An empty Japanese fishing boat drifting off the coast of western Canada could be the first wave of 1.5 million tons of debris heading toward North America from Japan's tsunami last March.

The wreckage from flattened Japanese coastal towns - including refrigerators, washing machines, televisions, roofs and fishing nets - is heading inexorably east across the Pacific and could arrive sooner than expected, according to the U.S. National Oceanic and Atmospheric Administration.

"The early indication is that things sitting higher up on the water could potentially move across the Pacific Ocean quicker than we had originally thought," said Nancy Wallace, director of NOAA's Marine Debris Program, which had forecast the appearance of tsunami debris on North American shores only in 2013.

"Those higher-wind, quicker moving items may actually be onshore much sooner - pretty much now."