| In the past decades, Antarctica has experienced a series of dramatic climate changes, with global impact through their contribution to sea level rise. While increased radiative forcing from greenhouse gases and stratosphere ozone has played a role in Antarctic surface temperature change, the regional scale changes in surface climate are strongly influenced by changes in the atmospheric circulation, and are thus further linked to the Tropical Ocean through Tropical-Antarctic teleconnections. In my PhD research, I first established a teleconnection between North and Tropical Atlantic and Antarctic climate in austral winter by means of data diagnostics and numerical simulations. The analyses and simulation results all show that, the North and Tropical Atlantic SST warming during June-July-August (JJA) season generates stationary Rossby Wave trains, propagating to the polar region and changing the atmospheric circulation around Antarctica. These circulation changes may further impact on the surface air temperature and sea ice concentration. I then further investigated the robustness and physical dynamics of the Atlantic-Antarctic teleconnection. In particular, I study the linearity and seasonality of the teleconnection independently using comprehensive, idealized, and theoretical atmospheric models. The results show that, the teleconnection between Tropical Atlantic and Antarctic atmospheric circulation, especially the circulation around Amundsen Sea Low area, are robust in austral winter, spring, and autumn, but is weakened or even disappear in austral summer. The stationary Rossby Wave trains generated by the deep convection over Atlantic region depends critically on the location and strength of the southern hemisphere sub-tropical jet, which is weakened during austral summer. I further investigate the roles of different ocean basins and ocean sectors in the context of the austral winter Tropical -- Antarctic teleconnection, as several other tropical ocean basins were found to remotely influence Antarctic climate system. Tropical Oceans are divided into several different ocean sectors, and the additive properties between the SST forcing from different ocean basins were studied. The simulation results imply a surprisingly pure linear dynamics. Specifically, the accumulated responses of the atmospheric circulation forced by the SST from each individual tropical oceans are almost identical to the total response in the atmospheric circulation forced by the entire tropical oceans. Based on this linearity property, I then estimate the impact of different ocean basins individually using CAM4 simulation. The simulation results indicate that the Atlantic Ocean plays the major role in different Tropical -- Antarctic teleconnections, by contributing about 58% of total SLP reduction over Amundsen Sea Low area. In addition, the Indian Ocean, West Pacific, East Pacific, and South Pacific Convergence Zone area also play important roles by either increasing or decreasing the SLP over the Amundsen Sea area. Other simulations using idealized GFDL model, as well as theoretical stationary Rossby Wave models all support the CAM4 results and point to the same conclusion. |
