On the spatial and temporal distribution of near-inertial energy in the Southern Ocean

We use an eddying realistic primitive-equation model of the Southern Ocean to examine the spatial and temporal distribution of near-inertial wind-power input (WPI) and near-inertial energy (NIE) in the Southern Ocean. We find that the modeled near-inertial WPI is almost proportional to inertial wind-stress variance (IWSV), while the modeled NIE is modulated by the inverse of the mixed-layer depth. We go on to assess recent decadal trends of near-inertial WPI from trends of IWSV based on reanalysis wind stress. Averaged over the Southern Ocean, annual-mean IWSV is found to have increased by 16% over the years 1979–2011. Part of the increase of IWSV is found to be related to the positive trend of the Southern-Annular Mode over the same period. Finally, we show that there are horizontal local maxima of NIE at depth that are almost exclusively associated with anticyclonic eddies.