Journey North International Plant Study

Tulips Tulips

Ocean Currents and Wind Patterns:
Factors that Control Climates

England and Iceland have much warmer and more moderate climates than would be expected just by looking at their location. Their latitude is similar to that of northern Canada, Labrador and Alaska, which experience a very different climate. Why?

The key to this puzzle lies in understanding the power of the wind over the vast, flat areas of ocean.

Currents and the Effect of the Earth Spinning
Over 70 % of the Earth's surface is covered with water. Wind helps this water to move and circulate. Wind powered surface currents move the majority of water from one place in the ocean to another. Surface currents which originate near the equator are warm and those that originate closer to the poles are cold currents.

Coriolis force
An apparent force that as a result of the earth's rotation deflects moving objects (as projectiles or air currents) to the right in the northern hemisphere and to the left in the southern hemisphere .

Ocean currents
credit US Navy Oceanographic office

These cold and warm currents are constantly moving and mixing. The Coriolis force causes currents in the open ocean north of the equator to move in a clockwise direction while currents south of the equator move in a counterclockwise direction. Study the map to see if you agree.
To better understand this phenomenon picture a spinning globe. Now picture pouring a glass of water down one side of the spinning globe. What pattern of water would you see when you stop spinning the globe? What would the pattern look like if you turned the globe upside down and repeated the experiment?

Land Masses
In addition to the Coriolis Effect, land masses or continents can influence ocean currents by causing them to be deflected from their original path. Study the map of ocean currents to see how the currents change directions as they are deflected from land masses.

Surface currents have a considerable effect on the climate of areas along their path. What can you learn from the map that would explain this phenomenon?

Try This!
You can make a model to explore wind-driven surface currents. With this model you can experiment with winds and currents and think about their affect on climate around the world. How would you design it to include some of the factors we learned about above (Coriolis effect and continent and landmass effects)?

Materials

9 x 12 inch aluminum pan
clay
flexible straw (the kind that’s bendable)
water
small piece of aluminum foil for rafts
ocean current diagram
wind pattern diagram
science notebooks

Explore

Using the clay make continents along both sides of the aluminum pan.
Fill the middle section of the pan with water.
Make 3 or 4 tiny rafts (approximately 1 cm square) out of the piece of aluminum foil.
Place your rafts in the “ocean.”
Bend the straw and place the long end of the straw (end furthest from the bend) in your mouth. Aim the short end of the straw at your “ocean” and blow gently causing a breeze. You do not need to blow hard enough to have a visible movement of the water. A current should begin to form.
Observe the path of the rafts and record your observations.
Repeat the process blowing in different directions. Record your observations in your journals.
EXTRA: Re-design your clay model to see what might happen when a continent is surrounded by ocean (like in Australia and New Zealand).

Journaling Questions

What factors influenced the path of the rafts?
Imagine that your model could show the effects (Coriolis) of the spinning Earth. How do you think this would affect your patterns?
How did the path differ when the winds blew in different directions?
Now can you answer this question?:
"England and Iceland have much warmer and more moderate climates than would be expected just by looking at their location. Their latitude is similar to that of northern Canada, Labrador and Alaska, which experience a very different climate. Why are they warmer?"

Adapted from SCiC Oceans and Jet Streams.