What is polar creep?

In the waters of the Polar Regions, it has been said that water here has high salinity (therefore also a high density) because when the seawater freezes, most of the salt stays behind in the unfrozen seawater. As this water moves, it meets up with warmer water therefore it sinks deep beneath the surface; then it travels slowly to the equator. This movement of polar water is called Polar Creep.