What is a Current?
Ocean currents can be divided into two types of flow based on the forces that drive them. Most currents in the upper kilometer of the ocean are driven by the wind. Mixing drives deeper currents, which brings very cold dense water up to the surface. The dense water is replaced by cold dense water that sinks to the bottom near Greenland, Norway and Antarctica. Deeper water is affected by long variability of climate. Climate controls salinity and temperature of the water, which has everything to do with density. (See our page: Role of the Ocean and Weather.)
The arrows in the image represent the currents directions. The length of the arrows represents the currents speed. The colors in the image represent the topography of the ocean surface. The reds and yellows are the " hills " and the blues and purples are the " valleys. "