The Fate of the East Madagascar Current

Schematic — AVHRR (June 1984)

(from Lutjeharms, Deep Sea Res., 1988)

SeaWiFS 6-day Chl composite

Retroflection ??

Series of 6-day composites 12 days apart

“Retro-fiction”Quartly, G.D., J.J.H. Buck, M.A. Srokosz and A.C. Coward, 2006, Eddies around Madagascar — the retroflection re-considered, J. Mar. Sys. 63 (3-4) 115-129.

OCCAMSea Surf. Ht

Zero of Wind Stress Curl lies further south

No eastward current for it to feed

SIOCC

Siedler, G., et al.(2006), Structure and origin of the subtropical South Indian Ocean Countercurrent, Geophys. Res. Lett., 33, L24609Siedler, G. et al. (2009), Modes of the southern extension of the East Madagascar Current, J. Geophys. Res., 114, C01005

Mean Dynamic Topography

Rio, M.H. et al.(2011), New CNES‐CLS09 global mean dynamic topography computedfrom the combination of GRACE data, altimetry, and in situ measurements, J. Geophys. Res., 116, C07018

Schematic of counter-rotating eddies

Surface drifters

Model representation of "SIOCC"

ADCP section

Ship-mounted ADCP

moorings

+ Sat imagery

CC

SST

Comparison with altimetryVe

locit

y (m

/s)

Jason-1 altimeter

Modes of variation

Summary

South Indian Ocean Counter CurrentIn SIO there is a mean eastward flow at ~25˚S

Connection to EMC:Some waters from EMC turn back to go east

… but does the mean current really exist?

… but is that really a “retroflection”?