Glossary

Terms

Albedo

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

Atolls

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

Bathythermograph

Temperature versus depth profile

Bergy bit

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

Broaching

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

Calve

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

Compressibility

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

Crest

Peak or highest part of a wave

Current

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

Drift

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

Fathom

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

Fracture

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

Freeboard

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

Growler

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

Guyots

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

Gyres

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

Isobaths

Lines of equal water depth

Lead

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

Littoral

Shore

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

Nilís

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

Polynya

Any sizable area of sea water enclosed by sea ice

Progressive waves

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

Puddle

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

Rams

Protrusions of ice beneath the surface of irregular icebergs

Refraction

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

Salinity

The total amount of dissolved solids in sea water

Sea waves

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

Seamounts

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

Set

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

Sills

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

Solvent

The ability to dissolve other substances

Specific heat

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

Spicules

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

Stand

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

Surf

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

Swamping

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

Tablemounts

See guyot

Thaw holes

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

Thermocline

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

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

Trenches

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

Trough

Lull or lowest part of a wave

Upwelling

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

Viscosity

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

Wavelength

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

Č

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

AOA

Area of operations

ASW

Antisubmarine warfare

AUTODIN

Automatic Digital Network

C

Wave speed

cm

Centimeter

Cwh

Combined wave height

ELF

Extremely low frequency

f

Wave frequency

FLIROUT

Forward looking infrared forecast

FNMOC

Fleet Numerical Meteorology and Oceanography Center

GFMPL

Geophysics Fleet Mission Program Library

h

Hour

IR

Infrared

ITWS

International Tsunami Warning System

km

Kilometer

km/hr

Kilometer per hour

L

Wavelength

LD

Layer depth

m

Minute

METSAT

Meteorological satellite

MLD

Mixed-layer depth

MOSS

Mobile Oceanography Support Facility

mph

Mile per hour

NAVEASTOCEANCEN

Naval Eastern Oceanography Center

NAVOCEANCOM

Naval Oceanography Command

NAVOCEANO

Naval Oceanographic Office

NAVPOLAROCEANCEN

Naval Polar Oceanography Center

NAVWESTOCEANCEN

Naval Western Oceanography Center

nm

Nautical mile

NODDS

Navy Oceanographic Data Distribution System

NOGAPS

Naval Operational Global Atmospheric Prediction System

NORAPS

Naval Operational Regional Atmospheric Prediction System

OPAREA

Operational area

OPARS

Optimum Path Aircraft Routing System

SST

Sea-surface temperature

sw

Swell waves

T

Wave period

TESS

Tactical Environmental Support System

ww

Wind waves