The central Pacific as the export region of the El Nino-Southern Oscillation sea surface temperature anomaly to Antarctic sea ice

Abstract

In the mature season of El Nino, Rossby waves do not easily propagate into the polar region, and the seasonal climatology of sea ice is minimal. Austral summer is a barrier to the persistent Antarctic dipole pattern (ADP) in sea ice. The sea surface temperature (SST) anomaly of central Pacific type El Nino (CP-El Nino) in the central Pacific contributes to a strong Rossby wave response and weakening of the polar-front jet that yields strong ADP in austral spring just before the ADP barrier. The strong ADP produces intensive sea-ice-air feedback, which allows the ADP anomaly to breach the barrier. In the conventional El Nino (EP-El Nino) events, the upper-level structure cannot contribute to the strong anomalous high pressure. In EP-El Nino events, the anomalous high in the Bellingshausen Sea is replaced by an anomalous low after the austral autumn following the mature season, whereas the anomalous high pressure persists up to the austral winter in the CP-El Nino. In the CP-El Nino, the ADP persists until austral winter after the mature season of El Nino, whereas, in the EP-El Nino, it does not persist after austral summer. The central Pacific cold SST anomaly of La Nina together with the seasonal SST climatology prolongs the opposite phase of the ADP anomaly up to the austral winter. Consequently, the tropical climate anomaly is exported to extratropics at the central Pacific in the Southern Hemisphere.