Storm driven mixing in the Sub-Antarctic Zone and implications for phytoplankton biomass and CO2 fluxes

Abstract

The Southern Ocean is one of the stormiest places on earth; here strong mid-latitude storms frequently traverse large distances of this ocean. Beneath these passing storms, this ocean is characterized high eddy kinetic energy (eddies and fronts occupying the meso to sub-mesoscale.. Storms drive significant changes in upper-ocean stratification and turbulence. In addition, storm-driven ocean mixing drives a vertical flux of nutrient that fuels phytoplankton growth in nutrient limited oceans. Yet, the modifying effects of mesoscale (10-100 km. motions on mixing, upward nutrient fluxes and phytoplankton dynamics during and after a storm are not well understood. Idealised simulations with synoptic forcing show that storms intensify vertical nutrient transport pathways associated with mesoscale dynamics resulting in increased phytoplankton production. However, it is unknown where and when these results are relevant in reality in the Southern Ocean. The SOSCEx-STORM experiment aims for the first time to address this important climate knowledge gap by simultaneously measuring how these intense storms impact upper ocean physics and biogeochemistry within meso to submesoscale fronts. Novel twinned autonomous ocean robots (Wave Glider coupled to a Slocum with a MicroRider turbulence package. experiments have been designed to directly observe scale sensitivities and links between storm-driven wind forcing, upper-ocean mixing, phytoplankton biomass and CO2 fluxes. The preliminary results from the first SOSCEx-STORM experiment carried out in the Sub-Antarctic Zone during SANAE57 (December 2017 – February 2018. are presented here. Given that the SO is arguably the main source of medium-term uncertainty in global CO2 fluxes, understanding such climate sensitivities is of critical importance. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.