How do the oceans move? Waves, Currents, Tides Unit 5 How do the oceans move? Waves, Currents, Tides

Water Movement Water in oceans can move in many ways Waves can be predictable or unpredictable in size and frequency Some are cyclic/predictable Currents-Global Predictable Movement Tides-Cyclic movement

Wave-An up-and down movement of the ocean surface Most are caused by wind

Ocean waves Any wave can be broken down into multiple parts

Parts of a wave Crest- the highest point of a wave Trough- the lowest point of a wave Wavelength- the distance between wave crests or troughs Wave height- the vertical distance between the crest and trough

How fast do the waves travel? Speed of a wave=velocity Frequency- The number of waves that past a given point in a given amount of time Ex: Number of waves that pass a given point in one minute

Wave frequency is a measurement of the amount of time it takes 2 wave crests to pass a point

How do the waves move? It looks like waves move side to side BUT…if you look at a boat in a wave it bobs up/down and doesn’t move side-to-side

Energy travels through the water as waves Water moves in circular motions, like the bottle shown, as the energy passes by An object in the water stays in the same place, bobbing up and down

https://www.youtube.com/watch?v=7yPTa8qi5X8 (on mute)

Wind causes ocean waves to form

Wind transfers energy to the water. http://www.rattlesnakecam.com/lake_movie_clips.htm Weak winds create ripples Strong winds create large waves Storms far out at sea create sets of waves called swell.

Ocean waves travel in the direction the wind blows. If the wind blows over a large area of water for a long period of time, large waves form.

https://www.youtube.com/watch?v=Fkwkn7vXpWI

Why do waves break? Waves feel the bottom and slow down when the depth is 1/2 the wavelength The waves break when the waves get too steep in the breaker zone.

https://www.youtube.com/watch?v=ouoodQg3XD0

In shallow water, the top of a wave travels faster than the bottom, causing the wave to “fall over” and break.

The “surf zone“ is where white foamy water washes up the beach after a wave breaks.

Hazards of the surf zone: A rip current is a strong narrow channel of water that flows from the surf-zone out to sea

Can waves break out at sea too? Yes! Whitecaps!

What about giant waves? Tsunami-Massive waves generated by a sudden disturbance in the Earth’s crust When a tsunami approaches shore it slows down Forward energy  Height VERY destructive!

Ocean Currents

Ocean Currents Mass movement or flow of ocean water River within the ocean (“Conveyor Belt”) Move in circles because of Coriolis effect Two types Surface Deep (or Subsurface)

https://www.youtube.com/watch?v=w_8mw-1HYFg

Ocean Currents Vocabulary Gyre: Nearly closed current system in the open ocean (giant circles) Clockwise pattern in N. Hemisphere Counter-clockwise pattern in S. Hemisphere Caused by Coriolis effect

Ocean Currents Vocabulary Continued… Meander – Bend in a current’s flow Ring – Large, whirl-like pattern (when a meander is cut off) Eddy – Small current Ring

https://www.youtube.com/watch?v=pysUORDq28Q

Surface Currents Horizontal, stream-like movements of water that occur at or near the surface of the ocean Can reach depths of several hundred meters

Surface Currents continued… Controlled by three factors Global winds Coriolis Effect Continental Deflections

Surface Currents continued… Global Winds Cause surface currents to flow in the direction the wind is blowing Coriolis Effect-Apparent curving of moving objects (ie- Water) due to the Earth’s rotation

Surface Currents continued… Continental Deflections Shape of continents change the direction of current flow

https://www.youtube.com/watch?v=gikHducfJG8 https://www.youtube.com/watch?v=UuGrBhK2c7U

Deep Currents Stream like movement of ocean water far below the surface Caused by changes in density Change in temperature Change in salinity

Deep Currents continued… Change in temperature Decreasing the temperature of water increases density Change in salinity Increasing the salinity of water increases density

THERMOHALINE CURRENTS!

Surface currents and climate Warm water currents On the east coasts of continents Bring warm water to colder regions

Surface currents and climate Cold water currents On the west coasts of continents Bring cold water to warmer regions

Upwelling The movement of deep, cold, nutrient rich water to the surface Nutrients promote growth of fish and plants Areas are important fishing grounds

Causes of warm and cold currents El Niño Change in the water temperature in the Pacific Ocean that produces a warm current

Causes of warm and cold currents La Niña Change in the eastern Pacific Ocean in which the surface water temperature becomes unusually cool

https://www.youtube.com/watch?v=wVlfyhs64IY https://www.youtube.com/watch?v=gpAkjSy_8iY https://www.youtube.com/watch?v=fAvk4RXrW_E

Ocean Tides The daily movement of ocean water that changes the level of the ocean’s surface

1.The gravitational attraction of the moon Tides are caused by 1.The gravitational attraction of the moon Moon pulls on Earth and Earth’s water 2. “centrifugal force” as Earth and the moon orbit around a common center of balance

High Tides are bulges of ocean water that occur on the side of the Earth facing the moon and on the side opposite

Low Tides are the areas between the bulges Low Tides are the areas between the bulges. Tides change as the Earth rotates between the bulges

Tidal Range is the difference in height between the high tide and low tide.

https://www.youtube.com/watch?v=dBwNadry-TU

Tides occur 50 minutes later each day. Since the moon moves along in its orbit around the earth each day, the earth must rotate an additional 50 minutes to catch up.

Spring Tides Sun Sun Moon Moon Are caused by the gravitational forces of the sun and moon pulling in the same directions (180 degrees) Produce very high and very low tides

Neap Tides Have small tidal ranges between high and low tides Less extreme tides Occur every 14 days during 1st and 3rd quarter moons

Neap Tides Sun Sun Moon Moon Are caused by the gravitational forces of the sun and moon pulling at 90 degrees from each other

https://www.youtube.com/watch?v=HdI_PyMFNro

At low tide in the Bay of Fundy, boats can be left setting on the bay bottom.

High tide arrives in 30 minutes in the Bay of Fundy, rising 20-50 feet High tide arrives in 30 minutes in the Bay of Fundy, rising 20-50 feet Tides of Nova Scotia

The Bay of Fundy is in Canada near northeastern USA

https://www.youtube.com/watch?v=lha-yk-rgq0 https://www.youtube.com/watch?v=l85Dk9LpIEs https://www.youtube.com/watch?v=rl0b6L2tDko

https://www.youtube.com/watch?v=-vwCj_c096s