- Said of the anti-clockwise change of direction of a wind,
as opposed to veering.
- backscattering cross-section
- The ratio of the acoustic power scattered at an angle of
180 from the incident acoustic wave to the acoustic
intensity incident on a unit volume or area. This measure,
typically referenced to a unit distance, e.g. 1 m, is the
ratio of the reflected acoustic power to incident acoustic
power per unit area. The units of this ratio are
area, e.g. m.
- That part or zone of a beach profile that extends landward from
the sloping foreshore to a point
of either vegetation development or a change of physiography,
e.g. a sea cliff or a dune field.
See Komar (1976).
- Baffin Bay
- A large sea located between the Canadian Archipelago and
the Labrador Sea.
It is about 1000 km and 400 km.
Most of Baffin Bay is deeper than 1500 m, but deep water exchange with
the Labrador Sea is restricted by a sill in Davis Strait with a
depth of 670 m.
A mobile ice cover forms during winter and moves southward under the
Icebergs calved from glaicers in southern and western Greenland drift
across the bay and southward in the
Baffin Current to southern latitudes.
A significant oceanographic feature of Baffin Bay is the
North Water, a partially open water area
in the northern part where complete ice cover would be expected under
prevailing climatological conditions.
The principal currents are a relatively warm northwards flowing current
along the Greenland coast, and the cold southwards flowing
This cyclonic circulation is driven by surface inflows of low salinity
Arctic water through the Canadian Archipelago in the north and by means
of the West Greenland Current
in the south.
Current meter data from northern Baffin Bay show strong surface Arctic
outflows to a depth of about 500 m, directed to the south and generally
following the bathymetry.
There is a strong annual cycle in the mean currents, with the currents
stronger in summer and weaker in winter.
This variability is probably driven by seasonal changes in buoyancy
forcing, which enhances the coastal currents on the wide shelves.
Tidal currents up to 0.4 m s have been observed on the shelves and
along the shelf slopes, and consist mainly of semidiurnal components, with
a considerable diurnal component in some areas.
The surface layer, defined as the layer extending to the maximum depth
influenced by wind stress, is a few tens of meters thick.
The surface layer water has a density of 1026 kg/m or less, with
the deeper water weighing in at 1027 kg/m.
Their salinities are 32.5 and 34.0, respectively.
In the eastern part of the bay there is a layer between about 200 and
800 m characterized by relatively warm and saline water. This is
considered the result of inflow of Atlantic water through the Davis
Strait. Substantial tidal currents have been measured in the eastern
part of the bay, e.g. up to about 20 cm/s at locations where the water
depth is 500 m.
See Ingram and Prinsenberg (1998).
- The local name given to tropical
cyclones in the Phillipines, especially those
occurring from July to November.
- balance equations
- See G. and Flierl (1981), p. 508.
- Balearic Sea
- One of the seas that comprise the western basin of the
Mediterranean Sea which
is sometimes called the Catalan Sea.
It lies between the Iberian coast and the Balearic Islands
(Ibiza, Mallorca, Menorca) in the northwestern Mediterranean.
It is separated from the
Tyrrhenian Sea to the
east by Sardinia and Corsica and abuts the
Alboran Sea to the west.
The bathymetry is dominated by the Balearic Abyssal
Plain, which covers over 30,000 square miles, covering
the majority of the basin floor at depths ranging from
2700-2800 m. This is bordered to the northwest by
the Rhone Fan, a large sedimentary cone.
The circulation can be seen to first order to be a single
oblong cyclonic cell with a divergence zone aligned with
the shape of the basin. More detailed studies
have shown the surface circulation to be strong year-round
and characterizied by two permanent density fronts. These
are the Catalan Front on the continental shelf slope and
the Balearic Front on the Balearic Islands shelf slope, with
the former the more active.
The northern area a plume of cold water frequently seen moving
southward along the continental slope and shedding dipole
eddies along its leading edge. Energetic filaments continuously
spawned by the Catalan Front seem to be associated with this
See Fairbridge (1966),
La Violette (1990) and
Pinot and Ganachaud (1999).
- Bali Sea
- A regional sea which is part of the
Australasian Mediterranean Sea in the southwest Pacific Ocean.
It is classified as a distinct sea for navigational purposes
but is usually grouped with the Flores Sea for
It is centered at around 116 E and 8.5 S
and is bordered by Bali and Sumbawa to the south and
Madura to the west, and abuts
the Java Sea to the north and
the Flores Sea to the east.
The Bali Sea covers an area of
about 45,000 km and has a greatest depth of 1590 m.
It is mostly underlain by a small trough extending to the
west of the Flores Trough and is bound by sills to the
south (the 200 m Bali Strait and the 220 m Lombok Strait)
and by a narrow, 600 m deep passage connecting it to the
Makassar Stait to the north.
The circulation and water mass properties are continuous
with the contiguous Flores and Java Seas to the east and
north, repectively. Most of the oceanographic interest
in the Bali Sea is concerned with its role in the Indonesian
throughflow of Pacific Ocean waters into the Indian Ocean,
with most if not all of this flow passing through the
aforementioned Bali and Lombok Straits.
See Fairbridge (1966).
- Acronym for the Baltic Sea Experiment, a GEWEX
project to study coupled hydrological processes between complicated
terrain, sea and ice and the atmospheric circulation to determine the
energy and water budgets of the Baltic Sea and related river basins.
The scientific objectives are:
- to explore and model the various mechanisms determining the space
and time variability of energy and water budgets of the BALTEX area and its
interactions with surrounding regions;
- to relate these mechanisms to the large-scale circulation systems in
the atmosphere and oceans; and
- to develop transportable methodologies to contribute to research in
- Baltic Current
- See Kattegat.
- Baltic Operational Oceanographic System (BOOS)
- A cooperative endeavor among national government
agencies in the countries surrounding the
Baltic Sea responsible for the collection
of observations, model operations and production of forecasts, services
and information for the marine industry, and public and other end
BOOS is a regional Task Team under
BOOS will be implemented from 1999-2003 by the accomplishment of
- optimizing the existing operational observing network;
- use of remote sensted radar and satellite data;
- an operational mesoscale analysis system called PRODAS;
- optimization of existing models and coupled models;
- ecological modeling;
- study of harmful algae blooms via HABWARN;
- development of an anthropogenic load model;
- an assessment of the current state of the Baltic environment; and
- development of Info-BOOS.
- Baltic Sea
- A dilution basin type of
mediterranean sea that is connected
to and experiences limited, intermittent water exchange with the
North Sea. It comprises several parts
separately known as the
Gulf of Bothnia,
the Aland Sea,
the Gulf of Finland,
the Gulf of Riga,
It has a mean depth is about 57 m, an area of about 370,000 km,
and a volume of about 20,000 km, and is one of the largest brackish
water bodies in the world.
About 17% of its area is shallower than 10 m.
The Baltic Sea depression is essentially a long fjord in the north-south
direction (1500 km) with an average width of 230 km.
The topography divides it into a series of relatively deep basins,
with maximum depths ranging from 105-459 m.
The Baltic has a positive freshwater balance with an annual river
runoff of 440-480 km, or about 2.2% of the volume.
The runoff is usually maximum in May and minimum in January or February.
A permanent salinity stratification results in a transition layer at
65-75 m. The residence time is on the order of several decades.
The difference between precipitation (640 mm) and evaporation (500 mm)
adds another 60 km per year.
The circulation in the Baltic Sea is mainly driven by three forces:
On average, sea level rises about 25 cm from the Danish Straits towards
the Gulf of Bothnia due to the river
- wind stress;
- horizontal density differences due to freshwater inflow from
rivers and saline water inflow via the Danish Straits; and
- sea level inclination from the Danish Straits towards the
If not interrupted by wind-driven currents, a continuous inflow
of saline water from the Skagerrak forms the
deep water of the Baltic. It is estimated that 740 km of saline water
enters the Baltic per year.
The inflow enters through the Great Belt (65%), the Sound (25%) and
the Little Belt (10%). After passing through these, the saline water
passes over the shallow Darss Sill (18 m), crosses the Arkona basin,
flows through Bornholm Strait into the Bornholm Basin, and finally flows
through Stolpe Channel into the Gotland Basin.
The value of increases from less than 5.0 in the Gulf of Finland
to more than 25.0 in the Skagerrak.
See Segerstrale (1957),
Rodhe (1998) and
- A paleogeographic area during the late Precambrian
and early Paleozoic that comprised north-western
Europe, including most of what are now the U.K., Scandinavia, European
Russian and Central Europe. It formed the southeastern margin of
the Iapetus Ocean and was moved by the
subduction of that ocean (during the
event) such that it made contact with North America and Greenland during
and Early Devonian.
- Banda Intermediate Water (BIW)
- See Rochford (1966).
- Banda Sea
- A regional sea in the
covering approximately 470,000 square kilometers and centered at
about 126 E and 5 S. It consists of several
basins and troughs interconnected by sills whose depths are
mostly greater than 3000 m.
See Gordon et al. (1994) and
- A unit of pressure equal to the pressure of 29.530
in. or 750.062 mm of mercury under the standard conditions of
0 C temperature and 9.80665 m/s gravitational
acceleration. Also, a popular locale during lengthty
- The local name given to strong, northwesterly squalls on the
north coast of the island of Celebes that occur most frequently
from December to February.
- Barents Sea
- One of the seas found on the Siberian shelf in the
Arctic Mediterranean Sea.
It is located between the White Sea
to the west and the Kara Sea to
the east and adjoins the
Arctic Ocean proper to the
The Barents Sea is a key region for the modification of water
masses in the Arctic, being one of several marginal seas in
the Arctic wherein water flowing over shallow regions is transformed
when heat loss and brine injection during the formation of sea ice
increase density in the winter and sea ice meltwater and river
runoff decrease surface water density in the summer.
It differs from the other marginal seas in the region in that
it has close connections with both the
Norwegian Sea and the
See Zenkevitch (1963),
Pfirman et al. (1994),
Pfirman et al. (1995) and
Harris et al. (1998).
- Descriptive of an an atmosphere or ocean in which surfaces of
pressure and density intersect at some level or levels. The
state of the real atmosphere and ocean, as opposed to
barotropic. In a baroclinically
stratified fluid total potential energy can be converted
to kinetic energy.
- baroclinic flow
- In oceanography, the vertically varying circulation associated with horizontal
imhomogeneities in the stratification of the oceans.
- baroclinic instability
- To be completed.
- baroclinicity vector
- A quantity that can be derived from the vorticity equation and
where is the density and the pressure.
This indicates a tendency to generate vorticity whenever density surfaces
are inclined to pressure surfaces.
See Gill (1982).
- baroclinic radius of deformation
- See Rossby radius of deformation.
- Descriptive of a hypothetical atmosphere or ocean in which
surfaces of pressure (isobaric surfaces)
and density (isentropic surfaces) coincide at all levels, as
compared to baroclinic. In a state
of barotropic stratification, no potential energy is
available for conversion to kinetic energy.
- barotropic flow
- In oceanography, depth-independent circulation due to changes in surface
elevation. More later.
- barotropic instability
- To be completed.
- barotropic radius of deformation
- See Rossby radius of deformation.
- barrier reef
- One of three geomorophologically distinct types of
coral reefs, the other two being
fringing reefs and
atolls. Barrier reefs are separated
from land by a lagoon usually formed by coastal subsidence.
See Barnes and Hughes (1988).
- barrier layer
- In physical oceanography, the layer between the
thermocline and the
It is called this because of its
effect on the mixed layer heat budget
due to the temperature
at the bottom of the barrier layer being zero, which excludes
heat loss to the underlying water via mixing.
It is defined as the difference between the thickness of the isothermal
layer and the mixed layer (determined by a defined change in density),
with the isothermal layer generally being greater than or equal to
the mixed layer depth.
In the Western
Pacific, an area with a barrier layer, horizontal temperature
gradients are also very small,
leading to the conclusion that the net heat flux at the ocean
surface must be close to zero.
See Tomczak and Godfrey (1994).
- Abbreviation for Baltic Sea Fluorescence Experiment, conducted
between March 1 and 10, 1994 aboard the RV A.V. Humboldt as
a collaborative project between the IRSA
in Italy and the Institute for Baltic Sea Research-IOW in
Germany. Water was collected along several transects and at
anchor stations over the diel cycle
from four or five depths using a rosette. A pulse amplitude
modulated (PAM) fluorometer was used on sample concentrated
by gentle filtration to measure phytoplankton photosynthesis.
- Acronym for Barents Sea Impact Study, a research project developed under
the auspices of IASC for studying the impacts of
global change in the Barents region, which includes the
Barents Sea and the northernmost parts
of Sweden, Finland, Norway and European Russia. The main emphasis
is on the Barents Sea and fisheries, and on terrestrial ecosystems,
forestry and reindeer herding.
- Acronym for Baltic Air-Sea-Ice Study, a field experiment of
The objective of BASIS is to create and analyze an experimental data set
for optimization and verification of coupled
The specific objectives are:
- investigation of water budget, momentum and thermal interaction at
air-ice, air-sea and sea-ice boundaries;
- investigation of the atmospheric boundary layer (ABL);
- investigation of the ocean boundary layer (OBL); and
- validation of coupled atmosphere-ice-ocean models.
The intensive field phase of BASIS took place in the Gulf of Bothnia
in the Baltic Sea in a boundary zone between the open sea and the
ice-covered sea from February 16 to March 7, 1998.
Ships used included the Swedish RV Argos and the
Finnish RV Aranda.
- Acronym for Basic Air Sea Studies, a series of experiments carried out
in Bass Strait, Australia during the period 1975-1985.
The data sets gathered results in a clearer understanding of the
relationships between wave state, wind stress, and surface layer
See Chambers and Antonia (1981).
- Acronym for Baltic Sea System Studies, a project of the
MAST and INCO program of the EU.
The objectives of BASYS are to further the understanding
of the susceptibility of the Baltic Sea to external forcing
and to improve the quantification of past and
- Batchelor scale
- A length scale at which the steepening of scalar concentration
gradients by the rate-of-strain is balanced by diffusive
It is defined as:
where is the kinematic viscosity of seawater,
is the molecular diffusivity, and
is the rate at which turbulent kinetic energy
is lost, i.e.
the rate of strain tensor (with units of
See McDougall et al. (1987).
- bathyal zone
- The marine ecologic zone that lies deeper than the continental
shelf but shallower than the deep ocean floor, i.e. those
depths corresponding to the locations of the continental
slope and rise. The depth
range is from 100-300 m down to 1000-4000 m depending on
such variables as the depth of the shelf break, the depth
of light penetration, and local physical oceanographic
See Fairbridge (1966).
- The measurement and charting of the spatial variation of
the ocean depths.
See Fairbridge (1966).
- bathypelagic zone
- One of five vertical ecological zones into which the
deep sea is sometimes divided.
This is the zone starting from 100 to 700 m deep (coinciding
with the upper limit of the
psychrosphere) at the
10 C isotherm. The number of species and populations
decreases greatly as one proceeds into the bathypelagic
zone where there is no
light source other than bioluminescence, temperature is uniformly
low, and pressures are great.
This overlies the
abyssopelagic zone and is overlain
See Bruun (1957).
This is the lowest of the
three vertical sections of the pelagic
part of the ocean, the other two being the upper
euphotic and the middle
- A device developed by Athelstan Spilhaus in 1938 to measure temperature/depth
profiles in the ocean, the bathythermograph was basically
a reworking of a mostly unworkable device called an oceanograph
built in 1934 by Carl-Gustav Rossby for the same purpose.
It consisted of an open, rectangular frame in which a compressible
bellows with a pen arm and stylus was mounted at one end.
The stylus rested on a smoked glass slide and moved across it to
scratch a record of ocean temperatures. The stylus also moved
vertically with changes in depth and thus created a temperature/depth
The bathythermograph (or BT) was further improved by Maurice Ewing
and Allyn Vine in 1940. Their version responded more quickly to
temperature changes and was streamlined so it could be lowered
and raised more quickly from a moving ship than could
the previous more unwieldy version.
In 1940 WHOI started doing military research for the government,
a large part of which was concerned with sonar and the use of
BTs with it. Knowledge of the vertical temperature structure of
the ocean was extremely helpful to sonar operators since sound
speed in sea water is a strong function of temperature, and various
types of vertical temperature profiles would lead to sound traveling
differently in the ocean. BT data was also useful for adjusting
the buoyancy or trim of submarines since it could help provide
an estimate of how much ballast would be needed to move a submarine
from periscope depth to greater depths. A strong thermocline would
require much more ballast for the submarine to descend.
The military research also led to further improvements in the
BT including better aerodynamics for more stable operation at
higher speeds as well as moving the glass slide and stylus
from within the BT to inside the submarine. By early 1943 many
submarines were outfitted with and used BTs. In an extremely
helpful quid pro quo, the glass slides were given to WHOI and
Scripps after missions in both oceans, allowing charts of the
vertical temperature structure of the ocean to be constructed.
Over 60,000 slides from the North Atlantic alone were thus made available
See Spilhaus (1938) and Schlee (1973).
- Acronym for Bermuda Atlantic Time-series Study,
project to obtain and study long-term time-series of biogeochemical
cycles in the Sargasso Sea near Bermuda.
See Michaels and Knap (1996) and
Steinberg et al. (2001).
More information can be found at the
BATS Web site.
- Acronym for the Baltic Sea Vertical Mixing and Advection Experiment, a
BALTEX program to investigate
vertical mixing and advection in the major basins
of the Baltic Sea.
- Bay of Bengal
- The northeastern arm of the Indian Ocean,
located between peninsular India and Burma. It covers about
2,200,000 sq. km and is bordered on the north by the Ganges
and Brahmaputra River deltas, on the east by the Burmese
peninsula and the Andaman and Nicobar Islands, on the west by
India proper and Ceylon, and on the south by the Indian Ocean
proper. The average depth is around 3000 m with maximum
depths reaching over 400 m in the southern parts.
Major circulation features are the
East Indian Current, a
northward current flowing along the Indian shelf from
January through October, and the
East Indian Winter Jet,
a southwestward flowing current that replaces during the
remainder of the year. This current reversal is due to the
seasonal change from the Northeast to the Southwest Monsoon
and the concomitant wind forcing. General clockwise and
conterclockwise circulation gyres are seen throughout the
Bay accompanying, respectively, the Current and the Winter
Jet, although the situation becomes a bit more complicated
during the transition periods.
The monsoonal wind variations and the resulting circulations
also serve to induce upwelling near the coasts during the
spring (with the northward current) and the piling up of
surface water along the coasts during the late fall and early
winter (with the southward currents). Thus the isopycnals
tilt upwards and downwards towards the shore during, respectively,
the spring and late fall. The annual mean SST for the region
is above 28.5 C., although upwelling can reduce this
to 25-27 C during the spring. The salinities are
kept lower than normal oceanic values (especially in the
western parts) by extensive monsoonal river runoff.
See Tomczak and Godfrey (1994),
Fairbridge (1966) and
Shetye et al. (1996).
- Bay of Bengal Water
- A water mass that originates
in the northern Bay of Bengal
via monsoonal input from the Ganges and Brahmaputra Rivers.
It is a low salinity water mass that spreads across the
Bay in an approximately 100 m thick layer that produces
a strong halocline beneath (above
Indian Central Water) and
keeps the surface salinity in the eastern parts of the Bay
below 33.0 throughout the year. Although there are no
variations in temperature through the BBW layer, there are
salinity variations below 50 m (and therefore above the
main halocline) due to the fact that weak wind mixing
erases variations over only about half the depth of the layer.
This causes the permanent existence of a barrier
The low salinity surface water to the west of India, sometimes
called East Arabian Sea Water (EAW), is usually subsumed under
the BBW rubric due to its nearly identical properties.
See Tomczak and Godfrey (1994).
- Bay of Biscay
- See Fairbridge (1966), pp. 637.
- Bay of Bothnia
- See Gulf of Bothnia.
- In oceanography, abbreviation for
benthic (or bottom) boundary layer.
- Abbreviation for
Bermuda Bio-Optics Project.
- The Brazil Basin Tracer Release Experiment was a WHOI
program in 1996 and 1997 who goal was to use two independent methods to
quantify turbulent mixing in the eastern Brazil Basin.
The methods employed were:
The experiment involved released approximately 110 kg of sulfur
hexafluoride on an isopycnal near 4000 m
depth near 21 40' S, 18 25' W.
The location is over a system of ridge spurs and canyons that run zonally
towards the crest of the Mid Atlantic Ridge. The spurs attain depths
of nearly 4400 m in the vicinity of the tracer release and the
canyon valleys about 5000 m, with both shoaling to the east towards
the Ridge crest where individual bathymetric peaks extend to about
2000 m depth.
- injecting an SF6 tracer and tracking
its dissipation over time; and
- making discrete, instantaneous
estimates of the turbulence using the
The tracer was surveyed in 1996 within two weeks of its release, with
HRP measurements indicating weak turbulent dissipation at all depths
(with a diapycnal diffusivity of about 0.1 cm s) in the
western half of the Brazil Basin where the bottom is smooth.
Mixing rates were much greater over the rough topography, with
measured diapycnal diffusivity values of about
0.5 cm s for the depth and region of the tracer cloud (and
values greater than twice this near the bottom).
A survey cruise in 1997 sampled the distribution of sulfur hexafluoride
about 14 months after its release.
The average diffusivity over the 14 months on the injection isopycnal
was estimated to be at least 1.5 cm s, with values of
10 cm s estimated near the bottom of the canyons.
See Polzin et al. (1997) and
- beach berm
- The nearly horizontal portion of a beach formed by the deposition
of sediment by receding waves. A beach may have more than one
See Komar (1976).
- beach face
- The sloping section of a beach profile below the
beach berm which is normally
exposed to the action of the wave swash.
See Komar (1976).
- Beaufort Sea
- The marginal sea consisting of the waters off the northern
coast of Alaska and Canada. This is bounded to the east by
Banks Island of the Canadian Arctic Archipelago and on the
west by the Chukchi Sea.
The bathymetric characteristics include the narrowest
continental shelf found anywhere in the Arctic Ocean.
This shelf is dissected by three submarine valleys, the
largest of which is 45 km wide, and drops off rapidly
to the Beaufort Deep, whose maximum depth is 3940 m.
Although it is geographically identified as a separate
entity, the Beaufort Sea is oceanographically
an integral part of the
Arctic Ocean and as such can't
be described in isolation.
Substantially different circulation regimes are found on the
inner and outer shelf regions, with the demarcation line
corresponding approximately to the 50 m isobath.
The inner shelf is strongly wind driven in summer, with
a westward water motion driven by the prevailing easterly
winds. This circulation varies seasonally, responding rapidly to large
changes (including even an occasional reversal in prevailiing wind direction),
and is far less energetic
in the winter (with wind effects persisting even under the
fast ice close to the shore).
The outer shelf circulation is energetic at subtidal frequencies
throughout the year, with the dominant feature being the
Beaufort Undercurrent, a
bathymetrically steered mean eastward flow extending from around the 50 m
isobath to at least the base of the continental slope.
This relatively strong current apparently increases with depth
(to around 10 cm s) and is probably not locally driven but
rather part of the large scale circulation in the Canadian Basin,
although the portion of the Undercurrent overlying the shelf can be
modified by local wind forcing.
Frequent cross-shelf motions are found near the inshore edge of the
Undercurrent, with daily means exceeding 5 cm s and durations
typically 3 days or more. These serve to transport materials between
the inner and outer shelf regions.
The most prominent hydrographic feature on the shelf is a subsurface
summer temperature maximum generally found seaward of around 40-50 m depth
which disappears during the winter.
This is associated with an eastward flow of water originating in the
The warm water enters via the eastern
Bering Strait and follows the Alaskan
coast around Point Barrow.
It is composed of two water masses called
Alaskan Coastal Water (ACW) and
Bering Sea Water (BSW).
The ACW has summer temperatures of 5-10 C west
of Barrow with salinities less than 31.5. It mixes rapidly with
local surface water as it moves eastward and is not clearly
identifiable east of around 147-148 W.
The BSW is more saline and has a density range from
25.5-26.0 , and can be traced as far east as
Barter Island at 143 W.
See Fairbridge (1966) and Aagaard (1984).
- Beaufort Sea Mesoscale Project
- A NOAA ERL project undertaken to provide
a quantitative understanding of the circulation over the Beaufort
Sea Shelf and of its atmospheric and ocean forcing. Major emphasis
was placed on providing extensive synoptic oceanographic and
meteorological coverage of the Beaufort Sea during 1986-88.
See Aagaard et al. (1989).
- Beaufort Undercurrent
- See Beaufort Sea.
- Beaufort wind scale
- More later.
- A project to develop a new ice thickness and subglacial topographic model
of the Antarctic region, including bathymetry to 60S.
- Abbreviation for Bottom Ekman Layer, the lowest of three layers into which
the bottom 1000 m of the ocean are sometimes divided, with the other
two being the
BNL and the BML.
The height of the turbulent BEL depends on the near-bottom
current speed and varies in time.
See Klein and Mittelstaedt (1992).
- Belgian Antarctic Expedition
- A research expedition carried out in the Antarctic regions from
1897 to 1899 aboard the ship ``Belgica.''
This was the first vessel to winter in the Antarctic regions.
See Murray and Hjort (1912), p. 16.
- Bellingshausen Abyssal Plain
- One of three plains that comprise the
(the others being the
Amundsen and the
Plains. It is located at around 100-120 W.
- Bellingshausen Sea
- A marginal sea located off Antarctica from approximately
70 to 100 W northwards to the Antarctic Circle.
It is located between Thurston Island to the west and
the Antarctic Peninsula to the east and was named for
the Russian admiral Baron Fabian Gottlieb von Bellingshausen
who led an expedition to Antarctic waters
at the behest of Alexander I in 1819.
He is considered the first to have actually discovered the
continent of Antarctic, those preceding him not having seen
it because of ice and low visibility.
features include Ronne and Marguerite Bay as well as
Peter I, Charcot and Alexander I Islands.
See Fairbridge (1966),
Turner and Owens (1995) and
Grotov et al. (1998).
- Belt Sea
- More later.
- Acronym for Bering Sea Experiment, a US/USSR study of the
Arctic ice cap.
- Acronym for Barotropic Electromagnetic and Pressure Experiment,
which took place in the North Pacific in 1986-87.
See Luther et al. (1990).
- Acronym for BENthic biology and Geochemistry of a north-eastern
Atlantic abyssal Locality. This is a high resolution temporal
and spatial study whose objective is to understand how the
properties of the abyssal boundary layer respond to and modify
the incoming chemical signal from the surface layers and therefore
affect the paleoceanographic record in the underlying sediment.
BENGAL aims to quantify and characterize the incoming flux
(with time-lapse sediment traps and midwater particle cameras),
its resuspension (with
transmissometers and current meters), and
its ultimate deposition (with chemical analysis of core samples and
time-lapse sea-bed photography).
- Bengal, Bay of
- See Bay of Bengal.
- Benguela Current
- A current that flows northward along the west coast of
southern Africa between about 15 and 35 S.
This is the eastern limb of the
circulation system in the South Atlantic Ocean.
See Fairbridge (1966),
Peterson and Stramma (1991) and
Garzoli and Gordon (1996).
- Benguela Current Experiment
- See Garzoli et al. (1999).
- Descriptive of organisms that are attached to or resting on bottom
sediments, as opposed to pelagic.
- One of three major ecological groups into which marine
organisms are divided, the other two being the
nekton and the
The benthos are organisms and
communities found on or near the seabed. This includes
those animals (zoobenthos) and plants (phytobenthos)
living on (epifauna) or in (endofauna) marine
substrata as well as those that swim in close proximity to
the bottom without ever really leaving it.
In terms of size, this is generally divided into
three categories: meiobenthos, the organisms that pass through
a 0.5 mm sieve; macrobenthos, those that are caught by grabs
or dredges but retained on the 0.5 m sieve; and epibenthos,
those organisms than live on rather than in the seabed. Those
in the latter category are usually larger.
Benthic life is subject to vertical zonation depending chiefly
on light, moisture and pressure. This has led to the division
of benthonic animals into two systems and seven zones.
Proceeding from shallow to deep water, the first system
is the phytal or littoral system, composed of the
and circalittoral zones.
The second system, the aphytal or deep system, is composed
See Fairbridge (1966).
- Berghaus, Heinrich (1797-1884)
- See Peterson et al. (1996), p. 65.
- Bering Sea
- A marginal sea located on the northern rim of the
Pacific Ocean centered
at approximately 58 N and 160 W. It is surrounded
by Alaska to the east, Siberia to the west and northwest,
and the Aleutian Island arc to the south. It has an
area of about 2,300,000 km and a volume of about
3,700,000 km. The bathymetry is about equally divided
between a vast shelf to the northeast that is at most
200 m deep and the Aleutian Basin where depths range from
3800-3900 m over most of the region. The Shirshov Ridge
(along 171 E between 500-1000 m depth) and the
shallower Bowers Ridge (along 180 E then turning west
along 55 N) effectively divide the Basin into three parts.
It is connected to
the Arctic Mediterranean Sea via the
Bering Strait and to the
Pacific via several sills between the various Aleutian
Islands, although the main connection is thought to be
between 168 E and 172 W where the sill depth is
about 1590 m.
The main circulation features include a large part of
the westward flowing Alaskan Stream
entering the Bering Sea through the passage centered at
170 W, turning east, and driving a cyclonic (counterclockwise)
gyre in the Aleutian Basin. This largely barotropic current
sees the two main ridges as obstacles which sets up a system of
two eddies, one on each side of the Shirshov Ridge. Eddies have
been observed separating from the eastern limb (often called
the Bering Slope Current) of the Bering Sea gyre, the larger of
the two systems. There is a countercurrent further up the
Bering Slope whose dynamics are those of an
eastern boundary current
in a subpolar gyre. A series of currents and related fronts
largely driven by Alaska Stream inflow through a shallower
passage at 175 W flow
north-northwestward on the broad shelf region.
The main circulation feature of the northern Bering Sea is
the Anadyr Current, a largely
seasonally invariant current flowing northeastward
and supplying most of the Bering Strait throughflow.
This throughflow, driven by sea level differences across the
strait, varies from about 0.1 m/s in the summer to 0.5 m/s in the winter,
with flow through the Shpanberg Strait seasonally shifting
from northward to southward to compensate for the differences.
The shelf flows also make some mostly unknown
contribution to this throughflow.
The western limb of the smaller gyre to the west of the
Shirshov Ridge contributes to and becomes part of the
The local water masses are derived from
Pacific Ocean water masses transported in to the area
and modified by processes on the shelf. This results
in a temperature minimum at or below 100 m, low surface
salinities rapidly rising to about 300 m, and overall
low oxygen concentrations. The water overlying the temperature
minimum is surface water imported from the Alaska Stream, and
the water below that is
Pacific Deep Water.
See Zenkevitch (1963),
Tomczak and Godfrey (1994),
Cokelet and Stabeno (1997) and
Schumacher and Stabeno (1998).
- Bering Slope Current
- A current that flows from southeast to northwest across the Aleutian
Basin of the Bering Sea, parallel to the
continental slope of the eastern Bering Sea shelf.
See Kinder et al. (1975).
- Bering Strait
- A narrow ocean passage separating the North American and
Asian continents. The transport of water through this
passage, estimated at about 0.6 Sv of northward flowing
low salinity water largely supplied by the
to the global budgets of any ocean properties. Its principal
role in large-scale circulation is apparently its contribution
to the stratification of the Arctic Ocean.
See Aagaard et al. (1985),
Coachman and Aagaard (1988) and
Cooper et al. (1997).
- berm crest
- The seaward limit of a beach berm.
- Bermuda Bio-Optics Project (BBOP)
- An ICESS project to explore the relationship
between light and upper ocean geochemistry at the
BATS site off the island of Bermuda.
The goal is to evaluate the role that light plays in the cycling
of carbon, nitrogen, silica, phosphorous and sulfur in the
upper ocean and to assess the ability to study these
processes using the SeaWiFS satellite
- Bermuda High
- See Azores High.
- Bermuda Testbed Mooring Program (BTM)
- A program run by the Ocean Physics Laboratory at
ICESS. This mooring was deployed in June 1994 about
80 km southwest of Bermuda and has provided the oceanographic
community with a deep-water platform for developing, testing,
calibrating, and intercomparing instruments which can obtain
long-term data sets.
- Bernoulli function
- A function defined as:
where is gravitational acceleration,
is the vertical coordinate,
is the pressure and
is the horizontal velocity.
The first two terms of this are called
the Montgomery potential, and
sometimes the Bernoulli function in the geostrophic approximation.
The gradient of this drives the flow in models with z, isopycnal or
sigma coordinates in the vertical.
See Saunders (1995).
- A joint US/USSR Bering and Chukchi Seas research program whose goal is to
examine the status of marine ecosystems of the Pacific Ocean, Bering Sea
and Chukchi Sea, and to assess their role in determining global climate.
The objectives of BERPAC consist of the study of the biogeochemical
cycles of contaminants, related oceanographical processes, and food-web
interactions in the North Pacific waters that flow through the Bering
and Chukchi Seas, including the study of the behavior of organic
pollutants at the water/sediiment interface since sediments are source of the
secondary pollution of ecosystems.
See Nagel (1992).
- A radioactive nuclide with a half-life of 53.3 days
produced by cosmic rays (i.e. electron capture
decay to Li) that can be used as a tracer of ventilation processes
occurring on a seasonal timescale.
It is deposited by rainfall on the ocean surface, and homogenized within
the surface mixed layer, with a fraction found to penetrate into the upper
The extent of penetration before decay depends partly on the strength
of vertical mixing and advective processes.
The distribution below the mixed layer at any time depends largely on
the depth history of the mixed layer, i.e. Beryllium-7 found in the
thermocline can be remnant or previous mixed layers formed within
several half-lives of the isotope (a seasonal timescale).
Thus, if the depth history of the mixed layer is known, then the mixing
and advection component affecting the Beryllium-7 distribution can
be found. Conversely, given an understanding of these processes,
it can be used to interpret mixed layer history on a seasonal timescale.
See Kadko and Olson (1996).
- Acronym for Bering Sea Impact Study.
- beta plane approximation
- In oceanography, a simplified coordinate system for the
equations of motion where the variation of the
Coriolis parameter with
latitude is approximated by
where is the value of at the mid-latitude of the region
and the latitudinal gradient of at that same
latitude. This is used to investigate both equatorial and mid-latitude
phenomena (for which there are slightly different beta plane
approximations) where varies significantly over a few
tens of degrees latitude.
The beta plane approximation allows considerable simplification
of the governing equations and therefore the use of analytical
See Gill (1982).
The beta plane equations are obtained by introducing a background
stratification into the
shallow water equations,
expanding them around a reference latitude with respect
, and keeping terms
up to first order in
This approximation introduces the horizonal coordinates
and expands the Coriolis parameter as
where is the beta paramter at the reference latitude.
The resulting equations (after Muller (1995)) are:
where are the velocity components in the directions,
is the mean radius of the Earth,
is the reference latitude,
is the Coriolis parameter at the reference latitude,
is the beta parameter at the reference latitude,
is a constant reference density,
are motionally induced deviations from
prescribed background fields, and
is the buoyancy frequency.
- beta plane equations
- See beta plane approximation.
- beta refraction
- An effect that results from the latitudinal variation of
Rossby wave phase speed which is, in
turn, due to the beta effect.
If a line of Rossby waves were started along a straight
eastern ocean boundary, then those at low latitudes would
arrive at the western boundary before those at high latitudes.
- beta spiral method
- An inverse method for determining the oceanic velocity field where
the motion is geostrophic and the
potential vorticity locally
balanced. This method provides a mechanism for determining
the absolute geostrophic circulation field rather than just
the relative field.
See Schott and Stommel (1978).
- The amount by which the average of a set of values departs from
a reference value. In statistics and signal processing, it is
usually felicitous to remove this before proceeding to further
and more complicated data manipulations.
- bias correction
- A method of flux correction
that guarantees no long-term climate drift
and reduces the other problems of flux correction. Fluxes are
modified at the ocean-atmosphere interface but the correction is
carried out on mean annual rather than monthly mean values, thus
resulting in smaller and spatially smoother corrections.
An interactive computation is also applied to reduce consistencies
in the bias correction. This method was developed by
J. Oberhuber at the DKRZ.
- The Scripps library contains a Cumulative Biography on the History
of Oceanography, a Bibliography of Ocean Scientists, and a Handlist of
Source Books on the History of Oceanography.
All are available at the given URL.
- Bigelow, Henry Bryant (1879-1967)
- A Harvard-trained zoologist who first went to see on an
expedition to the Maldive Islands with Alexander Agassiz in
1901. He later participated in the Eastern Tropical Pacific
Expedition also organized by Agassiz.
He first led an expedition in 1908 when he took to
Grampus to Gulf Stream waters to collect various faunal
samples. After four years of writing and publishing the
results from these expeditions, the desk-bound Bigelow embarked
on a groundbreaking series of research cruises in the Gulf of
Maine in 1912.
He spent the next 15 years, interrupted briefly by service as
a navigation officer on an army transport, doing repeated studies
of the Gulf of Maine in the manner pioneered by the
ICES in Europe twenty years before.
He studied the fish, plankton and hydrography of the Gulf, repeatedly
taking many measurements over the years including temperatures,
water samples, water color and transparency, currents (using an
Ekman current meter), salinity (using the ICES method of titration and
their Standard Water), quantitative and regular plankton hauls,
and dredging and trawling. In later years he would release drift
bottles to deduce the overall Lagrangian circulation pattern in
Bigelow was an American pioneer in that he was the first
to apply the ICES
methods of repeated measurements over many years to American
waters. The results of the Gulf of Maine studies were published
in separate monographs for the fish (1915), plankton (1926), and physical
oceanography (Bigelow (1927)).
Bigelow also published an autobiography (Bigelow (1964))
and an economic overview of oceanography (Bigelow (1931).
See Graham (1968).
- bioacoustical oceanography
- The application of underwater acoustics to investigations of biological
patterns and processes in the sea.
This has been traditionally divided into two distinct groups of
investigators, those who study the sounds produced by marine organisms, and
those who produce sounds and listen to the returning echoes to study
the distributions of marine organisms.
See Greene et al. (1998).
- Acronym for Biodiversity and Fluxes in Glacial Arctic Fjords,
a project to study the effects of seasonal fluctuations in salinity,
turbidity and sedimentation rates in the glacial fjords
on Svalvard on how the diversity of ice flora and fauna
is structured by stress gradients and the physical ice habitat.
Also studied will be the zonation of macrobenthic organisms
on hard bottom substrates and how this zonation changes
longitudinally in the fjord against the general stress
gradients. The work will involve several diving transects
from inner to outer fjord. This project is being performed
by the Norwegian Polar Institute under the leadership of
Haakon Hop during 1996.
- One of three major components of deep sea sediments, the other two being
Biogenic sediment consists mainly of calcite and opal
produced as the hard parts of organisms and eventually
precipitated. Calcite is formed by coccoliths (plants) and
foraminifera (animals) and opal by diatoms (plants) and
See Broecker and Peng (1982).
- Acronym for Biogas Transfer in Estuaries, a research project
funded by the European Union whose aim is to understand the
distribution of biogases in the surface water of European
estuaries and to quantify related atmospheric exchanges.
- biological oceanography
- The study of life in the oceans and how the physical and chemical
properties of the ocean are influenced by marine life.
The basic goal is to examine the distribution, abundance, and production
of marine species and to obtain a basic understanding of the processes
Compare to chemical,
See Mann and Lazier (1996),
Parsons et al. (1984),
Barnes and Mann (1980),
Day et al. (1989),
Falkowski and Woodhead (1992),
Valiella (1984) and
- biological pump
- The transformation, via
in the ocean surface layer
by plant cells (primarily phytoplankton), of dissolved inorganic
carbon (DIC) into biogenic carbon, including, for example, the CaCO in
shells of coccolithophorids.
The photosynthetic organisms incorporating the inorganic carbon
return much of it to
CO in the surface layer via respiration, but a significant
fraction settles below the main thermocline.
This is an oceanic sink for atmospheric
CO where a rain of small debris consisting of phytoplankton shells
and zooplankton fecal pellets and molts sink out of the ocean surface
waters. These sinking particles remove POC
from surface mixed layers into stratified, relatively deep layers where,
on a millenial time scale, it is no longer susceptible to exchange
with the atmosphere. Particulate matter removed in this manner
is called export flux.
It is estimated that 75% of the difference in DIC concentration
between the surface and deep oceans is due to the biological pump.
If this pump were eliminated, the carbon released from the deep
ocean as it equilibrated with the atmosphere would more than
double the CO2 concentration in the atmosphere.
On a global scale, the downward transport of CO by the
physical (i.e. vertical transport of CO-laden water)
and biological pumps amounts to around 102 Gt C yr.
The upward physical transport is about 100 Gt C yr,
leaving a net uptake of about 2 Gt C yr.
See Rowe and Baldauf (1995) and
- Acronym for Biological Investigations of Marine Antarctic Systems and
Stocks, a program whose principle objective was to gain a deeper
understanding of the structure and dynamic functioning of the Antarctic
marine ecosystem as a basis for the future management of potential
BIOMASS has two major field campaigns, the First (FIBEX) and
Second (SIBEX) International BIOMASS Experiments.
The goal of FIBEX was to determine how much krill is in the Antarctic.
It was composed of 16 research cruises carried out between November 1980
and April 1981, and produced a synoptic picture of the distribution
of krill over a large area of the southern ocean.
The goal of SIBEX was to improve the understanding of the dynamics
of the krill-dominated part of the Antarctic marine ecosystem.
It involved two field seasons, SIBEX-1 (8 cruises, Oct. 1983 to Apr. 1984)
and SIBEX-2 (10 cruises, Nov. 1984 to Apr. 1985), and produced a temporal
sequence of observations focused mainly on the Bransfield Strait and
Prydz Bay regions.
- Biot number
- A dimensionless number or
parameter expressing a ratio of thermal internal resistance to surface
film resistance. It is generally used in heat transfer calculations
such as unsteady state flow. It is defined as:
where is a heat transfer coefficient, the thermal conductivity, and
a mid-plane distance.
- A program to study bioluminescence and optical variability in
See Marra and Hartwig (1984).
- The stirring of sediment by animal life.
- Bismarck Sea
- A regional sea located in the northwest corner of the South Pacific
The Bismarck Sea is bounded to the southwest by New Guinea and
to the north, east, and south by the Bismarck Archipelago.
Its area and volume are about 40,000 km and 60,000 km, respectively.
- Acronym for Biophysical Interdisciplinary Tropic Studies buoy, an
instrumented and unmanned mooring designed to acoustically measure
the size and abundance of marine life populations, collect the
supporting data that characterizes the marine environment, and automatically
transmit the data to shore stations for analysis.
The BITS system was developed by Tracor and the University of
It employs a bi-frequency acoustic projector which operates at
165 kHz and 1.1 MHz, with backscattered acoustic signals received
by the sensors transmitted via VHF packet telemetry to shore stations.
- Abbreviation for
Banda Intermediate Water.
- Bjerknes, Jacob (1897-1975)
- One of the founders of modern meteorology, Bjerknes entered and
revolutionized the field at the age of 20 with his discovery of
the structure of extratropical cyclones.
His father was the physicist and geophysicist
- Bjerknes, Vilhelm
- More later.
- Bjerknes hypothesis
- The hypothesis that ENSO varies as a self-sustained
cycle in which anomalies of SST in the Pacific
cause the trade winds to strengthen or slacken, and that this in
turn drives the changes in ocean circulation that produce
anomalous SST. First advanced by Bjerknes (1969).
- Bjerknes' theorem
- A generalization of
that enables the calculation
of the circulation on a rotating Earth.
See Turner (1973), Hide (1978), and
- Black Sea
- A mediterranean sea, centered
at approximately 35 E and 44 N, that is the world's
largest inland water basin. It has an area of about
461,000 km and a volume of 537,000 km with a mean
depth of around 1200-1300 m, although depths greater than
2000 m are common in the central basin. The western part of
the Black Sea is a wide shelf that gradually narrows to the
south and breaks at around 100-150 m. In the rest of the
basin the shelf doesn't exceed 10-15 km in width.
It is connected to the
Marmara Sea via the narrow (760 m wide)
and shallow (27.5 m maximum depth)
Bosporus Strait, and further
connects to the Mediterranean Sea
via the long and narrow Dardanelles.
It is also connected to the
Sea of Azov to the north.
The Black Sea is a dilution basin
due to a large freshwater input from the Danube, Dniester,
Dnieper, Severskiy Donets and Don rivers (350 km/yr).
The flow through
the Bosporus comprises a surface flow of low salinity water
towards the Mediterranean (260 km/yr)
and an underlying return flow of salty
Mediterranean water (120 km/yr).
Precipitation (140 km/yr) and evaporation (350 km/yr)
close the freshwater budget.
The volume averaged salinity is 22, with surface salinities
in the central
part ranging from 16-18 and increasing to 21-22.5 at depths
greater than 150-200 m.
The surface temperatures range from
25 C in the summer to 6-8 C in the open sea, with the
northwestern part and the Sea of Azov covered with ice during
the winter. The deep water is 8-9 C year round.
The upper 50 m are saturated with oxygen, the content of
which diminishes until, at a depth of 150-200 m, hydrogen
sulfide appears and renders the lower regions uninhabitable.
The most remarkable circulation feature is the cyclonicically
meandering Rim Current, the
interior of which is formed either by one elongated cell covering
the entire basin or by two separate cyclonic cells occupying
the western and eastern halves of the basin.
The interior of the Western and Eastern Gyres contains a number
of recurring cyclonic mesocale eddies.
These are in contact with each other by a recurrent anticyclonic
eddy called the Central Basin Eddy, a recurrent feature observed to
form via the merging of two anticyclonic eddies pinched off from the
baroclinically unstable Rim Current southeast of Crimea and off
The upper layer flow field also consists of several mesoscale
eddies distributed along the periphery of the basin.
The two most pronounced and persistent of such are the anticylonic
Batumi Eddy in the southeastern corner of the basin and the anticyclonic
Sevastapol Eddy in the continental shelf topography of the Danube Fan,
west of the Crimean Peninsula. The latter has also been reported in
the literature as the Trabzon Eddy.
Two other quasi-permanent anticyclonic eddies are found along
the Anatolian (Turkish) coastal belt. They are situated off the
Sakarya and Kizilirmak Rivers and given their names.
Another quasi-permanent anticyclonic feature is the Bosphorous
Eddy located northwest of the Bosphorous-Black Sea junction.
Two other recurrent coastal anticyclonic eddies have been identified
between Sakarya Canyon and Cape Sinop.
Along the northern coast, the anticyclonic Crimean and Causasian Eddies are the
most pronounced mesoscale features, with the Kali-Akra Eddy a
recurrent feature to the north of the Bosphorous Eddy.
The intermediate depth circulation is characterized by the disappearance
of the Rim Current, the shifting of eddy centers, coalescence of eddies,
persistence of some features for the whole water column but changes with depth
in the structure of others, and more organized and large sub-basin
See Caspers (1957),
Oguz et al. (1993),
Ö (1997) and
- Black Sea Oceanography Expedition
- See () and other papers therein.
- Black Sea Water (BSW)
- A water mass formed in the
Black Sea that flows into the
Aegean Sea through the Strait of Bosporus,
the Marmara Sea and the Strait of Dardanelles.
The flux into the Aegean varies from 180-200 km yr to a
maximum of 700 km yr between April and October.
BSW is of primary importance to processes in the Aegean, but plays
a secondary role in the overall water balance of the Mediterranean.
BSW is recognized by a surface salinity minimum, with the salinity
off the mouth of the Strait of Dardanelles varying from 24 to 26 psu during
the warm months and from 30-35 psu during the cold months.
A pronounced halocline develops in the North Aegean, with the maximum
depth ranging from 20-80 m.
As it travels westward and southward, BSW is modified following the
general cyclonic circulation of the Aegean.
During the winter, it spreads westwards and then northwards, entering
the Samothraki Plateau. It flows westwards over the plateau and then
southwards along the eastern coast of the mainland to Evvia Island.
If the thermohaline front in the Andros Strait is well developed,
the BSW flows eastwards along the northern boundaries of the
Kyklades Plateau, following the general cyclonic circulation.
If the thermohaline front disappears, the BSW bifurcates, with one
branch moving eastwards along the northern boundary of the Kyklades
Plateau and the other southwards into the Saronikos Gulf, causing
the winter salinity minima seen there.
During the summer, the general cyclonic circulation pattern still
prevails, with the Etesian winds causing the BSW to flow southwestwards to
Evvia Island and then southwards.
The low salinity waters flow through Andros Strait and create the
second salinity minimum observed in the South Evvoikos and
Saronikos Gulfs. It has been detected (by the surface salinity
minimum) as far south as the Kithira Straits.
See Stergiou et al. (1997).
- Black Stream
- See Kuroshio Current.
- Acronym for Benthic Layer Interactive Profiling System.
See Adam Jr. (1990).
- Abbreviation for Bottom Mixed Layer, the middle of three layers into which
the bottom 1000 m of the ocean are sometimes divided, with the other
two being the
BNL and the BEL.
The thickness of the BML typically ranges from 20-80 m, although
values between 10-150 m have been observed.
The particle concentration within the BML is usually homogeneously
mixed, although occasional episodes of local resuspension by strong
bottom flows can change this.
See Klein and Mittelstaedt (1992).