The dynamical controls on the antarctic circumpolar current with the use of general circulation models

• Main Author: Grezio, Anita
• Format: Thesis
• Language: English
• Published: University of Southampton 2002
• Subjects: Antarctic; The Antarctic; Kerguelen; Drake Passage; Pacific; Curl; Antarc*
• Online Access: https://eprints.soton.ac.uk/464679/; https://eprints.soton.ac.uk/464679/1/843443.pdf

Three general circulation models (FRAM, OCCAM and POP) are used in order to investigate the dynamics of the Antarctic Circumpolar Current (ACC) at the Drake Passage latitudes (ACCB) where the ACC is unbounded. In these models bottom form stress balances the wind stress in the momentum budgets. In the vorticity budgets the main balance is between wind curl and bottom pressure torque in FRAM and OCCAM. In the higher resolution model (POP) the non linear advection is one of the main terms. Whereas standing eddies mainly decelerate the flow in the ACCB, transient eddies play a different role in the three models. In the upper levels transient eddies accelerate the flow in POP and FRAM, but decelerate the flow in OCCAM. The behaviour of standing and transient eddies changes throughout the water column in the ACCB and eddies have a dragging effect on the flow below the levels where the topography starts to obstruct the flow. The crucial role of topography is investigated using a set of numerical experiments. In the coarse version of OCCAM Kerguelen Plateau is lowered and the Drake Passage Region and the Antarctic-Pacific Ridge are removed. Results from the analysis in the ACCB indicate that changing topography has a local effect. The complete investigation of the ACC dynamics is extended to the ACC Path (ACCP). The vorticity budgets show that the Drake Passage Region affects all of the ACC flow. Removing Drake Passage reduces the contributions of the bottom pressure torque to the vorticity balance and the region of Sverdrup-like balance is extended. The key role for all the ACC is played by Drake Passage but not from other topographic features.