Ocean CurrentsThe water in the ocean moves in giant

streams called currents.

Scientists place ocean currents into two major categories: surface currents and

deep currents.

Surface Currents

• Ocean currents that occur at 328 feet deep or above

• Include coastal currents and surface ocean currents

• Driven primarily by winds• Controlled by three factors

– air currents – Earth’s rotation – location of the continents.

Two types of coastal currents- longshore currents- wave approaches the

beach at an angle, forms sandbars- rip currents – form where underwater land formations

prevent waves from flowing straight back out to sea through channels that cut through underwater sandbars.

Surface Currents – Coastal Currents

The trade winds are located just north and south of the equator.

The Westerlies are located in the middle latitudes.

Surface Currents – Surface Ocean Currents

The Earth’s Rotation

As Earth spins on its axis, ocean currents and wind belts curve, the curving of the path is called the Coriolis effect.The wind belts and the Coriolis effect cause huge circles of moving water called gyres to form.

• Circular wind patterns that create spiral ocean currents

• Winds affect the upper 100 meters of water• Five major gyres flow north and south of the

equator– North Atlantic– South Atlantic– North Pacific– South Pacific– Indian Ocean

Surface Currents - Gyres

• Particularly strong current that is part of the North Atlantic gyre

• Carries warm water north for the Gulf of Mexico up the coast of the eastern United States and over to western Europe

Surface Currents – Gulf Stream

Continental Barriers

• The continents are another major influence on surface currents.

• The continents act as barrier to surface currents.

• When a surface current flows against a continent, the current is deflected and divided.

Salinity

• The water in polar regions has high salinity because of the large amount of frozen water.

• When water freezes, the salt in the water does not freeze but stays in the unfrozen water.

• Unfrozen polar water has a high salt concentration.

Turbidity Currents

• A turbidity current is a strong current caused by an underwater landslide.

• The landslide mixes the nearby water with sediment. The sediment causes the water to become cloudy, turbid, and denser than the surrounding water.

• The dense water mass of the turbidity current moves beneath the less dense, clear water.

Deep Currents

• Cold, dense currents far below the surface.• Deep currents move much more slowly than surface

currents.• Deep currents form as cold, dense water of the polar

regions sinks and flows beneath warmer ocean water.

Upwelling in the World Ocean

Upwelling refers to deep water that is brought to the surface.

Areas of upwelling are created by surface winds that pull water away from an area. This deficit of water on the surface invites water to come up from deeper regions

Upwelling in the World Ocean

• Upwelled water contains nutrients (nitrate, phosphate, silicate) and dissolved gases (oxygen and carbon dioxide) that are not utilized at depth because of a lack of sunlight.

Now on the surface, these nutrients and gases help to fuel photosynthesis by small algae called phytoplankton.