East Australian Current (the EAC)

Where is it?

EAC Properties• Warm, deep, fast, nutrient

poor water• 100 km wide by 500km deep• 30 million m3/s transport! • Well known for eddy

formation (can be 200km across!)

Physical Description• Balance of Ekman wind-stress and coastal

friction (balance of wind curl and frictional vorticity)

• In S.H. : curl + or counterclockwise and friction vorticity – or clockwise

• Stommel- Coriolis term varies with latitude, strengthens W. Boundary EAC

• Surface EAC also strengthened (some) by deep->shallow shelf

Wind field response drives separation (not New Zealand or bottom topography

Eddies• Geostrophic balance: pressure balances coriolis• Cyclonic clockwise around low-pressure cells and counterclockwise (anticyclonic around high pressure cells) IN S.Hemis!

UpwellingW. coast of Aus doesn’t have wind-

driven upwellingInstead EAC “encroachment”

towards coast pushes up isopycnals

References

M. Roughan, J.H. Middleton / Continental Shelf Research 22 (2002) 2551–2572K.R. Ridgway, J.R. Dunn / Progress in Oceanography 56 (2003) 189-222http://www.cmar.csiro.au/remotesensing/oceancurrents/http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=15366