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Home , Benthic zone, Earth tide, Halocline

GLOSSARY GLOSSARY

Abyssal - deep portions of the , typically below Bed load (&action load) - quantity of bottom 2000 fa (3700 m). transported by a through traction, that is by Abyssal hills - small elevations (often extinct volcanoes) saltation, rolling, and sliding. distributed over large tracts of the seafloor. Benthic - pertaining to the bottom terrain of oceanic Abyssalplain - a flat or gently sloping, almost featureless regions. region of the deep ocean overlain with . Bloom - a rapid growth of phytoplankton in spring and Acceleration ofgravity @) -the rate of change with time of fall that causes large temporary of the the velocity of an object caused by the earth’s gravita- organism. Can result in discolored or toxic tional . known as red . (See ). Advection - the transport of a property (e.g. heat or salt) Bore (hydraulicjump)- an almost vertical, solitary wave by fluid motions such as currents or winds. front caused when the water speed associated with the Aerobic - conditions where free is present; re- crest begins to exceed the translation speed of the wave. quires free oxygen for organic existence and growth. Waves on beaches commonly deform into a bore prior Amphidromicpoint- a point at which there is no tide and to breaking. The water flow associated with a bore around which the cotidal lines rotate over a tidal cycle. changes abruptly from a region of low depth and high Tidal amplitudes (corange lines) increase outward speed to one of high depth and low speed with a series from this point to cover an area called the amphidromic of undulations behind the leading crest (see Tidal region. bore). Amplitude - the magnitude or half-cycle displacement of Bottomfiction - the retarding force on water moving a wavelike fluctuation as measured from its mean or over the bottom. It increases with increased roughness equilibrium value. The amplitude of an ocean wave is of the bottom, current speed, and degree of turbulence half its trough-to-crest height, or the height from the in the water. still water level to the wave crest; in the case of the tide, - water having a of 0.50-17%0, amplitude equals half the range. common to nearsurface estuarine environments from Anaerobic - lacking in free oxygen. Certain can late spring to early autumn. live in such conditions. - the net upward force exerted on an object or Andular momentum - the momentum of a particle or parcel of fluid due to the difference in between parcel of water arising from its rotation about an axis. it and the surrounding fluid; quantitatively equal to the Its value is proportional to the particle’s mass, linear of the water displaced by the object. velocity, and distance from the rotation axis. Anomalistic month - the average period of the ’s orbit around the earth with respect to the lunar per- Cat’spaw- a puff of wind; a light breeze that temporarily igee; equal to about 27.55 days. ruffles patches of the water surface. Anticyclonic - a sense of rotation opposite to that of the Chop - short-crested waves that spring up following earth’s rotation; clockwise in the northern hemisphere onset of a moderate breeze, and break readily at the and counterclockwise in the southern hemisphere. crest. Antinode (antinodal line, antinodal point) - the position Coastalplain - a plain composed of gently sloping or flat (or line) of maximum displacement in an oscillating strata of sedimentary material fronting the coast and region ofwater. The region midway between two nodal generally derived from a recently emerged portion of lines in a standing wave pattern. the bottom. Apogee - position in the moon’s orbit that is hrthest Cobble - a water-worn rock fragment between 64 and from the earth (opposite to perigee). 256 mm in diameter, larger than a pebble but smaller Asthenosphere (or mantle) -the region of the earth with than a boulder. plastic-flow characteristics between the Constituent,tidal - a harmonic (sinusoidal) contribution (lithosphere) and the core. in a mathematical expression for the tide-generating Attenuation - a reduction in wave amplitude. force used to specify a selected cycle in the tide or tidal current. Each constituent has a fixed period but an amplitude that is determined by observation or Backing - a change in the wind or current direction in a through a model. counterclockwise sense (opposite to Eering). Continentalmagin - the portion of the seafloor adjacent Bar - an elongate ridge of , gravel, or other uncon- to the continent and separating it from the . solidated material built in shallow water by the action The includes the , of waves and currents, especially at the mouth of a river continental slope, and or . Convective overturn - the process by which the surface Basalt - a fine-grained, dark-coloured igneous rock. The , cooled sufficiently by the air to make them and granitic continents are thought to be more dense than underlying waters, sink and are re- underlain by basaltic material. placed by an upward motion of less dense water. In the

- 249 - subarctic Pacific region of the North Pacific Ocean, the edge oftwo regions with different current speeds or overturning takes place in winter but is limited to the directions. upper 100 m ofwatcr due to the presence ofthe pcrma- - a near-shore (shore edge) wave with an nent between 100 and 200 m. accompanying pattern of horizontal currents that pro- Corange line - a line joining regions of equal tide range. gresses parallel to the coast with crests normal to the Coriolisfirce ( effect) -an apparent force due to the coastline. Wave heights diminish rapidly seaward ofthe earth's rotation that acts at right angles on a moving coast. object or fluid. The force is proportional to the speed Embayment - a shoreline indentation that forms an open and latitude of the object, is zero at the equator and a bay. maximum at either pole for a fixed speed. Entrainment - the process by which relativelv high-den- Cotidal line - a line joining regions with simultaneous sity fluid is incorporated into an overlying layer of less occurrence of high water. Synonymous with cophase dense fluid as a result of breaking wavelike disturbances line. or turbulent motions at the interface between the flu- Countercurrent - a surface current parallel to, but setting ids. In an estuary, entrainment produces at net trans- in the opposite direction to, the main current. port ofsalt from the saline ocean water to the overlying Crust - see Lithosphere. brackish layer. Cusp - one of a series of low mounds of beach material Epicenter - the point on the earth's surface directly above separated by crescent-shaped troughs spaced at the point of origin (focus) of an earthquake. roughly equal intends along a beach. Equilibn'um the09 - a model of the tide that assumes a Cyclonic - a sense of rotation in the same sense as that of continuous ocean of uniform depth over the earth in the earth's; counterclockwise in the northern hemi- which the water responds instantl!r to the tide-generat- sphere and clockwise in the southern hemisphere. ing ofthe and moon. Land masses, bottom friction, and inertia are ignored in the model. Equilibrium tide - the hypothetical tide generated by the tidegenerating forces in the equilibrium theory of the - the time for one rotation of the earth. There are Day tide. Also called the gravitational tide or astronomical different types of day depending on whether the sun, tide. moon, or a star is used as the point of reference for the rotation; solar day (24 h), lunar day (24.84 h), and sidereal day (23.93 h), respectively. Fan - a relatively smooth, fan-shaped feature that nor- Dead water - the condition whereby a vessel expends mall\i slopes away from the lower termination of a considerable propulsive power in the generation of an canyon or canyon system. Also, deep-sea fan and sub- internal wake as it travels in a region with a shallow marine fan. brackish layer overlying a deeper more saline layer. Fault - a fracture or in rock along which Declination - the angle that the sun, moon, or other relative movement of opposing sides has occurred. celestial object subtents with the plane of the earth's Fetch - the area of the ocean surface where are equator. generated by a wind with nearly constant direction and Density - the ratio of the mass of any substance to the speed. Also, the spatial extent of this area measured in volume it occupies. Typical ocean water has in the wind direction. the approximate range of 1.020-1.028 g/cm3. Flocculation - the process by which fine particles of clay - a single-celled plant (phytoplankton) covered suspended in fresh water aggregate into lumps on con- with two overlapping porous shells of silica. tact with salt water and settle out of suspension; a are one of the most abundant marine organisms and a depositional mechanism common to estuarine regions. primary source of food in the sea. Fracture zone - an extensive linear zone of irregular Dispenion - the separation of a group (or packet) of seafloor topography characterized by steep-sided or waves into component parts due to differences in prop- asymmetrical ridges, troughs, or escarpments. agation speeds of the waves. Frequency - a measure of the number of oscillations or Diurnal - meaning daily and pertaining to motions cycles per unit time; the reciprocal ofthe time duration which complete a cyclic pattern every solar or lunar day. (period) of an oscillation. (A wall outlet in North Dnjit current - a broad, slow principally America for example, has a voltage oscillation fre- driven by the large-scale winds. quency of 60 cycles/s.) Drogue - a current measuring device with sufficient sub- Frictional drad - the retarding force exerted on a fluid surface area and depth penetration to be mainly carried moving relative to a solid surface or to another region by the oceanic current rather than by the effects of of fluid as a result of momentum exchange processes. winds and waves. The momentum exchange can arise through molecular motions or through eddylike motions. (See Laminar floy Turbulent flow) - cyclic displacement of the earth's crust Front - a comparatively sharp horizontal transition be- caused by the tide-generating forces of the sun and tween two fluids of different density generally accom- moon. panied by a change in flow velocity. Atmospheric fronts - a quasi-circular movement of water, of relatively are delineated by changes in , oceanic small area, formed in the lee of obstructions or along fronts by changes in temperature and/or salinity.

- 250 - GeostrophufEow - currents or winds on length scales that breakwater. Other jetties include sea walls and training exceed approximately 100 km where the horizontal walls. gradient is exactly balanced by the . Glacwmarine - pertaining to unsorted and nonlayered Kinetic energy - the energy of an object or parcel of fluid marine sediments, generally unconsolidated, deposited by virtue of its motion. Kinetic energy is proportional by or underneath a glacier. to mass and the square of the speed. Granite - a coarse-grained igneous rock of mainly feld- Knoll - a relatively small, isolated elevation of a rounded spar and quartz comprising a significant portion of the shape on the seafloor. upper continental crust. Gyre - a large oceanic region of closed or nearly closed horizontal circulation. In the northern hemisphere Larninavjow - a flow in which the fluid moves smoothly cyclonic gyres exhibit a net divergence, anticyclonic and in parallel layers. Laminar flow over solid surfaces gyres a net convergence of surface waters. conforms to the general topography. (Opposite to Tur- bulent Aow) Land breeze - a generally light wind that blows seaward Halocline - a layer characterized by a sharp increase in due to greater cooling of the land than water. salinity with depth. In the North Pacific Ocean, there is Larva (plural larvae) - the young, self-sustaining and a permanent halocline at 100-200 m. independent stage of an animal's life cycle prior to Heat capacity - the ratio of the heat absorbed (or re- assuming the characteristics of the parents. leased) by a fluid to the corresponding temperature rise Lee wave - a type of formed downstream (or fall). For example, 1 cal is required to raise the (i.e. in the lee) of a topographic feature such as a sill or, temperature of 1 g of liquid water by 1c" so the heat in the case of the atmosphere, a hill or mountain range. capacity is 1.0 caVg C"; for ice the value is 0.55 caVg C". Lithosphere -the solid outer portion of the earth's surface Homogeneous fluid - a fluid with a spatially uniform above the asthenosphere (mantle). Oceanic density. lithospheres have an average thickness of 5-7 km, Hydraulic current - a current produced in a channel by a continental lithospheres an average thickness of 35 km. difference in water elevation (hydraulic head) at the Littoral (intertidal) - of or pertaining to the seashore. ends. May be due to a difference in the range or time of Commonly, that part of the between the the tide in the water bodies that the channel connects. high- and low-water levels. see Hydraulic jump - Bore. Littoral current - any current in the that Hydrocarbon - organic compounds composed of hydro- flows parallel to shore and usually driven by breakmg gen and carbon; natural gas and petroleum are com- waves. Synonymous here with longshore current. mon examples. Littoral drzft - the material transported in the littoral zone by a littoral current. Littoralzone -according to beach terminology, the indef- ZBneous rock - rock formed at the earth's surface when inite zone that extends from the shoreline to just molten material cools. (see Magma) beyond the breaker zone. In biological it Znterjace - a surface separating two fluids across which is part of the benthic region from the high-water line to there is an abrupt change in temperature, salinity, or 200 m depth. density. Longshore current - (see Littoral current) -a long subsurface wave of mainly semidiur- nal period generated within the body of an oceanic region or contiguous channel through the interaction of the astr,onomical tide with the bottom topography. Magma - molten rock under the earth's surface from Zso- - prefix meaning alike, equal, or same; from the which igneous rock is derived by solidification. Magma Greek word isos: equal. extruded onto the earth's surface is called lava. Isobar - A line that connects points of equal pressure. Magnetic anomaly - a distortion of the normal configura- Zsohaline - a line that connects points of equal salinity. tion of the earth's magnetic field resulting from local Isotherm - a line that connects points of equal concentrations of ferromagnetic materials. temperature. Magnetic domain - a small region in a ferromagnetic material where, because of molecular interactions, the individual molecular magnets are all aligned parallel to Japan Current - a popular, but not recommended, name one another. The directions of magnetization in dif- for the Kuroshio that flows northeastward over the ferent domains are not necessarily the same as neigh- continental slope off Japan. Also an incorrectly used boring domains. In an unmagnetized specimen, name for the eastward setting Subarctic Current. domains arc randomly oriented and the resultant mag- Jeny - a structure that extends into a netization is zero. designed to direct and confine the current and to pre- Mantle - (see Asthenosphere). vent shoaling of a channel due to littoral drift. A jetty Maritime climate - a regional climate under the predomi- projecting seaward to retard coastal erosion is called a nant influence of the ocean, and1 characterized by small ; a jetty brealung the wave force is called a diurnal and annual ranges in air temperature.

- 251 - Manh (salt manh) - a flat, vcgctatcd area at or above the cffccts include modifications of winds and rainfall bv high-water mark that is flooded by spring or the presence of mountain ranges. during storm surges. Vsmsis - the movement of molecules or ions across a Meteorological tide - the variation in water Icvcl due to selectively semi-permeable membrane. meteorological cffccts such as winds and atmospheric Osmoticpressure - the pressure cxcrtcd on a membrane as pressure. a result of the difyercncc in chemical in - the surfacc layer ofa body of water mixed to the fluids on either side. near homogeneity by wind-\vavc action or by con- OiwtoppiFtq - the flow of water over a natural or man- vective overturning. Mixed layers can also be created made structure due to \va~run-up or a surge. above the bottom through the action of turbulent Oxygen, dissohwd- oxygen gas that has dissolved in water. motions. The concentration of dissolved oxvgcn in the sea at Mollusk - a soft-bodied, unscgmcnted animal with gills normal and typically lies be- and commonly protected by a calcareous shell. In- nvecn 0 and 8 mL/L; the concentration at saturation cludes snails, squid, , and clams. decreases with increasing temperature and salinity. In Momentum - property of a moving fluid that is propor- the Northeast Pacific Ocean, osvgcn Icvcls decrease tional to the product of its muss times velocity. A force rapidly with depth beneath tlie permanent halocline to is required to change the momentum of a fluid; sim- a minimum of 1 mL/L or less around 1500 m then ilarly, a fluid will produce a force if it imparts monicn- gradually increase with depth. tum to an object or another parcel of fluid. Month - period of the moon’s orbit around the earth. Types of month include sidereal, anomalistic, and syn- PalcomaLqiictisnz- the remnant of the earth’s ancient mag- odical depending on whether the period of revolution netism retained during the initial formation of a is measured relative to a fixed star, perigee, or the sLiti. material. The calendar month is a rough approximation to the Paleoiitolofiil - the studv of ancient life bv fossil evidence. s!modical mo1ith. Pc~~colatioii- the proccsscs by which \\&e morions force Mud pat - a muddv or sandy coastal strip often sub- water into the spaces between bottom sediments. merged at high tidc. Pcrcqec - tlic position in the moon’s orbit that is tiearest the earth. (opposite to Apogee) pH - a measure of the alkalinity or acidity of a Natura1fi.equeiiq(rcsoriniitJicqtrcnc~ - the frcquencv, or based on the concentration of the hydrogen ion. A pH set of discrete frequencies, of oscillation in a body of value of 7 indicates a neutral solution, less than 7 is water determined by the physical characteristics of the acidic, and greater than 7 is alkaline. basin such as its depth, shape, dimensions, and density PI?ilsiopzph? - the description of the features and phc- structure. in semicncloscd embaymciits or har- nomcna of nature; the science that deals with the na- bors typically attain maximum amplitudes at an integer ture and origin of the earth’s topographic features. number of frcqucncics that arc naturally tuned to the Piiinmle - any high tower or spire-shaped pillar of rock, frequency of the cxtcrtial mechanism that cause the or , alone or cresting a summit. displacements. Plankton -drifting marine organisms with limited swim- Noblegas (inertgas) -any group ofrarc gases that include ming capability; include microscopic phytoplankton helium, neon, argon, krypton, and xenon and exhibit and zooplankton as \vel1 as certain macroscopic organ- grcat stability and extremely low chcmical reaction isms, such as . rates. Plastic material - a material that can be deformed contin- Node (also iiocid he,iiuc1;1/puiiir) - the position or line uously and permanently in any dircctioti without rup- in an oscillating region of water where the motions are ture through application of pressure. a niiiiimum or nonexistent. For a standing \vavc, vcrti- Plume - the sediment suspension carried by fresh water cal displacements arc least and horizontal current grcat- that flows out over the surface of a region OfSalh\iatCr. est at a nodal point. (see Ampfiidromic poiiir) Polar oztt6reab - the seaward flow of cold, dry, stable air Noiztidal current- the contribution to the net current at a along inlets subsequent to its formation over high particular location not directly caused by the tidc- altitude continental land masses. generating forces of the sun and moon (Synonymous Potential enegv - a stored form ofenergy associated with with Residual c~~r-rciir) the displacement of a fluid from its equilibrium or Nutrient - a chemical compound needed for the growth undisturbed level. of marine plants. Pvevailing - pertaining to the wind or current most commonly observed during a specified period, such as a month or season. Ocean (meather)station - a specifically located area ofthc Primordial- of or related to the beginning or initial times ocean surface roughly 200 nm on a side. Ocean of the earth’s history. weather ships arc equipped to obtain comprehensive Promorztov - a high point of land that projects into a meteorological anci oceanographic observations at bodv of water; a headland. these stations. i Propagntion ofivaves - the transmission of waves through Orcqraphic - of or pertaining to mountains. Orographic a fluid.

- 252 - Province - a region identifiable by a group of similar Sidereal month - the average period of the moon’s orbit physiographic features whose characteristics differ around the earth with respect to a fixed star. One markedly with surrounding areas; example, sidereal month equals 27.32 mean solar days. province. Solitay wave - an isolated wave crest in the form of a - a zone of comparatively rapid change in traveling mound of water, whose amplitude may be density with depth. comparable to the water depth, and not accompanied by a preceding or trailing trough. Also, a wave of translation in which the water parcels move only in the direction of wave advance. Rectilinear current (reversing currcnt) - a time varying current such as a tidal current, which flows Stability - the resistance to overturn or mixing in a alternatively in roughly opposite directions with a slack column of water. Stability increases with increased water at each reversal in direction. Found in confined and with decreased vertical change in cur- channels, , or passes. rent velocity with depth. - rocks near or at the surface that may constitute a Stratijcation - the condition in which a column of water to navigation. is layered, continuously or in abrupt steps, according to Residual current - (see Non tidal current) density with lighter water overlying heavier water. Synodical month - the average period of the moon’s orbit Resonance - a condition of wave amplification that arises when the oscillation frequency of the applied force on a around the earth with respect to the sun, or the time system matches the frequency of the particular wave or between identical lunar phases. One synodical month basin oscillation on which the force is acting. equals 29.53 mean solar days. Ridge - a long, narrow elevation with steep sides that often separates ocean basins as part of the major oceanic mountain systems with global extent. Terrace - a level or nearly level topographic feature on a R$ - a turbulent agitation of the water produced by steeper slope e.g. a relict beach terrace on the side of a opposing waves and currents or by rapid flow over an seamount. irregular bottom. Often called tide rips in regions Thennocline - a layer that marks a sharp change in tem- where currents are predominantly tidal in nature. perature with depth. In the ocean, there are short-lived, Rocky intertidal plafomz - a flat or gently sloping wave- transient , seasonal (temporary) ther- eroded platform in the lower foreshore zone on a rocky moclines, and permanent thermoclines. coast. - a tidal wave that advances up a relatively Rotary current - a current that flows continually, partly shallow and sloping estuary in the form of a solitary or wholly unrestricted by coastal boundaries, and wave. (see Bore) which changes direction through all points of the com- Tidal current - the cyclic horizontal flow of water associ- pass during a single cycle. ated with the combination ofthe tidal and more slowly varying residual (or nontidal) currents. Tidalpats - an area of marshy, muddy, or sandy land that Salinity - the quantity of dissolved salts in in is inundated by the tide. Tidal stream - the cyclic horizontal flow of water pro- parts per thousand (%o) by weight. duced solely by tide-generating forces of the moon and Saltation - a form of sand transport in a fluid when sun. The horizontal component associated with the rise individual particles bounce off the bed and are carried some distance downstream before again sinlung to the and fall of the tide. (Called tidal current in the United States). bottom. Tidal wave - a long, propagating shallow-water wave of Sea breeze - a light to moderate wind that blows toward tidal period generated by tide-generating forces and the land caused by greater heating of land than water. Sea fog - an advection-type fog produced when relatively modified by the Coriolis force, bottom friction, and moist air is transported from a region of warm surface seafloor topography. A misnomer for and storm surge. waters to one of cooler surface waters, leading to con- current - a dense, fast flowing current of sedi- densation of the lower layer of air. ment-laden water that moves down a slope. Sea stack - a tall, columnar rock separated from the coast by differential wave erosion. Turbulence - a state of fluid motion with irregular and random fluctuations that is describable only in terms of Semidaumal - pertaining to motions that undergo a variation of one cycle once every half lunar day. its statistics. Turbulent motions provide a more intense Set-up -elevation of the water surface above normal level mechanism for the redistribution of momentum, en- due to an onshore transport of water by wave action ergy, and suspended material than the slow molecular processes. (wave set-up) or directly by wind-induced flow (wind - a flow of significant irregular and ran- set-up). Turbulentpow dom motions, usually superimposed on a more Shingle - well rounded, often flat, waterworn pebbles larger than about 16 mm. organized flow pattern. Shore - the narrow strip of land immediately adjacent to and contacting the sea, including the tidal zone. A beach is a shore formed of unconsolidated material. Undercurrent - a subsurface current typically with a

- 253 - different speed and direction from the prevailing sur- Viscous damping - the attenuation of a fluid oscillation face current. due to the fluid's internal friction or viscosity. - a seaward current near the bottom on a sloping inshore zone, the result of the return of water carried onshore by waves; a common misnomer for rip Water mass -a body ofwatcr characterized by a particular current. (limited) range of temperatures and that al- Up-msh, (, run-up) - the rush of a low it to be distinguishable from surrounding oceanic onto a beach. regions. Wind drift - a large-scale ocean current where the Cor- iolis force and frictional forces are dominant. Also used Vector - a quantity with both magnitude and orientation here to describe a localized, weak, near-surface current relative to a given coordinate system or grid. A current generated by the wind. vector (current velocity) requires both speed and dircc- Wind waves - waves formed and amplified by the wind. tion for complete description. A current vector can be represented by an arrow with the length of the arrow proportional to the speed, and the tip of the arrow Zooplankton - the animal forms of plankton; include pointing in the direction of the flow. jellyfish, worms, mollusks, and a wide variety of other Veering - a change in wind or current direction in a marine animals. The primary grazers of phytoplankton clockwise sense. (opposite to Backing) and, in turn, the principal food for many larger marine Velocit?,- a vector quantity that gives both the speed and animals, such as squid and baleen whales. direction. The rate of change in time of an object's position.

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