Rapid changes in the characteristics of the deep salinity maximum of the south-east Indian Ocean

Abstract

Salinities of the deep salinity maximum at SCOR-UNESCO reference stations 1 and 2 in the south-east Indian Ocean have varied much more (� 0.01-0,02%o, about the mean) than those at a CSIRO reference station in the south-west Pacific Ocean (� 0,004%o about the mean) during 1959-63. At the SCOR-UNESCO reference stations, and other stations between, the changes in salinity of this maximum during 1959-63 were paralleled by changes in other properties, consistent with an annual increase in the advection of a north Indian Ocean deep water mass during March-July. Changes in the properties of the deep water at the CSIRO Reference Station during 1962-63 were within the precision limits of the Australian analytical methods found during the intercalibration tests on R.S. Vityaz in August 1962. Seasonal changes of the same, or greater magnitude than those at SCOR-UNESCO reference stations 1 and 2 can be expected at other sites chosen for SCOR-UNESCO reference stations in the Indian Ocean, whenever they fall within the boundaries of the north Indian Ocean deep water mass. Such stations will be unsuitable, therefore, for comparing analytical accuracies but could be very useful for monitoring changes in the deep circulation.