- Abbreviation for Antarctic Bottom Water.
- Abbreviation for Antarctic Circumpolar Water.
- Abbreviation for
Antarctic Intermediate Water.
- Abbreviation for
Antarctic Surface Water.
- Abbreviation for Arctic Acoustic Transmission Experiment,
a project of the APL at the University
of Washington School of Oceanography.
- An instance of the
phenomenon in Nagasaki Bay.
See Hibaya and Kajiura (1982).
- Abbreviation for
- 1. Abbreviation for
atmospheric boundary layer.
2. Abbreviation for
airborne backscatter lidar.
- Abbreviation for Acoustic Backscatter Probes.
- absolute humidity
- The ratio of the mass of water vapor in a sample of moist air to
a unit volume of the sample. It is expressed in grams per
cubic meter and also called the vapor
- absolute vorticity
- The sum of the
relative vorticity ()
planetary vorticity, i.e.
- In radiation transfer, the fraction of incoming radiation that
is absorbed by a medium.
The sum of this, the transmittance,
and the reflectance must equal unity.
- A process by which incident radiation is taken into a body and
retained without reflection or transmission. It increases either the
internal or the kinetic energy of the molecules or atoms composing
the absorbing medium.
- absorption band
- In atmospheric radiative transfer,
a collection of absorption lines
in a particular frequency interval.
- absorption line
- In atmospheric radiative transfer,
a discrete frequency at which an energy transition of an atmospheric
gas occurs due to the absorption of incident solar radiation.
The line width depends on broadening processes, the most important
of which are natural,
pressure (also known as collision), and
- See Arctic Bottom Water.
- abyssal hill
- Small hills found only in the deep sea which rise from the
ocean basin floor with heights ranging from 10 to over 500 feet
and widths from a few hundred feet to a few miles.
They are found along the seaward margin of most
abyssal plains and originate
from the spreading of mid-ocean ridges. As such, they usually
form two strips parallel to mid-ocean ridges. They generally
decrease in height as one traverses away from the ridges as
they gradually become covered with sediment and are replaced
by abyssal plains.
See Fairbridge (1966).
- abyssal plain
- Flat areas of the ocean basin floor which slope less
than 1 part in 1000. These were formed by
which covered the preexisting topography.
Most abyssal plains are located between the base
of the continental rise
and the abyssal hills.
The remainder are trench abyssal plains that lie in the
bottom of deep-sea trenches. This latter type traps all
sediment from turbidity currents and prevents abyssal
plains from forming further seaward, e.g. much of the
Pacific Ocean floor.
See Fairbridge (1966).
- abyssal zone
- This originally meant (before the mid-1800s) the entire depth
area beyond the reach of fisherman, but later investigations led
to its use being restricted to the deepest regions with a uniform
fauna and low temperatures. Thus it was distinguished from
the overlying bathyal or archibenthal zone with more varied
fauna and higher temperatures. Eventually an underlying
hadal zone was defined for areas
in trenches and deeps below 6000-7000 m depth.
The upper boundary of the abyssal zone
ranges between 1000-3000 m, with the position of the
4 C isotherm generally considered the demarcation line.
It is the world's largest ecological unit, with depths exceeding
2000 m comprising over three-quarters of the world ocean.
See Fairbridge (1966).
- abyssopelagic zone
- One of five vertical ecological zones into which the
deep sea is sometimes divided.
There is a pronounced drop in the number of species
and the quantity of animals as one passes into this zone.
It is separated from the overlying
by the 4 C isotherm and from the underlying
at about 6000 meters. The distinction between
benthic species can be
difficult to ascertain in this zone.
See Bruun (1957).
- a-c meter
- An instrument used to perform in-situ measurements of the amount
of chlorophyll in water.
It does this by pulling water into two tubes, one measuring
light absorption and the other attenuation.
A beam of light with a wavelength rotating among three values
is projected into each tube.
The attenuation tube determines light absorption and scattering
by measuring how much of the original light beam remains after it
passes through the water inside the blackened tube.
The absorption tube determines only how much light is absorbed
by particles by measuring how much light is left of the original
beam including that which has bounded off particles.
This tube is lined with a quartz mirror which, in contrast to
the absorbing black surface in the attenuation tube, reflects scattered
light toward the detector.
Chlorophyll causes a large change in the attenuation of light with
a wavelength of about 676 nanometers, so a measurement of attenuation
at the appropriate wavelength is a proxy measurement of chlorophyll
concentration to first order.
A fluorometer can also be used
to measure chlorophyll.
- 1. Abbreviation for the
Antarctic Circumpolar Current.
2. Abbreviation for the
Alaskan Coastal Current.
- Abbreviation for Atlantic Climate Change Experiment,
a joint program between WOCE and
NOAA's ACCP designed to
increase understanding of the meridional overturning circulation (MOC)
of the Atlantic Ocean and the overlying
atmosphere at interannual and longer time scales.
The goals of ACCE were:
See WOCE (1995).
- to provide a quantitative 4-D observational description of the
pathways and material property fluxes of the MOC within the North
Atlantic Ocean that vary on time scales from interannual to at least
- to improve understanding and modeling of the relationships between
the rates and natural variability of the MOC, internal ocean properties,
SST, and the variability of the overlying atmosphere; and
- to identify and initiate measurements to be continued beyond the
ACCE observational period to monitor the variability of important
elements of the MOC and its relation to global climate variability.
- Acronym for Austral Chilean Coast and Inland Sea project, a
program to facilitate the development of an interdisciplinary
and multi-institutional program focused on ecological and
socio-econonomic-human health issues in the temperate
waters of the Austral Chilean Coast and Inland Sea.
- Acronym for the Antarctic Circumpolar Current Levels by Altimetry and
Island Measurements program in the South Atlantic and Southern
Oceans. It consists of measurements from coastal tide gauges and
bottom pressure stations, along with an ongoing research program
in satellite altimetry.
ACCLAIM was the Proudman Oceanographic Laboratory's main contribution
to WOCE and now provides data for
CLIVAR, GLOSS and
The coastal tide gauge portion of ACCLAIM took place in two phases.
In Phase I from 1983, measurements at coastal tide gauge sites were
sub-surface pressure (SSP) measurements rather than sea level (where
SSP is defined as the total, measured pressure recorded by a sub-surface
pressure transducer, a measurement including the atmospheric as well as
the water column pressure). These data were acquired with different
sensors and with different pressre integration periods.
Phase II, which started in early 1993, involved replacing the gauges
at several sites with `B gauges' that recorded SSP, air pressure and
sea level. These gauges have precise datum control and are used
to provide long term sea level change data to the
See Spencer et al. (1993).
- Abbreviation for the Atlantic Climate Change Program, a
initiative for understanding the decadal-scale interactions of
deep circulation in the Atlantic and how it influences the
The goals of ACCP are:
- to determine the seasonal-to-decadal and multidecadal variability
in the climate system due to interactions between the Atlantic
Ocean, sea ice, and the global atmosphere using observed data,
proxy data, and numerical models;
- to develop and utilize coupled ocean-atmosphere models to examine
seasonal- to-decadal climate variability in and around the
Atlantic basin, and to determine the predictability of the Atlantic
climate system on seasonal-to- decadal timescales;
- to observe, describe, and model the space-time variability of the
large- scale circulation of the Atlantic Ocean and determine its
relation to the variability of the sea ice and sea surface temperature
and salinity in the Atlantic on seasonal, decadal, and multidecadal
- to provide the necessary scientific background to design an
observing system of the large-scale Atlantic Ocean circulation pattern,
and develop a suitable Atlantic Ocean model in which the appropriate
data can be assimilated to help define the mechanisms
responsible for the fluctuations in Atlantic Ocean circulation.
- The degree of freedom from error. The total error compared to a
theoretically true value. Contrast with and see
for an example.
- Abbreviation for Antarctic Current Experiment, a
- Acronym for Australian Coastal Experiment, an investigation
whose primary goal was to
identify continental shelf waves (CSW).
It was carried out off the coast of New South Wales (eastern Australia)
between Cape Howe and Newcastle from September 1983 to March 1984.
The experiment included an array of current meters with three main
lines with five moorings each, repeated CTD
and XBT surveys, meteorological measurements from
moored buoys and coastal stations, sea level measurements at coastal
tide gauges, and bottom pressure measurements at a few sites.
Each of the three mooring lines was arranged perpendicular to the
local coastline, were nominally identical, and consisted of 15 Aanderaa current
meters on 5 moorings.
A free wave analysis of the data gathered demonstrated that waves passed
through the experimental array and exhibited dispersion characteristics
strongly indicative of coastal trapped waves.
The measured pattern speed was between those predicted for free and
There was some predictive skill using a trapped wave model. Although the model
predictions only accounted for a maximum of 40% of the observed variance,
the best statistical predictor could only account for 50%.
This led to the conclusion that not all of the energy in the weather forcing
band was described by coastal trapped waves.
See Freeland et al. (1986) and
Church and Freeland (1987).
- Abbreviation for Advisory Committee on the Marine Environment, an
- Abbreviation for Advisory Committee on Marine Pollution, an
- Abbreviation for Advisory Committee of Experts on Marine Resources
Research, a FAO committee.
- Abbreviation for Advisory Committee on Oceanic Meteorological
Research, an WMO committee.
- Abbreviation for Advisory Committee on Protection of the Sea.
- Acronym for Arctic Climate Observations using Underwater Sound, a
joint U.S. and Russian program started in 1995.
The main objective of ACOUS is to establish a long-term, real-time
Arctic Ocean observing system using cabled moorings that integrate
point measurements with acoustic remote sensing measurements. The
remote sensing is used to monitor basin-scale changes in the
ocean temperature and the thickness of the Arctic ice cover.
See Mikhalevsky et al. (1999).
- acoustic signature
- A set of characteristics used to describe a sound signal.
This may include sound echos from targets, radiated and
ambient noise, with salient echo characteristics including
target strength, spectral reflectivity versus frequency,
doppler shift, doppler spread and target range extent.
- acoustic tomography
- The inference of the state of the ocean from precise measurements
of the properties of sound waves passing through it.
This technique takes advantage of the facts that the properties
of sound in the ocean are functions of temperature, water velocity
and other salient oceanographic properties and that the ocean
is nearly transparent to low-frequency sound waves. These felicitous
circumstances combine to allow signals transmitted over hundreds to
thousands of kilometers to be processed with
inverse methods to obtain
estimates of large-scale fields of ocean properties.
An especially advantageous feature of this method is that, given
the 3000 knot speed of sound in the ocean, reasonably
synoptic fields can be constructed.
The chief problems presently encountered in this field are
those related to engineering sufficiently accurate transmitters
and receivers for the task.
See Munk et al. (1995).
- acoustical oceanography
- The study of sound propagation in the ocean and its underlying
sediments. This ranges from the earliest use of
to chart the ocean floor to the use of
SONAR to locate
schools of fish, underwater vehicles and ocean drifters to
the most recent applications of
acoustic tomography to infer
large-scale properties of the ocean and the ocean floor.
- Abbreviation for the Arctic Climate System Study, a
WCRP program whose goal to to ascertain
the role of the Arctic in global climate. The primary scientific
- understanding the interactions between the
Arctic Ocean circulation, ice cover and
the hydrological cycle;
- initiating long-term climate research and monitoring programs for
the Arctic; and
- providing a scientific basis for an accurate representation of
Arctic processes in global climate models.
The components of ACSYS include:
- adaptive mesh refinement
- A method for locally refining grids in finite difference ocean models.
The basic idea behind the method is to attain a given accuracy for a
minimum amount of work. This is done by computing estimates of
the truncation error, and creating refined grids (or removing existing
ones) where and when it is necessary.
The approach is also recursive so that fine grids can contain even
See Blayo and Debreu (1999) for an initial application of this
method to ocean circulation models.
- Abbreviation for Acoustic Doppler Current Profiler, an instrument used
to measure ocean currents. It transmits high frequency acoustic
signals which are backscattered from plankton, suspended sediment,
and bubbles, all of which are assumed to be traveling with the
mean speed of the water.
The ADCP estimates horizontal and vertical velocity as a function of
depth by using the Doppler effect to measure the radial relative
velocity between the instrument and scatterers in the ocean.
Three acoustic beams in different directions are the minimum number
required for measuring the three velocity components, with a fourth
adding redundancy and an error estimate.
A ping is transmitted from each transducer about once per second, with
the echo returning over an extended period.
Echos from shallow depths return before those from greater depths.
Profiles are produced by range-gating the echo signal, i.e. breaking
the echo into successive segments called depth bins corresponding
to successively deeper depth ranges.
The noisy velocity estimates from each ping are vector-averaged into
1- to 10-minute ensembles, and the resulting relative velocities are
rotated from the transducer's to the earth's reference frame using the
A navigation calculation is performed to obtain absolute currents,
which are obtained by subtracting the average of the ship velocity
relative to a reference layer (i.e. ADCP velocities) from the
absolute ship velocity over the ground (from GPS navigation).
The raw absolute current velocities relative to the reference layer
are then smoothed to reduce the effect of noise in the position fixes,
and combined with the navigation data to obtain the best estimates
of ship positions and velocities.
Thus, absolute currents at any depth can be determined from the ship
navigation data and the relative ADCP measurements.
The ADCP measures the ocean current velocity continuously over the
upper 300 m of the water column, usually in 8 m depth increments.
It is also used to estimate the abundance and distribution of
biological scatterers over the same depth range and in the
same depth increments.
ADCP data collection requires that four instruments work together.
These are the ADCP itself, the ship's gyrocompass, a
GPS receiver, and a GPS Attitude
Determination Unit (ADU).
- Involving or allowing neither gain nor loss of heat.
- adiabatic compressibility
- A quantity arising from taking derivatives of the density in
representation of the
equation of state.
It is defined by
where is the fluid density,
the potential temperature, and
See Muller (1995),
McDougall et al. (1987) and the related
saline contraction coefficient
thermal expansion coefficient.
- Acronym for Asian Dust Input to the Oceanic System.
See Betzer et al. (1988).
- adjustment time
- A time scale characterizing
the decay of an instantaneous input pulse into a reservoir.
It is also used to characterize the adjustment of the mass
of a reservoir following a change in the source strength.
- Adriatic Bottom Water (ABW)
- A water mass - also known as
Adriatic Deep Water - formed in the southern
Adriatic Sea that exits into the
Ionian Sea via
The temperature and salinity of ABW are 13C and
38.6 psu, respectively.
There are a couple of competing conjectures as to the origin of
Either way, most studies confirm that ABW represents the most important
component of the bottom water of the entire Eastern Mediterranean.
See Artegiani et al. (1993).
- some postulate that
North Adriatic Deep Water flowing
into the canyon in the shelf of Bari mixes with
Modified Levantine Intermediate Water (MLIW)
to form ABW; and
- others think that contribution of NADW is minor and that the
ABW is formed mainly by the mixing of the surface water in the
center of the South Adriatic Pit with the underlying MLIW during
periods of deep convection.
- Adriatic Deep Water (ADW)
- Another name for
Adriatic Bottom Water (ABW).
- Adriatic Sea
- A part of the eastern basin of the
Mediterranean Sea located
between Italy and the Balkan Peninsula. It is landlocked on
the north, east and west, and is linked with
the Mediterranean through the Otranto
Strait to the south.
The Adriatic is a rectangular basin oriented in a NW-SE direction with
a length of about 800 km and a width of about 200 km.
It can be divided into three sub-basins:
The bottom rises toward the Strait of Otranto past the southern basin,
with the strait having a maximum depth of 780 m, and average depth
of 325 m, and a width of about 75 km.
- a northernmost shallow basin with the bottom sloping gently to
the south and reaching at most 100 m;
- three pits located along the transversal line off Pescara (one of
which is known as the Jabuka Pit), with
a maximum depth of 280 m; and
- a southern basin called the South Adriatic Pit
(separated from the middle basin by the 170 m deep
Palagruza Sill) characterized by approximately circular isobaths, with
a maximum depth of about 1200 m in the center.
The meteorological forcing has been summarized by
Artegiani et al. (1993) as:
Mainly during the winter, the Adriatic Sea region is under a continuous
influence of passing mid-latitude meteorological perturbations and of
the wind systems associated with them. The two main wind systems are the
bora and the scirocco. The bora is a dry and cold wind blowing in an
offshore direction from the eastern coast. The scirocco blows from the
southeast (i.e. along the longitudinal axis of the basin) bringing
rather humid and relatively warm air into the region. In particular,
the bora produces appreciable buoyancy fluxes through evaporative and
sensible heat loss, induces both wind-driven and thermohaline circulation,
and, most importantly, is responsible for deep water formation processes.
This is one of the two regions within
the Mediterranean where freshwater input exceeds evaporation
(the other being the Black Sea).
This is due mostly to outflow from the Po River in the north, which accounts for
1700 m s of the 4000 m s total river discharge
in the Adriatic.
The flow between the Adriatic and the greater Mediterranean
through the Otranto Strait is that of a typical
dilution basin wherein
low salinity water exits near the surface and high
salinity water enters at depth.
The Mediterranean inflow is of surface Ionian water and, in a
deeper layer from 200-300 m, of
Modified Levantine Intermediate Water (MLIW).
This inflow occurs over a wide area along the eastern shore of the
strait, with near-surface outflow concentrated in a thin layer along the
The latter consists of relatively fresh water originating mostly from
the northern Adriatic.
The remainder of the outflow consists of
Adriatic Bottom Water (ABW),
a water mass formed in the southern
basin that flows over the sill of the
Otranto Strait into the Ionian Sea.
The mean basin-wide circulation is generally a cyclonic pattern with
several smaller, more or less permanent gyres embedded therein.
A topographically controlled cyclonic gyre sitting over the
South Adriatic Pit partially isolates the northern Adriatic from
This gyre causes a bifurcation of the incoming MLIW, with part of it
entering the northern basins over the Palagruza Sill,
while the rest is entrained into the
South Adriatic cyclonic circulation cell.
The circulation regime varies seasonally and interannually in response
to changes in the heating and wind regimes.
Seasonally, the winter circulation is characterized by a prevalence
of warmer Mediterranean inflow reinforced by southerly winds.
In summer, there is a stronger outflow of fresher and warmer Adriatic
water along the western coast supported by the Etesian winds.
See Buljan and Zore-Armanda (1976),
Orlic et al. (1992),
Artegiani et al. (1993),
Tomczak and Godfrey (1994),
Artegiani et al. (1997a),
Artegiani et al. (1997b) and
- Abbreviation for
Adriatic Bottom Water.
- Abbreviation for
Adriatic Deep Water.
- Aegean Deep Water
- See POEM Group (1992).
- Aegean Sea
- A marginal sea in the eastern
Mediterranean Sea centered
at approximately 25 E and 38 N.
It is located between the Greek coast to the west, the
Turkish coast to the east, and the islands of Crete and
Rhodes to the south. It contains more than 2000 islands
forming small basins and narrow passages with very irregular
coastline and topography.
The northern part of the Aegean is also known as the
and the southern part between the Cretan Arc and the Kiklades
Plateau (defined as the 400 m isobath) as the
It contains an extended plateau (Thermaikos, Samothraki, Limnos and
Kyklades) as well as the deep basins the North Aegean
Trough (1600 m maximum depth), the Chios Basin (1160 m) and the
Cretan Sea (two depressions in the east 2561 m and 2295 m deep).
It covers an area of 20,105 km, has a volume of
74,000 km, and a maximum depth of 2500 m.
It is connected to the Levantine Sea
to the southeast via the Cassos or Kasos Strait (67 km wide, 1000 m deep)
between Crete and Karpathos, the Karpathos strait (43 km wide,
850 m deep) between Karpathos and Rhodes, and the Rodos or Rhodos Strait
(17 km wide, 350 m deep) between Rhodes and Turkey.
It joins the Ionian Sea and
Cretan Sea to the southwest
through the Antikithira Strait between Crete and Antikithira
(32 km wide, 700 m deep), the Kithira Strait
between Antikithira and Kithira (33 km wide,
160 m deep), and the Elafonissos Strait between
Kithira and Peloponnese (11 km wide and 180 m deep).
There is considerable and complicated interchange of water
with the eastern Mediterranean through these passages.
The Strait of Dardanelles (55 m deep, 0.45-7.4 km wide)
provides a northern link to the
Black Sea from which the Aegean
receives around 190 km per year of water.
The climate in the Aegean Sea area is characterized by the presence
of two distinct periods, summer and winter, with spring and autumn
relatively short and transitional.
The topography and continual alternation of land and sea make the
climate highly variable.
Annual river runoff averages about 18,800
and evaporation exceeds precipitation and river runoff.
The most prominent wind pattern is the Etesian winds, which are
persistent, northerly, cold and dry winds that often reach
gale force in July and August.
When this wind approaches the southern Aegean is bifurcates, becoming
northeasterly over the Kitherian Straits and northwesterly-westerly
over the southeastern Aegean.
The Etesians vanish in late autumn to be replaced by violent cyclonic
storms and highly variable prevailing winds.
The surface circulation is most affected by the
summer Etesian winds and the low salinity inflow from
the Black Sea.
The winds cause upwelling along the western
coasts of the islands in the eastern Aegean, and a accompanying cold
surface zone with temperatures 2-3C lower than in the northern
and western Aegean.
During the summer, this colder water is present in the eastern Aegean
from Rodos Island up to the Limnos Plateau. In winter, the warmer
waters of Levantine origin are found in the same area, while the
cold waters arriving from the Strait of Dardanelles spread over
the Samothraki Plateau and follow the general cyclonic circulation
of the north Aegean.
In addition to the overall cyclonic circulation,
there is also a Samothraki anticyclonic gyre located in the
northeastern part of the North Aegean, a semi-permanent feature that
can be detected through most of the year, and an anticyclone near Athos.
The surface flow in the south is into the
Aegean between Kithira and Crete, Crete and Karpathos, Karpathos
and Rhodes, and Rhodes and Turkey, and into the Mediterranean between
Kithira and the Peloponnese coast.
There is systematic wind-driven upwelling along the northern
coasts of the Patraikos and Korinthiakos Gulfs.
The main water masses found in the Aegean are (from shallowest to
The BSW enters from the Strait of Dardanelles, producing a pronounced
halocline in the norther Aegean with a maximum depth from 20-80 m.
It moves southward and westward, following the general cyclonic
circulation, and can be detected by a surface salinity minimum as
far south as the Kithira Straits.
LIW is the saltiest water mass of the eastern Mediterranean.
It is generated in the Levantine and southern Aegean Seas in
February and March. It flows eastwards and westwards from the
Aegean, and also flows into the Aegean via the eastern straits of
the Cretan Arc.
It predominates in the subsurface layers of the Cretan Sea as well as
in the eastern parts of the Aegean as far north as the southern
boundary of the Limnos Plateau, and is easily identified by its salinity
The modified AW enters the Aegean through the straits of the Cretan Arc
and is identifed in several regions as a subsurface (30-200 m) salinity
The Aegean deep water mass extends from about 400-500 m to the bottom,
with temperatures ranging from 12-14.5C and salinities from
See POEM Group (1992),
Stergiou et al. (1997) and
Balopoulos et al. (1999).
- Acronym for Atmosphere/Ocean Chemistry Experiment, a multi-disciplinary
and -institutional program focusing on a number of aspects of the atmospheric
chemistry over the North Atlantic Ocean.
The objectives of AEROCE are:
- to gauge the impact of anthropogenic sources on the chemical and
physical properties of the atmosphere;
- to assess the consequences of the perturbuations on natural
processes including climate; and
- to predict the longer term efforts via the use of models.
The program officially started in 1987 with coordinate measurements
from four stations, i.e. Barbados, West Indies; Bermuda; Izaña, Tenerife,
Canary Islands; and Mace Head Ireland.
Five more stations were added in June 1995 to give greater geographical
coverage of continuous measurements of bulk aerosol chemical composition
and condensation nuclei.
- Acronym for Alaska Environmental Satellite Oceanography
Project, a collection of remote sensing experiments and projects
being performed at the Institute of Marine Sciences at the
University of Alaska Fairbanks.
This seems to have been mothballed as of 2001.
This is part of the larger SEA Project.
- Acronym for Antarctic Environment and Southern Ocean Process Study, also
known as the U.S. Southern Ocean Joint Global Ocean Flux Study
AESOP involved studies of two different and distinct regions.
The first was the Ross Sea continental shelf,
where a series of six cruises (on the R.V.I.B. Nathaniel B.
Palmer) collected data from October 1996 through
February 1998. The second was the southwest Pacific sector of the
Southern Ocean spanning the
Antarctic Circumpolar Current (ACC)
at 170W, where data were collected during five cruises (on
the R.V. Roger Revelle) from
September 1996 through March 1998, as well as during selected transits
between New Zealand and the Ross Sea.
The objectives of the project were to:
- better constrain the fluxes of carbon in the Southern Ocean,
- identify the factors and processes regulating the magnitude and
variability of primary productivity, and
- gain a sufficient understanding of the Southern Ocean to model
past and present carbon fluxes with sufficient accuracy to predict
its response to future global changes.
The findings of AESOPS include:
See Smith et al. (2000) and other papers therein.
- the Ross Sea continental shelf is among the most productive of all
Antarctic systems, with a significant seasonal cycle;
- a seasonal bloom occurs in the region of the
- the annual production of the Ross Sea can be quantified by measuring
deficits of nutrients and dissolved carbon dioxide;
- the phytoplankton blooms in the Ross Sea have essentially no losses
due to microzooplankton herbivores;
- while iron did not stimulate phytoplankton growth in low silica
waters north of the silica gradient, it substantially stimulated diatom
growth in waters south of the gradient;
- the Polar Front region exhibits extreme mesoscale variability; and
- dissolved organic carbon concentrations increase seasonally by less
than a third as much as particulate organic carbon levels.
- Abbreviation for
Arctic Frontal Zone.
- Abbreviation for
Aegean Deep Water.
- age of tide
- The delay, usually a day or two, between full and
new moons (when the equilibrium semi-diurnal
tide is maximum) and the following
spring tides. This terminology
was first used to refer to this phenomenon by Whewell in
1883, although Defant referred to it as ``spring
retardation'' in 1961 and Wood later (in 1978) used the terms
``age of the phase inequality'' and ``age of the diurnal
equality'' to refer to, respectively, the ages of the
semi-diurnal and diurnal tides. This delay is caused
by frictional energy dissipation in coastal seas, although a
localized increase in the age of tide is also a good
indication of resonances at that location.
See Murty and El-Sabh (1985).
- age of water
- The elapsed time since a given water mass
was last at the sea surface.
See Groves and Hunt (1980).
- See double tide.
- A process that significantly alters the sizes, characteristics and
abundances of suspended particles in the ocean.
There are two major mechanisms for aggregation:
- biologically mediated aggregation, which occurs when small particles
are aggregated into fecal pellets through the feeding activities of
- aggregation via the largely physical processes of collision and
sticking, i.e. coagulation.
The impacts of aggregation on marine ecosystems include:
See Alldredge and Jackson (1995).
- much of the particulate matter reaching the ocean interior and
sea floor sinks as large, rapidly settling aggregates of detritus,
mucous, algae and microorganisms in the visible size range, i.e.
marine snow, so the export of carbon
and nutrients from the surface ocean is directly linked to the
mechanisms responsible for combining small particles into larger
units capable of rapid settlement, i.e. aggregation;
- aggregation of small organisms and other organic particles affects
the abilities of grazers to isolate their food from the aquatic environment
and makes more food available to large-particle feeders;
- aggregation produces particles large enough to maintain unique
internal chemical environments that can support unusual, microbial
communities and potentially provide island-like refuges for protozoa
and micorozooplankton; and
- aggregation affects the optical properties of seawater by altering
the size distribution and abundance of particles available to absorb
and scatter light.
- A condition observed annually in the coast water off Peru
in which the water is discolored red or yellow and there is
a significant loss of marine life. It typically occurs from
April through June and is probably caused by an increase
in water temperatures via the importation of warmer waters by
ocean currents. This causes the death of temperature sensitive
marine organisms such as dinoflagellates, which may in turn
kill other organisms via the release of toxins. The annual
nature of this phenomenon makes it distinct from the
El Nino phenomenon occurring in
the same region. This is also known as salgaso or
- Agulas Basin
- An ocean basin located off the southern tip of Africa at
about 43 S in the South Atlantic Ocean.
It includes the Agulhas Abyssal Plain.
See Fairbridge (1966).
- Agulhas Current
western boundary current
in the Indian Ocean south of 30 S.
The southern Agulhas Current flows southwestward as a narrow jet
along a steep continental slope, and is normally pinned to within
10-15 km of its mean position at latitudes 28.5-34S.
Large meanders - called the Natal pulse - can sometimes occur
within this region. These extend an average of 170 km offshore
with downstream propagation rates of about 21 cm s, with the
rates decreasing to 5 cm s as the continental shelf broadens
At this point the current separates from the coast and continues
southwestward along the Agulhas Bank, where many meanders, plumes and
The maximum transport of the Agulhas occurs in the vicinity of
Agulhas Bank, where transport estimates range from 95 to 136 Sv.
The core of the current has been defined as where surface velocities
exceed 100 cm s, with the core averaging about 34 km wide
with a mean peak speed of 136 cm s (with a greatest peak
speed of 245 cm s).
At around 36S the Agulhas leaves the continental shelf
and develops oscillations of increasing amplitude, eventually
retroflecting back toward the Indian Ocean in the region of
16-20E as the
Agulhas Return Current.
The retroflection loop usually encloses a pool of Indian Ocean
surface water south of Africa whose temperature is more than
5 warmer than South Atlantic surface water at similar latitudes.
The core of the Return Current infrequently passes over the
See Lutjeharms and van
Ballegooyen (1988) and
Peterson and Stramma (1991).
- Agulhas Front (AF)
- A strong subsurface to intermediate depth front beneath the
upper 100-150 m that originates at around 20-25 E
below the southern tip of Africa. It extends to between
65-90 E where it merges with the
Southern Subtropical Front
in the Indian Ocean sector of the ACC.
The chief identification criterion is usually the depth range
of the 10 isotherm, about 300-800 m south of Africa
at 16-27 E. This range shrinks to about 400-650 m
to the east in the Kerguelan-Amsterdam passage, indicating the
gradual weakening of the AF.
A thermostad on the warm side of the AF in the 150-300 m layer
is another useful identification criterion.
This thermostad cools and freshens to east, ranging from
17-18 C/35.5-35.6 at 20 E to
12-14 C/35.2-35.4 at 70 E.
See Belkin and Gordon (1996).
- Agulhas Retroflection
- See Peterson and Stramma (1991) and
Lutjeharms et al. (1992).
- Agulhas Return Current
- See Agulhas Current and
Peterson and Stramma (1991).
- Agulhas Undercurrent
- A current flowing beneath the
LADCP measurements indicate the core is centered
around 1200 m, against the continental slope and directly below the surface
core of the southwestward flowing Agulhas Current.
Maximum velocities of 30 cm/s to the northeast are observed in the
undercurrent, and its volume transport is 6 Sv, about a tenth that of
the overlying Agulhas.
See Beal and Bryden (1997).
- Acronym for Arctic Ice Dynamics Joint Experiment, a collaborative
program between the U.S., Canada and Japan that took
place in two phases in 1975-1976. In summer 1975 four manned camps
were maintained on ice floes in the Arctic Ocean to measure
surface and geostrophic winds, ocean current velocities, and
ice floe position. In April of 1976 the submarine USS Gurnard
traversed 777 nautical miles along three tracklines in the
Beaufort Sea, collecting ice
thickness data from upward-looking acoustical soundings.
See Trowbridge (1976).
- air-sea interaction
- The processes that involve the transfer of energy, matter, and
momentum between the atmosphere and the ocean.
The is one of the least well understood areas of physical oceanography,
with the theory inadequate and the data sparse.
Specific areas with glaring gaps include the interaction
of the wind and surface waves, the parameterization of subgrid scale
processes in large-scale circulation models, and the transfer of gases
across the air-sea interfaces.
See Donelan (1990),
Kraus and Businger (1994) and
- Acronym for Automatic Recording Inverted Echo Sounder.
- Airy wave
- A theory of waves of small amplitude in water of arbitrary
depth that is also known as linear wave theory.
The derivation of the theory, given the assumptions
of small wave slope (
) and a depth much
greater than the wave height
), gives the expression for the water surface
where is the wave height, the wave number, and
the wave frequency. An expression for the wave
length has also been developed, although it must be solved
Simpler expressions are available for the limiting cases
of deep and shallow water, with deep water being the case
(where is the depth and
the deep water wavelength) and shallow water
the case where
The particles move generally in closed elliptical orbits that
decrease in diameter with depth, reducing to limiting cases
of circles and straight lines in, respectively, deep and
See Kinsman (1984), LeMehaute (1976) and
- Abbreviation for Arctic Ice Thickness Monitoring Project.
- Abbreviation for
Arctic Intermediate Water.
- Acronym for Arctic Internal Wave Experiment, a project of the
APL at the University of Washington that
took place in 1985. See also LEADEX.
See Levine (1990).
- Ajax Expedition
- An oceanographic research expedition from 1983-1984.
- Acronym for Autonomous Lagrangian Circulation Explorer float,
an instrument that can be programmed to cycle up and down
through the water column at predetermined intervals to
provide vertical profiles of temperature and salinity.
ALACE floats have been used to track currents down to 1.5 km.
In operation, the float sinks to its neutral buoyancy depth,
drifts with the current, and after a programmed time (5-30 days)
increases its buoyancy by pumping oil into an external bladder to
rise to the surface.
It then transmits data to Service Argos satellites
over a 24 hour period, returns the oil to the internal bladder,
and sinks again to its neutral buoyancy depth.
The cycling continues until the battery energy is depleted after
around 100 cycles, or until the float fails for some other reason.
See Davis et al. (1992).
- Aland Sea
- A part of the Baltic Sea bordered by
the Gulf of Bothnia to the north,
the Gulf of Finland to the east,
and the man part of the Baltic Sea to the south.
- Alaska Coastal Current
- A narrow, high-speed, westward flow which extends for more than 1000 km
along the coast of Alaska. This is a separate feature from
the offshore, deepwater
Alaskan Stream. It was not
recognized as such up until the mid-1970s when a series of
hydrocast surveys in the area was begun which led to its
identification as a distinct circulation feature.
The ACC is driven by freshwater discharge from the mountainous
and coastal regions around the Gulf of Alaska and the consequent
nearshore confinement of this low-salinity water by westward
winds. It is typically narrow ( 50 km), shallow ( 150 m)
and partially baroclinic.
It flows most intensely between 145 and 155 W through
the Shelikov Strait between the Alaskan Peninsula and
Kodiak and Afognak Islands, but extends
recognizably along the Peninsula as far as
The baroclinic speeds and transports have been
estimated as typically 30 cm s and
0.4 Sv, respectively, in the winter, spring and summer. In the
fall, when the freshwater influx leads to the spin-up of the ACC,
the speeds and transports have been estimated as
89-133 cm s and 1.0-1.2 Sv, respectively.
Current mooring measurements have yielded estimates of
six-month mean total transports ranging from 0.85 Sv at 151 W
to 0.64 Sv at 155 in Shelikof Strait, with daily means
as high as 2.5 Sv and marked variability from day to day.
This variability is thought to be mainly due to variations in
wind-forcing caused by the passage of large-scale storms along
the coast. The mean baroclinic transport as estimated from
the same measurements was found to be about 75% of the total.
See Stabeno et al. (1995).
- Alaska Current
- The eastern limb of the counterclockwise-flowing subpolar gyre
in the North Pacific. This current is concentrated on the shelf
region by the freshwater input from Alaskan rivers which enhances
the pressure gradient across it. It is strongest in winter with
current speeds around 0.3 m/s and weakest in July and August when
prevailing winds tend to oppose its flow.
This current may or may not be distinguished from a western
boundary current flowing along the Aleutian Islands and called
the Alaskan Stream. Both have previously gone by the name of
Aleutian Current. Whether or not the nomenclature makes a
distinction, the Alaskan Stream and Current do have distinguishing
characteristics. The Current is shallow and highly variable while
the Stream is steadier and reaches to the ocean floor. The
more barotropic nature of the latter is evidence that it is
indeed a product of western boundary current dynamics while the
former is in an eastern boundary regime.
See Thomson (1972).
Tomczak and Godfrey (1994).
- Alaska Gyre
- A subpolar cyclonic circulation in the northeast Pacific associated with
the Aleutian low.
The primary currents consist of a broad eastern boundary current flowing
north, condensing into a narrow western boundary flow in the apex of the
gyre and proceeding west-southwest along the Aleutian Peninsula as
the Alaskan Stream.
See Lagerloef (1995).
- Alaskan Stream
- See Alaska Current.
- Acronym for Antarctic Largescale Box Analysis and the Role Of the Scotia
Sea, a cruise along the rim of the
Scotia Sea that took place from March 15 to
April 23, 1999 on the RRS James Clark Ross.
The aim of the cruise was to study the influence of the Scotia Sea
on global ocean circulation by undertaking a detailed hydrographic
survey of a box surrounding the Scotia Sea, with CFCs, oxygen isotopes,
tritium, helium and nutrients sampled as well as the traditional
temperature, salinity and oxygen.
The specific goals of ALBATROSS were:
- to determine the pathways of the
Weddell Sea Deep Water (WSDW) as it enters
and leaves the Scotia Sea;
- to quantify the cooling and freshening of
Circumpolar Deep Water (CDW) as it crosses
the Scotia Sea;
- to determine the pathway and transport of
Southeast Pacific Deep Water (SEPDW) across
the Falkland Plateau;
- to measure the transport of the
Falkland Current and compare with the
transport of the wind stress curl forced western boundary current;
- to compute heat, fresh water and other tracer budgets for the Scotia
Sea, southwestern Atlantic and western
- the calculate the transport and characterize the fronts associated
with the ACC as it enters and leaves the Scotia Sea;
- to determine the interannual variability of the transport and water
mass properties of the ACC at Drake Passage; and
- to determine temporal changes to the water masses of the Scotia
Sea and the extent to which recently ventilated deep waters may have
been affected by climate change.
- The proportion of incident radiation
reflected by a surface. About 30% of the incoming solar energy
is reflected back to space from the earth, of which 25% is reflected
by clouds and 5% by the surface or by atmospheric molecules or
suspended particles. The clouds and atmospheric gases and particles
absorb 25% of the incident radiation with the remainder absorbed at
the surface. See Peixoto and Oort (1992), Ch. 6.
- Alboran Sea
- A part of the western basin of the
Mediterranean Sea that
extends from the Gibraltar Strait
Alboran Islands covering an area between about 35 and 38
N and 6 N and the Equator.
This sea is dominated by a wavelike front with two anticyclonic
gyres in the western and eastern parts of the basin, which at
times disappear completely.
The Algerian Current is
closely tied to the dynamics associated with the eastern anticyclonic
It abuts the Balearic Sea to the east.
See Va (1984),
Gascard and Richez (1985),
Vazquez-Cuervo et al. (1996) and
Viúdez et al. (1998).
- Alboran gyre
- A gyre found in the
See Speich et al. (1996) and
Nof and Pichevin (1999).
- Acronym for Arbitrary Lagrangian Eulerian, a finite element solution
fluid flow problems with moving interfaces, e.g. moving walls, free
In the ALE method, the newly updated free surface is determined purely
via the Lagrangian method, i.e. by the velocities of the fluid particles
at the free surface. The nodes in the interior of the domain are displaced
in an arbitrarily prescribed way to obtain a mesh of proper shape and
to avoid mesh crossing.
- Aleutian Current
- See Alaska Current.
- Aleutian low
- A center of action
centered over the Aleutian Islands between the east coast of the
Siberian Kamchatka Peninsula and the Gulf of Alaska at about
50 N. It is prominent in the winter and disappears in
summer, with the average central pressure below 1000 mb in
January. See Angell and Korshover (1974).
- Acronym for AIDJEX Lead Experiment,
which took place Feb. 23 through Apr. 10, 1974 and investigated
small-scale meteorological and oceanographic processes
associated with leads in pack ice near Barrow, Alaska.
The experiment plan called for rapid deployment of five
instrumental huts, measuring equipment and personnel by
helicopeters and fixed-wing aircraft. The processes of
primary interest were sensible, latent, and radiant
heat loss to the atmosphere as well as the sinking of
convective plumes of saline water formed by freezing
and brine rejection at the surface. Logistical problems
limited the success of the experiment, with the
helicopter range limiting deployment to within 30
miles of Barrow and a dearth of suitable leads in that
See SMith et al. (1990).
- Acronym for Long-life, multi-cycle, pop-up RAFOS floats, i.e. RAFOS
floats that surface at regular intervals throughout their lifetime and
transmit data via satellite.
- Alfred Wegener Institute (AWI)
- The German national research center for polar and marine research.
The Institute was founded in 1980 and named after the geophysicist
and polar researcher Alfred Wegener.
The mandate of the AWI includes fundamental scientific research in
the polar regions, national coordination of polar research projects,
and logistic support of polar expeditions from other German
institutes. The Institute uses the RV Polarstern to perform
research at sea. See the
AWI Web site.
- Algerian Current
- A current that flows eastward along the Algerian coast in the
Mediterranean Sea. It flows
as a narrow, easily distinguished current for around 300 km
from about 0 to 4 E with a width of less than 30 km, average
and maximum velocities of 0.4 and 0.8 m/s, respectively, and
a tranport of about 0.5 Sv. This is a continuation of the
current associated with the
Almeria-Oran Front that is
itself a continuation of the
flow of Atlantic Ocean water entering through the
See Arnone et al. (1990)
and Tomczak and Godfrey (1994).
- A phenomenon encountered when sampling a continuous function to produce
values at discrete points. If the sampling frequency isn't high enough
to resolve the highest frequency signal present in the continuous
function, then the high frequency information above the sampling
frequency will appear as a false enhancement of (or, equivalently,
be aliased onto) a related lower frequency in the computed power
- Acronym for Autonomous Lander Instrumentation Packages for
Oceanographic Research, a project funded by
MAST III to create a European fleet of
lander vehicles that can operate together in joint research
projects. Lander vehicles will be built to carry out a variety
of experiments ranging from sediment probes to fish tracking.
Three facets of lander technology are to be addressed: (1) the
development of techniques to launch a fleet of landers from
a single ship; (2) the development of new sensors for examining
processes in the water of the deep benthic boundary layer at depths
ranging from 200 to 5000 meters; and (3) the design and construction
of two new types of landers, i.e. one that can carry several sensing
devices and another compact one that can be operated from a small
See the ALIPOR Web site.
- Common abbreviation for
- A property of sea water operationally defined as the
excess positive charge to be balanced by CO and HCO ions.
The carbonate ion content of any unit of sea water is equal to
its alkalinity (i.e. excess positive charge) minus its total
dissolved carbon content.
See Broecker and Peng (1982).
- Almeria-Oran Front
- A front and an associated current that separate the fresher
water flowing in from the Atlantic Ocean via the Gibraltar
Strait from the saltier Mediterranean Sea water to the west.
The incoming water flows eastward as a jet, breaks into one or
two large eddies of around 150 km diameter, and then is deflected
to the right (the south) by the Coriolis force where it encounters
the African coast and continues flowing eastward as the
See Tomczak and Godfrey (1994).
- Acronym for the radar altimeter used on the
The ALT was the first spaceborne dual-frequency altimeter and
is the primary instrument for the mission. Measurements are
made at two frequencies (5.3 and 13.6 GHz) and combined
to minimize the errors caused by the presence of ionospheric
free electrons, the total content of which is obtained as
a by-product of the measurement. This instrument was based
on previous Seasat and Geosat altimeters with several improvements
including the 5.3 GHz channel for the ionospheric measurement,
more precise height measurement, and a longer lifetime.
See Hayne et al. (1994).
- A deep submersible commissioned on June 5, 1964 at the Woods Hole
Oceanographic Institution. It has been used for over a thousand
research and rescue missions in the years since it was first launched,
most from aboard the tender ship Atlantis II, which was retired
from that duty in 1996.
See Kaharl (1990).
- Abbreviation for Amazone Shelf Sediment Study, an international
field program designed to investigate the transport of fresh
water and suspended sediment from the Amazon River into the
See Nittrouer et al. (1991).
- Amazon River
- More later.
- Amazon shelf
- See Geyer et al. (1996).
- Abbreviation for
Atlantic Multidecadal Oscillation.
- Acronym for Acoustic Monitoring of the Ocean Climate in the Arctic
Ocean, a 1994-1998 program whose overall objective was to develop and
design an acoustic system for long-term monitoring of the ocean
temperature and ice thickness in the Arctic Ocean, including
the Fram Strait, for climate variability studies and global warming
The specific objectives included:
- compilation and analysis of existing ocean and ice data from the
Arctic ocean for use in climate and acoustic models;
- simulation of present and future ocean temperature, salinity and
speed of sound fields, ice thickness concentration and extent in the
Arctic Ocean caused by natural variability and global warming scenarios,
as input to acoustic modeling;
- simulation of present and future basin-wide acoustic propagation
using natural variability and global warming scenarios to investigate
the sensitivity of acoustic methods for global warming detection;
- simulation of present and future acoustic propagation in the Fram
Strait to investigate the sensitivity of acoustic methods for monitoring
heat and volume fluxes in an area of strong mesoscale eddy activity; and
- design of an optimum acoustic monitoring system for climate change
detection in the Arctic Ocean.
- Acronym for Acoustic Mid-Ocean Dynamics Experiment, a 1991-1992
experiment involving a tomography array located between Puerto Rico
and Bermuda. The width of the array was abouata 670 km and is consisted
of six mooring acoustic sources and receivers.
The array detected signals of the lowest internal wave modes at
See Dushaw and Worcester (1998).
- Abbreviation for Acoustic Mid-Ocean Dynamics Experiment-Moving
Ship Tomography group.
See AMODE-MST Group (1994).
- amount effect
- A term applied to the relationship between isotopic composition
and monthly rainfall where months with heavy rainfall show different
isotopic concentrations than do months with low rainfall. In
high rainfall months, rain frequency is higher which entails
a higher relative humidity
in sub-cloud air, hence less evaporation
from raindrops. Since the rate of evaporation determines the
isotopic concentrations (the greater the rate the higher the
heavy stable isotope composition), low rainfall months should
show a higher heavy stable isotopic composition than high rainfall
- Abbreviation for Advanced Microstructure Profiler, an
instrument developed at the APL.
- A stationary point around which tides rotate
in a counterclockwise (clockwise)
sense in the northern (southern) hemisphere, i.e. the
point about which the
cotidal lines radiate.
The vertical range of the tide increases with distance
away from the amphidrome, with the amphidrome itself
the spot where the tide vanishes to zero (or almost
This is also called an
See Fairbridge (1966).
- amphridomic point
- See amphidrome.
- Acronym for
Atlantic Meridional Transect programme.
- Acronym for the Air Mass Transformation Experiment, conducted near
Japan in 1974 and 1975.
See Geernaert (1990).
- Amundsen Abyssal Plain
- One of the three plains that comprise the
(the others being the
Plains). It is located at around 150 W.
- Amundsen Sea
- A marginal sea of Antarctica centered at about
112 W and 73 S. It sits between the
to the east and
the Ross Sea to the west, with
the Antarctic Circle serving as the northern boundary.
See Fairbridge (1966) and
Grotov et al. (1998).
- Acronym for A Mediterranean Undercurrent Seeding Experiment, an
experiment taking place from 1993-1995 whose overall objective was
to observe directly the spreading pathways by which Mediterranean
Water enters the North Atlantic, including the direct observation
of Mediterranean eddies, i.e. meddies. The measurements included
repeated high resolution XBT section and
RAFOS float deployments across the
south of Portugal near 8.5W.
A total of 49 floats were deployed at the rate of about two floats
per week on 23 cruises of the Portuguese vessel Kialoa II and
one cruise of the R/V Endeavor. The floats were ballasted for
1100 or 1200 decibars to seed the lower salinity core of the
Undercurrent. The objectives of the float study were:
- to identify where meddies form;
- to make the first direct estimate of meddy formation frequency;
- to estimate the fraction of time meddies are being formed; and
- to determine the pathways by which Mediterranean Water which is
not trapped in meddies enters the North Atlantic.