- Anadyr Current
- A surface current that flows along the northwestern side of
the Bering Sea and on through the
Bering Strait. It is mostly
seasonally invariant with a velocity of about 0.3 m/s.
See Tomczak and Godfrey (1994).
- In signal processing this refers to a continuous physical variable
which bears a direct relationship to another variable so that one
is proportional to the other. An example would be the mercury
level in a thermometer and its relation to the temperature, both
of which vary continuously on the macroscopic level. Contrast
- Andaman Sea
- A body of water in the northeastern corner of the Indian
Ocean that lies to the west of the Malay Peninsula, the
north of Sumatra, the east of the Andaman Islands, and the
south of the Irrawaddy Delta in Burma. It stretches about
650 km from west to east and 1200 km from north to south.
The Andaman communicates
with the westward lying Bay of Bengal through several
channels between the chain of islands that stretches along
93 E., including the Preparis (200 m deep),
Ten Degree (800 m deep) and Great (1800 m deep) Channels.
It is connected with the
Australasian Mediterranean Sea via the
Malacca Strait between Thailand and Sumatra.
It has been variously estimated to have an area of
600,000 to 800,000 km2 and an average and maximum depth of,
respectively, 870-1100 m and 4200 m.
The temperature of the surface waters fluctuates mildly
from a monthly average of about 30 C in the summer months to
one of about 27.5 in the winter months. They drop off with depth
to about 5 C and 2000 m. The surface salinities exhibit
strong seasonal variations due to an extremely large freshwater
influx from the Irrawaddy and Salween rivers during
monsoon season. In the northern
part the salinities range from about 20 during the monsoon
months from June to November to about 32 from Demember to May.
These grade to a fairly constant 33.5 in the southwest end
and to a maximum of about 35 near 1500 m depth.
The steadiest current is the inflow through the Malacca
Straits, averaging around 1/3-2 knots through the year.
The monsoons controls the currents elswhere, driving inflow
waters from the Bay of Bengal through the western channels from
June to August during the southwest monsoon.
This also pushes the Malaccan inflow against
the Sumatran coast and forces some Andaman sea water through
the Straits. When these winds die southwestward currents gradually form
that are maintained and enhanced by the northeast monsoon
from December through February. A more sudden shift is seen from
March through May when the southwest monsoons begins anew.
See Fairbridge (1966).
- anelastic approximation
- A filtering
approximation for the equations of motion that eliminates sound waves
by assuming that the flow has velocities and phase speeds much smaller
than the speed of sound. In its purest form, it requires that the
reference state be isentropic as well as hydrostatic, although in
practice the reference state is often taken to be nonisentropic which
can have deleterious effects on the energy conservation properties
of the full set of equations. The anelastic approximation is one
of the set of approximations used for the somewhat similar
See Ogura and Phillips (1962), Durran (1989), and
Houze (1993), pp. 35-37.
- Angola Basin
- An ocean basin located to the west of Africa at about 15 S
in the south-central Atlantic Ocean.
It is demarcated to the north by the Guinea Ridge, south of
which lies the Angola Abyssal Plain which is fed by the
Congo Canyon, the largest in the eastern Atlantic. This has
also been known as the Buchanan Deep.
See Fairbridge (1966).
- Angola-Benguela Front
- A front, often abbreviated as ABF,
caused by the confluence of the southward flowing
Angola Current and the
northward flowing Benguela Current
near 16 S off the African coast. This can be identified
in the temperature of the upper 50 m and in the salinity to
at least 200 m.
See Tomczak and Godfrey (1994) and
Lass et al. (2000).
- Angola Current
- The eastern part of a cyclonic gyre centered around 13 S and
4 E that is driven by the
South Equatorial Countercurrent in the Atlantic Ocean.
This subsurface circulation gyre extends from just below the
surface to around 300 m depth with velocities of about
0.5 m/s in the section nearest the African coast. The
confluence between this southward flowing current and the
northward flowing Benguela Current
near 16 S off the African coast is called the
See Tomczak and Godfrey (1994).
- Angola Dome
- A small cyclonic gyre, centered near 10 S and 9 E,
driven by the
South Equatorial Undercurrent in the eastern Atlantic Ocean.
It is called a dome due to the elevation or doming of the
thermocline in the middle of
the gyre. This is distinct from the larger gyre that
incorporates the Angola Current.
See Peterson and Stramma (1991) and
Tomczak and Godfrey (1994).
- angular frequency
- The repetition rate of a cyclic process measured in radians/sec.
If the frequency in cycles/sec is f, then the angular
frequency = f.
- angular momentum
- The product of mass times the perpendicular distance from the axis
of rotation times the rotation velocity. The angular momentum about
the Earth's axis of rotation can be expressed as the sum of the angular
momentum of the solid Earth's rotation plus the angular momentum of zonal air
motion relative to the surface of the Earth. Were this quantity to be
absolutely conserved, a parcel of air with the angular momentum of the
Earth's surface at the Equator would have a westerly zonal wind speed
of 134 m/s at 30 latitude.
See Hartmann (1994).
- Descriptor for a physical property (e.g. density, etc.) that
varies depending on the direction in which it is measured.
- Annual El Niño Current (AENC)
- See Cucalón (1987) and
Strub et al. (1998).
- anomaly of specific volume
- Another name for the
specific volume anomaly.
- Antarctic Bottom Water (AABW)
- A type of water in the seas surrounding Antarctica with temperatures
ranging from 0 to -0.8 C, salinities from 34.6 to 34.7, and
a density near 27.88.
ABW is formed in the Weddell and Ross Seas.
This is the densest water in the free ocean,
with the only denser waters being found in regional sill basins
such as the Norwegian Sea or the Mediterranean.
It is overlain by
Antarctic Circumpolar Water (AACW)
at a depth of 1000 to 2000 m [3000 m (Tchernia)]
Weddell Sea Bottom Water (WSBW)
in some locations.
The flow of AABW in the tropical Atlantic is described by
Rhein et al. (1998) as:
About one-third of the northward flowing AABW at 10S
(4.8 Sv) and at 5S (4.7 Sv) west of about 3130'W
enters the Guiana Basin,
mainly through the southern half of the Equatorial Channel at
35W (1.5-1.8 Sv). The other part recirculates
and some of it flows through
the Romanche Fracture Zone
into the eastern Atlantic. In the Guiana
Basin, west of 40W, the sloping topography and the strong,
eastward flowing deep western boundary current might prevent
the AABW from flowing west: thus it has to turn north at the eastern
slope of the Ceara Rise (2.2 Sv). At 44W, north of the Ceara Rise,
AABW flows west in the interior of the basin in a main core near
715'N (1.9 Sv). A net return flow of about 0.5 Sv was found north
of 843'N. A large fraction of the AABW (1.1 Sv) enters the eastern
Atlantic through the
Vema Fracture Zone, leaving only 0.3 Sv
of AABW for the western Atlantic basins.
See Jacobs et al. (1970),
Tomczak and Godfrey (1994),
Tchernia (1980) and
Rhein et al. (1998).
- Antarctic Circumpolar Current (ACC)
- A major eastward flowing current that circles the globe
in the Southern Ocean.
It is principally driven by surface wind stress, although
there is a significant thermohaline component that is not
yet well understood. In the way of vorticity dynamics a simple
Sverdrup balance with dissipative
mechanisms of form drag by bottom
topography and lateral dissipation in western boundary layers
has been found consistent with the data. The present best
estimates of its transport through Drake Passage give a
net mean transport of 125 Sv (with a standard deviation of
10 Sv) above 2500 m.
The transport of the ACC is concentrated in two current
cores separated by a transition zone with surface water
characteristics intermediate between those found to the
south in the Antarctic Zone
and to the north in the
Subantarctic Zone, with
the transition zone being known as the
Polar Frontal Zone. The
maximum geostrophic surface speeds in these cores have
been calculated as 25-45 cm s in
There is also considerable mesoscale
variability in the ACC region due to instabilities causing
both cold and warm core rings to be shed. These eddies have
been found to have spatial scales varying from 30 to 100 km,
surface velocities typically 30 cm s or greater, and
are vertically coherent from surface to bottom. The regions
of highest variability have been found to be correlated
with prominent topographic features on the sea floor.
The ACC is a region of complicated and large meridional
heat flux, with a mean ocean heat loss to the south
estimated at about 0.45 petawatts due to ocean-atmosphere heat exchange
and equatorward Ekman transport.
This is thought to be balanced by the import of heat via
eddy processes and deep boundary currents, although the proportions
are known only vaguely as yet.
See Nowlin, Jr. (1986).
- Antarctic Circumpolar Water (AACW)
- A type of water
in the seas surrounding Antarctica with temperatures ranging from
0 to 0.8 C, salinities from 34.6 to 34.7 ppt, and a depth
range from a few hundred meters to about
1000-2000 m [3000 m (Tchernia)]
It is formed from a mixture of overlying
North Atlantic Deep Water (NADW)
and underlying (at 1000-2000 m)
Antarctic Bottom Water (AABW).
It has a temperature maximum around 500-600 m and a salinity maximum
between 700-1300 m.
This was originally called Warm Deep Water (WDW) by Deacon, but renamed
AACW by Sverdrup.
See Tomczak and Godfrey (1994), pp. 83, 287 and
- Antarctic Circumpolar Wave
- Interannual variations in the atmospheric pressure at sea level,
wind stress, sea surface temperature and sea-ice extent that
propagate eastwards around the
These anomalies propagate with the circumpolar flow with a period
of 4-5 years and taking 8-10 years to circle the pole.
See White and Peterson (1996).
- Antarctic Convergence
- See Polar Front.
- Antarctic Divergence
- In physical oceanography, a region of rapid transition located in the
Antarctic Zone of
Continental Water Boundary
to the south
and the Polar Front to the north.
It can be distinguished hydrographically by a salinity maximum
below about 150 m caused by the upwelling of water of high salinity,
i.e. North Atlantic Deep Water.
Above this the maximum is blurred by high precipitation and the melting
of ice. Its position corresponds reasonably well to the demarcation
between the east and west wind drifts which, in the light of
Ekman dynamics, at least partially
explains its divergent nature.
See Tomczak and Godfrey (1994), pp. 76-79.
- Antarctic Front
- In meterology,
a front which develops and persists around the Antarctic continent
at about 60-65 S, and divides
Antarctic Air from the maritime
Polar Air to the north.
- Antarctic Intermediate Water (AAIW)
- In physical oceanography, a type of water mass
in the Southern Ocean thought to
originate mainly through convective overturning of surface waters
during winter west of South America, after which it is injected into the
subtropical gyre and fills the
southern subtropics and tropics from the east.
In the Atlantic,
the densest SAMW found in the
Subantarctic Zone between the
Subantarctic Front and the
Subtropical Front is thought to be the primary precursor to AAIW,
although some postulate substantial input across the
The AAIW in the South Atlantic originates from a surface region
of the circumpolar layer, especially in the northern
Drake Passage and the
Falkland Current loop. AAIW from the Indian Ocean is added to
the Atlantic AAIW via
Agulhas Current leakage.
The AAIW is recognized by a subsurface oxygen maximum and
a salinity minimum north of about 50S, although the oxygen
maximum becomes weak north of 15S.
The oxygen maximum is found at a slightly lower density than the
The salinity minimum is found at about 300 m near the
Subantarctic Front at around 45S, descends northward to 900 m
at 30S near the subtropical gyre center, and rises again
to 700 m at the equator.
The AAIW spreads to the North Atlantic, identified by a salinity
minimum near the equator at a
value of about 27.3.
This minimum has been found to 24N, although traces of AAIW
can be followed as far north as 60N.
AAIW is characterized by a temperature near 2.2 C and a salinity
around 33.8 near its formation region, but erodes by the time it
reaches the Subtropical Front
to values closer to 3 C and 34.3.
See Piola and Georgi (1981),
Whitworth and Jr. (1987),
Tomczak and Godfrey (1994),
Boebel et al. (1997) and
Schmid et al. (2000).
- Antarctic Polar Front
- See Polar Front.
- Antarctic Polar Frontal Zone (APFZ)
- A concept originated in the 1960s following a detailed study of
the Polar Front.
This was later transformed into the concept of the
Polar Frontal Zone.
See Gordon (1971),
Gordon (1977), and
Belkin and Gordon (1996).
- Antarctic Surface Water (AASW)
- In physical oceanography, a water mass in the
Antarctic Zone of the
AASW is found in the upper 200 m south of the
Polar Front (PF) and is cold, fresh, and high
in oxygen and nutrients relative to the subantarctic surface waters,
although it is high in nutrients compared to underyling waters.
The most easily distinguishable characteristics of AASW in summer
sections is a intense temperature minimum at about 200 m
that marks the base of the winter mixed layer. The water
around this minimum is also commonly known as
Winter Water, and ranges from
50 m deep in the Weddell Gyre to
nearly 1000 m just north of the PF.
It is characterized by very low
temperatures ranging down to the freezing point of -1.9 C and low
salinities as the result of ice melting in the summer in the upper
100-250 m of the water column.
See Tomczak and Godfrey (1994) and
Whitworth and Jr. (1987).
- Antarctic Zone
- A name given to the region in the Southern Ocean
Polar Front to the north and the
Southern ACC Front to the south.
The AZ is one of four distinct surface
water mass regimes in the
Southern Ocean, the others being the
Continental Zone (CZ) to the
south and the
Polar Frontal Zone (PFZ) and
Subantarctic Zone (SAZ) to
See Orsi et al. (1995).
- A research program whose overall objective is to describe and model the
biogeochemical processes controlling the dynamics of nutrients
(C, N, S, P) and silica in the
More detailed objectives include investigating the seasonal ice zone,
deploying arrays of sediment traps, and studying benthic processes.
The first program cruise, ANTARES I, took place from March 29 to
May 18, 1993 on board the R. V. Marion Dufresne.
Stops were made at the Kerguelan and Crozet Islands on a ship
track that traversed an area between 40 and 60 S
and 50 and 75 E in the Southern Ocean.
Hydrographic and nutrient data were acquired with rosette hydrocasts
and CTD and oxygen profiles were obtained with a Neil Brown Mark III B
probe. Various core samples were also taken at a total of 20 stations
where 142 hydrological and coring sampling operations were performed.
See Gaillard (1997).
- An atmospheric pressure distribution in which there is a high central
pressure relative to the surroundings. This term was selected to
imply the possession of characteristics opposite to those found in
a cyclone or depression. As such, the circulation about
the center of an anticyclone is clockwise (counter-clockwise) in
the northern (southern) hemisphere, and the weather is generally
quiet and settled.
- The direction of rotation around a center of high pressure.
This is clockwise in the northern hemisphere and counter-clockwise
in the southern.
- Antilles Current
- More later.
- antitriptic wind
- A type of wind that occurs when the pressure gradient is balanced by
the force of friction. These are the atmospheric analogs of
See Dutton (1986).
- Acronym for the Antarctic Zone Flux experiment, the objective of
which was to measure the magnitude of heat flux through the
air-sea-ice interface and to describe the mechanisms that drive
and control the fluxes of heat, salt and momentum.
It took place aboard the RV Nathaniel B. Palmer in the
Eastern Weddell Sea from June 27 to August 24, 1994.
See the ANZFLUX Web site.
- Abbreviation for
Arctic Ocean Deep Water.
- Abbreviation for atmosphere/ocean general circulation model,
a numerical model that has fully dynamical atmosphere and
ocean components that are somehow coupled.
- Abbreviation for Atmospheric and Oceanographic Information
See Hasler and desJardins (1987).
- Acronym for Arctic Ocean Model Intercomparison Project, an effort designed
to identify systematic errors in Arctic Ocean models under realistic
The main goals of the proposed research are to examine the
ability of Arctic Ocean models to simulate
variability on seasonal to interannual scales, and to qualitatively
and quantatively understand the behaviour of different Arctic Ocean
AOMIP's major objective is to use a suite of sophisticated models to
simulate the Arctic Ocean circulation for the periods
1946-1998 and 1899-1998. Forcing will use the observed climatology
and the daily atmospheric pressure and air temperature fields.
Model results will be contrasted and compared to understand model
strengths and weaknesses.
- Abbreviation for
Atlantic Oceanographic and Meteorological Laboratory.
- Acronym for Arctic Ocean Section.
- Abbreviation for Arctic Ocean Sciences Board, a non-governmental body
including members and participants from research and governmental
institutions from several nations.
The long-term mission of the AOSB is to facilitate Arctic Ocean
research by the support of multinational and multidisciplinary natural
science and engineering programs.
It was established in May 1984.
- Abbreviation for
Autonomous Ocean Sampling Network, a
project whose long-term goals are to create and demonstrate a reactive
survey system capable of long-term unattended deployments in harsh
The scientific objectives include:
See Curtin et al. (1993).
- to create small, high performance mobile platforms capable of
deployments lasting for several months, with both propellor-driven,
fast survey vehicles and buoyancy-driven glider vehicles being developed;
- to create an infrastructure that supports controlling, recovering
data from, and managing the energy of remote deployed mobile platforms,
with structure elements including moorings, docking stations, acoustic
communications, two-way satellite communcations, and the Internet;
- to demonstrate these capabilities in science-driven field
- to develop adaptive sampling strategies to most efficiently meet
- Abbreviation for Apparent Oxygen Utilization, defined as the
difference between the observed oxygen content and the saturation
oxygen content of a sample of sea water. This is a method
of estimating the amount of dissolved oxygen utilized by
organisms via respiration, although it is called "apparent"
for a reason. Surface waters may more than likely carry
more than the saturation amount of oxygen due to the nonlinearity
in the solubility of oxygen with temperature. The effects of
this nonlinearity are small, though, and the AOU is usually
quite close to TOU, the True Oxygen Utilization.
See Broecker and Peng (1982).
- Acronym for East Asian/North Pacific Regional Experiment, an
The scientific goals of APARE are to quantify the oxidising
efficiency, and atmospheric
acidification by studying the emission, transport,
chemical transformation, and deposition
of primary and secondary chemical species over the
East Asian Continental Rim Region
and northwestern Pacific Ocean.
The objectives are:
- to assess transport and chemical transformations of air
pollutants over the East-Asian
continent and the northwestern Pacific Ocean, with particular emphasis
on distribution and photochemistry of reactive species to understand
oxidizing efficiency and the 03 budget in the region; and
- to determine the deposition of primary and secondary pollutants
in the East Asian region, with major emphasis on understanding the present
status and future prospects of acidification of the atmosphere and
deposition of acidic species in the region.
for available potential energy.
- Acronym for Arctic Polynya Experiment.
See Pease et al. (1985).
- Abbrevation for
Antarctic Polar Frontal Zone.
- aphotic zone
- The region below the
euphotic zone where no light
is available for photosynthesis.
- Abbreviation for Association of Physical Oceanography, the name of
what is now known as the IAPSO from
1929 to 1948.
- Acronym for Advances and Primary Research Opportunities in Physical
Oceanography Studies, a
workshop for physical oceanographers
held at Monterey, California from December 15-17, 1997.
The goal was to evaluate the current status of research in
physical oceanography and to identify future opportunities and
Similar workshops were held at the time for
biological oceanography (sf OEUVRE),
ocean chemistry (FOCUS) and
marine geology and geophysics (FUMAGES).
Future directions and problems mentioned in the final report included:
- the difficulties inherent in global climate prediction wherein
the decadal timescale only allows scientists to observe a few realizations
in their lifetimes, and the need to circumvent this by expanding the
current database and framing hypotheses about past climate change and
ocean circulation using paleoceanographic studies;
- better understanding the ocean's role in the hydrologic cycle;
- advancements on fundamental issues such as the causes of
the temperature-salinity relationship, thermocline maintenance, and
interhemispheric water mass exchanges;
- the increasing use of observational tools such as satellites and
tomography to obtain large-scale, detailed and long-term measurements
of the oceans;
- emerging issues concerning connections between large- and small-scale
motions, e.g. between small-scale turbulent mixing and large-scale
meridional overturning circulation;
- better understanding of the processes involved in cross-shelf
- increased understanding of inland waters such as estuaries, wetlands,
tide flats and lakes will probably lead to progress on the general
- unraveling the connections between the spatial and temporal
distribution of turbulent mixing, the large-scale meridional
overturning circulation, and climate variability;
- radical advances in knowledge of the structure of the ocean on
scales between the mesoscale (50 km) and the microscale (less than
10 m) via the use of towed and autonomous vehicles; and
- general circulation model components greatly in need of improvement
include deep convection, boundary currents and benthic boundary layers,
the representation of the dynamics and thermohaline variability of the
upper mixed layer, fluxes across the air-sea interface, diapycnal
mixing and topographic effects.
- A U.K.-led, international program of upper-ocean biogeochemistry
investigations in the
Arabian Sea region.
It was conducted during two contrasting seasons, i.e. the waning of
the southwest monsoon in August/September, and the intermonsoon-northeast
monsoon transition in November/December 1994.
Biogeochemical studies were carried out along three transects in the
Gulf of Oman and the Arabian Sea, with the main transcect, 1590 km in
length, orthogonal to the southern Oman coast.
See Burkill (1999).
- Arabian Gulf
- See Persian Gulf.
- Arabian Sea
- A regional sea, centered at approximately 65 E and 15 N,
that is bounded by Pakistan and Iran to the north, Oman, Yemen and
the Somali Republic
to the west, India to the east, and the greater
Indian Ocean to the south.
The southern boundary, from an oceanographic point of view,
runs from Goa on the Indian coast along the west side of the
Laccadive Islands to the equator, and thence slightly to the
south to near Mombasa on the Kenyan coast. It covers an area
of about 7,456,000 km.
The flow pattern in the Arabian Sea is seasonal, changing with
the monsoon winds. In the northeast monsoon season (from November
until March) the winds are light and the surface circulation
is dominated by a weak westward, counter-monsoon flow
(as an extension of the
North Equatorial Current)
with velocities usually under 0.2 m/s. This pattern starts in
November with water supplied by the
East Indian Winter Jet
flowing around the southern tip of Indian and heading northwestward
along the western Indian shelf.
Westward flow dominates in the southern
parts until late April with the north gradually shifting into a
weak anticyclonic pattern. With the advent of the southwest monsoon
in April, the Somali Current and
its northward extension, the
East Arabian Current, both develop
into strong, northeastward flowing currents by mid-May.
The anticyclonic pattern in the eastern Arabian Sea is
simultaneously being gradually replaced by a moderate eastward
flow composed of extensions of the Somali Current and the
Southwest Monsoon Current.
This pattern lasts for 4-5 months, peaking in June and July at
about 0.3 m/s and weakening rapidly in October as the eastward
flow around southern India once again pushes northwestward.
From May to September there is strong upwelling in the East Arabian
Current along Oman, accompanied by a 5 C or more lowering
of coastal temperatures due to the cold upwelling water. This
upwelling isn't as conducive to primary production as elsewhere
due to the rapidly moving current removing much of the upwelled
additional biomass before it can be utilized.
See Qasim (1982) and
Schott and Fischer (2000).
Arabian Sea Study Web site.
- Arabian Sea High Salinity Water (ASHSW)
- See Kumar and Prasad (1999)
- Arabian Sea Process Study (ASPS)
- A 1995 JGOFS program.
See Shi et al. (1999).
- Arafura Sea
- Part of the southeastern
Australasian Mediterranean Sea centered at about 10 S
and 137 E. It is bounded by Irian Jaya and Papua/New Guinea
to the north and northeast, the Timor Sea to the
west, and Australia and the
Gulf of Carpenteria to the
south and the southeast.
It is mostly a large shelf (covering about 650,000 km)
ranging from 50 to 80 m deep,
although it can get as deep as 3650 m to the northwest in the
There is a steady westward flow along the southern side of the
Sunda Islands that is part of the larger pattern of throughflow
through the Australasian Mediterranean from the Pacific to the
Indian Ocean. South of this the circulation varies with the
monsoon and trade winds that drive it. The deep water is
renewed from the northwest via the Timor Trough.
Sea surface temperatures range from a maximum of 28.4
in Dec.-Feb. to a minimum of 26.1 in Jun.-Aug., while
salinities annually range from 34.2-34.8 in the deeper parts
to the north to 34.2 to 35.0 on the Arafura Shelf.
See Fairbridge (1966) and
Tomczak and Godfrey (1994).
- Aral Sea
- See Zenkevich (1957) and Zenkevitch (1963).
- A French research program to observe and model the movement of
the Mediterranean Water (MW) in
the eastern North Atlantic Ocean in the interior and along the
eastern boundary. It is a joint civilian and military exercise taking
place between 40 and 50 N with most of the work to be done
east of 14 E up to the 200 meter isobath, although some float
work will take place out to 25 W to link with the proposed
U.S. RAFOS deployments in this region.
The plans call for the release of 60 RAFOS
and 40 MARVOR floats. Also deployed will
be 7 acoustic sources for tomographic work, 40 drifting buoys
drogued at 150 meters mostly on the continental slopes of the
Iberian Peninsula, 6 current meter moorings (with a total of 27
current meters) on and near the continental slopes of the Iberian
Peninsula for 3 years, and a bottom mounted
ADCP to be moored for several 3 month
periods. This program is scheduled to last until 1999 and is
a companion program to EUROFLOAT.
- Abbreviation for ARCtic System Science, an NSF
global change program. The goals of ARCS are to understand the
chemical, physical, biological and social processes of the arctic
system that interacts with the total earth system and thus
contributes to or is influenced by global change in order to
advance the scientific basis for predicting environmental change
on a decade to centuries time scale.
ARCSS Web site.
- See Richez (1998).
- Arctic Atmosphere Program (AAP)
- A component of ACSYS whose goal is to better
understand the Arctic atmosphere that provides the dynamic and
thermodynamic forcing of the Arctic Ocean circulation and sea ice.
The objectives of AAP include:
- to encourage intercomparisons of reanalysis efforts and the
assembly of long-term datasets from these intercomparisons;
- to identify shortcomings and implement improvoed parameterizations
in the atmospheric modeling systems used for future reanalysis efforts
and in climate models;
- to promote intercomparisons of the high latitude performance of
- to promote the quality control, archiving, updating, publication
on CD-ROM, and migration to relevant data centers of key atmospheric
- to promote strategies for rescue of at-risk atmospheric datasets; and
- provide a polar clouds and radiation program through the
GEWEX Clouds and Radiation Panel and other
- Arctic Bottom Water
- In physical oceanography, a water mass type
which fills the deep basins in the Arctic Sea at depths less than
3000 m. Its formation process
involves the interplay of two sources, GSDW
and water from the Arctic shelf regions. The salinities of ABW
are generally close to 34.95 but highest in the Canada Basin. The
potential temperature in most basins is between -0.8 C and
-0.9 C, although the Lomonossov Ridge prevents ABW colder
than -0.4 C from entering the Canada Basin. Its main impact
in the overall ocean circulation is its contribution to the formation
of NADW in the depth range between 1000 m
and 4000 m.
See Tomczak and Godfrey (1994), pp. 99, 282.
- Arctic Circumpolar Boundary Current (ACBC)
- The main water transformations in the Arctic Mediterranean take
place in a boundary current of Atlantic Water, which enters the
Arctic across the Greenland-Scotland Ridge. After entering, it
flows around the Arctic Ocean before exiting as the East Greenland
Current, primarily via the Denmark Strait.
On route, it experiences many branchings and mergings.
The details of its journey around the
Arctic are summarized by Rudels et al. (1999):
The circulation is dominated by the movement of warm Atlantic Water
entering across the eastern part of the Greenland-Scotland Ridge
into the Norwegian Sea. It flows
along the Norwegian coast as the Norwegian Atlantic Current. When it
reaches the latitude of the Bear Island Channel, its first major
bifurcation occurs. A substantial fraction flows eastward and enters
the Barents Sea, while
the main part continues northward as the West Spitsbergen Current.
Several branches are deflected westward from the current: north
of the Greenland Sea basin, north of the Boreas basin and in Fram
Strait. Only a smaller part of the West
Spitsbergen Current eventually enters the Arctic Ocean and flows
eastward along the Eurasian continental slope. North of the Kara Sea
the boundary current meets the branch that turned east and entered
the Barents Sea north of Norway. This branch reaches the Arctic Ocean
by crossing the Barents Sea and the northern part of the Kara Sea.
The combined boundary current continues eastward
a short distance before it again splits. Branches leave the continental
slope along bathymetric features, particularly along the
Nansen-Gakkel Ridge, the Lomonosov Ridge
and the Mendeleyev Ridge.
However, a part of the boundary current follows
the continental slope around the entire Arctic Ocean. As this part
recrosses the Lomonosov Ridge into the Eurasian Basin it meets and mixes
with the other branches as they converge east of the Morris Jesup
Plateau. The waters exit the Arctic Ocean through Fram Strait, where
they combine with the recirculating waters of the West Spitsbergen
Current to continue southward along the Greenland continental slope
as the East Greenland Current. The boundary current again diverges at
bathymetric features, in this case the Greenland Fracture Zone and the
Jan Mayen Fracture Zone, and branches from the boundary current enter
the interior of the Boreas Basin and the Greenland Sea Basin.
Exchanges in both directions
occur, and the East Greenland Current is resupplied with water masses
formed in the subpolar seas. The main part of the boundary current
exits the Arctic Mediterranean through the 600 m deep Denmark Strait, but
its denser fractions are deflected eastward along the Jan Mayen
Fracture Zone and along the Iceland shelf slope and eventually
enter the Norwegian Sea. The upper part of these waters then
returns to the North Atlantic through the 850 m deep Faeroe-Shetland Channel.
See Rudels et al. (1999).
- arctic domain
- A hydrographic division sometimes used in the North Atlantic Ocean
to distinguish it from the polar domain
to the north and the Atlantic domain
to the south. In this region upper layer waters are relatively
cold (0 to 4 C) and saline (34.6 to 34.9). The most
significant indication that this domain is not just a smooth
transition zone between the polar and Atlantic domains is that
the waters are markedly denser than either of the surface source
(i.e. ranges from 27.5 to greater than
See Swift (1986).
- Arctic Frontal Zone (AFZ)
- A frontal zone that runs meridionally between about
5 and 8 E in the
It separates warm, salty, northward-flowing
Norwegian Atlantic Water (NwAtW) in the
Norwegian Atlantic Current and the
West Spitsbergen Current to the east from the
cooler and fresher
Arctic Surface Water (ASW)
in the Greenland Sea gyre to the west.
The AFZ consists of two semipermanent frontal interfaces
with warm, saline Norwegian Atlantic Water to the east
and Arctic Water from the Greenland Sea gyre to the west.
These two interfaces bound a band of shallow cyclonic
cold eddies and anticyclonic warm eddies with
horizontal scales on the order of 40-50 km, consistent
with the local Rossby radius.
Drifter trajectories show a mean surface velocity across the
AFZ to the north, and the mean northward geostrophic transport
(relative to 1000 dbar) connected with the zonal density
gradient in the AFZ is about 3.8 Sv.
The accompanying transports of heat and fresh water across
the AFZ are thought to be of great importance for the control
of deep convection processes in the Greenland Sea gyre.
See van Aken (1995).
- Arctic Intermediate Water (AIW)
- A water mass found at intermediate
depths in the arctic domain
in the North Atlantic Ocean.
It is identified by a
temperature minimum at a depth of about 75 to 150 m as
well as temperature and salinity maximums at depths
ranging from about 250 to 400 m, with the extremes being the
product of winter cooling and sinking in the arctic domain.
It is useful to separate this water mass into lower and
The lower AIW contains the temperature and salinity maximums but
generally not the temperature minimum, with temperatures ranging
from 0 to 3 C and salinities greater than 34.9, with
the maximums clear signs that this water mass is produced by the cooling
and sinking of Atlantic Water (AW).
The upper AIW is defined as including the denser portion of the water
associated with the temperature minimum, including much of the water
column from the minimum up to the temperature maximum.
It is characterized by temperatures less than 2 C in the
salinity range 34.7 to 34.9 (with a lower limit of 34.6 suggested
The definitions for upper and lower AIW deliberately overlap
in density, with upper AIW in the Iceland Sea
having a temperature of 0 C, S = 34.88 and = 28.03
as opposed to a portion of the lower AIW in the northern Greenland
Sea having T = 3 C, S = 35.05, and = 27.95.
This is only true of the northeastern Greenland Sea, however.
Elsewhere, upper AIW always overlies lower AIW.
See Swift (1986).
- Arctic Mediterranean Sea
- The area comprising
the Greenland Sea,
the Iceland Sea,
the Norwegian Sea and
the Arctic Ocean.
The first three are sometimes referred to as the
The area has restricted communication with the rest of the world
ocean, with the passages being:
- to the Pacific via the Bering Strait;
- to the North Atlantic via the Greenland-Scotland Ridge; and
- through the Canadian Arctic Archipelago and the Davis Strait
west of Greenland.
- Arctic Ocean
- The smallest and most poorly studied of the oceans on earth.
It covers an area of 14 million square km that is divided
by three submarine ridges, i.e. the Alpha Ridge, the
Lomonosov Ridge, and an extension of the mid-Atlantic ridge.
It is also nearly landlocked, covered year-round by pack
ice, and one-third of its area is continental shelf containing
marginal seas. The marginal seas of the Arctic are
the Beaufort Sea,
the Chukchi Sea,
the East Siberian Sea,
the Laptev Sea,
the Kara Sea and
the Barents Sea.
An important climatic function of the Arctic and its adjacent
seas is the production of the dense water than drives the global
transports of heat and fresh water between the high latitude
North Atlantic and the Pacific.
The physical processes that combine to produce the circulation
in the Arctic and its marginal seas include:
See Coachman and Aagaard (1974).
- salt rejection from sea-ice growth forming dense water that
continues surface buoyancy forcing after the freezing point is reached,
preferentially where offshore winds maintain open waters for prolonged
- advection of ice produced in marginal seas that exports fresh
water from the basin, compensating for the freshening effect of
precipitation and run-off from Arctic rivers; and
- drainage of dense shelf water from the Arctic shelves into the
deep Eurasian basin, a process that affects the deep water properties
in the convective gyres via exchanges through the Fram Strait.
- Arctic Ocean Circulation Program (AOCP)
- A component of ACSYS designed to investigate
the feedback between changes in the upper
Arctic Ocean and its ice cover and
changes in the global heat balance.
The AOCP consists of four components:
- Arctic Ocean Hydrographic Survey - A program to collect a high quality
hydrographic database representative of the Arctic Ocean with the goal of
determining the general circulation and its transit times, and the rate
of transformation of the different water masses.
- Arctic Ocean Shelf Studies - A program aimed at understanding how
the shelf processes partition salt and fresh water components, how
the resulting buoyancy fluxes are coupled to the ocean interior, at
defining the dynamics and thermodynamics of the shelf waters sufficiently
to permit realistic modeling, and at determining the variability on the
shelves and how that affects the interior ocean.
- Arctic Ocean Variability Project - A program designed to assess the
variability of the circulation and density structure of the Arctic
Ocean including exchanges with the surrounding seas, to find the rates
and variability of the processes important in maintaining present
ocean conditions, and to provide a basis for further monitoring of
climate change in the Arctic.
- Arctic Ocean Climate Database Project - A project to establish a
universally available digital hydrographic database for the Arctic Ocean
for analysis of climate-related processes and variability, and to
provide a dataset suitable for the initialization and verification
of Arctic climate and circulation models.
- Arctic Ocean Deep Water (AODW)
- See Swift (1986).
- Arctic Ocean Section (AOS)
- A 1994 expedition in which two icebreakers - the USCGC Polar Sea
and the CCGS Louis S. St. Laurent - sailed from Nome, Alaska to
the North Pole across the entire Arctic basin, covering over 2000
The purpose of AOS was the increase understanding about the role of the
Arctic in climate change and gather baseline data on contaminants in
See Tucker and Cate (1996) and
Wheeler et al. (1996).
The significant science findings of the expedition were:
- the Atlantic layer of the Arctic Ocean
was found to be 0.5-1.0C warmer than prior to 1993;
- a large eddy of cold fresh water was found centered at 1000 m on the
periphery of the Makarov Basin;
- biological productivity was estimated to be ten times greater than
- an active microbial community was found; and
- mesozooplankton biomass was found to increase with latitude.
- Arctic Sea Ice Program (ASIP)
- A component of ACSYS whose objectives are:
The elements of the implementation strategy include:
- to assemble a climatological archive which documents the state of
pack ice in both the Arctic and Antarctic seas; and
- to study the interaction of polar pack ice with other elements
of the global climate system.
- assembling a climatology of Arctic and Antarctic sea ice based on
available historical observations and new observing initiations within
- determining the southward flux of pack ice;
- studying the processes by which pack ice, the ocean and the atmosphere
- studying sea ice mechanics at spatial scales ( 1 km) relevant to
its behavior in a geophysical context.
- Arctic Surface Water (ASW)
- A water mass found in the
arctic domain in the
North Atlantic Ocean. The ASW is the summer surface water
mass above the seasonal thermocline and has temperatures
greater than 0 C for the salinity range 34.4 to 34.7 and
greater than 2 C for the range 34.7 to 34.9.
See Swift (1986).
- Argentine Basin
- An ocean basin located in the western South Atlantic Ocean
off the coast of Argentina. It is separated from the
Brazil Basin to the north
by the Rio Grande Rise and includes the
Argentine Abyssal Plain.
See Fairbridge (1966).
- A global array of 3,000 free-drifting profiling floats that will
measure the temperature and salinity of the upper 2000 m of the ocean.
This will allow the continuous monitoring of the climate state of
Once the full network is in place in 2002 or thereabouts, Argo will
provide 100,000 T/S profiles and reference velocity measurements
per year from floats distributed over the oceans at about a 3 degree
spacing. The floats will cycle to 2000 m depth every 10 days, with a
planned 4-5 year lifetime for individual instruments.
All data will be made publicly available in near real-time via
the GTS, and in scientifically quality-controlled
form within a few months.
- An isotope of argon that is useful as a tracer in ocean studies.
It is a radioactive inert gas with a half life of 269 years and is
produced in the atmosphere by cosmic ray interactino with Argon-40.
It is well-mixed through the troposphere and its variation in
concentration over the last 1000 years has been estimated to be
no more than about 7%. This means that its distribution in the
atmosphere and ocean is in steady state.
It enters the ocean by gas exchange with the equilibrium time
between the surface mixed layer and the atmosphere being about
a month. The equilibrium concentration in surface water is calculated
from the solubility of argon, a well known function of temperature
and salinity, and the also well known concetration of Ar-39 in the
atmosphere. The surface concentration in regions of deep water
formation, where the surface water may not equilibrate with the
atmosphere due to rapid convection processes, can be determined
from measurements. Measurement is at present an onerous process
requiring 1500 liters of water, and the concentration measured
is reported in % modern, i.e. the Ar-39:Ar:40 ratio of the
sample divided by the Ar-39:Ar:40 ratio of the troposphere.
The minimum detectable limit is about 5% modern (with an
error of 3-5% modern) which corresponds to an age of 1100
years with a resolution of about 50 years.
Argon-39 is an ideal tracer for investigating mixing and circulation
in the deep ocean and in the mid to lower thermocline. Its distribution
is in steady state and the boundary conditions are well known, i.e.
there is no flux across the ocean bottom and the surface water
concentration is known everywhere. Its distribution in the ocean
interior is affected only by circulation, mixing and radioactive
decay process, and since the decay rate is know it serves as a clock
for circulation and mixing processes.
See Loosli (1983), Sarmiento (1988) and
Broecker and Peng (1982).
- Acronym for Autosampling and Recording Insrumental Environmental Sampler,
a multi-function sampling device providing high resolution concurrent
sampling of physical, chemical and biological parameters throughout the
water column from a moving ship.
ARIES is modular, being composed of a water sampling unit, a plankton
sampling unit and an oceanographic sensor unit.
See Dunn et al. (1993).
- Arlindo Project
- A joint oceanographic research endeavor of Indonesia and
the United States whose primary goal is to study the circulation
and water mass stratification within the Indonesian Seas, especially
to determine sources, pathways, and mixing histories of the
throughflow water masses for the monsoon extremes.
``Arlindo'' is an acronym for Arus Lintas Indonesia, meaning
``throughflow'' in the Bahasa Indonesian language.
The first stage of the project, Arlindo Mixing, consisted of a suite of
CTD measurements extending to the seafloor or 3000 dbar, tracer
chemistry, and biological productivity stations obtained
from the Indonesian research vessel Baruna Jaya I
during the southeast monsoon of 1993 (Aug. 6 to Sept. 12)
and northwest monsoon of 1994 (Jan. 25 to Mar. 3).
The results have been summarized as:
The primary interocean throughflow path in the upper thermocline is that
of North Pacific thermocline water flowing through the
Makassar Strait into the Flores and
southern Banda Seas before curling southward into the
Timor Sea and Indian Ocean. This path tracks the mostxi
persistent course of water masses core layer indicators
along a potential throughflow pathway. Even in the
southern Banda Sea the North Pacific core layer
indicators are evident, albeit very attenuated; they are not observed
in the northern Banda Sea, which attests to the Makassar/Flores
origin. The sill at the southern end of Makassar Strait
is about 550 m deep. No signs of deep water
upwelling lifting over the sill is evident. An attenuated,
fragmented thermocline salinity and CFC maximum layer in
Makassar Strait during the NWM relative to the
SEM, suggests that the throughflow slackens in that season,
allowing accumulative effects of local mixing.
East of Sulawesi there is little evidence of North
Pacific water mass throughflow into the Banda Sea. The
North Pacific thermocline water entering the northwest
corner of the Maluku Sea, exits back to the north in
the northeast corner of the Maluku Sea. The presence of
relatively salty water of South Pacific origin is observed in
the 10°-14°C interval in the Seram Sea. This water enters
the Seram Sea directly from the South Pacific via the
New Guinea Coastal Current and Halmahera Sea (sill
depth near 500 m). Below the thermocline the main source
of the throughflow is South Pacific water masses, though
they are derived from a more indirect route, via the
North Pacific's Mindanao Current, entering the Indonesian
Seas at the Maluku Sea. It is this water that spills over
the 1940 m deep Lifamatola Sill into the depths of
the Banda Sea.
The second stage was called Arlindo Circulation, whose goal was to resolve
the throughflow transport and velocity field across the central passages
of the Indonesian Seas. It took place from Nov. 20-Dec. 15, 1996 and
Feb. 17-Mar. 7, 1988.
The third stage is called Arlindo Monitoring and is intended to provide
a long term data set of the throughflow to enable study at timescales of
ENSO events. It is scheduled from 1998 to 2007.
See Ilahude and Gordon (1996).
- Arons, Arnold (1916-2001)
- Co-creator of the Stommel-Arons theory of deep circulation.
- arrested salt wedge estuary
- One of four principal types of estuaries
as distinguished by prevailing flow conditions.
This is a type in which there is
a relatively stationary interface between an underlying stable
salt wedge of sea water and an overlying strong flow of fresh
- Acronym for the Air-Sea interaction, Cloud And Precipitation experiment
over the Baltic Sea, a component of
ASCAP is a comprehensive campaign for an air-sea interaction field
campaign in the Baltic Sea, with the central aim being to improve
model parameterization schemes via a better understanding of the
physical mechanisms and validation of remote sensing algorithms.
The objectives are:
The measurement phase took place from 1995 until 1997.
- measurements of parameters determining air-sea interaction processes,
the sea state, and wave spectra;
- in-situ measurements and observations of clouds, water vapor and
- parameterization of air-sea interaction processs in region models;
- validation of algorithms to estimate cloud parameters, water vapor and
precipitation from radar and satellite data; and
- validation of numerical models against long-term measurements.
- Acronym for Association of Southeast Asian Marine Scientists.
- aseismic ridge
- An undersea ridge that is not seismically or volcanically
active. Examples of aseismic ridges are the Walvis Ridge,
the Rio Grande Plateau, the Kerguelen Plateau, the
Seychelles Ridge and the Lomonosov Ridge.
See Fairbridge (1966).
- An acronym that is the contraction of ASGAS-EX (for Air Sea Gas
Exchange project) and MAGE.
The ASGAMAGE project started on March 1, 1996 and lasted until
March 1, 1999.
The scientific objectives were:
- to find relationships between the transport coefficients for the
gas fluxes and any relevant geophysical parameters;
- to test new methods and new equipment for the measurement of
air-sea fluxes of CO, DMS and other gases;
- to intercompare different methods and systems to measure the
transfer velocity of trace gases over the sea; and
- to find out whether and, if at all, under what conditions there can be
a significant vertical gradient in the CO concentration in the
upper meters of the water column.
ASGAMAGE consisted of two experimental periods, with the first taking place
from May 6 to
June 7, 1996. It involved taking measurements at and around the
Meetpost Noordwijk (MPN), a research platform 9 km off the Dutch coast.
The second period, taking place from Oct. 7 to Nov. 8, 1996, involved
more measurements at MPN and a cruise of the RRS Challenger.
The measurement activities were primarily aimed at a determination
of air-sea gas transfer coefficients with the differential
tracer method being made simultaneously with micrometeorological
- Acronym for Axial Seamount Hydrothermal Emissions Study.
- Abbreviation for
Arabian Sea High Salinity Water.
- Acronym for Asian Sea International Acoustics Experiment, a scientific
collaboration between the U.S., China, Korea, Japan, Taiwan, Russia and
Singapore. The ASIAEx major field experiments began in 2000, one focusing
on acoustic bottom reverberation and the other on acoustic cross-shelf
- Asia Minor Current (AMC)
- A meandering current flowing westward and then northward
along the Turkish coast and
the southeastern coast of Rhodes.
It borders the northwest part of the Rhodes gyre, and
originates as part of the mid-Mediterranean jet branching to the north.
There is a major branch in the AMC in the region of the Rhodes and
Karpathos Straits. Both branches intrude into the south
Aegean Sea and meander in the northeastern
Cretan Sea as a continuation of the AMC.
The branches carry warm and saline Levantine waters within the
upper 300-400 dbar layer.
See Theocharis et al. (1999).
- Acronym for the American Society of Limnology and Oceanography,
the purposes of which are to promote the interests of limnology,
oceanography and related sciences, to foster the exchange of
information across the range of aquatic science, and to further
investigations dealing with these subjects.
ASLO originated with the Limnological Society of America (LSA),
which was established in 1936 to furhter interest and research in
In 1948 LSA merged with the Oceanographic Society of the Pacific
to become ASLO, and currently has over 3800 memebers from 50 countries.
See the ASLO Web site.
- Acronym for Acoustic Surface Reverberation Experiment.
- See Arctic Surface Water.
- Acronym for Atlantic Trade Winds Experiment, an experiment designed
to study the development of the boundary layer in the trade winds
near the ITCZ.
It was conducted in 1969 and based on a triangle of ships drifting with
the NE trades. Spatial structures of the boundary layer were
Air-sea fluxes were measured by the profile method and the
eddy correlation technique was used on two separate buoys, i.e. a
stable, wave-following buoy for profiles and a servo-stabilized
buoy for eddy fluxes.
Sea Dunckel et al. (1974) and
- Atlantic domain
- One of three regions into which the North Atlantic Ocean is sometimes
divided for the purposes of describing water mass formation processes
in the region, with the other two being the (northward lying)
arctic domain and the
Surface source water masses from the Atlantic
domain (called Atlantic Water (AW),
are carried into the arctic domain by the
Norwegian Atlantic Current
and, to a much smaller extent, by the
North Icelandic Irminger Current.
See Swift (1986).
- Atlantic Multidecadal Oscillation (AMO)
- A 65-80 year cycle with a 0.4C range
observed in North Atlantic sea surface temperature
AMO warm phases occurred during 1860-1880 and 1940-1960, with
cool phases during 190-1925 and 1970-1990.
The signal is global in scope, with a positively correlated co-oscillation
in parts of the North Pacific, although it is most intense in the
North Atlantic and covers the entire basin.
During AMO warmings most of the U.S. experiences less than
normal rainfall, including Midwest droughts in the 1930s and 1950s.
Mississippi River outflow varies by 10% between warm and cool phases.
The geographical pattern of variability is influenced mainly by
changes in summer rain.
Winter patterns of interannual rainfall variability associated with
ENSO are significantly changed between AMO phases.
- Atlantic Ocean
- Much more later.
Peterson and Stramma (1991) and
Stramma and England (1999).
- Atlantic-Indian Basin
- One of three major basins in the
Southern Ocean. It extends
from its western border with the
at the Scotia Ridge and
Drake Passage (at about 70 W) to
its eastern border with the
at the Kerguelan Plateau
(about 75 E).
It consists of the Enderby and Weddell
Abyssal Plains and is bounded to the north below 4000 m
by the Mid-Atlantic and South-West
Indian Ridges except for deeper connections into the
Argentine Basin in the western Atlantic and into the deep
basins of the western Indian Ocean.
- Atlantic Meridional Transect
- An ongoing research program that exploits the twice-annual passage of
the RRS James Clark Ross between the U.K. and the Falkland
Islands - before and after its use in the Antarctic research program
in the Austral Summer - to obtain spatially-intensive time and space
series data over the 13,500 km transect.
The transect starts at the U.K. and heads southwest to the first
waypoint at a JGOFS time-series station at
47N, 20W. From there it follows the 20W meridian
to 13N, after which it heads south and west to Montevideo (Uruguay)
and Stanley (Falkland Islands).
The objectives of the AMT program include:
- gauging the effects of anthropogenically induced environmental
change on the physical and biological systems along the transcent;
- improving knowledge of marine biogeochemical processes, ecosystem
dynamics, food webs and fisheries, as well as characterize physical
and biogeochemical provinces;
- developing a research strategy to integrate shipboard
measurements with remote sensing, modeling, etc. to maximally exploit
the time and space series obtained on the transect;
- providing calibration and validation of satellite sensors of ocean
color, sea surface temperature, and solar radiation;
- quantifying ecosystem responses to changes in the abundance of
radiatively and chemically active trace gases; and
- developing coupled physical-biological models of production and
The progress and limitations of AMT as of 2000 has been synthesized by
Aiken et al. (2000) as:
AMT cruises 1 to 7 (1995-1998) have seen the completion of phase
1 of the AMT programme, wherein many of the new, autonomous
technologies and operational approaches have been pioneered
and proven. There are obvious limitations in the programme, particularly
one which has objectives related to issues of climate change.
Notably, the physical oceanography is superficial, CTD casts have been
limited to 200 m in most cases with no geostrophic reference and
the spatial resolution of circa 400 km from typically 1 cast per day is
too coarse. As a basin scale programme the AMT samples the temperate
N. Atlantic poorly; there is no sampling north of 50N. As a
programme focused on climate change, a time series based on samples
only twice a year has severe limitations, with no adequate
resolution of the seasonal cycle in any province. Nevertheless, the
fledgling four-year time series can already provide measurements of
inter-annual variability, which is an essential pre-requisite for
any study of decadal trends. With another 10 cruises planned over five
years (1999-2003) during phase 2, the basis of a study of climate
change will be well established. During this period there must be a
focus on those measurements that are sensitive to climate forcing or
are known indices of anthropogenic influences on climate.
Collaboration with other European national research activities is
planned to improve the coverage of the seasonal cycle in the north
Atlantic and create a European Atlantic Time and Space
project. Core to this are the twice yearly transects of the other
Antarctic research vessels, the Polarstern (Germany), the Hesperides
(Spain) and the Pelagia (Netherlands) with opportunistic
research cruises in the area 20-63N, 20W, by UK,
Dutch, Belgian and Spanish vessels. If this develops, it will be
true to say, that the AMT programme has laid down the foundation
for a study of decadal trends in the marine ecosystems of the
Atlantic Ocean with which to understand and model their responses
to climate change.
See Aiken and Bale (2000) and the other papers in a special AMT
- Atlantic period
- A post-LGM European climate regime.
This refers to the period from about 6000-3000 BC that spans most of
the warmest postglacial times. It is also known as the
Postglacial Climatic Optimum.
It was preceded by the Boreal period and
followed by the
See Lamb (1985), p. 372.
- Atlantic Water (AW)
- A water mass traditionally defined
as any water with salinity greater than 35.0 entering the
arctic domain from the
AW first entering the Iceland and Norwegian Seas typically
has temperatures of 6-8 C and a salinity range of
about 35.1-35.3, although the property ranges of
other waters obviously connected
with AW have prompted some to expand the definition to include
all waters warmer than 3 C and more saline than 34.9.
Estimates of the total influx of AW range as high as 9 Sv.
See Swift (1986).
- Acronym for Autonomous Temperature Line Acquisition System,
a taut-line mooring with sensors measuring surface winds, air
temperature, relative humidity, sea surface temperature, and ten
subsurface temperatures to a depth of 500 m.
Daily mean data are telemetered to shore in near real-time via
NOAA's polar orbiting satellites and Service Argos.
The standard ATLAS mooring has a design lifetime of one year, with over
500 having been deployed sine 1984.
- atmospheric tide
- Those oscillations in any atmospheric field whose periods are integral
fractions of either a lunar or a solar day. These differ from
ocean tides in several ways, one of which is that atmospheric
tides are excited not only by the tidal gravitational potential
of the sun and moon but also (and to the larger extent) by daily
variations in solar heating. Another difference is that the
atmosphere is a spherical shell and thus there are no coastal
boundaries to worry about. Finally, the response of the atmosphere
to tidal forcing is by means of internal gravity waves rather than
the barotropic surface waves of the sea.
See Lindzen (1971).
- atmospheric turbulence
- See Wyngaard (1992).
- Abbreviation for Acoustic Thermometry of Ocean Climate,
a program composed of two complementary enviromental initiatives:
(1) to gather information about temperatures in the ocean using
acoustic tomography to verify the predictions of existing climate
models; and (2) to assess the potential effects of low frequency
sound transmissions on marine mammals and sea turtles through
its MMRP component.
ATOC Web site.
- One of three geomorphologically distinct types of
coral reefs, the other two
being fringing reefs and
barrier reefs. An atoll is an
annular reef formed around a subsiding volcanic island.
See Barnes and Hughes (1988).
- Abbreviation for Along-Track Scanning Radiometer microwave sounder,
a satellite-borne instrument designed to measure land and ocean
The ATSR is a passive two-channel radiometer that scans the
near-infrared and middle-infrared bands with a spatial resolution
of 1 km x 1 km and a swath width of 500 km.
It views the Earth from an orbit of about 800 km and can measure
ocean temperature to within 0.3 C.
The ATSR can be used to detect exceptional local incidents,
large scale changes, and general trends in the Earth's climate.
ATSR Web site.
- Acronym for Acoustic Travel Time Ocean Current Monitor.
- austausch coefficient
- A German term for a quantity equivalent to the
eddy viscosity coefficient.
- Australasian Subantarctic Front
- See Subantarctic Front.
- Australian-Antarctic Basin
- One of three major basins in the
Southern Ocean. It extends
from its eastern boundary with the
at the longitude of Tasmania (at about 145 E) to the
Kerguelan Plateau (at about
75 E). The
South-East Indian Ridge separates it from the
Indian Ocean at depths greater
than 4000 m except for a gap in the Ridge at 117 E.
- Australasian Mediterranean Sea
- The region on either side of the equator between the islands
of the Indonesian archipelago. This has the most complicated
topography of any of the regional seas of the world, consisting
of a series of deep basins with limited interconnections, each
characterized by its own type of bottom water of great age.
The basins comprising this include the Banda, Sulawesi (formerly
Celebes), Molucca, Halmahera, Serman, Sulu, Flores, Java and
Sawu Seas, with the Banda being the largest and deepest.
The net transport is believed to be westward at all times, from
the Pacific to the Indian Ocean, with a maximum in August
(estimated at 12-20 Sv) and a minimum in February (estimated
at 2-5 Sv). It takes the form of a western boundary current
that is strongest along Mindanao and and Kalimantan. The
transport also occurs mainly in the upper layers with little
transport below 500 m and about 75% above 150 m. Most of
the high salinity input occurs across the sill between the
Pacific and the Sulawesi Sea, while most of the low
salinity output is through various narrow passages
between the south Indonesian islands, with both input and
output occurring over the entire water depth over the
The freshening of the throughput occurs due to both
high freshwater input from seasonal precipitation and to
strong turbulent mixing that effects water mass conversion in the
upper 1000 m of the water column, with the turbulence probably
due to locally strong tidal currents. This mixing process
imparts a unique character to the Australasian Mediterranean
in that the salinity field in the upper 1000 m is nearly
homogeneous while the temperature field is still stratified.
This occurs because even though both temperature and salinity
are strongly mixed the intense solar heating in the
region serves to maintain the temperature stratification.
See Tomczak and Godfrey (1994).
- One of three major components of deep sea sediments, the other two being
Authigenic minerals are those formed by spontaneous crystallization
within the sediment or water column, and make up only a small
fraction of the total sediment volume. The most important
of this type of sediment is the iron-manganese oxide material
formed by reduction of these metals deep in the sediment column.
The resultant material migrates upwards and is deposited
in the oxygenated upper layers of sediment. It can also be
produced as a by-product of hydrothermal activity near
See Broecker and Peng (1982).
- Autonomous Ocean Sampling Network (AOSN)
- A network which uses man small, low-cost AUVs
operating from a network of moorings to gather data in oceanographic
field programs. A pilot system is currently under development
led by the MIT Sea Grant program.
AOSN Web site.
- An autonomous underwater vehicle (AUV), i.e. a robotic vehicle designed
to carry a varying scientific payload which is changed to suit each
See Collar and McPhail (1995).
- Self-nourishing organisms with the ability to synthesize organic
molecules from CO using either photosynthesis or chemosynthesis.
- Abbreviation for autonomomous underwater vehicle, a
vehicle that can roam the ocean and collect data on its own.
They can wait for episodic, short-lived events and change
course immediately to concentrate on the most interesting areas
during an experiment.
The MIT/WHOI program built the first prototype AUV, called the
Sea Squirt, in 1988 which was used to take various measurements
in rivers, harbors, lakes and ponds.
The second prototype, called the Odyssey I, was first
launched from an oceanographic research vessel in early 1993
in the Antarctic. It was capable of operating at depths of 6000 m.
The third prototype, the Odyssey II, was designed to operate
at full ocean depths. It was designed to be mass produced and to
be configurable in a number of ways depending on mission requirements.
An on-board computer executes navigation and control programs,
and an acoustic modem is used for two-way digital communication.
The first full-scale test of the Odyssey II took place in
February 1998 in midwinter in the Labrador Sea.
The plan of the experiment was to have the AUVs gather data about
bottom water formation for three months, recharging and dumping data
at an underwater docking station at regular intervals.
A mechanical problem limited the experiment to two weeks, although
much useful data was gained for the improvement of future experiments.
- available potential energy (APE)
- A quantity first derived in Lorenz (1955) in an investigation
to discover what portion of total potential energy could be
transformed into kinetic energy under the constraint of
quasi-hydrostatic and adiabatic processes.
Available potential energy (APE) was defined as the difference
between a system's mass integrated total potential energy and
the total potential energy of a hydrostatic reference state, i.e.
the difference in potential energy between the actual physical state and
the reference state, where the latter is defined as the state of minimum
potential energy that can be reached through reversible adiabatic
processes. In the reference state, all density surfaces are level.
This was extended in Van Mieghem (1956) to deal with
See Reid et al. (1981),
Oort et al. (1989),
Kucharski (1997) and
- Abbreviation for Advanced Very High Resolution Radiometer,
a five channel scanning radiometer with channels in the
visible, visible near infrared, and infrared water vapor
window. These were selected for production of quantitative
sea surface temperature products and visible and IR
imagery depicting clouds and thermal features, e.g.
the Gulf Stream. The AVHRR produces 1 km resolution
- Abbreviation for Absolute Velocity Profiler, an instrument
developed at the APL to measure velocity
profiles in the ocean.
This dropsonde references an electromagnetically inferred velocity
profile to one measured near the sea floor.
See Sanford et al. (1985).
- Abbreviation for Atlantic Water.
- Abbreviation for airborne expendable bathythermograph, an air-deployed,
expendable, ocean temperature profiling probe. The AXBT consists of
a temperature probe, 300-1000 meters of cable, a VHF transmitter and
antenna, and a salt water activated battery.
When the AXBT hits the ocean surface and stabilizes, the transmitter
is activated and the temperature probe released. The surface transmitter
telemeters the temperatures measured by the falling probe to a data
gathering system on the aircraft that released it.
- Abbreviation for airborne expendable current profiler.
- Abbreviation for airborne expendable conductivity, temperature and
- azoic zone
- Term used to describe the part of the deep sea thought lifeless
in the mid-19th century. It was thought that the abyss was
filled with a thick layer of 4 C (since sea water was thought
to be densest at that temperature), motionless water which, combined
with the tremendous pressures and absence of sunlight, virtually
guaranteed an absence of life. The term was coined by the
naturalist Edward Forbes in the 1840s who, after dredging
for life forms in various regions, postulated eight bands or
depth zones, each characterized by a particular assemblage of
animals. These zones extended to a lower limit he set at about
300 fathoms below which the existence of life was highly unlikely.
His results (and therefore perceptions) on this issue were
skewed by an 1841 cruise in the eastern Mediterranean where he
dredged for life forms at depths up to 230 fathoms in what is now
known to be a relatively barren area. The contrast of this with
the rich hauls he made in shallower waters around England led to
his thinking the abyss devoid of life.
See Schlee (1973).
- Azores Current
- The northern branch of the subtropical gyre in the North
Atlantic Ocean. This carries around 15 Sv of water along
35-40 N to the western part of the gyre, i.e.
the Canary Current.
See Sy (1988) and
New et al. (2001).
- Azores Countercurrent (AzCC)
- A band of westward transport all across the North Atlantic at about the
latitude of the Azores.
The driving mechanism is an anomaly in the meridional change of the
wind stress curl in the eastern North Atlantic.
See Onken (1993).
- Azores Front
- See Rudnick and Luyten (1996).
- Azores High
- A center of action centered
near the Azores Islands (near 35 N and 25 W). It
extends from near the western end of the Mediterranean Sea
westward almost to Florida in the summer months, with the western
section in summer sometimes referred to as the Bermuda High.
See Angell and Korshover (1974).
- Azov, Sea of
- A large gulf or lagoon, centered at about 46 N and
37 E, connected to the
Black Sea by the narrow and
shallow (around 5 m sill depth) Kerch Strait. The Sea
of Azov covers around 38,000 sq. km which comprises
9% of the area of the Black Sea system but only
0.5% of the volume.
See Zenkevitch (1963).