11 Oct What is the Great Pacific Ocean Garbage Patch?
Not all trash ends up at the dump. A river, sewer or beach can’t catch everything the rain washes away, either. In fact, Earth’s largest landfill isn’t on land at all.
The Great Pacific Garbage Patch stretches across a swath of the North Pacific Ocean, forming a nebulous, floating junk yard on the high seas. It’s the poster child for a worldwide problem: plastic that begins in human hands yet ends up in the ocean, often inside animals’ stomachs or around their necks. This marine debris has sloshed into the public spotlight lately, thanks to growing media coverage as well as expeditions by scientists and explorers hoping to see plastic pollution in action.
What’s it made of?
The Great Pacific Garbage Patch has sometimes been described as a “trash island,” but that’s a misconception, according to Holly Bamford, former director of the U.S. National Oceanic and Atmospheric Administration (NOAA) Marine Debris Program. If only things were that simple.
“We could just go out there and scoop up an island,” Bamford told MNN in 2009. “If it was one big mass, it would make our jobs a whole lot easier.”
Instead, it’s like a galaxy of garbage, populated by millions of smaller trash islands that may be hidden underwater or spread out over many miles.
A 2018 study, using data from vessel and aircraft surveys, found that 79,000 tons of plastic are floating in an area spanning 1.6 million square kilometers (about 618,000 square miles). Previously, researchers believed the area was four to 16 times smaller.
Recent ocean voyages have confirmed the garbage patch covers a huge area, and despite a lack of cohesion, it is relatively dense in places. Researchers have collected up to 750,000 pieces of microplastic from a single square kilometer, for example, and after conducting the first extensive aerial survey — a series of low-speed, low-altitude flights using multiple imaging techniques — the Ocean Cleanup foundation reported “more debris was recorded than what is expected to be found in the heart of the accumulation zone.” (The Ocean Cleanup is the brainchild of Boyan Slat, a Dutch inventor who came up with the idea as a teenager. After years of development and testing, his first system is expected to be deployed in mid-2018.)
While there’s still much we don’t understand about the garbage patch, we do know that most of it’s made of plastic. And that’s where the problems begin.
Unlike most other trash, plastic isn’t usually biodegradable — that is, most of the microbes that break down other substances don’t recognize plastic as food, leaving it to float there forever. Sunlight does eventually “photodegrade” the bonds in plastic polymers, reducing it to smaller and smaller pieces, but that just makes matters worse. The plastic still never goes away; it just becomes microscopic and may be eaten by tiny marine organisms, entering the food chain.
About 80 percent of debris in the Great Pacific Garbage Patch comes from land, much of which is plastic bags, bottles and various other consumer products. Free-floating fishing nets make up another 10 percent of all marine litter, or about 705,000 tons, according to U.N. estimates. The rest comes largely from recreational boaters, offshore oil rigs and large cargo ships, which drop about 10,000 steel shipping containers into the sea each year, full of things like hockey gloves, computer monitors, resin pellets and LEGOs. But despite such diversity — and plenty of metal, glass and rubber in the garbage patch — the majority of material is still plastic, since most everything else sinks or biodegrades before it gets there.
How is it formed?
Earth has five or six major oceanic gyres — huge spirals of seawater formed by colliding currents — but one of the largest is the North Pacific Subtropical Gyre, filling most of the space between Japan and California. The upper part of this gyre, a few hundred miles north of Hawaii, is where warm water from the South Pacific crashes into cooler water from the north. Known as the North Pacific Subtropical Convergence Zone, this is also where the trash collects.
Bamford refers to the convergence zone as a “trash superhighway” because it ferries plastic rubbish along an east-west corridor that links two spinning eddies known as the Eastern Garbage Patch and the Western Garbage Patch.
Read more: https://www.mnn.com/earth-matters/translating-uncle-sam/stories/what-is-the-great-pacific-ocean-garbage-patch