Large-scale ocean circulation

Absolute Dynamic Topography

A view of the global ocean circulation shows currents swirling around the hills and valleys at the sea surface. In the Northern Hemisphere, currents flow around hills in a clockwise direction and in an anticlockwise direction (the opposite occurs in the Southern Hemisphere) around valleys. These currents form gyres on either side of the equator. Planetary waves are other large-scale phenomena that are less easy to see on an instantaneous map, but nonetheless they too have a global impact.

  • Mean Dynamic Topography

    The major ocean currents generated by prevailing winds are deflected from their course by the shoreline, and by the Earth's rotation. Ocean circulation thus causes water to accumulate at the western edge of ocean basins, forming reliefs in the ocean surface proportional to the speed of the currents. By measuring sea level variations, altimetry satellites enable us to observe ocean currents.

  • Currents around the world

    Some examples of currents around the world : Gulf Stream, Kuroshio, circumpolar current, monsoon currents, South Indian Counter Current, Leeuwin current.

     

  • Rossby, Kelvin waves

    These are either Rossby waves, which go from East to West or Kelvin waves which move in the opposite direction. They intensify currents such as the Gulf Stream or the Kuroshio.

     

  • Thermohaline circulation

    The Greenland sea is a key zone of planetwide ocean circulation, i.e. thermohaline circulation. There, cold and salty Atlantic waters sink to the bottom of the ocean, like a waterfall. Descending, cold water mixes with ambient one, creating subsurface eddies that altimetry data analysis able us to detect.

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