Camille Moisset, Bruce Sutherland, and Lois Baker from the University of Alberta have been studying the behavior of internal tides in the ocean, particularly their interaction with equatorial currents. Their research, published in the Journal of Physical Oceanography, sheds light on how these underwater waves, which play a significant role in ocean dynamics and energy redistribution, are affected by equatorial zonal jets.
Internal tides are generated by tidal flow over submarine topography and can travel vast distances across ocean basins. These waves are crucial for deep ocean mixing and energy distribution, which in turn influences global climate patterns. However, satellite observations have shown that the phase coherence of these waves is lost in equatorial regions, affecting our understanding of their dynamics and energy distribution.
To investigate this phenomenon, the researchers developed an idealized linear model using modal decomposition. This model was used to study the dynamics of a mode 1 M2 internal wavepacket on an equatorial beta plane. They introduced a zonal jet at the equator to examine potential wave-mean flow interactions.
The study found that a vertically uniform zonal jet significantly affects the propagation of the mode 1 wavepacket. Depending on the jet’s strength, it can cause total reflection or strong distortion of the wavepacket. In contrast, a wavepacket entering a vertically sheared jet shows energy scattering into higher modes. These higher modes have lower phase and group speeds, shorter wavelengths, and are more susceptible to dissipation.
As the wavepacket exits the jet, reverse energy transfer occurs. The phase speed difference between the modes may explain part of the phase incoherence observed in altimetry data. This research provides valuable insights into the behavior of internal tides and their interaction with equatorial currents, which can help improve our understanding of ocean dynamics and energy distribution.
For the energy sector, understanding these processes is crucial for predicting and managing the impacts of tidal energy extraction. Internal tides play a significant role in ocean mixing, which influences the efficiency of tidal energy systems. By improving our knowledge of these interactions, we can better design and optimize tidal energy technologies, contributing to a more sustainable energy future.
This article is based on research available at arXiv.