The Silicon Stable Isotope Distribution Along the GEOVIDE Section of the North Atlantic Ocean

The North Atlantic Ocean and Labrador Sea are crucial regions for the Earth’s climate and thermohaline circulation. However, the chemical oceanography for these regions is poorly constrained making it difficult for scientists to properly interpret or predict the global influence of human-induced increases of atmospheric pCO2. Recently, an internationally funded GEOTRACES oceanographic voyage was realised along the OVIDE section of the North Atlantic Ocean and Labrador Sea (GEOVIDE) where a principal objective of the voyage was to study the influence of the marine biogeochemical cycling of silicon on the global carbon cycle. We present a high-precision dataset that characterizes the silicon isotope distribution along the GEOVIDE section of the North Atlantic Ocean and Labrador Sea. Variations in the natural abundances of stable isotopes of Si expressed as d³⁰Si, the parts per thousand variation in ³⁰Si/²⁸Si, is one key geochemical tool used to track relative differences in the extent of silicic acid removal in surface waters by diatoms. However, successful use of this geochemical tool requires a reasonable understanding of the d ³⁰Si of dissolved silicon throughout the ocean and the processes that control its distribution. Our dataset documents a coherent regional-scale d ³⁰Si distribution that traces the influence and interaction of water masses of differing origins. The formation of Labrador Sea Water by deep convection transports high d³⁰Si values, reflecting Si utilisation at the surface, to depths of ~2000m. The spreading of this water mass propagates this elevated d ³⁰Si signal through the western basins and into the eastern North Atlantic Ocean, where it contrasts with the low d³⁰Si signature of the Si-rich abyssal Lower Deep Water of Southern Ocean origin.