Ocean Science
www.ocean-sci.net
1812-0784
1812-0792
3
3
2007
10.5194/os-3-417-2007
http://www.ocean-sci.net/3/417/2007/
http://www.ocean-sci.net/3/417/2007/os-3-417-2007.html
http://www.ocean-sci.net/3/417/2007/os-3-417-2007.pdf
417
427
2007-09-24
On the fast response of the Southern Ocean to changes in the zonal wind
D. J. Webb
david.webb@noc.soton.ac.uk
B. A. de Cuevas
National Oceanography Centre, Southampton SO14 3ZH, UK
Model studies of the Southern Ocean, reported here, show that the Antarctic
Circumpolar Current responds within two days to changes in the zonal wind
stress at the latitudes of Drake Passage. Further investigation shows that
the response is primarily barotropic and that, as one might expect, it is
controlled by topography. Analysis of the results show that the changes in
the barotropic flow are sufficient to transfer the changed surface wind
stress to the underlying topography and that during this initial phase
baroclinic processes are not involved.
<br></br>
The model results also show that the Deacon Cell responds to changes in the
wind stress on the same rapid time scale. It is shown that the changes in the
Deacon Cell can also be explained by the change in the barotropic velocity
field, an increase in the zonal wind stress producing an increased northward
flow in shallow regions and southward flow where the ocean is deep. This new
explanation is unexpected as previously the Deacon Cell has been thought of
as a baroclinic feature of the ocean.
<br></br>
The results imply that where baroclinic processes do appear to be involved in
either the zonal momentum balance of the Southern Ocean or the formation of
the Deacon Cell, they are part of the long term baroclinic response of the
ocean's density field to the changes in the barotropic flow.
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