Dissolved gallium in the Atlantic Ocean

Gallium is geochemically similar to aluminum, though less reactive. As such, gallium is potentially useful to resolve questions about the aluminum distribution. Dissolved gallium data from 14 profiles in the Atlantic Ocean as well as additional surface water samples are presented here. The results verify that the main delivery of gallium to the surface ocean is aeolian and that gallium has a surface water residence time longer than aluminum but probably similar to manganese (i.e., order of decades). Surface water gallium concentrations in the Sargasso Sea are unusually high (>40 pmol kg−1). There is likely an anthropogenic component in the Sargasso Sea, but residence time effects may also be at work. Dissolved gallium profiles in the Atlantic are generally similar to those of aluminum. The subsurface gallium maximum previously observed in the northeast Pacific is not found, but may be obscured by advective features in the Atlantic. Deep waters in the Atlantic show generally conservative behavior of gallium, supporting the concept of using aluminum as a deep water tracer in the Atlantic. However, gallium enrichments are observed in the deep waters of the Norwegian Sea and Iceland Basin. A consideration of possible sources of these enrichments suggests that release from resuspended sediments is the most likely source mechanism.