- Acronym for the Ocean-Atmosphere Carbon Exchange Study, a program
designed to gain a predictive understanding of the magnitude of
the atmospheric carbon dioxide that is ultimately dissolved in the
ocean and removed from the atmosphere for a period of time.
- Acronym for Ocean-Atmosphere Materials Exchange.
- Acronym for the Office of Oceanic and Atmospheric Research, the
primary research and development unit of NOAA.
It conducts and directs research programs in coastal, marine, atmospheric
and space sciences through its own laboratories and offices as well
as through networks of university-based programs throughout the
- Acronym for Optical-Acoustic Submersible Imaging System, an instrument
developed for 3-D acoustic tracking of zooplankton with concurrent
optical imaging to verify the identity of the insonified organisms.
OASIS also measures in situ target strengths of freely swimming
zooplankton and nekton of known identity and 3-D orientation.
The system consists of a 3-D acoustic imaging system (Fish TV), a sensitive
optical CCD camera with red-filtered strobe illumination, and various
ancillary oceanographic sensors.
See Jaffe et al. (1998).
- Abbreviation for Ocean/Air Exchange of Trace Compounds, a
program whose goal was to determine the atmospheric mixing
ratio of HCFC-22 and its partial pressure in surface waters
of the Western Pacific Ocean and to assess the possible
existence of an oceanic sink for this compound. This cruise
took twelve weeks aboard the RV John V. Vickers in 1992,
beginning at Long Beach, California and ending at
Noumea, New Caledonia.
- Abbreviation for oceanic surface boundary layer, one of the two types
- obligate chemotroph
- A species of phytoplankton that
has no photosynthetic pigments and cannot photosynthesize, as
- Also called the obliquity of the ecliptic, this term is used to denote the tilt
of the earth's axis with respect to the plane of the earth's orbit.
This is one of the three main orbital perturbations (the other two
being eccentricity and
precession) involved in
the Milankovitch theory and as
such varies from about 22 to 25. at a period of about 41,000 years.
Obliquity perturbations tend to amplify the seasonal cycle in the high
latitudes of both hemispheres simultaneously, with the effect
small in the tropics and maximum at the poles.
See Williams (1993).
- Abbreviation for Optical Backscattering Meter, an instrument
built by Downing Associates and used
to obtain in-situ measurements of light scattering in sea water.
This measurement also provides a crude measure of the particle
abundance in the water.
The instrument works by projecting a beam of light into the
water and measuring the amount of light scattered back to a
detector place next to the source.
The LSS is a similar instrument.
- Acronym for Ocean Color Algorithm Validation Experiment, a
part of POCEX.
- Acronym for the Ocean Circulation and Climate Advanced Modelling
Project, a project whose aim is to build a high resolution model
of the world ocean. The OCCAM model is a primitive equation
model of the global ocean based on the GFDL MOM version of
the Bryan-Cox-Semtner ocean model with the addition of
a free surface and improved advection schemes. It uses a regular
latitude-longitude grid for the Pacific, Indian and South
Atlantic Oceans and a rotated grid for the Arctic and North
Atlantic Oceans to overcome the singularity found at the North
Pole in other models. The two grids are connected with a channel
model through the Bering Strait.
- Abbreviation for Ocean Carbon Cycle Model.
- Abbreviation for Ocean Chemistry Division, one of four scientific
research divisions within
NOAA's AOML. Its work includes projects
important in assessing the current and future affects of human
activities on the coastal, deep ocean and atmospheric environment.
- Acronym for Ocean Colour European Archive Network, a project of
CEC and ESA established in 1990. The aim of the project was to
generate a data base of CZCS data for
the European seas and to set up the scientific tools needed for
its exploitation. OCEAN processed about 25,500 CZCS images at
various levels in its five years of activity and generated an
archive of about 400 GB of data from this processing.
Some of the processed images are available online.
- Acronym for Ocean Information Center, a data center that maintains
information on WOCE,
TOGA, research ships and cruise
schedules, and other oceanographic information sources.
- oceanic expeditions
- The deep-sea expeditions that have taken place through the history
of ocean sciences have been grouped into four eras:
- Era of Exploration (1873-1914)
- Era of National Systematic and Dynamic Ocean Surveys (1925-1940)
- Era of New Marine Geological, Geophysical, Biological and Physical
- Era of of International Research Cooperation (1957-Present)
The Era of Exploration is considered to have begun - along with
modern oceanography - with the British
Challenger expedition from 1873-1876.
The era was characterized by widely-spaced stations alongs isolated
profiles, and the combined results of several such expeditions
provided a first overall picture of the bathymetry, stratification and
circulation of the water masses and conditions for life in the deep
Other significant expeditions in the era included the German
Gauss (1901-1903) and
Deutschland (1911-1912) expeditions;
Blake (1877-1886) and
Albatross (1887-1888) expeditions;
Vitiaz (1886-1889) expedition; the
Hirondelle and Pricesse Alice expeditions of Monaco (1888-1922);
Michael Sars (1904-1913) and
Armauer Hansen (1913-Onward) expeditions.
These were single, long-term expeditions on large vessels
until the Scandinavian
school pioneered the use of smaller vessels for more systematic
research, e.g. with the Armauer Hansen.
The Era of National Systematic and Dynamic Ocean Surveys was
initiated in 1925-1927 by the German Atlantic Expedition
on the RV Meteor. This expedition took closely spaced
measurements at standard intervals all the way to the sea floor
along fourteen latitudinal cross-sections of the Atlantic Ocean
between 20N and 65S.
This stimulated other nations to undertake similar expeditions, e.g.
the Dutch Willebrord Snellius Expedition (1929-1930) in the East Indian seas,
the British Discover Expeditions (since 1930) mostly in the
Antarctic oceans, the
American Atlantis Expeditions (since 1931) mostly in the North Atlantic,
the Danish Dana II (1928-1930) around the world expedition,
the Carnegie (1928) and Ryofu Maru and E. W. Scripps (since 1937) Pacific
Ocean expeditions, the quasi-synoptic survey of the Gulf Stream northwest
of the Azores by the Altair and Armauer Hansen in 1937, and
the Russian icebreaker Sedov initiating research in the North Polar Sea
See Wust (1964).
- Oceanic Peru Current
- Another name used for the Peru Current.
- Oceanic Polar Front
- See Polar Front.
- See bathythermograph.
- ocean heat transport
- See Bryan (1982) and Covey and Barron (1988).
- ocean modeling
- See McWilliams (1996).
- Living upon the high seas as opposed to living in coastal
waters, i.e. neritic.
- More later.
- oceanography history
Brekhovskikh et al. (1991),
Sears and Merriman (1980) and
- Oceanography Society
- A society founded in 1988 to disseminate knowledge of
oceanography and its application through research and education,
to promote communication among oceanographers, and to provide
a constituency for concensus-building across all the
disciplines of the field. They also publish a magazine called,
strangely enough, "Oceanography".
- ocean optics
- See optical oceanography.
- Ocean Storms Experiment
- A measurement program taking place from August 1987 to June 1988
that focused on the interactions of atmospheric forcing,
mixed layer dynamics and inertial motions, with the aim of improving
understanding of upper ocean response to atmospheric forcing.
The experiment took place in the autumn in the northeast Pacific,
and was concentrated just south of the normal storm track since
historical data suggested that it would be a place of rapid mixed
layer deepening and strong, storm-forced inertial currents.
It was also an area where a low level of mesoscale eddy energy
minimized advection and the interaction of eddies and inertial
See D'Asaro (1995).
- ocean stratosphere
- The lower layer of the ocean as defined by Defant in 1928.
The stratosphere is a sluggish, cold layer which is
homogeneous vertically and horizontally in its basic
properties. It is a region of slow exchanges.
See Defant (1961), Ch. XIX and
- ocean troposphere
- The upper layer of the ocean as defined by Defant in 1928.
The troposphere is a region of relatively high temperature
where there are strong vertical and horizontal variations
of properties. It is a zone of perturbations and strong
See Defant (1961), Ch. XX and
- ocean turbulence
- Turbulence in the ocean and atmosphere is chiefly involved with
the roles of momentum transport and scalar mixing.
In the former role, turbulent motions behave somewhat analogously
to molecular viscosity in reducing the differences in velocity
between different regions of flow.
Scalar mixing is the homogenization of fluid properties such as
temperature by random molecular motions, with mixing rates proportional
to spatial gradients. These gradients are greatly amplified by the
stretching and kneading (i.e. stirring) of fluid parcels by
Most classical research results about turbulence are based on
the assumptions of homogeneity, stationarity and isotropy in
each of which reflects a symmetry in space or time.
Turbulence in geophysical flows, or geophysical turbulence, is
usually modified by phenomena such as shear, stratification and
boundary proximity, each of which breaks one or more of the
classical symmetries and therefore invalidates or greatly modifies
that which can be deduced or transferred from classical results.
Shear breaks the symmetries of homogeneity and isotropy by deforming
turbulent eddies, with the resulting anisotropy allowing the eddies
to exchange energy with the background shear via the mechanism of
Reynolds stresses, i.e. they allow
the turbulence to transport momentum.
If this transport is counter to the direction of the shear flow, energy
is transferred from the flow to the disturbance. This mechanism
represents one of the most common generation mechanisms for
geophysical turbulence, with perhaps the most well known example
Stratification leads to buoyancy forces, which break flow symmetry
by favoring the direction in which the gravitational force acts.
Buoyancy effects can either force (the case of unstable
density stratification) or damp (the case of stable stratification)
turbulence. In the ocean, surface cooling or evaporation - both of
which increae the density of the surface layer - cause
unstable stratification which results in convective turbulence.
When the stratification is stable, fluid parcels displaced from
equilibrium do not convect but rather oscillate vertically at
the buoyancy frequency, i.e.
we have internal gravity waves.
If the stratification is strongly stable, turbulent motions become
in effect two-dimensional, with the turbulent motions taking place
in horizontal surfaces that undulate with the passage of internal
Three-dimensional turbulence is possible in moderately stable
stratification, although its structure is modified by the buoyancy
effects. The suppression of vertical motion inhibits the energy
transfer from the background shear flow.
The relative importance of stratification and shear depends on
the relative magnitudes of the vertical gradient of the shear (S) and
the buoyancy frequency (N), i.e. if the former is greater
turbulence is amplified, if the latter dominates it is suppressed.
Key overturning length scales for this situation are the
buoyancy scales, depending on whether
internal waves are present.
The distinction between stirring and mixing in stably stratified
turbulence is critical. Stirring is the advection and deformation
of fluid parcels by turbulent motions, while mixing involves changes
in the scalar properties of the parcels, i.e. mixing can only be
achieved via molecular diffusion. In stable stratification, changes
in the density field due to stirring are reversible, but mixing is
The majority of turbulent mixing in the ocean takes place near
boundaries, i.e. the ocean bottom and surface as well as lateral
obstacles to the flow.
Such boundaries obviously suppress perpendicular movement, thus
breaking both the isotropy and homogeneity symmetries.
If there is any motion, the fact that the velocity must be zero
at the boundary sets up a shear leading to the formation of a turbulent
The flexibility of the surface boundary leads to such phenomena as
surface gravity waves and
Langmuir cells, which contribute greatly
to upper ocean mixing and therefore air-sea fluxes of momentum,
heat and chemical species.
See Gargett (1989) and
Caldwell and Moum (1995).
- ocean water cycle
- The distribution of evaporation and precipitation over the ocean is
the ocean component of the global water or hydrological cycle.
Since the ocean covers 70% of the Earth's surface and contains
97% of its free water, it plays a dominant role in this cycle.
The terrestrial component of the cycle is understandably much more
well understood, although the estimated 86% of global evaporation and
78% of precipitation that occur over the ocean should be better
understood given the dramatic consequences small changes in the ocean
cycle could have over land.
The ocean water cycle also directly impacts the
a key component of the climate system, especially for variations
on decadal to millennial time scales.
The poleward transport of heat by the atmosphere and ocean
moderates high latitude temperatures, with meridional ocean heat
transport about equal to that of the atmosphere.
A large portion of the ocean heat transport in the northern hemisphere
is carried by the thermohaline overturning cell in the Atlantic which, if
disrupted, has major consequences for high and mid-latitude continental
climate. This cell is thought to have collapsed in the past due to
what is called the
halocline catastrophe, where
the ocean surface salinity is decreased sufficiently via enhanced
freshwater input to cause deep water formation processes to cease.
The primary factors determining the ocean surface salinity are the
distribution of evaporation, precipitation, ice and continental runoff,
so it behooves us to adequately understand the ocean water cycle.
Some major features of the ocean water cycle are:
- rainfall dominating over evaporation within the
ITCZ in the tropics;
- an excess of evaporation over most of the subtropics except for
the SPCZ, a band of net precipitation trending to
the southeast away from the western equatorial Pacific;
- dominance of precipitation in subpolar latitudes, more so in the North
Pacific than the North Atlantic;
- the amplitude of the water cycle is reduced at high latitudes by the
low water vapor capacity of a cold atmosphere;
- the processes of freezing, melting and transport of ice are significant
factors in the water cycle at high latitudes;
- patterns of E-P are generally strongly zonal, except for in the
North Indian Ocean where evaporation dominates in the Arabian Sea and
precipitation in the Bay of Bengal.
A necessary consequence of regional differences in evaporation and
precipitation over the ocean is compensating flows within the ocean
Water must be transported into evaporation zones and away from
precipitation zones. For instance, there is an excess of precipitation
in the North Pacific, especially in the eastern tropical Pacific, and
a dominance of evaporation in the Atlantic. This difference is
thought to be maintained by water vapor transport across Central
America as well as the lack of any similar transport into the Atlantic
See Schmitt (1995).
- Abbreviation for Ocean Color Imager, an
all-refractive spectral radiometer with six spectral bands spanning
from visible to near infrared.
- Abbreviation for Ocean Carbon-Cycle Model Intercomparison Project, a
GAIM project to compare
the results of global 3-D ocean models being
used to study the ocean's carbon cycle.
- Acronym for Outer Continental Shelf Environmental Assessment
Program, a NOAA/BLM project.
- Acronym for Ocean Tomography Operational Package and Utilization
Support, a project whose goals are:
- to turn tomography into a routine, affordable, and operational
tool for ocean research, monitoring and forecasting for even
- to increase the acceptance and usage of tomography results as
routine data; and
- to enable small and medium enterprises to carry out operational
applications and provide instrument services in tomography.
- Acronym for Ocean Colour Techniques for Observation, Processing and
Utilization Systems, a CEC project.
- Acronym for Ocean Color and Temperature Scanner, a visible and
infrared multispectral radiometer designed to measure global
ocean color and sea surface temperature with high sensitivity.
It will show the amount of chlorophyll and dissolved
substances in the water along with the temperature distribution.
The data will also be used for determination of ocean primary
production and the carbon cycle and for monitoring ocean
conditions for fisheries and environmental needs. It is a successor
to the CZCS.
OCTS scans the Earth's surface using a rotating mirror in the
direction perpendicular to the satellite flight path.
It has eight bands in the visible and near-infrared region and four
bands in the thermal region, with the bands determined by the
spectral reflectance characteristics of the objects being
observed as well as atmospheric window and correction considerations.
The spatial resolution is about 700 meters with a swath width of
about 1400 km on the ground, and the orbit allows the same area
on the ground to be observed every three days.
This instrument will fly on the ADEOS
- Acronym for Ocean Data Acquisition System, a NOAA
project to study phytoplankton blooms in the Chesapeak Bay using
aircraft remote sensing from 1990 to 1996.
ODAS is a relatively simple ocean color instrument
developed in the mid-1980s at the NASA GSFC. It
consists of 3 radiometers in the blue-green region of the visible
spectrum that measure radiance leaving the water at
460, 490 and 520 nm, a spectral region sensitive to changes in
The measurements were made in low altitude (150 m) surveys using
a De Havilland Beaver aircraft, with over 200 flights made during
- Abbreviation for the Ocean Drilling Program, which conducts
basic research into the history of the ocean basins and the overall
nature of the crust beneath the ocean floor using the scientific
drill ship, JOIDES resolution. This was originally called the
- Abbreviation for ozone depletion potential.
- Acronym for Ocean Ecology: Understanding and Vision for Research, a
workshop for biological oceanographers and
marine ecologists held at Keystone, Colorado from March 1-6, 1998.
The goal was to develop an assessment of the field and an attempt to
provide a vision of what it could become over the next few decades.
Similar workshops were held at the time for
physical oceanography (sf APROPOS),
ocean chemistry (FOCUS) and
marine geology and geophysics (FUMAGES).
- The comparatively flat portion of a beach profile extending
seaward from beyond the breaker zone
to the edge of the continental shelf.
See Komar (1976).
- Abbreviation for Office of Oceanographic Facilities and
Support, a NSF office.
- Acronym for the Office of Global Programs, a program
office of NOAA.
The OGP leads the NOAA Climate and Global Change (C&GC) Program, and
assists NOAA by sponsoring focused scientific research aimed at
understanding climate variability and its predictability.
- Abbreviation for Osservatorio Geofisico Sperimentale, a geophysical
research institution located in
Trieste, Italy. The OGS has a Department of Oceanology and
Environmental Geophysics that performs research in physical
ocenaography, especially in the Adriatic Sea, Eastern Mediterrean,
Sicily Channel, and the Messina and Otranto Straits.
- Acronym for Ocean Heat Transport EXperiment, a Japanese program.
- Okhotsk Sea
- A marginal sea on the northern rim of the Pacific Ocean
centered near 55 N and 150 E.
It is bounded by the Siberian coast to the west and north, the
Kamchatka Peninsula to the east, and the Kurile Islands to the
south and southeast. It covers an area of about 1,600,000 km,
has an average depth of about 860 m, and a maximum depth of
3370 m in the Kurile Basin. It is connected to both the
Pacific Ocean and the Japan Sea via narrow passages, the
most important ones being (for the former) the Boussole
Strait (2318 m) and the Kruzenshtern Strait (1920 m) and
(for the latter) the Tatarskyi Strait (50 m) and the
Soya (or La Perouse) Strait (200 m).
The bathymetry consists of a moderately broad shelf, defined by
the 200 m contour, to the north which gradually steepens to
depths greater than 3000 m to the south. Two shallow bays,
the Shelikov and the Penzhinskaya, occur at the northeastern
boundary. Depths shallower than 200 m extend about 100 km off
the coast of the Kamchatka Peninsula and Sakhlain Island.
From there the bathymetry deepens to a braod area with depths
between 1000 and 2000 m in the central part of the sea.
The slope steepens near the Kuril Basin, with depths changing
from 1000 m to mean depths of 3300 m in the Basin.
The circulation of the Okhtotsk Sea has been summarized by
Preller and Hogan (1998), and is presented here in slightly
The predominant pattern of circulation is cyclonic.
Flow from the
East Kamchatka Current (EKC) in the
Pacific enters the sea predominantly through Kurzenshtern Strait,
with smaller amounts of Pacific water entering through several of the
other straits to the north.
A two-layer flow exists in Kruzenshtern Strait, with a northerly
inflow in the upper 50 m with velocities up to 1.0 knot.
There is a southerly flow of 2.5 Sv between 100 and 200 m.
Strong variability exists on time scales of less than day, with the
flow dominated by a strong tidal component, and with the geostrophic
component being of secondary importance.
The flow entering through the Kruzenshtern and northern straits turns
northward. The transport through the northernmost straits flows along the
Kamchatka Peninsula. Flow through the Kurzenshtern Strait splits with
part flowing north and west an dpart flowing along the Peninsula.
The current continues its cyclonic motion through the shallow
Shelikov and Penzhinskaya Bays.
Upon exiting the bays, the flow moves westward across the northern
part of the sea.
It is not known whether this flow is along the shallow northern shelf
or in the deeper water just beyond the shelf.
The continuation of the cyclonic circulation to the south is called the
East Sakhalin Current, which may be weak or
absent in summer.
It is stronger in winter, extending farther south along the Sakhalin
In the southwestern part of the Okhotsk Sea, water originating from the
Tshushima Current in the
Japan Sea enters via the Soya Strait and
flows southeast along the northern Hokkaido coast as a narrow
boundary current called the
This current varies seasonally, with maximum flow in the summer (around
1 knot) and temperatures ranging from 12-19C. In winter,
the speed diminishes by a factor of two when the region north of
Hokkaido is covered by sea ice.
The Soya Current continues to flow past Hokkaido and turns to
the northeast, with part exiting through the southern straits,
part flowing along the Kuril Islands at least to Etorofu, and
part flowing into the central Kuril Basin.
The circulation of the Kuril Basin consists of a large, anticyclonic
gyre and two anticyclonic eddies.
The eddies appear each year, developing in summer and decaying in winter.
The Okhotsk Sea water leaves the basin and flows into the north Pacific
Ocean through the Bussol Strait and several shallower straits in the
southern half of the Kuril chain.
A two-way flow has also been calculated for the Bussol Strait, with
a southerly outflow of 6.4 Sv for the upper 600 m and a northerly
inflow of 4.3 Sv below 600 m. The outflow is found in the upper layers
of the western side, and the inflow in the eastern half down to depths
of 1700 m.
See Zenkevitch (1963),
Tomczak and Godfrey (1994),
Freeland et al. (1998),
Preller and Hogan (1998),
You et al. (2000) and
Polyakov and Martin (2000).
- Oleander Project
- An multiyear program to monitor the structure and variability of
the Gulf Stream.
This is accomplished by a container vessel Oleander operating
on a weekly schedule between Port Elizabeth, New Jersey, and Hamilton,
Bermuda. It is equipped with a 150 kHz narrowband acoustic
Doppler current profiler (ADCP) to measure currents from the surface
to about 300 m depth. A major objective of the program is to study
the annual cycle and interannual variations in velocity structure
and transport by the Gulf Stream.
See Rossby and Gottlieb (1998).
- Abbreviation for Ocean and Lake Levels Division, a part of
the NOS section of NOAA.
It is responsible for the management of the U.S. National
Water Level Program (NWLP), the foundation of which is the
National Water Level Observation Network (NWLON).
OLLD Web site.
- Ombai Strait
- One of the three main passages for waters in the
Indonesian archipelago to flow into the Indian Ocean.
The Ombai Strait between Alor and Timor Islands is 3250 m deep, and has
an observed mean westward volume transport of 51 Sv.
There is a weak annual period in the upper layer flow, and
a semi-annual period at depth.
See Molcard et al. (2001).
- omega equation
- More later.
- Acronym for Ocean Margin EXchange project, a component of the
MAST program. This project aims to study
the biogeochemical fluxes and processes across the European
continental shelf break facing the North Atlantic.
See van Weering (1998).
- Acronym for Ocean Model and Information System for APEC Region,
a project of the Marine Resource Conservation Working
Group sponsored by APEC and EPA of Chinese Tapei.
OMISAR Web site.
- Acronym for Ocean Mixed Layer ExperimenT,
a Japanese research program
taking place on the vessel Hakuho Maru from Jan. 11-Feb. 5, 1991.
- Abbreviation for
Optimum Multiparameter Analysis.