Journal of Marine Science: Research & Development
Open Access

Abstract

The Lakshadweep Archipelago consist a group of Islands in the Arabian Sea lies nearly parallel to the south western Indian coast. During the months of May-Jun the moisture laden air mass flows through this region and then hits the Kerala coast to initiate the monsoon season in India. Isotopic analysis of precipitation has been shown to be a useful tool to study the hydrological and atmospheric processes, but to our knowledge no such work has been done on Lakshadweep rain water. Since the rainfall in this island is expected to be almost free from continentally generated moisture, their isotopic study is likely to provide information of moisture source that is purely driven by the oceanic processes. With this perspective isotopic analysis of rainwater at Minicoy Island has been carried out on daily scale for the year 2015, starting from June to December. The δ18O varied from 0 to -5‰ during the monsoon season (JJAS), thereafter it showed significant depletion, ranging from -3 to -14‰. The post monsoon period depleted d18O values indicated a different moisture source, presumably from the Bay of Bengal, also supported by the back trajectory analysis. The local meteoric water line has been established as dD =7.34 δ18O + 8.70, (R2=0.98; n=63; p < 0.0001). The slope being less than that of the global meteoric water line implying significant amount of rain drop evaporation, which is also supported by a strong inverse correlation between the δ18O and d-excess of the Minicoy rain water. The δ18O showed strong inverse correlation with the 1ox1o TRMM derived rainfall data (R2= 0.28, n=63, p <0.001). The result is likely to be useful in understanding the complex behavior of the rain water isotopic variability observed in the Western Ghat mountain range of the south west coast of India.

Biography

Email: supriyo@tropmet.res.in