Place these notes in your Notebook. Chapter 24 Test Review Place these notes in your Notebook.

Surface currents in the ocean are primarily driven by winds. Surface currents flowing away from the equator carry warm water. The winds that are most involved in forming ocean currents worldwide are the trade winds and westerlies. In some regions there is a seasonal reversal in the direction of surface ocean currents due to a reversal in seasonal wind direction.

Two examples of warm ocean currents are the Gulf Stream and the Kuroshio Current. The British Isles and Iceland both have warmer climates than they would otherwise because the North Atlantic Drift carries warm water across the Atlantic. The Sargasso Sea would be associated with warm-core rings on the continental side of the Gulf Stream. Countercurrents flow in the opposite direction of wind-related currents.

Deep ocean currents are driven by differences in density. The circulation of ocean water is an efficient way to transport heat. Changes in density that lead to the formation of deep ocean density currents include evaporation, cooling, and freezing. Turbidity current density results from water mixing with sediment particles.

When seawater freezes, most of the salt is left behind, increasing the density of the remaining seawater. The cause of the density current that flows over the Strait of Gibraltar into the Atlantic Ocean is evaporation. Upwelling is important to sea life because it brings nutrients to the surface water. Upwelling occurs along the western edges of continents, where surface water flows away from land.

COULOIR CLIFFS, GRANITE HARBOR Antarctica

Major commercial fishing areas are usually located in areas of persistent upwelling. The gravitational pulls of the moon and sun cause Earth’s tides. The sun’s effect is about half that of the moon’s. Tides are highest when Earth is in line with both the sun and moon. The difference between high tide and low tide is most noticeable in long, narrow bays.

Waves and Tides

Ocean Currents

The diagram shows the generalized pattern of subsurface currents in the Atlantic Ocean. Circle the region(s) at the surface where high levels of nutrients allow phytoplankton to thrive. Shade the current that carries the densest water. (4 points)

The diagram shows the generalized pattern of subsurface currents in the Atlantic Ocean. Circle the region(s) at the surface where high levels of nutrients allow phytoplankton to thrive. Shade the current that carries the densest water. (4 points)

Essay: Compare the general temperature and direction of flow of the current that flows off the east coast of the United States with the temperature and direction of flow of the current that flows off the west coast of the United states. Off the east coast of the US the Gulf Stream flows northward, carrying warm water pole ward from near the equator. Off the west coast the California Current flows southward, carrying cold water from high latitudes toward the equator.

Essay #2 Compare the cause and amount of flow of a turbidity current with that of the flow of Antarctic Bottom Water. A turbidity current is a density current that forms when water mixes with sediment, increasing its density so that it flows down slope in response to gravity. It is local. Turbidity currents are common on continental slopes. Antarctic Bottom Water forms off the coast of Antarctica. As cold surface water in this region freezes, salt is left behind, increasing the density of the remaining water. This water is voluminous and sinks forming a dense current that spreads throughout most of the world’s ocean basins.