- Acronym for Great Australian Bight.
- GABEX I
- Acronym for Georgia Bight Experiment I.
See Lee and Pietrafesa (1987).
- GABEX II
- Acronym for Georgia Bight Experiment II.
See Paffenhöfer et al. (1987).
- Acronym for Guiana Abyssal Gyre Experiment.
- Acronym for Genesis of Atlantic Lows experiment.
See Bane (1989) and
Lee et al. (1989).
- Acronym for the GEWEX Asian Monsoon experiment,
the goal of which is to understand the role of the Asian monsoon in
the global climate system and develop methods for long-range
- Acronym for the Global Atmospheric Research Program, planned and
coordinated jointly starting in 1968 by the
WMO and the ICSU.
- Gaspé Current
- A current in the
Gulf of St. Lawrence usually
recognized as a baroclinic coastal jet driven by runoff and reinforced
by transverse currents from the gulf's north shore.
It has a peak near surface speed of 50 cm s, and a substantial
fraction of the transport appears to recirculate in the
See Benoit et al. (1985) and Han et al. (1999).
- 1. Acronym for GARP Atlantic Tropical
2. Acronym for Global Acoustic Transmission Experiment.
- Abbreviation for
Great Barrier Reef Undercurrent.
- Abbrevation for General Circulation Drifter.
- See general circulation model.
- Acronym for the Global Climate Observing System, a global observing
program planned jointly by ICSU,
and IOC of
It was established to develop a dedicated observing system
designed specifically to meet to observation requirements
for monitoring climate, detecting climate change, and for
predicting climate variations and change. The objectives of
GCOS are to meet the observational needs for climate system
monitoring, climate change detection and response monitoring,
especially in terrestrial ecosystems; data for application
to national economic development; and research toward
improved understanding, modeling, and predicting the
A Joint Scientific and Technical Committee (JSTC) and
a Joint Planning Office (JPO) were set up to develop the plans
and strategy for implementation of the system. See the
GCOS Web site
for more information.
- Abbreviation for
Global Drifter Center.
- Abbreviation for General Digital Environmental Model, a
four-dimensional (latitude, longitude, depth, and time)
digital model of temperature and salinity for the North and
South Atlantic, the Pacific, the Indian
Ocean north of 40 S, the Arctic Ocean, the Mediterranean
Sea, and the Black Sea. It consists of coefficients of
mathematical expressions describing vertical profiles of
temperature and salnity on a half degree latitude-longitude
grid for seasonal and annual time frames, with the actual
profiles generated by combining the coefficients with the
equations. Some regions are being updated to 10 minute
Data for creating the GDEM were obtained from
the Master Oceanographic Observational Data Set (MOODS)
as well as from the Levitus climatology. It is used by
the U.S. Navy for most of its operational systems.
See Teague et al. (1990).
- Abbreviation for
Global Drifter Program.
- Abbreviation for Global Digital Sea Ice Data Bank.
- Acronym for GEneral Bathymetric Chart of the Oceans, a map
series established by Prince Albert I of Monaco in 1903.
This is at present an activity of the IOC.
- Abbreviation for geomagnetic electrokinetograph.
- Dissolved material in sea water that is resistant to bacterial
attack. Its name comes from the yellow color it imparts to the
water. Brown algae, the principal algae group growing in coastal
waters of temperature and higher latitudes,
excrete phenolic compounds. These polyphenols are converted
into a brown polymer by secondary reactions with carbohydrates
and proteins of algal origin. The properties of the resulting
substance are identical with Gelbstoff. Its concentration in
sea water is around 1 mg/l and it is removed mainly by
precipitation since its phenolic nature renders it resistant
to bacterial attack. This is also known as yellow substance
See Riley and Chester (1971).
- A branch of applied mathematics which determines by observation and
measurement the exact positions of points and the figures and areas
of large portions of the earth's surface, the shape and size of
the earth, and the variations of terrestrial gravity.
See Torge (1991).
- Acronym for Geochemistry and Dynamics of the Mediterranean,
an MTP Core Sub-project whose aims are
to monitor the evolution of the physical and chemical
characteristics of western deep water and the detect similar
changes in the different Mediterranean basins, to describe
and quantify transfer processes at air-land-sea interfaces,
and to give a new picture of phytoplankton distribution,
new production and chemical transfers.
GEODYME Web site.
- geological oceanography
- More later.
Compare to biological,
- A hypothetical, global, and continuous sea-level
surface perpendicular to the direction of gravity at all points.
- geophysical model function
- A function used in wind scatterometry to relate the actual
measured parameter i, the normalized
radar cross-section, to the near-surface wind speed and direction.
At a given frequency, the function can be expressed as:
where is the normalized radar backscatter coefficient,
is the wind speed,
the relative azimuth angle between the incident electromagnetic
represents the (possibly small) effects of non-wind variables
such as long waves, atmospheric stratification, water temperature, etc.,
the incidence angle, and
There are many existing model functions that differ in various details,
although some common features are shared. These include:
See Naderi et al. (1991).
- at fixed incidence angle all model functions predict an increase
in with wind speed (for moderate wind speeds);
- the wind speed dependence at a fixed incidence and azimuth angle is
frequently expressed as a power law; and
- for a given wind speed, exhibits a biharmonic dependence
on the wind direction.
- Acronym for Geodynamics Experimental Ocean Satellite, a series of
satellites designed exclusively for geodetic studies.
They were flown as part of the National Geodetic Satellite Program.
The instrumentation varied with each mission.
The objectives were to:
- locate observation points (geodetic control stations) in a 3-D
earth center-of-mass coordinate system within 10 m of accuracy;
- determine the structure of the earth's gravity field to 5 parts in
- define the structure of the earth's irregular gravitational field and
refine the locations and magnitudes of the large anomalies; and
- compare results of the various systems on board the spacecraft to
determine the most accurate and reliable system.
- Acronym for Geodetic Satellite, a U.S. Navy satellite designed to measure
sea surface heights to within 5 cm.
It was launched on March 12, 1985 with a primary mission of obtaining a
high-resolution description of the marine geoid up to latitudes of
This first or geodetic mission (GM) was completed 18 months after data
collection began on March 30.
During this mission the ground track had a near-repeat period of
of about 23 days (330 revolutions in 23.07 days, average orbital
period of 6039.84 sec).
The GM data were initially classified but released to NOAA for
public distribution in 1995.
The satellite orbit was changed at the conclusion of the GM on
September 30, 1986, followed by the start of the
scientific Exact Repeat Mission (ERM) on November 8, 1986.
The ERM produced sea level profiles along tracks that repeated
themselves within 1-2 km at intervals of about 17 days (244 revolutions
in 17.05 days, average orbital period of 6037.55 sec).
It covered 62 complete 17-day cycles before the failure of the second
tape recorder on October 1989 terminated the mission.
See Douglas and Cheney (1990).
- Acronym for Geochemical Ocean Sections Study, a global survey of
the three-dimensional distribution of chemical, isotopic and
radiochemical tracers in the ocean.
It was designed to establish a baseline database for assessing
future chemical changes in the world's oceans and to provide
a better understanding of large-scale oceanic transport and
The expeditions were in
the Atlantic from July 1972 to May 1973 (121 stations);
the Pacific from August 1973
to June 1974 (147 stations); and
the Indian Ocean from December 1977 to March 1978 (141 stations).
The logistics and handling of GEOSECS cruises and analyses were
coordinated by SIO and directed by Arnold Bainbridge.
The C analyses for all three oceans are summarized
in Stuiver and Ostlund (1980),
Ostlund and Stuiver (1980) and
Stuiver and Ostlund (1983).
- Acronym for Geophysical and Oceanographic Station for Abyssal
Research, a project to develop an innovative deep sea benthic
observatory devoted to continuous and long-term geophysical,
oceanographic, and geochemical observations.
- general circulation model
- Generally a three-dimensional time-dependent model of the atmosphere
and/or ocean circulation. The solution to a set of mathematical equations
governing the motions of a layer of fluid on a spherical planet is numerically
approximated on a three-dimensional discrete grid of points to obtain
temperatures, velocities, rainfall, pressure and any of several other
that collectively comprise the state of the
climate. Often abbreviated as GCM.
See Washington and Parkinson (1986).
- geophysical fluid dynamics (GFD)
- An interdisciplinary field of study for understanding fluid flows which
occur naturally, e.g. the general circulation of the atmosphere, oceanic
circulations, mantle convection, and the motions which drive the
geodynamo. This is accomplished through mathematical, numerical and
- The potential energy per unit mass of a body due to the Earth's
gravitational field as referred to an arbitrary zero reference
level. A unit of geopotential is the potential energy acquired
by a unit mass on being raised a unit distance in a gravitational
field of unit strength.
- geopotential distance
- See dynamic height.
- geopotential height
- See dynamic height.
- geopotential surface
- A surface to which the force of gravity is everywhere
perpendicular and equal.
No work is necessary for the displacement of mass along a
potential surface as long as no other forces act in addition to
gravity. This can also be defined as a surface of equal
dynamic height below the level of
the sea surface,
using the ideal sea surface level as a reference surface
with the potential value 0.
This has also been called a potential surface or a level surface.
- geopotential thickness
- See dynamic height.
- That which is due to geostrophy.
- geostrophic adjustment
- The mutual adaptation of mass and momentum toward a steady geostrophic
state in rotating fluids.
The adjustment problem was first considered by Rossby (1938), who
derived the geostrophically balanced steady end state for an ocean
to which momentum is impulsively imparted.
The end state always possesses less energy than the initial state, a fact
due to the end state being achieved through decaying inertial
oscillations which disperse energy away in pulses of Poincare waves.
See Blumen (1972) and
Kuo and Polvani (1997).
- geostrophic approximation
- The use of the geostrophic wind as an
approximation to the actual wind in the equations of motion.
- geostrophic balance
- See geostrophy.
- geostrophic current
- A current resulting from geostrophy.
Analogous to the
geostrophic wind concept in
- geostrophic force
- A virtual force used to account for the change in direction of the
wind relative to the Earth's surface. It results from the
Earth's rotation and the Coriolis force.
- geostrophic method
- A method for determining the relative
geostrophic flow field in
the ocean from the distribution of density in the ocean.
An absolute geostrophic flow field can additionally be
found with the additional assumption of a
level of no motion.
- geostrophic turbulence
- Turbulent flow that exists in flows that are in near
geostrophic balance. The physical effects of rotation and
stratification provide basic constraints on the flow.
- geostrophic velocity
- Those velocities exhibited by geostrophic currents due to
- geostrophic wind
- The result of geostrophy in the atmosphere.
Analogous to the geostrophic current in
- The balance between the Coriolis force
and the horizontal pressure gradient that determines the first order
circulation patterns in the open ocean.
This balance is expected to hold for most latitudes but to break down
near the equator where the local vertical component of the
Coriolis force vanishes, although comparisons between geostrophic
estimates and direct measurements have shown it to hold within
fractions of a degree from the equator.
Geostrophy allows the large scale flow of the oceans to be determined
by mapping the horizontal pressure distribution, although such
solutions are degenerate in that they only allow the current fields
to be determined relative to an absolute reference level.
Various methods have been used to determine absolute current
fields via the assumption of geostrophy.
Inverse methods use constraints
such as mass conservation or tracer balances to find a
reference velocity for each
station pair (Wunsch, 1996).
A more traditional method is to find the reference velocities
using geostrophy and mass
conservation along with qualitative determinations of flow
reversals based on tracer fields
Satellite altimetry is making
it possible to determine the absolute height of the sea surface
relative to a geoid and thus be usable as
a reference level.
- Gerard barrel
- A barrel used to collect water samples in oceanography.
It holds 250 liters of sea water.
- German Deep-Sea Expedition
- An investigation of the physical and biological conditions
of the Atlantic and Indian oceans during 1898 and 1899 by
a research team aboard the ``Valdivia.''
This expedition penetrated into the Antarctic as far as the
ice would permit.
The results were issued as a series of memoirs under the
editorship of Chun, the leader of the expedition.
See Murray and Hjort (1912), p. 16.
- Gerstner wave
- A wave theory developed for periodic waves of finite height to
surpass the limitations of
Stokes wave theory.
The equations are simple to use and
the solutions are exact and satisfy continuity as well as the
pressure conditions at the water surface, and experimental
studies have shown that the theory closely approximates the
profiles of real waves on a horizontal bottom. Drawbacks
include that mass transport is not predicted, the velocity
field is rotational, and the particle movements are opposite
to that expected in real waves (and found in other theories).
The predictions of both Gerstner and Stokes wave theories
agree equally well with measured wave profiles. This is well
explained by the fact that if the Gerstner wave equations are
expanded into a series the first three terms are identical to
those in the Stokes solution. This similarity in predictive ability
and greater ease of use lead to the preferential use of Gerstner
wave theory in many engineering applications where its limitations
are not significant. This has also been called
trochoidal wave theory since the elevation profile takes the
form of a trochoidal curve.
See Komar (1976) and LeMehaute (1976).
- Acronym for the
Global Energy and Water Cycle Experiment. Initiated in 1988 by
the WCRP to observe and model the
hydrologic cycle and energy fluxes in the atmosphere, at the
land surface, and in the upper oceans. It is an integrated
program of research, observations, and science activities
leading to the prediction of global and regional climate change.
GEWEX hydrometeorology and land-surface projects include
the GRDC, ISLSCP,
GAME, LBA, and
MAGS. Radiation projects include
the BSRN, CPRP,
ISCCP, and SRB.
Modeling and prediction projects are
GCSS, G-NEP and
GEWEX Web site.
- Abbreviation for
- Abbreviation for
Global Hydrology and Climate Center.
- Gibb's phenomenon
- An artifact of attempting to approximate a function or waveform
with a discontinuity using a Fourier series or some other
global, continuous basis function. The fit is poor in a region near the
discontinuity, usually characterized by large oscillations within
the region. Increasing the number of components in the approximation
decreases the region of poor fit, which theoretically vanishes with
an infinite number of components.
- Gibraltar Experiment
- See Kinder and Bryden (1987).
- See Gelbstoff.
- GIN Sea
- Abbreviation for Greenland/Iceland/Norwegian Sea, an area that
has also variously been called the Norwegian Sea and the
Nordic Seas. The GIN Sea together with the
Polar Sea constitute the
Arctic Ocean in some classification
schemes (with others including the GIN Sea within the
confines of the Atlantic). The former may perhaps be preferred
for geomorphological as well as hydrographical reasons. The
bottom is continuously oceanic in crust and depth through the
connecting passage (to the north) of Fram Strait, while the
southern connection is over a continental ridge, i.e. the
Greenland-Scotland Ridge. Also, the deep thermohaline circulation
processes of the GIN and the Polar Sea are closely linked.
The GIN Sea comprises two major basins: the Greenland Basin and
the Greater Norwegian Basins (i.e. the Norwegian Basin and the
Lofoten Basin) separated by the Mohn Ridge. It has six open
boundaries through which important exchanges occur: Fram Strait
connecting to the Polar Ocean
to the north, three boundaries over the Greenland-Scotland
Ridge that connect with the Atlantic Ocean, and two boundaries
connecting to continental shelf seas, i.e. the North Sea and
the Barents Sea.
See Hopkins (1991).
- Global Drifter Center (GDC)
- An AOML data center located in Miami, Florida that
manages the deployment of drifting buoys around the world. Global
Lagrangian Drifters (GLD) are placed in areas of interest using
research ships, VOS, and U.S. Navy aircraft.
Once they are operationally verified, the data is telemetered to
the GDS and disseminated to interested parties everywhere.
GDC Web site.
- Global Drifter Program (GDP)
- A NOAA AOML
program whose objectives are to: (1) described mixed-layer
velocity on a 5 degree resolution global basis and produce
new charts of seasonal surface circulation; (2) provide an
operational data stream for SST, sea level pressure, and surface
velocity data; (3) verify global climate models; (4) compute
single particle diffusivities, eddy statistics, and interannual
to annual variability; (5) construct models of wind-driven
currents; and (6) obtain high resolution coverage in special
regions for process studies. The program was started in
GDP Web site.
- Global Energy and Water Cycle Experiment
- GEWEX was initiated in 1988 by the WCRP
as a program designed to observe and model the
hydrologic cycle and energy fluxes in the atmosphere, at the land
surface, and in the upper oceans. The International GEWEX Project
Office (IGPO) is the focal point for the planning and development of all
GEWEX projects and activities.
See Chahine (1992) and Chahine (1992) and the
GEWEX Web site
for further information.
- Global Hydrology and Climate Center
- A research center, abbreviated GHCC, whose
objective is to address global hydrological processes. See the
GHCC Web site.
- Global Precipitation Climatology Project
- A GEWEX-affiliated project, abbreviated GPCP,
designed to provide global data sets
of area, time-averaged precipitation for a minimum period of 10 years
(1986-1995). This data will be produced by merging geostationary
and polar-orbiting satellite microwave and
infrared data with rain
gauge data from more than 6000 stations. More information can be
found at the
GPCP Web site.
See Arkin and Xie (1994).
- Global Runoff Data Center
- A GEWEX project, abbreviated GRDC,
to compile a global data base of stream
flow data for the development and verification of atmospheric and
hydrologic models. More information can be obtained at the
GRDC Web site.
- Global Terrestrial Observing System
- The GTOS is a
global observing program planned jointly by FAO,
WMO, and UNEP.
- Acronym for Global Ocean Ecosystem Dynamics, a component of
IGBP developed and sponsored by
SCOR, the IOC,
the ICES, and
PICES. Its goal is advance our
understanding of the structure and functioning of the
global ocean ecosystem, its major subsystems, and its response
to physical forcing to where we can develop and capability to
forecast the marine upper trophic system response to scenarios
of global change. GLOBEC concentrates on zooplankton population
dynamics and its response to physical forcing in pursuit of this
goal. See the
GLOBEC Web site
U.S. GLOBEC Web site.
- globigerina ooze
- A type of calcareous ooze composed of the shells of unicellular
creatures called globigerina that live in the waters of warmer
ocean regions. These oozes are seldom found above 5000 m depth
and cover about 35% of the surface of the sea floor.
See Neumann and Pierson (1966) and
- Acronym for Global Continental Palaeohydrology Project, an activity
- Acronym for Global Land-Ocean River Inputs database.
- Acronym for the Global Sea Level Observing System, an
IOC-coordinated project for the establishment
of a strategic gloval core network of about 300 tide gauges around
the world for long term climate change and oceanographic sea level
monitoring. These gauges are spaced about 1000 km apart along
coastlines and on oceanic islands and provide hourly-resolution
standardized sea level data.
See Tolkatchev (1996)
and the GLOSS Web page.
- Acronym for Global Undersea Pressure data set, a global data bank for
ocean bottom pressure measurements established by a 1999
IAPSO resolution and maintained by
The GLOUP data are archived in either high frequency (typically hourly
or every 15 minutes) or daily format.
The high frequency data contain the total pressure, predicted pressure
from a tidal analysis, and residual pressure. The tidal analysis is
performed using 63 constituents for records longer than 12
lunar months, and 55 independent and 2 related
constituents for records longer than 6 lunar months.
Records shorter than 25 days contain no tidal predictions or residuals.
Daily values are only produced for records longer than 25 days, and
contain two values for each day calculated from residual pressures from
the high frequency data. The first value is a simple average of the
residual pressures during that day, and the second a value filtered
with a Doodson X0 filter
to remove any residual signal at tidal
- Abbreviation for Gulf of Mexico Program.