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CORVALLIS, Ore. - A massive trail of debris from the devastating tsunami that struck Japan in March of 2011 is slowly making its way across the Pacific Ocean en route to the West Coast of the United States, where scientists are predicting it will arrive in the next two to three years - right on schedule.

The mass of debris, weighing millions of tons and forming a trail a thousand miles long, will likely strike Oregon and Washington, according to models based on winds and currents.

But new accounts of where the trail has progressed suggest that at least some of that debris may peel off and enter the infamous "Garbage Patch," a huge gyre in the Pacific where plastic and other debris has accumulated over the years, according to Jack Barth, an Oregon State University oceanographer and an expert on Pacific Ocean currents and winds.

"Recent reports of debris are from farther south than the axis of the main ocean currents sweeping across the north Pacific toward Oregon," said Barth, a professor in OSU's College of Oceanic and Atmospheric Sciences. "This means a fair amount of debris may enter the patch. We should still see some of the effects in Oregon and Washington, but between some of the materials sinking, and others joining the garbage patch, it might not be as bad as was originally thought."

Barth said as time goes on, more of the materials will sink as they become waterlogged, or become heavy from barnacles and other organisms growing on them.

Conversely, he said, items of debris that are higher in the water and can be caught by the winds - such as small boats - may arrive more quickly than anticipated. The "westerlies," as these winds are called, blow straight across the Pacific Ocean from Japan to the Pacific Northwest coast "and they can be pretty strong," Barth pointed out.

Recent reports that the debris is ahead of schedule don't match Barth's calculations, which suggest that the bulk of the debris should arrive along the West Coast in 2013 to 2014. It appears to be moving about 10 miles a day, he said.

Fears of contamination from the debris are largely unfounded, Barth said. The OSU scientist just returned from a meeting of PICES - the North Pacific Marine Science Organization, where Japanese scientists reported that radiation levels in the waters off the Japanese coast were below a safe threshold.

"The dilution power of the Pacific Ocean is enormous," Barth said.

Barth led a five-year study a decade ago looking at how water moves off the Oregon coast in the aftermath of the 1999 shipwreck of the New Carissa. Hundreds of gallons of oil leaked from the vessel and despite sophisticated ocean current models, the fuel appeared in places that surprised scientists.

Although the westerlies will bring some of the debris toward the Northwest coast, what happens as it arrives near the shore will depend on the time of year, Barth said.

"One thing we learned from the New Carissa, is that when things get dumped off the Oregon coast in winter, they go quickly northward," Barth pointed out. "If the debris arrives in the winter, some of it may get pushed up to Vancouver Island. If it gets here in the summer, it is more likely to drift down to the south."

Local winds can further confuse the issue, keep debris off-shore in the summer when the winds are from the north, and pushing it on-shore in the winter.