05.04.2018: FB1-Seminar

11:00 Uhr, gr. Konferenzraum, Düsternbrooker Weg 20

Like all waves in fluids, internal gravity generally transport mass, vertically and horizontally propagating plane waves in a uniformly stratified fluid being one exception to the rule. I will begin by discussing mass transport, or the lack thereof, in linear waves for which there are two components: Stokes drift and second-order mean flows. I will then progress to internal solitary waves which are capable of transporting mass large distances, a process which has be conjectured to be of importance for biological processes. I will finish with a discussion of internal solitary waves with trapped cores. A trapped core in an idealized internal solitary wave is a core of fluid which is advected by the solitary wave, thereby providing an efficient means to transport fluid and entrained particles many kilometres. In numerical simulations and in observations cores are turbulent and leaky but can still provide and effective transport mechanism. Both surface and subsurface cores can exist, their location depending on the background stratification and, particularly crucial for the subsurface cores, on near surface background vorticity. Large internal solitary waves with sub-surface (O(100) m depth) cores have recently being observed in the South China Sea. Results from simulations aimed at modelling these observed waves will be presented.

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