Oceanography Physical Dynamics of the Oceans Ocean Currents

Oceanography Physical Dynamics of the Oceans

Ocean Currents • Currents are the circulation of water throughout the oceans. • There are two main types of ocean circulation: wind-driven currents and thermohaline circulation.

Wind-Driven Currents • Wind-driven currents move the upper parts of the ocean horizontally by wind action that strikes the ocean surface. • The two major wind driven currents near North America are the gulf stream and the California current.

The Gulf Stream • The gulf stream is a major wind- driven current that moves warm water from the Caribbean Sea up along the east coast of the United States, where it eventually reaches Greenland.

California Current • The California current is a wind-driven current which moves colder arctic waters southward. It brings cold water down the western coast of North America.

Upwelling • Upwelling is another important aspect of wind-driven currents that occurs when winds move warm surface waters away from the equator or the coasts of continents and allows nutrient-rich colder water to replace the warm nutrientdepleted water.

Deep Ocean Circulation • Deep ocean circulation is called thermohaline circulation. “Thermo” means heat and “haline” means salt. • This type of ocean circulation is driven by temperature and salinity differences in the water. • It allows for nutrients and heat to circulate throughout the world’s oceans.

Tides • Tides are the cycling rising and falling of the Earth’s ocean surface caused by tidal forces of the Moon and the Sun acting on the Earth. • Tides cause changes in the depth of the sea and also produce oscillating currents known as tidal streams.

High Tide Low Tide

Ocean Surface Waves • Surface waves occur in the upper layer of the ocean. • They usually result from wind or geologic effects and can travel thousands of miles before striking land. • They range in size from small ripples to huge tsunamis.

Factors That Influence Formation of Wind Waves • Wind speed. • Distance of open water that the wind has blown over. • Length of time the wind has blown over a given area. • The greater each of these variables, the larger the wave.

How Waves Are Measured • Height (From trough to crest. ) • Wavelength (From crest to crest. ) • Period (Time interval between arrival of consecutive crests at a stationary point. )

Breaking Waves • A breaking wave is a wave whose base can no longer support its top, causing it to collapse. • A wave will break when it enters shallow water or when two wave systems oppose and combine forces. • These are the waves that are surfed.