Detailed characterization of a cold Antarctic eddy

Eddy formation in the Southern Ocean plays a critical role in meridional exchanges of heat and salt. It has also been shown to have a significant impact on primary productivity and on the creation of preferred feeding regions for birds and other predators. This eddy formation is not geographically uniform, but is concentrated in certain specific regions, particularly where the Antarctic Circumpolar Current crosses shallow bathymetry. One such region is at the South‐West Indian Ridge where eddies are formed that subsequently drift past the Prince Edward Islands. We have studied such an eddy in detail. It was at least 1000 m deep, had a radius of 60–90 km, a heat content of 5.40 × 1019 J and rotated at a rate of 1 revolution every 5 days. Altimetric observations show that it was formed at 51°S; 32°E and that its intensity–as expressed as its sea level anomaly–declined by ∼40% of the original value within 144 days. This relatively rapid dissipation suggests that these eddies do not have a lifetime of more than 14 months. During that period they will have carried their anomalous heat and salt content about 1.5 degrees of latitude.