Iron supply pathways between the surface and subsurface waters of the Southern Ocean : from winter entrainment to summer storms

• Main Authors: Nicholson, S. A., /Levy, Marina, /Jouanno, Julien, /Capet, Xavier, Swart, S., Monteiro, P. M. S.
• Format: Text
• Language: English
• Published: 2019
• Subjects: storms; seasonal iron supply; winter entrainment; eddy advection; fronts; Southern Ocean
• Online Access: https://www.documentation.ird.fr/hor/fdi:010077431

Dissolved iron (DFe) plays an immeasurable role in shaping the biogeochemical processes of the open-ocean Southern Ocean. However, due to observational constraints iron supply pathways remain poorly understood. Using an idealized eddy-resolving physical-biogeochemical model representing a turbulent sector of the Southern Ocean with seasonal buoyancy forcing and zonal winds overlaid by storms, we quantify the importance of a range of subsurface and surface iron supply mechanisms. The main physical supply pathways to the surface layer are via eddy advection and winter convective mixing in equal proportions. The associated subsurface loss of DFe is restocked via net remineralization (75%) and eddy advection (25%). Summer storms resulted in weak DFe supplies relative to the seasonal supplies (<7.6%). However, in situations of deep summer mixed layers and when interacting with underlying ocean fronts, summer storms resulted in enhanced diffusive and advective DFe supplies and raised summer primary production by 20% for several days.