Glossary

Meridional (north/south) overturning circulation in the ocean, which is quantified using the zonal (east-west) sum of mass transport in depth or density layers. In the North Atlantic, outside the subtropical regions the MOC (which, in principle, is a quantifiable parameter) is often referred to as thermohaline circulation (THC), which represents a conceptual interpretation. It should be kept in mind that the MOC can also contain shallower, wind-driven overturning cells (as can be found in the upper ocean layers in the tropics and subtropics), in which warm (and therefore lighter), poleward-flowing water is transformed into denser water and flows back equatorward in deeper layers.