Remote Arctic Sensitivity to Regional Antarctic Meltwater Forcing: The Key Role of the West Antarctic Sector

Recent observations indicate an acceleration in Antarctic ice sheet mass loss, with the most vigorous melting occurring in West Antarctica. In light of this substantial and asymmetric meltwater forcing, we conduct fully coupled simulations to investigate the climate sensitivity to regional Antarctic meltwater inputs and to assess more realistic climate impacts. Two experiments are performed: one applies a uniform meltwater flux of 0.1 Sv around Antarctica (MV_ANT), and the other applies the same flux only to the Amundsen and Bellingshausen Seas (MV_A/B).

Comparing the two simulations, we find that the Southern Ocean circulations and regionally averaged surface temperature exhibit limited sensitivity to the meltwater source region. This limited regional sensitivity arises because the stronger responses in the Amundsen and Bellingshausen Seas sector are offset by weaker responses in other sectors where no meltwater is applied. In contrast, the Arctic shows a strong sensitivity to the West Antarctic meltwater input. In the MV_A/B experiment, the freshening of Antarctic Intermediate Water in the Atlantic sector reduces its density, which in turn enhances the upper Atlantic Meridional Overturning Circulation (AMOC) - a strengthening that is more pronounced than in the MV_ANT. This enhanced overturning transports warm water northward from south of 60°N, leading to significant Arctic warming and sea ice melt. Meanwhile, the MV_A/B experiment produces a more enhanced meridional temperature gradient in the Southern Hemisphere, which drives shifts in the westerly winds and a decrease in geopotential height, resulting in a positive Southern Annular Mode (SAM)-like response.

These results reveal a pronounced teleconnection from West Antarctica to the Arctic and highlight the West Antarctic sector as a key region governing the influence of Antarctic meltwater on Northern Hemisphere climate.