Flux measurements from an Ice-tethered profiler: First look

Abstract

A current sensor has been added to the Ice-Tethered Profiler to measure mean currents as a function of depth as well as temperature and conductivity. In addition, for periods with the profiler parked at the top of the mooring, turbulent fluxes of momentum, heat flux, and salinity flux have been measured in the under-ice boundary layer in the Arctic Ocean. In order to rotate the measured profiler relative velocities into earth coordinates, a three-axis accelerometer, a three-axis angle-rate gyro, and a three-axis magnetometer were added. This paper will give a first look at the under-ice turbulent flux measurements. Ice-tethered profiler number 35 was built, deployed in the Arctic on October 8, 2009, and recovered in early fall of 2010. Of 1357 profiles recorded over six months, 335 were stationary profiles for measuring under-ice turbulent fluxes. Of these 335 stationary profiles, six had excessive dropout and were not processed. The other 329 stationary profiles were processed for turbulent fluxes. The turbulent Reynolds stress magnitude was compared to a drag law stress and the correlation coefficient was 66%. Comparing magnitudes gave a drag coefficient of 0.01, high but not unreasonable for the rough underside of the ice and during a period of ice formation with its associated brine production and negative buoyancy flux in the boundary layer. The turbulent heat flux was compared to the time-rate-of-change of temperature at 5.7m depth and gave a correlation coefficient of 33%. The turbulent salinity flux was compared to the time-rate-of-change of salinity at 5.7m and gave a correlation coefficient of 54%.