A Drifting buoy tracked by satellite in the Tasman Sea

Abstract

A fibreglass buoy was tracked by the satellite EOLE for 11 months while it drifted around the Tasman Sea. It survived very close passes by two tropical cyclones and was recovered by chance after it had stopped working. At this time the 30-m tether line holding the 5 by 4 m window blind drogue was found to be chafed through. The track of the buoy was compared to sea surface temperature records of merchant ships and it was found that temperatures increased to the left-hand side of the buoy track, which would be the case in the Southern Hemisphere if these temperatures correlated with increased dynamic heights. Winds at the buoy which were calculated from daily atmospheric pressure maps generally had no obvious effects on the tracks, possibly because they caused only a slight deflection of the surface waters. However, there were three occasions when the wind vectors rotated over the course of several days and the effect was to produce small loops in the buoy's track. Also, during a close pass by a tropical cyclone the buoy speed was closely related to wind speed with the buoy being accelerated 90º to the left of the wind direction. Ocean kinetic energies were calculated from the tracks of this buoy, its predecessor and the Agulhas Current buoy of Stavropoulos and Duncan (1974).