Oa-Om

OACES

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.

[http://www.aoml.noaa.gov/ocd/oaces/]

OAMEX

Acronym for Ocean-Atmosphere Materials Exchange.

OAR

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 country.

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

OASIS

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).

OAXTC

Abbreviation for Ocean/Air Exchange of Trace Compounds, a NOAA CMDL 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.

[http://www.cmdl.noaa.gov/hats/ocean/oaxtc92/oaxtc92.html]

OBL

Abbreviation for oceanic surface boundary layer, one of the two types of PBL.

obligate chemotroph

A species of phytoplankton that has no photosynthetic pigments and cannot photosynthesize, as opposed to facultative chemotrophs.

obliquity

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$^\circ$. 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).

OBS

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.

OCAVE

Acronym for Ocean Color Algorithm Validation Experiment, a part of POCEX.

OCCAM

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.

[http://www.soc.soton.ac.uk/JRD/OCCAM/welcome.html]

OCCM

Abbreviation for Ocean Carbon Cycle Model.

OCD

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.

[http://www.aoml.noaa.gov/ocd/]

OCEAN

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.

[http://me-www.jrc.it/OCEAN/ocean.html]

OCEANIC

Acronym for Ocean Information Center, a data center that maintains information on WOCE, TOGA, research ships and cruise schedules, and other oceanographic information sources.

[http://diu.cms.udel.edu/]

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 Methods (1947-1956)
• 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 oceans. Other significant expeditions in the era included the German Gazelle (1874-1876), National (1889), Valdivia (1898-1899), Gauss (1901-1903) and Deutschland (1911-1912) expeditions; the U.S. Blake (1877-1886) and Albatross (1887-1888) expeditions; the Russian Vitiaz (1886-1889) expedition; the Hirondelle and Pricesse Alice expeditions of Monaco (1888-1922); the Norwegian Fram (1893-1896), 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 20$^\circ$N and 65$^\circ$S. 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 in 1938. See Wust (1964).

Oceanic Peru Current

Another name used for the Peru Current.

Oceanic Polar Front

See Polar Front.

oceanograph

See bathythermograph.

ocean heat transport

See Bryan (1982) and Covey and Barron (1988).

ocean modeling

See McWilliams (1996).

oceanic

Living upon the high seas as opposed to living in coastal waters, i.e. neritic.

oceanography

More later.

oceanography history

See Borgese (1992), Brekhovskikh et al. (1991), Deacon (1971), Deacon (1978), Deacon (1997), Herdman (1923), Idyll (1969), McConnell (1982), Mills (1989), Schlee (1973), Schott (1987), Sears and Merriman (1980) and Thomasson (1981).

[http://scilib.ucsd.edu/sio/archives/histoceanogr/mills-handlist.html]

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".

[http://www.tos.org/]

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 currents. 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 Tchernia (1980).

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 currents. See Defant (1961), Ch. XX and Tchernia (1980).

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 turbulence.

Most classical research results about turbulence are based on the assumptions of homogeneity, stationarity and isotropy in three-dimensional flow, 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 being the Kelvin-Helmholtzinstability.

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 gravity waves. 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 Ozmidov and 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 irreversible.

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 boundary layer. 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 thermohaline circulation, 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 and atmosphere. 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 from Africa. See Schmitt (1995).

[http://earth.agu.org/revgeophys/schmit01/schmit01.html]

OCI

Abbreviation for Ocean Color Imager, an all-refractive spectral radiometer with six spectral bands spanning from visible to near infrared.

[http://www.oci.ntou.edu.tw/en/oci/]

OCMIP

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.

[http://www.ipsl.jussieu.fr/OCMIP/]

OCSEAP

Acronym for Outer Continental Shelf Environmental Assessment Program, a NOAA/BLM project.

OCTOPUS

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 non-specialist users;
• 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.

[http://www.ifremer.fr/sismer/program/octopus/]

OCTOPUS

Acronym for Ocean Colour Techniques for Observation, Processing and Utilization Systems, a CEC project.

OCTS

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 mission.

[http://www.eoc.nasda.go.jp/guide/satellite/sendata/octs_e.html]

ODAS

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 chlorophyll concentrations. The measurements were made in low altitude (150 m) surveys using a De Havilland Beaver aircraft, with over 200 flights made during the program.

[http://noaa.chesapeakebay.net/odas_sas.html]

ODP

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 DSDP.

[http://www-odp.tamu.edu/]

ODP

Abbreviation for ozone depletion potential.

OEUVRE

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).

[http://www.joss.ucar.edu/joss_psg/project/oce_workshop/oeuvre/]

offshore

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).

OFS

Abbreviation for Office of Oceanographic Facilities and Support, a NSF office.

OGP

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.

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

OGS

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.

[http://www.ogs.trieste.it/]

OHTEX

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$^\circ$ N and 150$^\circ$ 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 modified form:

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 Island coast.

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 Soya Current. This current varies seasonally, with maximum flow in the summer (around 1 knot) and temperatures ranging from 12-19$^\circ$C. 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).

OLLD

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). See the 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 5$\pm$1 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.

OMEX

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).

[http://www.pol.ac.uk/bodc/omex.html]

OMISAR

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. See the OMISAR Web site.

OMLET

Acronym for Ocean Mixed Layer ExperimenT, a Japanese research program taking place on the vessel Hakuho Maru from Jan. 11-Feb. 5, 1991.

OMP

Abbreviation for Optimum Multiparameter Analysis.