Periodic Reporting for period 1 - BaSIS (Barium in the Southern Ocean Indian Sector)
Reporting period: 2022-11-01 to 2024-10-31
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.
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.
1-Sampling and Field Work
Prior to the BaSIS project, Samples were collected during the SWINGS campaign. These samples spanned a wide range of water column depths , providing critical data to investigate the influence of sediment inputs and establish a foundation for studying barium sources and cycling in this complex region.
2-Method Development and Analytical Implementation
The BaSIS project began with the development and validation of analytical protocols for measuring barium isotopic composition (δ¹³⁸Ba) at the host institution. Leveraging state-of-the-art clean laboratory facilities and TIMS instrumentation, the method was fine-tuned for accuracy and reproducibility. Test analyses on marine samples from diverse origins ensured the robustness of the protocol.
3. Isotopic Analysis of Barium
High-resolution isotopic measurements of δ¹³⁸Ba were performed on water and particle samples from the Kerguelen Plateau. These measurements identified distinct isotopic signatures associated with sediment inputs, which are crucial for understanding the barium cycle and its implications for carbon remineralization.
4. Investigation of Sediment Inputs
A significant focus was placed on characterizing sediment inputs as a key source of barium to the region. The δ¹³⁸Ba data revealed clear contributions from sediments, highlighting their role in shaping the barium distribution and cycling in the Southern Ocean.
5. Biological and Particle Dynamics
δ¹³⁸Ba measurements provided insights into biological processes such as remineralization.
Prior to the BaSIS project, Samples were collected during the SWINGS campaign. These samples spanned a wide range of water column depths , providing critical data to investigate the influence of sediment inputs and establish a foundation for studying barium sources and cycling in this complex region.
2-Method Development and Analytical Implementation
The BaSIS project began with the development and validation of analytical protocols for measuring barium isotopic composition (δ¹³⁸Ba) at the host institution. Leveraging state-of-the-art clean laboratory facilities and TIMS instrumentation, the method was fine-tuned for accuracy and reproducibility. Test analyses on marine samples from diverse origins ensured the robustness of the protocol.
3. Isotopic Analysis of Barium
High-resolution isotopic measurements of δ¹³⁸Ba were performed on water and particle samples from the Kerguelen Plateau. These measurements identified distinct isotopic signatures associated with sediment inputs, which are crucial for understanding the barium cycle and its implications for carbon remineralization.
4. Investigation of Sediment Inputs
A significant focus was placed on characterizing sediment inputs as a key source of barium to the region. The δ¹³⁸Ba data revealed clear contributions from sediments, highlighting their role in shaping the barium distribution and cycling in the Southern Ocean.
5. Biological and Particle Dynamics
δ¹³⁸Ba measurements provided insights into biological processes such as remineralization.
The BaSIS project contributes to advancing our understanding of barium cycling in the Southern Ocean, particularly in regions influenced by sediment inputs such as the Kerguelen Plateau pathways. The project’s results provide new insights into:
• The isotopic composition of barium (δ¹³⁸Ba) and its role in tracing sedimentary contributions to oceanic nutrient cycles.
• Biological processes such as carbon remineralization and the associated biogeochemical transformations of barium in the mesopelagic zone.
• Water mass mixing and its influence on the distribution of barium in the Indian sector of the Southern Ocean.
Potential Impacts
These results enhance the scientific community’s ability to use δ¹³⁸Ba as a tracer for marine biogeochemical processes. This knowledge could inform models predicting oceanic responses to environmental changes, contributing to global efforts to understand and mitigate climate change impacts.
While the project’s primary focus is on fundamental science, further research could expand the application of barium isotopes in other regions, improving the robustness of global ocean biogeochemical models.
• The isotopic composition of barium (δ¹³⁸Ba) and its role in tracing sedimentary contributions to oceanic nutrient cycles.
• Biological processes such as carbon remineralization and the associated biogeochemical transformations of barium in the mesopelagic zone.
• Water mass mixing and its influence on the distribution of barium in the Indian sector of the Southern Ocean.
Potential Impacts
These results enhance the scientific community’s ability to use δ¹³⁸Ba as a tracer for marine biogeochemical processes. This knowledge could inform models predicting oceanic responses to environmental changes, contributing to global efforts to understand and mitigate climate change impacts.
While the project’s primary focus is on fundamental science, further research could expand the application of barium isotopes in other regions, improving the robustness of global ocean biogeochemical models.