Oceanography (Jun 2012)
Journey to the Center of the Gyre: The Fate of the Tohoku Tsunami Debris Field
Abstract
The 9.0 magnitude Tohoku earthquake that struck off the coast of Japan on March 11, 2011, was the fourth largest earthquake in recorded history and the largest ever to hit a densely populated region (Bertero, 2011; Lekkas et al., 2011). The ensuing tsunami inundated an area of about 561 km2 (Geospatial Information Authority, 2011), washing away an estimated 24.9 million tonnes of debris, including wood, sediments, plastics, industrial chemicals, and structural components (Oh, 2011). Two weeks following the tsunami, the meltdown of the Fukushima Daiichi nuclear reactors released radioactive elements into the atmosphere and coastal waters. Atmospheric deposition was found to be an important source of radioactivity in surface waters and may have contaminated the debris field, although the extent of this contamination remains unknown (Buesseler et al., 2012; Honda et al., 2012).Here, we follow the debris field along its predicted path from its source in Japanese coastal waters through the Kuroshio-Oyashio Extension, the North Pacific Current, and the California Current. From there, it will loop back toward the Hawaiian Islands, ultimately accumulating in the North Pacific Gyre (International Pacific Research Center, 2011b; Figure 1). Relying on precedents from previous natural disasters and ongoing observations, we attempt to predict the impact of this debris field on marine and coastal ecosystems in each of these regions. We predict that the Tohoku debris field will create a rare perturbation for ecosystems interconnected across the North Pacific, exacerbating the accumulating human impacts on the world ocean.
