Australia: The Land Where Time Began

A biography of the Australian continent 

Rossby Waves Mediate Impacts on West Antarctic Atmospheric Circulation of Tropical Oceans  

Climate change around Antarctica has been found by recent studies to link to the sea surface temperature of tropical oceans, with teleconnections from the Pacific, Atlantic and Indian Oceans which make different contributions to the climate of Antarctica. In this study Li et al. have identified the impacts of each ocean basin on the circulation of the Southern Hemisphere in the austral winter by the use of simulation results from a comprehensive atmospheric model, an idealised dynamical core model, and a theoretical Rossby wave model. It is shown by the results of these comparisons that warming in the tropical Atlantic Ocean, warming of the Indian Ocean, and cooling of the eastern Pacific Ocean are all capable of deepening the Amundsen Sea Low that is located adjacent to West Antarctica, while warming of the western Pacific increases the pressure to the west of the international date line, encompassing the Ross Sea as well as regions to the south of the Tasman Sea. These tropical ocean basins were found to work together linearly to modulate the circulation of the atmosphere around West Antarctica in the austral winter. It was indicated by further analysis that these teleconnections depend critically on stationary Rossby wave dynamics and therefore are sensitive to the background flow, in particular the subtropical/midlatitude jet. Wind shear is amplified near these jets, which strengthens the generation of Rossby waves. On the other hand, the meridional gradient of the absolute vorticity near the edges of the jets is also enhanced. The edge of the jet may reflect stationary Rossby wave trains, thereby serving as a waveguide, as a consequence of the Rossby wave dispersion relationship. As well as identifying the roles of each of the tropical ocean basins in the tropical-Antarctic teleconnection, the simulation results also suggest that a deeper understanding of teleconnections requires a better estimation of the atmospheric jet structures.

Sources & Further reading

1. Li, X., D. M. Holland, E. P. Gerber and C. Yoo (2015). "Rossby Waves Mediate Impacts of Tropical Oceans on West Antarctic Atmospheric Circulation in Austral Winter." Journal of Climate 28(20): 8151-8164.