropical Front.

Abbreviation for Subtropical Frontal Zone.

still water level
The level of the sea with high frequency motions such as wind waves averaged out. See also mean sea level.

Abbreviation for Subtropical Mode Water.

stochastic process
A reasonably strict definition of this (also called a random process) is a family of random variables indexed by t, where t belongs to some index set T (which may denote time, space, or whatever else one wishes). A more intuitive definition might call this the set of all possible outcomes of an experiment (this set also being called the ensemble) inherently involving some degree of randomness along with the mechanism by which individual outcomes, or realizations, selected.

Acronym for Study of Tropical Oceans in Coupled Models, a project for the intercomparison of tropical ocean behavior in coupled ocean-atmosphere models on seasonal and interannual scales. It focuses on the Atlantic and Indian Ocean regions and their relationship to the Pacific Ocean. This project is designed to be complementary with the ENSIP program.


Stokes drift
A mean Lagrangian current that can be generated by surface gravity waves. This is caused when water particle orbits are not closed in surface gravity waves. A steady drift results even if no mean currents are present. See Stokes (1847) for the original work and McWilliams and Restrepo (1991) for a review of possible effects on ocean circulation. See also Ianniello and Garvine (1975).

Stokes' theorem
A theorem of geophysical importance in that it enables one to calculate whether there is a tendency for a flow to be circulating around a curve $ C$, e.g. the Earth. It is mathematically expressed as

$\displaystyle \int{\int_S}\eta\cdot (\nabla\times v)\,d\sigma\,=\,
{\int_C}\tau\cdot v\,ds$

where $ \eta$ is the normal vector to a surface $ S$, $ \tau$ the tangent vector to the curve $ C$ bounding $ S$, and $ v$ the velocity vector field. This theorem, dealing with the integration of the curl of the velocity field (or, equivalently, the vorticity vector), allows us to evaluate whether or not the fluid is circulating (as well as rotating or spinning via the calculation of the vorticity vector itself). See Dutton (1986).

Stokes velocity
A velocity in fluids that derives from the wave Reynolds stresses. See the Stokes wave entry and compare to Lagrangian velocity and Eulerian velocity. See Wunsch (1981), p. 345.

Stokes wave
A wave theory whose theoretical development is the same as that for Airy waves except that second and higher order terms involving the wave height are retained. The expression for the wave surface elevation includes the Airy wave expression as the first term and a number of additional terms (depending on the order of the theory) that modify the elevation profile. The added terms generally enhance the amplitude of the wave crest and detract from the trough amplitude such that the crests are steeper and the troughs flatter.

The particle orbits in Stokes theory, unlike those in Airy wave theory, are not closed. This leads to a nonperiodic drift or mass transport in the direction of wave advance with an associated speed called the Stokes velocity. Stokes wave theory is generally limited in applicability to waves with steepness (i.e. $ H/L$ where $ H$ is the wave height and $ L$ the length) less than 1/100 in deep water, with even more severe restrictions in shallow water. See Komar (1976) and LeMehaute (1976).

Stommel, Henry Melson (1920-1992)
A physical oceanographer who has been called "the most significant scientific contributor to the development of oceanography", Stommel's long and distinguished career was marked not only by many significant scientific contributions to his field but also by his unsurpassed ability to help others in their research efforts and to catalyze the development of major research programs.

His scientific contributions included proposing the use of T-S correlations to estimate missing salinity values from measured temperatures in order to calculate dynamic heights, the beta spiral method for determining absolute geostrophic circulation fields, the initiation of studies of double diffusion, and the development in the early 1960s (along with Arnold Arons) of a model of abyssal circulation that still serves as the fundamental basis for further investigations today. His most famous contribution was his 1947 paper in which he developed an analytical model showing how the westward intensification of ocean currents is caused by the variation of the Coriolis parameter with latitude (i.e. the beta effect).

His efforts to foster research programs included the genesis of the long-term measurements of the deep waters off Bermuda in 1953, the planning (with K. Yoshida) of a survey of the Kuroshio Current in the late 1960s, the proposal of a dense network of oceanographic stations off the coast of Bermuda that resulted in the Mid-Ocean Dynamics Experiment (MODE), and the motivation of the geochemistry community to carry out the GEOSECS program.

His work led to hundreds of publications under his name and with dozens of collaborators. His books included Science of the Seven Seas (1945), The Gulf Stream (1966), Kuroshio (co-edited with K. Yoshida in 1972), Volcano Weather (co-written with his wife Elizabeth in 1983), Lost Islands (1984), A View of the Sea (1987) and Introduction to the Coriolis Force (co-written with Dennis Moore in 1989). He inspired the 1981 festschrift entitled Evolution of Physical Oceanography: Scientific Surveys in Honor of Henry Stommel (edited by B. Warren and C. Wunsch). The Collected Works of Henry M. Stommel (edited by N. Hogg and R. Huang) were published in three volumes in 1995. This set includes introductory essays for each chapter written by his many colleagues as well as previously unpublished material, e.g. about a hundred pages from his unpublished autobiography. See Veronis (1992), Warren and Wunsch (1981), and Hogg and Huang (1995).


Stommel-Arons thermohaline circulation
A model of global thermohaline circulation developed by Henry Stommel and Arnold Arons in a series of papers starting in 1961. This model combines sources of abyssal water at either pole, the turbulent mixing of warm surface water downward, the broad and slow upward flow of cold deep water, and deep western boundary currents in a dynamically consistent manner to provide a first-order explanation for that part of the general ocean circulation driven by spatial differences in the salinity, temperature and, therefore, density of sea water.

Stommel's demon
In the theory of the ventilated thermocline, a deepening mixing layer allows only a narrow range of density to subduct at any geographical location. Only water of a particular density class is able to enter the thermocline at a given position. Stommel likened the process to the role of the demons in Maxwell's theory of gases. This has led to referring to the selection process of subducted density as Stommel's demon. See Stommel (1979), Williams et al. (1995) and Pedlosky (1996).

storm surge
A phenomena wherein sea level rises above the normal tide level when hurricanes or tropical storms move from the ocean along or across a coastal region. Technically, this is defined as the difference between the actual sea (tide) level under the influence of a meteorological disturbance (storm tide) and the level which would have been reached in the absence of the meteorological disturbance. This sea level rise can consists of three components, the first of which results from low barometric pressure, i.e. the so-called inverse barometer effect, where lower atmospheric pressure on the surface of the water allows it to rise. The second component is wind set-up where the winds drag surface water to the shore where it piles up. The third component of the rise is due to coupled long waves where the peak of the wave coincides with the shoreline. See Wiegel (1964) and Heaps (1967).

Strait of Gibraltar
A shallow strait that separates the eastern Atlantic Ocean from the Mediterranean Sea. See Gascard and Richez (1985).

Strait of Hormuz
A strait joining the Persian Gulf to the west and the Gulf of Oman to the east. It is located at about 56$ ^\circ$ E and 27$ ^\circ$ N.

Strait of Magellan
According to Strub et al. (1998), ``Despite the strong southwesterly winds characteristic of the area, tides are the dominant forcing function for the currents, especially on the Atlantic side.'' See Medeiros and Kjerfve (1988) and Panella et al. (1991).

Strait of Messina
A narrow strait between between the southwestern tip of Italy and Sicily that connects the Tyrrhenian Sea in the north with the Ionian Sea to the south. It is a narrow channel whose smallest cross-sectional area is 0.3 km$ ^2$ in the sill region where the mean water depth is 80 m. The depth increases more rapidly in the southern than in the northern part, with the depths 15 km from the sill to the north and south being 400 m and 800 m, respectively. Both Tyrrhenian Surface Water (TSW) and Levantine Intermediate Water (LIW) are present year-round, separated at a depth of around 150 m. A seasonal thermocline is also present for most of the year with the difference across this interface generally much larger than than across the TSW/LIW boundary. Large gradients of tidal displacements are present despite generally small tides in the Mediterranean since the predominantly diurnal tides to the north and south are approximately in phase opposition. The tides combine with the topographic restrictions to allow current velocities to reach as high as 3.0 m s$ ^{-1}$ in the sill region. There is also a weak mean exchange flow directed toward the Ionian Sea with a velocity of about 0.10 m s$ ^{-1}$ in the surface layer, and toward the Tyrrhenian Sea at about 0.13 m s$ ^{-1}$ in the lower layer. See Bignami and Salusti (1990).

Straits of Sicily
A strait located at around 12$ ^\circ$ E in the Mediterranean Sea that separates the eastern and western basins. Its shallow sill separates the deep waters of the Tyrrhenian Sea to the northwest from those of the Ionian Sea to the southeast. See Fairbridge (1966).

In oceanography, the vertical density structure resulting from a balance among atmospheric heating, surface water exchange, freezing, stirring and diffusion of heat, and the horizontal and vertical motion (advection) of waters with different temperature and salinity characteristics.

stratified estuary
One of four principal types of estuaries as distinguished by prevailing flow conditions. This type is stratified with a halocline between the upper and lower portions of the water column of nearly constant salinity. The James and Mersey estuaries are examples of this type.

stratified fluid
See Fernando (1991).

stream function wave theory
A surface gravity wave theory wherein the wavelength $ L$, coefficients $ X(n)$, and the the value of the stream function on the free surface $ \psi_\eta$ are numerically determined given the wave height $ z$, the water depth $ h$ and the wave period $ T$. The expression for the stream function $ \psi$ in a reference frame moving with the speed of the wave $ C$ is

$\displaystyle \psi\,=\,\left({L\over T}\,-\,U \right) z\,+\,
{{2\pi n}\over L}\,(h\,+\,z)\right]\,\cos
\left({{2\pi n x}\over L}\right).$

The unknowns are determined to best satisfy the dynamic free surface boundary condition in the least squares sense.

The advantages of this wave theory are that it is one theory that can be applied to the full range from shallow to deep water and from small to breaking wave heights, and that fairly comprehensive tables are available for design purposes (and, more recently, computer programs). The original irrotational version of the theory has been extended to some rotational flows. Other representations in terms of the stream function or velocity potential have also been developed since the stream function theory was first described in 1965. See Dean (1990).

streaming velocity
A small first-order mean velocity near the bottom in the direction of wave motion that occurs in the presence of the vortical bottom boundary layer in water of finite depth. See Phillips (1977) and Longuet-Higgins (1986).

strength of ebb
In the description of tides, the magnitude of the ebb current at the time of maximum speed. This is usually associated with lunar tide phases at spring tides near perigee or with maximum river discharge. This is also known as ebb strength.

Acronym for Sediment Transport Events over Shelves and Slopes. See Sherwood et al. (1994).

Acronym for Storm Transfer and Response Experiment, a joint meteorological-oceanographic experiment carried out in the northwestern Pacific Ocean during November and December 1980. The purpose was to examine the response of the atmospheric and oceanic boundary layers to the passage of storms. See Fleagle et al. (1982), Paduan and DeSzoeke (1986) and Geernaert (1990).

Strouhal number
A dimensionless number or parameter proportional to the reciprocal of vortex spacing. It is expressed as a number of obstacle parameters and generally used in momentum transfer calculations, e.g. Von Karman vortex street and unsteady flow calculations. It is expressed as:

$\displaystyle {S_r}\,=\,{{f\,L}\over V}$

where $ f$ is a frequency, $ L$ a characteristic length scale, and $ V$ a characteristic velocity.

Acronym for Submersible System Used to Assess Vented Emissions, an integrated instrument system consisting of an advanced chemical analyzer and an array of physical property sensors. SUAVE is used to investigate the chemical properties of hydrothermal vents. The chemical analyzer is based on the principles of flow analysis and colorimetric detection, and its main components include:

The auxiliary sensors include:

SUAVE was built in 1991 and has been deployed over 200 times to date, accumulating more than 1500 hours of in situ analysis time, all directed toward hydrothermal vent research. Over 1000 km of ridgecrest with hydrothermal plumes have been investigated, with the thermochemical attributes determined with spatial detail seldom achieved anywhere on the sea floor. See Massoth et al. (1992).


Subantarctic Front
In physical oceanography, a region of rapid transition in the Southern Ocean (S)) between the Polar Frontal Zone (PFZ) to the south and the Subantarctic Zone (SAZ) to the north. Its position is generally identified by the rapid northward sinking of the salinity minimum associated with the Antarctic Intermediate Water (AAIW) from near the surface in the PFZ (S $ <$ 34) to depths greater than 400 m in the SAZ (S $ <$ 34.30). The property indicators within the front are S $ <$ 34.20 at Z $ <$ 300 m, $ \theta\,>$ 4-5$ ^\circ$ at 400 m, and O$ _2$ $ >$ 7 ml/l at Z $ <$ 200 m. The SAF is one of three distinct fronts in the Antarctic Circumpolar Current (ACC), the others being (to the south) the Polar Front (PF) and the Southern ACC Front (SACCF). This has also been called the sf Australasian Subantarctic Front. See Orsi et al. (1995).

Subantarctic Mode Water (SAMW)
In physical oceanography, a water mass in the Subantarctic Zone of the Southern Ocean. This is one type of Subpolar Mode Water. The SAMW is the deep surface layer of water with uniform temperature and salinity created by convective processes in the winter. It can by identified by a temperature of around -1.8$ ^\circ$ C and a salinity of around 34.4 and is separated from the overlying surface water by a halocline at around 50 m in the summer. Although it is not considered to be a water mass, it contributes to the Central Water of the southern hemisphere, and is additionally responsible for the formation of AAIW in the eastern part of the south Pacific Ocean. This has also previously been called Winter Water. See McCartney (1977), Piola and Georgi (1981) and Tomczak and Godfrey (1994).

Subantarctic Surface Water (SSW)
A water mass found in the Southern Ocean between the Subtropical Front (STF) and the Subantarctic Front (SAF) and above the salinity minimum of the Antarctic Intermediate Water (AAIW). At the surface the SSW is fresher than the surface waters of the Polar Frontal Zone (PFZ) in the Drake Passage, although by the time it reaches the Greenwich Meridian surface salinities are 0.3-0.4 higher than in the Drake Passage and more saline than those in the PFZ. Below the surface the SSW shows monotonically decreasing temperature as well as a maximum in salinity and a minimum in oxygen, both of the latter induced by the underlying AAIW. See Whitworth and Jr. (1987).

Subantarctic Upper Water (SAUW)
In physical oceanography, a water mass located in the Subantarctic Zone of the Southern Ocean. It is characterized hydrographically by temperatures ranging from 4-10$ ^\circ$ C in the winter and 4-14$ ^\circ$ C in summer, with salinities between 33.9 and 34.9 and reaching as low as 33.0 in the summer as the ice melts. See Tomczak and Godfrey (1994), p. 82.

Subantarctic Zone
The name given to the region in the Southern Ocean between the Subantarctic Front to the south and the Subtropical Front to the north. This zone is characterized by the presence of SAUW at and near the surface. The SAZ is one of four distinct surface water mass regimes in the Southern Ocean, the others being (to the south) the Polar Frontal Zone (PFZ), the Antarctic Zone (AZ) and the Continental Zone (CZ). See Tomczak and Godfrey (1994) and Orsi et al. (1995).

Subarctic Intermediate Water (SIW)
In physical oceanography, this is a water mass which originates from the Polar Front formed between the Kuroshio and the Oyashio in the western North Pacific Ocean. It is formed chiefly by the process of mixing of surface and deeper waters and subducted into the subtropical gyre, filling the northern Pacific south of 40$ ^\circ$ N from the east. This is one of the few water masses whose formation process has little to do with atmosphere-ocean interaction. It is characterized by a salinity minimum ranging from about 300-1000 m depth and a large east-west salinity gradient in the South Pacific. See Tomczak and Godfrey (1994) (p. 161) and Ahran (1990).

In physical oceanography, a process whereby Ekman pumping injects surface water into intermediate depths along isopycnal surfaces. This process is responsible for the formation of the water masses in the permanent thermocline. Although it is a permanent process, water mass formation occurs only in late autumn and winter due to variations in the seasonal thermocline. See Tomczak and Godfrey (1994).

Subduction Experiment
An experiment that took place in the subtropical North Atlantic near the eastern flank of the Bermuda/Azores atmospheric high pressure system from June 1991 to June 1993. That region is a preferred one for convergence of the wind-driven or Ekman circulation which leads to subduction, the process by which mixed layer water is injected into the main thermocline. See Spall et al. (2000).


subjective analysis
In meteorology, the name given to synoptic weather charts prepared by hand since the resulting diagnosis or analysis relied extensively on the subjective judgment of the preparer. Compare to objective analysis. See Daley (1991).

Subpolar Mode Water (SMW)
See McCartney and Talley (1982).

subsurface countercurrent (SSCC)
Another name for the Tsuchiya jets found in the equatorial Pacific Ocean.

Of the subtropics.

Subtropical Convergence
The name given by Deacon (Deacon (1933), Deacon (1937)) to the hydrographic boundary between the Southern Ocean and subtropical waters to the north. This was replaced by the term Subtropical Front (STF) in the mid-1980s.

Subtropical Countercurrent
An eastward flowing current found in the region from 20-26$ ^\circ$ N. In geostrophic current calculations these currents extend to the bottom of the thermocline and occasionally to 1500 m, while they've been identified in ship drift data with speeds reaching 0.15 m/s. They do not exist east of Hawaii and, given also the fact that they are in the middle of the subtropical gyre, are thought to be caused by a modification of the Sverdrup circulation by those islands. No satisfactory explanation has as yet been advanced. See Tomczak and Godfrey (1994) and Kubokawa and Inui (1999).

Subtropical Front (STF)
In physical oceanography, a region of pronounced meridional gradients in surface properties that serves as the boundary between the Southern Ocean and the waters of the subtropical regime to the north. This was originally called the Subtropical Convergence (DTC) by Deacon but the newer terminology arose in the mid-1980s. This is generally a subduction region for various types of Central Water.

The STF separates the Subantarctic Surface Water (SASW) to the south from the Subtropical Surface Water to the north. The surface hydrographic properties of the STF include a rapid salinity change from 35.0 to 34.5 and a strong temperature gradient (from 14-10$ ^\circ$ C in winter and 18-14$ ^\circ$ C in summer) as one crosses from north to south. At 100 m its approximate location is within a band across which temperatures increase northward from 10 to 12$ ^\circ$ C and salinities from 34.6 to 35.0, with the salinity gradient usually the more reliable indicator. The position as well as the intensity of sinking or rising motion in the STF is more variable than in any other front or divergence in the Southern Ocean. See Tomczak and Godfrey (1994), Tchernia (1980) and Orsi et al. (1995).

Subtropical Frontal Zone (STFZ)
A broad zone up to 4$ ^\circ$-5$ ^\circ$ latitude wide consisting of several cores or fronts interspersed by zones of relatively homogeneous waters. The STFZ is thought to be a more accurate desciption of what was formerly thought to be single front called the Subtropical Front, with the STFZ boundaries being the North Subtropical Front (NSTF) and the South Subtropical Front (SSTF). See Belkin and Gordon (1996).

subtropical gyre
A clockwise/counterclockwise circulation in the northern/southern hemisphere that is forced by the wind and features western intensification in the form of a western boundary current. In the northern hemisphere the gyres span the width of the oceans and extend from about 10 to 40 $ ^\circ$N with the boundary currents in the Atlantic and Pacific called, respectively, the Gulf Stream and the Kuroshio. There are analogous features in the southern hemisphere. The polar boundaries between these and the subpolar gyres coincide with the latitude at which the curl of the wind stress vanishes, the latter being largely the mechanism of causation. See Schmitz and McCartney (1993).

Subtropical Mode Water (STMW)
A type of water mass found along the equatorward side of the separated western boundary currents of each of the subtropical gyres. They are identified as a layer of reduced stratification found below the seasonal thermocline and above the main thermocline. They are formed by winter mixing and cooling, with restratification occurring in the surface layer during summer. The STMW thermostads can be traced for a considerable distance away from the formation regions following the equatorward flow of the gyre interiors.

In the North Pacific, deep convection occurs offshore of both the Kuroshio and the Kuroshio Extension in winter. Vertically homogeneous water is formed in the deep convective mixed layer which remains as a pycnostad between the seasonal and main thermoclines through the succeeding surface warming. This pycnostad is found over a much wider region in the western subtropical North Pacific than its formation area, and the water therein is the North Pacific STMW.

According to Suga and Hanawa (1995):

The Kuroshio Countercurrent composing the Kuroshio recirculation system advects STMW formed in the wintertime thick mixed layer immediately off the Kuroshio Current and the Kuroshio Extension. During the non-large-meander period, the recirculation system has a single anticyclonic gyre centered near 30$ ^\circ$N, 137$ ^\circ$E and advects STMW formed off the Kuroshio Extension, or east of 140$ ^\circ$E, to the meridian of 137$ ^\circ$E south of Honshu within a few months. Heavier STMW formed farther eat is advected along an outer path, taking several months longer. During the large-meander period, the recirculation system is separated into two anticyclonic gyres west and east of 140$ ^\circ$E, and no substantial westward advection of STMW across the 140$ ^\circ$E meridian occurs, while minor advectionof STMW along the outer path can occur. The climatological hydrography also suggests that the STMW formed in one winter will be dissipated considerably within a year or so.

In the South Pacific, the STMW thermostad is less pronounced than in either the North Pacific or North Atlantic. According to Roemmich and Cornuelle (1992), the South Pacific STMW ...

... is a thermostad, or minimum in stratification, having temperatures of about 15-19$ ^\circ$C and vertical temperature gradient less than about 2$ ^\circ$C per 100 m. Typical salinity is 35.5 psu at 16.5$ ^\circ$C. The STMW layer is formed by deep mixing and cooling in the eastward-flowing waters of the separated East Australia Current (EAC). Surface mixed layers are observed as deep as 300 m north of New Zealand in winter, in the center of a recurring anticyclonic eddy.
See Masuzawa (1969), McCartney (1982), Bingham (1992), Roemmich and Cornuelle (1992), Hanawa and Suga (1995), Suga and Hanawa (1995) and Hautala and Roemmich (1998).

Generally the part of the Earth's surface between the tropics and the temperate regions, or between about 40$ ^\circ$ N and S.

Sulawesi Sea
Part of the Australasian Mediterranean Sea centered at approximately 122$ ^\circ$ E and 3$ ^\circ$ N. It is surrounded by the Sulu Archipelago and Mindinao to the north, Kalimantan to the west, the Makassar Strait and Sulawesi to the south, and the north part of the Moluccan Sea to the west. It covers about 280,000 sq. km with the deepest part being around 6200 m just southwest of Mindanao. The entire Sulawesi is mostly a deep, flat (4600-5200 m deep) plain with steep sides.

The deep water Pacific Ocean water that passes through the northern Molucca Sea and enters the Sulawesi over a 1400 m deep sill. This water eventually passes through the Makassar Strait and on into the Flores Sea to the south. The surface temperatures range between 28$ ^\circ$ C in April and 27$ ^\circ$ C in February, and the salinities range through four patterns during the year (i.e. 31-34 from SW to NE during Dec.-Feb., 32.8-33.9 from SW to NE during Mar.-May, 34 from Jun.-Aug., and 33.5-34.1 from NW to SE during Sep.-Nov.).

The monsoon pattern dominates the wind forcing, with the winds blowing from the north to northeast during the northern winter and more weakly from the south and southwest during the summer. This creates a surface current directed from Mindanao towards the Makassar Strait during the summer. This regime is largely maintained through the winter although westward currents are additionally found along Sulawesi. See Fairbridge (1966).

Sulu Sea
A regional sea contained within the Australasian Mediterranean Sea at the southwestern edge of the Pacific Ocean. It is centered at about 120$ ^\circ$ E and 8$ ^\circ$ N and connected to the Sulawesi Sea to the southeast via many passages through the Sulu Archipelago, the Bohol Sea to the east, and the South China Sea to the west and northwest chiefly via the Mindoro, Linapacan, North Balabac, and Balabac Straits. It borders the Philippine islands of Mindanao, Negros, and Panay to the east, Mindoro and the Calamin Group to the north, Palawan to the west, and the aforementioned Sulu Archipelago to the southeast. The Malaysian portion of the island of Borneo lies to the southwest.

A squall that occurs in the Malacca Strait, blowing from between southwest and northwest. These usually occur at night and are most frequent between April and November. They are generally accompanied by thunder and lightning and torrential rain, and their arrival is accompanied by a sudden fall of temperature.

Sunda Sea
A marginal sea in the southwest Pacific Ocean. This is a name sometimes given to the combined areas of the Java Sea and the shelf sector of the South China Sea.

Sunda Shelf
One of the largest continental shelves in the world. It covers around 1,800,000 km$ ^2$, is centered around 108$ ^\circ$ E and 2$ ^\circ$ N, and occupies the regions of the Java Sea, the southern parts of the South China Sea, and the Gulf of Thailand. See Fairbridge (1966).

Acronym for Subarctic Pacific Ecosystem Research, a research program in the north Pacific. See Miller (1993).

A French project to make systematic hydrographic observations in the North Atlantic subpolar gyre. Observations are made with the merchant ships Godafoss (between Iceland and the U.S. sine 1993) and Nuka Arctica (between Denmark and Greenland since May 1997). The sampling is mostly for temperature with XBTs and for sea surface salinity.


surf beat
The rising and falling of the water level in the surf zone at intervals in the vicinity of 2 to 5 minutes, especially noticeable on a flat beach. This is caused by the pattern of incoming waves being such that groups of high waves and low waves follow each other at the same intervals. This is in turn due to the interaction of wave groups with slightly different frequencies, a process that leads to a much longer envelope or beat frequency modulated the short wavelength waves. See Wiegel (1964).

surf zone
The portion of the nearshore zone in which borelike translation waves occur following wave breaking. It extends from the inner breakers shoreward to the swash zone. See Komar (1976).

surface energy balance
The balance of energy terms at the ocean surface in a climate model. The terms are the absorbed solar flux (S), the downward infrared flux (Sd), the upward infrared flux (Su), the sensible heat flux (H), and the latent heat flux (LE). The balance can be expressed as

   S + Sd - Su - H - HE = 0$\displaystyle .

surface renewal theory
A method for evaluating turbulent fluxes at the ocean surface. See Clayson et al. (1996).

surface Reynolds number
See Kagan (1995).

surface scattering layer
A group of marine organisms in the surface layers of the ocean which scatters sound. The layer may extend from the surface to depths as great as 600 feet, and several layers or patches may comprise the layer. There are also shallow and deep scattering layers.

surface tension
More later.

A French project started in the austral summer of 1992/1993 for monitoring climate variability at high latitudes. The objective of the program is to monitor the seasonal and interannual changes in upper ocean thermal content and salinity, as well as changes in the position, structure and transport of the polar fronts between Tasmania and Antarctica. SURVOSTRAL uses the French Antarctic supply ship Astrolabe to make measurements between Hobart, Tasmania and the French base Durmont D'Urville. Sampling is performed with XBTs and XCTDs to obtain vertical profiles of temperature and salinity, and a thermosalinograph is used to obtain continuous measurements of surface salinity and temperature.


Abbreviation for Subarctic Upper Water.

Sverdrup, Harald Ulrik (1888-1957)
Sverdrup started his scientific career by enrolling as a student in ``physical oceanography and astronomy'' at the University of Oslo, where his early interests leaned towards the latter. This changed when he received an assistantship to study under Professor V. Bjerknes, under whom he published twenty papers and a dissertation entitled Der nordatlantische Passat (in which he calculated energy and momentum budgets for the North Atlantic trade winds) over the next six years.

He took charge of scientific work on Roald Amundsen's North Polar expedition at the age of 29 in 1918. He did not return until late in 1925 as the expedition ship Maud attempted to duplicate the voyage (and ice drift) of the Fram. At one point during the seven years of this expedition Sverdrup left the ship to spend eight months with the nomadic Chukchi tribe of northeastern Siberia, an experience he later recounted in a book (which has never been translated into English). The collected observations of the expedition were a notable achievement, with Sverdrup's most significant contribution being a paper entitled ``Dynamics of tides on the North Siberian Shelf.''

Sverdrup succeeded V. Bjerknes as the Chair of Meteorology at the Geophysical Institute in Bergen, Norway upon his return, and he additionally became a research professor at the Christian Michelson Institute in Bergen in 1931. The ten years following his return from the Maud expedition were the most productive of his career, with his accomplishments including publishing over fifty papers on results from the expedition, spending two half-year periods in Washington, D.C. to help analyze the results from a cruise of the Carnegie, taking charge of the scientific work on the Wilkins Ellsworth North Polar Expedition aboard the submarine Nautilus in 1931, and spending two months in the snow fields of Spitzbergen which resulted in the first quantitative heat budget of glaciers.

In 1936 he accepted the Directorship of the Scripps Institution of Oceanography in La Jolla, California, leaving the Michelsen Institute for three years, although the war resulted in his not returning to Norway until 1948. At Scripps Sverdrup initiated the Marine Life Research Program (still ongoing today), organized the first systematic course in oceanography given in the United States, and taught and collaborated such future reknowned scientists as Gifford Ewing, Donald Pritchard, Roger Revelle, Robert Reid and Walter Munk. He spent a great deal of time and effort during the pre-war years collaborating with Martin Johnson and Richard Fleming to write the classic text The Oceans, with his chapter on the water masses and currents of the oceans still one of the best reviews of the subject available.

He returned to Norway in 1948 at the age of sixty and retired from research, dividing his time variously as Director of the Norsk Polar Institut, the President of the ICES, Prorector and Director of the Summer School for foreign students at the University of Oslo, and as Chairman of a committee for reorganizing the Norwegian educational system. He continued in these activities until a stroke weakened him and led to his death in 1957.


A unit of transport used in oceanography equivalent to $ 10^6$ m$ ^3$s$ ^{-1}$ and abbreviated as Sv.

Sverdrup balance
A vorticity balance in which meridional advection in the presence of the planetary vorticity gradient is balanced by the stretching of fluid columns. It is most simply stated as

$\displaystyle \beta v\,=\,f{{\partial w}\over{\partial z}}$

where $ \beta$ is the meridional gradient of the Coriolis parameter $ f$, $ v$ the meridional velocity, and $ w$ the vertical velocity. This indicates that the stiffness imparted to a large scale fluid by planetary rotation leads to the conservation of the separation of marked fluid surfaces measured parallel with the rotation vector.

Sverdrup transport
The net meridional flow of mass in the interior of the ocean gyres away from the lateral boundaries.

Abbreviation for Surface Velocity Program, a WOCE project.

Swallow float
See Swallow (1955).

swamp ocean
The simplest ocean model used in coupled model simulations. SSTs are computed but from surface energy balance (local effects) only, i.e. there is no accounting for heat storage (temporal) or ocean current (nonlocal) effects. Only mean annual forcing can be applied when a swamp ocean is used since the lack of the capability to store heat in the oceans would allow sea ice to freeze into the mid-latitudes in the winter hemisphere. On the plus side, the dominant equilibration time is that of the atmosphere since the ocean surface response time is almost instantaneous.

Acronym for Surface WAve Dynamics Experiment, an experiment performed in the fall of 1990 off the coast of Virginia which was primarily concerned with the evolution of the directional wave spectrum, wind forcing and wave dissipation, the effect of waves on air-sea coupling mechanisms, and the microwave radar response of the ocean surface. The scientific goals were to understand the dynamics of the evolution of the wave field in the open ocean; to determine the effect of waves on the air-sea transfers of momentum, heat and mass; to explore the response of the upper mixed layer to atmospheric forcing; to investigate the effect of waves on the response of various airborne microwave systems; and to improve numerical wave modeling. See Weller et al. (1991) and Willemsen (1995).

1. Acronym for Sea Wave Modeling Project. See group (1985). 2. Acronym for Southwest Area Monsoon Project.

Acronym for Simulating WAves Nearshore, a third-generation wave model that computes random, short-crested, wind-generated waves in coastal regions and inland waters. The physics accounted for in the SWAN model includes: A copy of the FORTRAN code is available upon registration. See Booij et al. (1999).


Acronym for Surface WAve Processes Program, an experiment conducted off the coast of California in 1990 and concerned with wave breaking and the interaction between surface waves and upper ocean boundary layer dynamics. The scientific goals were to improve the understanding of processes involved in wave breaking (e.g. what determines the occurrence of breaking in space and time, the processes of bubble and fluid injection, the generation of turbulence in the upper layer of the ocean by waves) and in determining the structure of the upper ocean (e.g. the role of surface waves in air-sea transfers and in mixed layer dynamics, with particular emphasis on the structure and dynamics of Langmuir circulation. See Weller et al. (1991).

Acronym for Shallow Water Acoustic Random Media 1995 experiment, an ONR sponsored joint operation between the NRL Acoustic Signal Processing Branch and Woods Hole. The goal is to explore the effects on acoustic propagation of random ocean environments in the water column and the bottom sediments. The experiment was performed on the continental shelf about 100 miles of the coast of New Jersey in the Hudson Canyon area in July-August 1995, and deployed a significant number of acoustic and oceanographic equipment to characterize the acoustic propagation environment. See apel:1997.


swash zone
The portion of the nearshore zone in which the beach face is alternately covered by the uprush of wave swash and exposed by the backwash. See Komar (1976).

Swedish Deep Sea Expedition
A research cruise taking place from 1947-1948 aboard the vessel ``Albatross,'' The expedition was headed by Hans Pettersson who also edited the ten-volume series of research reports published starting in 1957. The contents of the reports were:
  1. The ship, its equipment, and the voyage
  2. Zoology
  3. Physics and chemistry
  4. Bottom investigations
  5. Sediment cores from the East Pacific
  6. Sediment cores from the West Pacific
  7. Sediment cores from the North Atlantic Ocean
  8. Sediment cores from the Mediterranean Sea and the Red Sea
  9. Sediment cores from the Indian Ocean
  10. Special investigations
See Guberlet (1964).

Acronym for Shallow Water Intercomparison of wave prediction Models, and extension of the SWAMP project to shallow water. See group (1985).

Acronym for Shallow Water Integrated Mapping System, an instrument developed by the APL.

Acronym for Surface Waves Investigation and Monitoring from SATellite, a project to design, develop and use systems to measure directional wave spectra from satellites using the real-aperture technique rather than the traditional SAR technique. The system is a dual-beam radar (capable of nadir viewing and off-nadir viewing at an angle of 10$ ^\circ$) operating in the K$ _\mu$ frequency band (13.565 GHz) and flying on a polar-orbiting satellite at an altitude of 450-600 km. The nadir beam is operated to measure significant wave height and wind speed in the same way as spaceborne altimeters. An innovative feature is its operation in off-nadir viewing mode by tilting the radar beam to measure wave spectral characteristics. The principle is based on measuring modulations of the radar backscatter coefficient inside the swatch covered by the tilted beam. The tilted beam is rotated to perform a conical scan around the vertical axis to acquire measurements in all directions of wave propagation. SWIMSAT should be capable of measuring wave spectral properties under wind-sea (provided the dominant wavelength is greater than about 70 m) and swell conditions (provided the significant wave height is greater than 1.5-2 m, depending on wind). See Hauser et al. (2001).

Acronym for Slope Water Oceanic eDDY, a term coined in Pingree and LeCann (1992) to describe jet-like extensions of the slope current off northern Spain and France in the southern Bay of Biscay in the winter that develop into anticyclonic eddies with an upper core of slope water. A typical SWODDY has a lifetime of about a year and, if not trapped by topography, propagates or advects westwards out of the Bay of Biscay at typical speeds of about 2 cm s$ ^{-1}$.

Abbreviation for southern warm tongue, a tongue of relatively warm water located at the eastern boundary of the WPWP. It is located at around 10 $ ^\circ$ S. See Ho et al. (1995).

An experiment (also called ERS-SYMPLEX) carried out in the Sicily Channel during April-May 1996 to compare sea level anomalies obtained from ERS-1/2 and TOPEX/POSEIDON altimeters with in situ data. A dense network (about 5 km spacing) of XBT and CTD casts were made along all ERS-1/2 and TOPEX/POSEIDON tracks at the same time of each satellite pass.


Acronym for the SYNoptic Ocean Prediction experiment, an observational and modeling experiment designed to understand the physics governing large amplitude meandering of the Gulf Stream and the shedding and interactions of rings east of Cape Hatteras to the Grand Banks. The moored instrument program consisted of four arrays: Observations were made between 1987 and 1990.

A significant finding of SYNOP was the presence of strong, deep cyclones and anticyclones beneath the Gulf Stream, with the spin-up of the deep flow field occuring during the passage of the steep meander crests and troughs of the Stream. Velocities at 3500 m were observed to be as high as 35-40 cm s$ ^{-1}$ during the strong events. See Tracey and Watts (1991).


Descriptive of data simultaneously obtained over a large area.

synoptic mean circulation
In oceanography, the time-averaged flow field obtained in a coordinate system whose axes are parallel and perpendicular to the instantaneous axis of a particular strong current such as the Gulf Stream. This coordinate system can and does change with time. Compare to Eulerian mean circulation. See Schmitz and McCartney (1993).

systematic errors
Stable errors in model simulations that result from model deficiencies in the component (e.g ocean and atmosphere) models alone, additive errors from the component models after they are coupled, or errors that are produced by the coupled interactions between imperfect component models. Sometimes called climate drift. See Meehl (1992).

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