2076 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 35 Adjustment of the Southern Ocean to Wind Forcing on Synoptic Time Scales

• Main Authors: Wilbert Weijer, Sarah, T. Gille
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Southern Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.411.8233; http://www-pord.ucsd.edu/~sgille/pub_dir/weijer_gille05.pdf

This study addresses the response of the Southern Ocean to high-frequency wind forcing, focusing on the impact of several barotropic modes on the circumpolar transport. A suite of experiments is performed with an unstratified model of the Southern Ocean, forced with a stochastic wind stress that contains a large range of frequencies with synoptic time scales. The Southern Ocean adjustment displays a different character for frequencies below and above 0.2 cpd. The low-frequency range is dominated by an “almost-free-mode” response in the region where contours of f/H are obstructed by only a few bathymetric features; the truly free mode only plays a minor role. Topographic form stress, rather than friction, is the dominant decay mechanism of the Southern Mode. It leads to a spindown time scale on the order of 3 days. For the high-frequency range, the circumpolar transport is dominated by the resonant excitation of oscillatory modes. The “active ” response of the ocean leads to strong changes and even discontinuities in the phase relation between transport and wind stress. 1.