Ocean Ocean CurrentsCurrents

Ocean CurrentsOcean Currents• Mass movement or flow of Mass movement or flow of

ocean waterocean water

• River within the ocean River within the ocean (“Conveyor Belt”)(“Conveyor Belt”)

• Two types Two types • SurfaceSurface

• Deep (or Subsurface)Deep (or Subsurface)

Ocean Currents Ocean Currents VocabularyVocabularyGyre: Gyre: Nearly closed current system in the Nearly closed current system in the

open oceanopen ocean

• Clockwise Clockwise pattern in N. pattern in N. HemisphereHemisphere• Counter-Counter-clockwise clockwise pattern in S. pattern in S. HemisphereHemisphere

Ocean Currents Ocean Currents Vocabulary Continued…Vocabulary Continued…

• MeanderMeander – Bend – Bend in a current’s flowin a current’s flow• RingRing – Large, – Large, whirl-like pattern whirl-like pattern (when a meander (when a meander is cut off)is cut off)• EddyEddy – Small – Small current Ringcurrent Ring

Surface Current LinkSurface Current Link

• Horizontal, stream-like Horizontal, stream-like movements of water that movements of water that occur at or near the occur at or near the surface of the oceansurface of the ocean

• Can reach depths of Can reach depths of several hundred metersseveral hundred meters

Surface Currents Surface Currents continued…continued…

• Controlled by three factorsControlled by three factors– Global windsGlobal winds– Coriolis EffectCoriolis Effect– Continental DeflectionsContinental Deflections

•Global WindsGlobal Winds– Cause surface currents to flow in Cause surface currents to flow in

the direction the wind is blowingthe direction the wind is blowing

•Coriolis Effect LinkCoriolis Effect Link– Apparent curving of moving Apparent curving of moving

objects (ie- Water) due to the objects (ie- Water) due to the Earth’s rotationEarth’s rotation

Surface Currents Surface Currents continued…continued…

•Coriolis Effect Coriolis Effect – Northern Hemisphere = clockwiseNorthern Hemisphere = clockwise– Southern Hemisphere = counter Southern Hemisphere = counter

clockwiseclockwise

•Continental DeflectionsContinental Deflections– Shape of continents change the Shape of continents change the

direction of current flowdirection of current flow

Surface Currents Surface Currents continued…continued…

Deep CurrentsDeep Currents• Stream like movement of ocean Stream like movement of ocean

water far below the surfacewater far below the surface

• Caused by changes in densityCaused by changes in density– Change in temperatureChange in temperature– Change in salinityChange in salinity

• Change in temperatureChange in temperature– Decreasing the temperature Decreasing the temperature of water increases densityof water increases density

• Change in salinityChange in salinity– Increasing the salinity of Increasing the salinity of water increases densitywater increases density

Deep Currents Deep Currents continued…continued…

Surface currents and Surface currents and climateclimate

• Warm water currentsWarm water currents– On the east coasts of On the east coasts of continentscontinents

– Bring warm water to Bring warm water to colder regionscolder regions

• Cold water currentsCold water currents– On the west coasts of On the west coasts of continentscontinents

– Bring cold water to Bring cold water to warmer regionswarmer regions

Surface currents and Surface currents and climateclimate

Upwelling LinkUpwelling Link

• The movement of deep, cold, The movement of deep, cold, nutrient rich water to the nutrient rich water to the surfacesurface

• Nutrients promote growth of Nutrients promote growth of fish and plantsfish and plants

• Areas are important fishing Areas are important fishing groundsgrounds

Downwelling Downwelling

• The movement of warm The movement of warm surface waters towards the surface waters towards the coastcoast

• Causes a thickening of the Causes a thickening of the surface waters which causes surface waters which causes them to sinkthem to sink

Causes of warm and cold Causes of warm and cold currentscurrents

•El NiEl Niññoo–Change in the water Change in the water temperature in the Pacific temperature in the Pacific Ocean that produces a Ocean that produces a warm currentwarm current

•La NiLa Niñaña–Change in the eastern Change in the eastern Pacific Ocean in which the Pacific Ocean in which the surface water temperature surface water temperature becomes unusually coolbecomes unusually cool

Causes of warm and cold Causes of warm and cold currentscurrents