Exploring the Impact of a Southern Ocean Anticyclonic Eddy on Biogeochemical Structure Using BGC-Argo Float Observations

Recent studies have found that eddies in the Southern Ocean can contribute to both uptake and outgassing of CO₂, emphasizing a need to understand the impact of eddies on biogeochemical structure in the Southern Ocean.  Despite having a significant role in climate regulation and global ocean transport, the Southern Ocean and its eddies are largely under-sampled, leaving many unknowns when trying to understand how the Southern Ocean can be impacted by a changing climate.  Whereas CO₂ and other biogeochemical properties including oxygen and nitrate (which can be studied as indicators of a changing climate) are historically under-sampled and understudied in the Southern Ocean, the use of autonomous vehicles has allowed for the collection of high-quality data that can be used to analyze the impact of eddies on Southern Ocean biogeochemical structure.  A SOCCOM BGC-Argo Float encountered and sampled an anticyclonic eddy in the area lying between 54° and 50° S and 148° and 143° W in February 2019.  During the encounter, the float collected daily profiles of the biogeochemical structure within the eddy.  Using additional resources for sea surface height, wind, and ocean currents, we conduct a spatial and temporal analysis of the biogeochemical structure of the eddy.  We compare float data to climatologies, examine the physical properties that impact the mixed layer depth within and around the eddy, and understand how these properties influence biogeochemical variability caused by the eddy.  In addition, we pull biogeochemical data from all known eddy encounters by SOCCOM BGC-Argo floats and determine the significance of eddies on biogeochemical structure in the Southern Ocean.