Distinct Impacts of the Central and Eastern Atlantic Niño on West Antarctic Sea Ice

Abstract The sea ice variabilities in West Antarctica, crucial for both local and global climate systems, are profoundly affected by the sea surface temperature anomalies over the tropical Atlantic. Analyses based on observational data and numerical model experiments demonstrate that the two recently identified Atlantic Niño types, central and eastern Atlantic Niño (CAN and EAN), have distinct impacts on the sea ice concentration in West Antarctica. The CAN stimulates two atmospheric Rossby wave trains in the Southern Hemisphere through both direct and indirect pathways, collectively strengthening the Amundsen Sea Low. In contrast, the EAN only excites one atmospheric wave train over the South Pacific through an indirect pathway, due to its associated weaker local Hadley circulation, which fails to establish a significant Rossby wave source in the subtropical South Atlantic. Consequently, compared to the EAN, the atmospheric circulation and the associated sea ice concentration anomalies in West Antarctica during the CAN are stronger and more extensive. Therefore, distinguishing between the two Atlantic Niño types could potentially enhance the seasonal prediction capabilities for sea ice concentration in West Antarctica.