"A significant amount of debris has already arrived on U.S. and Canadian shores, and it will likely continue arriving in the same scattered way over the next several years," NOAA officials said in a statement. "As we get further into the fall and winter storm season, NOAA and partners are expecting to see more debris coming ashore in North America, including tsunami debris mixed in with the 'normal' marine debris that we see every year."
After the magnitude 9.0 earthquake struck the east coast of Japan on March 11, 2011 and triggered a tsunami that killed more than 15,000 people, an estimated 5 million tons of debris was swept into the Pacific.
The waste includes everything from boats to kitchen appliances. And while around 70 percent of the litter sunk into the ocean, the rest -- some 1.5 million tons -- is scattered in the water and drifting toward North America.
"At this point, nearly three years after the earthquake and tsunami struck Japan, whatever debris remains floating is very spread out," NOAA officials said. "It is spread out so much that you could fly a plane over the Pacific Ocean and not see any debris, since it is spread over a huge area, and most of the debris is small, hard-to-see objects."
NOAA, which has been tracking the debris since 2011, recently updated its trace models to include the effect of wind on the waste.
"This new modeling effort gives us a better understanding of where the debris may have traveled to date, but it does not predict where it will go in the future or how fast it will drift," NOAA officials wrote in an update. "The new model takes into account that wind may move items at different speeds based on how high or low materials sit in the water."