1. Greta Leber Rosenstiel School of Marine and Atmospheric Science Student Seminar Presentation: December 1, 2010 Advisor: Dr. Lisa Beal

2. Image Courtesy Dr. Lisa Beal

3. Average Vertical Spacing: 2m Average Horizontal Spacing: 23km Lowered Acoustic Doppler Current Profiler (LADCP) with Conductivity- Temperature-Depth (CTD) Line 1: LADCP + CTD During Deployment: Less Synoptic: April 7-15 Steamed back for a continuous underway shipboard ADCP section Line 2: LADCP + CTD More Synoptic: April 17- 19 Image Courtesy Dr. Lisa Beal

4. Images Courtesy Dr. Lisa Beal Agulhas Undercurrent Experiment East London line February-March 2003

5. Solitary Meander Characteristics (de Ruijter et al, 1999): Downstream velocity ranges from 5 (North) to 20 (South) km day-1, Diameter ranges from 30-200 km Period between 50 and 150 days. Marine Remote Sensing Unit; http://www.afro-sea.org.za/mrsu/flags.php

6. April 7 April 12 Line 1 Diameter: ~100km Velocity: ~15 km day -1 downstream SSALTO/ Data Unification and Altimeter Combination System (DUACS) Real-Time AVISO MADT Product

7. Line 1Line 2

8. Line 1Line 2 Northeastward (Undercurrent)68.319.2 Southwestward (Agulhas)128.2129.1 Total (Southwestward)59.9109.8

9. Need a ZVS… commonly:But, we know that the ZVS is V-shaped, so use ZVS from LADCP data: Still no Northeastward (Barotropic Feature)!

10.  SOLUTION: Demean the Geostrophic Velocity and add Geostrophic Barotropic component from LADCP.

11. Line 1Line 2

12.  During the passage of a Solitary Meander, the northward flow strengthens and extends to the surface as a barotropic feature.  Geostrophic velocity is highly sensitive to the choice of a ZVS, with comparison to LADCP barotropic component giving the best results.  Ageostrophic flows in the Agulhas are concentrated in the surface layer.  Next Steps (with the hydrographic data): Investigate structure of ageostrophic flow (Cylostrophic? Ekman? Data artifact?). Continue evaluating meander properties (vorticity, mixing, etc.).

13.  My advisor, Dr. Lisa Beal.  The crew of the R.V. Knorr  Funded by NSF

14. Images Courtesy Dr. Lisa Beal

15.  Largest WBC in the world (Bryden and Beal, 2005)  Large heat and salt transports.  Important inter-ocean link in the Thermohaline Circulation as the so- called ‘warm-water route’ first described by Gordon, 1986.  Upstream dynamics have been linked to frequency of ring-shedding events (Lutjeharms and van Ballegooyen, 1988; van Leeuwen et al, 2000). Zahn, 2009

16. SSALTO/ Data Unification and Altimeter Combination System (DUACS) Real-Time AVISO MADT Product