Lecture 13 - Geostrophic Balance Flashcards
(10 cards)
What is geostrophic balance?
It is the balance between the horizontal pressure gradient force (PGF) and the Coriolis force, responsible for large-scale ocean currents.
In geostrophic balance, how do currents flow relative to the pressure gradient?
Currents flow parallel to isobars (i.e., at 90° to the PGF)—to the right in the Northern Hemisphere, to the left in the Southern Hemisphere.
What two forces are in balance in a geostrophic current?
The Pressure Gradient Force and the Coriolis Force.
What determines the strength of a geostrophic current?
The steepness of the pressure gradient; a steeper gradient results in a faster current.
What does a pressure gradient result from in the ocean?
Variations in sea surface height (SSH)—higher SSH = higher pressure.
What direction does the Coriolis force act in each hemisphere?
To the right of motion in the Northern Hemisphere, and to the left in the Southern Hemisphere.
What equation can be used to calculate geostrophic velocity using pressure?
v= 1/ρf * dP/dx
u= − 1/ρf * dP/dy
What equation can be used to calculate geostrophic velocity using sea surface height (SSH)?
v = g/f * dn/dx
u = -g/f dn/dy
𝜂 =sea surface height
g = gravitational acceleration
f = Coriolis parameter
What is measured by satellite altimetry to infer ocean currents?
The sea surface height (η) relative to the geoid.
Why are geostrophic currents useful in oceanography?
They help explain and predict large-scale ocean circulation, climate patterns, and transport of materials.
