Chapter 13 Ocean Motion

What is a wave? The movement of energy through a body of water. The movement of energy through a body of water. Most waves form when wind blows across the surface of the ocean water and energy is transferred from air to water. Most waves form when wind blows across the surface of the ocean water and energy is transferred from air to water.

Wave Size The size of the wave depends: The size of the wave depends: 1. strength of the wind 1. strength of the wind 2. length of time wind blows 2. length of time wind blows 3. distance the wave travels. 3. distance the wave travels. Wave Energy: as a wave moves across the water, the water does not move positions. Wave Energy: as a wave moves across the water, the water does not move positions.

Wave motion Waves move in a circular pattern. They spring forward, then down, then up to original position. Waves move in a circular pattern. They spring forward, then down, then up to original position. Wave depth: most waves are not very deep in the ocean. If you were in a sub, you would never feel the size of waves. Wave depth: most waves are not very deep in the ocean. If you were in a sub, you would never feel the size of waves.

Wave characteristics Highest point: crest Highest point: crest Lowest point: trough Lowest point: trough Wavelength: Distance between 2 crests or 2 troughs Wavelength: Distance between 2 crests or 2 troughs Frequency: the number of waves that pass a certain point in a certain amount of time Frequency: the number of waves that pass a certain point in a certain amount of time Wave height: distance between crest and trough. Wave height: distance between crest and trough.

Diagram of a Wave

How waves change at shore! White capped waves that crash in to shore are called breakers. They form when the bottom of the wave begins to drag in shallow water. The top of the wave continues on… and the wave’s circular motion fall apart or breaks! White capped waves that crash in to shore are called breakers. They form when the bottom of the wave begins to drag in shallow water. The top of the wave continues on… and the wave’s circular motion fall apart or breaks!

A day at the Beach

Tsunamis Type of wave caused by earthquake energy. Type of wave caused by earthquake energy. Most common in Pacific Ocean around Alaska, Hawaii, Japan, Southeast Asia. Most common in Pacific Ocean around Alaska, Hawaii, Japan, Southeast Asia.

How waves affect the shore Longshore drift: as waves come into shore, water washes up the beach at an angle, carrying sand grains. The water and the sand then run straight back down the beach which make sandbars. Longshore drift: as waves come into shore, water washes up the beach at an angle, carrying sand grains. The water and the sand then run straight back down the beach which make sandbars.

Rip currents As a sandbar grows, it can trap water as it flows from shore. As is goes back to the ocean it forms a rip current which is a rush of water that flows rapidly back to sea through a narrow opening. These are very dangerous to swimmers. As a sandbar grows, it can trap water as it flows from shore. As is goes back to the ocean it forms a rip current which is a rush of water that flows rapidly back to sea through a narrow opening. These are very dangerous to swimmers.

Rip Currents

Waves and Beach Erosion Beaches never remain the same because sand is constantly being eroded in some places and built up in others. Beaches never remain the same because sand is constantly being eroded in some places and built up in others. Sand is formed over thousands of years of waves hitting rocks and cliffs. Sand is formed over thousands of years of waves hitting rocks and cliffs.

Barrier Beaches A natural landform that protects shorelines from beach wave action. A natural landform that protects shorelines from beach wave action. These beaches are separated by the mainland by a lagoon. These beaches are separated by the mainland by a lagoon. Ex: Cape Cod, Georgia and Carolina coasts, Miami Ex: Cape Cod, Georgia and Carolina coasts, Miami

Sand Dunes Hills of windblown sand that make beaches more stable and protect the shore from erosion. Hills of windblown sand that make beaches more stable and protect the shore from erosion. Groins: a wall that is built by people of rocks or concrete to try to protect beaches and homes from erosion. Groins: a wall that is built by people of rocks or concrete to try to protect beaches and homes from erosion.

13.3 Ocean Water Chemistry Earth’s surface is 70% oceans. Earth’s surface is 70% oceans. The oceans are salt water- because salts of sodium chloride, sulfur, magnesium, calcium and potassium are dissolved in the ocean water. The oceans are salt water- because salts of sodium chloride, sulfur, magnesium, calcium and potassium are dissolved in the ocean water. The salts come from dissolved minerals from rocks that were transported to the ocean or from volcanic activity. The salts come from dissolved minerals from rocks that were transported to the ocean or from volcanic activity.

Salinity In seawater the most abundant elements are sodium and chlorine. These two elements form a compound called halite. In seawater the most abundant elements are sodium and chlorine. These two elements form a compound called halite. Halite is the salt used to season food. Halite is the salt used to season food. Salinity is the measure of the amount of salt in seawater. It is measured in grams of salt per kilogram. One kilogram of water usually holds 35g of salts. That is 35 parts per thousand. Salinity is the measure of the amount of salt in seawater. It is measured in grams of salt per kilogram. One kilogram of water usually holds 35g of salts. That is 35 parts per thousand.

Salinity Lows and Highs Salinity is lower near the surface where rain and melting ice add fresh water to the ocean. Salinity is lower near the surface where rain and melting ice add fresh water to the ocean. Salinity is higher in hot dry climates where there is a lot of evaporation and near the poles where much of water is frozen as ice and salt remains in liquid water. This make ocean water dense. Salinity is higher in hot dry climates where there is a lot of evaporation and near the poles where much of water is frozen as ice and salt remains in liquid water. This make ocean water dense.

Temp of Ocean Water Temperatures at the surface of ocean water vary with location and seasons. Warmest near equator and coldest at poles. Temperatures at the surface of ocean water vary with location and seasons. Warmest near equator and coldest at poles. Temperature decreases as you go down in the water Temperature decreases as you go down in the water At 1 km down it is about 4 Deg C At 1 km down it is about 4 Deg C Below that it remains about 3.5 deg C Below that it remains about 3.5 deg C

Pressure of ocean water Pressure increases continuously as you go further down Pressure increases continuously as you go further down A diver can only go down about 40 meters safely A diver can only go down about 40 meters safely After that depth a submersible is needed. After that depth a submersible is needed.

13.4 Ocean Currents

Surface Currents Surface currents move water horizontally-parallel to the Earth’s surface. Surface currents move water horizontally-parallel to the Earth’s surface. Surface currents are powered by the wind. Friction between the wind and water cause the water to move, driving the ocean water in huge circular patterns. Surface currents are powered by the wind. Friction between the wind and water cause the water to move, driving the ocean water in huge circular patterns.

Surface Currents Surface currents move only the upper few hundred meter of water, though some are as deep as 1000m Surface currents carry seeds, plants, and messages in bottles.

Ocean Currents

Famous Surface Currents Antarctic Circumpolar Current- Strongest surface current and the only one that circles the Earth.

The Gulf Stream Sailors back in colonial times used the Gulf Stream to sail from North America to England. It is 100 km wide and allowed sailors to use the wind to get across the ocean quickly.

Sneakers Galore! In 1991 a shipping accident occurred in the middle of the Pacific and a few months later a current called the North Pacific Drift Current and the California Current had washed up 80,000 pairs of shoes on the west coast of the US. In 1991 a shipping accident occurred in the middle of the Pacific and a few months later a current called the North Pacific Drift Current and the California Current had washed up 80,000 pairs of shoes on the west coast of the US.

Factors Influencing Surface Currents 1. Coriolis Effect- 1. Coriolis Effect- deflects currents north of the equator to the right and south of the equator to the left. deflects currents north of the equator to the right and south of the equator to the left. 2. Continents- 2. Continents- land being in the way affects currents and changes their path of travel. land being in the way affects currents and changes their path of travel.

The Reverse Flush

Importance of Surface Currents Surface currents distribute heat from the equator to the other areas on the Earth. Surface currents distribute heat from the equator to the other areas on the Earth. Example-Iceland has a mild climate because the warm water from the Gulf Stream travels right past and warms the air over Iceland. Example-Iceland has a mild climate because the warm water from the Gulf Stream travels right past and warms the air over Iceland. Ireland is further from the equator than Scranton but has a warmer average temperature. Ireland is further from the equator than Scranton but has a warmer average temperature.

Upwelling Upwelling is the circulation in the ocean that brings deep cold water to the ocean surface. Upwelling is the circulation in the ocean that brings deep cold water to the ocean surface. This works when wind blowing offshore or parallel to the coast carries water away from the land. This water is replaced with cold deeper water rising up. This works when wind blowing offshore or parallel to the coast carries water away from the land. This water is replaced with cold deeper water rising up.

Is upwelling bad? No- because when the cold water rises it bring with it high concentrations of nutrients No- because when the cold water rises it bring with it high concentrations of nutrients These nutrients help fish and other organisms and are great fishing locations These nutrients help fish and other organisms and are great fishing locations Cold water actually is fuller with life Cold water actually is fuller with life Tropical water can be too warm to support most life. Tropical water can be too warm to support most life. Examples: Coast of Washington and Oregon, Examples: Coast of Washington and Oregon, San Francisco San Francisco

Density Currents Deep in the ocean water circulates not because of wind but because of density differences. Deep in the ocean water circulates not because of wind but because of density differences.