In oceanography, the excess of the actual geopotential difference, between two given isobaric surfaces , over the geopotential difference in a homogeneous water column of salinity 35 per mille (%) and temperature 0 degrees. Also called anomaly of geopotential difference. The dynamic-height anomaly between two isobaric surfaces is the product of the mean specific-volume anomaly and the difference in pressure (in decibars); the latter is assumed to equal the difference in depth in meters.