Currents and Wind

The Earth is Spinning… Because

Earth spins, winds and water appear to be deflected in a curved motion

This is called the Coriolis Effect

Which way do things

not connected to

Earth get deflected

in the northern

hemisphere?

In the southern hemisphere?

RIGHT!

LEFT!

DON’T FORGET WE’RE TALKING ABOUT THE DEFLECTION FROM THE PERSPECTIVE OF WHERE THE OBJECT IS MOVING FROM! Look at this picture and see that in the north, the arrows curve to the right from the point of origin and to the left in the south.

WindWinds drive ocean surface currents.

Because wind is not connected to Earth, it is effected by the Coriolis Effect

What is wind?When the sun heats the surface of Earth, the air

closest to the ground also gets heated.

When air is heated it becomes less denseand begins to rise.

Cooler air moves into itsplace.

This is wind.

Most winds are named by what direction they come

from.

Trade Winds

Trade Winds

Westerlies

Westerlies

Polar Easterlies

Polar Easterlies

How do you think the trade windsgot their name?

These helped develop tradeRoutes centuries ago.

Earth’s Major Wind Patterns

Doldrums and Horse Latitudes Doldrums

is defined as a boring and monotonous time.

The area along the equator doesn’t have much wind, so it is called the doldrums.

Sailing vessels often got stuck here for weeks because of lack of wind.

Doldrums and Horse Latitudes Another area of

calm air with little wind occurs along the 30 degree latitudes.

Supposedly, sailing ships that got stuck here would throw horses overboard to make the ship lighter in hopes of sailing out of this calm area.

Surface CurrentsA current is a moving fluid (liquid or gas)

Winds produce currents in the ocean when they blow from the same direction for a long period of time.

Ekman TransportWhen wind moves across

water, the water moves at a 20-45° angle to the wind.

That water causes the water around to move at angle to itself, and so on and so on.

Eventually, there is water flowing in the opposite direction of the wind, but it is much deeper under water.

On average, the water moves at a 90° angle to the wind. (To the right in the North and to the left in the south.)

GyreA gyre is a circular current formed by a

combination of the rotation of the earth, prevailing winds, and land masses that interfere with the movement of water currents.

Major GyresWarm water

is deflected away from the equator by wind.

Cool water is deflected from the poles toward the equator by winds.

Thermohaline Circulation Thermo- means heat and -haline means salt

At the poles, water is very cold

When the water freezes to form ice, it excludes salt, so the ice is all freshwater

The water left behind is extremely salty and cold

This combination makes the water very dense, so it sinks.

It slowly travels along the floor of the ocean toward the equator, and warmer, less salty water flows in to replace it.

This is a VERY slow process. Surface currents average 6 mph, but it is estimated that it takes 600-800 years for the entire thermohaline cycle to complete itself.