Geostrophic currents in the south-eastern Indian Ocean

Abstract

Dynamic topographies and geostrophic currents in the upper 1750 m are presented for several cruises between 1960 and 1963. The mean zonal surface circulation is shown to consist of the south equatorial current, 9-14� S., and a weak easterly current between 14� and 32� C. From 0� to 9�S., and again from 32� to 45�S., the mean dynamic height anomalies are independent of latitude, so that mean geostrophic zonal currents are negligible in these latitudes. Changes in dynamic height of the surface relative to 300 decibars within 2-4 weeks are shown for five "seasonal biological cruises" , along 110� E. The significance of these changes in interpreting the dynamics of the region is discussed. Cyclonic and anticyclonic eddies appear occasionally off Fremantle, but no seasonal pattern was found. Cyclonic eddies south of Java are postulated, mainly during the south-east monsoon. A bathythermograph section across the equator on 95� E. is included; it shows no evidence of the equatorial undercurrent.