Sonar Spots Invisible Arctic Oil Spills
Boom in Arctic Ocean drilling means hazardous leaks under ice, hidden from sight—but not from sound

5-7-14 | Senior Editor Josh Fischman

The next big oil spill could be out of sight. Climate warming has packs of Arctic sea ice in retreat, opening up vast areas for oil and gas drilling. That is posing a new problem for spill detectors: There is still a lot of ice in the region, and people cannot see through it. Remember that giant oil slick on the surface of the Gulf of Mexico after the Deepwater Horizon oil rig blowout? Off the north coast of Alaska that kind of slick would likely be shielded by miles of drifting ice. “The risk of a serious oil spill in the Arctic is escalating,” the National Research Council warned in a report just last month. And, the council added, the U.S. is not ready to respond.

One answer could be to use sound rather than sight. High-frequency sonar chirps can reveal oil underneath ice, even when it is sandwiched between ice layers. “We were able to distinguish two different signatures: oil together with ice versus just ice alone,” says Christopher Bassett, a postdoctoral researcher at Woods Hole Oceanographic Institution. He and his colleagues presented their work Wednesday at the Acoustical Society of America’s meeting in Providence. Other researchers showed that sonar was sensitive enough to detect even tiny leaks, down to the level of individual oil and gas bubbles.