ABSTRACT
Ocean waters are in a state of constant movement, stirred and mixed by two major forces: advective (those which cause displacement of water) and turbulent (involving random motion of water molecules). These mix huge quantities of water, together with their load of dissolved and suspended substances and gases, both vertically, between surface and deep waters, and horizontally, around the Earth. Because of the high heat capacity of water highlighted in Chapter 2, large-scale ocean circulation is responsible for approximately one-third of the long-term net transfer of heat energy from the tropics to the poles, and is therefore an important part of the global climate system. Furthermore, circulation in the deep ocean aerates bottom waters and causes mixing between the ocean basins. Thus the concept of ocean water movement is simple, but the details are horrendously complex because of the problems in identifying the shape and distribution of water masses. Complexity of water circulation is also due to the different scales of motion in the ocean, from small eddies up to ocean-scale gyres.
