Garbage soup- secrets spewed up by the trash vortex

by Jeni Bone on 31 Dec 2008
Discovered by a sailor in 1997, the 'Great Pacific Garbage Patch' or 'trash vortex' that floats around in oceanic gyres is now of great interest to scientists, biologists, weather forecasters and marine researchers for the information it reveals about ocean currents.

There is a soup of waste – humanity’s flotsam and debris – literally clogging the Pacific Ocean. Experts say it’s growing at an alarming rate and now covers an area twice the size of the USA. This floating rubbish dump stretches from Hawaii almost to Japan and is held in place by swirling underwater currents.

Charles Moore, an American oceanographer who discovered the phenomenon and coined the phrases 'Great Pacific Garbage Patch' or 'trash vortex', believes that about 100 million tons of flotsam are circulating in the region.

Marcus Eriksen, a research director of the US-based Algalita Marine Research Foundation, which Moore founded, describes it as 'a plastic soup'.

'It moves around and when it comes close to land, as it does at the Hawaiian archipelago, the results are dramatic. The garbage patch barfs, and you get a beach covered with this confetti of plastic.'

About one-fifth of the stuff is thrown off ships or oil platforms. The rest has been discarded from the land.

Moore, a former sailor, first encountered the rubbish in 1997, while taking a short cut home from a Los Angeles to Hawaii yacht race. He had steered his craft into the 'North Pacific gyre', a vortex where the ocean circulates slowly because of little wind and extreme high pressure systems.

Gobsmacked by its magnitude, Moore, the heir to a family fortune from the oil industry, was inspired to sell his business interests and become an environmental activist. These days he warns people that unless consumers cut back on their use of disposable plastics, the plastic stew will double in size over the next decade.

In the past, rubbish that ended up in oceanic gyres has biodegraded. But modern plastics are so durable that objects half-a-century old have been found in the north Pacific dump.

Moore said that because the sea of rubbish is translucent and lies just below the water's surface, it is not detectable in satellite photographs. 'You only see it from the bows of ships,' he said.

Worldwide, about 10,000 cargo containers fall overboard each year. In most parts of the world, the dispersal of flotsam isn't of major interest to researchers. But along the busy trade routes that link eastern Asia to North America, the random rubbish and containers that drop off ships are showing scientists precisely how the Pacific Subarctic Gyre works.

Despite thousands of scientific instruments dotted around our oceans, when it comes to measuring surface currents, scientists have been limited by their equipment. Satellite-monitored probes called Argo floats drift through the ocean at depths of about 2 kilometers. Every 10 days or so, they pop up to measure the overlying water's temperature and salinity.

However, the direction and speed of deep currents, where these high-tech probes spend most of their time, don't necessarily match those of currents in the top few metres or centimeters of ocean. The path of an Argo float provides little information about surface currents.

Then there are probes specifically designed to ride surface currents. These face their own problems. Their sensors can quickly become obstructed by algae, barnacles, and other organisms that thrive in the sunlit section of the ocean.
On top of all that, probes use batteries that fail within months, only allowing them to travel a small fraction of the path around the gyre.

Now, to map the currents and clock their speeds, scientists are harnessing the power of floating junk. For the first time, scientists can estimate that a lap around the Pacific Subarctic Gyre takes approximately three years. From that and other studies of the circulating trash, researchers have noticed long-term variations in water temperature and salinity in the North Pacific that hadn't been observed previously.

Research aside, the consequences of this massive bundle of plastic debris are negative. Plastic is believed to constitute 90 per cent of all rubbish floating in the oceans. The UN Environment Program estimated in 2006 that every square mile of ocean contains 46,000 pieces of floating plastic. The group states that plastic waste causes the deaths of more than a million seabirds every year, as well as more than 100,000 marine mammals.

And not all plastic floats. Around 70 per cent of the junk sinks to the bottom, stifling the sea bed, killing organisms and messing with the food chain. In fact around 70 percent of discarded plastic sinks to the bottom. Dutch scientists have counted around 110 pieces of litter for every square kilometre of the seabed, a staggering 600,000 tonnes in the North Sea alone.

Our plastic waste poses a risk to our health too. What goes into the ocean goes into the food chain and eventually onto your dinner plate. Hundreds of millions of tiny plastic pellets, known as 'nurdles' - the raw materials for the plastic industry - are lost or spilled every year, working their way into the sea. These pollutants act as chemical sponges attracting man-made chemicals such as hydrocarbons and the pesticide DDT.

The North Pacific gyre is one of five major ocean gyres and it is possible that this Trash Vortex problem is one which is present in other oceans as well. The Sargasso Sea is a well known slow circulation area in the Atlantic, and research there has also demonstrated high concentrations of plastic particles present in the water.

Greenpeace warns that floating plastics can also affect marine ecosystems in yet another way: by providing a ready surface for organisms to live on. These plants and animals are then transported far outside their normal habitat to invade new habitats and become potential nuisance species.

More at www.greenpeace.org