A phenomena related to the pressure dependence of the thermal expansion coefficient for the density of seawater. The dependence of the compressibility of seawater on both potential temperature and salinity means that water parcels displaced laterally without doing any work against gravity will not follow neutral surfaces defined in terms of spatially averaged (rather than instantaneous or local) potential temperature and salinity. They will move off this surface in a process called thermobaricity. For example, stirring by mesoscale eddies leads to a net motion of fluid across neutral surfaces. The process called cabbeling leads to the same result of moving fluid across neutral surface, although by mixing at the molecular level rather than by stirring.