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

Isotopic compositions (delta O-18 and delta D) 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 delta O-18 and salinity (S), and the relationships between delta O-18-delta D and delta O-18-S, the following inferences have been drawn: (1) there is a broad correspondence between the geographic distributions of the delta O-18 and S; (2) in spite of a large scatter, a statistically significant delta O-18-S relationship can be identified in much of the investigated part of the AS; (3) the delta O-18-delta D 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 delta O-18 and delta D breaks down completely in the months of March-May; (5) contrary to the adjoining Bay of Bengal (BOB), both delta O-18 and S progressively increase from the equator northwards; (6) the delta O-18-delta D and the delta O-18-d-excess relationships indicate strong kinetic fractionation due to evaporation from surface waters of the AS throughout the year, with enhancement during summer months. (C) 2013 Elsevier B.V. All rights reserved.