2. Factors That Affect Surface Currents Surface Currents flow in the upper 1000 meters of the ocean. They are driven by the wind. It is a transfer of energy from the air to the water and then back again. Section 1 Ocean Currents A current is a continuous flow of water along a broad path in the ocean. It can be at the surface or it can be below the surface. There are two main categories for ocean currents: Surface Currents Deep Currents

3. Global Wind Belts Trade Winds: They are steady winds that always blow from North East in Northern Hemisphere and South East in the Southern Hemisphere. In both hemispheres they push currents westward across tropical latitudes of all three major oceans. It is the historical path that the early trade ships sailed; they used the prevailing winds to help push them along quicker in order to shorten long trips. Westerlies: They push ocean currents eastward toward higher latitudes. They are w arm water currents that flow on West side of the oceans. Continental Barriers Continental barriers deflect and divide the currents. The Coriolis Effect The Coriolis Effect forms gyres (huge circles of moving water) Northern Hemisphere the currents flow Clockwise. Southern Hemisphere the currents flow counter- clockwise. This difference is due to the spinning (rotation) of the earth on its axis.

5. Equatorial Currents Warm water currents re produced here. This makes the Western side of ocean basins have WARM currents moving away from the equator. The Eastern side of the ocean basin has COLD currents moving toward the equator. Currents in the Southern Hemisphere The Antarctic Circumpolar Current (West Wind Drift) Currents in the North Atlantic Gulf Stream The Gulf Stream is the swift moving, deep, warm Atlantic current that flows along the Eastern Seaboard. It s tarts in the Caribbean Sea and then becomes the North Atlantic Drift traveling all the way to Iceland and England. This keeps some areas warmer than other locations at the same latitude. (Palm trees in Ireland) In the North Atlantic if also forms a gyre that is in the middle of the ocean, called the Sargasso Sea. It is a warm calm center of the ocean. Currents in the North Pacific Kuroshio Current in North Pacific is similar to our Gulf current.

6. Major Surface Currents

7. Deep Currents Deep currents are usually cold water currents. Cold Currents flow toward the equator on the Eastern side of the ocean basins. The three dense currents are Antarctic Bottom Water, North Atlantic Deep Water, and the Antarctic Intermediate Water. Density Currents flow under the surface due to density differences. They can stay submerged for 500 – 2000 years and connects with global surface currents to form circular paths. They are slow moving and the only source of oxygen for deep-sea life because they retain what they absorb (salinity, oxygen, temperature and density). Evaporation can cause them. Antarctic Bottom Water The densest water is found in polar-regions due to intense cooling and freezing. When sea water freezes the salt is left behind, increasing salinity.

8. North Atlantic Deep Water Canary Current In the North Atlantic Bengula Current In the South Atlantic Labrador Current Found off the coast of Newfoundland. It can carry icebergs (remember the Titanic). When it reaches the Gulf Stream (warm) the mixture produces the thickest fog in the world. Turbidity Currents We learned in last chapter, caused by underwater sediment slides. Counter-Currents They are currents that flow in the opposite direction of the wind related currents. They can flow at or beneath the surface. They occur because steady winds pile water up on either side of an ocean basin

9. Section 2 Ocean Waves A wave is the periodic disturbance in a solid, liquid or gas as energy is transmitted through a medium. Wave Height is the difference between the crest and trough Crest is the high point of a wave Trough is the low point of a wave Wavelength is distance from one crest to the next crest Period – is the time it takes a wave to pass a point Speed = Wavelength ex. 150 kilometers = 12.5 km/minute Period 12 minutes

10. Wave Energy Waves form from friction between the wind and the water. The longer the winds blow, the larger the wave becomes. Water Movement in a Wave As a wave moves across the surface of the ocean, only the energy of the wave, not the water, moves in the direction of the wave. The water molecules within the wave move in a circular motion. During a single wave period, each water particle moves in one complete circle. At the end of the wave period, a circling water particle ends up almost exactly where it started. Because waves receive their energy from wind pushing against the surface of the ocean, the energy received decreases as the depth of the water increases.

11. Wave Size There are three factors that determine the size of a wave: wind speed, length of time the wind blows and the fetch. Fetch is the distance that the wind blows across an area of water. The larger the fetch, the larger the waves become. White Caps A white cap occurs when the wind blows the crest of a wave off. Wave Swell is when a steady smooth wave comes at regular intervals up to 10 seconds apart. They are caused by winds and storms far away.

12. Waves and the Coastline In shallow water, the wave bottom will touch the ocean floor and will cause it to slow down and eventually break. Breakers Breakers begin to form as a wave approaches the shore line. The curl as they slow down and crash on the beach. Other actions that a wave takes are Swash and Backwash. Swash is the motion of water going up the beach. Backwash is the motion of water going back down the beach.

13. Refraction Refraction is the process by which the ocean waves bend directly toward the coastline as they approach the shallow water. Undertows and Rip Currents Undertows are seldom strong and will occur in areas along the shorelines that have a steep drop-off. Rip Currents flow perpendicular to the shore and are strong.

14. Long Shore Currents A long shore current is a current that flows parallel to the shoreline. These currents are very strong and can carry large amount of sand, often forming sandbars. Tsunamis A tsunami is a wave formed from an underwater earthquake. Tsunamis may travel at speeds of up to 890 km/h (as fast as a jet airplane). A Tsunami as a Destructive Force Near the shore, the height of a tsunami greatly increases as the tsunami's speed decreases. As a tsunami approaches the shore, it may reach a height of 30 to 40 m. The arrival of a tsunami may be signaled by the sudden pulling back of the water along the shore. This pulling back occurs when the trough of the tsunami arrives before the crest. If the crest arrives first, a sudden, rapid rise in the water level occurs.

15. Section 3 Tides A tide is the periodic rise and fall of the water level in the oceans. High Tide – moon pulls water to itself Low Tide – water leaves the sides Causes of Tides In the 1600’s Sir Isaac Newton discovered that gravity pulled on the water along the coastlines. The gravitational pull of the moon on the Earth’s water caused the tides. Behavior of Tides Earth’s rotational period is 24 hours and the moon’s orbit around the earth is approximately 29 days. Because the Earth and the moon orbit in the same direction that the Earth rotates, all areas of the ocean pass under the moon every 24 hours and 50 minutes. This makes the tides change every 6 hours and 12.5 minutes. Each high tide gradually turns into a low tide, and each low tide turns into a high tide. The time of the high and low tides change each day.

16. Spring Tides Spring tides are when the sun is at a 0 o or 180 o to the moon (New and Full). The pull is stronger which makes high tides higher and low tides lower. Neap Tides Neap tides are when the sun and the moon pull against each other at 90 o during the quarter moon phases the high tide is not very high and the low tide is not very low. This occurs at the quarter and ¾ phases.

17. Tidal Variations Atlantic Coast has two high tides and two low tides each day Gulf of Mexico has one high and one low tide each day Pacific Coast has a mixed pattern. They have Very High tides followed by very low tides and lower high tides followed by higher low tides. Tidal Oscillations Tidal oscillations are the slow rocking motion of the ocean water that occurs as the tidal bulges move around the ocean basin. Tidal Currents Tidal currents are the movement of water toward and away from the coast as a result of the rise and fall of the tides. Ebb Tide when the water moves toward the oceans Flood Tide is when the water moves toward the coast Slack Tide is when there are no currents