Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean

• Published in: Communications Earth & Environment
• Main Authors: Tangunan, Deborah, Berke, Melissa A., Cartagena Sierra, Alejandra, Flores, José Abel, Gruetzner, Jens, Jiménez Espejo, Francisco J., LeVay, Leah J., Baumann, Karl-Heinz, Romero, Óscar, Saavedra-Pellitero, Mariem, Coenen, Jason J., Starr, Aidan, Hemming, Sidney R., Hall, Ian R.
• Other Authors: Ministerio de Ciencia e Innovación (España), European Commission, German Research Foundation, Ministerio de Ciencia, Innovación y Universidades (España)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Nature Publishing Group 2021
• Subjects: Indian; Southern Ocean
• Online Access: http://hdl.handle.net/10261/275960; https://doi.org/10.1038/s43247-021-00148-0; https://doi.org/10.13039/501100000780; https://doi.org/10.13039/501100001659; https://doi.org/10.13039/501100004837

In the southern Indian Ocean, the position of the subtropical front - the boundary between colder, fresher waters to the south and warmer, saltier waters to the north - has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations. Migration of the Subtropical Front during glacial and interglacial periods resulted in variability in the strength of the biological pump in the Southern Ocean sector of the Indian Ocean, according to sedimentary records from the Agulhas Plateau. This work used samples and data provided by the IODP. We are thankful for the support from the crew of the R/V JOIDES Resolution and IODP staff. This work is funded through the Universidad de Salamanca Postdoctoral Contract supported by the Ministerio de Ciencia, Innovación y Universidades Grant RTI2018-099489-B-I00 and the German Science Foundation (DFG) Research Center/Cluster of Excellence ‘The Ocean in the Earth System' (MARUM; Grant No. 49926684). We acknowledge financial support from the National Science Foundation of the US under Award No. 1737218 (M.A.B), the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant Agreement No. 799531 (M.S.P.), and ...