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Sa-Sm

SAA
Abbrevation for Satellite Active Archive, a digital library of real-time and historical satellite data from NOAA's POES. SAA allows users to search inventories of satellite data, preview representative Earth images of that data, and to download the data for further processing and analysis.

[http://www.saa.noaa.gov/]

SAARI
Acronym for the South Atlantic Accelerated Research Initiative, an ONR research program primarily directed toward improvement of the description of the subtropical South Atlantic. It focused on the poleward corners of the subtropical gyre, i.e. the separation of the Brazil Current and its confluence with the Malvinas or Falkland Current in the southwest, and the Agulhas Retroflection and Benguela Current in the southeast. See Gordon (1988).

SABRE
Acronym for South Atlantic Bight Recruitment Experiment, a NOAA program to stud the birthdate history of survivors (larvae, late larvae, and juveniles) to determine which life history phase or passage (spawning, transport across the shelf, inlet ingress, estuarine development, inlet egress) regulates recruitment variability in annual cohorts of transgressive species like Atlantic menhaden.

[http://www.ccpo.odu.edu/~wheless/sabre.html]

SABSOON
Acronym for South Atlantic Bight Synoptic Offshore Observational Network, a NOPP funded program to develop a real-time observational network on the continental shelf offshore of South Carolina and Georgia. The network consists of eight large offshore platforms - currently operated by the U.S. Navy for flight training - being instrumented to provide a range of oceanographic and meteorological observations on a continuous, real-time basis. The grid covers an area of 155 km by 50 km and a depth range from 25 to 45 m, with an existing communcations system allowing high bandwidth, real-time data transmission to shore.

[http://www.skio.peachnet.edu/projects/sabsoon.html/]

SAC
Acronym for Shipboard ADCP Center, now renamed to JASADCP.

SACCF
Abbreviation for the Southern ACC Front.

SADCO
Acronym for the South African Data Centre for Oceanography, a center that stores, retrieves and manipulates multi-disciplinary marine information from the areas around Southern Africa.

[http://fred.csir.co.za/ematek/sadco/sadco.html]

S-ADCP
Abbreviation for Salinity-ADCP.

SAF
Abbreviation for Subantarctic Front.

SAFDE
Acronym for the Sub-Antarctic Flux and Dynamics Experiment, a program designed to collect observations of the ACC south of Tasmania that would permit direct evaluation of the momentum, energy and vorticity budgets. The experiment lasted two years - from April 1995 to March 1997 - and collected multi-year observations of currents and temperatures in both a small current meter mooring array with a diameter of about 70 km, and along a SSW-NNE section perpendicular to the expected mean axis of the ACC at the Subantarctic Front. The measured variables were found to be coherent horizontally and vertically in broad, sub-inertial frequency bands, a rarity with such oceanic measurements.

The center of the SAFDE array consisted of nine subsurface, nearly full depth moorings deployed as a local dynamics array (LDA), of which four were fully and three partially recovered. The array also included a suite of 17 (15 recovered) horizontal electrometers (HEM) and 18 (all recovered) inverted echo sounders (IES) to obtain time series of the vertically averaged horizontal water velocity, the temperature structure, and the dynamic height structure. The HEMs measure the horizontal electic fields which are theoretically related to the conductivity-weighted, vertically-averaged horizontal water velocity Chave and Luther (1990).

[http://www.soest.hawaii.edu/~dluther/SAFDE/]

SAHFOS
Abbreviation for Sir Alister Hardy Foundation for Ocean Science, whose mission is to further the understanding of marine pelagic ecosystem processes through: It was originally established in 1990 to operate the CPR survey, a program started in 1931 by Alister Hardy.

[http://www.npm.ac.uk/sahfos/sahfos.html]

saline contraction coefficient
A quantity arising from taking derivatives of the density in the $ (p, \theta , S)$ representation of the equation of state. This is defined in seawater as:

$\displaystyle \beta\,=\,{1\over\rho}\, {{\left.{{\partial\rho}\over{\partial S}... ... \,+\, {{\left.\alpha{{\partial\theta}\over{\partial S}}\right\vert}_{T,\rho}} $

where $ \rho$ is the in situ density, $ \theta$ is the potential temperature, $ S$ is the salinity, and $ T$ is the temperature. In practice, $ {{\partial\rho}\over{\partial S}}$ can be obtained from the International Equation of State of seawater, and $ {{\partial\theta}\over{\partial S}}$ from Bryden (1973).

McDougall (1987b) gives a polynomial expression for $ \beta$:

$\displaystyle \beta\,$ $\displaystyle =$ $\displaystyle \,0.785567 \times {10^{-3}}\,-\,0.301985 \times {10^{-5}}\theta\,+\, 0.555579 \times {10^{-7}} {\theta^2}$  
  $\displaystyle -$ $\displaystyle \,0.415613 \times {10^{-9}}{\theta^3} \,+\,(S\,-\,35.0)[-0.356603 \times {10^{-6}} \,+\,0.788212 \times {10^{-8}}\theta$  
  $\displaystyle +$ $\displaystyle \,0.408195 \times {10^{-10}}p \,-\,0.602281 \times {10^{-15}}{p^2} ] \,+\,{{(S\,-\,35.0)}^2}[+0.515032 \times {10^{-8}}]$  
  $\displaystyle +$ $\displaystyle \,p [-0.121555 \times {10^{-7}} \,+\,0.192867 \times {10^{-9}}\theta \,-\,0.213127 \times {10^{-11}}{\theta^2}]$  
  $\displaystyle +$ $\displaystyle \,{p^2}[+0.176621 \times {10^{-12}} \,-\,0.175379 \times {10^{-14}}\theta ] \,+\,{p^3}[+0.121551 \times {10^{-17}}]$  

The units of $ \beta$ are psu$ ^{-1}$ and the rms error of this fit is $ 0.163 \times {10^{-6}}$ psu$ ^{-1}$. A test value is $ 0.72088 \times {10^{-3}}$ psu$ ^{-1}$ at $ S$ = 40 psu, $ \theta$ = 10.0$ ^\circ$C and $ p$ = 4000.0 db. See McDougall et al. (1987) and the related thermal expansion coefficient and adiabatic compressibility.

salinity
An oceanographic concept conceived to provide a measure of the mass of salt per unit mass of seawater. The first systematic attempt to define this was made by a commission appointed by the International Council for the Exploration of the Sea in 1899 and chaired by Knudsen. Attempts to measure salt content by drying samples were accompanied by losses of volatile compounds along with the water, and the hygroscopic nature of the residue also served to complicate matters. A dry residue method where the sample was evaporated and dried to a stable weight at 480$ ^\circ$ C after processing with hydrochloric acid was offered as an alternative method. This led to the definition of the salinity as ``the total amount of solid material in grams contained in one kilogram of seawater when all the carbonate has been converted to oxide, all the bromine and iodine replaced by chlorine, and all the organic material oxidized.''

When this dry residue method also provided practical difficulties aboard ship the commission defined a chlorinity that could be determined via a volumetric titration using silver nitrate. This measurement could be combined with the assumption of constant ionic ratios in seawater to obtain a measure of the salinity, with the relationship between the two quantities being defined as

S$\displaystyle ({{^\circ}/{_{\circ\circ}}})\,=\,0.03\,+\,1.805\,$   Cl$\displaystyle ({{~\circ}/{_{\circ\circ}}}).$

A small adjustment was made in the definition of chlorinity in the late 1920s, but it remained basically the same until the development of reliable and precise electronic instrumentation in the 1950s led to a qualitative redefinition of the chlorinity, and therefore the salinity, in terms of measurements of the electrical conductivity of a water sample. This led to the creation and publication of the the International Oceanographic Tables giving salinity as a function of conductivity ratio above 10$ ^\circ$. These tables were adequate for the laboratory determination of salinity, but could not be used with in-situ salinometers since most such measurements were made at temperatures below 10$ ^\circ$ C. A separate set of tables were developed in the mid-1960s that covered the range 0-30$ ^\circ$ C, although this led to discrepancies between in-situ and bench measurements of salinities and many separate attempts to patch together the two data sets. This in turn led to confusion in the comparison of salinity data amongst the major oceanographic institutes.

A solution was found in 1978 in the form of a new definition called the Practical Salinity Scale (PSS-78) where the practical salinity is defined in terms of the ratio of the electrical conductivity of a seawater sample at atmospheric pressure at 15$ ^\circ$C to that of KCl solution containing 32.4356 g of KCl in a mass of 1 kg of solution at the same pressure and temperature. See Lewis (1980) and Lewis and Perkin (1978).

SALR
Abbreviation for saturated adiabatic lapse rate.

salt fingering
See double diffusive instability.

salt fountain
A hypothesized perpetual fountain where a long, narrow heat-conducting pipe inserted vertically through a region of ocean where warm, salty water overlies colder, fresher (and therefore denser) water. Water pumped upwards through the pipe would reach the same temperature as the surroundings at the same level (by conduction of heat through the wall of the pipe), while it remained fresher and therefore lighter. A fountain started thusly (in either direction) will continue to flow so long as there is a vertical gradient of salinity to supply potential energy. The idea was first advanced by Stommel et al. (1956) and is discussed in Turner (1973).

Samar Sea
A small sea contained within the Visayan Islands that comprise the central portion of the Philippines. It is centered at approximately 124$ ^\circ$ E and 12$ ^\circ$ N and connected to the Visayan Sea to the southwest, the Philippine Sea to the northeast via the San Bernardino Strait, and the Sibuyan Sea to the northwest.

SAMBA
Acronym for Sub-Antarctic Motions in the Brazil Basin, a component of the WOCE float program aimed at describing the absolute general circulation of the Antarctic Intermediate Water (AAIW) as it spreads northward at about 800 m depth in the Brazil Basin. During the SAMBA experiment a total of 100 MARVOR floats were launched between February 1994 and December 1998 at 800 $ \pm$ 30 dbar in the Brazil Basin.

[http://www.ifremer.fr/lpo/samba/]

sample
In signal processing, to pick out values from an analog signal, usually at regular intervals, to create a corresponding digital signal.

SAMW
Abbreviation for Subantarctic Mode Water.

sand
More later.

Sandstrom's Theorem
An ocean circulation theorem that states that a closed steady circulation can only be maintained in the ocean if the heat source is situated at a lower level than the cold source. Sandstrom considered to momentum balance of the steady circulation of the oceans, and concluded that, to overcome friction, there should be a net input of mechanical energy over each closed streamline, i.e.

$\displaystyle w\,=\,-{\int_s}\,\nu\,dp\,>\,0$ (15)

where $ \nu$ and $ p$ are the specific volume and pressure, and the integration is taken along closed streamlines $ s$. He modeled the oceanic circulation in terms of a heat engine by assuming four idealized stages within each cycle of the oceanic heat engine: Within this cycle, the net amount of work would be negative if the system is heated under low pressure, and cooled under high pressure. Positive work is only possible when heating takes place at a higher pressure and cooling at a lower pressure.

The application of this theorem to the ocean was a vexing issue for years, as is summarized by Huang (1999):

However, the application of Sandstrom's theorem to the oceanic circulation does pose a serious puzzle. The ocean is mostly heated and cooled from the upper surface. Due to thermal expansion, the sea surface level at low latitudes where heating takes place is about one meter higher than the sea level at high latitudes where cooling takes place. Therefore, according the Sandstrom's theorem, there should be no convectively driven circulation.'
According to Huang (1999), the resolution lies in Sandstrom's original model excluding diffusion and friction. He used an idealized loop model of the oceanic thermohaline circulation that included mixing to discover that the circulation can be classified into two types, depending on the vertical locations of the heating and cooling sources. An unexpected result from the same study was that geothermal heating can contribute a substantial portion of the energy for the mixing of deep water. Another interesting result was finding the diapycnal mixing rate due to tidal energy and geothermal heat flux to be about 0.22-0.28 $ \times{10^{-4}} {m^2}{s^{-1}}$. See Defant (1961) and Huang (1999).

San Matías Gulf
A gulf located at around 42$ ^\circ$S along the Argentine coast of eastern South America. According to Piccolo (1998):
It has a significant interaction with the adjacent shelf. A sill at a depth of 74 m is found at the entrance of the gulf. It is a basin with 200-m depths at its center. Unfortunately, very few studies were performed to learn its circulation and dynamics, and therefore only a brief review is presented here. The temperature structure of the gulf in winter reveals a well-mixed water column indicative of deep-reaching and bottom water ventilation. Near 41$ ^\circ$50'S a relatively intense thermohaline front is found. Relatively cold fresh waters similar to the open shelf waters are found south of the front, while warm salty waters typical of the gulf are found north of the front. This front is produced by tidal mixing. The gulf circulation is dominated by a cyclonic gyre about 70 km in diameter located north of the front. South of the front the thermocline structure is complex and not well resolved by the observations. The San José Gulf communicates with the San Matías Gulf, and there is a strong water interaction between both coastal bodies.
See Piccolo (1998).

Santa Barbara Channel
See Harms and Winant (1998).

SAR
Abbreviation for Synthetic Aperture Radar, a side-looking imaging radar system that uses the Doppler effect to sharpen the effective resolution in the cross-track direction. Basically, high resolution is achieved by measuring the travel time of short emitted pulses, while comparable resolution is achieved in the azimuthal (flight) direction by collecting the amplitude and phase histories of the returned signals from a large number of individual pulses to reconstruct the signal of a large virtual antenna. An SAR on a polar orbiting satellite at 800 km can typically scan a swath about 100 km wide with a resolution of 20 m by 20 m at incidence angles of 20 to 25$ ^\circ$.

Incident electromagnetic microwaves resonantly interact with short ocean ripple waves and backscatter via the mechanism of Bragg scattering. An SAR system is capable of detecting a variety of large scale oceanic phenomena which modulate the short (Bragg) ocean ripple spectrum, e.g. fronts, internal waves, natural surface films or man-made slicks, bottom topography, and ocean gravity waves. These modulations may be of either the tilt moduluation or hydrodynamic modulation varieties. See Komen et al. (1996).

Sargasso Sea
A clockwise-circulating region in the North Atlantic Ocean bound by the Gulf Stream on the west and north and less definitely to the east at 40$ ^\circ$ W near the Canary Current and to the south at 20$ ^\circ$ N near the North Equatorial Drift Current. It is so named because of the indigenous, yellow-brown seaweed called Sargassum that is found there in great abundance. The Sargasso is part of the subtropical gyre circulation system in the North Atlantic and comprises a large part of its interior circulation, covering an area of around 5.2 million square kilometers.

A large volume of a type of mode water known as 18$ ^\circ$ water forms in the Sargasso in the winter and is seen as a thick layer of water at that temperature between 250 and 400 m depth. In the summer an excess of evaporation over precipitation results in a thick (nearly 900 m deep near the center) lens of water warmer and more saline than surrounding waters. The anticyclonic sense of the circulation causes this water to pile up such that it is almost a meter higher than the sea level along the eastern U.S. coast. This water lens also serves to inhibit the upwelling of nutrient-rich, colder water which results in a sparsity of marine life in the region. It is has been called the clearest, purest and biologically poorest ocean water ever studied.

The northwestern part of the Sargasso is a region of recirculation for the Gulf Stream. This recirculation region is dominated by cold core eddies pinched off from the Gulf Stream, with as many as 10 clearly identifiable rings found there at any one time. This makes this northwestern region one of the most energetic in the world ocean.

Sargasso Sea Water (SSW)
See 18$ ^\circ$ Water.

Sargassum
The name given to about eight species of seaweed that float in clumps and long windrows in the Sargasso Sea. It was so named by Portuguese sailors who followed the voyages of Columbus through the region and noticed the resemblance of the small air bladders that allow Sargassum to float to a type of grape called Salgazo.

SASS
Acronym for the SEASAT-A Scatterometer System, an active backscatter scatterometer operating at a frequency of 13.0 GHz which produced earth locatino and time tagged backscatter coefficients, surface wind stress, and surface wind vectors (with a 180 degree directional ambiguity).

satellite altimetry
See Fu. and Cazanave (2001).

satellite oceanography
More later.

saturated adiabatic lapse rate
The temperature lapse rate of air which is undergoing a reversible natural adiabatic process. Abbreviated SALR.

saturated humidity mixing ratio
The humidity mixing ratio of air which is saturated at a specified temperature and pressure, with saturation defined with reference to either liquid water or ice.

saturation mixing ratio
An atmospheric quantity given by

$\displaystyle {m_s}\,=\,{ {0.622 {e_s}} \over {p\,-\,{e_s}} }$

where $ {m_s}$ is the ratio, $ {e_s}$ the saturation vapor pressure and $ p$ the atmosphere pressure.

saturation vapor pressure
Usually measured with respect to water, this is the maximum water vapor pressure that can occur when the water vapor is in contact with a free water surface at a particular temperature. It is the water vapor pressure that exists when effective evaporation ceases.

SAUW
Abbreviation for Subantarctic Upper Water.

SAVE
Acronym for South Atlantic Ventilation Experiment, an experiment taking place from 1987-1989.

Savonius rotor
A rotor originally developed for power generation (i.e. it's a propellor in reverse that spins when placed in moving water) that has been extensively used as a sensor on various ocean current meters. Its advantages are that it is rugged, omni-directional and linear in steady flow, but its response to time-varying flow and susceptibility to contamination by vertical flows make it unsuitable for measurements near the surface where wave action creates both time-varying and vertical flow fields. See Heinmuller (1983).

Savu Sea
See Sawu Sea.

Sawu Sea
One of the several connected seas that comprise the Australasian Mediterranean Sea. This is centered at approximately 123$ ^\circ$ E and 9$ ^\circ$ S and is situated between Timor to the south and east, Sumba to the south and west, and Flores to the north. The basin is mostly greater than 1500 m deep and reaches depths greater than 3000 m over most of its northern and eastern parts.

SAXON-FPN
Abbreviation for Synthetic Aperture Radar and X Band Ocean Nonlinearities-Forschungsplatform Nordsee program, a 3-year effort to investigate radar backscatter from the ocean and synthetic aperture radar (SAR) imagery of the ocean. A secondary objective was to explore the relationship between acoustic and microwave scattering from the ocean surface. This joint U.S./Federal Republic of Germany program consisted of Phase I, a major field experiment in the North Sea on and around the German Forschungsplatform Nordsee during November 1990, Phase II, a second and smaller field experiment on the same platform in November 1991, and a series of four data analysis workshops. See Plant and Alpers (1994).

SAZ
Abbreviation for Subantarctic Zone.

scale depth
A means of characterizing a (oceanic or atmospheric) density field. It is defined by $ H\,=\,{c^2}/g$ where $ c$ is the speed of sound and $ g$ gravitational acceleration. In the ocean this is on the order of 200 km. The largeness of this in comparison to the water depth (5 km) is one of the key assumptions in the Boussinesq approximation.

scale height
In the atmosphere, the height at which the pressure has fallen to $ e^{-1}$ (i.e. the e-folding scale) of its value at the surface. This occurs at about 370 mb which, for a temperature of 250 K, is about 7.4 km.

scattering
The process by which some of a stream of radiation is dispersed to travel in directions other than that which from it was incident by particles suspended in the medium through which it is travelling.

scatterometer
A high-frequency radar instrument that transmits pulses of energy towards the ocean and measures the backscatter from the ocean surface. It detects wind speed and direction over the oceans by analyzing the backscatter from the small wind-induced ripples on the surface of the water. See the NASA JPL scatterometer site.

SCAVE
Acronym for the Sound Channel Axis Velocity Experiment, where SOFAR explosive charges were fired at the depth of the sound axis off Antigua and the resulting signals received and processed at Eleuthera and Bermuda. In this experiment, taking place in 1961, travel times were ascertained to within 30 ms with rms variations estimated at at 200 ms over a period of 27 months with time scales of a few months. The variations were most likely caused by the mesoscale variability that characterizes this region. See Munk et al. (1995).

SCAWVEX
Acronym for Surface Current and Wave Variability Experiment, an EC MAST project whose primary objective is to measure the spatial and temporal variability of waves and currents in coastal regions using the full range of state of the art measurement techniques and models. The measurement systems used in this experiment include HF radar, synthetic aperture radar (SAR), satellite altimetry, accelerometers, ADCP, current meters, pressure cells, and X-band ground-based radar since one of the primary goals is the intercomparison of these techniques.

[http://www.shef.ac.uk/~sceos/environmental/scawvex/home.html]

Schlutsky-Yule effect
A consequence of smoothing a time series with a low-pass filter. In a relatively short time series, even purely random fluctuations can give the impression of there being significant quasi-cyclic fluctuations present if they are smoothed by some sort of running mean. This is name for two statisticians who demonstrated in 1927 that some trade cycles that had been apparently discovered in some 19th century data could be reproduced from a series of random numbers. See Burroughs (1992), p. 20.

Schmidt number
A nondimensional number that relates the competing effects of gas diffusion and fluid viscosity on the piston velocity, a key variable in measuring gas transfer across the air-sea interface. The Schmidt number is given by

$\displaystyle Sc\,=\,{\nu\over D}$

where $ \nu$ is the kinematic viscosity and $ D$ the molecular diffusivity of gas in sea water. See Najjar (1991).

SCICEX
A 5-year program (1995-1999) in which the U.S. Navy made available a Sturgeon-class, nuclear powered attack submarine for unclassified science cruises in the Arctic Ocean. A test cruise in 1993 started a collaboration between civilian scientists and Navy personnel wherein a variety of information on the geology, physics, chemistry and biology of the Arctic was gathered. The 100,000 miles of shiptrack traveled during the program allowed data to be gathered from regions that have never before (at least officially) been visited.

[http://www.ldeo.columbia.edu/SCICEX/]
[http://psc.apl.washington.edu/scicex/scicex2000.html]

scirocco
A warm, southerly wind in the Mediterranean region. Near the north coast of Africa the wind is hot and dry and often carries much dust. After crossing the Mediterranean, the scirocco reaches the European coast as a moist wind and is often associated with low stratus.

SCOPE
Acronym for San Clemente Ocean Probing Experiment, a NOAA ETL program conducted in September 1993. It was an experiment to study the effects of the atmosphere on active and passive microwave remote sensing measurements of the ocean surface.

[http://www6.etl.noaa.gov/projects/scope.html]

SCOPEX
The South Channel Ocean Productivity Experiment was a multidisciplinary study of a whale-zooplankton predator-prey system in the southwestern Gulf of Maine that focused on the oceanographic factors responsible for the development of dense patches of the copepod Calanus finmarchicus, the major prey resource for right whales. See Kenney and Wishner (1995).

SCOR
Acronym for Scientific Committee on Oceanic Research, the oldest interdisciplinary committee of the ICSU, established in 1957 for the promotion and coordination of international oceanographic activities. SCOR doesn't directly fund research although its scientific groups organize international meetings, publich scientific literature, and propose and plan large international collaborative efforts such as JGOFS and GLOBEC. SCOR consists of its members - the national committees for oceanic research of its 39 member countries, each represented by three individual oceanographers. An Executive Committee, elected at biennial General Meetings, also includes ex officio members from allied disciplinary organizations including IAPSO, IABO, CMG, and IAMAS. A SCOR Secretariat located at Johns Hopkins University in Baltimore, Maryland provides routine administrative support for SCOR activities as well as publications such as the JGOFS and GLOBEC Report Series, the annual SCOR Procedings, and the directory or SCOR Handbook.

There are two major categories under which SCOR work can be subsumed. The first is the traditional mechanism of the SCOR working group wherein small international groups address narrowly focused scientific problems that will benefit from such a cooperative effort. These groups generally have about ten members, meet two or three times, and produce either a book or special journal volume or organize an international conference or workshop to complete their efforts. They are estblished on the basis of proposals received from national committees, other organizations, or even individual scientists. While the working group exists for short term (four years or less) projects, longer term and more complex activities are the province of the second mechanism, i.e. scientific committees.

The names of the currently (1998) constituted SCOR working groups (along with their respective numbers) are:

[http://www.jhu.edu/~scor/]

Scorpio Expedition
A name of a 1973 expedition, led by Henry Stommel, to perform trans-Pacific hydrographic sections at 28 and 43$ ^\circ$ S. See Stommel et al. (1973).

Scotia Front (SF)
A front located north of the Weddell-Scotia Confluence which marks the boundary between the Weddell and Scotia Seas in the Southern Ocean. The SF is a distinct subsurface front marked by a maximum thermal gradient in the maximum temperature core layer (200-700 m) of the Circumpolar Deep Water (CDW). Crossing the SF from north to south, the temperature maximum decreases from 1.5$ ^\circ$-2.0$ ^\circ$ C to below 0.5$ ^\circ$, with the CDW salinity maximum in the 800-1200 m layer similarly decreasing southward across the SF from 34.70-34.72 to 34.67-34.68. In the minimum temperature layer, the SF appears as a thermal front across which the minimum temperature decreases southward from 0$ ^\circ$-0.5$ ^\circ$ C to below -1.0$ ^\circ$ C. There is usually no distinct sign of the SF in the surface layer. The 1$ ^\circ$ isotherm in the 300-500 m layer is considered a good single indicator of the SF axis. See Belkin and Gordon (1996).

Scotia Ridge
A ridge connecting South American and Antarctica located at about 70$ ^\circ$ W in the Southern Ocean that, along with the narrowing of the Drake Passage 2000 km to the west, impedes the flow of the Antarctic Circumpolar Current (ACC). It is generally less than 2000 m deep with some openings at the 3000 m level. After the ACC accelerates to squeeze through the Drake Passage it hits to Ridge and an increased speed and shifts northward.

Scotia Sea
More later.

SCSMEX
Abbreviation for South China Sea Monsoon Experiment, a large-scale experiment to study the water and energy cycles of the Asian monsoon regions. The goal is to provide a better understanding of the key physical processes for the onset, maintenance and variability of the Southeast Asian monsoon.

[http://ncc.cma.gov.cn/scsmex/html/scsmex_e.htm]
[http://www.bom.gov.au/bmrc/wefor/research/scsmex.htm]
[http://www.siesip.gmu.edu/Science/sci_scs.html]

sea breeze
A wind blowing from the ocean towards land caused by the effects of differential heating. In the summer when the land surface is warmer than the ocean, the air over the land heats up more than over the ocean, expands and becomes less dense, and rises. This rising air is replaced, due to the constraints of continuity, with moisture-rich air from over the oceans.

Sea Grant
The idea of a Sea Grant College Program was first suggested by Athelstan Spilhaus at a meeting of the American Fisheries Society in 1963. He predicted the proposed sea-grant colleges would spur advancements in the ocean sciences that would be ``modernized parallels of the great developments in agriculture and the mechanical arts which were occasioned by the Land-Grant Act of about a hundred years ago.'' In 1965, Senator Claiborne Pell of Rhode Island introduced legislation establishing Sea Grant colleges on campuses nationwide, leading to the adoption of the National Sea Grant College Act in 1966.

The first four universities to achieve Sea Grant College status were Oregon State, Texas A&M, the University of Rhode Island and the University of Washington in 1971. As of 2001, there are 30 Sea Grant Colleges divided into Great Lakes, Northeast, Mid-Atlantic, Southeastern Atlantic and Gulf of Mexico, and Pacific Regions.

[http://www.nsgo.seagrant.org/]

sea ice
More later.

sea level
Much more later.

sea level change
Recent analyses indicate that the global or eustatic sea level has risen about 2 mm per year over the last century, with the rate probably being much smaller for the previous several millennia. The rate is predicted to be larger over the next century - although how much larger is still uncertain. Quantifying sea level change is a difficult task given the complexity of the contributing processes including: See Douglas (1995).

Sea of Azov
See Azov, Sea of.

Sea of Candia
See Cretan Sea.

Sea of Crete
See Cretan Sea.

Sea of Japan
See Japan Sea.

Sea of Okhotsk
See Okhotsk Sea.

sea state
More later.

SeaBASS
Acronym for SeaWiFS Bio-Optical Archive and Storage System, a product of the calibration/validation element of the SeaWiFS project which provides an interface to the project holdings of bio-optical and laboratory instrument calibration data.

[http://seabass.gsfc.nasa.gov/]

SEA LION
Acronym for SEa ice in the Antarctic LInked with OceaN-atmosphere forcing, a project whose aim is to assess and improve the performance of coupled global atmosphere-sea ice-ocean models in reproducing sea ice in the high southern latitudes.

[http://www.iup.physik.uni-bremen.de/iuppage/sealion_ed1.html]

seamount
More later.

SEAREX
Acronym for Study on Sea-Air Exchanges program. See Riley and Chester (1989).

SEAS
Acronym for Study of the European Arctic Shelf, an LESC program.

SEAS
Acronym for Shipboard Environmental (Data) Acquisition System, a program developed by NOAA to provide accurate meteorological and oceanographic data in real time from ships at sea through the use of satellite data transmission techniques. The shipboard data is transmitted to NOAA via either the GOES or INMARSAT C satellites.

[http://www.dbcp.nos.noaa.gov/seas/seas.html]

SEASAR
Acronym for Synthetic Aperture Radar for Sea Studies.

SEASAT
A NASA satellite that operated from June 1978 to October 1978. Instruments on board included SASS, an altimeter, SMMR, a microwave SAR, and VIRR. The altimeter was an active radar altimeter which produced earth location and time-tagged satellite heights, significant wave heights, and geoid information. The SAR produced 25 meter resolution surface roughness imagery on a 100 km wide ground swath.

SeaSoar
An open ocean undulating data acquisition vehicle originally designed and built by the Institute of Oceanographic Sciences (now the Southampton Oceanography Center, UK). SeaSoar is capable of undulating from the surface to 500 m at tow speeds of up to 12 knots (with a faired cable) following a controlled and adjustable undulating path through the ocean. Data obtained from sensors mounted in SeaSoar are transmitted to the towing vessel via a multi-core tow cable.

[http://www.chelsea.co.uk/Vehicles%20SeaSoar.htm]

seasonal thermocline
In oceanography, a weakly stratified layer of water that appears when the mixed layer makes a rapid transition between its winter maximum and its summer mimimum. It is created by deep convection during the winter, and several processes are responsible for its restratification during the rest of the year. These processes, in chronological order starting in early spring, are the creation of a fossil thermocline during the ascent of the mixed layer, solar heating below the mixed layer, geostrophic advection, and thermohaline intrusion.

seasonal thermostad
See seasonal thermocline.

sea spray
See Andreas et al. (1995).

sea surface film
A microlayer hundreds of microns thick located at the sea-air interface. These are the site of intense accumulation of organic matter from underlying waters or atmospheric deposition. See Romano (1996).

sea surface slick
A sea surface film in which organic accumulation exceeds a threshold such that it becomes visible as a slick, i.e. a sea surface feature that appears as smooth grey spots or stripes in contrast to the surrounding deep blue waters. The smoothing effect is due to the accumulation at the sea-air interface of organic compounds, many of them surface-active, which enhance solar reflection at the surface by damping the capillary waves. Slicks are thought to play a significant role in heat flux and gas exchange, biogeochemical cycles, and pollutant dispersion dynamics as a consequence of the organic enrichment and their location at the boundary between atmosphere and ocean. See Romano (1996).

seawater
See Fofonoff (1962) and Fofonoff (1985).

SeaWiFS
Acronym for Sea-viewing Wide-Field of view Sensor, an ocean color sensor to study ocean productivity and interactions between the ocean ecosystems and the atmosphere. For more information see the SeaWiFs Web site.

SeaWinds
A scatterometer flown aboard the QuikSCAT mission.

SEBSCC
Abbreviation for Southeast Bering Sea Carrying Capacity, a NOAA PMEL investigation whose goal is to document the role of juvenile pollock in the eastern Bering Sea ecosystem, to examine the factors which affect their survival, and to develop and test annual indices of pre-recruit abundance.

[http://www.pmel.noaa.gov/sebscc/]

Secchi disk
A white target lowered from a vessel and viewed from above the surface in full solar illumination to estimate the attenuation in the water column. This is done by empirically relating the depth at which the disk disappears to the attenuation. This method was devised in the 1860s by an Italian astronomer named Angelo Secchi who used it while he worked in the Mediterranean aboard the papal vessel Immacolata.

The Secchi disc is usually 20-30 cm in diameter, and is either all white or has four quadrants, two painted white and two black. The empirical relation used is:

$\displaystyle {Z_S}\,=\,{F\over{C\,+\,+K \sin\theta}}$

where $ Z_S$ is the Secchi depth, $ C$ is the attenuation coefficient for directional light, $ K$ is the diffuse attenuation coefficient for non-directional light (sometimes known as the extinction coefficient), $ F$ is a background factor depending on the reflectivity of both the disc and the background and the observer's threshold perception of contrast, and $ \theta$ is the sighting angle from the horizontal. Typically, $ F$ ranges from about 8.7 in clear oceanic water to 6 in turbid estuarine water.

The disc is typically used to estimate the diffuse attenuation coefficent $ K$ or the attenuation coefficent $ C$. For the former, it has been found that the product of $ K$ and $ Z_S$ is relatively constant, with measurements in many types of water indicating that $ 1.4\,<\,K\times{Z+S}\,<\,1.7$. An empirical relationship has also been derived for the latter, i.e. $ V\,=\,0.7{Z_S}$.

SEC
Abbreviation for South Equatorial Current.

SECC
Abbreviation for South Equatorial Countercurrent.

SECHIBA
Acronym for Schematisation des Echanges Hydriques a l'Interface entre la Biosphere et l'Atmosphere, an LSP. See Ducoudre et al. (1993).

SECTIONS
Acronym for a research program which translates to Energetically Active Zones of the Ocean and Climate Variability. This was a joint program among Poland/USSR/Bulgaria/Germany/Cuba that gathered the largest data set ever collected in the tropical Atlantic. The six ships used in the program were the Academic Vernadsky and the Mikhael Lomonosov from the Marine Hydrophysical Institute (MHI) of the Ukrainian Academy of Science in Sevastopol and the Volna, Jakov Gakkel, Dmitry Ushakov, and Parshin of the State Oceanographic Institute (SOI) of the USSR. The MHI vessels collected hydrographic data at 5 m vertical intervals with 65% of the stations extending to 1200 m, while the SOI vessels collected data at 10 m intervals (although it was archived only at 16 standard levels). The combined data set archived at MHI consists of 4931 temperature and salinity profiles collected during 26 surveys carried out from 1984 to 1990.

The surveys were divided into three stages. The first stage (1984-1985) comprised eight surveys conducted near the South American coast between 2$ ^\circ$ S and 20$ ^\circ$ N, with each survey consisting of 8 to 10 hydrographic sections perpendicular to the coast. The sections were 100 km and the stations 50 km apart in a survey designed to define the seasonal cycle in the northwest. The second stage (1986-1988) comprised twelve surveys conducted between 2$ ^\circ$ S and 12$ ^\circ$ N latitude and 58$ ^\circ$ and 5$ ^\circ$ W longitude. During the first two years of this stage the sections were 166 km and the stations 55 km apart, with the between-section spacing increased to 333 km durin the final year. Two or three vessels were usually simultaneously collecting data in a survey designed to investigate the seasonal variability of the North Equatorial Countercurrent (NECC). The third stage (1989-1990) saw seven surveys organized into three experiments designed to observe synoptic variability, with one experiment in the west and one in the central basin. The first experiment took place in the spring of 1989 with two vessels in the western region; the second was in the fall of 1989 in the east with two vessels; and the third took place in the winter of 1990 using two vessels in the west. See Chepurin and Carton (1997).

SEEP-I
A program to examine shelf edge exchange processes on the outer margin of the U.S. Mid Atlantic Bight. The SEEP program began in 1980 when a group of investigators met to propose an interdisciplinary, inter-institutional program called SEEP (Shelf Edge Exchange Processes) to test what was known as the ``shelf-export hypothesis.'' This was a conjecture that the large fraction of the spring phytoplankton bloom that was observed to not be consumed by the local pelagic food web was exported from the continental shelves to the central ocean basins or to the sediments of the upper continental slope. It was predicted that the net export of particles across the shelf-slope break would increase with successive, more southerly experiments because of an expected southerly increase in primary productivity, and also because of a southerly decrease in the width of the shelf. A primary problem with the hypothesis was the existence of a strong temperature-salinity front separating the continental shelf and slope, the sort of barrier particles would find difficult to cross. However, iseveral other mechanisms for exporting particles from the shelf - e.g. entrainment of shelf water by passing warm core eddies, sinking across the front, advection by the benthic boundary layer - were identified and thought to be collectively sufficient for the task. They were also collectively referred to as ``diffusive'' processes.

SEEP-I took place from July 1983 to October 1984 in the waters of the Mid-Atlantic Bight (MAB) shelf and slope south of Cape Cod and Long Island. The field program consisted of two experiments run by two different groups, with little overlap between them. This fragmentation of effort led to estimates of particle export ranging from $ <$10% diffusive exchange across the shelf edge (with some indication of an increase towards the southwest), to 10-20% with most oxidized on the shelf, to from $ <$10% to nearly 40% in model results. This led to the design and implementation of SEEP-II. See Walsh et al. (1988).

SEEP-II
A program to examine shelf edge exchange processes on the outer margin of the U.S. Mid Atlantic Bight. This follow-up to SEEP-I took place from February 1988 to June 1989, during which 10 cruises took place and 10 moorings were placed at 12 locations on the shelf and upper slope south of the Delmarva Peninsula. The vanishing likelihood of a SEEP-III led to the moorings being deployed in two transects parallel to the mean isobaths and 90 km apart, the latter to attempt to identify the hypothesized increase in across-shelf particle flux to the south. SEEP-I was more integrated than SEEP-I, with the instrumentation from different institutions intercalated throughout the experiment. The result was perhaps the most extensive set of moored, synoptic measurements of temperature, salinity, phytoplankton chlorophyll fluorescence, macrozooplankton, oxygen, current conditions and verticle particle flux yet acquired in an oceanographic program.

According to Biscaye et al. (1994):

The results of the SEEP-II study overwhelmingly show that the hypothesis of export of a large proportion of the MAB [Mid-Atlantic Bight] shelf primary productivity is untenable. All the observational data suggest that although a small fraction of carbon is exported across the shelf-slope break and through the front to the slope decpocenter, the principal fate of shelf carbon is, in fact, oxidation on the shelf. That small portion that does escape the shelf to the shelf water and depocenter appears to increase from the northern to the southern MAB.
Several key questions remained unresolved, though, including: See Biscaye et al. (1994).

seiche
More later.

seismic sea wave
Much more later.

Seismic Sea-Wave Warning System
A network of seismographs across the Pacific Ocean to serve as an early warning system against the arrival of seismic sea waves (SSW) (also called tsunamis or, in an egregious misnomer, tidal waves). The SSWWS was established in 1946 after a particularly destructive SSW originating at Unimak, Alaska struck Hawaii and killed 159 people. Its headquarters are in Honolulu, Hawaii and it is operated by the Coast and Geodetic Survey of the U.S. Dept. of Commerce.

SEMAPHORE
An experiment that took place in the northern Canary Basin from July to November 1993. A large data set was obtained from three hydrographic arrays, current meter moorings, surface drifters drogued at 150 m, and 2000 m deep RAFOS floats. See Eymard (1998).

semidiurnal
Descriptive of a tide that has a cycle of approximately one-half a tidal day, as opposed to diurnal.

semi-geostrophic equations
See G. and Flierl (1981).

semi-implicit method
A numerical approximation algorithm that allows longer time steps than an explicit method and is less computationally onerous than a fully implicit method. Algorithms can usually be designed using this compromise method that both allow the longer time step and don't sacrifice numerical accuracy.

sensible heat
The portion of total heat associated with a temperature change, as opposed to latent heat. This is so-called because it can be sensed by humans. The sensible heat is calculated by

$\displaystyle \Delta Q\,=\,m\,{C_p}\,\Delta T$

where $ C_p$ values are

$\displaystyle {C_{pd}}\,=\,1004.67\,{{\text{J kg}}^{-1}}{\text{K}^{-1}}$

for dry air,

$\displaystyle {C_p}\,=\,{C_{pd}}\,(1\,+\,0.84\,r)$

for moist air (where $ r$ is the mixing ratio of water vapor), and

$\displaystyle {C_{\text{liq}}}\,=\,4200\,{\text{J kg}^{-1}}{\text{K}^{-1}}$

for liquid water.

sensible heat flux
The flux of heat between the ocean surface and atmosphere that results mainly from their difference in temperature. The heat exchange is accompished via molecular conduction in the first few millimeters above the surface and via turbulent mixing and convection above that. The flux is usually from the ocean to the atmosphere during the day and opposite during the evening and night. See Peixoto and Oort (1992).

separation formula
A method for computing the adiabatic inter-hemispheric meridional transport. See Nof (1998).

SEQUAL
Acronym for the Seasonal Response to the Equatorial Atlantic research program. See Katz (1987) and Richardson and Reverdin (1987).

Seram Sea
One of the seas that comprise the Australasian Mediterranean Sea. This is centered at about 130$ ^\circ$ E and 2-3$ ^\circ$ S and surrounded by Buru and Seram to the south and by Halmahera and the wester part of Irian Jaya to the north. It connects with the Arafura Sea to the southeast, the Banda Sea to the southwest, and the Halmahera Sea to the north. It is variously spelled Ceram Sea.

Seven Seas
A term used long ago to collectively refer to the Indian Ocean, the Red Sea, the Persian Gulf, the Black Sea, the Sea of Azov, the Adriatic Sea and the Caspian Sea. The term is no longer much used although it is generally conceded that a modern and more geographically generous grouping would be the Arctic Ocean, the Southern Ocean, the Indian Ocean, the North and South Atlantic Ocean and the North and South Pacific Ocean.

shallow atmosphere approximation
In meteorology, an approximation made to simplify the equations of motion in spherical coordinates where the radial distance r is replaced by a+z, where the altitude z is much smaller than the radius of the Earth r. See Salby (1992).

shallow scattering layer
A layer of marine organisms found over a continental shelf which scatter sound. These layers are usually composed of patchy and horizontally discontinuous groups whose horizontal dimensions are usually less than their vertical dimensions. There are also surface and deep scattering layers.

shallow water approximation
In oceanography, an approximation made for motions where the aspect ratio $ \delta\,=\,H/L$ (where $ H$ is the vertical length scale and $ L$ he horizontal scale) is small. An example arises in the study of the tides, where the horizontal scale of the wave motion is thousands of kilometers and the vertical scale in constrained by the maximum depth of the oceans, and as such the applicable dynamics are those of shallow water gravity waves, i.e. gravity waves that ``feel'' and are influenced by the bottom.

The shallow water equations are obtained (after Muller (1995)) by applying the spherical approximation to the Boussinesq equations, expanding them with respect to $ \delta$, and keeping only zeroth order terms. One obtains:

$\displaystyle { {\partial u} \over {\partial t} }\,$ $\displaystyle +$ $\displaystyle \, { u \over {{r_0}\cos\theta} }{ {\partial u} \over {\partial\ph... ... {\partial u} \over {\partial z} }\,-\, { {uv} \over {r_0} }\tan\theta\,-\,fv\,$  
  $\displaystyle =$ $\displaystyle \, -{1\over{{\rho_*}{r_0}\cos\theta}}{ {\partial p} \over {\partial\phi} }$  
$\displaystyle { {\partial v} \over {\partial t} }\,$ $\displaystyle +$ $\displaystyle \, { u \over {{r_0}\cos\theta} }{ {\partial v} \over {\partial\ph... ...{\partial v} \over {\partial z} }\,+\, { {u^2} \over {r_0} }\tan\theta\,-\,fu\,$  
  $\displaystyle =$ $\displaystyle \,-{1\over{rho_*}}{ {\partial p} \over {\partial\theta} }$  
$\displaystyle 0\,$ $\displaystyle =$ $\displaystyle \,{ {\partial \rho'} \over {\partial z} }\,+\,\rho 'g$  
$\displaystyle { {\partial w} \over {\partial z} }\,$ $\displaystyle =$ $\displaystyle \, -{ 1 \over {{r_0}\cos\theta} }{ {\partial u} \over {\partial\p... ...1 \over {{r_0}\cos\theta} }{ {\partial (v\cos\theta )} \over {\partial\theta} }$  
$\displaystyle { {\partial \rho '} \over {\partial t} }\,$ $\displaystyle +$ $\displaystyle \, { u \over {{r_0}\cos\theta} }{ {\partial \rho '} \over {\parti... ...'} \over {\partial\theta} }\,+\, w{ {\partial\rho '} \over {\partial z} }\,=\,0$  

where $ (u,v,w)$ are the velocity components, $ r_0$ is the mean radius of the Earth, $ (\phi , \theta , r)$ are spherical polar coordinates where $ \phi$ is longitude, $ \theta$ latitude, and $ r$ radial distance, $ f$ is the Coriolis parameter, $ \rho_*$ is a constant reference density, $ p$ is the pressure, $ \rho '$ is the deviation from the reference density and $ g$ is gravitational acceleration. See Muller (1995).

shallow water equations
See shallow water approximation.

SHEBA
Acronym for the Surface Heat Budget of the Arctic project, a WCRP program to address the interaction of the surface energy balance, atmospheric radiation, and clouds over the Arctic Ocean.

[http://sheba.apl.washington.edu/]

shelf sea
A shallow sea that occupies a portion of a wide continental shelf. This is one type of epicontinental sea. Compare to epeiric sea and inland sea.

Shelikof Strait
A strait located between the Alaska Peninsula and Kodiak Island at around 58$ ^\circ$N, 154$ ^\circ$W. See Reed and Bograd (1995).

SHIVA
Acronym for Studies of the Hydrology, Influence and Variability of the Asian summer monsoon, a project sponsored by the European Commission. The project goals are:

[http://www.enm.meteo.fr/ufr/umt/shiva/main.html]

short-crested waves
A propagating surface gravity wave with a free surface elecation which is doubly periodic in two perpendicular directions, along and normal to the direction of propagation. These can be produced either by the interaction of two progressive waves angles to each other or by oblique reflection from a maritime structure. The doubly periodic nature is characterized by the pattern of island crests that are formed at intersections of the component waves, rendering the surface shape of such a wave system much more complex than its wave components. The isolated crests thus produced propagate in a combined direction with a wavelength and a definite crest length equal to the distance between successive crests normal to the former at the same time. The transverse distance between adjacent crests is finite as opposed to the original two-dimensional wave motions that combine to form short-crested waves, thus giving them their name. See Hsu (1990).

Siberian Coastal Current
See Weingartner et al. (1999).

Siberian High
One of the centers of action that tend to control large scale weather patterns around the globe. This center forms over Siberia during the winter and is centered around Lake Baikal. The sea level pressure exceeds 1030 millibars from late November to early March. The resulting anticyclonic circulation pattern is enhanced by the tendency of the surrounding mountains to prevent the cold air from easily flowing away. This pattern is replaced by a low pressure pattern in the summer related to the monsoon circulation.

SIBEX
Acronym for Second International BIOMASS Experiment.

Sibuyan Sea
A regional sea contained within the Philippines between the northern island of Luzon and the central island group the Visayan Islands. It is centered at about 122.5$ ^\circ$ E and 12.3$ ^\circ$ N and connected to the Visayan Sea to the southeast, the Samar Sea to the east, the Sulu Sea to the southwest via the Tablas Strait, and the South China Sea to the northwest via the Verde Island Passage. Geographical features of note include Sibuyan Island and Marinduque Island as well as the Ragay Gulf in the southeast arm of Luzon.

Sierra Leone Basin
An ocean basin located to the west of Africa at about 3$ ^\circ$ N in the east-central Atlantic Ocean. See Fairbridge (1966).

SIGMA
Acronym for Significant Interactions Governing Marine Aggregation, a group that conducted an investigation of the aggregation of a diatom bloom in a laboratory mesocosm to test the ability of coagulation theory to predict aggregation in complex marine systems. See Alldredge and Jackson (1995).

sigma-t ($ \sigma_t$)
A conventional definition introduced into physical oceanography for purposes of brevity. It is the remainder of subtracting 1000 kg m$ ^{-3}$ from the density of a sea water sample at atmospheric pressure, i.e.

$\displaystyle {\sigma_t}\,=\,({\rho_{S,T,0}}\,-\,1000)$

where $ S$ and $ T$ are the in situ salinity and temperature. The density of water ranges from 1000 kg/m3 to about 1028 kg m$ ^{-3}$ for the densest ocean surface water, so sigma-t ranges from about 0.00 to 28.00, with the units usually omitted.

sigma-theta ( $ \sigma_\theta$)
A measure of the density of ocean water where the quantity sigma-t is calculated using the potential temperature $ \theta$ rather than the in situ temperature, i.e.

$\displaystyle {\sigma_{\theta}}\,=\,({\rho_{S,\theta,0}}\,-\,1000)$

where $ S$ is the in situ temperature.

significant wave height
A quantity defined by Walter Munk in 1944 (in an SIO technical report) as the average height of the one-third highest waves. He stated that this was about equal to the average height of the waves as estimated by an experienced observer. The quantity is usually written as $ H_{1/3}$ or $ H_S$ and estimated using the calculated root-mean-square height of the observed waves. The latter is calculated as

$\displaystyle {H_{rms}}\,=\,\sqrt{{1\over N}{\sum^N_{j=1}}\,{H^2_j}}$

where $ N$ is the total number of observed waves and $ H$ their heights. The significant wave height is estimated via:

$\displaystyle {H_S}\,\approx\,\sqrt{2}{H_{rms}}.$

See Bauer and Staabs (1998).

significant wave method
See S-M-B method.

silicate pump
A mechanism that acts in diatom-dominated communities to enhance the loss of silicate from the euphotic zone to deep water compared to nitrogen, which is more readily recycled in the grazing loop, thus leading the system to silicate limitation. The silicate pumping to deep water results in low silicate, high nitrate conditions in the mixed layer. In such situations silicate dynamics may control and dominate new production processes and consequently control the rate at which newly upwelled CO$ _2$ in the surface regions is reduced by the phytoplankton. See Dugdale et al. (1995).

siliceous ooze
A fine-grained sediment of pelagic origin found on the deep-ocean floor. It contains more than 30% siliceous material of organic origin and is usually found below the carbon compensation depth at depths greater than 4500 m. Two types of this are radiolarian oozes and diatom oozes

SIMIP
Acronym for Sea Ice Model Intercomparison Project, an international effort to develop an improved representation of sea ice in climate models. SIMIP is carried out in the framework of ACSYS within the WCRP. A hierarchy of sea ice rheologies is evaluated on the basis of a comprehensive set of observational data. Four different sea ice rheology schemes are compared: The same grid, land boundaries, and forcing fields are applied to all models, with the prognostic equations solved on a spherical grid for the whole Arctic with a resolution of 110 km and a daily time step. The results as summarized at the project web site are:
Overall, the viscous-plastic rheology yields the most realistic simulation. In contrast, the results of the very simple free drift model with velocity correction clearly show large errors in simulated ice drift as well as in ice thicknesses and ice export through Fram Strait compared to observation. The compressible Newtonian fluid cannot prevent excessive ice thickness buildup in the central Arctic and overestimates the internal forces in Fram Strait. Because of the lack of shear strength, the cavitating-fluid model shows marked differences to the statistics of observed ice drift and the observed spatial pattern of ice thickness. Comparison of required computer resources demonstrates that the additional cost for the viscous-plastic sea ice rheology is minor compared with the atmospheric and oceanic model components in global climate simulations.
See Kreyscher et al. (2000).

[http://www.ifm.uni-kiel.de/me/research/Projekte/SIMIP/simip.html]

Singular Spectrum Analysis
A method of time series analysis, sometimes abbreviated as SSA, designed to extract as much information as possible from short, noisy time series without prior knowledge of the dynamics underlying the series. It is a form of Principal Component Analysis applied to lag-correlation structures of time series. It was developed by Broomhead and King (1986) and applied to the analysis of paleoclimate time series by Vautard and Ghil (1989) and Vautard et al. (1992). The SSA Toolkit includes SSA amongst several time series analysis tools.

SSA performs better than traditional Fourier analysis at separating closely spaced relevant spectral peaks, but retains problems such as the requirement of stationarity and the limitation to situations of high SNRs. See Ruiz de Elvira and Bevia (1994).

SIO
Abbreviation for Scripps Institution of Oceanography.

SIR-C
Acronym for the Shuttle Imaging Radar-C used for geologic, hydrologic, and oceanographic studies. It can image the Earth through cloud cover and its sensitivity to surface roughness, soil moisture, and sea-ice-water contrast makes it useful in studies of geological features, canopy morphology, sea-ice dynamics, and ocean surface temperature. See the SIR-C Web site.

SISMER
Acronym for Systemes d'Informations Scientifiques pour la Mer or, in translation, the French National Oceanographic Data Center. See the SISMER Web site.

SIW
In physical oceanography, a water mass. See Tomczak and Godfrey (1994), p. 161.

Six thermometer
A self-registering maximum and minimum thermometer invented by James Six (1731?-1793) of England in 1782. It consisted of a U-shaped tube with mercury in the bend, one side filled with alcohol, and the other partially filled. Indices marked the highest and lowest temperatures. This was the most widely used thermometer for taking deep sea temperatures up until the 1870s. See Deacon (1971).

SIZEX
Acronym for Seasonal Ice-Zone Experiment.

Skagerrak
A circulation controlled sedimentary basin that provides part of the connection (along with Kattegat) between the North Sea and the Baltic. It is surrounded by Norway to the northwest, Sweden to the northeast, Denmark and Kattegat to the southeast, and the North Sea to the southwest. It is centered at approximately 9$ ^\circ$ E and 58$ ^\circ$ N and is the deepest part ($ >$ 700 m) of the the Norwegian Trench.

The circulation in Skagerrak is counterclockwise with North Sea water masses entering via the Jutland Current in the southwest, proceeding northeastward along the Denmark coast, combining with some of the brackish Baltic Current, turning and flowing northwestward along Sweden, turning again and becoming the Norwegian Coast Current (NCC) as it flows southwestward along Norway, and finally leaving Skaggerak and turning northwards as the NCC. There is also a deep countercurrent beneath the NCC that injects high salinity Atlantic water into the Skagerrak deep. See Svansson (1975), Rodhe (1996) and Danielssen et al. (1997).

SKAGEX
Acronym for Skagerrak Experiment, an ICES experiment carried out from spring 1990 to spring 1991 in the Skagerrak. The main stage lasted four weeks with shorter and less intensive stages occurring at other times. The objectives of the experiment were to identify and quantify the various water masses entering and leaving the Skaggerak area and their variation over time, to investigate the mechanisms that drive the circulation in the area and its link with biological processes, and to investigate the pathways of contaminants through the Skagerrak. The project leader was B. Dybern.

[http://www.ices.dk/ocean/project/data/jskag66.htm]
[http://www.ices.dk/ocean/project/data/skagex.htm]

skin effect
A temperature inversion in a thin near-surface ocean layer with a thickness of several millimeters. This is a source of uncertainty in radiometric measurements. The inversion layer, created mainly by evaporation, results in an underestimation of the SST compared with what it would be as determined by conventional methods in a layer with a thickness ranging from several tens of centimeters to several meters. See Kagan (1995).

skin temperature
The temperature of the millimeter thick skin layer at the surface of the ocean. The skin temperature is 0.1-0.5$ ^\circ$C cooler than the water a few millimeters below the surface. The skin is cooler than the layer just beneath because the net heat balance at the surface is from the ocean to the atmosphere, even during strong solar insolation and weak winds. This is because the sensible and latent heat fluxes at the air-sea interface are usually net losses from the ocean. The net longwave emission at the surface is also usually a heat loss. The incoming shortwave solar radiation is absorbed by the upper layers, with the infrared absorbed in the upper meter, the ultraviolet in the upper 3-5 m, and the visible in the upper 100 m. The shortwave absorption at the surface is therefore small, and the ocean surface loses heat. The heat lost is obtained from a flux from the interior via molecular conduction since turbulence is damped close to the surface. A large temperature gradient is required to accomodate the surface heat losses, which causes the skin temperature to drop sufficiently such that the resulting gradient can handle the flux from the interior. See Kantha and Clayson (2000).

slab ocean
A simple, non-dynamic ocean model used in coupled model simulations. SSTs are calculated from surface energy balance and heat storage in a fixed-depth mixed layer but there are no ocean currents, i.e. we account for the effects of local and temporal but not non-local processes. The salient equilibration time of this type of model is that of the slab ocean, usually on the order of about 20 years for a 50 m thick slab.

SLEUTH
Acronym for System for Locating Eruptive Underwater Turbidity and Hydrography.

slippery sea
A phenomenon occurring in the wind-driven layer at the surface of the sea. In conditions of strong surface heating, a well-mixed warmer (and lighter) layer if formed, which is of limited depth because the stabilizing density distribution inhibits vertical mixing with the deeper, colder water. At the bottom of this surface layer is a strong density gradient where the turbulence is suppressed and the Reynolds stresses are small. A given wind stress at the surface can thus accelerate the water to produce stronger surface currents in this case compared to an unstratified ocean. This is true because both the depth of the layer involved is smaller and the retarding stress below it is reduced. This creates the slippery sea phenomenon. See Turner (1973).

Slope Water (SW)
A water mass that forms between the Gulf Stream and the continental shelf in the northwestern Atlantic Ocean. It is isolated by the Stream from contact with oceanic water masses in its depth range and therefore forms via interactions among shelf water, water from the Labrador Current, and water from the Gulf Stream. The Slope Water thus formed extends over the upper 1000 m of the water column north of Cape Hatteras along the continental rise and has a nearly linear T-S curve similar to that evinced by North Atlantic Central Water (NACW). The T-S curve typically extends from 21$ ^\circ$ C-36.0 to 15$ ^\circ$ C-35.1. Slope Water is intermittently transported by cyclonic rings across the Gulf Stream and into the Sargasso Sea. See Tomczak and Godfrey (1994).

slow manifold
A hypothetical N-dimensional manifold (i.e. surface) embedded in the 3N-dimensional phase space of a primitive equation model that is devoid of gravity waves. This has been called the Holy Grail of initialization schemes for weather forecasting since if a numerical weather prediction model could be initialized with observations filtered to retain just their components on the slow manifold, then the large-amplitude gravity waves that have wrecked numerical forecasts since Richardson would no longer be a problem. The concept was introduced by Leith (1980) and is reviewed by Boyd (1995).

SLP
Abbreviation for sea level pressure.

S-M-B method
A method of wave forecasting developed by Sverdrup, Munk and Bretschneider, whence comes the name. This approach yields predictions of significant wave height $ {H_{1/3}}$ and significant wave period $ {T_{1/3}}$ from known storm conditions, i.e. wind velocity $ U$, fetch distance $ F$ and storm duration $ t$. This method can be used for a partially arisen sea. Predictions are made empirically using graphs of all the available data in terms of the dimensionless ratios $ gF/{U^2}$, $ gt/U$, $ gH/{U^2}$ and $ gT/U$. The empirical equations used to develop the graphs are:
$\displaystyle { {gH}\over{U^2} }\,$ $\displaystyle =$ $\displaystyle \,0.283 \tanh \left[0.0125{{ \left({ {{gF}\over{U^2}} }\right) }^{0.42}}\right]$  
$\displaystyle {{gT}\over{2\pi U}}\,$ $\displaystyle =$ $\displaystyle \,1.20\tanh \left[0.077{{ \left({ {{gF}\over{U^2}} }\right) }^{0.25}}\right]$  
$\displaystyle {{gt}\over U}\,$ $\displaystyle =$ $\displaystyle \,K\,e^{\left( {{ \left\{A {{\left[\ln\left({{gF}\over{U^2}}\righ... ...right)\,+\,C\right\} }^{1/2}}\,+\, D\,\ln\left({{gF}\over{U^2}}\right) \right)}$ (16)

where $ g$ is the gravitational acceleration, $ U$ is the estimated wind velocity, $ F$ is the fetch length, $ t$ is the wind duration, $ T$ is the significant wave period and $ H$ is the significant wave height. The constant values are $ K$ = 6.5882, $ A$ = 0.0161, $ B$ = 0.3692, $ C$ = 2.2024 and $ D$ = 0.8798. See Komar (1976).

smeddie
See Pingree and LeCann (1993).

SMHI
Abbreviation for Sveriges Meteorologiska och Hydrologiska Institut or Swedish Meterological and Hydrological Institute. See the SMHI Web site.

SMILE
Acronym for Shelf Mixed Layer Experiment, a WHOI research program designed to study the response of the oceanic surface boundary layer over the continental shelf to atmospheric forcing. SMILE took place over the northern California shelf between Pt. Arena and Pt. Reyes from mid-November to mid-May 1989. See Alessi et al. (1991).

[http://uop.whoi.edu/data/smile/smile.html]

SMMR
Abbreviation for Scanning Multichannel Microwave Radiometer, an instrument that has been on board both SEASAT and NIMBUS-7. It produced earth location and time-tagged SSTs, surface wind stress, atmospheric water vapor, liquid water content, and precipitation rate information. See Liu (1984).

SMONEX
Acronym for Summer Monsoon Experiment, a program taking place from May 1 to August 31, 1979 in eastern African, the northern part of the Indian Ocean, the Arabian Sea, the Bay of Bengal, and in adjacent continental areas.

[http://www.meteo.ru/fund/inter.html]

SMWG
Abbreviation for Synthesis and Modeling Working Group, a WOCE committee.

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Manbreaker Crag 2001-08-17