The Antarctic Circumpolar Wave: A beta effect in ocean-atmosphere coupling over the Southern

• Main Authors: Warren B. White, Shyh-chin Chen, Ray, G. Peterson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1998
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.584.7572; http://sam.ucsd.edu/sio219/white.pdf

The Antarctic circumpolar wave (ACW) is a nominal 4-yr climate signal in the ocean–atmosphere system in the Southern Ocean, propagating eastward at an average speed of 6–8 cm s21, composed of two waves taking approximately 8 years to circle the globe. The ACW is characterized by a persistent phase relationship between warm (cool) sea surface temperature (SST) anomalies and poleward (equatorward) meridional surface wind (MSW) anomalies. Recently, White and Chen demonstrated that SST anomalies in the Southern Ocean operate to induce anomalous vortex stretching in the lower troposphere that is balanced by the anomalous meridional advection of planetary vorticity, yielding MSW anomalies as observed. In the present study, the authors seek to understand how this atmospheric response to SST anomalies produces a positive feedback to the ocean (i.e., an anomalous SST tendency displaced eastward of SST anomalies) that both maintains the ACW against dis-sipation and accounts for its eastward propagation. To achieve this, we couple a global equilibrium climate model for the lower troposphere to a global heat budget model for the upper ocean. In the absence of coupling, the model Antarctic Circumpolar Current (ACC) advects SST anomalies from initial conditions to the east at speeds slower than observed, taking 12–14 years to circle the globe with amplitudes that become insignificant after 6–8 years. In the presence of coupling, eastward speeds of the model ACC are matched by those due to