Wind-Driven Ocean Currents Flashcards
Whats the pressure like at the equator?
Low pressure due to surface air being drawn down to replace rising air - equatorwards wind
What is the circulation like in a non rotating earth?
A single circulation cell in each hemisphere
clockwise - North
anticlockwise - South
What is the effect of earth rotation on the ocean currents?
Strong modification of large scale water and air motions (the Coriolis effect)
Objects relative to the ground are deflected to the right in the north and left in the south.
What are the global winds like on a rotating earth?
3 circulation cells in each hemisphere
top (pole) = polar cell
middle = ferrel cell
bottom (equator) = hadley cell
What produces large scale surface currents?
Zonal wind fields
What is caused from the deflection by continents?
Gyres
What is Ekman transport?
surface flow deflected relative to wind
surface flow = 45 degrees to wind
net flow = 90 degrees to wind
base of spiral flow = opposite to wind
What is upwelling and downwelling?
due to continuity
nutrient rich water is bought up to the surface
divergence - upwelling
convergence - downwelling
What is langmuir circulation?
persistent winds can induce small scale vertical motions
10-100m scale / minutes - hours
What is geostraphic flow?
Ekman transport causes water to converge in the centre of gyres
What is western intensification?
Western boundary currents are faster and narrower than currents on the eastern side due to an increase in the coriolis effect with latitue and change in east-west wind field.
What are gulf stream eddies?
The gulf stream separates warm water in the gyre from the cold water in the north. The flow often curves but if it becomes too extreme, they pinch off and form closed loops.
