Stable isotopic variations in foraminiferal test from Arabian Sea and its relation to the annual south-west monsoonal rainfall over the Indian subcontinent

Abstract

Examination of delta 18O estimations from the planktonic foraminifera, Globigerinoides ruber, collected at fortnightly intervals using deep sea sediment traps moored at depths of 1000 and 2787 m in the Eastern Arabian Sea (15 degrees 28'N and 68 degrees 45'E) shows very little variation during May to October 1987 - the period of intense southwest monsoon activity over the north Indian Ocean and the adjoining land mass. This implies that the sea surface temperature in this part of the Arabian Sea did not change significantly during the study period. As the monsoonal rainfall of 1987 over the subcontinent was anomalously weak in nature, the above observational finding of low swing in delta 18O values underlines the use of seasonal variability in the planktonic foraminifera as a proxy for the monsoon performance