Arterial ocean circulation of the southeast Indian Ocean

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Abstract

[1] The time mean ocean circulation for the southeast Indian Ocean (SEIO) is analyzed using a colorwheel to reveal an “arterial-like” structure. Although quasi-zonal, the mean circulation in this region is distinctly more complex than previously presented in recent literature. The mean flow is derived from an eddy-resolving ocean reanalysis of the past 14 years. The ocean state is constrained through data assimilation with observed sea level anomaly, sea surface temperature and in-situ profiles. Geostrophic currents derived from the reanalyzed mean dynamic topography (MDT) are validated against two other MDT analyses to show a comparable arterial structure and distribution of scales. In particular, the broad scale eastward flow is regularly interspersed by narrow bands of the near westward flow. Meridional sections from the ocean reanalysis reveal a net eastward transport in the surface layer and a net westward flow at mid-depth. The seasonality of the surface layer flow in the SEIO appears to have increased (decreased) eastward mean transport that coincide with seasons of stronger (weaker) Leeuwin Current (LC). Whether the narrow bands of mean current and mass flux are simply the average of the eddies or represent an underlying weak jet remains a topic of current debate.

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