The rubber ducks that changed our understanding of the world's oceans

  • Living
  • Monday, 21 Feb 2022

Thousands of rubber bath toys were released in the North Pacific in a container accident some 30 years ago. They helped provide valuable data for oceanographers. Photo: dpa/picture alliance/Symbolbild

Some 30 years ago, a container toppled off a ship into the North Pacific. Such an accident in itself isn’t that remarkable as they are quite common.

But this one would help provide valuable insights into the oceans.

The container, with its 29,000 rubber ducks, turtles, beavers and frogs, was originally heading from Hong Kong to the United States. Instead, when a storm struck, the contents were released into the seas in January 1992.

Strong waves and powerful winds then swirled the toys onwards to coastlines around the world in myriad brightly coloured journeys longer than their manufacturers had ever dreamed.

People strolling along the beaches picked them up and gradually, the journeys made by the plastic bath toys caught scientists’ attention.

Reconstructing the time it took for the toys to reach different parts of the world and the routes they took provided multiple unexpected insights into the currents of the oceans.

US oceanographer Curtis Ebbesmeyer took a leading role in the studies, having gathered data after a similar shipping accident some years earlier.

When more than 60,000 Nike trainers fell overboard and then washed up on the west coast of the US and Canada, he recruited a network of beachcombers to report what they found.

They contacted him when they discovered the bath toys too, tracing their origin through the manufacturer’s trademark.

Treasure trove of data

“The accident with the bathing animals brought research a real treasure trove of data,” says Johanna Baehr, an oceanographer at the University of Hamburg.

“In one fell swoop, there were thousands of data points – we wouldn’t normally just put out so many scientific measuring instruments at once.”

The idea of researching the ocean currents by using floating devices is far from new.

“Using drifters is one of the oldest methods of marine research,” says oceanographer Jorg-Olaf Wolff from the University of Oldenburg.

Back in 1864, researcher Georg von Neumayer from what was the German Naval Observatory in Hamburg threw a bottle containing a message overboard as he sailed off Cape Horn.

His letter asked the finder to report back where and when the bottle was found.

It reached Australia. “That was more than 150 years ago and has helped to better understand large-scale ocean currents,” says Wolff.

Nowadays, researchers use devices equipped with GPS to record precise data of temperatures, water salinity or air pressure and radio them to satellites.

“There are also free-floating devices that repeatedly sink from the surface to depths of 1 and 2km, collecting data as they go,” says Wolff.

The data delivered by the flotillas of toy ducks and frogs was far less accurate.

“But it’s better than nothing, especially because the data was generated for free,” he says, noting the high cost of digital measuring devices means it is impossible to use such large numbers.

The ducks, beavers and frogs first circled counterclockwise in the North Pacific current, from Sitka on the coast of Alaska, along the Aleutian Islands, past the Kamchatka Peninsula and finally back across the Pacific, up the west coast of the US to Alaska.

In 1994, 1998, 2001 and 2003, Ebbesmeyer received reports of finds from Sitka, suggesting that some of the toys had made a few rounds in circles.

Others escaped the vortex and made it to Hawaii and Australia.

“Perhaps one of the most exciting findings is that the toys drifted from the Pacific to the North Atlantic,” says Baehr. “This was predicted by corresponding models, but the animals proved that it can really happen.”

Distribution of litter

Beachcombers were still picking up toys in the early 2000s on the east coast of the US as well as in Scotland and England.

Scientists say they drifted northwards through the Bering Strait into the Arctic Ocean, reaching Greenland, although it remains unclear whether they were frozen in ice or sat above the ice floes.

“This route was an interesting confirmation that there is a surface current there that travels such a distance,” says Wolff.

He has been using drifters to investigate how litter is distributed in the North Sea, as part of an interdisciplinary team set up in 2016.

They threw 65,000 small wooden drifters into the North Sea, marked with a number and a request to report any finds with details of place and time.

This project has also provided unexpected insights, namely that the currents in the North Sea can reverse under certain conditions.

“We suddenly received reports from England that showed the wooden drifters were no longer drifting counterclockwise as usual, but clockwise,” says Wolff. Scientists had not known that was possible.

Such studies can enable a better understanding of the distribution of plastic waste so ways can be developed to handle it.

Using drifting instruments can also provide on-site data to develop weather models, and ultimately improve forecasting as well as predictions for the decades to come, given climate change, says Baehr.

For now, it is not clear what has happened to any tub toys that were not picked up. Wolff doubts any are left out there. After 30 years of wind, waves and UV radiation, the ducks and frogs have likely turned into microplastic.

Baehr, however, says a couple of the toys may still be out there, perhaps frozen in ice, and could still turn up. “Rubber ducks have a frighteningly long shelf life, like all the plastic that winds up in the sea,” she says. – dpa/Anja Garms

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