Editing Wave base

{{Short description|Maximum depth at which a water wave's passage causes significant water motion}}
[[Image:wavebase.jpg|325px|thumb|right|'''Wave base''' diagram.]]
The '''wave base''', in [[physical oceanography]], is the maximum depth at which a [[water wave]]'s passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the [[seafloor]] are no longer stirred by the wave motion above.<ref name="mechanics">{{cite book | title=Water wave mechanics for engineers and scientists | author=R. G. Dean | author2=R. A. Dalrymple | name-list-style=amp | year=1991 | series=Advanced Series on Ocean Engineering | volume=2 | publisher=World Scientific, Singapore | isbn=978-981-02-0420-4 }}</ref>

==Process==
In [[seawater]], the water particles are moved in a circular [[orbital motion]] when a wave passes. The [[radius]] of the circle of motion for any given water molecule decreases [[Exponential decay|exponentially]] with increasing depth. The wave base, which is the depth of influence of a water wave, is about half the [[wavelength]].

At depths greater than half the wavelength, the water motion is less than 4% of its value at the water surface<ref>At a depth of half the wave length, the [[amplitude]] of the water particle motion by the waves has been reduced to ''e<sup>−π</sup> ≈ 0.04'' times it value at the water surface.</ref> and may be neglected.

For example, in a pool of water {{convert|1|m|ft}} deep, a wave with a {{convert|3|m|ft}} wavelength would be moving the water at the bottom. In the same pool, a wave with a wavelength of {{convert|0.5|m|ft}} 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).<ref name="mechanics"/>

The fair weather wave base refers to the depth beneath the waves under normal conditions and the portion of the [[seafloor]] that is agitated by this everyday wave action, known as the [[Upper shoreface]].

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]].

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.'' <ref>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</ref>)

==See also==
*[[Upper shoreface]] — ''above wave base''
*[[Lower shoreface]] — ''below wave base''
*[[Airy wave theory]]
*[[Dispersion (water waves)]]
*[[Waves and shallow water]]

==References==
{{reflist}}

{{physical oceanography|state=open}}

[[Category:Water waves]]
[[Category:Wave mechanics]]
[[Category:Physical oceanography]]