The wave base, in

physical oceanography Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters. Physical oceanography is one of several sub-domains into which oceanography is divi ...

, is the maximum depth at which a

water wave In fluid dynamics, a wind wave, water wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result from the wind blowing over the water surface. The contact distance in the direction of t ...

's passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the

seafloor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

are no longer stirred by the wave motion above.

Process

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

, the water particles are moved in a circular

orbital motion In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

when a wave passes. The

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

of the circle of motion for any given water molecule decreases

exponentially Exponential may refer to any of several mathematical topics related to exponentiation, including: *Exponential function, also: **Matrix exponential, the matrix analogue to the above * Exponential decay, decrease at a rate proportional to value *Exp ...

with increasing depth. The wave base, which is the depth of influence of a water wave, is about half the

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

. At depths greater than half the wavelength, the water motion is less than 4% of its value at the water surface and may be neglected. For example, in a pool of water deep, a wave with a wavelength would be moving the water at the bottom. In the same pool, a wave with a wavelength of would not be able to cause water movement on the bottom.

Distinctions

There are typically two wave bases, the fair weather wave base (FWWB) and the storm wave base (SWB). The fair weather wave base refers to the depth beneath the waves under normal conditions and the portion of the

that is agitated by this everyday wave action, known as the

Upper shoreface Upper Shoreface refers to the portion of the seafloor that is shallow enough to be agitated by everyday wave action, the wave base. Below that is the lower shoreface. Process The continuous agitation of the sea floor in the upper shoreface en ...

. The storm wave base refers to the depths beneath storm-driven waves and can be much deeper. The portion of the seafloor that is only agitated by storm-driven wave action is known as the

Lower shoreface Lower Shoreface refers to the portion of the seafloor, and the sedimentary depositional environment, that lies below the everyday wave base. It is also used for the sandstone sedimentary structure rock formations that were produced by this proce ...

. Note that another classification exists, which considers that the zone affected by both fair weather and storm waves is to be defined as shoreface, whereas ''Upper offshore'' is the name given to the zone only affected by storm waves and ''Lower offshore'' a zone not disturbed by any surface wave. (''e.g.'' Bayetgoll ''et al.'', 2015, Ichnology and sedimentology of a shallow marine Upper Cretaceous depositional system (Neyzar Formation, Kopet-Dagh, Iran): Palaeoceanographic influence on ichnodiversity, ''Cretaceous Research'', 56, 628-646)

Types Of Wave Bases

fair weather base: it is a sea depth of 5 to 15m below sea level where the sea bed is unaffected by the action of waves in the calm wave conditions.

References

{{physical oceanography, state=open Water waves Wave mechanics Physical oceanography

Process

Distinctions

Types Of Wave Bases

See also

References