A model study of the Southern Ocean dynamics: mean flow, intrinsic variability and teleconnections.

• Main Author: Sgubin, Giovanni
• Format: Doctoral or Postdoctoral Thesis
• Language: Italian; English
• Published: 2011
• Subjects: Antarctic; Drake Passage; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://www.fedoa.unina.it/8940/; http://www.fedoa.unina.it/8940/1/Sgubin.pdf; https://doi.org/10.6092/UNINA/FEDOA/8940

The general circulation in the Southern Ocean plays a significant role in the global climate, as it connects all the major world basins, carrying anomalies around the globe through the Antarctic Circumpolar Current (ACC). A better understanding of the physical mechanisms that take place in this region can help improve the knowledge of the global ocean circulation. In this context, this thesis deals with the dynamics of the Southern Ocean and of the ACC by means of a numerical model approach. Results obtained from the primitive equation sigma-coordinate Princeton Ocean Model (POM) concerning both the mean circulation and the intrinsic variability in the Southern Ocean are presented and discussed. Preliminary simulations are performed in order to set up a consistent circulation for the Sothern Ocean, i.e. with a realistic structure of the ACC fronts and with acceptable values of the volume transport across the Drake Passage. Steady wind stress and heat fluxes are imposed based on climatological data in a periodic channel with realistic coastlines and bathymetry. In order to investigate the role of the bottom form drag on the dynamical balance of the ACC, a hierarchy of model implementations for a homogeneous ocean are first developed using both a flat-bottom and an idealized topography. Baroclinicity is also considered: in particular, the meridional density gradient is found to be a significant element, as it activates the JEBAR effect and prevents a total topographic steering. A consistent model for the ACC is finally proposed using realistic bottom topography and background stratification. An overview of the simulations in an eddy-permitting resolution shows evidence of intrinsic variability of the ACC. The latter is found to be strongly sensitive to the bottom topography, eddy viscosity and stratification. By analyzing the results of these numerical experiments we investigate the statistical interrelationships between different regions in the Southern Ocean, and give a first estimate of teleconnections in the ...