Stable isotopic studies of marine carbonates and precipitation A tool to evaluate the surface ocean characteristics minicoy island lakshadweep

Abstract

The present research work explores the potential of aragonite secreting marine organisms to use their stable isotopic signatures as archives to investigate the past sea surface conditions over the Minicoy region Arabian Sea Further since the region receives both the SW and NE monsoon rains stable isotope composition of daily precipitation was also investigated to gain insights on how the ocean atmosphere conditions drives monsoonal changes over this region and to understand the hydrological cycle The stable isotope study will provide a stepping tool to reconstruct the past climate from natural proxies such as corals and molluscs Reef building corals Porites spp offer insights into the past variability of the tropical and sub tropical oceans and atmosphere at annual or seasonal resolution making them a key addition to terrestrial information Stable isotope analysis was performed on the coral sample collected from Minicoy Island to investigate its potential as a proxy for southwest monsoonal variability The X ray picture of the Porites coral revealed 24 annual bands spanning from 1989 to 2013 The mean annual extension over this period is 7 7mm year Stable carbon and oxygen isotope analysis of these bands revealed that the isotopic composition is controlled by kinetic fractionation Further there is a drop of relative to the mean value during 1997 98 indicating anomalous warming of the sea surface Further the results obtained from Minicoy Island have been combined with the published stable isotope records of 18O 13C obtained from Kavarthi Island Lakshadweep The results have been used as a potential proxy to investigate the occurrence of El Nino years coupled with seasonalto decadal variability in sea surface temperature SST The study was useful to trace the isotopic variation in corals and clamshell since the 18O of these proxies are influenced by SST and Sea Surface Salinity SSS As such the SST and SSS in this region vary with dual monsoon systems newline