The percent of the sunís electromagnetic energy reflected by the surface of an object back into space


Seamounts or guyots that have broken the surface with coral deposits built up around the rim

Average wave height

The average height of all the waves present, from the smallest ripple to the largest wave


Temperature versus depth profile

Bergy bit

A medium-sized fragment of glacier ice about the size of a small cottage


Occurs when a landing craft gets turned parallel to the wave train


When the leading edge of a glacier breaks off

Coastal current system

A relatively uniform drift that flows roughly parallel to shore that may be composed of tidal currents, wind-driven currents, or local, density-driven currents

Composite products

Products composed of more than one dayís data


The ability of water to be compacted under pressure

Continental rise

Found seaward of the continental slope, in approximately 500 fathoms of water, made up of thick sediment deposits that cover irregular relief features

Continental shelf

The first province of the five major bottom provinces. The average width of the shelf is approximately 40 miles and comprise about 7.5 percent of the total ocean bottom


Peak or highest part of a wave


The horizontal movement of water

Deep-water layer

The bottom layer of water, below 1,200 meters in the middle latitudes, characterized by fairly constant cold temperatures, generally less than 4įC

Density current

Current caused by density differences, or gravity differences between currents


The speed of a current measured in terms of knots

Duration-limited sea

Occurs when the wind is in contact with the sea for too short a time and it doesnít have enough time to impart the maximum energy to the sea

Ebb tide

A falling, or outgoing, tide

Fast ice

Ice that forms along the shorelines


6 feet

Fetch areas

Areas of constant wind speed and direction over a time

Fetch-limited sea

Occurs when the fetch length is too short and the wind is not in contact with the waves over a distance sufficient to impart the maximum energy to the waves

First-year ice

Reasonably unbroken level of ice of not more than one winterís growth that starts as young ice. The thickness is from 30 centimeters to 2 meters (1 foot to 6 Ĺ feet)

Flood tide

A rising or incoming tide

Forced waves

Waves that are maintained by a periodic force


Any break through sea ice

Frazil crystals

Thin plates of ice on the sea surface

Free waves

Waves caused by a sudden underwater impulse such as seismic activity


The portion of an iceberg above the water

Fully developed sea

When dissipation is equal to input energy and the waves stop growing

Geopotential current

See density current

Grease ice

Sea-surface ice showing a thick soupy consistency


A small fragment of glacier ice about the size of a grand piano


Submerged, isolated, flat-topped mountains rising 3,000 feet or more above the sea floor


Large oval, or circular, currents formed in the ocean basins by the combined effects of the winds, and the position of the continents

Heat budget

The temperature balance established in the ocean between heat gain and heat loss mechanisms

Highest 1/10th wave height

The average height of the highest 1/10th of all waves used to indicate the extreme roughness of the sea

Hummock ice

Ice topography piled haphazardly into mounds or hillocks

Hydraulic currents

Small-scale thermohaline subsurface circulations caused by the differences in sea level between two water bodies

Ice rind

Sea-surface ice showing a brittle crust forming with a shiny appearance

Island arcs

Groups of volcanic islands


Lines of equal water depth


A long, narrow open or refrozen break or passage through sea ice; a navigable fracture



Littoral current

Current occurring in the surf zone caused by waves approaching the beach at an angle

Long waves

Waves that exist in water depths that are less than one-half of their wavelength

Longshore current

See littoral current

Main thermocline

The central layer of the ocean generally between 1,000 and 3,000 feet

Mean range

The difference, in height, between the high tides and the low tides

Mean tide level

The plane between mean low water and mean high water

Mixed layer

The upper layer of the three-layered ocean model

Neap tide

Tide that occurs when the moon is in its first- and third-quarter phases, the sun and the moon are at right angles to each other producing a lower-than-normal high tide and higher-than-normal low tide

Nearshore current system

Composed of shoreward moving water in the form of waves at the surface, a return flow or drift along the bottom in the surf zone, nearshore currents that parallel the beach (longshore or littoral), and rip currents


Sea-surface ice showing an elastic crust forming with a matte appearance

Ocean basin

Accounts for 76 percent of the ocean floor with depths ranging from 1,500 to 3,000 fathoms

Ocean currents

Organized, coherent belts of water in horizontal motion

Ocean eddies

A circular movement of water formed by the cutting off of meandering currents

Oceanic fronts

Lines of temperature and/or salinity discontinuity between two water masses

Old ice

Extremely heavy sea ice that has survived at least one summerís melt and occurs primarily in the arctic and Antarctic polar packs

Pack ice

Sea ice covering more than half of the visible sea surface

Plunging breakers

Violently breaking waves that gain height rapidly as they first feel the bottom


Any sizable area of sea water enclosed by sea ice

Progressive waves

Waves that are evident by the progressive movement of the wave form


A depression in sea ice usually filled with melted water caused by warm weather

Rafted ice

Ice topography that occurs when wind forces ice cakes or ice floes to override one another


Protrusions of ice beneath the surface of irregular icebergs


The bending of a wave that occurs when one portion of the wave moves slower than another portion

Ridged ice

Ice topography that is much rougher than rafted ice and occurs with first-year ice

Rip currents

Current caused by the return flow of water from the beach


The total amount of dissolved solids in sea water

Sea waves

A complicated mix of superimposed waves and ripples that develop in a storm


Submerged, isolated, pinnacled mountains rising 3,000 feet or more above the sea floor

Seismic wave

A wave generated by a submarine (underwater) earthquake or volcanic event commonly called tsunamis


The direction in which the current is moving (toward)

Shelf break

Located at the seaward edge of the continental shelf with an average slant ratio roughly 20 times greater than that of the continental shelf

Short waves

Waves that exist in water depths greater than one-half of the wavelength

Significant wave height

The average height of the highest 1/3rd of all the waves present


Elevated parts of the ocean floor that partially separate ocean basins restricting the movement of bottom water masses resulting in their partial, and in some cases nearly total, isolation

Slack water

The period between an ebb tide and a flood tide when there is no appreciable horizontal movement of water


The ability to dissolve other substances

Specific heat

The amount of heat needed to raise the temperature of one gram of a substance 1Cį


Minute ice needles on the sea surface

Spilling breakers

Waves that break very gradually as they move through the surf zone

Spring range

The annual average of the highest semi-diurnal range, which occurs twice a month, when the moon is in its new or full phase

Spring tide

Tide that occurs when the moon is in its new and full phases and the high tides are higher than normal and the low tides are lower than normal


The period between an ebb tide and a flood tide when there is no appreciable vertical movement of water

Standing waves

Waves made up of two progressive waves traveling in opposite directions

Steady state

Occurs when all the windís energy is imparted to the sea within the fetch

Storm surges

Occurs when tropical storms generating strong winds and low central pressures raise the sea level just before coming ashore


Swell that breaks on the shore

Surf boarding

Occurs when a craft is overtaken by a spilling breaker that carries the craft along, causing it to get out of control, broach, collide with another craft or hit some personnel

Surf zone

The horizontal distance in yards or feet between the outer most breaker and the limit of wave uprush on the beach

Surface tension

The ability to support heavier objects

Surging breakers

Waves that increase in height very slowly, the crest peaks but does NOT break as with other types, instead it continues to move up on to the beach


Occurs when a craft is overtaken by a plunging breaker, and the wave "breaks" into and/or over the craft, causing it to fill with water, sink, turn over, shift out of position, or incur some other hazardous ordeal

Swell waves

Long, smooth, regular waves outside the generating area

Swell waves

Occurs as wind waves move beyond the fetch or when the wind over the fetch dies off


See guyot

Thaw holes

Holes in sea ice that are caused by the melting associated with warm weather


The part of the ocean where temperature decreases rapidly with depth

Tidal current

The horizontal movement of water caused by tide changes

Tidal day

The daily tidal effect caused by the moon revolving around earth once every 24 hours and 50 minutes

Tidal range

The changes or difference in feet between high tide and low tide


Gravitational waves that have lengths in hundreds of miles and heights ranging up to 50 feet and are a consequence of the simultaneous action of the moonís, the sunís, and the earthís gravitational forces, and the revolution about one another


Long, narrow, and relatively steep-sided depressions that comprise the deepest portions of the oceans normally found on the seaward side of island arcs


Lull or lowest part of a wave


The rising of water toward the surface from subsurface layers of a body of water


Resistance to flow

Wave amplitude

One-half of the wave height, or the vertical displacement of a particle from the "at rest" position (sea level), to the top of the wave crest or base of the trough

Wave frequency

The number of waves passing a given point during a one-second interval

Wave period

The time interval between successive wave crests or troughs as they pass a fixed point

Wave speed

The rate at which the wave moves through the water measured in knots


The horizontal distance between two successive crests or troughs

Wind waves

Waves which result from the energy of the wind being imparted to the sea

Wind-driven current

Current initiated and sustained by the force of the wind exerting stress on the sea surface

Young ice

Ice that forms in one year or less with a thickness range from 10 to 30 centimeters (4 to 12 inches)



Abbreviations and Acronyms


Symbol denoting the measurement of salinity in parts per thousand by weight


Area of operations


Antisubmarine warfare


Automatic Digital Network


Wave speed




Combined wave height


Extremely low frequency


Wave frequency


Forward looking infrared forecast


Fleet Numerical Meteorology and Oceanography Center


Geophysics Fleet Mission Program Library






International Tsunami Warning System




Kilometer per hour




Layer depth




Meteorological satellite


Mixed-layer depth


Mobile Oceanography Support Facility


Mile per hour


Naval Eastern Oceanography Center


Naval Oceanography Command


Naval Oceanographic Office


Naval Polar Oceanography Center


Naval Western Oceanography Center


Nautical mile


Navy Oceanographic Data Distribution System


Naval Operational Global Atmospheric Prediction System


Naval Operational Regional Atmospheric Prediction System


Operational area


Optimum Path Aircraft Routing System


Sea-surface temperature


Swell waves


Wave period


Tactical Environmental Support System


Wind waves