Giant whirlpools of the northern oceans

Satellite-based map of visible eddies and currents in the North Atlantic. Invisible to satellites are recently discovered enormous whirlpools. Photograph: Nasa

Scottish researchers have discovered a series of previously unknown eddies, enormous slow whirlpools thirty kilometres across, mixing water from the Arctic and Atlantic Oceans.

Orbiting satellites would generally spot such eddies, from temperature difference with thermal imaging, or the change in water colour from different concentrations of marine life. In this case though, the eddies are masked by a layer of water the same temperature as the surrounding ocean. They were located instead by underwater “gliders,” small unmanned submarines gathering temperature and salinity data. The Scottish Association for Marine Science (SAMS) operates the gliders as part of a larger project.

Recovery of an underwater ‘glider’. Photograph: Joanne Hopkins / National Oceanography Centre

“It was surprising to find something so close to the surface that we couldn’t see using satellites,” says SAMS researcher Marie Porter.

The eddies are offshoots from ocean currents in the Barents Sea, where cooler and fresher Arctic water moves south and mingles with the warmer, saltier water of the Atlantic. The unexpected eddies suggest that previous studies may have underestimated just how much water is on the move.

The warm water is rich in nutrients while the cooler water is lifeless, so this mixing process is vital to the study of our ocean ecosystems. “If these eddies are widespread it would change our understanding of how nutrients are transported in surface waters,” says Porter.