Medium resolution turbulence cluster for upper ocean measurements under sea ice

A system for measuring three components of velocity, temperature, and conductivity at several levels in the upper ocean under sea ice is described. Instrument clusters including commercially available conductivity and temperature sensors, and three partially ducted rotors mounted along orthogonal axes, are mounted either on masts suspended below the ice, or on a rigid frame that can be lowered by winch. A special interface unit samples data from up to 7 clusters at rates up to 6 per second. Examples from the 1984 MIZEX experiment in the Greenland Sea illustrate measurement of turbulence spectra, Reynolds stress, and turbulent heat flux. Comparison with current measurements from a prototype Diode-Laser-Doppler Velocimeter from Flow Industries is also presented.