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Ocean Mixing |
| Physical Oceanography |
The general circulation of the ocean is driven by the winds and the large-scale variation in solar heating with latitude. As currents accelerate under these forces, frictional processes develop which serve to impede further acceleration. Ultimately a quasi-steady state is achieved (our climate) where forcing and dissipation are in balance.
For the past twenty-five years it has been possible to measure small scale turbulent processes in the ocean interior. This centimeter to millimeter scale motion is strongly damped by molecular viscosity. It is the ultimate end product of a cascade of energy from large to small scales. The phenomena involved at intermediate stages in this cascade process and the basic principles which govern the transfer of energy from one scale to the next are still not well understood.
In the figure, upper ocean data obtained in the western equatorial Pacific ocean are displayed. A Doppler sonar mounted on a research vessel documented the ocean current (top) and acoustic echo strength (bottom) as a packet of "solitary waves" passed by. These waves are isolated pulses of velocity (up to 1 m/s = 2 kts) which propagate at speeds of roughly 2.5 m/s (5 kts). The upper ocean interior is displaced 80 m downward in approximately 10 minutes as these waves pass. The increased acoustic scattering following soliton passage is evidence of small scale turbulence which is triggered by the large scale waves.
The solitons were generated by tidal motion interacting with a nearby chain of islands. At Scripps, they are being studied theoretically and observed in both coastal and open ocean environments. We are tying to determine whether these motions are a major link in the dissipation of tidal energy, globally, or just an interesting sideshow.
Scripps faculty researching ocean mixing and/or solitons include:
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Physical Oceanography at Scripps