BACKGROUND
Variability
The Undercurrent appears relatively stable and persistent.
- A velocity time series taken at 1200 m depth and 32 km offshore is not within the Undercurrent proper, but exhibits small reversing currents, suggesting that the interface between the opposing currents fluctuates through this point.
- Thus, the Undercurrent may be narrower or deeper on average than indicated by the LADCP snapshots (Figure 2a).
- A twelve month time series at 2000 m depth and 32 km offshore does capture the Undercurrent (Figure 2b), having a mean northeastward flow as much as 10 cm/sec, despite its distance from the core.
- There are seven reversal events in the AUC flow (Figure 2b), but the northeastward current quickly recovers, with most events lasting just three or four days.
- These events were found to be uncorrelated with reversals in the Agulhas Current above, which are attributed to the meandering of the WBC path.
- There is no suggestion that either current exhibits significant seasonal variability, although the time series duration was too short to resolve this well.
Figure 2. Ocean current vector time series at 32° S,
31.5 km offshore and at (a) 1189 m and (b) 2004 m depth
- Introduction
- Velocity Structure
- Variability
- Water Masses and Potential Vorticity Structure
- Geostrophy and Transport
- Mooring Array
- Cross-stream sections
- Along-stream sections
- Synopticity and variability
- LADCP experiment design
- Interocean exchange Indian Ocean ventilation
- Velocity and PV fields
- Mean Transport and variability
- Characterisation of mixing