Factors Modulating the Variability of Eddy Kinetic Energy in the Southern Ocean from Idealized Simulations

Abstract

The Southern Ocean is characterized by high levels of eddy activity, which are crucial for the vertical exchange or transfer of matter, energy, and momentum. Previous studies have shown that the variability of eddy kinetic energy (EKE) in the Southern Ocean is primarily intrinsic. However, the factors that modulate the forced and intrinsic variability of the EKE remain unclear. In this study, we conduct a series of idealized simulations and apply ensemble analysis to investigate the impact of topography and wind-stress perturbations on the forced and intrinsic variability of the EKE and their relative contributions. The results show that while the large wind-stress perturbation obviously increases the forced variability of EKE by enhancing the Ekman response, the topography not only amplifies the forced variability by sharpening isopycnals and energizing the mean flow but also intensifies the intrinsic variability of EKE. However, EKE variabilities in both complex-topographic and flat-bottom cases are dominated by their intrinsic components, even when driven by escalated wind-stress perturbations. These findings deepen our understanding of the eddy field, its ongoing variability in the Southern Ocean, and its potential impact on the balance of heat, carbon, and freshwater.