Dependence of the transport in channel models of the ACC on the Rossby radius of deformation

• Main Author: Crevier, Louis-Philippe.
• Other Authors: Straub, David N. (advisor)
• Format: Thesis
• Language: English
• Published: McGill University 1998
• Subjects: Physical Oceanography; Antarctic; Drake Passage; The Antarctic; Antarc*
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21532

It has been suggested that the transport of the Antarctic Circumpolar Current is set, essentially, by the southward Sverdrup flux at latitudes just north of Drake Passage. Although this idea is consistent with observations, it has been critized in that Sverdrup dynamics fail at Drake Passage latitudes. Here, we think of the total transport as being comprised of two components: one associated with the basin-like dynamics to the north of Drake Passage and the other associated with the dynamics of the Drake Passage latitude band itself. The Drake Passage latitudes are often simulated using channel models with bottom topography. For a two-layer channel, large topography effectively blocks geostrophic contours at depth and allows zonally-reconnecting contours in the upper layer. This concentrates the through-channel transport in the model's upper layer. Furthermore, it is argued that the statistical steady state for wind-driven channel flow (that is not too viscous) should be baroclinically unstable. Assuming marginal instability then leads to an estimate of the through-channel transport. A two-layer primitive-equation channel model with bottom topography and wind forcing is used to test this relationship. Model integrations are made to obtain statistical steady states for a range of parameters. The Rossby radius and the wind strength are varied as the theory predicts that transport should go like the square of the former and be relatively insensitive to the latter. Integrations to test the robustness of these results to model resolution are also conducted.