Abstract:
Isotopic compositions (δ18Oand δD) and salinity (S) of 683 surfacewater 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 b34; (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.
