- Acronym for Ocean Observations Panel for Climate, a panel succeeding and
formed from the OOSDP. It is sponsored jointly
with WCRP, GOOS, and
The OOPC continues the design of the ocean observing system begun by
OOSDP, in addition to addressing:
- areas not considered by the OOSDP;
- prioritizing recommended elements;
- considering alternate sampling strategies; and
- assisting in making inventories of available data and products needed for
the GCOS/GOOS common module.
- Acronym for Ocean Observing System Development Panel, established in
1990 by the CCCO of
the Joint Scientific Committee (JSC) of the
The panel's task was to formulate a conceptual design of a long-term,
systematic observing system to monitor, describe, and understand
the physical and biogeochemical processes that determine ocean circulation
and the effects of the ocean on seasonal to decadal climate changes
and to provide the observations needed for climate predictions.
The panel published seven background reports and a final report in 1995 before
reforming as the OOPC. The reports were:
The final report is available online.
- The Role of Models in an Ocean Observing System - Neville Smith
- Scientific Rationale for Recommending Long-Term, Systematic
Ocean Observations to Monitor the Uptake of CO by the Ocean - Now and
in the Future - Liliane Merlivat and Alain Vezina
- Surface Conditions and Air-Sea Fluxes - Robert Weller and
Peter K. Taylor
- The Ocean Freshwater Cycle - Raymond Schmitt
- Monitoring Global Ocean Carbon Inventories - Douglas Wallace
- The Role of the Indian Ocean in the Global Climate System:
Recommendations Regarding the Global Ocean Observing
System - J. S. Godfrey et al.
- Sea Ice in the Global Climate System: Requirements for an
Ocean Observing System - Ian Allison and Richard E. Moritz
- Scientific Design for the Common Module of the Global Ocean
Observing System and the Global Climate Observing System: An Ocean
Observing System for Climate - OODSP Final Report
- Acronym for Océan PArallélisé, an ocean general circulation
model developed by the ECUME team at the
Laboratoire d'Océanographie Dynamique et de Climatologie
It is a primitive equation model applied to both regional and global
It can be interfaced with several sea ice models, a passive and
biogeochemical tracer model, and several AGCMs.
It also has adjoint and tangent linear models.
- Abbreviation for Optical Plankton Counter.
See Herman (1992).
- open boundary conditions
- See Palma and Matano (1998).
- Acronym for Observatoire Permanent de l'Atlantique Tropical.
- Operation Cabot
- A multiple-ship cruise to survey the Gulf Stream in 1950.
See Fuglister and Worthington (1951) and
- operational oceanography
- The activity of routinely making, disseminating, and interpreting
measurements of the seas and oceans so as to provide continuous
forecasts of the future condition of the sea for as far ahead as
possible, provide the most usefully accurate description of the present
state of the sea including living resources, and assemble climatic
long term datasets to provide data for the description of past
states as well as time series showing trends and changes.
This usually proceeds via the rapid transmission of observational
data to computerized data assembly centers. There they are processed
through numerical models to generate products for various applications.
- operator splitting
- In numerical ocean circulation modeling this is a technique
for splitting the fast and slow dynamics into separate subproblems.
When the partial differential equations governing large-scale
ocean dynamics are discretized to achieve numerical solutions,
dynamical phenomena with many temporal and spatial scales are
usually included in the discretized equations. Most prominent
in discretizations of the
primitive equations are
external and internal gravity waves, where the characteristic
wave speeds are, respectively, 200 m/s and 1-2 m/s.
The size of the discrete time step used to integrate the
equations is limited by the fastest motion that has to be
resolved, in this case the external gravity waves. One way
to get around this limitation is to separate the fast and slow
motions into separate subproblems. The fast external motions are
essentially 2-D due to approximate independence from depth, which
leads to the common option of obtaining the 2-D velocity field
from a vertical average of the horizontal velocity field in the
original 3-D equations.
This procedure can give rise to computational instabilities
since the operator splitting method is inexact except for the
case of a linearized flow with a horizontal bottom and a
In this case one solution is exactly independent of depth and
the horizontal velocity field obtained
corresponds exactly to the vertically averaged velocity.
However, if any of the restrictions are relaxed the fast and
slow motions can be mixed by variable bottom topography or
nonlinearities and can result in numerical instabilities if
an explicit method with a long time step is used to advance
the slow motion component in time. See
Higdon and Bennett (1996).
- optical depth
- See optical thickness.
- optical oceanography
- See Mobley (1994) and
Reynolds and Lutz (2001).
- optical thickness
- A measure of the attenuation of solar radiation by the atmosphere
that allows the convenience of considering as a single unit the losses
due to scattering and
absorption processes. The greater
the thickness, the greater the attenuation of incoming
This is also referred to
as the optical depth.
- Optimum Multiparameter Analysis (OMP)
- A tool to analyze the water mass mixture in a water sample by calculating
the contributions from the original
water masses (the source water masses) to
OMP is based on a simple linear mixing model that assumes all water
mass properties undergo the same mixing processes, i.e. their mixing
coefficients are identical.
This allows their distribution is space to be determined via a linear
set of mixing equations.
Mathematically speaking, OMP is an inversion of an overdetermined
system performed individually for each observation point.
The source water type contributions for each data point are obtained
by finding the best linear mixing combination in parameter space
defined by temperature, salinity, oxygen, nutrients and
other water mass properties that minimizes the resisuals in a non-negative
least squares sense.
- Acronym for Ocean Prediction Through Observation, Modeling, and
Analysis, a program that consisted of a lengthy set of surveys
of the eddy field in the
See Rienecker et al. (1985).
- Acronym for Organization of Persistent Upwelling Structures, a
program taking place in 1983 that studied the inner part of
a filament near Point Conception, California.
See Atkinson et al. (1986).
- Abbreviation for an isopycnic ocean
circulation model developed and used
at the DKRZ.
See Oberhuber (1993).
- Acronym for Oceanographic Remotely Controlled Automaton, a diesel
powered semi-submersible designed to survey water depths from 10 to
300 meters. This instrument was designed for the cost effective
collection of hydrographic and oceanographic data.
ORCA Web site.
- organic matter pump
- Then name given to the cycle of organic matter and nutrients in
the ocean. Since
exceeds respiration only in the
there is a net sink of CO2, phosphate and nitrate in the
euphotic zone and a net source in the
aphotic zone. Thus a downward
flux of organic matter and an upward flux of nutrients connects
the euphotic zone sink and the aphotic zone source of nutrients.
This has also been called the soft tissue pump, but the present
name was suggested in recognition of the possible role of dissolved
organic species in the transport cycle.
See Najjar (1991).
- orthobaric density
- A density variable empirically corrected for pressure.
It is constructed by first fitting compressibility (or sound speed)
computed from global ocean datasets to an empirical function of pressure
and in situ density (or specific volume). An exact Pfaffian differential
form is then obtained by replacing true compressibility by the best-fit
virtual compressibility in the thermodynamic density equation.
The orthobaric density has advantages as a vertical coordinate variable
for both descriptive and modeling purposes.
The advantages of this over the potential density include:
See de Szoeke (2000).
- a geostrophic streamfunction exists for the momentum equations transformed
to orthobaric density coordinates such that the gradients of orthobaric
density surfaces give precisely the geostrophic shear;
- a form of Ertel's potential vorticity can be defined whose evolution
equation contains no contribution from the baroclinity vector; and
- orthobaric density surfaces are invariant to the choice of reference
- Acronym for Oceanographic Systems for Chemical, Optical, and Physical
Experiments, a program addressing the need for next generation
autonomous near real-time long-term time series measurements in critical
regions of the world oceans.
The goal is to systematically obtain high resolution, long-term,
interdisciplinary oceanic data by improving the variety, quantity,
quality and cost-effectiveness of observations using a network of
strategically placed moorings.
O-SCOPE capitalizes on several recent technological advances (e.g.
pCO, pH and TAlk sensors, nitrate analyzers, spectral optical
sensors, and data telemetry) to meet this goal.
The scientific goals of O-SCOPE are:
- quantification of trends in biogeochemical and bio-optical variables
which can be caused by major changes in wind-driven and thermohaline
circulation and seasonal, interannual, and decadal changes in upper
ocean biogeochemical and bio-optical variability and carbon fluxes which
affect global climate; and
- monitoring trends in ``ocean health'' in the form of chemical, biological,
and optical indicators.
- Abbreviation for Ocean Surface Current Radar, a measuring system
that uses high frequency radio pulses to probe the ocean surface
to deduce near-surface currents. The shore-based system consists
of two units which are deployed several kilometers apart. Each
unit makes independent measurements of current speed along radials
emanating from its phased-array antennae system. The data are
then combined via UHF or telephone communication to produce
accurate vector currents, store them to disk, and display them
in near real time. Measurements can be made simultaneously at
up to 700 grid points at either 1 km or 250 m resolution. The
OSCR samples for about 10 minutes and then processes radar returns
for about 10 minutes to create a quasi-synoptic surface current
map every 20 minutes.
OSCR Web site.
- Abbreviation for Intergovernmental Committee for Ocean Science
and Living Resources, an IOC committee.
- Acronym for Ocean Thermal Energy Conversion, the use of the
temperature difference between surface and deep sea water to
generate electric power. This is done by taking a working
fluid with a low boiling point, turning it to vapor by heating
it up or depressurizing it, and then using the pressure of
the expanding vapor to turn a turbine. The liquid used may
be either the sea water or ammonia. The OTEC is called
open-cycle if the ocean water itself functions as the
refrigerant, transferring heat energy by changing between
the liquid and gaseous phases. It is called closed-cycle
if ammonia is used.
The idea was first propounded by a French engineer named
Jacques D'Arsonval in 1881, although it was a student of his
named Georges Claude who first tested the idea. Claude
used warm seawater to create a low pressure vacuum system,
i.e. an open-cycle system. D'Arsonval's original idea was to
use another fluid such as ammonia, i.e. a closed-cycle system.
At present the only operating OTEC plant is at the Natural
Energy Laboratory of Hawaii.
- Abbreviation for over-the-horizon radar, a type of radar
originally developed to detect military targets far beyond the
optical horizon. Radio waves in the 5 to 28 MHz range are reflected
from the ionosphere and reach up to 3500 km in one hop. Properties
of the ocean surface are extracted from the energy backscattered
from the ocean surface. Properties that can be measured
include surface wind direction, radial surface currents,
sea state, surface wind speed, and more.
OTH Web site.
- A research project whose goal is to improve the knowledge about
the hydrodynamics of the Straits of Otranto and the evaluate the
water and particulate fluxes across this strait at synoptic,
seasonal, and interannual time scales. This
MTP Core Project took place from Dec. 1993 to
OTRANTO Web site.
- otter trawl
- A device used in biological oceanography to trawl for
pelagic organisms. As opposed to the
beam trawl, the opening to this
is kept open not by a rigid rectangular frame but rather by
otter boards attached to either side of the net opening.
These boards are forced apart by the force of the water when
the trawl is towed and close when it is not being towed, an
eventuality convenient for retaining the organisms caught.
The open may be 20 to 26 m wide and the net up to 40 m in
See Sverdrup et al. (1942).
- outer sublittoral zone
- See circalittoral zone.
- overall Richardson number
- A dimensionless number
expressing the ratio of the removal of energy
by buoyancy forces to its production by the shear in a flow. It
is expressed by
where is the reduced gravity and
and are, respectively, length and velocity scales imposed
by the boundary conditions of the problem. The name comes from the
fact that this is an overall parameter describing a whole flow as
opposed to the gradient and
flux Richardson numbers.
See Turner (1973).
- OVERFLOW '60
- An ICES investigation of cold, sub-arctic,
deep water overspill into the North Atlantic Ocean from the
Iceland-Faroe Ridge. It was carried out from May 30 to
June 18 in 1960 under the leadership of J. B. Tait and
was an optimal coordination of 9 research ships in a small
region to reach a maximum of synoptic work. This experiment
is considered to be the starting point of current
measurements in deep water by self-recording anchored
- OVERFLOW '73
- An ICES expedition whose core period
of observation was between August 15 and September 15 in 1973.
The principal objective of this experiment was to describe
in detail the kinematic and dynamical processes which lead to
the renewal of the sub-Arctic bottom water of the northern
North Atlantic across the Iceland-Faeroe Ridge and the
Denmark Strait. This experiment, a follow-up to
OVERFLOW '60, consisted of
over 1700 hydrographic stations and 52 current meter moorings
as well as numerous XBTs, tide measurements and drogue tracking.
The chief scientist was J. Meincke of the University of Hamburg.
- A condition that can exist in strongly stratified
estuaries with net circulation out in the upper layer and
net circulation in in the lower layer. This limits the
amount of salt water available for mixing inside the
estuary. This condition begins as mixing proceeds within
the estuary by whatever processes are dominant. The mixing
causes more salt water to be added to the net circulation and
volume flow out of the estuary up to a critical condition
past which any more increased mixing has no further effect
on the discharge flow or the exiting salinity.
See Officer (1976).
- overturning potential energy
- In a stratified ocean, the locally averaged change in potential
energy produced by vertically rearranging the water column to
achieve static stability.
See McDougall et al. (1987).
- A tomography experiment planned by
IFREMER to study the variability in the
subpolar gyre from seasonal to decadal time scales. The goals are
to document the transformation of the subpolar mode water and the
amplitude of the thermohaline circulation.
OVIDE is planned to start in 2002 and includes hydrography,
profiling floats, and tomography. It will be based on four tomography
moorings that will be installed in the Western European Basin for
monitoring the heat content varability of the waters entering and
leaving the basin.
- A layer of maximum downward decrease in
- See Richards (1957).
- oxygen isotope analysis
- The use of stable oxygen isotopes to extract paleoclimatic information
from ice cores. The theoretical basis Bradley (1985)
of the method is that two paleoclimatically important
heavy isotopes (one containing deuterium and the other 18O)
have vapor pressures lower than that of pure H20.
Thus, evaporation leads to water vapor depleted in deuterium and
18O as well as a water body enriched in the same.
Further, condensation of the vapor preferentially removes even
more of these heavy isotopes, leaving the vapor even more
depleted in deuterium and 18O. Therefore, to a first approximation
isotopic concentration in the condensate can be considered as a
function of the temperature at which the condensation occurred,
although other considerations come into play.
A major use of this
method is to gauge the waxing and waning of glacial periods since
the deposition of large amounts of water on land in the form of
glaciers leaves the water enriched in and the water depleted of
the heavy isotopes.
- oxygen isotope ratio
- The ratio of oxygen-18 to oxygen-16, used as an indicator of
paleotemperatures since it is related to ocean temperature.
- A layer of relatively small vertical change in
oxyty as proposed in
- The concentration of dissolved oxygen. This was proposed as
an analogy to salinity in
Montgomery (1969). For a line of uniform oxyty, both
isoxygen and isooxygen have been proposed, with isooxygenic
as the adjectival form.
- Oyashio Current
- The western boundary current
of the subpolar gyre in the
North Pacific Ocean. Divergence in the center
of this gyre causes the Oyashio to carry cold water rich
in upwelled nutrients and full of marine life - hence the
meaning of the name as ``parent current''. The Oyashio is
formed by the confluence of the
Alaskan Stream and
the Kamchatka Current
west of the Kamchatka Peninsula at about 55 N. It flows
southward and splits into two paths called the First and
Second Oyashio Intrusion just south of Hokkaido, after which
the First Intrusion proceeds southward along mainland Japan
(Honshu) where it turns west at about 38 N
to rejoin the First Intrusion, which has proceeded more or
less directly south from the splitting point.
They merge at about 39 N and 145 E where the
southern boundary of the Oyashio defines the Polar Front.
This boundary and the northern edge of the Kuroshio maintain
their identities at least through the
Kuroshio Extension, although
it is not well known how much further east they continue to
be distinguishable and distinct from the broader eastward flow of
the North Pacific Current.
Thus the Oyashio forms the western and part of the southern limb
of the North Pacific subpolar gyre.
See Tomczak and Godfrey (1994).
- Oyashio Front
- A front delimiting the southern limit of subpolar waters in the
According to Talley et al. (1995):
The Oyashio Front is defined for our purposes as the southern limit
of waters that we characterize as ``subpolar'' based on their
temperature-salinity relation, and which are often referred to as
The Oyashio commonly meanders twice (the ``first and second intrusions'')
after leaving the coast of Hokkaido.
The meanders are separated by a warm core feature shown to originate
from northward movement of warm core rings produced by the
Kuroshio, possibly with interaction from westward propagating offshore
warm core rings, and with considerable modification due to winter
cooling and mixing with surrounding water. The warm core separating
the Oyashio ``intrusions'' is not necessarily always a closed ring.
The Oyashio is fairly barotropic, with little vertical shear, and has
apparently more transport than can be inferred from a shallow reference
The Oyashio Front, if defined as a water mass boundary, continues
eastward across the Pacific along 40-42N as the
Subarctic Front, forming the boundary between the subarctic and
modified subtropical water masses.
Much farther east, past the date line, the surface Subarctic Front
and the deeper front that forms the northern boundary of the subtropical
water become separated, with the surface front found farther
See Talley et al. (1995).
- Ozmidov scale
- An important length scale in stratified flow representing the vertical
length scale at which the buoyancy force is of the same order of
magnitude as the inertial forces.
This is expressed as:
where is the kinetic energy dissipation rate and
the buoyancy frequency.
The Ozmidov scale is the largest that can overturn, i.e. buoyancy
has only a minor effect at smaller scales but dominates at larger ones.
Overturning can occur at scales greater than if
internal waves are present, however, with
the buoyancy scale used instead of the
Ozmidov scale if vertical velocity fluctuations due to internal waves
are small compared to those due to turbulence.
This scale varies from a few cm in the
thermocline to several hundred meters
in weakly stratified and/or highly energetic flows.
See McDougall et al. (1987).