Connection between the Tropical Pacific and Indian Ocean and Temperature Anomaly across West Antarctic

Since the 1970s, the West Antarctic and the Antarctic Peninsula have experienced dramatic warming during austral spring. This study investigates the mechanism behind this phenomenon by analyzing observations and utilizing the Community Atmosphere Model version 4 (CAM4). Specifically, it focuses on how the tropical Pacific and Indian Ocean temperature anomaly mode (PIM) influences surface air temperature (SAT) anomalies across the West Antarctic during austral spring. The positive phase of the PIM is characterized by positive sea surface temperature anomalies (SSTAs) in the tropical central-eastern Pacific and western Indian Ocean, along with negative SSTAs in the Maritime Continent. This configuration leads to the generation of two branches of stationary Rossby wave trains originating from the tropical central Pacific and southeastern Indian Ocean. These waves propagate towards the West Antarctic, with an anticyclonic anomaly forming over the Amundsen Sea. The northerly winds transport warmer air to the Ross-Amundsen Seas, while southerly winds bring colder air to the Antarctic Peninsula-Weddell Sea region. This results in a dipole pattern of SAT anomalies over the West Antarctic. The dominance of SSTAs in the tropical central-eastern Pacific, particularly around the Maritime Continent, plays a crucial role in this process. Additionally, SSTAs in the western Indian Ocean, combined with those over the Maritime Continent, further contribute to the western pole of the SAT anomalies. Importantly, simulations incorporating prescribed PIM forcing accurately reproduce the observed dipolar SAT response across the West Antarctic, which highlights the necessity of considering the tropical Pacific and Indian Oceans as a unified system when studying Antarctic climate dynamics.