Continental shelf waves

Coastal Trapped Waves and Continental Shelf Waves... 

When the width of the shelf is much larger than the baroclinic Rossby radius, the mixed modes become quasi-barotropic (Huthnance, 1978) and stratification follows the barotropic motions of the waves passively without having an impact on the properties of these waves, which are denoted as Continental Shelf Waves (CWS). 

The controls on carbon dioxide would have been somewhat different. Today, carbon dioxide is stored in carbonate minerals in the ocean floor and on the continental shelf. Subduction, followed by volcanism, cycles the carbon dioxide to the mantle and then restores the CO2 to the air. Metamorphic decarbonation of the lower crust also returns carbon dioxide. The carbon dioxide is then cycled back to the water, some via rain, some dissolved via wave bubbles. Erosion provides calcium and magnesium, eventually to precipitate the carbonate. In the earliest Archean, parts of this cycle may have been inefficient. The continental supply of calcium may have been limited however, subseafloor hydrothermal systems would have been vigorous and abundant, exchanging sodium for calcium in spilitization reactions, and hence providing calcium for in situ precipitation in oceanic crust. 

Brink, K. H., 1991. Coastal-trapped waves and wind-driven currents overthe continental shelf Annual Review of Fluid Mechanics, 23, 389-410. 

Emergent shorelines expose shore-adjacent portions of the continental shelf which have become coastal belts. Rapid coastal emergence, common in formerly glaciated areas that presently rebound and in places of coastal faulting and volcanic activity, results in wave-abraded scarped and cliffy shores. Many shorelines have dominant characteristics of more than one of the above subdivisions. 

Huthnance, J.M. 1981. Waves and currents near the continental shelf edge. Progress in Oceanography, 10 193-226. 

When a tsunami is generated in or near the continental shelf, it will have many wave components of differing frequendes. For a local tsunami, the dominant wave period will be from 3 to 20 minutes. For a distant tsunami, the dominant wave period is usually longer than 30 minutes because shorter period components of the wave train are damped out during the travel for long distances over the ocean. 

As the tsunamis propagate over a continental shelf and approach a coastal area, the dispersion effect of waves becomes weak, and the nonlinearity and bottom fi-iction of waves dominantly influence the transformation of the tsimamis. However, the linear Boussinesq-type wave equation does not include the nonlinear and bottom friction terms. Thus, the nonlinear shallow-water equations (NSWE) are employed for the near-field transformation of tsunamis. 

Mean grain size diameter versus compressional wave (sound) velocity in samples from the continental terrace (shelf and slope). (Reproduced with permission from Hamilton, E.L., and Bachman, R.T., /. Acoust. Soc. Am., 72, 1939-1957 1982. Copyright 1982 Acoustic Society of America.)... 

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