Potential impacts of enhanced tropical cyclone activity on the El Ni？o–Southern Oscillation and East Asian monsoon in the mid-Piacenzian warm period

ABSTRACT Tropical cyclones (TCs) not only passively respond to climate change, but also play an important role in vertical mixing of the upper ocean and in driving oceanic heat transport. Using a fully coupled climate model, the authors investigate the potential effect of TC-induced vertical mixing on the El Ni？o–Southern Oscillation (ENSO) and East Asian monsoon in the mid-Piacenzian, during which global TCs are estimated to have been stronger. Sensitivity experiments indicate that the TC-induced oceanic mixing over global storm basins leads to additional warming over the eastern tropical Pacific and a deeper thermocline in the mid-Piacenzian, whereas it dampens the interannual variability of ENSO. Regarding the East Asian monsoon circulations, low-level (850 hPa) summer and winter winds are intensified in response to enhanced vertical mixing, with a southward/westward shift of the western North Pacific high and westerly jet in summer and a deepened East Asian trough in winter. These climatic features are largely reproduced in the experiment with enhanced vertical mixing only over the central-eastern North Pacific. These results may shed light on TC feedbacks associated with vertical mixing and advance our understanding on mid-Piacenzian climate. Graphical Abstrac