One man's trash is another man's..
way to track ocean currents:
In January 1992, a freighter crossing the Pacific from Hong Kong to Tacoma, Wash., ran into rough weather near the International Date Line. As the ship heaved through the storm-tossed seas, several cargo containers on deck—including one filled with tens of thousands of plastic tub toys—came loose, fell overboard, and broke apart. Seven months after the spill, the plastic ducks, beavers, turtles, and frogs began washing up on beaches. Scientists who track ocean currents were ecstatic..
.. Worldwide, about 10,000 cargo containers fall overboard each year. In most parts of the world, the dispersal of flotsam isn't of major interest to researchers. But along the bustling trade routes that link eastern Asia to North America, the tennis shoes, kids' sandals, hockey gloves, and other stuff that drops off ships is enabling scientists to fill in details of how the Pacific Subarctic Gyre works.
10,000 cargo containers is a whole lotta junk. More interesting, though, is how long some of this stuff hangs around.
In January 2000, a cargo box contributed another batch of accidental tourists. It contained children's sandals that, like the sneakers, carried code numbers linking them to the particular shipment. Ten of the sandals have washed ashore on Alaska's Kodiak Island—some in 2001, others in 2005. None showed up in the intervening years.
The flotsam-recovery database .. also includes information from some of the 19,000 beer bottles—containing identification numbers and contact information—that oceanographers threw off a boat far out in the Gulf of Alaska between 1956 and 1959. The last recording of one of these bottles washing ashore was in 1972.