Tracking Tsunami Flotsam

Wind and currents determine where debris from the Japanese catastrophe has floated.

Cars mounded up by cleanup crews are leftovers from the March 2011 tsunami that devastated Japan’s east coast in and near Fukushima Prefecture.

Marcus Eriksen

On June 10, 2012, fifteen months after the tsunami of March 11 that ravaged the east coast of northern Japan, we drop our dock lines and depart Yokohama Bay. Our expedition is leaving ten days later than planned, thanks to Mawar, the first typhoon of the season. With the tropical depression that will become Typhoon Guchol forming off the Philippines, we have chosen to squeeze between the two storms and race 1,000 miles offshore to clear the Kuroshio Current. Like the Gulf Stream of the North Atlantic, the Kuroshio is a warmwater highway that big storms track northward along Japan’s eastern shore. We are a team of a dozen sailors, scientists, photographers, journalists, and environmentalists representing eight different countries. Standing on the bow of Sea Dragon, the seventy-two-foot racing sailboat we chartered to Hawaii, we are smiling for now. Our experienced skipper, Rodrigo Olson from Ensenada, Mexico, has previously sailed the equivalent distance of ten circumnavigations around the equator. I trust him when he says, “Let’s go. It could get rough, so we need to sail east, fast.”

The tsunami washed entire communities, an estimated 5 million tons of material, into the ocean at one time, on one day. Some 16,000 thousand lives were confirmed lost, with at least 3,000 more still unaccounted for. During our weather delay in Japan, we traveled to Fukushima to volunteer with a relief agency helping some citizens briefly enter their homes in the no-go zone around the damaged nuclear reactors. Low levels of radioactivity allowed people to return, but we still brought our own Geiger counter. More than 150 miles of the coastline is stripped bare. Concrete slabs lie where homes once stood, much of the debris gathered into giant piles to be separated manually into recoverable materials. But much more was washed into the Pacific, and what didn’t sink immediately was taken by the Kuroshio Current into the North Pacific Subtropical Gyre, an ocean-wide vortex of clockwise currents that sequester floating trash.

Departing Japan on June 10, 2012, the expedition sailed along a route (black line) that took it through the area where, fifteen months after the catastrophe, computer models predicted flotsam from the Japanese tsunami would be concentrated (violet area).

Nikolai Maxime nko/International Pacific Research Center, University of Hawaii at Manoa

As horrible as that disaster was, it has also provided scientists with an opportunity to learn something new, a unique and unrepeatable experiment in oceanography. Of all the construction material, metals, roofing tiles, insulation, cars, tires, trees, glass bulbs, appliances, furniture, textiles, and diverse plastic materials, what, we want to know, is still at sea today, and where is it going? Natural organics, such as trees and wooden construction materials, are likely gone, bored by worms or waterlogged and sunk. Metals, glass, and fiberglass, unless still trapping air, have also sunk, leaving mostly polyethylene and polypropylene plastics adrift. With tremendous caution and compassion, we are going to find out.

Two California-based organizations, the 5 Gyres Institute in Santa Monica and the Algalita Marine Research Institute in Long Beach, organized the expedition route based on oceanographic models predicting landfall of tsunami debris. To date hundreds of tsunami artifacts have reached the shore from northern California to Kodiak, Alaska, including oyster-farm floats, soccer balls, a fishing dock, one Harley-Davidson in the back of an insulated container, and a 120-foot rusted fishing boat (which was scuttled soon after its discovery near British Columbia). Based on the videos of debris being swept off Japan the year before, the public imagines a haunting mirror image, with waves of debris crashing onshore. But when and where debris arrives depends on a variety of factors, especially variations in the direction and velocity of wind and current.

That’s not all. “What we’re finding is that debris reacts differently to wind and current depending on how it is positioned in the water,” explained Nikolai Maximenko of the International Pacific Research Center at the University of Hawaii, an oceanographer tracking tsunami debris. In other words, the movement of a floating object depends on how much of it is exposed to the wind, known as its windage, and how much is beneath the surface. “What you may find on your expedition is the lowwindage, subsurface debris field,” he said. We want to ground-truth this model, as well as to understand the life cycle of diverse materials thrust into the ocean: what marine life colonizes this debris, and what the long-term ecological impacts are.

We have one more assignment. Weeks before our departure date we received a call from the Woods Hole Oceanographic Institute in Massachusetts. “Looks like you’re following the same route we sailed last year to study radioactive fallout from the Fukushima reactor,” senior scientist Ken Buesseler informed us. “Could you revisit the same sites?” Ten flat-packing twenty-liter bottles soon arrived. The work is simple: fill them with seawater from stations every 5 degrees of longitude. Buesseler will analyze these months later in his lab using sensitive detection equipment to screen for low-level radiation. In 2011 Buesseler and other scientists detected cesium-134 (134Cs), a radioactive isotope of the element, along their Tokyo-to-Hawaii transect, with a spike at 170 degrees East longitude, but still far below levels threatening to humans. They want to know if it’s moved—and if it’s detectable at all. This isotope has a half-life of two years, so in ten years, or five half-lives, 97 percent of it decays. Any 134Cs in the Pacific Ocean today is from Fukushima, since any source of it from nuclear testing half a century ago is long gone.

We’re sailing 3,800 nautical miles to get to the debris field, which at the time of our voyage is centered at 35 degrees North and the international date line. It’s as far from land as you can get on the planet without leaving the surface. We do no research for the first five days, focused on getting miles under our belt. With 100-knot sustained winds circulating in a storm that moves four times as fast as we do, there is no room for error. The sea always has the last word.

The first few days of the expedition are wrought with nausea, caffeine-deprivation headaches (because you can’t stomach even the smell of coffee), and bruises from navigating narrow passageways inside what sometimes feels like a washing machine. With a break in the weather, we deploy our high-speed trawl, a net we designed to skim the sea surface at speeds up to eight knots. With an opening five and a half inches wide by eighteen inches tall and a 500-micron-mesh net, it captures zooplankton, fish, and plastic.

A scrap of plastic bearing Japanese characters is encrusted with fish eggs and small barnacles.

Marcus Eriksen
Today’s catch unveils a few unusual suspects. Among the flying fish, squid, salps, and jellies, we find a paper nautilus, Argonauta argo (a species of octopus); a pelagic nudibranch, or sea slug, Glaucus atlanticus (also known as the sea swallow); Pacific viperfish (Chauliodus macouni); and several lanternfishes. These last fish (family Myctophidae), we’ve discovered in previous research, ingest microplastic particles, a multi-colored panorama of which, undistinguishable as to product or country of origin, makes up the bulk in terms of weight of what the trawl collects.

Glaucus atlanticus, a pelagic nudibranch, or sea slug, that turned up in the trawl was photographed on deck before being preserved.

Mandy Barker

With a careful eye on the skies, we plot a course eastward between 30 and 32 degrees North for 2,000 miles through the southern half of the tsunami debris field. The two cyclones have withered, but then merged to create a persistent low-pressuresystem above 35 degrees North, requiringus to stay to its south. Crew keep busy trawling the seas for plastic, and first mate Jesse Horton becomes adept atscooping up debris from the bow, netting a toothbrush and a comb within one hour, and occasionally a fragment with identifiable Japanese characters. We’ve begun timed observations. With a clipboard and a stopwatch, two people stare at the sea surface out to sixty feet off the beam on both sides, recording everything they see. In forty-one nonconsecutive hours spread over three weeks, we catalog 690 pieces, averaging one piece every 3.6 minutes. We also record 130 random observations of trash, all identified as to object and material when possible.

Only 2 percent of the items are non-plastic, including glass, metal, and natural organics. Roughly 60 percent are unidentified fragments of hard plastic or foamed polystyrene. The rest are unmistakable items: buckets, crates, flip-flops, a coffee cup, fishing floats and rope, plastic bags and bottles, bottle caps, a toy red pail in the shape of a castle, a syringe, a clothes hanger, a surfboard fin, a felt-tip marker, a boot eerily laced to the top, and a few glass jars, bottles, bulbs, and fluorescent tubes. It’s extremely difficult to know when or from where debris has originated, but three objects stand out as from the tsunami.

A wheel for a small truck, its tire still inflated, is marked “Made in Japan.” Algae, gooseneck barnacles, and other marine organisms have colonized it.

Marcus Eriksen

“A big tire just went by!” photographer Mandy Barker yells. We go back for it. It is not easy to turn the boat around when full sails are up. “Roll the jib and center the main,” skipper Olson yells. Barker keeps her eyes on the tire, now more than a tenth of a mile behind us. “Ten degrees to port, fifty meters off the bow,” crew yell to guide the boat to the tire. Using a scoop net, it’s a struggle to haul the algaecovered tire aboard, still inflated on the rim. Thirty small crabs drop to the deck. A bristle worm is wedged between the rim and the tire, and a dozen gooseneck barnacles sticking outward along the treads flail their cirri, or legs, grasping at the air. It’s a tire from a small truck, unlike a tire seen on U.S. vehicles, with “Made in Japan” embossed on one side. The rim is well preserved where it is painted, but any exposed iron is nearly rusted through. If left for another year in the sea, the tire would likely fill with water and sink. Soon after, Paul Sharp, founder of Australia’s Two Hands Project, nets a piece of thatch the size of a large pizza box. Two layers of straw thatch, factory stitched with a thin sheet of blue foamed polystyrene insulation in the middle, is unmistakably a piece of traditional tatami mat from the floor of a Japanese home. Straw, like any other natural organic or wooden construction material, does not last long at sea. Wood-boring worms, known to plague ships for centuries, or seawater seeping into the air-trapping spaces between plant tissues, will decrease the buoyancy of plant material and eventually sink it. The timing of decay, location in the debris field, and lack of slowgrowing colonial bryozoans give me confidence that the tire and matting are from the tsunami.

“I think it’s a whale!” one crewmember says, followed seconds later with, “No, it’s a capsized boat.” In the late afternoon, 1,587 nautical miles east of Tokyo, we discover the forward half of a crushed fishing boat drifting in the water. Any excitement at finding it is muted by the real possibility that this boat belonged to someone who suffered—and perhaps perished—in the tsunami.

The author inspects fish attracted to the mostly submerged front half of a fishing boat. The fish may be seeking to feed on marine life that colonizes such flotsam.

Stiv Wilson

Tipped horizontally, the boat’s prow reveals Japanese characters, almost certainly identifying it as a casualty of the tsunami. Its owner is still unknown.

Stiv Wilson
I dive in with the skipper to investigate and film fish aggregating below. We count at least eight species, including amberjack, mahi mahi, and a pair of wahoo. They disperse as I approach. I grab the rail of the boat for a closer look, and see that the hull and deck are remarkably barren of colonizing marine life. Expecting a bouquet of gooseneck barnacles, crabs, nudibranchs, and polychaete worms, I find only eight adult barnacles on the entire exposed surface, which sits two-thirds below the sea surface. In one small, protected crack I see the diversity I am looking for, hidden from grazing triggerfish. We haul the boat aboard and immediately send photographs to NHK Broadcasting in Japan. The three characters in the boat’s name are literally translated as “bright,” “door,” and “vessel.” By the end of our trip, the photographs are broadcast on Japanese television in search of the owner (still unidentified to date).

On day sixteen of our expedition, rounding the northwest end of the Papaha¯naumokua¯kea Marine National Monument, we exit the tsunami debris field. The national monument is a 139,797-squaremile conservation area that encompasses most of the string of minor Hawaiian Islands. After sailing the remaining 1,200 nautical miles to Honolulu, Hawaii, I meet Nikolai Maximenko in a coffee shop. His latest animations track tsunami debris with variations in windage. I show him the debris we found, all of which fits the low-windage profile. We realize that much of the debris hasn’t made it across the ocean yet.But that doesn’t mean we’ll see an avalanche of trash anytime soon. Comparing the high-windage debris model with that of low windage, we see they do not go in the same direction. “By early summer 2012 we’ve witnessed most of the high-windage debris make its way across, pushed by wind to the shores of Alaska, British Columbia, Washington, and Oregon,” Maximenko explains.

Low-windage debris, influenced largely by current, behaves differently, moving southward into the California Current and the Great Pacific Garbage Patch. What we’ll likely see in the years ahead is a trickle of debris reaching North American coastlines, and then an increase in degraded-plastic pollution on the eastern shores of Hawaii, like famed Kamilo and Kahuku beaches, where weekly beach cleanups can barely keep up with the never-ending plastic waves. Over time the tsunami debris will become indistinguishable from the background of trash in the North Pacific Subtropical Gyre, noticeable only an increase in microplastics in future researchers’ trawls. The impacts on wildlife owing to ingestion and entanglement are the same, whatever the source.

The immediate response to the 2011 tsunami has been to care for the victims and pick up the pieces. But that natural disaster will continue to leave its mark on distant shores—and it’s mostly plastic.

Based on the behavior of drifting buoys deployed over years, a model predicts how the tsunami flotsam will be carried by ocean currents alone over a five-year period. Much of the debris should end up circulating in what is known as the Great Pacific Garbage Patch. Not shown is the path of wind-driven flotsam, comprising objects that project well above the water’s surface. It travels more quickly, pushed by the prevailing winds to the shores of Alaska, British Columbia, Washington, and Oregon.

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