Introduction of Isotopically Light Barium from the Rainbow Hydrothermal System into the Deep Atlantic Ocean

•Negligible Ba removal observed in the Rainbow hydrothermal system.•Insignificant modification of Ba isotope composition of the vent fluid endmember.•Rainbow vent introduces isotopically light Ba (−0.17 %0) to the deep Atlantic Ocean.•Hydrothermal inputs contribute 4.6 ± 2.2 Gmol/yr Ba to the ocean.