Stirring up the biological pump: Vertical mixing and carbon export in the Southern Ocean

• Other Authors: Stukel, Michael R (authoraut), Ducklow, Hugh W (authoraut)
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Antarctic; Antarctic Peninsula; Palmer Station; Palmer-Station; Southern Ocean; Antarc*
• Online Access: https://diginole.lib.fsu.edu/islandora/object/fsu%3A531351/datastream/TN/view/Stirring%20up%20the%20biological%20pump.jpg

The biological carbon pump (BCP) transports organic carbon from the surface to the ocean’s interior via sinking particles, vertically migrating organisms, and passive transport of organic matter by advection and diffusion. While many studies have quantified sinking particles, the magnitude of passive transport remains poorly constrained. In the Southern Ocean weak thermal stratification, strong vertical gradients in particulate organic matter, and weak vertical nitrate gradients suggest that passive transport from the euphotic zone may be particularly important. We compile data from seasonal time-series at a coastal site near Palmer Station, annual regional cruises in the Western Antarctic Peninsula (WAP), cruises throughout the broader Southern Ocean, and SOCCOM autonomous profiling floats to estimate spatial and temporal patterns in vertical gradients of nitrate, particulate nitrogen (PN), and dissolved organic carbon (DOC). Under a steady-state approximation, the ratio of ∂PN/∂z to ∂NO3-/∂z suggests that passive transport of PN may be responsible for removing 46% (37%-58%) of the nitrate introduced into the surface ocean of the WAP (with DOM contributing an additional 3-6%) and for 23% (19%-28%) of the BCP in the broader Southern Ocean. A simple model parameterized with in situ nitrate, PN, and primary production data suggested that passive transport was responsible for 54% of the magnitude of the BCP in the WAP. Our results highlight the potential importance of passive transport (by advection and diffusion) of organic matter in the Southern Ocean, but should only be considered indicative of high passive transport (rather than conclusive evidence) due to our steady-state assumptions. Keywords: Carbon export, Plankton, Mixing, Subduction, Nitrogen cycle, Carbon cycle Publication Note: Published version can be found at https://doi.org/10.1002/2017GB005652 Preferred Citation: Stukel, M. R. and H. W. Ducklow (2017). "Stirring up the biological pump: Vertical mixing and carbon export in the Southern Ocean." ...