Major ocean currents have shaped Earth's climate and biota. Changes in currents have affected the onset and termination of Glacial Ages and thus shaped the terrestrial surface of Earth.

> through the distribution of massive quantities of heat ocean currents moderate the extremes in temperature that would occur in their absence
> many species of vertebrates and invertebrates as well as plants use the ocean currents to move their young or seeds over great distances

> thermal energy causing density changes are the primary forces that propel ocean currents
> winds and changes in salinity (density) also are factors in current dynamics

> the spinning of  Earth creates a Coriolis effect that also shapes currents
 direction

 

Red to Violet/Grey warm to cold temperatures of the oceans follow equatorial / polar as well as current trends	The Coriolis effect tends to deflect currents to the right as they flow N/S in the Northern hemisphere and to the left in the Southern Hemisphere
The Northern and Southern Gyres	The Coriolis Effect can cause upwelling (or down welling) of currents. Upwelling can lift nutrients from the ocean floor nourishing phytoplankton the base of the food chain.

South and North Equatorial Currents, Equatorial Countercurrent, Golf current (Atlantic), Canary Current (Europe) Kuroshio (Japan, China), California Current (U.S.A.), South Indian Current (Indian Ocean), Benguela Current (Africa), Antarctic Circumpolar Current.

The Great Conveyer that is driven by thermal energy and changes in salinity that both affect density is a sensitive system that could be switched off if increases in Green House gases increase Earth' temperature past a critical point. This is a good example of what some fear could be a rapid change in Earth's climate due the sudden change in an ocean current that would leave Europe in the deep freeze.