Forces and Currents

• scalar


  mass, physical quantities that has only one size
• vectors 


  physical quantitative that have direction as well as magnitude
• Newtons First Law of Motion 


  object in a state of rest/uniform motion unless there is a resulting force acting upon it
• if an object is at rest or moving at a constant speed it will have a resultant force of 0
• terminal velocity 


  constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration
• Newtons Third Law of Motion


  for every action there is an opposite or equal reaction
• steady state


  when an object at rest/constant velocity the resultant force is 0
• transient motions 


  non-steady motions
• all ocean currents are a result of forces acting on the fluid ocean
• Newtons Second Law of Motion 


  force=rate of change of momentum
• wind blowing across the ocean surface will transfer momentum across the water surface creating a drag force, pulling the surface water
• Eddies


  the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime
• pressure

  A) P

  B) pVg

  C) A

  D) pgH

  
• density if mass per volume
• magnitude of the Coriolis Force increases from 0 from the equator to the maximum at the poles
• coriolis force acts as right angles of the direction of motion
• coriolis causes a deflection to the right in the northern hemisphere
• coriolis causes a deflection to the left in the southern hemisphere
• geostrophic flow 


  pressure gradient forces is balanced by the corilos effect and moves along lines of equal pressure
• lines of equal pressure are known as isobars
• geostrophic current

  A) geostrophic current

  B) pressure gradient force

  C) coriolis force

  D) high pressure

  E) low pressure

  
• differences in atmospheric pressure helps set up a pressure gradient
• Ekman Spiral


  drag force imposed by wind on the ocean surface pulls the surface water in the direction of the wind
• ekman spiral

  A) wind

  B) surface current

  C) 45

  D) net water transport

  
• friction in the water column moves the surface layer dragging the layer beneath
• ekman depth


  max depth of penetration of an ekman spiral
• Ekman transport 


  net transport of water that is wind driven 90 degrees to the right of the wind
• secondary force


  fluid moving relative to the earth
• wind direction if different from ocean direction
• heating in tropics causing pressure to drop
• poleward flow deflected by coriolis force
• ferrel cell 


  atmospheric layer between polar and hadley cell
• subpolar zones have prevailing easterlies
• mid-latitude zones have prevailing westerlies
• tropics zones have equator-easterly trade winds
• trade winds are deflected to the east
• Ekman transport deflects to the right in the northern hemisphere
• ekman creates a buldge at 30 latitude
• peak of bulge lies west of the ocean center
• bulge produces a strong geostrophic western boundary current and a weaker more spread out