An environmental group has returned from another trip into the debris field in the North Pacific, where it found that home-grown garbage — not tsunami wreckage — is forming the bulk of the floating mess.

Mary Crowley, president of the U.S.-based Ocean Voyages Institute and founder of Project Kaisei, said Canadians became more aware of the problem of ocean trash after debris from the tsunami that hit Japan's northern coast in 2011 — including foam insulation and bottles, a motorcycle, and a large dock — began washing up on North American shores.

"I'm afraid the terrible tragedy of the tsunami debris and its magnitude is bringing the issue of ocean trash more to people's minds," Crowley said.

"I just think it's important that people understand the extent of the problem that's been developing over the last 50 years."

The Kaisei, the Ocean Voyages Institute's research ship, has made several trips over the past four years into what's called the North Pacific gyre in order to document and track man-made ocean garbage.

The Kaisei has made several trips over the past four years into the North Pacific gyre in order to document and track floating garbage. (Project Kaisei)

On every trip, the crew has been pulling up plastic waste at almost every sample point.

On its most recent expedition, the research team found that most of the garbage was not of Japanese-origin. It was from this side of the Pacific.

"It's this uncanny feeling 'cause you feel like you are looking in a garbage bin of your own garbage. Except it's all out there in the ocean," Crowley said.

Unwieldy problem

Janine Oros Amon, a spokesperson for Project Kaisei, said that while large pieces and intact articles are common, much of the gyre contains minute particles — the broken-down plastic of everything from fishing gear to throw-away cups.

Earlier this year, oceanographers released a study suggesting that the Pacific garbage patch, which was discovered in 1997, and a similar swath of plastic bits uncovered in 2010 in the North Atlantic, could be much larger than first thought.

In July, researchers with the 5 Gyres Institute said that the debris field from the tsunami may be more extensive than previously thought, only it may be hiding beneath the ocean's surface.

"This is something that is developing day-by-day, as we speak and as we go out in the ocean. There's a lot we don't know," Amon said.

Crowley said that governments around the world aren't doing enough to clean up existing garbage patches and to prevent more garbage from collecting in the ocean.

The crew of the Kaisei hopes that at least awareness of the tsunami debris will lead to solutions to deal with all of the trash.

With files from the CBC's Alan Waterman