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Place 02 · Monterey Bay · Chapter 1 of 7
The Wind Turns Right
Push the ocean south and it goes west. The spinning planet is to blame.
About 15 minutes · 1 video · 1 live map · 2 quick activities
Start here
Blow on the ocean and it goes sideways
In 1893 the explorer Fridtjof Nansen froze his ship into the Arctic ice on purpose, just to see where the ice would carry him. He noticed something odd: the ice did not drift with the wind, but 20 to 40 degrees to the right of it. The answer turned out to be the spin of the planet, and it is the reason Monterey Bay is cold, green and full of whales.
Watch this
See it move
National Geographic — Coriolis Effect. Four people, one merry-go-round and a ball that refuses to go where it was thrown.
While you watch, look for
- Where the ball ends up compared with where it was aimed
- Whether the ball itself curves, or the people move out from under it
- Something you did not expect. Hold onto it.
The short version
Three things going on here
The spin
The ground is moving
At the equator the ground carries you east at about 1,670 km/h; near the poles, hardly at all. Anything traveling a long way slides over ground moving at a different speed, so its path bends: to the right in the Northern Hemisphere, to the left in the Southern. That bend is the Coriolis effect.
The belts
Winds come in stripes
Air warmed at the equator rises, and the Coriolis effect bends the flow into belts: trade winds near the equator, westerlies farther north and south. In summer a huge high-pressure system sits over the North Pacific and sends steady winds from the northwest straight down the California coast.
The twist
Water goes 90° right
The wind drags the top layer of the sea, which veers a little right; that layer drags the next, which veers a little more. Add up the whole spiral and the water moves at 90° to the right of the wind. So a wind blowing south along California pushes the water west, out to sea, and leaves a gap at the coast. Something has to fill it.
Photos: Zelch Csaba, Igor Passchier, Frank Cone / Pexels
Play with it
Watch the wind right now
This is a live wind map centered on the California coast. Find Monterey Bay and follow the moving streaks near the shore to see which way the wind is blowing today.
Live map: Windy.com, using ECMWF forecast data.
Two questions to answer while you are in there
- Which direction is the wind coming from along the coast at Monterey today?
- If the surface water moves 90° to the right of that wind, is it heading out to sea or toward the beach?
Try it yourself
Check yourself
Try it
Left or Right?
Eight quick calls: which way does it bend, and what happens at the coast?
Try it · interactive
Ekman Turner
Pick a wind direction along the California coast, watch where the surface water really goes, and see whether the coast gets upwelling or downwelling.
Open the Ekman Turner in its own window (opens in a new tab).
Words you will hear
Four terms, that is all
Coriolis effect
Earth’s spin bending moving air and water
Prevailing winds
The direction a place’s wind usually blows
Trade winds
Steady easterly winds on either side of the equator
Ekman transport
Net water movement at 90° to the wind
Check your understanding
Practice the whole chapter
Everything in this chapter, in eight quick questions. Retry as often as you like. Read the feedback on every answer, right or wrong, because that is where the learning is.
Practice
Practice: The Wind Turns Right
Eight questions covering the video, the three cards, the four terms and the interactive above.
If you want more
Go deeper
- Webb 8.2 — Winds and the Coriolis Effect — LibreTexts · 10 minutes
- Webb 9.3 — The Ekman Spiral and Geostrophic Flow — LibreTexts · 8 minutes
- Our World Ocean 12.2 — What Causes Winds? — LibreTexts · the friendliest version of this · 10 minutes
Photo credits (Pexels): Riccardo Bertolo, Dmitriy Ryndin, Zelch Csaba, Igor Passchier, Frank Cone.