Ocean currents Ocean Waves Tides Movement of Oceans Ocean currents Ocean Waves Tides

22.1 Ocean Currents Currents-mov’t of ocean waters in giant streams. Two types of major currents are surface and deep currents.

Surface Currents Move on or near the surface of ocean and are driven by winds.

Deep Currents Move more slowly beneath the surface of the ocean and are caused by differences in the density of water.

Surface currents Wind is the driving force. Most are the result from global wind patterns.

Factors affecting ocean surface currents Controlled by wind belts, earth’s rotational effects, and location of the continents. Global wind belts that most directly affect the flow of surface currents are trade winds and westerlies. Trade winds located n & s of equator. Westerlies are located in the middle latitudes.

Trade winds Northern Hemisphere, they blow from southwest, pushing currents eastward across the Atlantic and Pacific. Southern Hemisphere, they blow from the northwest, pushing the West Wind Drift, around the world. West Wind Drift is the earth’s largest current.

Coriolis Another factor controlling surface currents. It is the deflection of the earth’s winds and ocean currents caused by the earth’s rotation. Creates huge circles of moving water called Gyres.

Gyre Huge circles of moving water Winds flow counterclockwise in Southern Hemisphere. Winds flow clockwise in the Northern Hemisphere.

Third Major Factor Continent is the third major factor that effects surface currents. When current flows against a landmass, it is deflected and divided.

Equatorial & Equatorial Countercurrent Currents Warm water currents found in the Pacific, Atlantic, and Indian Oceans. Flows westward. Weaker current that lies between these westward flowing currents. It flows eastward.

Gulf Stream Swift warm current that pushes water through the Caribbean Sea and the Gulf of Mexico. It also flows around the tip of Florida and up the eastern seaboard. Meets the cold waters of the Labrador Currents. Widens and speed decreases south of Greenland, until it becomes the North Atlantic Drift.

North Atlantic Drift Vast, slow moving warm current that comes off of the Gulf Stream. A drift is a weak current. It splits and one part becomes the Norway Current off the coast of Norway. The other current split becomes the Canary Current.

Four Currents that form the North Atlantic Gyre Gulf Stream Canary Current North Atlantic Drift North Atlantic Equatorial Current Center of the gyre lies the Sargasso Sea. Sargasso Sea is a vast area covered in brown seaweed called Sargassum float.

Japan Current Pacific equivalent of the Gulf Stream. Flows northward along the east coast of Asia.

California Current Waters from the Japan Current flow toward the North America as the North Pacific Drift, eventually flowing southward as the cool California Current. Along the California coast

Currents in Southern Hemisphere Move counterclockwise. In southern regions of the big three oceans, constant westward winds produce the West Wind Drift. Largest current in the world.

Patterns of Surface Currents in Indian Ocean Southern part-currents follow a circular, counterclockwise gyre. Northern part-currents are governed by winds called monsoons. Monsoons are winds which change direction with the seasons.

Deep Currents Movement of polar waters is the result of density differences. Water molecules contract, when the water is cooled. Water molecules expand, when water is warmed. Higher density of polar waters is a result of an increase in salinity of water.

Antarctic Bottom Water Close to freezing temperature. Salinity is higher. These two factors make the water off the coast of Antarctica the densest and coldest ocean water in the world.

Turbidity Currents Are thought to cause the deepening of submarine canyons. Deep ocean currents are the result of changes in density of ocean water.

Bell Ringer Passage 2 and questions 8 on Tuesday. Pg 44-45 Earth Science test on chapter 22 will be Friday from worksheets and chapter questions. Study Guide for 9wks test will be given out Friday. Use your old notes to answer.

22.2 Ocean Waves A wave is a periodic up and down movement of water. Way of transferring energy.

2 Parts of a wave Crest-highest point of a wave. Trough is the lowest point between two crests. Scientists study to learn characteristics.

Wave Terms Wave height is vertical distance between the crest and trough of a wave. Wavelength is the horizontal distance between two consecutive crests or between two consecutive troughs. Wave period is the time it takes for one complete wavelength to pass a given point.

Wave speed = wavelength/perod Example: Wavelength of 216 m and a period of 12 s has a speed of: 216 m/12 s= 18m/s

Swell Group of long, rolling waves that are all the same size. Move in groups One following another

Factors determining the size of waves Speed of the wind blowing Length of time that the wind blows The fetch or Length of open water, across which the wind blows.

Fetch Is the distance that the wind can blow across open water.

Whitecaps Crest of a wave that is blown off by high winds. Pg. 435

FACT Height of a wave changes as the wave approaches the shore. Water involved in the up and down motion of a wave extents to a depth of one-half wavelength. Top of the wave continues to move at its original speed.

Breaker A foamy mass of water that washes onto shore. Height of the wave is one to two times the height of the original wave.

Factors that determines the size & force of breakers By the original wave height, wavelength, & the steepness of the ocean floor close to the shore.

Refraction Bending of a wave. Occurs when the part of the wave nearest the shore strikes the shallow bottom and slows down.

Undertow When water carries onto a beach by breaking waves is pulled back into deeper water by an irregular current. Seldom very strong and only along shorelines with steep drop-offs do they create problems.

Rip current Dangerous undertow Swift rip currents form when water from large breakers returns to the ocean through channels in underwater sandbars. Flow perpendicular to shore May be strong enough to carry a swimmer. Could close beaches.

Longshore current These waves are the result of waves that approach the beach at angles. Forms a sandbar

Tsunamis Caused by underwater earthquakes. Most destructive waves in the ocean. Often called tidal waves.

Waves that slow Waves slow down in shallow water because the bottom of the wave touches the ocean floor and is slowed by friction.

22.3 Tides The daily changes in the level of the ocean surface. Sir Issac Newton identified the force that causes the rise and fill of tides along coastlines. Gravitational pull of the moon on the earth and the water. Pull is the strongest on the side of the earth nearest the moon. Ocean bulges on that side.

Other facts Bulging ocean forms a high tide inside the bulge. Low tides are formed halfway between the two high tides.

Tides Tidal bulges move westward. Two tidal budges in most places causes two high tides and tow low tides daily.

Tidal Range The difference between the levels of the high and low tides at a specific location. It can vary widely from place to place. Cycles of high and low tides occur 50 min later each day because the moon rises about 50 minutes each day. Suns gravitational pull also has an effect on the tidal range.

Spring tides Combined gravitational pull of the sun, and the moon are all aligned. Results in higher high tides and lower low tides. Daily range is larger at these times. Occurs twice a month.

Neap tides When the sun and moon are at right angles during the first and third quarter, the gravitational forces do not act together, instead against each other. Daily tidal range is small. Occur twice a month.

Tidal oscillations Slow, rocking motions of ocean water that occur as the tidal bulges move around the ocean basins.

Tidal current As water rises and falls with the tides, it flows toward and away from the coast. Tidal current flowing toward the coast is called the flood tide. Tidal current flowing toward the ocean is called the ebb tide. Slack water is the time period between flood tide and ebb tide with no tidal currents.

Tidal bore The surge of water that rushes upstream. It enters the ocean through a long bay. Can rise as high as 5 m.

Factors influencing tidal patterns in a location: Size, shape, depth, and location of the basin in which the tide occurs.