Influence of Winter Arctic Sea Ice Anomalies on the following Autumn Indian Ocean Dipole Development
Xin Cheng, Shangfeng Chen, Wen Chen, Renguang Wu, Shuoyi Ding, Wen Zhou, Lin Wang, Yali Yang, Jinling Piao, Peng Hu
Abstract
Abstract This study shows a close relationship between winter Arctic sea ice concentration (WASIC) anomalies in the Barents–Greenland Seas and the subsequent autumn Indian Ocean dipole (IOD) based on the observational analysis and numerical simulations. Particularly, more (less) WASIC in the Barents–Greenland Seas tends to lead to a positive (negative) IOD in the following autumn. Above-normal WASIC in the Barents–Greenland Seas results in reduction of the upward turbulent heat flux and induces tropospheric cooling over the Arctic. This tropospheric cooling triggers an atmospheric teleconnection extending from the Eurasian Arctic to the subtropical North Pacific. Numerical experiments with both the linear barotropic model and atmospheric general circulation model can well capture the atmospheric teleconnection associated with the WASIC anomalies. The subtropical atmospheric anomalies generated by the WASIC anomalies then result in subtropical sea surface temperature (SST) warming, which sustains and expands southward to the equatorial central Pacific during the following summer via a wind–evaporation–SST feedback. The resulting equatorial central Pacific SST warming anomalies induce local atmospheric heating and trigger an anomalous Walker circulation with descending motion and low-level anomalous southeasterly winds over the southeastern tropical Indian Ocean. These anomalous southeasterly winds trigger positive air–sea interaction in the tropical Indian Ocean and contribute to the development of the IOD. The close connection of the WASIC anomalies with the subsequent IOD and the underlying physical processes can be reproduced by the coupled climate models participated in the CMIP6. These results indicate that the condition of WASIC is a potential effective precursor of IOD events. Significance Statement The rapid loss of Arctic sea ice has profound implications for global climate change. In recent decades, many studies have investigated the influence of Arctic sea ice anomalies on mid–high latitude climate systems. However, there is less research on the influence of Arctic sea ice variability on the tropical climate systems. In this study, we show a close linkage between the boreal winter Arctic sea ice concentration (WASIC) anomalies in the Barents–Greenland Seas and the subsequent autumn Indian Ocean dipole (IOD), a dominant ocean–atmosphere coupled mode in the tropical Indian Ocean. The occurrence of IOD events can exert substantial impacts on the global climate via teleconnection. Hence, understanding the triggers of IOD events is of great importance, which has crucial implications for the prediction of the IOD. In this study, we reveal that an increase (decrease) in the WASIC in the Barents–Greenland Seas tends to be followed by a positive (negative) IOD event in the following autumn. The underlying physical mechanisms are further investigated based on observational analysis and numerical simulations. The results of this study suggest that the state of the WASIC is an important precursor for the following autumn IOD events. In addition, the finding of this study could improve our understanding of the interaction between climate system over high latitude and low latitude.