Ken Buesseler climbed the highest peak on Enewetak Atoll and peered out over the expanse of paradise below. Offshore lay an azure lagoon inked with a dark-blue circle at its center. But this hole wasn’t natural. It was created by an atomic bomb—one a of series of 67 nuclear weapons tests conducted by the United States between 1946 and 1958 on the tiny Marshall Islands in the Pacific Ocean.
“It was a temporary fix,” said Buesseler, a marine chemist at Woods Hole Oceanographic Institution. As Buesseler stood atop the dome with his WHOI colleague Matthew Charette, palm fronds rustled softly in the distance. A Geiger counter in Buesseler’s hand clicked away. The clicks indicated whether the scientists were being exposed to radiation beyond safe background levels from the nuclear waste dump buried beneath their flip-flops.
“As an oceanographer who studies groundwater,” Charette said, “when I first saw the dome, I could immediately picture that it was filled with water beneath us, and with the rising and falling of each tide, the water was moving through that radioactive material. The dome made the atoll habitable, but the fact that it’s just a cap and not lined at the bottom means that it wasn’t really offering much protection.”
“In Japan, cesium levels have trailed off quite a bit since the accident,” said Buesseler, who began monitoring radiation just a few months after the Daiichi reactor meltdown. “But we’re not seeing the steady decrease we expected. This means that radiation is still leaking out. Anything we can learn from Bikini and Enewetak in terms of how the radionuclides are behaving could be helpful in Japan.”
Charette explained that their post-accident research at Fukushima showed them that wave and tide action has caused some of the highly contaminated water to wash up and filter through beach sands.
“These beach sands have become like a reservoir for cesium that will continue to be released back to the ocean over time,” he said. “But how long it will take for it to wash back out into the ocean is a key question. Our work in the Marshalls should give us some idea of the time scales involved for nuclear accidents and weapons tests and how long those radioactive elements may continue running off the land.”
Meanwhile, Buesseler wants to find ways to get back to the Marshalls to keep a watchful eye on conditions there. In particular, he worries about the dome.
“Sea levels have already risen to the point where they’re starting to wash up on the cap,” he said. “This is slowly starting to erode the edges, and at this rate, the whole thing might be completely submerged in fifty to one hundred years. It’s difficult to predict what that might mean in terms of additional radiation flow into the Pacific, so it will be important to study this moving forward. I’d go back in a heartbeat.”