Jeff Larson has seen just about everything wash up on the shores of Santa Cruz: bottles, toys, shotgun shells, busted surfboards and fishing floats that looked like they had bobbed across the Pacific.

When surging water driven by the magnitude 9.0 earthquake in Japan tore apart his city’s harbor, he was there to scoop up the splintered docks and broken boats that were heaved onto the sand.

Now, more than a year after the catastrophe in Japan, Larson and fellow beachcombers up and down the West Coast are awaiting the flotsam that was set on a eastward course by the destructive surge of water.

GRAPHIC: Japan tsunami debris adrift

Fishing floats, soccer balls, fuel tanks and crewless fishing vessels set adrift by the tsunami and pushed thousands of miles across the ocean by currents and winds are already arriving on American shores.

But this is not just driftwood. These fragments of people’s lives are floating reminders of a great tragedy: The March 11, 2011, earthquake that unleashed tsunami waves over 100 feet high killed more than 16,000 people, obliterated coastal communities and swept millions of tons of material out to sea.

So as scientists track the debris, the government prepares for its arrival and expeditions sail to the middle of the ocean to meet it, Larson will patrol his adopted beach with a five-gallon bucket and a grab stick, the tsunami on his mind.

“I’ll be looking for any signs of foreign material,” the volunteer with beach cleanup group Save Our Shores said, “and reporting it to anyone who cares.”

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From Alaska to Northern California, beachcombers are reporting a growing influx of aerosol cans, fishing floats and plastic fuel cans swept from Japan.

There was a soccer ball with Japanese writing discovered in March on a remote Alaskan island and traced to a 16-year-old boy in Japan. In early April, the U.S. Coast Guard had to use explosives to sink a so-called ghost ship — a 164-foot Japanese fishing vessel drifting through the Gulf of Alaska.

A corroded Harley-Davidson motorcycle packed in a container washed up on a Canadian island. The owner, located through the bike’s license plate number, had lost three family members in the tsunami, Japanese media reported. Although currents along the California coast may deflect much of the debris back toward Hawaii, environmental groups as far south as San Diego are monitoring their shores just in case.

In all, more than 200 bottles, cans, buoys and floats have been reported to the National Oceanic and Atmospheric Administration. None of the debris is considered radioactive since it was dragged to sea before the nuclear disaster.

But the agency has verified just a few traceable items as tsunami debris. Much of the rest, officials say, is items so commonplace they can’t be distinguished from the flotsam that makes landfall every day.

“We have debris washing up on the shore all the time from Japan, China and other places and they probably have ours,” says Nir Barnea, West Coast coordinator of NOAA’s marine debris program.

Others say the U.S. government is downplaying the size and significance of the approaching debris.

“Unfortunately 99.999% of debris doesn’t come with a label,” retired Seattle oceanographer Curtis Ebbesmeyer said. “Lawyers want something with a street number or a boat name on it. Flotsam isn’t like that, so basically you can’t positively track anything back to Japan.”

Ebbesmeyer, who compiles reports from West Coast beachcombers on his blog, has tallied at least 500 foam and plastic floats and fuel cans that have shown up from Japan since October. He said that’s roughly 167 times the normal rate.

“They all started arriving at once from Kodiak, Alaska, to Northern California, and that’s very indicative of a disaster,” he said.

Ebbesmeyer expects the amount of debris to increase dramatically this fall with the arrival of floating refrigerators, car wheels, bath toys and shoes — items with a remarkable ability to float long distances.

With that possibility in mind, the state of Washington has distributed fliers with instructions on how to handle everything from canisters of insecticide to personal possessions.

“It is extremely unlikely any human remains from the tsunami will reach the United States,” the flier reads. But if they do, it advises, call 911.

With debris making landfall sooner than predicted, U.S. lawmakers have started to question whether the government is truly prepared.

“Many people said we wouldn’t see any of this impact until 2013 or 2014, and now ships and motorcycles and this various debris is showing up and people want answers,” Sen. Maria Cantwell (D-Wash.) said at a hearing this month.

A top NOAA official had few answers to senators’ pointed questions about how much flotsam will wash up and where, how hazardous it will be and how it will be cleaned up. But there is no reason to be overly alarmed, the administrator said, because there is no evidence of any huge sheets of debris headed ashore.

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The tsunami dragged about 5 million tons of material into the Pacific and in the weeks after, satellite imagery showed a massive debris field floating out to sea.

Most of the homes, vehicles and appliances quickly broke up and sank close to shore, but about 2 million tons has dispersed across the Pacific, much of it now floating somewhere northeast of Hawaii.

As the capsized boats, shipping containers and fuel drums move closer to North America, the U.S. government has asked freighters, fishermen and the U.S. Coast Guard to report anything out of the ordinary. But the Pacific Ocean is so vast and the debris so widely scattered that experts say it might not be possible to see more than one piece at a time.

Yet some items have been unmistakable, like the Japanese fishing boat marked Fukushima that a Russian vessel spotted drifting hundreds of miles from Midway Atoll.

Experts say only a small fraction of the debris — perhaps 5% — will make it to the West Coast, where it may wash up intermittently over the course of a year before being pulled back toward Hawaii.

Much of the material — timber and furniture, for instance — may break down before reaching U.S. shores, but fishing nets, buoys, floats and plastics may be float for months without being corroded by the salt water and waves.

The rest is eventually to join the great concentration of debris already circling endlessly in a vast, slow-moving ocean vortex known as the North Pacific Gyre.

For some scientists, the tsunami offers an unprecedented opportunity to study the fate of a huge volume of debris as it spreads from a single geographic point and single moment in time through the world’s largest ocean.

“A tragic experiment of nature,” University of Hawaii researcher Nikolai Maximenko calls it.

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Some aren’t waiting for the debris to arrive; they are sailing out to meet it.

In June, a 13-member research expedition will sail through the doldrums of the North Pacific — lonely, still expanses sparsely traveled by ships — in search of debris from the tsunami.

To cover the costs, passengers are paying $15,500 each to accompany marine debris experts on the 72-foot sailboat — the Sea Dragon — on the voyage from Tokyo to Maui.

Finding the debris could be a bit like searching for drops of ink in a swimming pool — one that covers nearly one-third of the Earth’s surface. So the researchers will drag trawls and pool skimmers behind the racing vessel, reporting observations and taking photographs and measurements of anything they find.

“There could be masses of nets and propane tanks. There could be boats overturned. There could be car tires bobbing around. We just don’t know,” said expedition leader Marcus Eriksen, executive director of the 5 Gyres Institute

Anything that can be traced back to an individual will be photographed, labeled, and if possible, turned over to Japanese authorities.

“We are going to handle it with the utmost care,” Eriksen said. “A horrible disaster like this demands sensitivity and a level of compassion for people as well as the ocean.”

tony.barboza@latimes.com