Sub-mesoscale Circulation in the Southern Ocean

Wednesday, 17 December 2014
Isabella Rosso, Australian National University, Canberra, ACT, Australia, Andrew Hogg, Australian National University, Canberra, Australia, Peter G Strutton, University of Tasmania, Hobart, TAS, Australia, Andrew E Kiss, University of New South Wales Canberra at the Australian Defence Force Academy, Canberra, Australia and Richard Matear, CSIRO Hobart, Hobart, Australia
The Southern Ocean is dominated by the Antarctic Circumpolar Current, a quasi-zonal current that encircles Antarctica, is steered by the topography and whose energy is characterized by mesoscale eddies and fronts. Understanding its dynamics is of fundamental importance, given its major role in the carbon cycle and, hence, in the global climate system.

The first sub-mesoscale-resolving (1/80°) model of the Kerguelen Plateau Region, located in the Indian sector of the Southern Ocean, has been implemented. The model resolves sub-mesoscale filamentary structures and shows patchiness in the sub-mesoscale eddy kinetic energy and vertical velocities. The vertical velocities, which are dramatically higher than in mesoscale-resolving models, strongly enhance the vertical exchange of advected Lagrangian particles. Furthermore, we find evidence that the patchiness in the sub-mesoscale fields is related to the topographic features present in this location and that the topography indirectly generates these sub-mesoscale structures.

We conclude that in the Southern Ocean, with its low stratification and high eddy kinetic energy, the sub-mesoscales might provide a fundamental and new mechanism for vertical transport in this region.