EGU22-6715
https://doi.org/10.5194/egusphere-egu22-6715
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tide-topography interactions: the influence of an along-shelf current on the internal wave spectrum

Yangxin He and Kevin Lamb
Yangxin He and Kevin Lamb
  • University of Waterloo, Waterloo, Canada (y67he@uwaterloo.ca)

We investigate the influence of a barotropic geostrophic current on
the internal wave (IW) generation over a shelf slope.
It is well known that most of the energy in the tide-topography
generated waves lies in waves with tidal frequency $\sigma_T$. 
Here we restrict our attention on the frequencies other than the dominant frequency $\sigma_T$. 
The current $V_g(x)$ is modeled as an idealized Gaussian function centered at
$x_0$ with width $x_r$ and maximum velocity $V_{max}$.
The bathymetry is modelled as a linear slope with smoothed corners.
Since the center of the current lies on the slope, there will always
be a region on the slope where the effective frequency $f_{eff}$ is
greater than the Coriolis parameter $f$ and another region where
$f_{eff} < f$. Parametric subharmonic instability (PSI) occurs where
waves with approximately half of the primary wave frequency, in this
case $\sigma_T/2$, are generated. In the presence of a large current,
PSI can occur where $f_{eff} < \sigma_T/2 < f$. This could not
happen without a current, i.e. $f_{eff} = f > \sigma_T/2$. Other interesting
interactions, including interharmonics and strong tidal harmonics, are also observed.

How to cite: He, Y. and Lamb, K.: Tide-topography interactions: the influence of an along-shelf current on the internal wave spectrum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6715, https://doi.org/10.5194/egusphere-egu22-6715, 2022.