Ekman and Geostrophic Transport

Steady state

Condition in which forces acting on a water parcel balance so that its net acceleration is zero

Geostrophic balance

Equilibrium state achieved when the horizontal pressure gradient force is exactly balanced by the Coriolis force

Mathematical expression for geostrophic balance relating pressure gradient force $P_x$ to Coriolis parameter $f$ and velocity $v$

$$P_x = f v$$

Direction in which the pressure gradient force acts on a sloping sea surface

Downhill (from high sea surface height to low sea surface height)

Direction in which the Coriolis force acts relative to the direction of motion in the Northern Hemisphere

To the right of motion

Steep sea surface slopes

Feature of sea surface slope that corresponds to the fastest geostrophic ocean velocities

Circulation direction of large-scale ocean gyres in the Northern and Southern Hemispheres

Clockwise in the Northern Hemisphere; counterclockwise in the Southern Hemisphere

Net direction of ocean water movement relative to wind direction due to Ekman transport in the Northern Hemisphere

$90^\circ$ to the right of the wind direction

Direction of final Ekman surface flow in the Northern Hemisphere when wind blows directly north

To the southwest

Three major oceanographic processes driven by Ekman transport

Coastal upwelling/downwelling, divergence and convergence zones, and subtropical gyre formation

Type of swift ocean current formed due to a strong cross-current pressure gradient balanced by Coriolis force (e.g., Gulf Stream)

Western boundary current

Pressure gradient force

Oceanic force caused by spatial differences in sea surface height

Wind stress

Force exerted directly by wind on the ocean surface