Spatio-temporal distributions of δ18O, δD and salinity in the Arabian Sea: Identifying processes and controls

Reporting δ18O, δD and salinity of 683 new surface water samples from Arabian SeaSlope of δ18O–δD regression much lower (3.2 ± 0.16) than global ocean surface waterContrary to Bay of Bengal, both δ18O and S progressively increase from 0 to 10°N.

Isotopic compositions (δ18O and δD) and salinity (S) of 683 surface water samples from the Arabian Sea (AS) collected during 2008–2010, were measured to understand the factors controlling the spatio-temporal distribution of these parameters. From the distributions of δ18O and salinity (S), and the relationships between δ18O–δD and δ18O–S, the following inferences have been drawn: (1) there is a broad correspondence between the geographic distributions of the δ18O and S; (2) in spite of a large scatter, a statistically significant δ18O–S relationship can be identified in much of the investigated part of the AS; (3) the δ18O–δD regression line for all samples clumped together has a slope of 3.2 (± 0.16), much lower than that (7.37) for the global ocean surface water line (GOSWL), which in the case of the AS is seen only for samples with salinity < 34; (4) the linear relationship between δ18O and δD breaks down completely in the months of March–May; (5) contrary to the adjoining Bay of Bengal (BOB), both δ18O and S progressively increase from the equator northwards; (6) the δ18O–δD and the δ18O–d-excess relationships indicate strong kinetic fractionation due to evaporation from surface waters of the AS throughout the year, with enhancement during summer months.