The height of the instantaneous ocean surface above the geoid (the Earth’s gravity equipotential surface that approximates the ocean surface at rest) is known as Dynamic Ocean Topography (DOT).DOT contains contributions from wind and other high frequency effects like tides, currents, and the loading of atmospheric pressure. DOT is also known as Absolut Dynamic Topography (ADT) or Ocean Surface Topography (OST).

Mean Dynamic Topography (MDT) is the averaged dynamic ocean topography over a time period and it is considered semi-stationary. It corresponds to the ocean relief (therefor, it is also called Sea Surface Topography – SSTop) and the gradient is related to the time-mean surface geostrophic circulation. It is also related to upper ocean density (temperature and salinity) as well as the time-mean currents.

Global Mean Sea Level (GMSL) represents the spatial average of sea surface height over the global ocean, derived from satellite altimetry observations after applying the standard geophysical and instrumental corrections (e.g., tides and atmospheric effects). It is the primary indicator used to monitor long-term changes in global sea level and assess sea level rise. GMSL can be expressed in two equivalent ways: (1) as the global average of sea surface height referenced to a reference ellipsoid, or (2) as the global average of the sum of the geoid height and the DOT. Since the geoid evolves slowly on climate time scales, apart from relatively small changes caused by mass redistribution within the Earth system, most of the temporal variability in GMSL can be attributed to changes in the ocean surface, as represented by variations in DOT.