The reason is of course the very low data density in the deeper ocean regions, which does not allow us to resolve the high spatial gradients associated with turbulent features. The landmark maps of the water masses of the Atlantic Ocean produced by W¨ust (1935) more than 70 years ago are out-standing historical examples; their smooth property fields, which were constructed from a total of some 250 observation points spread over the entire Atlantic Ocean, suggest uniform spreading of Antarctic Intermediate Water and Antarctic Bottom Water from the Southern Ocean towards the equator and smooth movement of North Atlantic Deep Water in the opposite direction.