MODAS and the mesoscale field

Animated visual comparison of float trajectories with the evolution of the MODAS-SSH field reveals a strong agreement between the location and propagation of mesoscale features as depicted by floats and SSH.

KAPEX RAFOS float trajectories over MODAS steric height anomaly. Trajectory segments span 7 days centred on August-27 1998. A trajectory segment of "1 degree length" corresponds to a velocity of 18 cm s-1. Thick solid lines represents isobaths at 0, 500, 1000, and 3000m depth. Steric height anomaly contours (thin black lines) are at 1, 1.5, and 2 m, located over cyan, yellow and red background colour respectively.

A movie can be downloaded by anonymous ftp (39 Mbytes!) from
ftp://po.gso.uri.edu/pub/downloads/oboebel/agulhas_movie.zip

Strong positive (red) and negative (blue) SSH anomalies coincide with anticy clonic and cyclonic float trajectory segments, respectively.

An anticyclonic Agulhas Ring is observed near 36° S, 14° E, which is separated from the Agulhas Retroflection (38° S, 20° E) by an cyclonic eddy (37° S, 16° E)

A meander in the Agulhas Current trapped a cyclonic eddy (37° S, 22° E) along the continental shelf break.

The strong association of floats with the SSH signal indicates that the trapping depth of mesoscale features extend to at least 27.2 sigma-theta isopycnal (between 800 and 1200m depth) in this area.