Lecture 20: Southern ocean dynamics Flashcards
(13 cards)
What major current dominates the Southern Ocean?
The Antarctic Circumpolar Current (ACC).
What causes divergence and convergence in the Southern Ocean?
Westerly winds, Ekman transport, and coastal easterlies.
What are isopycnals?
Surfaces of constant potential density.
What is the difference between barotropic and baroclinic structures?
Barotropic: isopycnals parallel to isobars;
Baroclinic: isopycnals sloped relative to isobars.
: What are the key fronts in the ACC?
Subantarctic Front (SAF), Polar Front (PF), and Southern ACC Front (SACCF).
What happens to water at oceanic fronts?
There are sharp changes in temperature, salinity, and density.
What is the direction of water flow in the Southern Hemisphere due to pressure gradients?
Water flows left of the pressure gradient due to the Coriolis effect.
How does bathymetry influence ocean currents?
Bathymetry steers currents by altering the depth and hence potential vorticity.
What is potential vorticity (PV) and what factors affect it?
PV is conserved and depends on planetary vorticity (latitude), depth (H), and relative vorticity (shear).
What are mesoscale eddies?
Intermediate-scale swirling currents that transport heat, salt, and momentum.
What is the effect of cyclonic and anticyclonic eddies on water motion Southern Hemisphere?
Cyclonic: upwelling;
Anticyclonic: downwelling
(in Southern Hemisphere).
How do mesoscale eddies affect the ocean?
They stir water in the top ~2000m, balance wind momentum input, and mix properties between fronts.
How does the ACC facilitate upwelling and downwelling?
Deep water upwells through the ACC, and intermediate water sinks north of the SAF due to isopycnal mixing and wind forcing.
