Waves and vertical mixing in the interior of the ocean

Vertical mixing in the ocean‘s interior plays an important role in the maintenance of the known ocean stratification as it leads to an upward transport of cold water. This process effects major ocean current systems which points out the importance of measurements that help to determine the magnitude of vertical mixing, understand generating processes and investigate its global distribution.A likely energy source for vertical mixing are internal waves which propagate in the ocean‘s interior. These waves are generated by a variety of processes such as e.g. wind, tides, the bottom topography or strong currents. They can be exited in a specific frequency range which is dependent on the latitude and the stratification. Signals of these waves can be seen in measurements of temperature, salinity and velocity. As an internal wave propagates, it transports energy which eventually can be used for vertical mixing, for example if a wave interacts with the topography.During my PhD project I am using shipboard measurements as well as a 5 year long timeseries of moored instruments to investigate temporal changes in these mixing processes and internal wave activity in the strong and variable Deep Western Boundary current at 16°N in the Atlantic.

Janna Köhler, GLOMAR PhD student

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RCMmicrocat

Instruments were deployed in the Deep Western Boundary current to measure velocities (RCM), pressure, temperature and salinity (microcats).