Editing Internal wave (section)

==Onshore transport of planktonic larvae==
Cross-shelf transport, the exchange of water between coastal and offshore environments, is of particular interest for its role in delivering [[meroplankton]]ic [[larva]]e to often disparate adult populations from shared offshore larval pools.<ref>Botsford LW, Moloney CL, Hastings A, Largier JL, Powell TM, Higgins K, Quinn JF (1994) The influence of spatially and temporally varying oceanographic conditions on meroplanktonic metapopulations. Deep-Sea Research Part II 41:107–145</ref> Several mechanisms have been proposed for the cross-shelf of planktonic larvae by internal waves. The prevalence of each type of event depends on a variety of factors including bottom topography, stratification of the water body, and tidal influences.

===Internal tidal bores===
Similarly to surface waves, internal waves change as they approach the shore. As the ratio of wave amplitude to water depth becomes such that the wave “feels the bottom,” water at the base of the wave slows down due to friction with the sea floor. This causes the wave to become asymmetrical and the face of the wave to steepen, and finally the wave will break, propagating forward as an internal bore.<ref>Defant A (1961) Physical Oceanography, 2nd edn. Pergamon Press, New York</ref><ref>Cairns JL (1967) Asymmetry of internal tidal waves in shallow coastal waters. Journal of Geophysical Research 72:3563–3565</ref> Internal waves are often formed as tides pass over a shelf break.<ref>Rattray MJ (1960) On coastal generation of internal tides. Tellus 12:54–62</ref> The largest of these waves are generated during [[spring tide|springtides]] and those of sufficient magnitude break and progress across the shelf as bores.<ref>Winant CD, Olson JR (1976) The vertical structure of coastal currents. Deep-Sea Research 23:925–936</ref><ref name="Winant CD 1980">Winant CD (1980) Downwelling over the Southern California shelf. Journal of Physical Oceanography 10:791–799</ref> These bores are evidenced by rapid, step-like changes in temperature and salinity with depth, the abrupt onset of upslope flows near the bottom and packets of high frequency internal waves following the fronts of the bores.<ref>Shanks AL (1995) Mechanisms of cross-shelf dispersal of larval invertebrates and fish. In: McEdward L (ed) Ecology of marine invertebrate larvae. CRC Press, Boca Raton, FL, p 323–336</ref>

The arrival of cool, formerly deep water associated with internal bores into warm, shallower waters corresponds with drastic increases in [[phytoplankton]] and [[zooplankton]] concentrations and changes in plankter species abundances.<ref name="Leichter JJ 1998">Leichter JJ, Shellenbarger G, Genovese SJ, Wing SR (1998) Breaking internal waves on a Florida (USA) coral reef: a plankton pump at work? Marine Ecology Progress Series 166:83–97</ref> Additionally, while both surface waters and those at depth tend to have relatively low primary productivity, [[thermocline]]s are often associated with a [[chlorophyll]] maximum layer. These layers in turn attract large aggregations of mobile zooplankton<ref name="Mann KH 1991">Mann KH, Lazier JRN (1991) Dynamics of marine ecosystems. Blackwell, Boston</ref> that internal bores subsequently push inshore. Many taxa can be almost absent in warm surface waters, yet plentiful in these internal bores.<ref name="Leichter JJ 1998"/>

===Surface slicks===
While internal waves of higher magnitudes will often break after crossing over the shelf break, smaller trains will proceed across the shelf unbroken.<ref name="Winant CD 1980"/><ref>Cairns JL (1968) Thermocline strength fluctuations in coastal waters. Journal of Geophysical Research 73:2591–2595</ref> At low wind speeds these internal waves are evidenced by the formation of wide surface slicks, oriented parallel to the bottom topography, which progress shoreward with the internal waves.<ref name="Ewing G 1950">Ewing G (1950) Slicks, surface films and internal waves. [[Journal of Marine Research]] 9:161–187</ref><ref>LaFond EC (1959) Sea surface features and internal waves in the sea. Indian Journal of Meteorology and Geophysics 10:415–419</ref> Waters above an internal wave converge and sink in its trough and upwell and diverge over its crest.<ref name="Ewing G 1950"/> The convergence zones associated with internal wave troughs often accumulate oils and [[flotsam]] that occasionally progress shoreward with the slicks.<ref>Arthur RS (1954) Oscillations in sea temperature at Scripps and Oceanside piers. Deep-Sea Research 2:129–143</ref><ref name="Shanks AL 1983">Shanks AL (1983) Surface slicks associated with tidally forces internal waves may transport pelagic larvae of benthic invertebrates and fishes shoreward. Marine Ecology Progress Series 13:311–315</ref> These rafts of flotsam can also harbor high concentrations of larvae of [[invertebrates]] and fish an order of magnitude higher than the surrounding waters.<ref name="Shanks AL 1983"/>

===Predictable downwellings===
Thermoclines are often associated with chlorophyll maximum layers.<ref name="Mann KH 1991"/> Internal waves represent oscillations of these thermoclines and therefore have the potential to transfer these phytoplankton rich waters downward, coupling [[benthic]] and [[pelagic]] systems.<ref>Haury LR, Brisco MG, Orr MH (1979) Tidally generated internal wave packets in Massachusetts Bay. Nature 278:312–317</ref><ref>Haury LR, Wiebe PH, Orr MH, Brisco MG (1983) Tidally generated high-frequency internal wave-packets and their effects on plankton in Massachusetts Bay. [[Journal of Marine Research]] 41:65–112</ref> Areas affected by these events show higher growth rates of suspension feeding [[ascidiacea|ascidians]] and [[bryozoa]]ns, likely due to the periodic influx of high phytoplankton concentrations.<ref>Witman JD, Leichter JJ, Genovese SJ, Brooks DA (1993) Pulsed Phytoplankton Supply to the Rocky Subtidal Zone: Influence of Internal Waves. Proceedings of the National Academy of Sciences 90:1686–1690</ref> Periodic depression of the thermocline and associated downwelling may also play an important role in the vertical transport of planktonic larvae.

===Trapped cores===
Large steep internal waves containing trapped, reverse-oscillating cores can also transport parcels of water shoreward.<ref name="Scotti A 2004">Scotti A, Pineda J (2004) Observation of very large and steep internal waves of elevation near the Massachusetts coast. Geophysical Research Letters 31:1–5</ref> These non-linear waves with trapped cores had previously been observed in the laboratory<ref>Manasseh R, Chin CY, Fernando HJ (1998) The transition from density-driven to wave-dominated isolated flows. Journal of Fluid Mechanics 361:253–274</ref> and predicted theoretically.<ref>Derzho OG, Grimshaw R (1997) Solitary waves with a vortex core in a shallow layer of stratified fluid. Physics of Fluids 9:3378–3385</ref> These waves propagate in environments characterized by high [[shear (fluid)|shear]] and [[turbulence]] and likely derive their energy from waves of depression interacting with a shoaling bottom further upstream.<ref name="Scotti A 2004"/> The conditions favorable to the generation of these waves are also likely to suspend sediment along the bottom as well as plankton and nutrients found along the benthos in deeper water.