Mrs. Mannel Earth Science

Surface Currents  Surface currents move water at or near the surface in stream like movement  They can be several thousand km in length and travel across entire oceans  The Gulf Stream current transports 25 times more water than all the rivers in the world

Factors Controlling Surface Currents  Global winds  The Coriolis effect  Continental deflection

Global Winds  Winds blowing across the earth’s surface create surface winds  Different winds cause currents to flow in different directions  At the equator, winds blow ocean water E to W  At the poles, winds blow ocean water W to E

The Coriolis Effect  The Earth’s rotation causes winds and surface currents to move in a curved path rather than a straight line  Currents in the NH flow clockwise and in the SH counterclockwise

Continental Deflection  Since continents rise above sea level, they cause winds, and therefore currents to become deflected...or change directions

Ocean Temperatures

Deep Currents  Deep currents are stream like movements of ocean water far below the surface  Deep currents are controlled by water densities  Density in ocean water is determined by temperatures and salinity Decreasing the temp and increasing the salinity will increase the density!

Deep Currents  Colder, more dense water will always sink below warmer, less dense water  As these deep currents flow along the ocean floor towards the equator, they begin to warm and rise  As the warmer surface currents flow towards the poles, they cool and sink!  Page 369

Surface Currents and Climate  Surface currents can warm, or cool the local climates of coastal areas

El Nino   El Nino is a cycle of warmer waters in the eastern Pacific Ocean that can occur ever 2 to 12 years.  It is caused by the trade winds moving less warm water to the western Pacific  The effects of El Nino include flooding and mudslides due to an increase in precipitation while some regions experience droughts