SME
Oceanography · Problem type
Gyres, western boundary currents and the conveyor
Use this for “Why is the Gulf Stream narrow and fast while the Canary Current is broad and slow?”
Explore
Trade winds push water west near the equator and westerlies push it east near 45°.
Ekman transport piles water toward each basin’s middle, so the sea surface there stands about 1 m high.
Geostrophic flow runs round that hill: clockwise in the north, counterclockwise in the south.
Assumptions
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Winds drive the surface gyres; differences in density, from temperature and salinity, drive the deep flow.
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The Coriolis parameter f grows toward the poles, and that change is what squeezes each gyre against its western side.
Topic check
See what you know: 5 questions on this topic
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Related lessons
Currents and circulation
Main lesson
Ekman transport and coastal upwelling
Use this for “A 10 m/s wind blows toward the equator along 1,000 km of coast at 40° N. How much water upwells?”
Volume transport in sverdrups
Use this for “A current 80 km wide and 400 m deep flows at 1.2 m/s. What is its transport in sverdrups?”