Japan’s 2011 Fukushima nuclear power plant meltdowns blanketed snow and ice around the Northern Hemisphere with a thin layer of light radioactivity dubbed the Fukushima Layer. The nuclear disaster was triggered by a massive thrust earthquake that spawned a devastating tsunami, which knocked out the nuclear plant’s main cooling system. The resulting meltdowns contaminated groundwater around the plant and spewed radioactive particles into the atmosphere. It was thought that the airborne radiation would have faded by now. But scientists writing in Environmental Research Letters say the thawing and melting of glaciers around the hemisphere has made the radioactivity more concentrated, creating a lingering layer of contamination.