Seabed scars raise questions over carbon-storage plan

Like a porpoise on the prowl, the sleek submersible HUGIN tracks its prey with sonar chirps. But the hunter set loose in the waters of the North Sea is not pursuing fish — the robot is trawling for geological clues that could help to determine whether billions of tonnes of carbon dioxide can be stored below the sea floor for centuries, keeping it from warming the planet.

Now, the latest data from the autonomous underwater vehicle and other tools deployed by the European Commission’s €10-million (US$13.8-million) ECO₂ research project suggest that the plan might not be so simple. The seabed is fractured and scarred more than researchers had appreciated — providing potential routes for CO₂ to leak from sub-seabed reservoirs where it is currently being stored. “We are saying it is very likely something will come out in the end,” says Klaus Wallmann, ECO₂ coordinator and a marine geochemist at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.