Reduced connection between the East Asian Summer Monsoon and Southern Hemisphere Circulation on interannual timescales under intense global warming

• Published in: Climate dynamics Vol. 51; no. 9-10; pp. 3943 - 3955
• Main Authors: Yu, Tianlei, Guo, Pinwen, Cheng, Jun, Hu, Aixue, Lin, Pengfei, Yu, Yongqiang
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2018; Springer; Springer Nature B.V; Springer-Verlag
• Subjects: Atlantic Meridional Overturning Circulation (AMOC); Bridges; Cerebral hemispheres; Circulation; Climate; Climate change; Climate models; Climate system; Climatology; Computer simulation; Connecting; Earth and Environmental Science; Earth Sciences; East Asian monsoon; Environmental aspects; Freshwater; Geophysics/Geodesy; Global warming; Greenhouse effect; Greenhouse gases; Heat exchange; Heat transport; Inland water environment; Meridional heat transport; Meteorology & Atmospheric Sciences; Monsoon circulation; Monsoons; Observations; Ocean-atmosphere interaction; Oceanography; Oceans; Sea level; Sea level pressure; Southern Hemisphere; Summer; Summer monsoon; Temperature (air-sea); Wind; East Asia; Southern Hemisphere; Freshwater hosing experiment; Global warming; East Asian Summer Monsoon; Atlantic meridional overturning circulation; Interannual variability; Southern Hemisphere Circulation
• ISSN: 0930-7575; 1432-0894
• DOI: 10.1007/s00382-018-4121-7

Previous studies show a close relationship between the East Asian Summer Monsoon (EASM) and Southern Hemisphere (SH) circulation on interannual timescales. In this study, we investigate whether this close relationship will change under intensive greenhouse-gas effect by analyzing simulations under two different climate background states: preindustrial era and Representative Concentration Pathway (RCP) 8.5 stabilization from the Community Climate System Model Version 4 (CCSM4). Results show a significantly reduced relationship under stabilized RCP8.5 climate state, such a less correlated EASM with the sea level pressure in the southern Indian Ocean and the SH branch of local Hadley Cell. Further analysis suggests that the collapse of the Atlantic Meridional Overturning Circulation (AMOC) due to this warming leads to a less vigorous northward meridional heat transport, a decreased intertropical temperature contrast in boreal summer, which produces a weaker cross-equatorial Hadley Cell in the monsoonal region and a reduced Interhemispheric Mass Exchange (IME). Since the monsoonal IME acts as a bridge connecting EASM and SH circulation, the reduced IME weakens this connection. By performing freshwater hosing experiment using the Flexible Global Ocean—Atmosphere—Land System model, Grid-point Version 2 (FGOALS-g2), we show a weakened relationship between the EASM and SH circulation as in CCSM4 when AMOC collapses. Our results suggest that a substantially weakened AMOC is the main driver leading to the EASM, which is less affected by SH circulation in the future warmer climate.