Ocean circulation over the Saya de Malha Bank in the South West Indian Ocean

Abstract

The Saya de Malha Bank is one of the major banks of the Mascarene Plateau in the South West Indian Ocean. It is known for its unique ecosystem, remoteness (nearest island is about 300 km away) and complex oceanographic conditions. This study presents the results of a survey conducted in May 2018 on-board the R/V Dr Fridtjof Nansen, and aims to provide a descriptive overview of the interaction of the large-scale South Equatorial Current (SEC) over the shallow Saya de Malha Bank. The analysis of the current pattern revealed a two-layered structure of the current over the shallow topography of the bank compared to the vertically rigid-structure of the SEC throughflow in its deeper region. This two-layered flow consists of a surface layer and a sub-thermocline layer. The top layer flow, carrying the lower salinity mass (Tropical Surface Water) is driven by the Ekman dynamics observed in the southern hemisphere whereas the sub-thermocline current layer is most likely governed by the tidal and internal wave dynamics generated by the topographic relief of the bank.