chapt 7 -OcCirculation.doc - OCE2001 Exam 2 Notes 1 Chapter...

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OCE2001 Exam 2 Notes 1 Chapter 7 - Ocean Circulation Ocean currents - large-scale water movements occurring everywhere in the ocean - on both the surface and far below. Surface ocean currents o Driven by winds (which are ultimately fueled by solar heating) o Winds and surface ocean currents are intimately related. Transfer heat from warmer to cooler areas Similar to pattern of major wind belts Primarily horizontal motion Affect coastal climates Deep ocean currents o Driven by differences in density due to differences in temperature and salinity Vertical and horizontal motions Provide oxygen to deep sea Affect supply of nutrients and type of marine life Measuring surface currents Direct methods o Floating device tracked through time with GPS o Fixed current meter – measures speed of flow Indirect methods o Pressure gradients o Radar altimeters – satellite computer animations o Doppler flow meter – similar to those used in weather prediction Incidental float “meters” - Floating objects can act as drift meters o Drift seeds - “sea beans” o Bottle messages (MIB) o Objects accidentally lost from cargo containers off freighters (Worldwide, about a thousand containers are lost overboard each year) o Can travel thousands of miles Measuring deep currents Floating devices tracked through time Properties of seawater - used to map movements of deep waters (salinities, temps, etc.) Naturally occurring chemical tracers Manmade Chemical tracers – added to seawater by human activity o Tritium from nuclear bomb testing – measure decay of hydrogen isotope to helium. Origin of surface currents Frictional drag between wind and ocean Other factors affect speed and direction o Distribution of continents o Gravity o Friction against high underwater features
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OCE2001 Exam 2 Notes 2 o Coriolis effect causes deflection Types of Currents Ocean gyres - large circular loops of water moving in a swirling vortex. o Circular motion due to Coriolis effect – water is deflected. o Organisms use gyres for movement o General Information on gyres 5 Subtropical gyres - centered about 30 o N or S o Western intensification - Current stronger on western edge Major components in both the Northern and Southern Hemisphere o Equatorial currents flow west o Western Boundary currents flow away from equator o Northern or Southern Boundary currents flow east or west o Eastern Boundary currents flow toward the equator o Subpolar gyres flow eastward o Equatorial countercurrents - flow east (counter to equatorial currents) Other factors affecting surface currents Ekman Spiral - change in current direction and speed with increasing depth forms a spiral when viewed from above. Describes speed and direction of seawater flow at different depths Results from o A steady wind blowing across an ocean o The force of the water moving above of each water layer o Due to the Coriolis effect
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  • Spring '14
  • Pacific Ocean, Gulf Stream, OCEAN CURRENTS, North Atlantic subtropical gyre

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