Intense Submesoscale Upwelling in Anticyclonic Mesoscale Eddies
Liam Brannigan, University of Oxford, Physics, Oxford, United Kingdom, David Philip Marshall, University of Oxford, Oxford, United Kingdom, Sheldon Bacon, University of Southampton, Southampton, United Kingdom, A. J. George Nurser, National Oceanography Center, Soton, Southampton, United Kingdom and Jan Kaiser, University of East Anglia, Norwich, United Kingdom
Abstract:
High resolution simulations of mesoscale eddies show that wind-driven extraction of potential vorticity leaves the mixed layer of mesoscale eddies unstable to symmetric instability. At submesoscale-permitting resolutions the symmetric instability leads to intense upwelling of thermocline fluid along isopycnals into the mixed layer of the eddy. There is a strong cyclone-anticyclone asymmetry as the instability in the anticyclone exhibits much faster growth and deeper penetration into the thermocline. A simple limiting nutrient experiment shows that resolving these filaments leads to much higher primary productivity in anticyclones that may account for observed high primary production in the eddies. In addition, symmetric instability provides a mechanism for dissipating the kinetic energy of the mesoscale eddy. Global estimates of the nutrient upwelling and energy dissipation due to the mechanism will be provided.
