Ocean Currents
How deep does the affect of wind and the Coriolis effect go?
50-100 meters
How long does it take for deep-ocean currents to complete a cycle?
500-2000 years
Gyre
A circular rotation of wind or water that moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
How is energy transferred from the wind to the water?
As the wind blows, friction created between the air and water transfers energy from the wind to the water.
Why is the deep ocean water poorly mixed compared to the surface water?
Because it moves much more slowly than the surface water.
Give two examples of gold gyres.
Canary and California currents
Which direction do Gyres in the Norther Hemisphere rotate?
Clockwise
What direction to Gyres in the Southern Hemisphere rotate?
Counterclockwise
The constant blowing of the prevailing winds over the ocean causes what?
Currents and waves.
Thermohaline circulation
Deep sea currents that occur because of the difference in temperature and salinity in seawater (deep-sea conveyor belts).
What is the result of the wind / Coriolis effect called?
Ekman spiral
Compared to deepwater currents how to surface currents travel?
Fast
What directions to the "trade winds" blow?
From northeast to southwest (5-30 degrees N). Or from southeast or northwest (5-30 degrees S).
What direction to the "polar easterlies" blow?
From northeast to southwest (60-90 degrees N) and southeast to northwest (60-90 degrees S)
Which directions do the "westerlies" blow?
From southwest to northeast (30-60 degrees N). Or from northwest to southeast (30-60 degrees S).
Which way do the deep-ocean currents travel?
From the equator toward the poles.
Give two examples of warm gyres.
Gulf Stream and the Kuroshio Current
Are surface currents warm or cold?
It depends on where they are in the gyre.
What happens to the second layer of ocean water when wind moves the top layer?
It gets dragged along with the top layer, but because the force on the second layer is weaker it is affected more by the Coriolis effect and is deflected more to the right or left.
What happens to deep-ocean water from the poles that gradually warms as it reaches the equator?
It rises to the surface and travels back toward the poles with the surface currents.
What is one effect of surface currents?
Mix waters and distribute heat energy.
Do currents move with the same speed as the wind that causes them?
No the currents are slower than the winds, because energy is lost from friction.
How deep can wind driven surface currents go?
Not beyond 50-100 meters.
Compared to surface currents how do deepwater currents travel?
Slow
How do surface currents mix waters and distribute heat energy?
Surface currents move water thousands of miles from the tropics to the polar regions and back again.
Give an example of how surface currents affect climate and weather.
The Gulf Stream warms Newfounland, Iceland, and Great Britian.
Ekman spiral
The result of the spiral effect (wind / Coriolis effect) that movement of water is perpendicular to wind direction.
Why doesn't the water travel in the same direction as the wind?
The top layer of water moves, but because of the earth's rotation, the Coriolis effect steers the water to the right (in the Northern Hemisphere) and to the left (in the Southern hemisphere).
What two things can cause deep-ocean and surface waters to mix?
Thermohaline Circulation and winds (upwelling and downwelling)
What is another affect of surface currents?
They keep the surfaces of the ocean well mixed.
What causes wind patterns?
Uneven heating of the earth's surface and its rotation.
What are two types of vertical water movement?
Upwelling and downwelling.
What do surface currents affect?
Weather and Climate of the coastlines they travel to.
Downwelling
When winds blow against a continent this causes water to accumulate against the continent. The accumulated water will sink. This sinking water is called downwelling.
Upwelling
When winds blow away from a continent it cause water to flow away from the land, this leaves a gap. Water will flow up from the depths to fill this gap. This is called upwelling.
Geostrophic flow
Wind patterns push water toward the center of the ocean. When this happens the water's surface is higher in the center and water gets pulled downhill by gravity,
What three things cause gyres in the oceans?
Wind, the Coriolis effect and geostrophic flow.
Does upwelling or downwelling occur at the equator?
Yes, when winds blow parallel to the continents, upwelling will occur where the winds blowing in the same direction cause the water to diverge. Downwelling will occur where the winds blowing in opposite directions will cause the water to converge.
