9:30 AM - 9:45 AM
[ACG36-03] Initiation and termination of eddy activities in the Southern Ocean
Keywords:Antarctic Circumpolar Current, storm tracks, energy analysis, mesoscale eddy
The Antarctic Circumpolar Current (ACC) region is believed to play a central role in the global ocean circulation that affects the Earth’s climate and material circulations. For better understanding of these circulations in the ACC region, detailed knowledges on the ACC dynamics are imperative. Several observational studies have shown that the isopycnal slope associated with the ACC, hence the magnitude of the ACC, is insensitive to the changes in the winds over the region. This interesting aspect, known as the eddy compensation and eddy saturation, has been suggested to be associated with eddy-mean flow interactions in the ACC region. Therefore, eddy-mean flow interactions have been one of the central isssues in the Antarctic Circumpolar Current (ACC) region.
Previous studies have suggested that the eddy kinetic energy (EKE) are sustained even in further downstream of the eddy growth region using idealized channel models. This phenomenon is analogous to "the downstream development" of atmospheric storm tracks. However, the zonal distribution of the EKE obtained from satellite observations does not show such downstream development. Then, initiation and termination mechanisms of the eddy activities are explored from energetic viewpoint based on an eddy-resolving Ocean General Circulation Model (OGCM), named OGCM for the Earth Simulator (OFES). The OFES results demonstrate that a large part of the EKE, generated through the baroclinic energy conversion, is balanced by the diabatic dissipation at their generation sites. It is shown that the vertical pressure flux transports the EKE downward from the depth of eddy energy production above the main thermocline towards the ocean bottom. The EKE converged near the bottom is dissipated due to the diabatic process, indicating that the vertical redistribution of the EKE is the key process for a rather limited zonal extent, i.e. the “downstream decay”, of eddy activities.
Previous studies have suggested that the eddy kinetic energy (EKE) are sustained even in further downstream of the eddy growth region using idealized channel models. This phenomenon is analogous to "the downstream development" of atmospheric storm tracks. However, the zonal distribution of the EKE obtained from satellite observations does not show such downstream development. Then, initiation and termination mechanisms of the eddy activities are explored from energetic viewpoint based on an eddy-resolving Ocean General Circulation Model (OGCM), named OGCM for the Earth Simulator (OFES). The OFES results demonstrate that a large part of the EKE, generated through the baroclinic energy conversion, is balanced by the diabatic dissipation at their generation sites. It is shown that the vertical pressure flux transports the EKE downward from the depth of eddy energy production above the main thermocline towards the ocean bottom. The EKE converged near the bottom is dissipated due to the diabatic process, indicating that the vertical redistribution of the EKE is the key process for a rather limited zonal extent, i.e. the “downstream decay”, of eddy activities.