In addition, it is thought that extensive salinity stratification can lead to a reduction in the meridional overturning circulation (MOC) through the slowing of thermohaline circulation. Increased stratification means that there is effectively a barrier to subduction of parcels of water; isopycnals effectively do not outcrop at the surface and are parallel to the surface. The ocean, in this case, can be described as "less ventilated", and this has been implicated in the slowing down of the MOC.