The system of surface and deep currents which make up the Atlantic Ocean circulation, a powerful heat conveyor belt and a poster child for abrupt climate change, is a more complex affair than straightforward textbook diagrams suggest.
Atlantic meridional overturning circulation is driven by cold water that sinks in the seas off Greenland and returns towards the equator at depth. How exactly this machinery works, and where its components sit, is interesting for a variety of reasons – not least in that it helps oceanographers look at the right spots for possible system failures.
That’s why a discovery, reported in Nature today [subscription], is worthy of note. Amy Bower of the Woods Hole Oceanographic Institution in Cape Cod, Massachusetts, and colleagues report that on its way back to the tropics cold Atlantic water takes a different pathway than previously assumed.
Bower and colleagues monitored the trajectories of drifting floats released from 2003 to 2006 into the southward-flowing Deep Western Boundary Current off Canada’s east coast. To their surprise, most floats soon drifted towards the high sea instead of strictly following the boundary current which has been thought to be the main pathway linking the Labrador Sea with the subtropical North Atlantic. Virtual floats ‘released’ in a three-dimensional ocean model at similar positions displayed the same preference for internal ocean pathways as did their material counterparts.
A secret interior ocean path? There you go, modelers!