Ocean Currents

1. Ocean Currents

2. Currents Currents are moving masses of water Ocean currents transport nutrients, heat and water, acting like the circulatory system of the ocean Currents influence climate and living conditions for plants and animals, in water and on land.

3. Gyres Currents are deflected by the continents which cause them to bend and create large current loops called circulation gyres. The Main Gyres include: North Pacific Gyre South Pacific Gyre North Atlantic Gyre South Atlantic Gyre Indian Ocean Gyre Ross Sea Subpolar Gyre

5. Gyres Within these gyres are the ocean currents of the world The Coriolis effect (due to the rotation of the Earth) move water clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere

6. Coriolis Effect Causes a surface water movement at 45� to the direction of the wind This movement is called Ekman Transport Each layer in the water moves at 45 � to the above water layer The deepest layers of the ocean will move in the opposite direction of the wind due to the Ekman Transport

9. Surface Currents The horizontal circulation of ocean waters are called surface currents. About 10% of the world ocean is involved in surface currents Surface currents is driven by wind friction which moves water at a depth of about 450 m

10. Surface Currents The winds that most affect the oceans' currents are: The Westerlies which blow west to east in the temperate regions (30-60� latitude) The Trade Winds which blow east to west at ~15 � latitude The Easterlies which blows east to west in the polar regions (60 - 90� latitude)

11. Surface Currents impacted by Westerlies and Trade Winds The currents impacted by the Westerlies and Trade Winds are the fastest and deepest currents These currents are moving the warm water north There are 5 large warm currents The largest current is the Gulf Stream It moves at ~2 m/s at a depth of 450 m It can travel up to 160 km/day

12. Surface Currents by the Equator Currents around the equator (impacted usually by Trade Winds) are accompanied by countercurrents and undercurrents Countercurrents are currents flowing on the surface in the opposite direction Undercurrents are currents flowing in the opposite direction but under the surface currents

14. Surface Currents impacted by Easterlies These currents contain colder water from the polar regions to the equator There are 5 main cool currents They are shallow and very broad (sometimes up to 1000 km in width) Slow surface flow compared to westerly currents Ex. Canary Current flows at 1 m/s compared to the Gulf Stream at 2 m/s

17. Deep Ocean Currents and Thermohaline Circulation Differences in water density affect deep ocean currents Movement of surface ocean water to the bottom of the ocean and movement of deep ocean water to the surface. It is impacted by temperature and salinity It is responsible for vertical movement and circulation of oceans

18. Thermohaline Circulation Upwelling When nutrient- rich water from the bottom of the ocean moves up to the surface. Downwelling When the water from the surface of the ocean moves downward

19. �Global Conveyor Belt� An example of �Thermohaline Circulation� occurs when deep water forms in the North Atlantic and sinks because of density It starts to moves south, and circulates around Antarctica, and then moves northward to the Indian, Pacific, and Atlantic basins.

21. Other causes of currents Include tides, rain, runoff, and ocean bottom topography. Topography is the surface features of a place. Ocean topography includes slopes, ridges, valleys, and mountains! All these things are found at the bottom of the ocean, and can influence currents.

22. How do we study currents? Release studies which use drift bottles or drift sensors (float methods) Flow methods are used to measure the speed of currents as it flows past a fixed object Scientists are now using CFC�s to measure flow because they are easy to track Satelites are used to measure temperature, topography and color