Environment, Ocean Science and the Natural World

Physical and chemical oceanography and marine meteorology glossary

The ocean as a moving, stratified, chemically active fluid coupled to the atmosphere: thermohaline overturning and the AMOC, Ekman transport, geostrophic and western boundary currents, the seawater carbonate system, dissolved oxygen and nutrients, and salinity under TEOS-10. Marine meteorology adds air-sea flux, ENSO and teleconnections, tropical cyclones, sea state, and marine heatwaves, with bodies such as IOC-UNESCO, WMO, NOAA, and the Argo programme.

263 defined terms.

Showing 250 on this page (page 1 of 2).

A

Abyssal Zone: Ocean depth zone from approximately 4,000 to 6,000 meters, characterized by near-freezing temperatures and high pressure.
Acoustic Doppler Current Profiler (ADCP): Instrument that measures water current velocities over a depth range using the Doppler effect.
Adiabatic Lapse Rate: Rate at which an air parcel cools or warms as it rises or descends without exchanging heat with surroundings.
Advection: Horizontal transport of a water property by ocean currents.
Aerosol Optical Depth (AOD): Measure of aerosols distributed within a vertical column of the atmosphere.
Agulhas Current: Strong western boundary current of the southwest Indian Ocean off the east coast of Africa.
Air-Sea Flux: Exchange of heat, moisture, momentum, or gases across the ocean-atmosphere interface.
Alkalinity: Capacity of seawater to neutralize acid, a key parameter of the carbonate system.
Ammonium: Reduced nitrogen species (NH4+) used by phytoplankton and a key nutrient in seawater.
AMOC: Atlantic Meridional Overturning Circulation, the large-scale overturning circulation of the Atlantic.
Anomaly: Departure of an observed value from a long-term climatological mean.
Antarctic Bottom Water (AABW): Dense, cold water mass formed around Antarctica that fills the deep global ocean.
Antarctic Circumpolar Current (ACC): World's largest ocean current, flowing eastward around Antarctica.
Antarctic Intermediate Water (AAIW): Cool, low-salinity water mass found at intermediate depths in the Southern Hemisphere oceans.
Apparent wind: Wind perceived from a moving vessel.
Aragonite Saturation State: Indicator of whether seawater is corrosive or favorable to aragonite-shelled organisms.
Argo Program: International array of profiling floats measuring temperature, salinity, and biogeochemistry of the upper 2,000 meters.
Atmospheric Boundary Layer: Lowest part of the atmosphere directly influenced by contact with the sea surface.
Atmospheric Pressure: Force per unit area exerted by the weight of the atmosphere, measured in hectopascals.
Available Potential Energy: Portion of total potential energy that could be converted to kinetic energy under adiabatic adjustment.

B

Baroclinic: Condition where pressure surfaces and density surfaces intersect, allowing energy conversion.
Barotropic: Condition where pressure depends only on density, with coincident pressure and density surfaces.
Bathythermograph (BT): Instrument that records temperature versus depth as it is lowered through the water column.
Beaufort scale: Empirical wind force scale 0-12.
Benguela Current: Cold eastern boundary current along the southwest coast of Africa.
Bergeron Process: Ice crystal growth mechanism in mixed-phase clouds important to precipitation.
Bermuda High: Semi-permanent subtropical high pressure system over the North Atlantic.
Beta Effect: Variation of the Coriolis parameter with latitude, influencing Rossby wave propagation.
Bicarbonate: HCO3-, the dominant form of dissolved inorganic carbon in seawater.
Biogeochemical Argo (BGC-Argo): Argo float subset equipped with chemistry and biology sensors.
Black Body Radiation: Thermal emission used to derive sea surface temperature from satellite infrared radiometers.
Boundary layer: Thin viscous region adjacent to the hull.
Boussinesq Approximation: Simplification treating density variations as negligible except in buoyancy terms.
Brazil Current: Warm western boundary current of the South Atlantic.
Brunt-Vaisala Frequency: Natural frequency of vertical oscillation in a stratified fluid.
Buoyancy Flux: Rate at which buoyancy is exchanged across an interface, often through heat and salt fluxes.

C

California Current: Cold eastern boundary current of the North Pacific along western North America.
Carbonate Compensation Depth (CCD): Depth below which calcium carbonate dissolves faster than it accumulates.
Carbonate System: Equilibrium chemistry of CO2, bicarbonate, carbonate, and pH in seawater.
Centennial Variability: Climate variations on timescales of about a century.
CFC Tracer: Use of chlorofluorocarbons as transient tracers of ocean ventilation.
Chlorinity: Mass of chloride per kilogram of seawater, historically used to estimate salinity.
Chlorophyll-a: Pigment in phytoplankton commonly measured to estimate ocean primary productivity.
Climate Reanalysis: Reconstruction of past climate states by assimilating observations into models.
Coastal Upwelling: Wind-driven uplift of cold, nutrient-rich water along a coastline.
Conductivity-Temperature-Depth (CTD): Standard oceanographic instrument package for profiling water column properties.
Conservative Temperature: TEOS-10 thermodynamic variable representing heat content per unit mass.
Continental Slope Current: Persistent current flowing along the continental slope, often poleward.
Convergence Zone: Region where surface currents or air streams flow together, often producing fronts.
Coriolis Parameter: Quantity (f = 2 omega sin phi) describing Earth rotation effects on geophysical fluids.
Cromwell Current: Equatorial Undercurrent of the Pacific Ocean.
Cyclogenesis: Process of formation and intensification of a low-pressure system.

D

Deacon Cell: Apparent meridional overturning cell in the Southern Ocean, largely an artifact of Eulerian averaging.
Decadal Variability: Climate variability on roughly 10-year timescales, such as the Pacific Decadal Oscillation.
Deep Western Boundary Current (DWBC): Equatorward flow of North Atlantic Deep Water along the western Atlantic.
Density Driven Circulation: Flow caused by horizontal density gradients, fundamental to thermohaline circulation.
Diapycnal Mixing: Mixing across density surfaces in a stratified ocean.
Dissolved Inorganic Carbon (DIC): Sum of CO2, bicarbonate, and carbonate ions dissolved in seawater.
Dissolved Organic Carbon (DOC): Operationally defined fraction of organic carbon passing through a filter.
Dissolved Oxygen (DO): Concentration of O2 in seawater, vital for marine respiration.
Diurnal Cycle: Variation occurring on a daily timescale, such as sea surface temperature heating.
Dobson Unit: Unit measuring the thickness of the ozone layer.
Doldrums: Equatorial region of light and variable winds within the ITCZ.
Downwelling: Vertical sinking motion of surface water due to convergence or wind forcing.
Drag Coefficient: Dimensionless parameter quantifying air-sea momentum transfer.
Drifter: Surface or subsurface device that follows currents to measure Lagrangian flow.

E

ECMWF: European Centre for Medium-Range Weather Forecasts, an intergovernmental forecasting organization.
Eddy Kinetic Energy: Kinetic energy associated with mesoscale fluctuations in ocean currents.
Ekman Layer: Surface or bottom layer where wind or bottom friction transfers momentum.
Ekman Pumping: Vertical motion driven by divergence or convergence of Ekman transport.
Ekman Spiral: Theoretical wind-driven current that rotates with depth due to Coriolis force.
Ekman Transport: Net horizontal mass transport in the Ekman layer, perpendicular to wind direction.
El Nino: Warm phase of ENSO with weakened trade winds and warming of the eastern tropical Pacific.
ENSO: El Nino-Southern Oscillation, the dominant interannual coupled ocean-atmosphere mode in the tropical Pacific.
Enthalpy: Thermodynamic property combining internal energy and pressure-volume work.
Equatorial Counter Current: Eastward flowing current between the North and South Equatorial Currents.
Equatorial Undercurrent: Subsurface eastward jet along the equator.
Eulerian Measurement: Observation at a fixed point in space, such as a moored current meter.
Eutrophication: Nutrient enrichment leading to excessive plant or algal growth.
Evaporation Minus Precipitation (E-P): Net freshwater flux at the ocean surface.

F

Ferrel Cell: Mid-latitude atmospheric circulation cell between the Hadley and Polar cells.
Float (Profiling): Autonomous oceanographic instrument that cycles vertically, such as Argo floats.
Fram Strait: Passage between Greenland and Svalbard, the main deep connection between Arctic and Atlantic.
Free Surface: Air-sea interface allowed to move in dynamic ocean models.
Frequency Spectrum: Distribution of variance with frequency, used in wave and current analyses.
Frontal Zone: Boundary between water masses of different temperature or salinity.
Fugacity of CO2 (fCO2): Effective partial pressure of CO2 accounting for non-ideal gas behavior.

G

Gas Exchange Velocity (k): Rate constant for air-sea gas transfer.
Geopotential Height: Height of a pressure surface above mean sea level adjusted for gravity.
Geostrophic Balance: Balance between Coriolis force and horizontal pressure gradient.
Geostrophic Current: Current resulting from geostrophic balance, common in the ocean interior.
GHRSST: Group for High Resolution Sea Surface Temperature analyses.
Global Drifter Program: NOAA-led array of satellite-tracked surface drifters.
Global Ocean Observing System (GOOS): IOC-UNESCO coordinated framework for sustained ocean observation.
GO-SHIP: Global Ocean Ship-based Hydrographic Investigations Program for repeat hydrography.
Greenhouse Effect: Atmospheric warming due to absorption and re-emission of infrared radiation.
Gulf Stream: Warm western boundary current of the North Atlantic.

H

Hadley Cell: Tropical atmospheric overturning circulation between the equator and around 30 degrees latitude.
Halocline: Vertical layer with a strong salinity gradient.
Heat Capacity: Amount of heat needed to raise the temperature of a unit mass by one degree.
Heat Content (OHC): Integrated heat stored in a water column, often expressed for the upper 700 or 2000 meters.
Heinrich Event: Past episodes of massive iceberg discharge into the North Atlantic.
Hindcast: Model reconstruction of past conditions using observed forcing.
Horse Latitudes: Subtropical high-pressure belts near 30 degrees latitude with calm winds.
Humboldt Current: Cold eastern boundary current along the west coast of South America.
Hurricane Heat Potential: Integrated upper-ocean heat content above 26 degrees Celsius.
Hydrography: Science of surveying water bodies.
Hydrostatic Pressure: Pressure at depth due to the weight of overlying water.

I

Indian Ocean Dipole (IOD): Coupled ocean-atmosphere mode with SST anomalies across the tropical Indian Ocean.
Indonesian Throughflow (ITF): Flow of Pacific water to the Indian Ocean through the Indonesian archipelago.
Inertial Oscillation: Free oscillation of a water parcel with period 2 pi divided by the Coriolis parameter.
Internal Tide: Internal wave generated at tidal frequencies by tide-topography interactions.
Internal Wave: Wave propagating within a stratified fluid along density interfaces.
Intertropical Convergence Zone (ITCZ): Belt of low pressure near the equator where trade winds converge.
IOC-UNESCO: Intergovernmental Oceanographic Commission of UNESCO, coordinating ocean science globally.
Iridium SBD: Short Burst Data telemetry widely used to relay oceanographic data.
Iron Fertilization: Addition of iron to surface waters to stimulate phytoplankton growth.
Isobar: Line of equal atmospheric pressure on synoptic chart.
Isohaline: Line of constant salinity.
Isopycnal: Surface of constant potential density.
Isotherm: Line of constant temperature.

J

Jet Stream: Narrow band of strong upper-tropospheric winds.
Joint Numerical Weather Prediction: Operational meteorological forecasting using coupled models.
JONSWAP spectrum: Joint North Sea Wave Project spectral form.

K

Kelvin Wave: Trapped wave that propagates along a boundary or the equator without dispersion.
Kuroshio Current: Warm western boundary current of the North Pacific off Japan.

L

La Nina: Cool phase of ENSO with enhanced trade winds and cooler eastern equatorial Pacific.
Labrador Sea Water: Intermediate water mass formed by deep convection in the Labrador Sea.
Lagrangian Measurement: Observation following a moving water parcel.
Langmuir Circulation: Wind-driven helical roll cells in the surface mixed layer.
Latent Heat Flux: Heat exchanged with the atmosphere through evaporation or condensation.
Length of Day Variation: Small fluctuations linked partly to atmospheric and oceanic angular momentum.
Liquid Water Path: Vertically integrated cloud liquid water content.

M

Madden-Julian Oscillation (MJO): Eastward propagating mode of tropical convection and circulation.
Marine Boundary Layer: Atmospheric boundary layer over the ocean.
Marine Heatwave (MHW): Persistent anomalously warm sea surface temperature event.
Mediterranean Outflow Water: Saline water exiting the Mediterranean through the Strait of Gibraltar.
Meridional Overturning Circulation: Zonally integrated north-south circulation in an ocean basin.
Mesoscale Eddy: Coherent rotating ocean feature with scales of tens to hundreds of kilometers.
Microstructure Profiler: Instrument measuring small-scale temperature and shear used to estimate mixing.
Mid-Atlantic Bight: Continental shelf region from Cape Cod to Cape Hatteras with distinctive water masses.
Mixed Layer: Near-surface layer of nearly uniform temperature and salinity due to turbulent mixing.
Mixed Layer Depth (MLD): Depth marking the base of the surface mixed layer.
Moored Buoy: Anchored platform providing continuous meteorological and oceanographic measurements.
Munk Boundary Layer: Western boundary layer in wind-driven ocean models including lateral friction.

N

Nansen Bottle: Classical water sampler used before electronic CTDs.
NEMO: Nucleus for European Modelling of the Ocean, a widely used ocean general circulation model.
Nepheloid Layer: Bottom layer with elevated suspended sediment concentrations.
Net Heat Flux: Sum of shortwave, longwave, sensible, and latent heat fluxes at the sea surface.
NOAA: National Oceanic and Atmospheric Administration of the United States.
North Atlantic Deep Water (NADW): Cold, dense water mass formed in the northern North Atlantic.
North Atlantic Oscillation (NAO): Climate mode based on the pressure difference between Iceland and the Azores.
Nutricline: Vertical layer with strong nutrient concentration gradient.

O

Oceanic Mixed Layer Depth Climatology: Reference datasets such as de Boyer Montegut compilations.
Oceanographic Atlas: Compilation of climatological ocean properties, such as the World Ocean Atlas.
OISST: NOAA Optimum Interpolation Sea Surface Temperature product.
OSCAR: Ocean Surface Current Analyses Real-time product.
Oxygen Minimum Zone (OMZ): Mid-depth layer with very low dissolved oxygen concentrations.
Oxygen Solubility: Maximum dissolved O2 concentration at saturation, decreasing with temperature and salinity.

P

Pacific Decadal Oscillation (PDO): Long-lived ENSO-like pattern of Pacific climate variability.
Partial Pressure of CO2 (pCO2): Pressure that CO2 in seawater would exert in equilibrium with the gas phase.
Peru Current: Cold current along the Peruvian coast, part of the Humboldt system.
pH: Negative logarithm of hydrogen ion activity, central to ocean acidification studies.
Photosynthetically Active Radiation (PAR): Spectral range driving photosynthesis, 400 to 700 nanometers.
Pielou Index: Evenness measure used in ecology and applicable to marine community studies.
Planetary Boundary Layer: Atmospheric layer directly affected by Earth's surface.
Polar Front: Boundary between polar and subpolar water or air masses.
Polar Vortex: Persistent large-scale low pressure circulation in the polar stratosphere or troposphere.
Potential Density: Density a water parcel would have if brought adiabatically to a reference pressure.
Potential Temperature: Temperature a parcel would have if moved adiabatically to a reference pressure.
Practical Salinity Scale 1978 (PSS-78): Salinity standard based on conductivity ratios.
Precipitable Water: Total atmospheric water vapor in a vertical column.
Primary Production: Rate of synthesis of organic matter by photosynthesis or chemosynthesis.
Pycnocline: Vertical layer with rapid density change.

Q

QBO: Quasi-Biennial Oscillation in tropical stratospheric winds.
Quasi-Geostrophic Theory: Approximation describing slowly varying, balanced motions in rotating stratified fluids.

R

Radiation Budget: Net difference between incoming and outgoing radiation at a surface.
Rain Rate: Precipitation intensity, often measured at sea by disdrometers or satellites.
Reanalysis: Consistent reconstruction of atmospheric or oceanic state using data assimilation.
Relative Humidity: Ratio of actual to saturation water vapor pressure.
Residual Circulation: Mean flow remaining after removing tidal and wind-driven variability.
Return Flow: Compensating subsurface flow that closes a surface transport.
Reverse Estuarine Circulation: Outflow at depth and inflow at surface in evaporation-dominated basins.
Reynolds Number: Dimensionless ratio of inertial to viscous forces.
Richardson Number: Ratio of buoyancy to shear, used to assess turbulence onset.
Rio Mean Dynamic Topography: CNES-CLS product of mean dynamic ocean topography.
Rip Current: Strong narrow seaward flow through the surf zone.
Roaring Forties: Strong westerly winds between 40 and 50 degrees south.
Rossby Number: Ratio of inertial to Coriolis forces.
Rossby Wave: Large-scale wave owing its existence to the variation of Coriolis with latitude.

S

Salinity: Concentration of dissolved salts in seawater, dimensionless on PSS-78.
Saltwater Intrusion: Encroachment of saline water into freshwater systems.
Sargasso Sea: Region of the North Atlantic bounded by ocean currents and famous for Sargassum mats.
Saturation Vapor Pressure: Equilibrium vapor pressure of water at a given temperature.
Schmidt Number: Ratio of kinematic viscosity to molecular diffusivity, used in gas transfer.
SCOR: Scientific Committee on Oceanic Research, an ICSU body coordinating ocean science.
Sea Breeze: Onshore wind driven by differential daytime heating of land and sea.
Sea Ice Concentration: Fractional area covered by sea ice within a region.
Sea Level Pressure (SLP): Atmospheric pressure reduced to mean sea level.
Sea State: Description of the wave field, characterized by significant wave height and period.
Sea Surface Height (SSH): Elevation of the sea surface relative to a reference, typically measured by altimetry.
Sea Surface Salinity (SSS): Salinity of the upper few meters of the ocean.
Sea Surface Temperature (SST): Temperature of the upper few meters of the ocean.
Secchi Depth: Depth at which a Secchi disk disappears from view, indicating water transparency.
Seiche: Standing wave in a partially enclosed body of water.
Sensible Heat Flux: Heat exchanged between sea and atmosphere by conduction and turbulence.
Shallow Water Wave: Wave whose wavelength is much greater than water depth.
Sigma-t: Density of seawater at atmospheric pressure minus 1,000 kg per cubic meter.
Significant wave height (Hs): Mean of highest one-third wave heights.
Sloan Foundation Argo Support: Funding instances supporting biogeochemical Argo expansion.
Solar Constant: Mean solar irradiance at the top of the atmosphere, about 1361 watts per square meter.
South Atlantic Anomaly: Region of weakened geomagnetic field complicating some satellite measurements.
Southern Annular Mode (SAM): Mode of variability of westerly winds around Antarctica.
Southern Ocean: Ocean encircling Antarctica, generally south of 60 degrees south.
Specific Heat of Seawater: Heat required to raise temperature of one kilogram of seawater by one degree.
Squall Line: Line of thunderstorms associated with a cold front or mesoscale system.
Steric Sea Level: Change in sea level due to thermal expansion and salinity changes.
Stokes Drift: Net Lagrangian drift due to surface wave orbital motion.
Stratus: Layered low-level cloud common over the marine boundary layer.
Subantarctic Mode Water (SAMW): Thick, weakly stratified water mass formed in the Subantarctic Front region.
Subduction: Process by which surface water enters the ocean interior along isopycnals.
Subtropical Gyre: Large rotating circulation in subtropical ocean basins.
Sverdrup (Sv): Unit of volume transport equal to one million cubic meters per second.
Sverdrup Balance: Wind-driven interior flow balance between meridional transport and wind stress curl.

T

Teleconnection: Climate linkage between distant regions through atmospheric or oceanic mechanisms.
TEOS-10: Thermodynamic Equation of Seawater 2010, the international standard for seawater thermodynamics.
Tethered Profiler: Instrument that profiles up and down a mooring wire.
Thermal Inertia: Resistance of a material such as the ocean mixed layer to temperature change.
Thermocline: Vertical zone with rapid temperature change in the upper ocean.
Thermohaline Circulation: Density-driven global ocean overturning circulation.
Tidal Mixing: Mixing caused by interaction of tidal currents with topography.
Total Alkalinity (TA): Excess of proton acceptors over proton donors in seawater.
Trade Winds: Persistent easterly winds in the tropics.
Transient Tracer: Anthropogenic substance such as CFC-11 used to date water masses.
Tropical Cyclone: Warm-core low pressure system originating over tropical oceans.
Tropopause: Boundary between the troposphere and stratosphere.
Turbulent Kinetic Energy (TKE): Kinetic energy associated with turbulent eddies.

U

Underway Sampling: Continuous shipboard observation of surface seawater properties.
Universal Time Coordinated (UTC): Reference timescale for navigation.
Upwelling: Coastal current rising cold water, relevant in weather routing.
Upwelling Index: Bakun and related indices quantifying coastal upwelling intensity.

V

Variable Wind Coast: Coastline where winds vary widely on synoptic timescales.
Vertical Velocity (w): Component of velocity perpendicular to the horizontal plane.
Virtual Salt Flux: Equivalent salt flux representing freshwater input in rigid-lid models.
Vorticity: Curl of the velocity field, measuring local rotation.

W

Walker Circulation: Zonal atmospheric overturning over the tropical Pacific linked to ENSO.
Water Mass: Body of water with distinctive temperature, salinity, and chemistry.
Wave Age: Ratio of wave phase speed to wind speed.
Wave Setup: Increase in mean water level near shore due to wave momentum flux.
Weddell Sea Polynya: Recurrent open-water area within Antarctic sea ice.

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