A system for correcting ADCP heading on moorings at high latitudes

CSIRO has deployed large oceanographic moorings near the South Pole to help scientists better understand ocean dynamics in the ice forming regions around Antarctica. A standard instrument on these moorings is an Acoustic Doppler Current Profiler (ADCP), which provides information on the direction and magnitude of ocean currents in the water column. These instruments use an integrated magnetic compass to alight current vector readings with compass points. Unfortunately, at high latitudes - such as those near the magnetic South Pole - those internal compasses are not able to produce a reliable heading. A system was needed to supplement the internal ADCP compass in order to properly align the current heading. A system using a fiber optic gyroscope was developed to provide corrected heading information for the instrument packages. This paper discusses the challenges of correcting for compass heading data at high latitudes. It discusses the design and development of a system for facilitating the correction of ADCP heading data on moorings deployed in the southern ocean. Results from ocean deployments in the Ross Sea are also presented. Finally, the paper disuses how the system can be modified to allow for deep operation, operation on larger moorings or integration with other ship deployed systems such as conductivity temperature and depth (CTD) systems.