Surface Currents

CurrentsCurrent: A horizontal movement of water in a

well-defined pattern.In the ocean, there are surface currents and deep

currents.

Surface CurrentsWhat do you think causes surface currents?Answer: WIND. What do you think affects the direction surface

currents flow?Answer: Controlled by 3 factors: Air currents

(such as major wind belts), Earth’s rotation (Coriolis Effect), and the location of the continents (deflect and divide currents).

Atmospheric CirculationDrives Surface CurrentsDrives El Nino, La Nina (we will look at this next class).

Drives Monsoons and Hurricanes (we will also look a these in more detail).

Layers of the Atmosphere

Label the wind belts, pressure zones, and calm winds on your sheet.

Global Winds over the Pacific

Atmospheric Circulation CellsHadley Cells: 0-30

degrees (tropics). Brings warm, moist air from equator towards the poles.

Ferrel Cells: 30-60 degrees (mid-latitude). Cold air moves from the poles toward the equator.

Polar Cells: 60-90 degrees. Cold air ascends and moves toward the poles.

Global Winds and Surface Currents affected by Coriolis Effect.

Coriolis Effect: The bending of winds due to Earth’s rotation.

Winds and Currents bend to the right (Clockwise) in Northern Hemisphere.

Winds and Currents bend to the Left (Counterclockwise) in Southern Hemisphere.

Doldrums and Horse LatitudesDoldrums: Zone of calm equatorial winds where two Hadley cells meet. The word doldrums means gloomy, perhaps because sailors felt that way when they were stuck here. Horse Latitudes: Zone of high pressure where Hadley Cells and Ferrel Cells meet. Called this because sailors would get stuck and have to either throw their horses overboard or eat them.

World Surface Currents

Gyres: Circular flow around an ocean basin. Made of multiple, connected currents.

Heat transfer by surface currents What do you notice about

how surface currents transfer heat?

Answer: Warm water is brought from equator towards poles. Cold water from poles to the equator.

What causes England to be fairly warm even though it is the same latitude as Canada?

Answer: Warm water from Gulf Stream.

Western and Eastern Boundary CurrentsWestern Boundary

Fastest (2 m/s) and deepest (up to 1500 feet)

Western boundary of ocean basins or eastern boundary of continents

Move warm water from equator towards the poles

Includes the Gulf Stream and the East Australian Current (EAC).

Eastern BoundaryShallow and slowerEastern boundary of ocean

basins or western boundary of continents

Move cold water from the poles towards the equator

Includes the Canary current off the coast of Europe and the Humboldt Current off the coast of Peru.

World Surface Currents

Eddies:Turbulent rings of circulating water on the edge of a current.

Formed by abrupt changesin water temperature,speed, and direction.• Only form along westernboundary currents.

Gulf Stream Eddies