Application of precipitation isotopes in pursuit of paleomonsoon reconstruction: An Indian perspective

The isotopic analysis of carbonates is widely used to get information on past monsoon variability. A systematic study addressing a fundamental issue, how do the oxygen isotopes respond to large-scale processes, is still lacking. We have generated precipitation isotopic records from the Andaman Islands, Bay of Bengal, to investigate how the precipitation isotopes respond to monsoon rainfall over a varying spatial domain that ranges from a local scale to a continental scale. Analysis of moisture transport parameters reveals that the precipitation isotopes are more sensitive to the moisture fluxes than the rainfall amount. The relation between precipitation isotopes and moisture dynamics remains robust, encompassing a large portion of the Bay of Bengal, but weakens beyond its geographical domain. The amount effect was observed to be decreasing with an increasing spatial domain. The study predicts that point scale observation, such as speleothem isotopic records, though respond to large-scale processes, rainfall quantification, however, for a vast region may be underestimated.