Glossary

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Page ID: 31542

W. Sean Chamberlin, Nicki Shaw, and Martha Rich
Fullerton College via Blue Planet Publishing

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Words (or words that have the same definition)	The definition is case sensitive	(Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages]	(Optional) Caption for Image	(Optional) External or Internal Link	(Optional) Source for Definition
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Glossary Entries
Word(s)	Definition	Image	Caption	Link	Source
macronutrient	a biologically important nutrient required in high concentrations.
Madden–Julian Oscillation	an intraseasonal, eastward-traveling, globe-trotting atmospheric wave that influences weather.
magma	molten rock beneath Earth’s surface.
major constituent	an element whose concentration exceeds 1 part per million in seawater.
Malvinas Current	a cold, northward-flowing current off the coasts of Uruguay and Argentina.
manganese nodule	See polymetallic nodule.
manipulator arm	human-controlled, mechanical extension on an ROV for collecting samples, drilling holes, or deploying instruments in the ocean.
marine big data	the enormous volumes of oceanographic data now available and growing daily.
marine geomorphometry	the quantitative study of the seafloor.
marine layer	a low-altitude cover of stratus clouds that forms over a cool ocean.
marine phosphorite	a phosphate-rich sedimentary rock formed in oceanic upwelling regions with high biological productivity.
marine virus	a noncellular entity inhabiting the ocean with a protein shell that encapsulates genetic information.
mass extinction	a rapid and global decrease in the abundance and diversity of organisms.
matground	surface crust formed as a result of interactions between microbes and sediments.
mathematical models	simple or complex mathematical expressions or sets of expressions to describe or simulate how something works.
mean sea level	the average sea level.
mega-evaporite	enormous deposit of salt formed by evaporation of seawater trapped during uplift of extensive ocean basins.
megacity	a city whose population exceeds 10 million people.
meltwater	water that originates from frozen sources.
membrane-based desalination	a process that uses membranes to produce freshwater.
meridional current	a current flowing along a line of longitude.
meridional overturning circulation	the combined three-dimensional surface and deep circulation of the ocean; see also world ocean circulation.
mesopelagic zone	a zone characterized by dim and diffuse light, extending from the bottom of the euphotic zone to approximately 1,000 meters.
mesophotic coral ecosystems	coral reefs that grow in dimly lit waters.
mesoscale	distances on the order of a few to a hundred kilometers.
mesoscale structure	the regional scale of physical, chemical, or biological features of the ocean, from a few to a few hundred miles.
mesosphere	the layer above the stratosphere in the middle of Earth’s atmospheric layers, where meteors become visible as they are heated through friction.
metamorphic rock	a rock transformed by heat, pressure, and fluids.
metazoan	true animals; multicellular animals with differentiated cells.
meteorology	the scientific study of the atmosphere.
methane	a molecule composed of one carbon and four hydrogen atoms that acts as a greenhouse gas in Earth’s atmosphere.
methane hydrate	a frozen form of methane found on the seafloor.
methanogen	a type of microbe that converts organic matter into methane.
metric system	See International System of Units.
microbial mat	a carpet of photosynthetic and sediment-dwelling bacteria.
microfossil	the hardened remains of a microscopic organism.
microlayer	the lower part of the sea surface microlayer, inhabited by a unique assemblage of microbes and various abiogenic and biogenic particles, found from 1 to 1,000 micrometers in depth.
micronutrient	a biologically important nutrient required in low concentrations.
microwave	electromagnetic radiation with wavelengths between 1 millimeter and a meter.
middle intertidal	in the North American West Coast littoral classification system, the second zone (Zone 2), occupying the region at tide heights of zero to 1.5 meters.
midnight zone	See bathypelagic zone.
Milky Way	the galaxy in which Earth resides.
Mindanao Current	the southward flow of the North Equatorial Current at its western terminus.
mineral	a solid of inorganic material with a unique chemical composition and crystalline structure.
mini-autonomous underwater explorer	small, autonomous, sensor- and GPS-enabled platform that works in a swarm beneath the surface of the ocean to track currents or carry out other kinds of observations and measurements.
minor constituent	an element whose concentration in seawater is less than 1 part per million.
minus tide	a tide whose tide height is less than zero.
mitochondria	the cell structure that supplies energy to eukaryotic cells.
mixed layer depth	the depth to which the surface mixed layer extends, usually the top of the thermocline.
mixed semidiurnal tide	a twice-daily tide with unequal heights.
mixed tide	See mixed semidiurnal tide.
mixed-type distribution	the existence of different distributions of a trace element in seawater depending on its form.
mixground	a slurry of soft seafloor sediments formed by the activities of organisms.
mixing	the homogenization of seawater.
mixture	a collection of molecules with an indefinite or varying composition, such as air or seawater.
molecule	two or more atoms bound together.
Mollusca	a phylum that includes bivalves, gastropods, chitons, and cephalopods.
molting	the shedding of an exoskeleton by an organism.
momentum	the product of a molecule’s mass and its velocity.
momentum transfer	the transfer of momentum from a moving molecule to a nonmoving molecule.
monophyletic	descending from a common ancestor.
monsoon	the wind that arises from seasonal heating of the interior of continental regions.
Mount Erebus	the world’s southernmost active volcano.
Mount Everest	the highest mountain on Earth.
mouth (of river or watershed)	the lowermost elevation of a river; where it ends.
moving water	flow of water.
multicellular organism	an organism with many different specialized cells which carry out specific functions and cannot independently create a whole organism.
multiple thermocline	the presence of two or more thermoclines in a water column.
multispectral imager	sensor capable of detecting multiple wide bands of electromagnetic radiation.
mystery zone	See abyssopelagic zone.
nanolayer	the thin organic coating at the very surface of the ocean, from zero to 1 micrometer in depth.
National Tidal Datum Epoch	a 19-year average of low or low low tide heights used to establish that tidal datum at different locations around the US.
natural gas hydrate	a potential source of energy found in great quantities on the seafloor.
neap tide	a tide of minimum range occurring at the first and the third quarters of the Moon.
near-bottom zone	See benthopelagic zone.
negative buoyancy	the tendency of a fluid or object to sink in a fluid.
negative feedback loop	a process that acts to maintain, reduce, or reverse changes in a system.
negative tide	See minus tide.
nekton	organisms that propel themselves through the water column.
Neoproterozoic Oxygenation Event	a period of increase in atmospheric oxygen sufficient to oxygenate at least some deep ocean basins around 570 million years ago.
neritic waters	See coastal waters.
neutrally buoyant	the tendency of a fluid or object to remain at rest in a fluid.
neutron	a neutrally charged subatomic particle found in the nucleus of an atom.
new Moon	when the side of the Moon facing Earth is not visible.
night vision technology	devices that detect infrared radiation and permit viewing of objects in the dark.
Niskin bottle	a type of seawater sampling bottle that can be triggered electronically.
nitrogen-fixing bacteria	microbes capable of turning nitrogen gas into biologically available forms of nitrogen.
nitrous oxide	a molecule composed of nitrogen and oxygen produced naturally by microbial activity; acts as a greenhouse gas in Earth’s atmosphere.
nondispersive	waves that do not separate according to their wavelength or wave period.
noon sun angle	the angle of the Sun above the equatorward horizon at noon.
North America	the third-largest continent.
North Atlantic Current	the eastward-flowing west wind drift current in the North Atlantic Ocean.
North Atlantic Gyre	the subtropical gyre circulation in the North Atlantic Ocean.
North Equatorial Countercurrent	a west-to-east current just north of the equator.
North Equatorial Current	the equatorial current that flows just north of the equator.
North Pacific Current	the eastward-flowing west wind drift current in the North Pacific Ocean.
North Pacific Gyre	the subtropical gyre circulation in the North Pacific Ocean.
North South Equatorial Current	the northerly branch of the South Equatorial Current in the Atlantic Ocean.
Northeast Monsoon Current	the westward-flowing current that occurs during the winter monsoon.
northeast trade wind	the trade wind that blows from northeast to southwest north of the equator.
Norwegian Current	a northerly current along the coast of Norway.
nowcast	forecast of ocean or atmospheric conditions in near real time.
nucleus (in biology)	the cell structure in which most of a cell’s genetic material is housed.
nucleus (in chemistry)	the central portion of an atom, composed of protons and neutrons.
nuisance flooding	local flooding caused by sea level rise that now occurs at high tides.
numerical models	computer models that solve sets of mathematical equations to make forecasts or projections of natural processes at some time in the future.
nutrient	See biologically important nutrient.
obligate anaerobe	an organism that cannot tolerate oxygen in its environment.
ocean basin	a depression in Earth’s crust covered by seawater extending from the shelf break to the deepest trench.
ocean climate	the average of ocean conditions over a specified period of time.
ocean color	the colors of visible light emanating from the surface of the ocean.
ocean depth zone	a system for classifying the general conditions for organisms present at various depth ranges in the water column and on the seafloor.
ocean eddy	a self-sustaining, rotating loop of water tens to hundreds of miles wide.
ocean heat content	the heat stored in the ocean.
ocean life zone	See ocean depth zone.
ocean mining	the extraction of mineral resources from the seafloor.
ocean mooring	seafloor-anchored cable on which various ocean sensors can be attached and held vertically by a float.
ocean observatory	an integrated array of ocean-observing sensors and platforms on and above the seafloor designed to address questions of scientific and societal importance.
ocean tide	the daily rising and falling of sea level.
ocean tracer	a substance used to track the movement and evolution of water masses.
ocean wave	the physical expression of energy moving forward at the interface between two fluids of different density, including surface and internal waves.
ocean weather	the instantaneous state of the ocean.
ocean-observing systems	a broad category of sensor-outfitted platforms that fly above, glide on top of, or dive below the surface of the ocean.
oceangoing investigation	a scientific investigation carried out at sea.
oceanic crust	the part of Earth’s crust that forms the ocean basins.
oceanic gyre	the rotation of currents around a common center in an ocean basin.
oceanic plateau	flat or nearly flat region of the seafloor that drops off abruptly on one or more sides.
oceanic ridge	a narrow region of varying complexity whose height exceeds 1,000 meters and whose length-to-width ratio is greater than 2.
oceanic trench	a V-shaped depression in the seafloor with steep walls.
oceanic waters	waters overlying the ocean basins.
oceanographer	any person, robot, or animal engaged in the scientific study of the ocean.
oceanography	the scientific study of the world ocean.
offshore	the region beyond the surf zone.
offshore wind	a wind that blows from the land to the ocean.
onshore wind	a wind the blows from the ocean to the land.
ooid	light-colored oval of calcium carbonate.
Oort Cloud	a spherical-shaped system of dust, icy objects, and comets at the far reaches of our solar system.
open ocean oceanography	See blue water oceanography.
open ocean	the oceanic waters beyond the continental shelves.
operational oceanography	the acquisition and dissemination of oceanographic and meteorological information useful to navigating or carrying out activities in the ocean.
orbital plane	the imaginary horizontal plane on which Earth orbits the Sun.
ordinal direction	northeast, southeast, northwest, southwest.
ordinary gravity wave	waves with periods from 1 to 30 seconds.
Ordovician	a geologic period from 485.4 to 443.8 million years ago.
organelle	a subcellular, specialized structure present in eukaryotes and possibly Archaea and bacteria.
oxygen minimum zone	a region of reduced or absent dissolved oxygen in the water column.
oxygenic photosynthesis	photosynthesis that yields oxygen as a by-product.
Oyashio Current	a southward-flowing current off the island of Hokkaido, Japan.
ozone hole	a region where stratospheric ozone concentrations are greatly reduced.
ozone layer	the part of the stratosphere containing ozone.
Pacific Ocean	the largest ocean in the world.
pale blue dot	the name given to the blue speck of Earth as seen from millions of miles away in outer space.
paleoshoreline	an ancient shoreline formed during lowstands of sea level.
Pangea	a supercontinent that formed and broke apart over an interval from 320 to 195 million years ago.
paraphyletic	not including all descendants of a common ancestor.
parent rock	the source material for sediments.
particulate organic carbon	anything living or once living that occurs as a particle in seawater.
particulate organic matter	living and dead particles of organic matter.
passive microwave sensor	sensor that measures the intensity of microwave radiation emanating from Earth’s land, ice, and sea surface.
passive sensor	sensor that measures the electromagnetic properties of the ocean.
peer review	the process whereby scientists receive feedback on their work by other scientists and experts.
pelagic depth zones	ocean depth zones within the water column from the surface to the deepest trenches.
pelagic organism	organism that inhabits the water column.
perihelion	the point in Earth’s slightly elliptical orbit where its distance from the Sun is smallest.
periodic table of elements	a chart depicting all of the known elements.
Periodic Table of the Elements in the Ocean	an online chart of the elements found in seawater and their concentrations with depth in the ocean.
permanent thermocline	the boundary between polar water masses and seasonally mixed water masses.
Peru Current	See Peru–Chile Current.
Peru–Chile Current	the equatorward-flowing eastern boundary current in the South Pacific Ocean.
Pettersson–Nansen bottle	a type of sampling bottle for obtaining seawater at depth.
Phaeophyta	a phylum that includes multicellular brown algae.
Phanerozoic	the eon of visible life from 541 million years ago to the present.
photic zone	the lighted waters of the upper ocean.
photoautotroph	an organism that uses light to manufacture its own food.
photophore	the light organ of bioluminescent animals.
photosynthesis	the manufacture of organic carbon from carbon dioxide and inorganic substances using energy obtained from sunlight.
photosynthetically available radiation	the wavelengths of visible light that stimulate photosynthesis in plants, generally from 400 to 700 nanometers.
phylogenetic tree	a branching diagram that illustrates the hypothetical evolutionary relationships between organisms.
physical model	a scaled-down, three-dimensional, semirealistic representation of a physical object or part of nature.
physical oceanography	the scientific study of the physical properties and processes in the world ocean.
physical state	the state of matter: solid, liquid, or gas.
physical weathering	the breakdown of rocks by physical processes.
physisorption	the physical attraction of elements to particles.
phytoplankton	photosynthetic microbes that drift with the currents in the sunlit waters of the ocean.
phytoplankton thin layer	narrow layer with high concentrations of phytoplankton.
pillow basalt	a basaltic rock formation that resembles pillows.
Pineapple Express	the popular name given to the subtropical jet stream when it carries humid subtropical air from Hawaii to California.
plasma	a fourth state of matter consisting of free-moving electrons and ions.
plunging breaker	wave that creates a tube with a lip that shoots over the face of the wave in a kind of waterfall.
plus tide	a tide whose height is greater than zero.
point break	a type of breaking wave that wraps around a headland.
polar cell	the atmospheric cell that occurs over polar regions.
polar day	the six-month period of continual or near-continual sunlight in polar regions.
polar easterlies	the easterly directed prevailing winds that blow at polar latitudes.
polar gyre	a gyre circulation at polar latitudes.
polar jet stream	a high-altitude flow of cold air that meanders like a river around the North and South Poles.
polar molecule	a molecule that exhibits a separation of charges.
polar night	the six-month period of continual or near-continual darkness in polar regions.
polar submarine canyon	submarine canyon found on Arctic and Antarctic continental shelves.
polar zone	region north of the Arctic Circle or south of the Antarctic Circle characterized by freezing weather.
polychaete	a segmented marine worm with bristles.
polymetallic crust	similar to nodules in composition, forming as a coating on rocks along the flanks and summits of seamounts.
polymetallic nodule	tennis ball–sized globe of different metals that precipitates slowly around a nucleus (a shell or bone fragment, for example) on the seafloor.
poorly sorted	having grain sizes that vary widely.
Porifera	a phylum that includes sponges.
positive buoyancy	the tendency of a fluid or object to rise in a fluid.
positive feedback loop	a process that acts to amplify or accelerate changes in a system.
positive tide	See plus tide.
potential energy	stored energy or energy inherent in an object in a gravitational field.
practical salinity scale	a unitless scale used to define salinity.
precipitation	the gravity-driven falling of liquid or solid water from the atmosphere.
pressure gradient force	the force that arises when two locations have different air pressure.
pressure	the force exerted by a fluid (a gas or a liquid) on an object immersed within it.
principle of constant proportions	the observation of constant proportions among the major constituents of seawater.
principle of unity	the idea that there is but one ocean on Earth, the world ocean.
progressive wave	a wave moving forward along a density boundary.
prokaryote	a cell lacking a visible nucleus and other organelles.
Proterozoic	the eon of early life, from 2.5 billion to 541 million years ago.
protist	a single-celled or multicellular species with a eukaryotic cell type.
proton	a positively charged subatomic particle found in the nucleus of an atom.
protostar	the earliest stage in the evolution of a star.
qualitative	data described by its properties or relationships with other variables.
quantitative	numerical data that can be analyzed mathematically.
quartz	a white or clear mineral composed of silica found as grains in beach sand.
radial component	the vertical component of the tidal force.
radial symmetry	a shape arranged around a central axis, like a cake or pie.
radiation	the transfer of heat via electromagnetic energy.
radio wave	the longest wavelength of radiation in the electromagnetic spectrum, by which analog radio is transmitted.
radiometer	sensor that detects electromagnetic radiation.
ray	the path of a beam of light.
recirculation gyre	a regional gyre-type flow that recirculates water along a western boundary current.
reference ellipsoid	the best-fit ellipsoid to Earth’s geoid.
reflection	the rebound of a light ray at the same angle at which it strikes an object.
regional cabled array	seafloor-based ocean observatory spanning a region of geologic interest.
relative sea level rise	the increase in local mean sea level measured at a particular location.
relief	the change in height of a seafloor feature from its highest to lowest point.
remotely operated vehicle	human-controlled, camera-equipped, propelled vehicle attached to a shipboard tether for gathering images, making measurements, or collecting samples from the water column or seafloor.
reservoir	a place where something is stored.
reservoir model	a conceptual (or mathematical) model identifying (and quantifying) the sources and sinks of substances to a reservoir.
residence time	the time an element spends in a reservoir like the ocean.
respiration	the metabolic breakdown of organic matter.
restoring force	a force that restores sea level.
reverse osmosis system	the movement of water across a concentration gradient.
reversing thermometer	a type of oceangoing thermometer that turns upside down when triggered at depth to obtain an accurate measure of temperature.
Rhodophyta	a phylum that includes single-celled and multicellular red algae
rill	a treelike pattern of sand formed when water seeps from a beach exposed during a low tide.
ring	a type of mesoscale eddy that forms in association with western boundary currents.
ripple	wind waves larger than capillary waves and smaller than wind chop.
robotic investigation	a scientific investigation that employs robotic devices to make observations and measurements of the natural world or under artificially created conditions.
rocks	aggregates of minerals
rock cycle	the transformations of one rock type to another.
rock tumbler	a device used to polish small rocks.
rockslide	the tumbling of rocks downhill.
rocky intertidal zone	the region bounded by the highest and lowest tides.
rocky planet	a planet whose composition is predominantly solid materials.
Rodinia	the second supercontinent, appearing about a billion years ago.
rolling	the tumbling of a sediment grain in the direction of fluid flow.
rooted tree	a phylogenetic tree with a main trunk and branches depicting ancestry among species.
rosette	a circular arrangement of sampling bottles attached to a CTD.
Ross Gyre	a polar gyre in the Ross Sea.
Rossby wave	a large-scale, wavelike motion of the upper troposphere, often associated with the polar jet stream.
runnel	a strip of shallow water parallel to the beach on the seaward side of the beach face.
Sahara Desert	the world’s largest hot desert.
saildrone	a wind-propelled, solar-powered surfboard to which instruments may be attached for gathering oceanographic and meteorological information.
salinity	the concentration of dissolved salts in seawater.
salinometer	an electronic device used to measure salinity.
salt	a general term applied to all dissolved substances found in seawater.
saltation	the hopping of a sediment grain in a fluid flow.
sand mining	the removal of sand from beaches or the seafloor by commercial enterprises.
sandbar	a shallow, usually submerged, accumulation of sand on the seaward side of the beach face.
Santa Ana wind	an episodic, often intense, offshore wind that occurs in Southern California and Northern Baja California.
satellite altimeter	an active microwave sensor used to determine the bumps and depressions of the sea surface.
satellite oceanography	the use of Earth-orbiting satellites to make observations and collect data on ocean features and processes.
satellite product	any of a number of computed variables derived from measurements using satellites.
saturation concentration	the maximum concentration of a solute that can be dissolved by a solution under a given set of conditions.
scattering	the change in direction of a light ray as it interacts with an object.
scavenging	the removal of trace elements by sinking particles.
science communication	the widespread and transparent dissemination of scientific knowledge and understanding, especially in a manner accessible to the public.
science literacy	the knowledge and understanding of science required to participate meaningfully in personal and societal discussions and decisions that use science.
scientific discussion	the presentation in oral or written form of the conclusions of a particular scientific study.
scientific diving	the use of scuba diving to carry out scientific investigations underwater.
scientific inquiry	a general term to describe the diverse approaches scientists use to investigate the natural world.
scientific method	the systematic and self-correcting set of practices that scientists use to discover knowledge about the natural world.
scientific name	the standardized name given to all scientifically described species.
scientific question	a well-formed question that lends itself to investigation using the scientific method.
scuba	an acronym for self-contained underwater breathing apparatus.
sea bean	any of a number of tropical seeds transported by ocean currents to faraway beaches.
sea breeze	an onshore wind generated by temperature differences between the land and ocean.
sea level	the theoretical height of the ocean at rest.
sea surface height	the elevation of the sea surface relative to Earth’s geoid—the bumps and depressions of the sea surface.
sea surface microlayer	the top 1 millimeter of seawater at the surface of the ocean.
sea surface salinity	the concentration of dissolved salts at the surface of the ocean.
sea surface temperature	the temperature of the surface skin of the ocean.
sea surface	the ever-changing upper boundary of the ocean.
sea surface topography	the shape of the sea surface.
seafloor feature	part of the seafloor with measurable relief or delimited by such a feature.
seafloor massive sulfide deposit	the sulfur-rich chimneys and deposits of hydrothermal vents.
seafloor province	region of the seafloor bounded by recognizable features produced as a result of geologic processes.
seafloor	the part of Earth’s crust submerged beneath the ocean.
seamount	an isolated underwater mountain with a relief greater than 1,000 meters.
season	the changes in sunlight that occur as a result of Earth’s orbit around the Sun.
seasonal thermocline	the thermocline that appears during surface warming and disappears during surface cooling over the course of a year.
seawater parcel	an oceanographer’s term for an unspecified volume of seawater.
sediment	solid particles of various sizes fragmented from rocks.
sediment transport	the movement of sediments over space and time.
sediment trap	device that collects and stores sinking particles
sedimentary rock	a rock formed from fragmentation and consolidation of other rock types.
sedimentologist	a scientist who studies sediments.
semidiurnal tide	a twice-daily tide with near-equal heights.
semipermeable membrane	a filter the separates salts from water.
sensible heat	heat that can be detected by human senses or instruments.
shallow-water wave	a wave that travels in water shallower than one twentieth its wavelength.
shark cage	a metal cage that permits safe viewing of sharks and other pelagic ocean species.
shelf break	the place on the continental shelf where the slope of the seafloor increases sharply.
ship of opportunity	private, commercial, or nongovernmental ship enlisted to take oceanographic and meteorological measurements on its voyage.
shortwave radiation	collectively, the portion of the electromagnetic spectrum that includes ultraviolet, visible, and near-infrared wavelengths.
SI units	See International System of Units.
sidereal month	the time it takes the Moon to complete one orbit around the Earth.
sine wave	a geometric pattern that resembles the shape of a wave.
sink	a process that decreases the mass or volume of a reservoir.
skeleton	any framework that provides support, shape, or protection to an organism.
Skeleton Coast	the name given to the coast of Namibia where shipwrecks and the skeletons of marine animals are abundant.
snailfish	the deepest known vertebrate
Snowball Earth	a period of time when Earth was entirely or mostly covered in glaciers and ice.
sodium chloride	the most common salt in seawater.
sodium ion	the ionic form of sodium.
solar path	the path of the Sun across the sky.
solar system	the name for the system of celestial bodies orbiting the Sun
solar wind	the steady stream of charged particles from the Sun.
solid	a substance that maintains its own form.
solstice	the time of year when the Sun is at its highest or lowest point in the sky.
solute	the substance being dissolved in a solution.
solvent	a substance that dissolves another substance.
sorting	the separation of sediment grains by size in a fluid flow.
source	a process that increases the mass or volume of a reservoir.
South America	the fourth-largest continent.
South Atlantic Current	the eastward-flowing west wind drift current in the South Atlantic Ocean.
South Atlantic Gyre	the subtropical gyre circulation in the South Atlantic Ocean.
South Equatorial Current	the equatorial current that flows just south of the equator.
South Indian Current	the eastward-flowing west wind drift current in the South Indian Ocean.
South Indian Gyre	the subtropical gyre circulation in the South Indian Ocean.
South Pacific Current	the eastward-flowing west wind drift current in the South Pacific Ocean.
South Pacific Gyre	the subtropical gyre circulation in the South Pacific Ocean.
southeast trade wind	the trade wind that blows from southeast to northwest south of the equator.
Southern California Continental Borderland	an offshore expanse of submarine canyons, sea valleys, and ocean basins adjacent to Southern California from Point Conception to the US–Mexico border.
Southern Ocean	the wheel-shaped ocean surrounding Antarctica.
Southwest Monsoon Current	the eastward-flowing current that occurs during the summer monsoon.
space weather	solar activity that may disrupt human activities and technology.
spaceborne investigation	a scientific investigation that employs sensors aboard Earth-orbiting platforms to make observations and obtain measurements of Earth’s surface.
spatial resolution	relating to units of space (distance, area, volume).
speciation	the presence of multiple forms of a trace element in seawater.
species	a group of individuals that share near-identical genetic code and can produce fertile offspring with each other.
specific gravity	the density of a substance divided by the density of water.
specific heat	the heat required to change the temperature of 1 gram of a substance by one degree.
spicule	needle of calcium carbonate or silica in the skeleton of a sponge.
spilling breaker	a wave whose lip trickles down the front of the wave.
splash zone	a subdivision of the littoral zone; the upper limit of marine life, characterized by occasional wetting from strong waves and extremely high tides.
spongin	a fibrous network of protein in sponges.
spreading loss	the decrease in energy along a wave front as it expands.
spring equinox	the time of year when daylength is increasing and the Sun is passing directly over the equator into the opposite hemisphere.
spring tide	the periods in a month when tidal range is greatest.
St. Elmo’s fire	an electrical discharge from the masts of ships.
stable water column	a water column whose layers increase in density from the surface to the bottom.
standard seawater	seawater used to calibrate instruments that measure salinity.
standing wave	a wave that appears to sand still.
star classification	an alphanumeric system for describing the characteristics of a star.
steerable stratospheric balloon	a high-altitude balloon capable of staying aloft for long periods of time.
still water level	the surface of the ocean in the absence of disturbing forces.
stratification	the layering of the water column due to surface heating.
stratosphere	the atmospheric layer above the troposphere.
stromatolite	layered rock structure created in shallow waters out of fine sediments trapped by filamentous cyanobacteria.
subatomic particle	one of the constituent parts of an atom.
sublittoral zone	the region from the zero tide height to the shelf break.
submarine	a human-occupied vessel capable of propelling itself underwater and remaining submerged for long periods of time.
submarine canyon	a steep-sided underwater valley whose shallow end comes close to shore.
submersible	a small submarine capable of reaching the deepest depths of the ocean.
submersion	when an organism or object is covered by seawater.
subpolar gyre	a gyre circulation in the vicinity of the Arctic and Antarctic Circles.
subseafloor environment	a region extending a mile or more beneath the seafloor; host to microbial life.
subsidence	a decrease in the elevation of the land or seafloor.
substance	a general term for atoms, molecules, and compounds.
subtidal zone	a subdivision of the littoral zone, the region below the zero tide height.
subtropical gyre	oceanic gyre found at middle latitudes in the major ocean basins.
subtropical jet stream	a fast-moving flow of air that flows between 20° and 30° latitude and at altitudes of 6 to 10 miles.
summer solstice	the time of year when the Sun is at its highest point in the sky and daylength is greatest.
sunny-day flooding	See nuisance flooding.
sunrise point	the point on the eastern horizon where the Sun rises.
sunset point	the point on the western horizon where the Sun sets.
supersaturated	when the concentration of a solute is greater than the saturation concentration.
surf	a breaking wave.
surf prediction	a forecast of the timing, location, and intensity of breaking waves.
surf report	a regularly updated source of information on weather and surf conditions for surfers.
surf zone	the part of the nearshore where waves are breaking.
surface circulation	the largely horizontal flows of water at the surface of the ocean.
surface mixed layer	the topmost layer of waters in the upper ocean with homogeneous properties.
surface runoff	water that flows over the land surface.
surface tension	the enhancement of cohesion at the surface of a liquid.
surface wave	the physical expression of energy moving forward at the surface of the ocean, the air–sea interface.
surface wind stress	the transfer of energy from the wind to the ocean surface along the horizontal plane of the ocean.
surface zone	See epipelagic zone.
surfing	using a specialized board (or your body) to ride waves.
surging breaker	a wave that slides up onto the beach in a swoosh.
suspension	the lifting and transport of a sediment grain within a fluid flow.
Swallow float	a subsurface platform with acoustic transmitters for tracking ocean currents.
swell direction	the compass direction from which ocean swell arrives at a beach.
swell shadow	the reduction or absence of ocean swell at a beach location due to the presence of islands.
swell	the sinusoidal waves that travel out beyond the winds that generate them.
synodic month	the time it takes for the Moon to transit around the Earth and return to its starting point relative to the Earth and Sun.
synoptic scale	distances on the order of hundreds to a thousand kilometers.
synthetic aperture radar	an active microwave sensor used to generate two- and three-dimensional images of Earth’s surface, especially sea ice.
system	an assemblage of parts and processes working together.
systematics	the study of the diversity of life forms and their relationships with each other.
taxa	the different levels in the hierarchical system used to classify life.
taxonomy	the naming of organisms.
telepresence	a livestream from a ship-based ROV transmitted via satellite that permits remote users to watch live video and interact with scientists and technicians on board.
temperate zone	region between the tropical and polar zones in both hemispheres, characterized by mild weather.
temperature	loosely defined, the average kinetic energy of molecules in a system, substance, or object.
temporal resolution	relating to units of time, from fractions of seconds to millennia.
tether	a metal-strengthened fiber-optic cable that transmits two-way signals between an operator and an ROV.
Tethys Ocean	the ocean surrounding the supercontinent of Pangea.
texture	a characteristic of sediment rocks that takes into account the size, shape, and arrangement of their particles, individually or collectively.
theory of common descent	the idea that all life on Earth shares a common ancestor.
thermal	a heat-driven, rising column of air.
thermal contraction	the contraction of rocks caused by cooling.
thermal expansion	the expansion of rocks caused by heating.
thermal-based desalination	a process that uses heat and evaporation of seawater to produce freshwater.
thermocline	a layer of the water column in which temperature declines rapidly.
thermometer	a device used to measure temperature.
thermosphere	the layer above the mesosphere named for its high temperature.
thermosteric sea level rise	sea level rise due to ocean heating.
third quarter	the point halfway between the full and new Moon, when the left half of the Moon is illuminated.
three-cell model	an idealized conceptual model depicting three cells of atmospheric motion in each hemisphere.
threshold velocity	the fluid speed at which a sediment particle begins to move.
tidal current	a horizontal motion of water caused by tidal forces.
tidal datum benchmark	a metal, land-based marker with a known elevation from which the tidal datum can be determined.
tidal datum	the baseline from which tide height is determined.
tidal day	the time of one complete revolution of Earth beneath the Moon, a period of 24 hours and 50 minutes.
tidal force	the variations in the Moon’s (and Sun’s) gravity across Earth’s surface.
tidal height	the vertical distance of sea level above or below a standard baseline.
tidal period	the time between successive high (or low) tides.
tidal range	the difference between the highest and lowest tides in a day.
tide gauge	an instrument that tracks and continuously records sea level.
tide graph	a chart of the change in sea level over time.
time-series investigation	a scientific investigation that observes and measures natural processes over time.
tipping point	a change in the state of a system that is unstoppable or irreversible.
tomol	wood plank canoes constructed by the Chumash people
tow-yo pattern	a W-shaped pattern of sampling using a towfish alternately raised and lowered on its path.
towfish	a winged, sensor-enabled platform towed behind a vessel on a cable.
trace element	See minor constituent.
trace fossil	the fossilized mark of an animal’s activity.
tractive component	the horizontal component of the tidal force.
trade wind	a near-constant easterly wind that blows north and south of the equator.
transectTranspolar Drift Stream	a line of stations on a grid.
transitional wave	See intermediate wave.
transmission	the movement of light energy through a medium.
transpiration	the uptake of water by roots and its subsequent evaporation through the stems, leaves, and flowers of plants.
Transpolar Drift StrTranspolar Sea Routeeam	an extension of the Beaufort Gyre, this current flows off the Siberian Shelf and transports water and sea ice into the Norwegian, Greenland, and Iceland Seas.
Transpolar Sea Route	a hypothesized shipping lane from the Atlantic to the Pacific during future ice-free periods in the Arctic Ocean.
tree of life	See phylogenetic tree.
trench zone	See hadopelagic zone.
triatomic molecule	three atoms of the same or different elements bound to each other.
tributary	source of water to a watershed.
trochoid	the curve traced by a point on a wheel as it moves forward.
Tropic of Cancer	23.5°N; the location where the Sun is directly overhead on the June solstice.
Tropic of Capricorn	23.5°S; the location where the Sun is directly overhead on the December solstice.
tropical zone	the region between the Tropics of Cancer and Capricorn, characterized by warm weather.
troposphere	the lowest layer in Earth’s atmosphere, where humans live.
tsunami	long-period waves generated by vertical motions of the seafloor during shallow earthquakes.
turbidite	a sedimentary deposit formed by turbidity currents.
turbidity current	an underwater, gravity-driven slide of sediments that carves submarine canyons.
turbulence	the chaotic and irregular changes in the speed and direction of flowing water or air.
twilight zone	See mesopelagic zone.
Udden–Wentworth scale	a geological classification system for sediment sizes from clay to boulders.
ultragravity wave	waves with periods from 0.1 to 1 second.
ultraviolet light	electromagnetic radiation with wavelengths shorter than visible light and longer than x-rays.
uncrewed aerial platform	uncrewed, human-controlled, or autonomous platform that carries out missions in Earth’s atmosphere.
uncrewed surface vessel	a self-propelled, self-navigating, sensor-equipped vehicle carrying out various missions on the surface of the ocean.
uncrewed underwater vehicle	a self-propelled, self-navigating, sensor-equipped vehicle carrying out various missions beneath the ocean.
undersampling problem	the lack of sufficient data to fully understand the ocean over all scales of space and time.
undersaturated	when the concentration of a solute is less than the saturation concentration.
underwater research station	semipermanent undersea structure designed for human habitation and scientific research on the seafloor.
underwater swarm robotics	an emerging field of robotics in which multiple autonomous platforms interact with each other to solve problems or carry out missions.
universal solvent	a term used to describe water’s ability to dissolve many substances.
unrooted tree	a phylogenetic tree lacking a trunk and with branches that resemble a starburst pattern depicting relatedness among species.
unstable water column	a water column whose layers are not arranged according to density from the surface to the bottom.
uplift	an increase in the elevation of the land or seafloor.
upper intertidal	in the North American West Coast littoral classification system, the uppermost zone (Zone 1), centered on the high high tide and inclusive of the splash zone.
upper middle intertidal	in the North American West Coast littoral classification system, the third zone (Zone 3), occupying the upper part of the middle intertidal at tide heights of 0.5 to 1.5 meters.
upwelling	the upward movement of subsurface waters toward the surface.
Ur	the first supercontinent, appearing about three billion years ago.
variable gas	a substance whose concentration varies in the atmosphere.
vertical land movement	the increase or decrease in the elevation of a land surface or the seafloor.
visible light	electromagnetic radiation detected by the human eye.
waning crescent	the crescent Moon following the third quarter.
waning gibbous	the gibbous Moon between the full Moon and third quarter.
waning	when the Moon’s lighted portion is diminishing in size.
warm-core ring	a mesoscale eddy with a warm interior relative to its perimeter.
wastewater	water into which human waste and chemicals from homes and businesses have been discharged.
water column	an unspecified volume of water from the surface to a particular depth.
water conflict	dispute over water.
water molecule	the substance formed by the bonding of two hydrogen atoms with one oxygen atom.
water particle	a term representing a dot of water molecules within a wave.
water scarcity	a lack of sufficient water in a region.
water security	the ability of a community to protect access to sustainable quantities of water for practical and peaceful purposes.
water vapor	the gaseous form of water.
watershed	an interconnected region of waterways that drains water, dissolved materials, sediments, and debris to a common outlet.
wave base	the depth at which the orbital motion of water particles in a surface wave becomes negligible.
wave crest	the peak of a wave.
wave diffraction	the lateral shifting of wave energy along a wave front in response to seafloor bathymetry or the presence of an island or structure.
wave dispersion	the separation of swell with different speeds.
wave focusing	the concentration of energy at a point along the wave front in response to seafloor bathymetry.
wave front	a moving line perpendicular to the direction of motion of a wave that stretches across its full width.
wave glider	a sensor-enabled platform that uses solar and wave power to glide through the ocean.
wave height	the vertical distance between the crest and the trough in a wave.
wave interference	the interaction of two or more waves to produce waves of smaller or greater height.
wave orbital	the circular motion of water particles in a wave.
wave period	the time between successive crests of a progressive wave.
wave reflection	a change in the direction of a progressive wave when it encounters a boundary, such as a beach or seawall.
wave refraction	the bending of a wave front in response to changes in seafloor bathymetry.
wave set	a series of similarly sized waves that arrive on a shore in close progression.
wave speed	the forward motion of a wave crest over time.
wave steepness	the ratio between a wave’s height and its wavelength.
wave train	waves of similar speed traveling together.
wave trough	the valley of a wave.
wavelength	the horizontal distance between successive crests in a wave.
waxing crescent	the crescent Moon following the new Moon.
waxing gibbous	the gibbous Moon between the first quarter and full Moon.
waxing	when the Moon’s lighted portion is growing in size.
weather	the instantaneous state of the atmosphere.
weathering	the disintegration and alteration of rock at Earth’s surface.
Weddell Gyre	a polar gyre in the Weddell Sea.
well sorted	having similar grain sizes.
West Australian Current	the broad northward flow of water in the eastern half of the Indian Ocean (no longer classified as a boundary current).
west wind drift current	an eastward-flowing current along the poleward edge of a subtropical gyre.
westerlies	the westerly directed prevailing winds that blow at middle latitudes.
western boundary current	a boundary current that flows along the western edge of an ocean basin.
western intensification	the increase and narrowing of flows along the western boundaries of ocean basins as a result of latitudinal differences in the Coriolis force.
Western Subarctic Gyre	a subpolar gyre off the Kamchatka Peninsula.
whitecap	the broken top of a wave crest, usually caused by wind.
Wien’s law	a principle that defines the relationship between temperature and the wavelength of maximum emission: the hotter an object, the shorter its wavelength of maximum emission.
wind	a movement of air.
wind chop	short and steep irregular waves smaller than swell.
wind duration	the length of time that the wind blows in a given area.
wind spworld oceaneed	the distance moved by a parcel of air over a specified time.
wind wave	wave generated by the wind.
winter solstice	the time of year when the Sun is at its lowest point in the sky and daylength is shortest.
world ocean	all of the waters contained within the ocean basins.
world ocean circulation	the interconnected, interdependent flows of water throughout the world ocean; see also meridional overturning circulation.
wrack line	a line of seaweed and debris parallel to the beach.
x-ray	electromagnetic radiation with wavelengths between 0.03 and 3 nanometers.
XZ graph	a graph oriented with one or more horizontal X-axes across the top and a vertical, downward-pointing Z-axis to indicate depth in the water column.
zero tide height	See tidal datum.
zonal current	a current flowing along a line of latitude.
abductive reasoning	coming to a conclusion based on experience, especially where data are limited.
abiogenesis	the origin of life from non-living materials.
absorption (in geology)	the incorporation of a trace element by a particle.
absorption (in physics)	the transfer of energy from a light ray to an object.
abyssal benthic zone	a zone occupying depths between 3,000 and 6,000 meters on the seafloor.
abyssal fan	a fanlike deposit that forms on the seafloor at the mouths of submarine canyons.
abyssal hill	a region of an ocean basin with relief between 300 and 1,000 meters.
abyssal mountain	a region of an ocean basin with relief greater than 1,000 meters.
abyssal plain	a region of an ocean basin with relief less than 300 meters.
abyssal province	the region of the seafloor that extends from the foot of the continental slope to the start of the hadal regions.
abyssal waters	dense waters found on or near the bottom of the ocean.
abyssobenthic	See abyssal benthic zone.
abyssopelagic zone	a poorly characterized ocean depth zone beneath the bathypelagic zone.
active microwave sensor	sensor that transmits and receives electromagnetic radiation to make measurements of Earth’s surface.
activity model of the scientific method	the interactive, back-and-forth, collaborative approach of teams of scientists for discovering knowledge about the natural world.
adaptive radiation	the diversification of a lineage of organisms into different environments and ecological roles.
adaptive tracking system	artificial intelligence–enhanced computer software that enables AUVs to navigate according to environmental conditions.
adsorption	the attachment of a trace element to a sinking particle.
aeolian dust	particles of sediment transported by winds.
aerial investigation	a scientific investigation that employs sensors aboard crewed or uncrewed airborne platforms to make observations or obtain measurements of natural processes.
aerobic respiration	the metabolic breakdown of organic matter in the presence of oxygen.
aerosol	a group of solid or liquid particles less than 1 micrometer in diameter, important in the formation of clouds and other atmospheric processes.
Africa	second-largest continent, where modern humans originated.
aggregation	the sticking together of particles.
agronomic revolution	the transformation of the seafloor from crusty to soft during the Ediacaran.
Agulhas Current	the western boundary current in the South Indian Ocean.
air column	an undefined cylinder of air from Earth’s surface to a given altitude.
air density	the number of molecules in a given volume of air.
air–sea interface	the boundary between the ocean and the atmosphere.
Alaskan Gyre	a subpolar gyre off the coast of Alaska.
albedo	the reflectivity of Earth’s surface.
anaerobic respiration	the metabolic breakdown of organic matter using substances other than oxygen as an electron acceptor.
ancient sunlight	energy from the Sun that fell on Earth millions of years ago.
Andes	the largest continental mountain range in the world.
animal-tagging investigation	a scientific investigation that uses sensors attached to animals to obtain observations or measurements of natural processes, generally in places inaccessible to humans.
anion	a negatively charged ion.
Annelida	a phylum that includes segmented worms.
anoxygenic photosynthesis	photosynthesis that does not yield oxygen as a by-product.
Antarctic Circle	66.5°S; the latitude below which no or little sunlight reaches between the fall and spring equinoxes in the Southern Hemisphere.
Antarctic Circumpolar Current	the eastward-flowing current that encircles Antarctica.
Antarctica	the southernmost continent, host to 60 percent of Earth’s freshwater.
anthroposphere	the human system.
aphelion	the point in Earth’s slightly elliptical orbit where its distance from the Sun is greatest.
aphotic zone	the dark waters of the ocean.
aquifer	a water-bearing stratum of permeable rock, sand, or gravel.
Archaea	unique single-celled organisms found throughout the world ocean and in extreme environments.
archaeal organelle	complex subcellular structure in Archaea analogous to that of a eukaryote.
Archean Oxidation Event	one of several whiffs of atmospheric oxygen present in the Archaean prior to the Great Oxidation Event.
Archean	the second geologic eon, occurring from 4 to 2.5 billion years ago.
Arctic Circle	66.5°N; the latitude above which no or little sunlight reaches between the fall and spring equinoxes in the Northern Hemisphere.
Arctic Ocean	the polar ocean at the North Pole.
Arthropoda	a phylum of organisms with jointed legs that includes crustaceans, insects, and spiders.
artificial intelligence	a broad category of computer science that aims to mimic how humans think, act, and adapt.
Asia	Earth’s largest continent and home to some 60 percent of the human population.
asphaltum	a tar-like substance found on beaches that forms from seeps of oil beneath the ocean
astronomical unit	the average distance between the Earth and the Sun.
Atlantic Ocean	the second-largest ocean in the world.
atmosphere	the gases surrounding Earth.
atmospheric cell	the large-scale convection of one part of the atmosphere.
atmospheric diving suit	a self-contained, pressurized, one-person diving suit used to explore waters deeper than scuba permits.
atmospheric river	extremely wet upper-air currents that appear like rivers on satellite images.
atmospheric window	the selectivity of the atmosphere to different wavelengths of electromagnetic radiation.
atom	a building block of matter.
aurora australis	the southern lights, caused by interactions of the Earth’s magnetic field and atmosphere with the solar wind.
aurora borealis	the northern lights, caused by interactions of the Earth’s magnetic field and atmosphere with the solar wind.
Australia	the least populous continent (not including Antarctica, which has a small temporary population).
autonomous profiling float	sensor-enabled robotic device that rises and sinks in the water column to carry out various ocean measurements and transmit the data to shore stations using satellites.
autonomous underwater vehicle	a self-propelled, self-navigating, sensor-equipped underwater vehicle for collecting oceanographic data or conducting search-and-rescue operations in the ocean.
autotroph	an organism capable of manufacturing its own food.
axial tilt	the angle of Earth’s axis relative to its plane of orbit around the Sun.
Azores Current	an eastward-flowing, southerly branch of the North Atlantic Current.
backshore	the flat portion of a beach adjacent to terrestrial vegetation, only occasionally inundated by waves and tides.
bacteria	unique single-celled organisms found virtually everywhere on Earth.
bacterial organelle	complex subcellular structures in bacteria analogous to those of a eukaryote.
barystatic sea level rise	sea level rise due to melting glaciers, changes in land storage of water, and changes in the atmosphere.
basalt	an extrusive, dense, dark-colored igneous rock.
bathyal benthic zone	a zone extending from the shelf break to the bottom of the continental rise.
bathybenthic	See bathyal benthic zone.
bathypelagic zone	the depth zone beneath the mesopelagic zone, characterized by a complete absence of surface light.
bathyscaphe	a hollow steel sphere attached to a giant, gasoline-filled balloon for exploring the ocean depths.
bathysphere	a hollow steel sphere with transparent baseball-sized portholes for making observations in the deep ocean.
beach cusp	crescent- or scallop-shaped deposits of sand parallel to the beach.
beach diamond mining	the removal of diamonds from beaches or the seafloor by commercial enterprises.
beach face	the sloped portion of a beach alternately submerged and exposed during a tidal cycle.
beach	loose bits and fragments of material along the shore of a body of water, including lakes, rivers, and the world ocean.
beach nourishment	the artificial supply of sand to a beach to increase its size.
beach profile	a cross-sectional view of the slope of a beach.
beach sand budget	a quantitative accounting of the sources and sinks of sand for a beach.
beach scarp	a clifflike berm at the boundary of the foreshore and backshore.
beach starvation	the loss of sand from a beach due to a decrease in its supply.
Beaufort Gyre	a polar gyre in the Beaufort Sea.
Beaufort wind force scale	a visual guide for determining wind speed from sea state.
Benguela Current	the equatorward-flowing eastern boundary current in the South Atlantic Ocean.
benthic depth zone	ocean depth zone along the seafloor from the shoreline to the deepest trench.
benthic lander	autonomous, sensor-enabled platform that sinks to the seafloor, carries out observations and experiments, and returns to the surface when signaled or at a predetermined time.
benthic organism	organism that lives on or within the seafloor.
benthic-pelagic coupling	the ecological interaction between the seafloor and the overlying water column.
benthopelagic zone	the portion of the water column within 100 meters of the seafloor.
berm	a shelf of sand left by high-energy waves in a receding tide.
bias	a less than objective, partial view of evidence.
big data	a subdiscipline of computer science for analyzing data sets whose size or complexity exceeds the capabilities of traditional software and computers.
big wave surfer	a surfer who rides waves greater than 20 feet in height.
bilateral symmetry	a shape that can be divided into two halves.
Bilateria	a group with bilateral symmetry that includes all animals except sponges, comb jellies, and cnidarians.
binomial nomenclature	a two-part naming system that includes the genus as the first part of the name and the species as the second part.
bio-optical oceanographer	a human, robot, or animal that carries out optical measurements of the ocean’s living systems.
bio-optical oceanography	the scientific study of the optical properties of living systems in the ocean.
biogeochemical cycle	the assembling and disassembling of molecules in a continuous recycling of Earth’s matter.
biogeography	the study of the relationship between the distribution of organisms and their environment.
biological oceanography	the scientific study of the biological properties and processes in the world ocean.
biological weathering	the breakdown of rocks by biological processes.
biologically important nutrient	a dissolved substance required for the growth of phytoplankton.
bioluminescence	biologically produced light.
biomineralization	the process by which organisms incorporate minerals into their body structures.
bionic AUV	autonomous underwater vehicle that mimics the appearance and swimming behavior of a marine organism (also known as a robofish).
biosphere	the Earth’s living systems.
biotite	a gray or black silicate mineral containing mica found as grains in beach sand.
bioturbation	the disturbance and mixing of sediments by organisms.
black carbon	a type of aerosol formed from the incomplete combustion of fossil fuels; an air pollutant.
blue water oceanography	the study of the oceanic waters.
bond	a sharing or exchange of electrons by two or more atoms that results in their attraction to each other.
boundary current	a current that flows along the outer edge of an ocean basin where it meets a continent.
Brazil Current	the western boundary current in the South Atlantic Ocean.
breaker	See surf.
brine rejection	the precipitation of salts from seawater during the formation of sea ice.
brine	the salty syrup that remains when freshwater has been removed from seawater.
bubble injection	the penetration and dissolution of bubbles of air caused by breaking waves.
buoyancy compensator	a device worn by scuba divers to control buoyancy.
buoyancy	the tendency of an immersed object to rise, sink, or remain in place.
buoyancy-driven mixing	the homogenization of the water column as a result of an increase in the density of surface waters.
buoyant force	the upward force exerted on a fluid or object immersed within a fluid.
byssal thread	a tough, fibrous, threadlike material used by mussels to attach to rocks.
calibration	the process of verifying the accuracy of an instrument.
California Countercurrent	a northerly flow of the California Current along the coastlines of San Diego, Orange County, and Los Angeles.
California Current System	the system of eastern boundary currents that flow along the western US in the North Pacific Ocean.
California grunion run	the twice-monthly periods when the California grunion swim onto the beach face to reproduce.
California Undercurrent	a subsurface, northward-flowing current beneath the Davidson Current.
calving	the fracture and fragmentation of a glacier and its discharge into the ocean.
Cambrian	a geologic period from 541 to 485.4 million years ago.
Cambrian radiation	the rapid increase in animal diversity in the Cambrian.
Canary Current	the equatorward-flowing eastern boundary current in the North Atlantic Ocean.
capillary wave	a wave whose wavelength is smaller than 1.73 centimeters.
carbon dioxide	a molecule composed of carbon and oxygen that provides a carbon source for plants and acts as a greenhouse gas in Earth’s atmosphere.
carbonate platform	limestone platform attached to a continental shelf, built by a combination of biological, sedimentary, and geological processes.
cardinal directions	north, south, east, and west.
carnivory	the eating of one animal by another.
cation	a positively charged ion.
Celsius scale	a temperature scale that sets zero as the freezing point and 100 as the boiling point of water.
Central South Equatorial Current	the central branch of the South Equatorial Current in the Atlantic Ocean.
chain of reasoning	a logical extension of previous scientific work on a problem.
Challenger Deep	a part of the Mariana Trench, the deepest location in the world ocean.
charismatic megafauna	species of large animals best known and loved by the general public.
chemical oceanography	the scientific study of the chemical properties and processes in the world ocean.
chemical symbol	the letter or letter combination that represents an element.
chemical weathering	the breakdown of rocks by chemical processes.
chemisorption	the chemical attraction of elements to particles.
chemoautotroph	an organism that uses chemical energy to manufacture its own food.
chemosynthesis	the manufacture of organic carbon from carbon dioxide and inorganic substances using energy obtained from inorganic chemicals.
chloride ion	the ionic form of chlorine.
chlorofluorocarbon	a class of gas molecules containing chlorine and fluorine.
chlorophyll	the primary light-absorbing pigment of all oxygen-producing photosynthetic organisms.
Chlorophyta	a phylum that includes single-celled and multicellular green algae.
circalittoral zone	the region below the infralittoral zone extending to the bottom of the euphotic zone.
citizen science	the reporting and collection of scientific data by the public.
clade	a group of organisms that share a common ancestor.
cladistics	a method of classification that uses measurable characteristics to determine degrees of similarity between organisms.
clam gun	a cylindrical device used to capture clams buried in the sand.
classification	the organization of life into groups that share certain characteristics.
cleaning station	place on a seamount or reef where cleaner organisms remove parasites from other organisms.
climate	the long-term average of weather conditions at a given location or globally.
climate zone	a region of Earth defined by a particular average weather.
cloud	a visible form of suspended liquid or solid water.
cloud condensation nucleus	aerosol that acts as a site of condensation for water vapor in the formation of clouds.
Cnidaria	a phylum that includes sea anemones, corals, and jellies that use stinging cells.
coastal armoring	the hardening of a beach to prevent its erosion by waves.
coastal array	ocean observatory deployed on a continental shelf (i.e., near a coastline).
coastal benthic zone	See sublittoral zone.
coastal bluff	a rounded seaside cliff formed by wave erosion and uplift.
coastal cell	See littoral cell.
coastal ocean	the ocean waters overlying the continental shelves.
coastal oceanography	the study of coastal waters.
coastal waters	waters overlying the continental shelves.
cohesion	the sticking together of water molecules.
cold seep	places in the seafloor where methane and other energy-rich fluids leak through the sediments.
cold-core ring	a mesoscale eddy with a cold interior relative to its perimeter.
collapsing breaker	a wave where the entire wave face disintegrates into foam.
colonial organism	an organism with hundreds to thousands of identical cells, each of which may produce a whole new organism.
comet	an icy object that travels across the solar system in a highly eccentric orbit.
compass rose	an illustration that depicts the cardinal and ordinal directions.
compound	molecules composed of different atoms.
compressional heating	the heating that occurs due to increases in air pressure as wind flows from higher to lower elevations.
computer modeling investigation	a scientific investigation that uses computers to visualize or quantify natural processes.
conceptual model	a mental picture, often in visual form, of how we think something works.
conduction	the transfer of heat through molecule-to-molecule contact.
conductivity-temperature-depth instrument	an electronic depth-profiling instrument with sensors for measuring conductivity (i.e., salinity), temperature, and depth.
conservative element	an element whose ratio with other elements remains constant.
constructive interference	the interaction of two or more waves that produces a wave larger than the original waves.
continent	the elevations in Earth’s crust.
continental crust	the part of Earth’s crust that forms the continents.
continental margin	the submerged edges of the continents.
continental rise	a gently sloping region of sediments at the base of the continental slope.
continental shelf province	the submerged flat portion of the continental margins.
continental slope province	the steeply sloped part of the continental crust that extends from the shelf break to the abyss.
contour current	a current that flows along depth contours of continental slopes.
contourite	a sedimentary deposit formed by contour currents.
convection current	the heat-driven, circular motion of fluids (air and water) from one place to another.
convection	the transfer of heat by moving fluids.
convective heating	motions of the atmosphere or ocean that transfer heat from one location to another.
coral bleaching	the expulsion of photosynthetic symbionts by a coral polyp in response to prolonged elevated water temperatures.
Coriolis force	the apparent deflection of moving objects across Earth’s surface.
coronal mass ejection	an intense outburst of particles from the Sun.
covalent bond	the chemical bond formed when atoms share electrons
crescent Moon	the illuminated slivers of Moon visible just after and just b.efore the new Moon
Cromwell Current	See Equatorial Undercurrent.
cross-shore transport	the wave-generated movement of sediments toward and away from the beach face.
cryosphere	the frozen parts of Earth.
crystal lattice	the three-dimensional, symmetrical, and repetitive arrangement of atoms in a crystal.
CTD	See conductivity-temperature-depth instrument.
Ctenophora	a phylum that includes comb jellies.
cycloid	the curve traced by a point on the perimeter of a wheel as it moves forward.
Day Zero	the day that a city’s water supply will run out.
daylength	the number of hours in the lighted portion of the day.
deductive reasoning	the approach of eliminating all possible hypotheses until only one cannot be disproven.
deep circulation	the three-dimensional flows of water in the abyssal ocean.
deep sea	everywhere beneath the euphotic zone.
deep water wave	a wave that travels in water deeper than one half its wavelength.
deforestation	the removal of trees from a landscape.
delta	a large deposit of sediments formed at the mouth of a river.
density	the mass of molecules occupying a given volume.
depocenter	a site of enhanced organic matter sedimentation in oceanic trenches.
desalination	the process of creating freshwater from saltwater.
destratification	the disappearance of the seasonal thermocline due to mixing.
destructive interference	the interaction of two or more waves that produces a wave smaller than the original waves.
detritus	a general term for particles of dead matter in the ocean.
diatomic molecule	two atoms bound to each other.
diffusion	the movement of molecules across a boundary due to a concentration gradient.
digital thermometer	a temperature-measuring device that displays digital data.
dipole	a substance that exhibits a separation of electrical charges.
dissolution	the dissolving of substances in water.
dissolved gas	gas-phase elements in seawater.
dissolved organic matter	organic matter dissolved in seawater.
dissolving	the mixing of a solute into a solvent.
disturbing force	a force that creates an ocean wave.
diurnal tide	a once-daily tide.
diving bell	dome-shaped, air-filled chamber that permits divers to work at depth.
domain	the highest level of organization in the classification of life.
downslope wind	a wind that blows from high to low elevations.
drift bottle method	the use of buoyant containers for tracking ocean currents.
drifter	a platform that floats on the ocean’s surface to track currents.
duck dive	a technique of plowing the nose of a surfboard under a wave.
Earth system	the various interdependent, interconnected systems that collectively regulate Earth.
Earth’s axis	the imaginary line around which the Earth rotates.
Earth’s energy imbalance	the excess (or deficit) between solar radiation levels to and from Earth’s surface.
Earth’s geophysical fluids	the air, water, and molten rock found on our planet.
Earth’s orbit	the movement of Earth around the Sun.
Earth’s rotation	the turning of Earth on its axis.
Earth’s surface reservoirs	water found just beneath and above Earth’s surface.
East Australian Current	the western boundary current in the South Pacific Ocean.
eastern boundary current	a boundary current that flows along the eastern edge of an ocean basin.
Echinodermata	a phylum of organisms with a spiny exoskeleton that includes sea urchins, sea stars, brittle stars, sea cucumbers, and sand dollars.
ecology	the study of interactions between a co-occurring community of organisms and their environment.
ecosystem engineering	the restructuring of a habitat through the activities of organisms.
ecosystem service	an economic, ecological, restorative, or cultural benefit provided by an ecosystem to humans.
Ediacara biota	the fossil assemblage that appeared from 571 to 541 million years ago, representing the oldest macroscopic marine communities preserved in rocks.
Ediacaran	a period of geologic time 635 to 541 million years ago that set the stage for the widespread diversification of life that occurred in the Cambrian.
Ekman depth	the depth where the current flow is 37 percent of the surface current flow and in a direction 180° opposite to the direction of the wind.
Ekman spiral	the wind-generated, Coriolis-influenced, multidirectional flow that resembles a spiral stack of books from the sea surface to the limit of wind energy penetration.
Ekman transport	the average flow from an Ekman spiral in a direction 90° to the right (or left) of the wind (depending on the hemisphere).
electrical conductivity	the flow of electrons through a wire.
electrode	a piece of metal through which electricity flows.
electromagnetic radiation	all of the types of radiant energy emanating from stars.
electromagnetic spectrum	a chart of the range of all types of electromagnetic radiation in order of increasing or decreasing wavelength.
electron	a negatively charged subatomic particle that orbits the nucleus.
electronegative	the negatively charged region of a polar molecule.
electropositive	the positively charged region of a polar molecule.
electrostriction	the slight reduction in volume that occurs when salts dissolve in water.
element	an atom with a specific and unique number of protons.
elittoral zone	a term proposed to account for depths deeper than the circalittoral but shallower than the bathyal.
emergent property	a property of a system not apparent when studying its parts alone.
emersion	when an organism or object is exposed to air.
Emery method	a technique employing two 2-meter sticks and a tape measure for determining the beach profile.
endoskeleton	a skeleton on the inside of an animal.
endosymbiosis	the merging of two single-celled organisms into one.
energy	the ability to do work.
environment	the geological, chemical, physical, and biological conditions present at a given time and place.
eon	the largest division of geologic time.
epifauna	organisms living upon a substrate.
epipelagic zone	the region of the upper ocean from just beneath the sea surface microlayer to the lower boundary of the euphotic zone.
equatorial current	a current that flows east to west along the equator.
equatorial doldrums	a region of calm air over the equator.
equatorial plane	the imaginary horizontal plane that passes through Earth’s equator.
Equatorial Undercurrent	a subsurface current flowing west to east along the equator.
equilibrium model of tides	a simplified model of ocean tides on an Earth with no continents.
equinox	the two times of the year when the Sun is directly overhead at the equator.
Eukarya	unique single-celled and multicellular organisms descended from Archaea and bacteria.
eukaryogenesis	the sequence of events that gave rise to the Eukarya.
eukaryote	a cell type with visible organelles characteristic of Eukarya.
euphotic zone	the lighted region of the upper ocean from the sea surface to the depth where sunlight diminishes to 1 percent of its surface value.
Europe	part of the Eurasian landmass, home to the third-largest human population on Earth.
evaporation fog	the condensation of water vapor over a warm lake.
evaporation	the transformation of liquid water into water vapor.
evaporite	deposit of salt formed by evaporation of seawater trapped during uplift of isolated basins.
evolutionary arms race	the diversification of structures, physiologies, and behaviors to compete with predators or prey.
exoskeleton	a skeleton on the outside of an animal.
exosphere	the layer above the thermosphere that may extend beyond the Moon.
external particle	a particle delivered to the ocean from an external source.
extreme sea level rise	a rapid change in sea level due to waves, tides, and storm surge.
Fahrenheit scale	a temperature scale that sets 32 as the freezing point and 212 as the boiling point of water.
fall equinox	the time of year when daylength is decreasing and the Sun is passing directly over the equator into the opposite hemisphere.
falsification	the process of disproving a hypothesis.
fantail	the back end (i.e., stern) of a ship.
feedback loop	a process that exerts a change on a system.
feldspar	a yellow-to-red aluminosilicate mineral containing calcium, sodium, or potassium found as grains in beach sand.
Ferrel cell	the atmospheric cell that occurs between the Hadley and polar cells.
fetch	a distance over which the wind blows in the same direction.
fetch width	the width of the wind field that generates a wave.
field investigation	See oceangoing investigation.
first quarter	the point halfway between the new and full Moon, when the right half of the Moon is illuminated.
float	a platform that drifts beneath the ocean’s surface to track currents.
flux	a pathway and rate of flow of a substance into and out of a reservoir.
fog	a cloud formed near the ground.
forebulge	a region of uplift adjacent to a glacier.
forebulge collapse	the subsidence of land following retreat of a glacier.
foreshore	the portion of a beach nearest the water extending from the beach scarp (if present) to the lower boundary of the beach face.
fourth paradigm	the use of computers to explore and mine big data for information.
frost wedging	the freezing and expansion of water in rock cracks that bursts rocks apart.
full Moon	when the side of the Moon facing Earth is fully illuminated.
fully developed sea	a sea exhibiting the maximum wave size under existing wind conditions.
Gaia hypothesis	the idea that Earth resembles a living organism.
galaxy	collection of star systems bound together by gravity.
gamma ray	electromagnetic radiation with the highest energy and shortest wavelength.
gas	a fluid of indefinite shape and volume that will expand to fill any container in which it is held.
gas planet	a planet whose composition is predominantly gaseous materials.
gene	a segment of genetic material that codes for proteins and other cellular functions.
genus	the second-lowest level of organization in the classification of life; above species and below family.
geobiology	the study of life’s interactions with the Earth and their evolution over geologic time.
geoid	the theoretical equal-gravity surface of Earth.
geologic time	the history of Earth from its beginning.
geological oceanography	the scientific study of the geological properties and processes in the world ocean.
geomagnetic storm	disruptions of Earth’s magnetic field caused by coronal mass ejections.
geophysical fluid dynamics	the study of fluid flows in nature.
geosphere	the solid Earth.
geostrophic current	a current that results from a balance between the pressure gradient force and the Coriolis force.
gibbous Moon	when three quarters of the Moon is illuminated.
glacial isostatic adjustment	the changes in land surface elevation as a result of the disappearance of glaciers.
glider	winged, sensor-enabled, buoyancy-driven platform for carrying out various measurements over large expanses of the ocean.
global array	ocean observatory deployed in a deep water location.
global atmospheric circulation	the three-dimensional motions of air within the troposphere.
global climate change	the change in Earth’s climate over geologic time.
global mean sea level rise	the global increase in the volume of the ocean.
global scale	distances greater than a thousand kilometers.
global warming	the increase in Earth’s average temperature since 1850.
global water crisis	the lack of water for billions of people around the globe.
global water cycle	a conceptual (or mathematical) model of the movement of water between various reservoirs on Earth’s surface.
grain	an individual particle of sand.
grain size distribution	the frequency of different grain sizes in a sediment deposit.
granite	an intrusive, light-colored igneous rock.
gravitational force	the force of attraction between objects with mass.
gravity	See gravitational force.
Gravity Recovery and Climate Experiment	a satellite-based measurement of the variations in gravity that result from changes in the distribution of mass across Earth’s surface.
Great Barrier Reef	the largest coral reef in the world, located off the east coast of Australia.
Great Ordovician Biodiversity Event	one of several periods of rapid diversification of organisms during the Early to Middle Ordovician.
Great Oxidation Event	the rise in atmospheric oxygen about 2.5 billion years ago.
greenhouse effect	warming as a result of gases in Earth’s atmosphere.
greenhouse gas	an atmospheric gas that absorbs longwave radiation.
Greenland	the world’s largest island.
groin	a structure built perpendicular to the shore to trap sediments on a beach.
ground truthing	the process of independently verifying the accuracy and precision of measurements made from satellites.
groundwater	water stored in natural underground reservoirs.
group speed	the speed of a wave train equal to half the speed of individual waves.
Gulf Stream	the western boundary current in the North Atlantic Ocean.
guyot	a flat-topped seamount.
habitat	the range of environments that support the survival and reproduction of a species.
hadal benthic zone	an ocean zone occupying depths below 6,000 meters on the seafloor.
hadal lander	benthic lander capable of reaching the deepest parts of the world ocean.
hadal province	the seafloor at depths below 6,000 meters.
Hadean	the first division of geologic time, from 4.56 to 4 billion years ago.
Hadley cell	the atmospheric cell that occurs over the tropics.
hadobenthic zone	See hadal benthic zone.
hadopelagic zone	a depth zone bounded by the walls of oceanic trenches.
halite	the crystalline form of sodium chloride.
headland	a point of land that juts out into the ocean.
headless canyon	a class of submarine canyon confined to the continental shelf.
headwaters	the source of a stream or river.
heliosphere	the Sun and solar system.
heritage	the properties of sediments inherited from their parent rock.
heteronuclear molecule	two atoms of different elements bound to each other.
hierarchical system	a system characterized by different levels, one above or below the other.
high high tide	the highest of the high tides in a mixed tide.
high low tide	the highest of the low tides in a mixed tide.
high tide	when sea level reaches its highest extent during the day.
high-pressure region	a region whose air pressure is higher than surrounding regions.
high-tide flooding	See nuisance flooding.
Himalayas	Earth’s tallest mountains.
holey sock drogue	a large, subsurface cloth cylinder attached to a surface float that improves the accuracy of current measurements.
homonuclear molecule	two atoms of the same element bound to each other.
horse latitudes	a region of calm air at about 30°N/S.
Humboldt Current	See Peru–Chile Current.
hybrid remotely operated vehicle	a cross between an ROV and an AUV that permits operation with or without a tether.
hybrid-type trace element	trace elements with multiple pathways for their removal from seawater.
hydrogen bond	a type of bond formed between hydrogen atoms and other molecules.
hydrogen fusion	a reaction of hydrogen atoms that sustains the release of energy from the Sun.
hydrographic station	a shipboard sampling location in the ocean, usually arranged as points on a grid.
hydrosphere	Earth’s waters.
hydrostatic equilibrium	the balance between the downward pull of gravity and the upward force of pressure, where no net movement of the air occurs.
hydrostatic skeleton	a skeleton whose shape is maintained by water pressure.
hyperspectral imager	sensor capable of detecting hundreds of narrow bands of electromagnetic radiation.
hypothesis	a carefully worded, conditional, and testable explanation of how nature works.
hypothetico-deductive approach	the general process of generating and disproving hypotheses based on observations or experiments.
hypsographic curve	a graph of the percentages of Earth’s crust at a particular elevation or depth.
ice	the solid form of water.
iceberg	a chunk of glacier floating in the ocean.
igneous rock	a rock formed from volcanic activity within or upon Earth’s surface.
Indian Ocean	the third-largest ocean in the world.
Indonesian Throughflow	the system of currents flowing through Indonesia that acts as a control valve on the world ocean circulation.
inductive reasoning	the process of extracting general principles and possible hypotheses from a limited set of observations or data.
infauna	organisms living within a substrate.
infiltration	the flow of water through soil and porous rock.
infragravity wave	waves with periods from 30 seconds to 5 minutes.
infralittoral zone	the region immediately below the littoral zone, exposed only on the lowest tides.
infrared light	the portion of the electromagnetic spectrum with wavelengths greater than visible light and shorter than radio waves.
inherited character	the trait of an organism coded in its genes and passed down by its ancestors.
interdisciplinary science	a science that integrates the tools, approaches, knowledge, and understanding of multiple disciplines to solve scientific problems.
intermediate wave	a wave that travels in water shallower than one half and greater than one twentieth its wavelength.
internal particle	a particle formed within the ocean.
internal wave	a wave along a density boundary beneath the surface of the ocean.
International System of Units	the system of units used by scientists.
intertidal zonation	the grouping of organisms into horizontal bands along vertical gradients in elevation along a shoreline.
intertidal zone	a subdivision of the littoral zone, the region of alternating submersion and emersion as a result of tides or waves.
Intertropical Convergence Zone	the region where the trade winds meet, characterized by bands of clouds and high rainfall.
invertebrate	an organism lacking a backbone.
ion	an atom or molecule whose number of positively charged protons differs from its number of negatively charged electrons.
ionic bond	a bond formed when atoms exchange electrons.
isobar	a line of equal pressure.
isobath	a line of constant depth.
isostasy	the equilibrium height of Earth’s crust as it floats on the mantle.
isothermal	a layer of water whose temperature is identical over a range of depths.
jet stream	swift currents of air that blow west to east at high altitudes.
Kármán line	the boundary between Earth’s atmosphere and outer space.
kelp highway	the idea that early humans traveled by watercraft from Asia to North America consuming seafood along the way.
kinetic energy	energy in motion.
king tide	an extremely high tide.
kite aerial photography	a type of above-surface photography that uses kites to elevate the camera.
Kuiper Belt	a donut-shaped system of icy objects found just beyond the orbit of Neptune.
Kuroshio Current	the western boundary current in the North Pacific Ocean.
laboratory investigation	a scientific investigation carried out in a laboratory.
Lagrangian platform	a platform that moves with the currents.
land breeze	an offshore wind generated by temperature differences between the land and ocean.
land of the midnight sun	polar regions that experience 24 hours of daylight during the summer.
Late Heavy Bombardment	a period during the Hadean characterized by a high number of asteroid and comet impacts.
latent heat of fusion	the heat required to transform a solid to a liquid or vice versa.
latent heat of vaporization	the heat required to transform a liquid to a gas or vice versa.
latent heat	the heat required to change the state of a substance.
lava	molten rock that spills onto Earth’s surface.
law of conservation of energy	the observation that energy can neither be created nor destroyed, but it can change forms.
Leeuwin Current	the poleward-flowing eastern boundary current in the South Indian Ocean.
lichen	a symbiotic organism formed by a fungus and an alga.
liquid	a fluid with an indefinite shape but a near-constant volume (as opposed to a gas).
liquid water	the liquid form of water.
littoral cell	a conceptual model of the watershed–beach–submarine canyon system that governs the size of beaches.
littoral zone	the region between the tides (where present) along the very edge of the ocean.
living sea	the interconnected, self-replicating, and self-sustaining network of diverse life forms that inhabit the world ocean.
living shoreline	a structure that employs artificial and natural landscapes to protect coastlines and preserve the ecological services provided by coastal habitats.
long period wave	waves with periods from 5 minutes to 12 hours.
longshore current	a wave-generated flow of water parallel to the beach.
longshore transport	the transport of sediments and debris by the longshore current.
longwave radiation	collectively, the portion of the electromagnetic spectrum that includes mid- to far-infrared wavelengths.
Low Elevation Coastal Zone	lands with an elevation of less than 10 meters
low high tide	the lowest of the high tides in a mixed tide.
low low tide	the lowest of the low tides in a mixed tide.
low tide	when sea level reaches its lowest extent during the day.
low-pressure region	a region whose air pressure is lower than surrounding regions.
low-tide terrace	a flat portion of the lower foreshore exposed at low tide.
lower intertidal	in the North American West Coast littoral classification system, the fourth zone (Zone 4), occupying tide heights from zero to the height of the lowest tide.
lower middle intertidal	in the North American West Coast littoral classification system, the third zone (Zone 3), occupying the lower part of the middle intertidal at tide heights of zero to 0.5 meter.

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