ABOUT 25 MILLION tons of debris was created in Japan following the 11 March earthquake and tsunami last year.

About 2 million tons of it – made up of various items including houses, fishing vessels and household appliances – remains in the Pacific ocean.

After just five weeks, the one-time necessities dispersed across the sea. This is how they have probably spread, according to researchers at the Univeristy of Hawaii International Pacific Research Centre.

Note: model may only be partially visible on iPhone or other smartphone screens.

As the model shows, the rubbish has already dispersed over an area 2,000 miles long and 1,000 miles wide. The projections were made using computer models and at-sea reporting from ships.

From this research, scientists believe that a small amount of debris could begin to wash ashore on the western-facing beaches of the main Hawaiian Islands in late 2012 or early 2013.

Canada and parts of the US west coast, and in particular Washington, could see waste from Japan hit its shores in 2013. The remaining debris field is subject to ocean current oscillations and is predicted to end up in the North Pacific Gyre by 2016.

The IPRC work predicts that the majority of the debris that does not sink will move into the already existing Garbage Patch (a large pile of floating rubbish) trapped by the Gyre between Hawaii and California.

It was thought that the Midway islands (as donated on the model) would see debris by the end of February but the waste started to move well north of the islands because of currents. However, sea movements have changed and debris is expected to land there shortly.

YouTube credit: USOceanGov

There have been reports of debris, including buoys, washing ashore on the beaches of Washington State’s Olympic Peninsula but none have been confirmed as tsunami-generated. Some experts believe the objects could not have reached the shore that quickly if only released on 11 March 2011.

However, others believe that surface-drifting debris has a faster trajectory. Oceanographer Curits Ebbesmeyer from the University of Washington says that plastic and fibreglass (such as that used for boat hulls) moves more quickly because they will be exposed to wind.

The debris, as disbursed as it is, will have a significant impact on wildlife in the ocean.

When washing ashore, it could also damage reefs, introduce invasive species and impact Hawaiian natives such as the albatross, monk seal, green sea turtle and other endangered creatures.

Derelict fishing gear also threatens seabirds and migratory species such as bluefin tuna, sea turtles, sharks and whales.

Another big question arising from the debris problem is whether America has to worry about radioactive debris. The answer is probably not. The debris washed out to sea before radioactive water was released at the Fukushima nuclear power plant so is unlikely to be contaminated.

Despite the small chances, macroalgae and crustaceans will continue to be monitored for contaminants.

Last October, a Russian ship found a 20-foot Japanese fishing vessel northest of Midway Atoll in the Pacific Ocean. The boat was tested for radioactivity but results came back normal.

The find – as well as an expedition by Hawaiin researchers – has confirmed the above model’s trajectory.

As the model by Drs Nikolai Maximenko and Jan Hafner shows, there is no one floating island of trash or even small numbers of dense patches. Just five weeks after the disaster, the debris was so dispersed that it could no longer be tracked by NASA or National Oceanic and Atmospheric Administration satellites.

Debris accumulated near the coast of Yamada, Japan following the tsunami. The debris has dispersed since this image was taken (Credit: US Navy Pacific fleet).

The researchers have now completed a survey fo the probable pathways of the debris as it moves towards the Hawaiin Islands. Eleven drifting buoys and 400 numbered blocks designed to simulate the motion of different types of debris have been deployed so monitoring can continue.

Boaters, fishermen and beachgoers have been asked to contact scientists if they find these blocks to help increase the understanding of the motion of debris and currents in the remote island region.

The Ocean Conservancy notes that although the tsunami is the latest high profile case, it is just a small part of the ocean’s trash problem. A tsunami’s worth of ocean trash is actually created each year by objects that are bought, used and thrown away.

Some plastic and other materials will float forever or their final destination will be the Garbage Patch, says Maximenko.

More: Full coverage and analysis one year after the Japanese tsunami>