Around Antarctica in Five Years

by Thomas Ronge

I’m currently working on a project in which I’m trying to reconstruct changes in the circulation patterns of the Southern Ocean and their impact on past climate parameters. However, while looking at my data, pondering how water masses are transported from one spot in the ocean to another, I suddenly had to think about a big yellow buoy which crossed my path last year…

Is it an AUV? Is it an Argo Float? No! It’s a renegade buoy, casually braving the Southern Ocean. 
©Thomas Ronge/AWI

In February of 2017, heading for the Antarctic Amundsen Sea, we had been sailing the Southern Ocean for about a week. One day before we reached the sea ice margin, we spotted a big yellow buoy, dancing in the icy waves.

From the distance, the crew of R/V Polarstern could easily identify the buoy as the detached, uppermost part of a scientific mooring. During our expeditions, we always try to collect floating garbage and dispose of it properly, back on land. Therefore, the captain and our chief scientist made the decision to recover the buoy, in particular as this kind of “garbage” might carry some important scientific data.

Detective Marcelo, searching for 
signs of the buoy’s owner.
©Thomas Ronge/AWI
Once on the working deck, we could see that the buoy was indeed the uppermost part of a mooring, which originally went down to a depth of 1500 m. Heavily battered by the sea and ice, only the buoyancy body itself and an Acoustic Doppler Current Profiler (ADCP) survived.

An ADCP is the tool of choice for most oceanographers interested in the velocities within the water column. It uses the Doppler shift of sound waves to detect the direction and speed of oceanic currents. Unfortunately, there was no sign of the buoy’s owner. The only clue we had was the manufacturers seal, which included a serial number.
This number we could use to contact the manufacturer and ask whether or not they can identify the unfortunate owner of the mysterious buoy.

Fast forward three weeks, we got a call from the US-based company. Back in 2012, Chinese colleagues of the First Institute for Oceanography had deployed the buoy in the East Antarctic Prydz Bay!
The Chinese scientists planned to recover the mooring one year later, in 2013. However, once back, there was no trace left of their equipment. The mooring, and more importantly the data, were thought to be lost at sea.

The surviving Acoustic Doppler Current Profiler. 
Did we recover a treasure trove filled to the
brim with scientific data, or just a rubber duck
 on steroids?  ©Thomas Ronge/AWI

Back in 2018, our find yields new hope for our Chinese colleagues that some data might have survived within the buoy. Now that Polarstern is back at her homeport of Bremerhaven, Germany, we have prepared the buoy for its last journey back to China. So far, it is still sitting in an AWI warehouse somewhere in the port of Bremerhaven. After waiting for customs clearance and the return of our Chinese colleagues from the white continent, the final shipment of our buoy is planned for May or June of 2018. So, I’m a bit sorry for the cliffhanger here, but hey that’s how all the pilots of a good series end, no? Anyway, I promise to update you on the fate of the buoy’s scientific value…

However, one other mystery remains, eventually. How on Earth did the buoy manage to travel to the opposite part of Antarctica? The first conceivable route (A) runs clockwise along the Ross Sea and into the Amundsen Sea. This route would indicate a direct transport within the Antarctic Circumpolar Current (ACC). On a second route (B), the buoy would have travelled counterclockwise along the Weddell Sea, the Antarctic Peninsula, and via the Bellingshausen Sea within the Antarctic Coastal Current. A third possible route (C) would have transported the buoy within the Coastal Current into the Atlantic Weddell Sea, and from there via the Weddell Gyre and the Scotia Sea into the ACC. From Weddell Sea, the buoy would have circumnavigated about ¾ of the Antarctic continent!

Which route did the Mystery Buoy travel in the Southern Ocean? Clockwise, via the ACC (A – red), counterclockwise, passing the Antarctic Peninsula (B – blue) or the badass-combination of both, ultimately circumnavigating up to ¾ of Antarctica (C – black)? Map generated using the awesome, free Quantarctica GIS 
package (

Probably we will never solve this mystery. In my humble opinion, route B is the most difficult and unlikely one and I’m not really convinced the buoy would make it to the other side of the Antarctic Peninsula. A and C, on the other hand, are both likely. However, I prefer route C, as it would be just too awesome if the buoy had sailed almost the entire Southern Ocean!

No matter which route “our" mystery buoy has chosen, this find is an impressive example of how closely linked our global oceans are.

Thomas Ronge, PhD
Department for Marine Geology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Germany

If you have questions or comments concerning Thomas' post, please leave a comment below or send him an email. You can also connect with him on Twitter and ResearchGate.


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