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Main points of today's lecture:

• Patterns of atmospheric circulation.
• Effects of winds on the surface of the ocean.
• Coriolis effect and Ekman transport.
• Global surface-water current pattern.

Insights:

• As the sun warms up the surface of the earth at the equator, warm air becomes lighter and rises higher in the atmosphere where it flows towards the poles, cooling down and increasing in density. Cooler, heavy air sinks back to the surface of the planet and thence flows towards the Equator, creating an atmospheric cell circulation pattern, called a Hadley Cell.

• Winds are created by air currents flowing in the atmosphere from high-pressure regions towards low-pressure ones. Complex global wind patterns result mainly from the rotation of the Earth and from the uneven distribution of solar heat on it's surface.

• Free moving objects traveling on the surface of the planet experience a deflection in their trajectories, to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, due to rotation of the Earth. This deflection, which increases towards the poles, is called the Coriolis effect.

• Winds blowing across on the surface of the ocean make the water move. Water currents being dragged along by the winds will deflect to the right, due to the Coriolis effect; movement of these currents will drag the water particles immediately beneath them, which will also deflect to the right. This pattern repeats itself downward, creating a spiraling current whose speed decreases with depth, called the Ekman spiral.

• Circulation gyres are gigantic ocean currents flowing in circular trajectories from East to West along the Equator, towards the poles at the western ends of the ocean basins, to the east in the polar regions, and towards the Equator along the eastern boundaries of the ocean basins, where the cycle repeats again.

Have you thought about... (answers need not be submitted!)

• What's the role of the ocean in the atmospheric weather pattern?

• Does the rotation of the earth affect a boat sailing from Seattle to Hawaii?

• Why is the ocean water always so cold on the Oregon coast?

http://dusk.geo.orst.edu/oceans/surface_currents.html