[A-AS06] Stratosphere-troposphere Processes And their Role in Climate

[AAS06-10] The stratospheric QBO affects Antarctic sea ice through the tropical convection in early austral winter

*Koji Yamazaki¹, Tetsu Nakamura¹ (1.Hokkaido University)

Keywords:Antarctic sea ice, stratospheric quasi-biennial oscillation, Rossby wave propagation, tropical convection, Indian Ocean

We found a statistically significant relationship between the stratospheric quasi-biennial oscillation (QBO) and Antarctic sea ice concentration (SIC) in austral winter. SIC differences between the easterly phase of the QBO (EQBO) and westerly phase of the QBO (WQBO) show positive anomalies of SIC in the following regions: over the Ross Sea, Weddell Sea, and around 90°E. This wave-3 pattern is clearly seen in June and July, and decays in August. The increased SIC regions correspond to anomalous offshore wind regions, and the reduced SIC regions correspond to onshore wind regions, indicating the atmospheric circulation anomaly produced the SIC anomaly. The atmospheric circulation anomaly is barotropic and closely related with the upper atmospheric flow. The upper circulation anomaly shows a stationary Rossby wave train propagating from Indian Ocean. We show the enhanced convection in the tropical Indian Ocean in EQBO can excite the Rossby wave train. In summary, the stratospheric QBO affects the tropical convection, then generating the Rossby wave train which propagates into southern high latitude, and finally affecting Antarctic sea ice. There exists a possibility to predict winter sea ice in one-year advance, because the QBO is a quasi-regular oscillation.