Module 11 (Ocean Currents)

Surface ocean currents move warm and cold water around the globe

 Ocean currents affect the climate of the continents and the

productivity of different areas of the ocean

 Ocean currents are driven by a combination of factors: temperature,

gravity, prevailing winds, the Coriolis effect, salinity, and the location

of continents

Gyre – a large-scale pattern of water circulation that moves clockwise in

the Northern Hemisphere and counterclockwise in the Southern

Hemisphere

 Gyres redistribute heat in the ocean, just as atmospheric convection

current redistribute heat in the atmosphere

Upwelling – the upward movement of ocean water toward the surface as a

result of diverging currents

 Upwelling brings nutrients up from the ocean floor. These nutrients

support high productivity in upwelling zones which then supports large

fish populations

Deep ocean currents circulate ocean water over long time periods

Thermohaline circulation – an oceanic circulation pattern that drives the

mixing of surface water and deep water

 This circulation is most likely driven by cold salty ocean water sinking

near the poles and then warm rising ocean water at the equator

 There is concern that melting glaciers could shut down the

thermohaline circulation making some areas colder and others warmer.

The El Nino-Southern Oscillation is caused by a shift in ocean

currents

El Nino-Southern Oscillation (ENSO) – a reversal of wind and water currents in

the South Pacific

 El Nino occurs every 3-7 years and is the result of a weakening or

reversal of trade winds in the South Pacific

 El Nino can last for a few weeks to a few years and results in changes

in weather patterns around the globe

Wind directions

Wind strength

Precipitation

location

Water

temperature in

eastern Pacific

Water

temperature in

western Pacific

Change from

normal conditions

Normal

conditions

East to west

Medium

Western Pacific

Cold

Warm

N/A

El Nino conditions

West to east

Low

Eastern Pacific

Warm

Surface winds change direction

and warm water flows to eastern

Pacific