Decadal Variabilities over the Tropical Ocean Basins Impact on the West Antarctic Climate

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. This study investigate the teleconnection between Tropical Ocean and the West Antarctic climate in austral winter by means of data diagnostics and numerical simulations.

In this study, the tropical oceans are divided into several different ocean sectors. Both the analyses and simulation results 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. Similarly, the Indian Ocean warming and the La Nina type changes over the Pacific Ocean may impact on the atmospheric circulation over the West Antarctica through the same mechanisms. These circulation changes may further impact on the surface air temperature and sea ice concentration.

Moreover, 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 model 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.