Tidal diffusivity: A mechanism for frontogenesis

Publication Type  Journal Article
Year of Publication  2003
Authors  Ou, H. W.; Dong, C. M.; Chen, D.
Journal Title  Journal of Physical Oceanography
Volume  33
Issue  4
Pages  840-847
Journal Date  Apr
ISBN Number  0022-3670
Accession Number  ISI:000181851100011
Key Words  georges bank; shelfbreak front; currents; variability; dispersion; flux
Abstract  

It is hypothesized that tidal mixing may provide a "diffusivity'' mechanism for frontogenesis. It stems from the fact that tidal diffusivity varies in the opposite sense from the water depth, so the vertically integrated diffusivity may exhibit a minimum at midshelf, thus giving rise to a maximum in the property gradient-even in the absence of flow convergence. An analytical model assuming a tidal diffusivity dominated by shear dispersion is used to elucidate the mechanism, which shows additionally that the front is located at a water depth that is about twice the tidal frictional depth-a prediction not inconsistent with some observed fronts. The proposed frontogenesis is demonstrated by numerical calculations using the Princeton Ocean Model (POM), which show the emergence of a front from an initial field of uniform gradient after tides are switched on, and the diagnosis of the numerical solution and its parameter dependence has corroborated the analytical model. It is suggested moreover that this diffusivity mechanism may be extended to the wind-induced mixing to explain the shelfbreak front off of the northeastern United States.

Notes  

660UCTimes Cited:2Cited References Count:23

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