[Translate to English:] Foto | Ritzo ten Cate

Prof Talk | Toys afloat at sea

IKEA furniture, sandals, My Little Pony’s. The beaches of the Wad were recently strewn with garbage and new batches are still washing ashore. A German freighter lost nearly three hundred full containers containing a range of goods during a heavy storm in early January. Can thousands of floating toy ponies teach us something about the sea's currents? Can we predict when and where these loads will end up? And what will happen to all the lightweight packaging?

photo Ritzo ten Cate

With the images of the devastation wrought on the beach etched one's retina, it is difficult to imagine that an accident like this can have any positive aspects. But as early as last week oceanographers reported that a lost load bobbing around certainly can reveal useful information about sea currents, the most famous example being the thirty thousand rubber ducks that went overboard in the Pacific in 1992 and were found here and there some twenty years later.

In the intervening period the American researcher Curtis Ebbesmeyer - expert in floating wreckage, flotsametrics - kept an accurate record of the journey travelled by the rubber ducks and recognized this as a unique opportunity to trace ocean currents.


As yet this process in reverse - using knowledge of currents to predict where a load will wash ashore - is unfortunately not very accurate, explains fluid dynamics expert GertJan van Heijst. “The ocean's major currents are found at depths and complete their circuits slowly, taking a year or more. Think of a current as a big mass that is in motion. Locally on the surface all kinds of factors such as wind, storm and depressions can generate a different current. So there's a lot of white noise to contend with and that makes predictions difficult.”

“In addition to this, all that is detectable in the North Sea is an offshoot of the major ocean current. While it is permanently present, it is very weak. As we are dealing with various time scales and chaos factors, simulations provide only a rough impression when we try to predict locations.”


The Wadden region is an even more complex system, point out Van Heijst and his colleague Matias Duran Matute, who produces simulations of the currents in the Wadden Sea at the Royal Netherlands Institute for Sea Research (NIOZ). “It is the world's largest continuous tidal area, but not only is the seabed uncovered during ebb, water is continuously flowing in and out through the tidal inlets. As a result, the surface currents change constantly, and while what we can simulate is ever increasing, chaos remains a tricky element to capture in a model.”

The fact that the seabed is also moving increases the impact of an accident like this one. “Washed-up items of furniture are things you can clean up while they are still in one piece, but tiny remnants of plastic packaging get into the sediment that is stirred up when seawater flows in,” says Van Heijst. “When the tide turns, the plastics sink to the bottom or get entangled in biological structures and then spread farther in a fragile ecosystem.”

Along the beaches of the Wadden Islands and the North Netherlands coast, the University of Groningen has now started a large-scale study in which they are working with app-enabled volunteers - see waddenplastic.nl - to chart the location and quantity of washed-up grains of plastic and pieces of foil. Professor in Physical Chemistry of Polymers Jaap den Doelder says, “The HDPE grains (high-density polyethylene, ed.) that were probably in one of the containers provide the basis for making robust plastic packaging of various types, such as shampoo bottles. The packaging foils are made of low-density polyethylene. In chemical terms, they're the same, and both are inherently nontoxic, but they can cause major problems in an ecosystem; you don't want them to end up there. This campaign can hopefully provide a good picture of the spread of plastics and in that way help with the cleanup. ”

Ecological disaster

If the plastic soup still seems a world away, a container accident like this one - Van Heijst, “Go ahead and call it an ecological disaster” - brings home the downside of plastic use. With the reuse of plastics central to his chair, Den Doelder appeals for the recycling infrastructure to be improved. “Every year eight million tons of plastic disappear into the seas. Eight million tons!”

“In many Asian countries the use of plastic has increased enormously and afterwards it is often casually thrown away. It's a continuous process that we see only when, for example, a river clogs up and the trash piles up. In the Netherlands we are already making headway, but now we must lend our help worldwide to solve the plastic problem. If you want to consume, you also have to collect.” Because however useful rubber ducks or toy ponies may be for research into currents, plastic does not belong in the sea.

Reading tips

* Book tip offered by GertJan van Heijst: Flotsametrics and the Floating World  How One Man’s Obsession with Runaway Sneakers and Rubber Ducks Revolutionized Ocean Science - Curtis Ebbesmeyer, Eric Scigliano

* Reading tip offered by Jaap den Doelder: Stemming the tide – Land-based strategies for a plastic-free ocean

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