Saturday, February 18, 2012

Tsunami Debris

KITV-TV Honolulu.
Late last September the sailing vessel Pallada was headed home. The 354-foot, steel-hulled training vessel was returning from a good-will tour of several ports in the western US and Canada. En route to her home port of Vladivostok, the vessel suddenly encountered a large field of debris. The field included not only items you might commonly expect to come from a ship or dock -- boards, plastic bottles, fish net buoys, drums, boots -- but large items like refrigerators, TVs, and even fiberglass fishing boats. The Pallada spent nearly a week working her way west against the debris field, finally leaving it behind as she made way for Russia while the currents carried the debris toward North America.

Twenty-five million tons of debris were washed into the sea by the tsunami following the March 2011 earthquake in Japan. Researchers at the University of Hawaii estimate that the debris will first come ashore in the Midway Islands sometime this year, eventually reaching Hawaii in a couple of years, then the West Coast mainland a year after that. But there have already been reports of fish net buoys on the beaches of Washington, and the Hawaii researchers note that fishing vessels ripped off their moorings by the tsunami will reach the coast faster than less hydro-dynamic debris.

The ocean currents. Original map by
Michael Pidwirny
The Kuroshio and North Pacific Currents. The world's oceans are full of currents driven by the rotation of the earth, as well as differences of salinity and temperature in various parts of the oceans. The most famous of these is the Gulf Stream, which flows north along the east coast of North America, but the Pacific has its currents as well. The tsunami debris, once washed into the Pacific off the east coast of Japan, was picked up by the Kuroshio Current, which carried it north and east until it encountered the North Pacific Current, which carried the debris into the path of the Pallada and will eventually bring it into North America.

These currents are often cited as evidence that Japanese or Chinese mariners could have visited American shores before Columbus. What is known for sure is

  • Glass fishing net floats made in the 1920s and 1930s in Japan have become collectors items for West Coast beach combers and popular items in American antique shops, often selling for $50 or more.
  • In 1990, the container ship Hansa Carrier lost a container full of 80,000 Nike tennis shoes in the North Pacific. Scientists have used recovered shoes to more accurately map the Pacific's oceans currents.
  • In 1997, a racing sailor discovered what has come to be known as the Great Pacific Garbage Patch, an area north of Hawaii where currents have brought a large amount of floating plastic and other trash. The trash is trapped in an area where currents rotate around it, called a gyre.

Current Issues. The earthquake and tsunami also famously caused an emergency at the Fukushima nuclear plant, leading to concerns that some of the debris could be radioactive. When officers on the Pallada tested some of the debris they encountered, though, they found only normal levels of radiation.
But, the debris will still present several problems, including hazards to navigation and fishing, dangerous litter on beaches, and threats to animal life.

Related Posts
Ships, Toxic Wastes, and the Mob

Related Articles
University of Hawaii: Clearing Up Misunderstandings about Tsunami Debris on Course to the North American West Coast
Fox News: 25 Million Tons of Tsunami Debris Floating Toward US Shores
NASA Using Flotsam To Study Ocean Currents Across the Pacific Ocean, Plastics, Plastics Everywhere

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