- Acronym for Towed Ocean Bottom Instrument, a deep-towed
multi-sensor sonar sytem that comprises a two-sided
30 kHz sidescan sonar, a 7.5 kHz sub-bottom profiler sonar,
a magnetometer, a temperature probe, a transmissometer, and
a range of vehicle handling instruments.
TOBI is towed on a 200 meter umbilical behind a 600 kg depressor
weight attached to the surface ship via the main 0.68 in. armored
coaxial cable, which reduces ship-induced heaving that influences
the stability of the vehicle.
The sidescan sonar has a range of 6 km and a seabed footprint
ranging from 4 by 7 meters close to the vehicle to 42 x 2 meters
at longer ranges, and the profiler sonar can penetrate up to
60 meters into soft sediments with a vertical resolution of better
than 1 meter. This instrument was developed by
See Flewellen et al. (1993) and the
TOBI Web site.
- Acronym for Tropical Ocean Climate Study, a project commenced by
JAMSTEC in 1993 as a follow-up to the JAPACS
program as a Japanese contribution to
The objective of TOCS is to achieve a better understanding of the
western Pacific warm pool and its effects on ocean circulation,
the ENSO phenomenon, and global climate change.
- Acronym for Tropical Ocean and Global Atmosphere program, a
WCRP program beginning in 1985.
The objectives of TOGA were:
- to gain a description of the tropical oceans and the global
atmosphere as a time-dependent system, in order to determine the
extent to which this system is predictable on timescales of months
to years, and to understand the mechanisms and processes underlying
- to study the feasibility of modeling the coupled ocean-atmosphere
system for the purpose of predicting its variations on timescales of
months to years; and
- to provide scientific background for designing an observing and
data transmission system for operational prediction if this capability
is demonstrated by the coupled ocean-atmosphere system.
The objectives were addressed by:
- building the TOGA Observing System;
- conducting a major process study in the tropical Pacific,
- developing a sequence of coupled ocean-atmosphere models of
the tropical Pacific;
- conducting a program of prediction studies through the TOGA
Numerical Experimimentation Group;
- conducting analytic and diagnostic studies of the
ENSO phenomenon; and
- relating ENSO to seasonal-to-interannual
variability in other tropical regions, especially in the
Significant results from the TOGA program include:
See McPhaden et al. (1998).
- documentation of the ENSO cycle and related phenomeno, such as
the mean seasonal cycle and intraseasonal variability, with
unparalleled resolution and accuracy;
- testing of ENSO theories such as the delayed oscillator;
- development of new theoretical concepts relating to ocean-atmosphere
interactions on seasonal-to-interannual time scales;
- development of ocean, atmospheric, and coupled ocean-atmosphere
- development of ocean data assimilation systems for improved climate
analyses and for initializing climate prediction models.
- Acronym for TOGA Marégraphies Atlantique.
- Acronym for Typhoon Operational Experiment, a WMO
3-year project for testing the typhoon warning system under real typhoon
- A cooperative project between the U.S. (NASA) and France (CNES) which was
the first space mission specifically designed and conducted for
studying the circulation of the world's oceans.
TOPEX is the collective name for the instruments comprising the
U.S. portion of the mission and POSEIDON that for the French portion.
The satellite uses a state of the art altimetry system to measure
the precise height of sea level from which information about
the ocean circulation can be obtained.
It was launched on August 10, 1992 and began making measurements
in late September of the same year.
The unprecedented accuracy required for obtaining useful information
about the ocean circulation from altimetry measurements led to
a number of innovations.
These included the first dual-frequency space-borne radar altimeter
capable of retrieving the ionospheric delay of the radar signal,
a three-frequency microwave radiometer for retrieving the signal delay
caused by water vapor in the troposphere, an optimal model of
the Earth's gravity field, and multiple satellite tracking systems
for precision orbit determination.
These innovations produce single-pass sea level measurements
with a root-sum-square accuracy between 4.7-5.1 cm, better than
the requirement for useful data of 13.7 cm.
The mission is designed to last for at least 3 years with a possible
extension to 6 years.
The orbit configuration was chosen to avoid aliasing tidal
signals into the frequencies of ocean current variabilities.
The chosen inclination of 66 degrees avoids this as well
as the aliasing of different tidal constituents to the same frequency.
A 9.916 day repeat period allows an equatorial cross-track
separation of 316 km.
An orbital height of 1336 km satisfied several constraints including
maximizing the accuracy of orbit determination and minimizing the
power needed to achieve the required level of signal to noise ratio.
The satellite circles the world every 112 minutes
between latitudes 65 N and S, allowing it to measure
sea surface height over 90% of the world's ice-free oceans.
The mission payload consists of six scientific instruments.
The four operational sensors are:
The two experimental sensors are the single-frequency solid-state
radar altimeter (SSALT)
and the Global Positioning System (GPS)
demonstration receiver (GPSDR).
See Fu et al. (1994).
- the dual-frequency radar altimeter (ALT),
- the TOPEX microwave radiometer (TMR),
- the laser retroflector
- and the Doppler orbitography and radiopositioning
integrated by satellite (DORIS)
dual Doppler tracking system
- topographic form stress
- The integrated horizontal pressure force on the bottom.
See McWilliams (1996).
- topographic Rossby wave
- To be completed.
See Hendershott (1981), p. 309.
- topographic steering
- The deflection or steering of flow required to keep the
constant. For large scale processes in the interior of the
ocean, we can neglect the
and the potential vorticity reduces to . As such, if
a water column stretches, i.e. D increases, (shrinks, i.e. D decreases)
to accomodate a greater (lesser)
depth, then it must move toward (away from) the nearest
pole to increase (decrease) to keep its ratio to
- Acronym for Total Ocean Profiling System.
- Torres Strait
- See Gulf of Carpenteria.
- Abbreviation for True Oxygen Utilization.
- A study of mesoscale eddies in the northeast Atlantic Ocean.
See Le Group Tourbillon (1983).
- Acronym for Tower Ocean Wave and Radar Dependence Experiment, an
experiment conceived to provide a data base to resolve the
disparity among different
Synthetic Aperture Radar
(SAR) ocean surface imaging theories. The specific objectives
were to investigate the hydrodynamics of short waves and their
modulation by long waves, to assess the assumptions stipulated
in radar backscatter theory that are used in SAR ocean surface
imaging, and to develop a verifiable theory for SAR imaging
of the ocean surface.
See Shemdin (1990).
- Abbreviation for the TOGA Program on
Prediction. See the TPOP Web site
for more information.
- Abbreviation for Trans-Pacific Profiler Network, a joint
NOAA/University of Colorado project.
- Abbreviation for the series of Trans-Pacific expeditions
along 24 N in 1985.
- Abbreviation for the series of Trans-Pacific expeditions
along 47 in 1985.
- Abbreviation for Tropical Pacific Thermal Monitoring System.
- Acronym for Tracing the Water Masses of the North Atlantic and the
Mediterranean, a project to use a Lagrangian trajectory method to investigate
the North Atlantic and Mediterranean water mass circulation as they
result from numerical simulations of the global ocean.
The major goals of the project are to investigate:
The OCCAM, OPA and
GIM circulation models will be used in the investigation.
- the origin and formation of NADW;
- the fate and transformation of NADW;
- the Mediterrean Water mass circulation; and
- the Lagrangian trajectory methods to be used.
- trade winds
- The trade winds, or tropical easterlies, are the winds which diverge
from the subtropical high-pressure belts, centered at 3-40 N and
S, towards to equator, from north to east in the northern hemisphere
and south to east in the southern hemisphere.
- transfer efficiency
- In marine ecology, the ratio of the production of one
trophic level to that of the
next. This is a reasonable estimate of the
if it is assumed that the energy extracted from a given
trophic level is proportional to its production.
See Barnes and Hughes (1988).
- transfer function
- A device used in paleoclimate data analysis to obtain
proxy data. An equation, or transfer
function, is developed
using mathematical techniques of regression that relates the actual data
(.e.g. planktonic fossil assemblages) to
some desired physical variable (.e.g. water temperature). See
Imbrie and Kipp (1971), Kipp (1976)
and Crowley and North (1991).
- transfer velocity
- See piston velocity.
- Transitional Mediterranean Water (TMW)
- A transition water mass found between the overlying
Levantine Intermediate Water (LIW) and
Eastern Mediterranean Deep Water (EMDW) in
the eastern Mediterranean Sea.
The TMW is relatively colder (14.25C) and slightly less
saline (38.88-38.90) than LIW.
See Theocharis et al. (1999).
- In dynamical systems theory, a system is said to be transitive if
different sets of initial conditions all evolve to a single
resultant state. Compare to intransitive
and almost intransitive.
See Lorenz (1979).
- An instrument for the measurement of the transmission of light
of a given wavelength over a known distance in a seawater sample.
The wavelengths are usually chosen based on the particles being
studied, with about 660 nanometers the wavelength most often used.
The changes in transmission are primarily related to changes in
the abundance and type of particles present, with most
variations resulting from particles less than 20 microns in
- In radiation transfer, the fraction of incoming radiation that
is transmitted into or through a medium.
The sum of this, the absorptance,
and the reflectance must equal unity.
- Acronym for TRANS-PACific experiment.
See White and Bernstein (1979).
- Abbreviation for Tracer Release Experiment.
- Acronym for Tsunami Risk Evaluation through Seismic Moment from
- trench wave
- See Mysak et al. (1979).
- A type of drifter.
See Niiler et al. (1995).
- A hydrogen isotope useful as a tracer in ocean studies.
It is the heaviest isotope of hydrogen, and emits a low
energy beta particle in its decay to helium-3. Being
hydrogen, it exists almost exclusively as water and is
thus transported only by fluid motion and vapor exchange, making
it an ideal hydrologic tracer. Tritium is produced naturally
in the upper atmosphere by cosmic ray spallation, with
pre-nuclear concentrations in precipitation around 5-10
Tritium Units (TU)
and surface water concentrations ranging from 0.1 to 0.5 TU.
The pre-nuclear natural inventory was around 3.6 kg.
Atmospheric nuclear weapons testing in the 1950s and 1960s produced
tritium in quantities that dwarfed the natural inventory which,
given the subsequent cessation of such testing, offered a unique
opportunity to study the long-term transport through the ocean
of a large spike of an important and readily identified tracer.
About 500 kg of tritium was produced by the weapons testing
programs, boosting the concentration in precipitation to
as high as 10,000 TU in places, with surface seawater concentrations
reaching 20-30 TU in the northern hemisphere.
The latitudinal distribution of weapons tritium delivery to the ocean
is characterized by mid-latitude maxima (near 45-50)
with about a five-fold asymmetry between northern and southern
hemisphere. The time history of surface delivery is a spike
for the northern hemisphere and more extended for the southern
The usefulness of tritium as a tracer is due to its time history
not monotonically increasing (i.e. the weapons source is no more)
which gives independent time information, the strong hemispheric asymmetry
in its delivery which is valuable in the study of cross-equatorial
flow and, finally, its nature as an ideal fluid tracer since, being
part of the water molecule, it is unaffected by biological and
chemical processes. The long-term evolution of its large-scale
distribution will provide much useful information about ocean
See Sarmiento (1988),
Broecker and Peng (1982), and
Broecker et al. (1986).
- Tritium Unit
- A unit defined as 10**18 times the atom ratio of
tritium to normal hydrogen.
- Acronym for Triangle Trans Ocean Buoy Network, a
a buoy for measuring surface meteorology and upper ocean data.
These Japanese moorings are used in the
TAO/TRITON array west of
- trochoidal wave
- See Gerstner wave.
- Acronym for Tropical Experiment.
- TROPIC HEAT
- Acronym for Tropical Pacific Upper Ocean Heat and Mass Budgets,
a process-oriented study within the TOGA
observing system for examining the processes controlling
SST in the equatorial eastern Pacific.
It was designed to explore the characteristics and dynamics of the mixing
in the equatorial Pacific Ocean in greater detail and to establish the
basis for realistic parameterizations of the mixing.
A two ship study was conducted southeast of Hawaii in November and
December 1984 in which intensive fine- and microscale observations
See Eriksen (1985) and
Heert et al. (1991).
- tropical cyclone
- A non-frontal, synoptic scale, low pressure system originating over
tropical or subtropical waters with organized convection and definite
cyclonic wind circulation.
- tropical depression
- A tropical cyclone with maximum
sustained winds of 33 knots or less near the center.
- tropical instability waves
- Waves that derive their energy from the large-scale, seasonally
varying zonal equatorial currents through shear instability
(and possibly through SST frontal instabilities).
They were first observed in the Pacific in 1977 in satellite
SST imagery, and have since been detected in ocean currents,
temperature and salinity fields, and in satellite altimetry data.
They typically appear as well-organized, cusplike features that
propagate westward with zonal wavelengths
of 800-2000 km and periods of 20-30 days.
They are seasonally and interannually modulated, being weakest
during the boreal spring and during the warm phase
These waves provide a significant source of drag on the
South Equatorial Current (SEC) and the
Equatorial Undercurrent (EUC).
They heat the cold tongue via large downgradient (i.e. equatorward)
eddy heat transports.
They can also affect the stability of the atmospheric boundary
layer, the distribution of cloudiness, latent heat fluxes,
and the distribution of nutrients and chemical species
in the eastern equatorial Pacific.
Instability waves have also been detected in the Atlantic during
the boreal summer. They potentially provide a large source
of aliased energy which can add noise contamination to
measurements of lower frequency signals.
See McPhaden et al. (1998).
- tropical SST paradox
- This refers to an apparent contradiction between tropical SSTs
as inferred from various proxy data and as calculated by the
present generation of computer models for past warm periods.
The measurements for
the Pliocene, Eocene
and Cenomanian suggest that tropical SSTs
were not significantly greater than those at present, while
model simulations for these times show significant differences.
See Crowley and North (1991).
- tropical storm
- A tropical cyclone with maximum
sustained winds of 34 to 47 knots near the center.
- The narrowest of the atmospheric layers, extending from the surface
of the Earth to about 10 km at the Equator and 6 km at the
poles near the 200 mbar level.
This layer contains about 80-85% of the atmosphere's total
mass and almost all of the water vapor and clouds. Temperatures fall with
height at the rate of about 0.5 F per 100 feet. It is bounded
above by the tropopause which varies
with latitude and season. This layer is characterized by strong
vertical mixing associated with latent heat effects and clouds.
- tropospheric aerosols
- See Haywood and Boucher (2000).
- truncation error
- That which occurs when a function, theoretically represented exactly
as the summation of an infinite (or otherwise bloody huge)
number of terms, is represented by a smaller subset of these terms.
The difference between the exact function and the function represented
by the finite number of terms is called the truncation error.
This is one of several kinds of errors inherent in representing
a continuous world discretely on computers.
- T-S curve
- See T-S diagram.
- T-S diagram
- A graph showing the relationship between temperature and salinity
as observed together at, for example, various depths in a water
column. A T-S diagram for a given station is typically
prepared by plotting a point for the temperature/salinity
combinations at a range of depths and then joining them
by straight lines in order of depth. The resulting line is
called the T-S curve.
Isopleths of constant density are often also drawn on the
same diagram as a useful additional interpretation aid.
In the ocean certain T-S combinations are preferred which
leads to the procedure of identification via the definition of
water types and
water masses and their distributions.
- T-S-t diagram
- An extension of the
T-S diagram concept to include
information about the temporal evolution of the properties
of ocean waters in specific areas. It is
created by plotting, on a standard T-S diagram, the
temperature and salinity of a given area at regular time
intervals (say, monthly or quarterly values).
- T-S-V diagram
- An extension of the concept of a
T-S diagram to display the distribution
of temperature and salinity in the world ocean waters in proportion
to their total volume. This is created by dividing
a T-S diagram into a grid of squares with each square containing
a number indicating the volume of water whose properties lie
within it. A 3-D graphic of the results can also be created
by replacing each number with a proportionally long vertical
bar. See Montgomery (1958) and
- Tsuchiya jet
- Narrow eastward currents in the Pacific that bracket the equator just below the
They form the poleward boundaries of the 13C equatorial
The northern jet begins west of 141E at 325 m depth, and the
southern jet near 155E at 300 m depth.
Both start 3 from the equator, then gradually diverge and shoal
to the east until they are 6 from the equator and 150 m below
the surface at 110W. The typical core speeds are 35 cm s,
and the transport 5-10 Sv each.
There is some evidence for a secondary southern jet south of the
main southern jet in the eastern Pacific.
These are also known as subsurface countercurrents (SCC).
One model of their dynamics considers a linear, vertically
diffusive model which simulates the Tsuchiya jets as lobes of
the Equatorial Undercurrent (EUC)
which are formed at the poleward edge of a broad diffusive equatorial
boundary layer (McPhaden (1984).
Downward vertical diffusion of cyclonic
is balanced by the poleward advection of
planetary vorticity within
the boundary layer, with the advection of planetary vorticity
balanced by vortex stretching
creating a pycnostad
outside of it.
The jets are the result of a geostrophic balance across the
An inertial jet model has the conservation of the
Bernoulli function and
combining with th eastward shoaling of the
tropical pycnocline to determine
See Tsuchiya (1972),
Johnson and Moore (1997) and
Rowe et al. (2000).
- Tsugaru Current
- A current flowing east from the
Japan Sea through the strait
between mainland Japan and Hokkaido and on into the Pacific Ocean.
This is also known as the
Tsugaru Warm Current.
The Tsugaru originates in the
Tsushima Current, which splits off from
the Kuroshio Current and enters the
Sea of Japan through Tshushima Strait
where it is modified before exiting through the
In summer and autumn, the Tsugaru tends to expand eastward and into
a small anticyclonic gyre as it meanders eastward past the
northern tip of Honshu, and then turns southward along the Sanriku
In winter and spring, it usually turns directly southward along
See Tomczak and Godfrey (1994) and
Talley et al. (1995).
- Tsugaru gyre
- See Nof and Pichevin (1999).
- Tsugaru Warm Current
- Another name for the
- A Japanese word meaning ``harbor wave''. This is often used
(along with the even more incorrect ``tidal wave'') as a name
for what is more correctly called a
seismic sea wave.
A true harbor wave is a type of seiche and
can be excited by, among other things, seismic sea waves.
Tsunami originally applied to all large waves including
storm surges but is now more or less
restricted to seismic sea waves, and has mostly supplanted both
seismic sea wave and tidal wave in the literature.
Tsunamis are primarily created by vertical movements of the
sea floor caused by tectonic activity. This causes rapid
vertical movements in the sea surface over a large area which leads to
the formation of
a train of very long period waves, with periods exceeding
one hour not unusual. Secondary mechanisms for tsunami formation
are landslides and volanic activity, with the effects of the
resultant waves more localized than those of the tectonic
variety which may travel across ocean basins.
See Camfield (1990).
- Tsushima Current
- A branch of the Kuroshio Current
that flows into the Japan Sea via
the Korea Strait. This brings in warm water which is
ultimately exported to the Pacific via a continuation of
the Tsushima called the
The Tsushima splits into two branches near 35 N when it
encounters the Tsushima Islands, with the western branch
following the Korea coast and eventually turning east to
join the Polar Front and the eastern branch closely following
the Japanese coast until it becomes the Tsugara Current.
The transport varies seasonally, with August transport
about 1.3 Sv (at up to 4 m/s) and January transport
only 0.2 Sv (below 0.1 m/s). Most of the increased August
transport passes through the western branch as the eastern
branch is weak year round. Both branches are prone to
major pathway shifts and the western branch tends to shed
large eddies where it separates from the Korean coast.
The western branch has also been called the
East Korea Current.
See Lie and Cho (1994) and Tomczak and Godfrey (1994).
- Abbreviation for Transient Tracers in the Ocean. This comprised
two separate studies: the TTO North Atlantic Study (TTO/NAS) and
the TTO Tropical Atlantic Study (TTO/TAS).
The 1981 North Atlantic Study (NAS) experiment cruise consisted
of seven legs and visited 250 hydrographic stations across the
North Atlantic in 200 days. About 9000 water samples were taken
for analysis of salinity, oxygen, and nutrients; 3000 samples
were taken for tritium analysis; and 1000 samples for
radiocarbon analysis. The
from the CDIAC.
- turbidity current
- See Johnson (1964).
- As defined by a subpanel of SCOR working group
69 in 1987:
Turbulence is a condition of fluid flow in which:
- each of the components of velocity and vorticity is irregularly
and aperiodically distributed in both space and time;
- energy is transferred between large and small scales where it
is dissipated; and
- there is diffusion of properties at a rate much in excess of the
molecular rates that would occur in a laminar flow with the same
average distribution of flow and scalar properties.
Kantha and Clayson (2000) list the characteristics of turbulent flows as:
- randomness, i.e. high irregularity in both time and space;
- intrinsic three-dimensionality;
- high vorticity, i.e. the deformation of fluid particles involves
- strong diffusivity, i.e. turbulent diffusivities of mass, momentum,
heat, etc. typically several orders of magnitude larger than molecular
- strong dissipation, i.e. energy is extracted from the mean flow
by turbulent shear stresses acting against the mean shear;
- instrinsic nonlinearity, i.e. it is the nonlinear terms in the
Navier-Stokes equations that effect the cascade of energy from large
eddies to small eddies on down the spectrum;
- a broad and red spectrum where energy is concentrated in larger
scales or lower wavenumbers;
- anisotropy of large scales, i.e. large scales are continuously being
oriented and elongated in the direction of the mean flow by the mean
strain rate; and
- loss of memory, i.e. initial conditions are quickly forgotten due to
the intense scrambling of the flow.
Small-scale, active turbulence is defined as a nearly isotropic,
eddy-like state of fluid motion where the inertial forces in the eddies
are larger than the buoyancy and viscous forces. It consists of
random motions, with Reynolds and
Froude numbers that exceed critical
values. The length scales of such three-dimensional turbulent
motion are smaller than about 0.6 and larger than about
11, where is the
Ozmidov length scale and
Kolmogorov length scale.
Small scale fluctuations that satisfy the first three requirements
but not those of active turbulence are sometimes described as
fossil turbulence, i.e. remnants
of previously active turbulence.
See McDougall et al. (1987) and
- turbulence kinetic energy (TKE)
- The energy contained within the turbulent portion of a flow.
- turbulent stress tensor
- See Reynolds stress tensor.
- Turner angle
- A quantity delineating the stability of a water column to double diffusion
and salt fingering.
It is given by:
where is a density ratio defined as:
where and are the coefficients of thermal
and saline expansion, and and the vertical
gradients of temperature and salinity. The angle obtained is
See Ruddick (1983).
- 45 to 90 - salt fingering occurs;
- -45 to 45 - double diffusion is not possible;
- -45 to -90 - diffusive convection occurs; and
- all other angles - the fluid is statically unstable.
- turnover time
- A time scale defined as the ratio
of the mass of a reservoir to the rate of its removal from
that reservoir. In the context of the climate this can be
seen as the total amount of carbon dioxide in the atmosphere
and its rate of removal via land and ocean processes.
- Acronym for Two-Way Acoustic Transmission Experiment.
See Worcester (1977).
- The Turbulence and Waves over Irregularly Sloping Topography Experiment
is a WHOI program to discover what dictates
the magnitude, frequency and spatial scales of internal waves in
continental slope regions.
The study area is on the continental slope of the North Atlantic
Ocean near Norfolk Canyon. The area is centered at
37.25N and 74.66 W and was chosen for the evenly
spaced topographic waves that run orthogonal to the slope.
In the deployment phase, planned to last from May 10 to June 8, 1998,
three Moored Profilers (MP) will
be deployed in a closely spaced array (about 500 m separation).
This should allow the assessment of horizontal internal wave scales.
High Resolution Profiler (HRP) dives will
also be made to quantify the smallest scale components of vertical
See the TWIST Web site.
- Abbreviation for tropical western Pacific.
- A tropical cyclone with maximum
sustained winds of 64 knots or more near the center.
- Tyrrhenian Sea
- One of the seas that comprise the western
basin of the
It is separated from the
Balearic Sea to the west by
Sardinia and Corsica and from the eastern basin by
It has a central abyssal plain along with some smaller
plains located witin slope basins. The central plain
is pierced by a large seamount that rises 2850 m above
the sea floor to within 743 m of the surface.
See Fairbridge (1966).