English: The colouring of the world's oceans at the beginning of this animation represents surface water density, with dark regions being most dense and light regions being least dense (see the animation Sea Surface Temperature, Salinity and Density). Heights and (especially) depths of the oceans are greatly exaggerated (20x on land, 100x in oceans) to better illustrate the differences between the surface flows and deep water flows. Note that this animation presents the flows as described in current models and theories of the thermohaline circulation, not actual observed data. (The thermohaline circulation is a very slow moving current that can be difficult to distinguish from general ocean circulation, making it difficult to measure or simulate.)