The Vertical Transport in the Ocean due to Sub-mesoscale structures: Impacts in the Kerguelen Region

Several studies have recently found that sub-mesoscale structures of O(10)km may generate a strong vertical transport of tracers in the ocean. Our interest is focused in investigating the impacts that this transport has in the Indian Sector of Southern Ocean. This ocean is known to be a high nutrient, low chlorophyll (HNLC) environment. However, there are several locations of elevated chlorophyll concentration, amongst which is the seasonal bloom originating above and downstream of the Kerguelen Plateau. While the importance of the Kerguelen bloom has been largely documented, the mechanism that drives iron to this region, and consequently triggers the bloom, is unclear. Existing hypotheses for the explanation of the seasonal Kerguelen bloom have focused on potential mechanisms to transport iron into the region and have provided different explanations for the blooms occurring over and downstream of the plateau.

We propose a new hypothesis which may account for vertical transport of iron in the Kerguelen Plateau region. We run numerical experiments at a horizontal resolution of 1/20° and 1/80° and investigate the dynamics and transport of tracers at the sub-mesoscales. The simulations use realistic topography and idealized surface forcing in a domain located at (57E-129E, 35S-70S). A Lagrangian tracking tool is also used to investigate the transport due to the different scale structures resolved by the models.