Interregional interactions on multiple timescales that will help our understanding of regional climate change under a warmer climate

An increasing number of studies have focused on the linkages between the tropics and polar regions. The observed expansion of sea ice in Antarctica and cooling in the Southern Ocean have long been considered paradoxes in global warming, especially when compared with amplified warming in the Arctic region. Based on observations and simulations from multiple large ensembles of numerical model experiments, it has been shown that the expansion of sea ice in Antarctica in recent decades can be attributed to the decadal variability in the tropical Pacific Ocean through atmospheric teleconnections. This tropical-polar teleconnection may also affect the future projection of changes in Antarctica and the Southern Ocean. Warming in the Southern Ocean during the 21st century can be modulated by changes in the amplitude of the El Niño-Southern Oscillation (ENSO). The projected ENSO enhancement may slow warming of the Southern Ocean by weakening surface winds and the uptake of heat in this region.

The effect of global warming on the biochemical environment has been widely studied in polar regions, and increased attention has recently been paid to the effects of chemical changes on the polar climate. The depletion of stratospheric ozone and increases in tropospheric ozone may both contribute to warming of the interior Southern Ocean by causing spiciness changes along isopycnals and deepening the isopycnals in the Southern Ocean, respectively.