The Sub-surface Biogeochemical Structure of Southern Ocean Eddies

Jiaoyang Su, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia; University of Tasmania, Hobart, TAS, Australia and Peter G Strutton, University of Tasmania, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia
Eddies play several key roles in the Southern Ocean. They are thought to dissipate additional energy that the ocean receives via climate-related changes in winds. They also have the potential to move biological and chemical tracers north and south across Southern Ocean fronts. We know that the temperature and salinity signatures of Southern Ocean eddies penetrate to about 1500 m, but we know much less about the subsurface structure of nutrients, oxygen and carbon. In this work, biogeochemical Argo float profiles from the Southern Ocean Carbon and Climate Observations and Modelling project (SOCCOM), and other international programs, are matched with eddies using satellite altimetry data. The subsurface structure of nitrate, oxygen, chlorophyll fluorescence and particulate backscatter of both cyclonic and anticyclonic eddies are revealed quantitively. Below 100m, cyclonic eddies show positive anomalies of nitrate and anticyclonic eddies show negative anomalies compared to surrounding waters, as expected. In surface waters, results thus far are counter-intuitive, perhaps owing to the coverage of the growing data set. In addition to quantifying the biogeochemical structure of Southern Ocean eddies, this work lays the foundation for regional and seasonal analyses, and for the investigation of time-varying properties such as net community production in eddies.