Up to 18 million tonnes of debris from this year's devastating Japanese tsunami are being carried across the Pacific Ocean and could hit British Columbia shores within three years.

Scientists at the University of Hawaii say that a massive field of debris is spread out across an area that is roughly 3,200 kilometres long and 1,600 kilometres wide.

That debris field is currently located between Japan and Midway Atoll.

It was recently spotted by a Russian ship, which saw a refrigerator, TV and other appliances floating together in an area where the scientists had predicted the debris would be.

The presence of a fishing boat that has been traced to the Fukushima Prefecture served as further proof that the debris originated from the Japanese disaster.

"From a scientific point of view, it was confirmation that our research was doing something right," said Jan Hafner, a scientific programmer who worked on the projections as to where the debris would be headed after the tsunami, in a recent interview with The Associated Press.

The scientists believe the ocean currents will carry the debris to Hawaiian shores by 2013, before reaching the West Coast.

Hafner said it is not clear how much of the debris is still above water, as an unknown portion of it has likely sunk.

"It's a common misconception it's like one mat that you could walk on," he said.

Hafner and a colleague who put the debris projections together are now calling for sailors and boaters to report more data on the debris in the sea.

"We are trying to get across our message that it is coming and it's about time to start planning some action," he said.

The tsunami in Japan was triggered by a massive 9.0-magnitude earthquake that struck on March 11.

The twin disasters left more than 21,000 people dead or injured, while creating a major emergency at a nuclear power plant that was severely damaged by the tsunami and quake.

Japan's government has said the disasters caused more than $300 billion in damage.

With files from The Associated Press