Articles | Volume 11, issue 3
Ocean Sci., 11, 361–371, 2015
https://doi.org/10.5194/os-11-361-2015
Ocean Sci., 11, 361–371, 2015
https://doi.org/10.5194/os-11-361-2015

Research article 12 May 2015

Research article | 12 May 2015

Eddy characteristics in the South Indian Ocean as inferred from surface drifters

S. Zheng1, Y. Du*,1, J. Li2, and X. Cheng1 S. Zheng et al.
  • 1State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
  • 2Naval Institute of Hydrographic Surveying and Charting, Tianjin 300061, China
  • *now at: State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China

Abstract. Using a geometric eddy identification method, cyclonic and anticyclonic eddies from submesoscale to mesoscale in the South Indian Ocean (SIO) have been statistically investigated based on 2082 surface drifters from 1979 to 2013. A total of 19 252 eddies are identified, 60% of them anticyclonic eddies. For the submesoscale eddies (radius r<10 km), the ratio of cyclonic eddies (3183) to anticyclonic eddies (7182) is 1 to 2. In contrast, the number of anticyclonic and cyclonic eddies with radius r≥10 km is almost equal. Mesoscale and submesoscale eddies show different spatial distributions. Eddies with radius r≥100 km mainly appear in the Leeuwin Current, a band along 25° S, Mozambique Channel, and Agulhas Current, areas characterized by large eddy kinetic energy. The submesoscale anticyclonic eddies are densely distributed in the subtropical basin in the central SIO. The number of mesoscale eddies shows statistically significant seasonal variability, reaching a maximum in October and minimum in February.

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Short summary
Eddies in the South Indian Ocean (SIO) were statistically investigated based on 2082 surface drifters, and 19252 eddies were identified with 60% anticyclonic eddies. Mesoscale and submesoscale eddies show different spatial distributions. Large eddies mainly appear in regions with large eddy kinetic energy. The submesoscale anticyclonic eddies are densely distributed in the subtropical basin in the central SIO. The number of mesoscale eddies shows statistically significant seasonal variability.