- anabatic wind
A local wind which blows up a slope heat by sunshine, as opposed
to its converse the katabatic wind
- 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
A cross-connection between two channels, vessels, branches, etc.
Acronym for Across North America Tracer Experiment.
- 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
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.
A continuous record of wind speed (and sometimes direction) made
with an anemograph.
A recording anemometer
which gives a continuous record of wind
speed (and sometimes direction). These were once mechanical
devices (e.g. the Dines tube anemograph), but are now constructed
using solid-state electronic devices.
A device that measures the velocity and direction of the wind.
This usually takes the form of a series of cups attached to
a vertical axis, the rotation rate of which is measured and
calibrated to obtain the wind speed.
A self-recording aneroid barometer.
A vascular plant possessing true flowers
with seeds in ovaries.
- 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).
- 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).
Acronym for Atmospheric Nutrient Input to Coastal Areas, a
NOAA COP program
of monitoring and modeling to quantify the contribution of
atmospheric nitrate to coastal areas and to estimate the
impacts of increased nitrogen oxide emissions. The initial
focus of the program is the Chesapeake Bay, although results
will be applied elsewhere eventually.
ANICA Web site.
Descriptor for a physical property (e.g. density, etc.) that
varies depending on the direction in which it is measured.
- anomalistic month
The interval between two successive passages of the Moon in its
orbit through perigee. This is equal to
- anomalistic year
The interval between two successive passages of the Sun, in its
apparent motion, through perigee. It is equal
to 365.25964 mean solar days.
- anomalous absorption paradox
In the study of solar radiation in the atmosphere, this is a
paradox whereby measurements of the absorption of solar radiation
by clouds generally suggest that clouds absorb more solar energy
than theoretical predictions can explain for clouds composed
solely of liquid water and water vapor. One explanation offered
to resolve this is that absorbing aerosols
are responsible for the excess absorption.
See King (1993) for a summary.
In celestial mechanics, the angle between the radius vector of an orbiting
body and the major axis of the orbit as measured from perihelion in the
direction of motion.
Abbreviation for aquatic nuisance species.
- Antarctic Air
An air mass, originating over the Antarctic continent, which is cold
and dry in all seasons.
- 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. See Jacobs et al. (1970),
Tomczak and Godfrey (1994) and
and Tchernia (1980).
- Antarctic Circle
A latitude (66 S) south of which the sun does not rise
on June 21 (winter solstice)
or set on December 22 (summer solsticesummersolstice)
in the southern hemisphere.
- 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 Convergence
A region of convergence and subduction
in the Southern Ocean that circles
Antarctica at latitudes ranging from 47-62 S. It can be
identified as a relatively rapid transition is surface temperature
from 1-3 C in winter and 3-6 C in summer. It coincides
with the maximum velocity axis of the ACC
and marks the change from relatively temperature climate to polar
climate, and is also the limit of distribution of some marine species.
See Tchernia (1980).
- 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
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
In physical oceanography, a type of water mass
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. There is also evidence
for some formation via subduction of
surface waters along the Polar Front.
It 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 Convergence
to values closer to 3 C and 34.3. It can be also identified by
a salinity minimum near 800-1000 m depth, which weakens and
finally disappears as it progresses northwards.
See Piola and Georgi (1981) and Tomczak and Godfrey (1994).
- Antarctic Polar Front
See Polar Front.
- Antarctic Surface Water
In physical oceanography, a water mass in the
Antarctic Zone of the
SouthernOcean. It is characterized hydrographically 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), p. 82.
- 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).
Originating from human rather than natural sources.
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
- 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 aerosol optical depth.
Abbreviation for Australian Oceanographic Data Centre, a center
originally established in 1964 within the Royal Australian Navy
which is the official NODC for
Australia. See the
AODC Web site.
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
Atlantic Oceanographic and Meteorological Laboratory.
Abbreviation for Arctic Ocean Radiative Fluxes, a data set.
Autonomous Ocean Sampling Network.
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).
Abbreviation for alkaline phosphatase activity.
Acronym for Absorbed Photosynthetically Active Radiation.
Acronym for East Asian/North Pacific Regional Experiment, an
1. In the thermodynamics of geophysical fluid flows, an abbreviation
for available potential energy.
The difference between the total potential energy when the atmosphere
or ocean is
and that when it has been driven into
barotropic stratification by
an adiabatic redistribution of mass.
2. In bioclimatology, an abbreviation for annual potential
This quantity is calculated differently in various
bioclimatic classification schemes.
3. Acronym for Airborne Polar Experiment, and LESC program to
coordinate an airborne experiment to measure the minor
atmospheric components responsible for the greenhouse effect.
The main objectives are to study the production and loss of the
ozone in the mid-latitude and polar regions, the role of the polar
vortex and its instabilities in affecting the ozone distribution,
the effect of polar stratospheric clouds on ozone depletion, and
the role of natural aerosols in the processes of ozone depletion.
APE Web site.
An abbreviation for annual potential
ratio, a variable used in the
Holdridge scheme for
bioclimate classification. It is defined as
APE/APPT, where in
this scheme the APE is defined as
58.93 times ABT.
Acronym for Arctic Polynya Experiment.
That point of the orbit of a planet or comet which is farthest from
- aphotic zone
The region below the
euphotic zone where no light
is available for photosynthesis.
A genus of 37 species commonly called the sea hare, a name which
derives from Pliny's original designation of them as
Lepus marinus, described as such because of their
prominent rhinophores and hunched posture when resting.
Many of the species are endemic to small geographical
areas or restricted to defined ocean basins, with three species
being truly cosmopolitan. Most species are also restricted
to warm waters between 40 N and 40 S, although
the range of at least one extends to the Arctic circle.
Some 26 species occur in the Pacific Ocean, 9 in the Indian,
13 in the Atlantic, 5 each in the Mediterranean and the Red
Sea, but none around Antarctica.
All the species characteristically inhabit marine waters
shallower than 5 meters in depth and have a diet
consisting principally of seaweeds along with the occasional
angiosperm. They eat a broad range of seaweeds and prodigiously
so, and consequently exhibit fast growth rates. This genus
has been used extensively as a research model in a variety of
disciplines, especially in the study of nerve function and the
neuronal bases of learning and behavior. This is due to its
neatly ordered and comparatively simple nervous system which
contains cells large enough to be easily penetrated with
microelectrodes for neurophysiological study.
review of Carefoot (1987) for further details on their
distribution, life cycles, feeding and nutrition, growth,
energetics, locomotion, predators and defense, and parasites and
for further references concerning research uses.
That point of the orbit of a satellite, natural or artificial, which
is farthest from the Earth.
- apparent polar wander
The motion of the paleomagnetic pole relative to a continent or
plate. Until recently, this was hypothesized to be due solely
to plate motion relative to the
mesosphere, the relatively stronger
and slowly deforming mantle beneath the
asthenosphere, but now it is
generally regarded that
polar wandering affects
true polar wander paths.
See Gordon (1987).
- apparent solar day
The interval between two successive transits of the true Sun over
the meridian. This is not constant due to the Earth's elliptical
orbit around the Sun.
- apparent solar time
Time as measured by the apparent position of the Sun in the sky, i.e.
time as would be measured by a sundial.
Abbreviation for average total annual precipitation,
a variable used in the
Holdridge scheme for classification
of bioclimates. It is defined as the annual mean of monthly
precipitation amounts (in mm).
- apse line
The diameter of an elliptical orbit which pases through both foci
and joins the points of greatest and least distance of the revolving
body from the center of attraction.
The fifth of six ages in the
Early Cretaceous epoch, lasting
from 119 to 113 Ma. It is preceded by
the Barremian age and followed by
the Albian age.
A subterranean body of unconsolidated material such as sand, gravel,
and soil that is saturated with water and sufficiently permeable
to produce water in useful quantities.
The first of six ages in the
Mioocene epoch (the first of two in the
Early Miocene), lasting from 23.7 to 21.8 Ma. It is preceded by
the Chattian age of the
Oligocene epoch and followed by
the Burdigalian age.
- 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.
Arabian Sea Study Web site.
- 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).
atmospheric radiative cooling.
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.
ARCANE Web site.
The first of two eons in the
Precambrian period, lasting from as
far back as you want to go to 2500 Ma. It is preceded by a
great bloody void and followed by the
Proterozoic eon, and comprised of
the Early (whenever-3400 Ma), Middle (3400-3000 Ma),
and Late (3000-2500 Ma) eras.
- archibenthic zone
The ecologic zone in which the ocean bottom-dwellers can be
found. This is from
See Fairbridge (1966).
Collective term for bottom-dwelling ocean life coined by
See Fairbridge (1966).
- archipelagic apron
The broad cone or fan-like slopes that abut single or
multiple volcanic seamounts. They are usually smooth
but can be hilly or mountainous, and are most common in
the central and south Pacific Ocean. A typical development
sequence has a volcano developing on the sea floor,
depressing the local crust, and lava and sediment filling
in the depression to form the archipelagic apron.
See Fairbridge (1966).
- Architeuthis princeps
A marine invertebrate in the phylum
This is the notorious giant squid or kraken of myth and
See Ellis (1994).
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.
- 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 Circle
- 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 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.
See Coachman and Aagaard (1974).
- Arctic Ocean Deep Water
See Swift (1986).
- 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).
Acronym for Arctic Research Consortium of the United States, an
organization formed in 1988 to identify and bring together the
distributed human and facilities resources of the Arctic
research community. It is a non-profit corporation consisting
of institutions organized and operated for education, professional,
or scientific purposes. The headquarters and staff are located
in Fairbanks, Alaska.
ARCUS Web site.
Acronym for the Atmospheric Research and Environment Programme of
the WCRP, which coordinates and fosters
research on the structure and the chemical composition of the atmosphere
and its related physical characteristics; the physics of weather
processes and weather forecasting. The four major components of
AREP are the Global Atmospheric Watch (GAW),
Weather Prediction Research, Tropical Meteorology Research, and
Physics and Chemistry of Clouds and Weather Modification
Research. See the
AREP Web site.
- 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).
- argon-argon dating
A radioisotopic dating method
that entails measuring the ratio of two argon isotopes,
argon-39 and argon-40.
for which this method was developed as an alternative,
measurements of both isotopes
are simultaneously made at the same location in the
crystal lattice where the argon is trapped.
The potassium-40 is indirectly measured by irradiating the sample
with neutrons in a nuclear reactor, causing the stable potassium-39
to transmute into argon-39. The sample age is calculated by
measuring both the argon-40 and argon-39 and knowing the
(constant) ratio of potassium-40 to potassium-39.
See Bradley (1985).
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 the Atmospheric Research and Information Centre
located at the Manchester Metropolitan University,
a multidisciplinary center for the study and resolution of
atmospheric pollution issues. See the
ARIC Web site.
Acronym for Applications and Research Involving Space Techniques
for the Observation of the Earth's fields from Low-Earth-orbit
- Arizona monsoon
A meteorological phenomenon that occurs during the summer throughout
the southwest portion of North America. During the monsoon the
prevailing winds shift from the winter pattern from the west and
northwest to from the south and southeast. This causes moisture
to be imported from the Pacific Ocean and Gulf of Mexico and
dramatic changes in rainfall patterns.
The summer wind shift is due to a combination of the northward
movement of the Bermuda High and
the intense heating over the desert creating rising air (i.e.
a low pressure region) which is replaced my moisture-rich air
from the south.
Arizona monsoon Web site.
Air Resources Laboratory.
- 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 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).
See Ilahude and Gordon (1996).
Acronym for Atmospheric Radiation Measurement Program, a major
program of atmospheric measurement and modeling intended to improve
the understanding of processes and properties that affect
atmospheric radiation, with a particular focus on the influence of
clouds and the role of cloud radiative feedback.
See Stokes and Schwartz (1994) and the
ARM Web site.
Abbreviation for autoregressive moving average, a method for
constructing simple dynamical models from data.
Acronym for the Amazon Region Micrometeorological Experiment.
See Shuttleworth (1988).
Acronym for Advanced Research Project Agency, a part of the
DOE formerly called DARPA.
Abbreviation for Analysis of Rapid and Recent Climate Change.
- 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 airborne radiation thermometer.
Acronym for Africa Real Time Environmental Monitoring Using Imaging
Satellites, an operational environmental monitoring program that
provides real and near-real time precipitation and vegetation
assessment for African, the Near East and southwest Asia based on
the integrated use of high frequency
NOAA AVHRR data. See the
ARTEMIS Web site.
Acronym for a Self-contained Atmospheric chemistry coDe, a package
developed for integrating chemical schemes into atmospheric
GCMs. It was developed by the ACMSU
group of the UGAMP project. See the
ASAD Web site.
Acronym for Advanced Synthetic Aperture Radar (SAR).
- ascending node
The point on Earth at which a satellite crosses the equatorial plane
traveling from south to north.
Acronym for Atmospheric Studies in Complex Terrain, a
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).
Abbreviation for Atmospheric Stabilization Framework.
Acronym for Aquatic Sciences and Fisheries Abstracts, an abstracting and
indexing service covering the world's literature on the science, technology,
management, and conservation of marine, brackish water, and freshwater
resources and environments, including their socio-economic and
legal aspects. This database, produced by ASFIS,
contains over 600,000 references with coverage since 1971 with over
3000 new references added each month. ASFA informtion products and
services are available in printed and computer-readable formats.
ASFA Web site.
Acronym for Aquatic Sciences and Fisheries Information System, a
cooperative international system coordinated and created by
the Food and Agricultural Organization (FAO) of the United Nations.
The system is co-sponsored by the IOC and
the Division for Ocean Affairs and the Law of the Sea, Office of Legal
Affairs of the United Nations (UN-DOALOS/OLA), and
ASFIS creates information products and services that serve those
engaged in aquatic sciences, technology, policy, living and non-living
resources, pollution and environmental quality, and aquaculture. The
most prominent product is ASFAS.
Acronym for Air-Sea Gas and Marine Aerosol and Gas Exchange
Abbreviation for Association of Sea Grant Program Institutes.
Acronym for Axial Seamount Hydrothermal Emissions Study.
Acronym for Antarctic Southern Hemisphere Ozone Experiment,
a program designed to examine the causes of ozone loss in the
Southern Hemisphere lower stratosphere and to investigate
how the loss is related to polar, mid-latitude and tropical
processes. This experiment was conducted in concert with
MAESA in four phases through the
Antarctic winter of 1994.
ASHOE Web site.
Abbreviation for atmospheric surface layer.
Acronym for the American Society of Limnology and Oceanography.
Their goals are to promote the interests of limnology, oceanography
and related sciences, to foster the exchange of information across
the range of aquatic science, adn to facilitate investigations dealing
with these subjects. More information can be found at the
ASLO Web site.
Acronym for Aspendale ISCCP Regional Experiment.
An aggregation of species that live together at some locality
but do not relate to each other ecologically. Contrast with
- assemblage biozone
a type of biozone in which the recognition of
different taxa with varying vertical ranges forms
the basis for the definition, and in this case the name of the biozone
itself is generally based on one of the more common members.
See Briggs and Crowther (1990), pp. 466-467.
Abbreviation for Aerosol Scattering Spectrometer Probe.
Acronym for Advanced Spaceborne Thermal Emission and Reflection
Radiometer, an imaging instrument that will fly on the satellite
EOS AM-1. ASTER consists of three separate subsystems that
operate in different spectral regions, with each system having
its own telescope. The subsystems are the Visible and Near
Infrared subsystem (VNIR), the Shortwave Infrared (SWIR)
subsystem, and the Thermal Infrared (TIR) subsystem.
The information gained from ASTER will be used in studies
of the surface energy balance, plant evaporation and
evapotranspiration, vegetation and soil characteristics,
the hydrologic cycle, and volcanic processes.
ASTER is a cooperative effort between NASA and Japan's
Ministry of International Trade and Industry, with the
collaboration of many scientific and industrial organizations
in both countries.
ASTER Web site.
A marine animal of the class
A class of marine invertebrates in the phylum
The are commonly known as sea stars, most of the around
1100 species of which live near the shore although some
dwell at great depths.
Introduction to the Asteroidea
U.C. Museum of Paleontology.
Acronym for the Atlantic Stratocumulus Transition Experiment,
conducted in June 1992 off North Africa in the area of the
Azores and Madeira Islands. It was based in an area where the
total cloud cover (mostly stratocumulus) ranges from
50 to 60%, dominated by low-level clouds with moderate
optical thicknesses. The region is characterized by broken
low cloudiness and strong gradients of low-level cloud
amount, with satellite studies showoing conditions ranging
from solid stratocumulus decks decks to broken trade
cumulus. It is also not directly influenced by continental
effects, which enabled ASTEX to address issues related to
the stratocumulus to trade-cumulus transition and cloud-mode
The ASTEX measurement program was designed to study how the
transition and mode selection are affected by cloud-top
entrainment instability, diurnal coupling and clearing due to
solar absorption, patchy drizzle and a transition to horizontally
inhomogeneous clouds through decoupling, mesoscale variability
in cloud thickness and associated mesoscale circulations, and
episodic strong subsidence lowering the inversion below the
lifting condensation level. The overall design was to provide
improved dynamical, radiative and microphysical models and an
improved understanding of the impact of aerosols, cloud
microphysics, and chemistry on large-scale cloud properties.
See Albrecht et al. (1995) and the
ASTEX Web site.
The layer of the Earth
below the lithosphere,
characterized by lower strength, lesser
rigidity and greater density than the overlying layer. These qualities
lead to the process of
taking place here as well as the generation of magma and the
attenuation of seismic waves. It is approximately 200 km thick.
See Arctic Surface Water.
Acronym for the Atlantic Trade-wind Experiment.
See Albrecht (1981).
- 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 Ocean
Much more later.
- Atlantic Oceanographic and Meteorological Laboratory (AOML)
A part of the NOAA
ERL network that conducts
basic and applied research programs in fisheries recruitment,
coastal nutrient studies, ocean plume studies, hurricane
research, tropical climate studies, rainfall studies, atmospheric
chemistry, climate change, and ocean acoustic remote sensing.
See the AOML Web site.
- 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 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 mooring system.
Abbreviation for Atmospheric Lidar.
Abbreviation for Atmospheric Transport Model.
Acronym for Atmospheric Transport Model Evaluation Study, performed
by CEC, WMO and IAEA using Chernobyl data.
The Atmospheric Trace Molecule Spectroscopy experiment is
an infrared spectrometer (a Fourier transform interferometer)
designed to study the chemical composition of the atmosphere.
This instrument is carried and used on the Space Shuttle.
Measurements are made at the times in each orbit during which
the atmosphere is between the Sun and the ATMOS instrument.
Rapid successive measurements are taken to distinguish changes in
the composition of specific molecules with altitude. This
is accomplished by analyzing the absorptions due to each molecule
in each successive spectrum.
ATMOS Web site.
- atmospheric boundary layer (ABL)
One of two types of
planetary boundary layer.
See Garratt (1994).
- atmospheric electrical circuit
A proposed method for measuring global temperatures that uses
the relationship between global thunderstorm activity and the mean
global temperature. Thunderstorms lead to an electrification
of the fair-weather atmosphere, and it is known that thunderstorm
activity is nonlinearly related to temperature. It has been
suggested that a 1% increase in global temperature may lead to
a 20% increase in the ionospheric potential.
Such measurements may be complicated by changes in atmospheric
composition and by changes in atmospheric dynamics, e.g. El Nino
and ancillary phenomena. See
Karl et al. (1995).
- atmospheric radiative cooling
The combination of the net radiative energy flux at the
top-of-the-atmosphere (TOA) with the net radiative energy
flux at the Earth's surface. This is the net effect of
infrared emission by the atmosphere, the absorption by
the atmosphere of infrared emitted by the Earth's surface,
and the absorption by the atmosphere of solar radiation.
To a first approximation, the ARC is balanced by latent
heat release, which suggests that the globally averaged
precipitation rate is determined by radiative processes.
See Wielicki et al. (1995).
- 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).
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.
- atmospheric stabilization
A term used to describe the limiting of the concentration of the
greenhouse gases at a certain level.
Acronym for Acoustic Thermometry of Ocean Climate.
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.
- attribution problem
The problem of establishing a causal link between changing
greenhouse gas emissions and
changes in climate, i.e. of establishing that changes in
anthropogenic emissions are required to explain satisfactorily
a detected change in climate.
There is a nonzero chance that a change thus detected could indeed
be due to non-anthropogenic causes, and the only way to decrease
this possibility is via a systematic numerical investigation of
the system's response to various combinations of possible
climate forcing changes. Unique attribution of a detected
climate change to anthropogenic causes would require the explicit
specification of the climate change signals of all possible
competing mechanisms (individually and in combination), and
statistical determination that none of these mechanisms could
satisfactorily explain the detected change.
Abbreviation for Alaskan Tsunami Warning Center.
- austausch coefficient
A German term for a quantity equivalent to the
eddy viscosity coefficient.
- 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).
In cloud microphysics, the rate at which cloud water content
decreases as particles grown to precipitation size by coalescence
and/or vapor diffusion. See Houze (1993).
The mathematical process of calculating the correlation coefficient
between a time series and the same series with a lag of a number of
sampling intervals. The variation of this correlation coefficient
as a function of the lag provides information on the existence
of periodic fluctuations in the series.
The ecology of an individual
- 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.
Descriptive of a phytoplankton species
that is able to satisfy its dietary requirements from purely
- autotrophic respiration
The form of respiration by which CO2 is released by the metabolic
processes of plants.
A term used in respect to climate change to denote the capacity
of the global climate to fluctuate of its own accord without the
need for extraterrestrial (e.g. solar variations, orbital
variations, etc.) influences.
- autumnal equinox
Abbreviation for autnomomous underwater vehicle.
Descriptive of a phytoplankton
species unable to grow without a supply of a specific organic
compounds, e.g. vitamin B12, which they are unable to produce
- available potential energy
The part of the total potential energy of the atmosphere available
for conversion into kinetic energy by adiabatic
redistribution of its mass so that the density stratification
becomes everywhere horizontal.
A class of the subphylum Vertebrata of
the phylum Chordata that contains
those birds dependent upon the sea for food, examples of which
include the albatross, the petrel, cormorants and auks.
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
Acronym for Airborne Visible Infrared Imaging Spectrometer,
an instrument that flies aboard a NASA ER-2 airplane (a U2 modified
for increased performance). It is an optical sensor that delivers
iamges of the upwelling spectral radiance
in 224 contiguous spectral channels in wavelengths ranging from
the infrared (400 nm) to the ultraviolet (2500 nm).
It flies at about 20 km at about 730 km/hr. The main scientific
objective of the instrument is to identify, measure, and monitor
constituents of the Earth's surface and atmosphere based on
molecular absorption and particle scattering signatures.
AVIRIS Web site.
Acronym for Advanced Visible and Near-Infrared Radiation, a
visible and near-infrared radiometer designed to measure land
and coastal zones with high spatial resolution. It measures
solar light reflected by the Earth's surface in order to monitor
such environmental phenomena as vegetation and desertification.
It has a spatial resolution ranging from 8 to 16 m and a swatch
width of about 80 km and will fly on the
Abbreviation for Absolute Velocity Profiler, an instrument
developed at the APL.
Abbreviation for Atlantic Water.
Acronym for Automated Weather Acquisition and Retrieval Data
Alfred Wegener Institute.
Acronym for Advanced Weather Interactive Processing System.
Abbreviation for airborne expendable bathythermograph.
Abbreviation for airborne expendable current profiler.
The horizontal angle between the observer's meridian and the line
joining observer and object. This is conventionally measured from
north through east in astronomical computations and from south through
west in triangulation and precise traverse work.
- 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 he 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.
- 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.