Picture: Phytoplankton-rich waters off of Argentina. Credit: Norman Kuring, NASA’s Ocean Color Group, using VIIRS data from the Suomi National Polar-orbiting Partnership

Mesoscale eddies are rotating bodies of water with diameters between 30 and 300 km that span weeks to months in the ocean. They are known to carry macronutrients (i.e. nitrate, silicate and phosphate) across the Antarctic Circumpolar Current. Because of extremely limited direct observations of these eddies, it is difficult to calculate the actual quantity of nutrients that these eddies carry.

CLEX and CSIRO researchers observed two cold‐core eddies that were sampled during austral summer and austral autumn in the Southern Ocean south of Tasmania. They found that both eddies had similar nutrients distribution over their depth, especially below the mixed layer depth.

This result encouraged the researchers to combine their real-world observations with satellite observations to calculate the quantities of nutrients carried into the Subantarctic Zone by similar eddies. They found these eddies carried high nitrate and low silicate waters into the Subantarctic Zone.

This transport has a negligible impact on local biological production but it has the capacity to change the nutrient content of waters that are exported from the Southern Ocean to lower latitudes.

  • Paper: Patel, R. S., Llort, J., Strutton, P. G., Phillips, H. E., Moreau, S., Conde Pardo, P., & Lenton, A. (2020). The biogeochemical structure of Southern Ocean mesoscale eddies. Journal of Geophysical Research: Oceans, 125, e2020JC016115. https://doi.org/10.1029/2020JC016115