Ocean Currents Chapter 5 Notes

Ocean Currents Movement of ocean water that follows a regular pattern

First Explorer 1940 Thor Heyerdahl theorized that humans migrated across oceans using currents 1947 he left Peru in a sail boat sailed for 97 days until he reached the island of Polynesia.

Surface Currents Horizontal movement caused by winds near the oceans surface Two examples: Gulf Stream and Brazil Current Three Factors: global winds, Coriolis effect, continental deflections

Global Winds Winds cause the currents to flow in different directions Equator= east to west Poles = west to east

Coriolis Effect Curving of moving objects from a straight path due to Earth’s rotation Northern hemisphere- clockwise Southern hemisphere-counterclockwise

Continental Deflections Currents change directions by hitting the continents or landmasses

Deep Currents A stream like movement of ocean water far below the surface Form where water density increases Decreasing water temperature and increasing water salinity increase density. Examples: North Atlantic Deep Water and Antarctic Bottom Water

Deep Currents can form by Decreasing temperature Increasing salinity through freezing Increasing salinity through evaporation

Currents and Climates Surface currents gently cool or warm the coastal areas year round Some surface currents change their circulation pattern causing changes in the atmosphere that affect the climate in many parts of the world.

Warm Water Currents and Climates Warm water currents create warmer climates in coastal areas.

Cold Water Currents and Climates Cold water current bring cooler climates into areas.

Upwelling An upwelling is the movement of deep, cold, and nutrient rich water to the surface of the ocean This is important for organisms. Allows for the plankton and zooplankton to feed fish and other organisms.

El Nino El Nino: a change in the water temperature in the Pacific Ocean that produces a warm current Occurs ever 2-12 years Can last a year or longer La Nina : A change in the eastern Pacific Ocean in which the surface water temperature becomes usually cool Usually follows El Nino

Effects of El Nino Flash floods Mudslides in the United States and Peru Droughts in Indonesia and Australia Lack of upwelling off the coast of South America

El Nino

Wave Parts of a Wave Picture of a wave Trough: lowest point on a wave Crest: highest point on a wave Wavelength: distance between two crests Wave height: the vertical distance between the crest and the trough

Types of Waves Wind forms MOST ocean waves Waves can move in one direction and can generate many different events that can be dangerous to humans.

Deep water waves and Shallow water waves Deep water waves are waves that move in water deeper than one-half their wavelength. As these waves turn into shallow water waves the waves start to interact with the ocean floor. This interaction allows the wave to increase in height. Eventually gravity will pull the crests downward at the “Breaker zone”. Waves continue to “break” until they reach the surf or beach.

Shore Currents Undertow: when waves crash on the beach head on, the water flows back to the ocean underneath new incoming waves

Long shore Currents Waves that hit the shore at an angle cause the water to move along the shore in a current that is near and parallel to the shoreline Down side: spreads trash and erodes the sand.

Open Ocean Waves Whitecaps: Bubbles in the crests of breaking waves Form during storms Very short lived

Open Ocean Waves Swells: Rolling waves that move steadily across the ocean Have longer wavelengths Travel for thousands of kilometers

Tsunamis Waves that form when a large volume of ocean water is suddenly moved up or down Causes: Underwater Earthquakes, Volcanic Eruptions, landslides, underwater explosions,

Tsunamis

Storm Surges A local rise in sea level near the shore that is caused by strong winds from a storm Contain a lot of energy Follow a hurricane Can be 8 m in height