The internal origin of the west-east asymmetry of Antarctic climate change

Abstract

Recent Antarctic surface climate change has been characterised by greater warming trends in West Antarctica than in East Antarctica. Although this asymmetric feature is well recognised, its origin remains poorly understood. Here, by analysing observation data and multi-model results, we show that there exists a west-east asymmetric internal mode amplification in austral winter that originates from the combination of two local factors: the ocean temperature over the Amundsen-Bellingshausen seas and the Antarctic terrain. The warmer ocean temperature over the West Antarctic sector has positive feedback, with an anomalous upper-tropospheric anti-cyclonic circulation response centred over West Antarctica, in which the strength of the feedback is controlled by the Antarctic topographic layout and the annual cycle. The current west-east asymmetry of Antarctic surface climate change is undoubtedly of natural origin