If you've had cause to check the Coffs Harbour and Batemans Bay waverider buoys, you'll notice something is amiss. Both buoys have currently gone AWOL off the East Coast.
The reason for the buoys - which are owned and operated by Manly Hydraulics Laboratory (MHL) - breaking their moorings is unknown, there's been no large swells to break their fastenings, but nor are the buoys completely lost.
Since going adrift on the 12th of November, MHL have been tracking the Coffs buoy via satellite and they've provided a plot of its journey thus far. The plot makes visible the East Australian Current (EAC).
The EAC is a western boundary current (falling on the western side of the Pacific Ocean and abutting the Australian continent) and feeds tropical water south from the Coral Sea down the NSW coast, usually taking a turn east towards New Zealand from a position south of Seal Rocks. At this junction we also see warm water eddies spawning and seperating from the main flow.
When at its strongest the East Australian Current pushes down past the southern NSW coast and can even impact Tasmania. We're seeing this occur more frequently with continued warming of the world's oceans due to climate change.
Overlaying the track of the drifting Coffs Harbour buoy with the observed current path and speed provided by the Integrated Marine Observing System website (below), we can see an almost perfect match, as expected.
The buoy has travelled approximately 700km in 20 days, that being 35km/day, 1.5km/hour or 0.41m/s. Looking at the chart above we can see the strongest sections of the EAC are currently flowing at about 1.5m/s (black arrows).
Currently the buoy is located east-southeast of Jervis Bay and looking at the current path from here, we can expect to see the buoy hooking due east and then back north-east into the Tasman Sea. The MHL have stated they're “monitoring the drifting buoy and will attempt recovery if it moves close to the coast.”
This appears unlikely to happen.
Unike the Coffs buoy, the Batemans Bay buoy isn't communicating with MHL, however as we know how the EAC is moving we also know the approximate path of the buoy. Depending on when it went adrift, the Batemans buoy could currently be anywhere from eastern Bass Strait to up near where the Coffs Harbour buoy is drifting, which would be very handy indeed.