Dynamics of a CO 2 -seawater interface in the deep ocean

A trough filled with liquid CO2 located at 3940 m depth has been used as a model system for CO2 deposition on the seafloor. To study the intrinsic properties of the interface between CO2 and seawater a wave maker was used to excite regular plane waves. The frequency (2.5 rad/s) and wavelength (20 cm‐40 cm) of the waves have been measured, and compare reasonably well with the dispersion relation for deep fluid gravity waves. The shear stability of the interface was investigated by setting the water above the CO2 in motion with a thruster. For shear velocities exceeding vc 17.6cm/s the interface became unstable, with breaking waves and CO2 droplets torn from the wave crests. For the sheared system we find that the energy spectrum of the interface variations has a peak for wavelength 0.8 cm, meaning that energy absorption is greatest for this wavelength. For the most unstable wavelength of the Kelvin-Helmholtz instability to match this wavelength, an effective interfacial tension of the hydrate covered interface of 0.075 N/m must be assumed.