|Institution:||Jacobs University, Bremen|
|Room:||Research Buidling I, Room 117|
|Phone:||+49 421 200 - 3218|
|Other webpage(s):||Gökce's Jacobs University web page|
The interior energy pathway: internal wave emission by quasi-balanced flows
In this project, we will investigate the function of spontaneous emission and subsequent capture of internal gravity waves (IGW) for interior dissipation in quasi-balanced flows. Energy is transferred in the ocean by dissipation from the essentially balanced large-scale ocean circulation and mesoscale eddy fields down to smaller scales. This transfer takes place with the contribution of spontaneous wave emission and wave capture, which ends with instabilities and small scale turbulence in the ocean.
Most of the studies has only considered spontaneous wave generation in an extent of wave generation mechanism without having any direct relation to future of waves after being emitted. After emission of the waves, it follows that they can be refracted or may be captured. The captured waves are identified as a wave with exponential increase in wave number and wave amplitude while following exponential decrease in intrinsic group velocity.
It has been shown in recent studies that the eddying flows emit IGWs spontaneously. However, the strength of IGW emission depends on the magnitude of Rossby number characterizing the flow. Large value of the Rossby number creates strong IGW emission such as in the equatorial ocean and in the vicinity of strong fronts, while the emission is weak for the smaller Rossby number. In the latter case, the timescales of the background flow and the timescales of the emitted flow split clearly. The emitted IGWs are exponentially small with respect to a function of the Rossby number via exponential asymptotics. The theoretical result via exponential symptotics put forward no sufficiently important wave emission in the interior ocean for consideration in the presence of a small Rossby number; however, it does not emphasize the evolution of emitted waves but only spontaneous emission of waves. It is not known that for which finite value of Rossby number, wave emission can be neglected. Due to subsequent refraction and wave capture affecting all IGWs, the wave with growing wave
amplitude takes a significant role in the ocean.
In this project, we will split the velocity and mass fields into a balanced and an imbalanced flows, which are respectively the quasi-balanced flow field and the emitted IGW field, as one of the fundamental step to be taken, and a careful analysis of IGW activity will be helpful to improve understanding of the subject and to answer the research questions of this project:
- How important is the route to dissipation via spontaneous wave generation and wave capture?
- What are the factors that control the IGW emission?
- Is it possible to characterise the IGW emitted by a turbulent geostrophic flow?
|Prof. Dr. Marcel Oliver||Jacobs University, Bremen|
|Jun.-Prof. Dr. Gualtiero Badin||University of Hamburg|
|Prof. Dr. Sergey Danilov||Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI), Bremerhaven|