Interannual variability of the South Indian Countercurrent
journal contributionposted on 2023-05-18, 19:34 authored by Menezes, VV, Helen PhillipsHelen Phillips, Vianna, ML, Nathaniel BindoffNathaniel Bindoff
In the present work, we investigate the interannual variability of the South Indian Countercurrent (SICC), a major and still understudied current of the Indian Ocean circulation. To characterize the interannual variability of the SICC, four different datasets (altimetry, GLORYS, OFAM3 and SODA) are analysed using multiple tools, which include Singular Spectrum Analysis and wavelet methods. The quasibiennial band dominates the SICC low frequency variance, with the main peak in the 1.51.8 yr interval. A secondary peak (2.12.5 yr) is only found in the western basin. Interannual and decadal-type modulations of the quasi-biennial signal are also identified. In addition, limitations of SODA before the 1960’s in the SICC region are revealed. Within the quasi-biennial band the SICC system presents two main patterns with a multiple jet structure. One pattern is characterized by a robust northern jet, while in the other the central jet is well developed and northern jet is weaker. In both patterns, the southern jet has always a strong signature. When the northern SICC jet is stronger, the northern cell of the subtropical gyre has a triangular shape, with its southern limb having a strong equatorward slant. The quasi-biennial variability of the SICC is probably related to the Indian Ocean tropical climate modes that are known to have a strong biennial characteristic.
Australian Research Council
Publication titleJournal of Geophysical Research: Oceans
Department/SchoolInstitute for Marine and Antarctic Studies
PublisherWiley-Blackwell Publishing, Inc.
Place of publicationUnited States
Rights statementCopyright 2016 American Geophysical Union