(Phys.org) —This month's annual beach cleanup may turn up items from the Tohoku earthquake and tsunami that devastated Japan more than two years ago.
Remnants of the wreckage continue to reach the Pacific Northwest: A 65-foot Japanese dock washed up in December on a beach near Forks, Wash., a fish hitched a ride on a 20-foot boat that washed up in March in Long Beach, Wash., and pieces of a Japanese shrine washed ashore in March and April in Oregon. Japanese sports balls, foam insulation and other flotsam regularly wash up on the coast to provide a reminder of the lasting effects of the disastrous earthquake and tsunami.
Ian Miller, a coastal hazards specialist with Washington Sea Grant, a UW-based center that's part of the national Sea Grant network, co-authored a report on possible scenarios for debris accumulation in Washington state and has recently given public talks about the debris found to date.
"So far there still hasn't been a big wash-up significantly above and beyond our normal debris load," he said. He and hundreds of volunteers will comb the beach April 20 to see if that remains true after the largest annual beach cleanup of Washington's coast.
Immediately after the March 11, 2011, tsunami, one of the concerns was that huge amounts of garbage would wash up on the U.S. coastline.
"What became obvious early on was that nobody had a clue," Miller said. "There was a lot of uncertainty, a lot of contradictory information, and that caused anxiety.
"That tells me we need to focus on what is happening now, so that next time we have a more factual basis to make projections."
To officially be designated as tsunami debris, an item must have an identifying marker and get verification of its origin from the Japanese government. However, pieces of plastic foam believed to have probably come from Japan are common, as are pieces of lumber that observers say are unlike their American counterparts.
A widely reported pulse of suspected tsunami material washed ashore in early summer, Miller said, and then things quieted down. Winter storms in recent months have been bringing more items.
Miller's review of oceanographic literature, published in the fall, predicted that most of the debris would wash up in Alaska, and that most would land within four years of the tsunami. Anecdotal reports and media coverage suggest that most material so far is in fact hitting Alaska, Miller said.
Computer models from the University of Hawaii suggest that most of the tsunami material has washed ashore by now. Models from the National Oceanographic and Atmospheric Administration show a large patch still offshore. But those are probably items that don't catch the wind, such as plastic bags or pieces of wood, that likely will follow currents to what's known as the garbage patch in the center of the North Pacific Gyre, Miller said.
He is studying the actual debris accumulation and working with colleagues at the National Park Service, NOAA and other agencies to monitor the beaches and dispose of the dock and other large items.
It's not until the big annual cleanup that many of the more remote sections of beach are combed for litter. To document possible tsunami debris, a team from Western Washington University will be sorting and weighing collected material.
That cataloging effort is a step in the right direction, Miller said.
"We know that we get debris on our coast, but we don't know what is a quote-unquote 'normal' load," Miller said.
He hopes documentation will broaden awareness and knowledge of washed-up ocean garbage.
"The tsunami has highlighted the issue. On a global scale, it's a drop in the bucket compared to the amount of trash that's out in the ocean and the amount that's added to the ocean every year," Miller said. "If this gives us more information about where it washes ashore we can focus [cleanup] investment accordingly."
If you plan to spend the lead-up to Earth Day cleaning up the Washington coast, register online and arrive early Saturday. No special tools are required, but volunteers may want to bring a sharp knife, hacksaw or small shovel to deal with tenacious debris items. Cleanup takes place at beaches along the coast, and some organizing groups host volunteer barbecues or chowder lunches afterward.
The annual event is a chance to help clean the coast and experience a connection with other nations around the Pacific Rim.
"Last year I can remember sitting down with a bag of plastic bottles, and I think I ended up counting eight different languages," Miller said. "You find things from all over the world."
Explore further: 3Qs: Game theory and global climate talks
More information: Learn about tsunami debris.