On the response of the Antarctic Circumpolar Current transport to climate change in coupled climate models
Article first published online: 10 AUG 2011
Copyright 2011 by the American Geophysical Union.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 116, Issue C8, August 2011
How to Cite
2011), On the response of the Antarctic Circumpolar Current transport to climate change in coupled climate models, J. Geophys. Res., 116, C08011, doi:10.1029/2010JC006757., , and (
- Issue published online: 10 AUG 2011
- Article first published online: 10 AUG 2011
- Manuscript Accepted: 12 MAY 2011
- Manuscript Revised: 24 MAR 2011
- Manuscript Received: 22 OCT 2010
- Antarctic Circumpolar Current;
- climate models;
- future response
 The Coupled Model Intercomparison Project phase 3 (Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report) models show a consistent intensification and poleward shift of the westerly winds over the Southern Ocean during the 21st century. However, the responses of the Antarctic Circumpolar Currents (ACC) show great diversity in these models, with many even showing reductions in transport. To obtain some understanding of diverse responses in the ACC transport, we investigate both external atmospheric and internal oceanic processes that control the ACC transport responses in these models. While the strengthened westerlies act to increase the tilt of isopycnal surfaces and hence the ACC transport through Ekman pumping effects, the associated changes in buoyancy forcing generally tend to reduce the surface meridional density gradient. The steepening of isopycnal surfaces induced by increased wind forcing leads to enhanced (parameterized) eddy-induced transports that act to reduce the isopycnal slopes. There is also considerable narrowing of the ACC that tends to reduce the ACC transport, caused mainly by the poleward shifts of the subtropical gyres and to a lesser extent by the equatorward expansions of the subpolar gyres in some models. If the combined effect of these retarding processes is larger than that of enhanced Ekman pumping, the ACC transport will be reduced. In addition, the effect of Ekman pumping on the ACC is reduced in weakly stratified models. These findings give insight into the reliability of IPCC-class model predictions of the Southern Ocean circulation and into the observed decadal scale steady ACC transport.