The Southern Ocean (SO) plays a pivotal role in global climate regulation and ocean biogeochemistry, acting as a major sink for atmospheric carbon dioxide (CO2). Its unique dynamics, driven by the Antarctic Circumpolar Current, influence global nutrient cycles and marine ecosystems. Despite its significance, the SO remains one of the least understood regions due to its remoteness and the complexity of its processes. The SO is particularly noteworthy for its extensive yet underutilized reservoir of macronutrients, constrained by limiting factors like light and micronutrient availability (e.g. iron and manganese). Understanding these dynamics is essential to predict how this key region will respond to climate change and its role in carbon sequestration.
Central to the SO’s biogeochemical processes is the mesopelagic zone, where carbon and nutrients are recycled through the activity of phytoplankton and remineralization processes. The element barium (Ba) has emerged as a promising tracer for organic carbon remineralization. However, the global Ba cycle remains poorly understood, with key uncertainties surrounding sources such as hydrothermal vents, deep sediments, and biological activity. These limitations hinder our ability to use Ba effectively as a biogeochemical tracer.
The BaSIS project addresses this critical knowledge gap by focusing on barium isotopic composition (δ¹³⁸Ba), a cutting-edge approach to disentangle Ba sources and processes in the SO. Ba isotopes offer unique insights into the contributions of biological and sedimentary processes, as well as particle dynamics. This study, the first of its kind in the SO, will significantly advance our understanding of the region’s role in the global Ba cycle and its broader implications for ocean biogeochemistry.
Project Pathway to Impact
BaSIS aims to deliver transformative insights into the Ba cycle through high-resolution isotopic measurements across the Indian sector of the SO. By leveraging samples collected during the SWINGS project—a multidisciplinary campaign focusing on trace element dynamics—BaSIS will:
1. Document the distribution of Ba and Ba isotopes across major water masses to uncover their influence on the global ocean Ba cycle.
2. Characterize sedimentary sources of Ba on the Kerguelen Plateau to quantify their contributions.
3. Investigate biological and particle-mediated Ba transformations, including export and remineralization processes.
These objectives align with broader scientific priorities in oceanography, providing critical data to refine global biogeochemical models. The project’s outcomes will directly inform policies related to climate change mitigation and marine ecosystem management by enhancing predictions of carbon cycling in the ocean.
