Comparison between the Effects of Two Types of El Niño Events on Austral Summer Sea Ice in the Antarctic

Based on the sea ice data from 1979 to 2017, this study used linear regression and a linear baroclinic model to investigate the differences in Antarctic sea ice in Austral summer during two types of El Niño events (Eastern-Pacific, EP and Central-Pacific, CP) and their potential physical mechanisms. The results suggest that the amplitude and spatial pattern of sea ice anomalies differ, despite some similarities. The sea ice anomalies in the Ross Sea and the Amundsen Sea are negative in both EP and CP events, but they are more robust in the EP event than the CP event. The sea ice anomalies in the Weddell Sea are positive, and they are stronger and farther northwestward in the EP event relative to the CP event. The difference in the intensity of sea temperature anomalies between EP and CP events is a major reason for the different amplitude of sea ice. The sea surface temperature anomalies are stronger in the EP event than the CP event, forcing a Pacific–South America teleconnection pattern with a stronger high-pressure anomaly. In the EP event, such atmospheric circulation causes a northeast wind anomaly in the Ross Sea, transporting sea ice to high latitudes and decreasing sea ice. It causes a south wind anomaly in the Weddell Sea, causing sea ice to accumulate on the northern Weddell Sea. Compared to the EP event, the Pacific–South America teleconnection anomaly forced by the CP event is weaker, which induced weaker sea ice anomalies. The positive anomaly of sea ice in the Weddell Sea appeared during the CP event in November and grew stronger due to the ice–albedo feedback in the following spring. Our findings suggest that sea ice anomalies are stronger when the sea surface temperature anomalies in the tropical Pacific are stronger. It differs from previous studies but is more reasonable.