Ocean Circulation

Global Surface Currents http://www.classzone.com/books/earth_science/terc/content/visuali zations/es2401/es2401page01.cfm?chapter_no=visualization

What causes surface currents? Surface currents are driven by wind Coriolis effect is in place due to Earth’s rotation Surface currents in the Northern Hemisphere move to the right of wind direction Surface currents in the Southern Hemisphere move to the left of wind direction If no rotation, ocean currents would move the same direction as wind At the equator, Coriolis force is zero (neither left or right) Ekman transport (or Ekman spiral) (http://oceanservice.noaa.gov/education/kits/currents/05currents4.html) Movement of water layers below the water surface rotates 45 degrees Depth of movement is determined by total depth of water body (less in lakes than in ocean)

Global Circulation http://serc.carleton.edu/eslabs/climate/5a.html

Simplified Global Circulation Five major ocean gyres

Ekman Spiral

What about tides? Tidal currents are the rise and fall of water caused by gravitational pull from moon on our planet Flood current is the movement of water toward the shore Ebb current is the flow of water away from shore However, water doesn’t actually go anywhere, it is just pulled higher of lower in elevation

Are there other types of currents? Currents can be caused by ocean topography, rain, and runoff from land The majority of sub-surface currents are caused by differences in water densities and have a BIG affect on global temperatures This can include interaction of hot and cold water (thermocline) OR Interaction of saltier water and fresher water (halocline) Usually a combination of both (thermohalocline)

Thermohaline Circulation Great Ocean Conveyor Belt

Gulf Stream and North Atlantic Drift Gulf Stream is one of the strongest currents known. It brings warm air from the Gulf of Mexico, up the coast of the Eastern U.S., to Newfoundland (Canada), then across to Northern Europe Without this current of warm water (and subsequently air temperature), England and other places in Europe would be as cold as Canada AND the Gulf Stream is the reason palm trees grow in Ireland (which is at the same latitude as Labrador in Canada)

NOAA: Motion in the Ocean http://oceanservice.noaa.gov/podcast/apr14/mw123-currents.html

Upwelling

Curt Ebbesmeyer Article: http://oceanmotion.org/html/research/ebbesmeyer.htm

Movement of Objects in Ocean

Collapse of Atlantic Ocean Current Article: http://m.huffpost.com/us/entry/us_587031f3e4b02b5f8588fa35

Bill Nye: Ocean Currents https://www.youtube.com/watch?v=r17rLdL9Nik