The Tibetan Plateau's Far-Reaching Impacts on Arctic and Antarctic Climate: Seasonality and Pathways

As the highest and most extensive plateau in the world, the Tibetan Plateau (TP) has remarkable effects on global climate. Through coupled model sensitivity experiments with and without the TP, we show that the TP can affect the Arctic directly via orography-forced stationary waves, and influence the Antarctic indirectly via stationary waves forced by sea surface temperature (SST) in the Indian Ocean. These far-reaching impacts occur mainly in wintertime. The fast atmospheric processes play an important role; particularly, the midlatitude westerly flow, which is stronger and closer to the equator in winter, provides a favorable condition for the eastward and poleward energy propagation of the forced waves. In the Northern Hemisphere, removing the TP causes a wave train traveling from the Asian continent to the North America-Atlantic Ocean region, resulting in intensified westerlies and thus an enhancement of stratospheric polar vortex and Arctic cooling. The pathways are northeastward directly in the upper level due to the background westerlies, while they are eastward and then northeastward in the lower level, modulated by the winter monsoon. To the south, the TP perturbation causes an anomalous cross-equatorial flow, leading to an anomalous SST dipole pattern in the Indian Ocean in the austral winter; this generates stationary waves propagating energy southeastward from the tropical Indian Ocean to the Antarctic, resulting in a Rossby wave train circulating around the Antarctic. Our study identifies the seasonality and pathways of the TP affecting the polar regions, which may help to understand the role of the TP in the future climate changes in polar regions.