The variable-buoyancy drifting DIMES Shearmeter instrument

A new drifting float has been designed and built for long-endurance continuous measurements of internal gravity waves in the upper 1700 m of the ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The floats measure vertical shear multiple times per hour. They also record temperature and conductivity at the same data rate to record vertical strain and thus Richardson number. They have active buoyancy adjustment so that they can remain on the density surface under analysis in the project. They are tracked acoustically while operating, drop ballast after recording for up to one year, and return data via Iridium satellite.