On the fast response of the Southern Ocean to changes in the zonal wind

[摘要] Model studies of the Southern Ocean, reported here, show that the AntarcticCircumpolar Current responds within two days to changes in the zonal windstress at the latitudes of Drake Passage. Further investigation shows thatthe response is primarily barotropic and that, as one might expect, it iscontrolled by topography. Analysis of the results show that the changes inthe barotropic flow are sufficient to transfer the changed surface windstress to the underlying topography and that during this initial phasebaroclinic processes are not involved.

The model results also show that the Deacon Cell responds to changes in thewind stress on the same rapid time scale. It is shown that the changes in theDeacon Cell can also be explained by the change in the barotropic velocityfield, an increase in the zonal wind stress producing an increased northwardflow in shallow regions and southward flow where the ocean is deep. This newexplanation is unexpected as previously the Deacon Cell has been thought ofas a baroclinic feature of the ocean.

The results imply that where baroclinic processes do appear to be involved ineither the zonal momentum balance of the Southern Ocean or the formation ofthe Deacon Cell, they are part of the long term baroclinic response of theocean's density field to the changes in the barotropic flow.

[学科分类] 海洋学与技术